[Stoves] Stoves Digest, Vol 88, Issue 11
Norbert Senf
norbert.senf at gmail.com
Sun Dec 10 14:40:25 CST 2017
On Sat, 9 Dec 2017 21:04 Andrew Heggie wrote:
>>>Yes you have mentioned these before but I was referring to what was
known as ciment fondu, a cement that rapidly hardened and was used in
marine applications. (snip)
The castable refractories to which Crispin refers mostly use calcium
aluminate cement as a binder.
There is also a phosphate binder and sodium and calcium silicate, but
fondue (calcium aluminate)
is by far the most common.
It is a "high early" cement and achieves 90% full strength in 24 hrs.
Normally it takes several
hours for initial set. You can use portland cement as an accelerator, and
get a virtually instant
set for certain specialty structural applications, but you would never ever
do this in a refractory
application.
On Sun, Dec 10, 2017 at 2:00 PM, <stoves-request at lists.bioenergylists.org>
wrote:
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> Today's Topics:
>
> 1. Re: Bangladesh TLUD (was Re: No subsidies in TLUD char
> peoduction (Ronal W. Larson)
> 2. Re: Bangladesh TLUD (was Re: No subsidies in TLUD char
> peoduction (Andrew Heggie)
> 3. Re: Fuel cylinder temp experiment needed (was Re: Bangladesh
> TLUD (was Re: No subsidies in TLUD char peoduction (Paul Anderson)
> 4. Re: Bangladesh TLUD (was Re: No subsidies in TLUD char
> peoduction (lh cheng)
> 5. Re: Bangladesh TLUD (was Re: No subsidies in TLUD char
> peoduction (Crispin Pemberton-Pigott)
> 6. Re: Bangladesh TLUD (was Re: No subsidies in TLUD char
> peoduction (Crispin Pemberton-Pigott)
> 7. Re: Bangladesh TLUD (was Re: No subsidies in TLUD char
> peoduction (Crispin Pemberton-Pigott)
> 8. Understanding TLUDs, MPF and more. (was Re: Bangladesh TLUD
> ) (Paul Anderson)
> 9. Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh
> TLUD ) (Crispin Pemberton-Pigott)
> 10. Re: Bangladesh TLUD (was Re: No subsidies in TLUD char
> peoduction (Andrew Heggie)
> 11. Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh
> TLUD ) (Gordon West)
> 12. Re: Going back to 3-Stone Fire [Was Re: China and cookstoves]
> (Nikhil Desai)
> 13. Re: Bangladesh TLUD (was Re: No subsidies in TLUD char
> peoduction (Nikhil Desai)
> 14. Re: Going back to 3-Stone Fire [Was Re: China and cookstoves]
> (Nikhil Desai)
> 15. Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh
> TLUD ) (Crispin Pemberton-Pigott)
> 16. Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh
> TLUD ) (Gordon West)
> 17. Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh
> TLUD ) (Scott Zager)
> 18. Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh
> TLUD ) (Scott Zager)
> 19. Re: Summary of TC285 activities (tmiles at trmiles.com)
> 20. Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh
> TLUD ) (Gordon West)
> 21. Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh
> TLUD ) (Paul Anderson)
> 22. Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh
> TLUD ) (Gordon West)
> 23. Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh
> TLUD ) (Crispin Pemberton-Pigott)
> 24. Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh
> TLUD ) (Crispin Pemberton-Pigott)
> 25. Re: Understanding TLUDs, MPF and more. (was Re: Bangladesh
> TLUD ) (alex english)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 9 Dec 2017 12:19:09 -0700
> From: "Ronal W. Larson" <rongretlarson at comcast.net>
> To: Discussion of biomass <stoves at lists.bioenergylists.org>, Todd Albi
> <todd.r.albi at gmail.com>
> Cc: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
> Subject: Re: [Stoves] Bangladesh TLUD (was Re: No subsidies in TLUD
> char peoduction
> Message-ID: <F2EAC69E-1C26-4F05-8A15-2BFA226D9D1C at comcast.net>
> Content-Type: text/plain; charset="utf-8"
>
> Todd:
>
> Thanks for the comment. I urge readers to visit
> https://www.silverfire.us/ <https://www.silverfire.us/>. Some nice
> looking designs.
>
> I can?t quite accept your message below (and one from Crispin that
> we received 1:23 hours later). You are both using the terms primary and
> secondary in a different (not wrong - just different) sense from those of
> us interested in char-making. We char-makers (or at least the TLUD design
> - Nat Mulcahy and World Stove have a still different meaning to this
> nomenclature) use primary air (meaning oxygen) as something that is totally
> depleted at/near the pyrolysis front. No oxygen in the exiting pyrolysis
> gases, where they are met by secondary air (oxygen).
>
> I am pretty sure you and Crispin (who is also discussing
> char-using stoves) do not mean the above. Rather ?primary? means plenty of
> air (controllable to a minimum degree) to both create and consume char.
> Your and most Rockets (regardless of pre-heating) find char to be a
> defect; you would have preferred to consume it, I believe. (I?d love to
> hear that you welcome the char.) So your ?secondary? is to be sure that
> the ?small? amount of uncombusted gases leaving the fuel bed are
> combusted. I am NOT disputing your phrase below (?Secondary combustion is
> possible with a rocket stove?). I am only saying that secondary air is
> mandatory with TLUDs, and has a totally different function than ?primary?
> air. Most of your primary air consumes char.
>
> The dialog between Paul and myself below on secondary air is
> different than your own explanation below on its preheating.
>
> Do we agree that the terms ?primary? and ?secondary? have very
> different meanings in these two different parts of the stove world?
>
> Ron
>
>
> > On Dec 9, 2017, at 12:32 AM, Todd Albi <todd.r.albi at gmail.com> wrote:
> >
> > Ron:
> >
> > Not quite correct. Secondary combustion is possible with a rocket
> stove. Our Survivor Rocket stove launched 5 years ago introduced preheated
> ventilation ductwork at launch. In fact we only offer a primary &
> secondary combustion design rocket stove. Thats why our stove incorporates
> 360 degree ventilation through base of stove, tied to ventilation ductwork
> behind combustion chamber walls. The double insulated walls allow
> preheated air to travel behind firebox and mix at chimney base, before
> exiting cooktop. Others have also now added preheated channels and
> secondary gasification to rocket stoves. It is not an inclusive to TLUD
> designs and can be adapted to any stove firebox.
> >
> >
> > <Snow Pair Fire.jpg>
> > SilverFire Rocket stove on left & Hunter Chimney TLUD stove on right.
> > ??
> > Todd Albi, SilverFire
> >
> > On Fri, Dec 8, 2017 at 8:52 PM, Ronal W. Larson <
> rongretlarson at comcast.net <mailto:rongretlarson at comcast.net>> wrote:
> > Paul:
> >
> > Yes on your item #1. My first response forgot about preheating
> secondary air - which is why I quickly added this point; heating secondary
> air is a big fuel conservation advantage. Generally not possible with
> rocket stoves - or even charcoal cookers. If not used for heating
> secondary air, that energy would have been just another loss mechanism.
> >
> > Yes also on your #2. I suspected their problem with a concrete
> inner cylinder was related to the secondary holes.
> >
> > But I think (not mentioned earlier) that there may be
> satisfactory ways to use only a single concrete cylinder and still get
> preheating of the secondary air. I?m thinking of some vertical piping or
> tubing - maybe in the concrete. It is not obvious that two cylinders must
> be used. Which is I guess your point.
> >
> > Re #3, if meant for me - I can probably find a way to get coconut
> husks/shells from some local restaurants - but better to ask others than
> myself. I am trying these days to defend biochar against other CDR
> approaches on 3 or 4 other internet lists . So not much time left for
> stoves - or experimenting with char in ground or elsewhere.
> >
> > Tremendous ignorance remains about biochar; the very positive
> Bangladesh soil experience will be very helpful in defending biochar,
> however produced. And, of course, in advancing TLUD technology. I?m
> writing about this elsewhere right now.
> >
> > Ron
> >
> >
> >> On Dec 7, 2017, at 6:51 AM, Paul Anderson <psanders at ilstu.edu <mailto:
> psanders at ilstu.edu>> wrote:
> >>
> >> Ron,
> >>
> >> About the concrete inner (fuel) cylinder. Hard to be sure without
> actually observing it, but I suspect that:
> >> 1. The thermal mass is estracting heat, meaning cooler gases inside
> the chamber, with risk of insufficient temperature for ignition at the top,
> especially when nearing the end of pyrolysis.
> >>
> >> 2. Julien and Mahbubul can confirm about this: The concrete (or
> ceramic) inner cylinder does not have any of the side holes (24 in the
> metal version). Such holes allow for some "pilot light" effect after the
> char level is below a hole. I imagine that small holes would be very
> difficult to put into a concrete cylinder. However, maybe 3 or 6 holes
> could be created at strategic locations (to be discussed). They could be
> created in the following way:
> >> When the concrete is being poured (or soon after), place something
> like round toothpicks (about 2 mm size??) across the concrete, sticking out
> both sides. (might be at a place in the mould with holes that would leak
> concrete/water except that they would soon be "plugged" with the
> toothpicks. When the piece is dried, and used for the first time (or two
> or three times) the wood would burn out (or be drilled out or poked out),
> leaving the desired hole.
> >> Alternatively, do the same with larger diameter pieces like
> chopsticks. If the holes are too large (to be determined by
> experimentation), then they might be plugges slightly (in a variety of
> ways.).
> >>
> >> First, let's get more understanding of the 24 "pilot light" holes in
> the metal version.
> >>
> >> 3. How much supply of coconut shells (hard part) is there in your zone?
> >>
> >> Paul
> >>
> >> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
> >> Email: psanders at ilstu.edu <mailto:psanders at ilstu.edu>
> >> Skype: paultlud Phone: +1-309-452-7072 <tel:(309)%20452-7072>
> >> Website: www.drtlud.com <http://www.drtlud.com/>
> >> On 12/6/2017 11:55 PM, Ronal W. Larson wrote:
> >>> Julien cc List
> >>>
> >>> Thanks for the answers below. Good to hear that both users with
> and without land see value in making char. No new questions, two comments
> >>>
> >>> 1. Re a concrete inner cylinder, you said below ?..but their
> smoke-free combustion was less reliable, and there were some gas burner
> issues to solve. ?
> >>> It is not obvious to me why either concern should occur, so I hope
> stovers everywhere could try this out. Seems likely to be cheaper (can
> even maybe cast in place) and hopefully longer lived. We know usual cheap
> steel has a limited life and the best steels are likely both not readily
> available and expensive.
> >>> I forgot to congratulate on the two metal swinging ?doors? at the
> bottom. Nice solution.
> >>>
> >>> 2. Re fuels, the biochar list has had quite a lot of recent
> discussion of ?blue biochar? - where the source material is kelp or other
> seaweeds. Bangladesh is possibly already in that business, because of its
> ocean proximity. This could be a source of employment and a way to save
> forests while having a feedstock that should bring back needed minerals and
> fertilizer value. Beating the price of wooden blocks seems possible.
> >>>
> >>> Ron
>
> <snipped message from Julien not on this topic - to save badwidth>
>
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> ------------------------------
>
> Message: 2
> Date: Sat, 9 Dec 2017 21:04:54 +0000
> From: Andrew Heggie <aj.heggie at gmail.com>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Bangladesh TLUD (was Re: No subsidies in TLUD
> char peoduction
> Message-ID:
> <CAPSaZeasU+HXvBEOUESXELGRshiLpaQanr=bRLWF
> _SbYiRWajQ at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> On 9 December 2017 at 15:45, Crispin Pemberton-Pigott
> <crispinpigott at outlook.com> wrote:
>
> > High alumina materials (above 60% Al2O3) are available in at least three
> formulations, all castable refractory materials. High alumina castable
> materials can take 1300 C if the normal bottom of the mine one is used.
> They are available for much higher Temps. Thermal conductivity is about
> 1.5. Some, fired to 1300 can take 1700 C thereafter.
>
>
> Yes you have mentioned these before but I was referring to what was
> known as ciment fondu, a cement that rapidly hardened and was used in
> marine applications. There was a civil engineering department that
> held a competition for the students in UK where a mould was made in
> the sand and a chicken wire mesh laid over it, this formed the steel
> reinforcement for a slip-formed concrete which was laid over the mesh,
> it hardened in minutes but then the tide came in and it set overnight.
> The students then recovered the shells and rowed them in a race around
> the bay.
>
> It got a very bad name when it was found to recrystallise over time
> and develop faults when uses in high rise buildings but I still used
> it for setting concrete fence posts as it sets so fast.
>
> It is calcium aluminates rather than calcium silicate in portland
> cement. I used it, with vermiculite aggregate,in one of my larger
> vortex burners in the conical roof but it soon failed as temperatures
> reached 1200C but it should cope better than portland cement at these
> lower temperatures we are talking about.
>
> Andrew
>
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 9 Dec 2017 15:07:39 -0600
> From: Paul Anderson <psanders at ilstu.edu>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Fuel cylinder temp experiment needed (was Re:
> Bangladesh TLUD (was Re: No subsidies in TLUD char peoduction
> Message-ID: <406e70a6-f179-e7f3-a447-fcd47e9fe19c at ilstu.edu>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> Stovers
>
> Numerous excellent reports by Dr. Julien Winter about TLUD stove can be
> found at the website:?? http://www.drtlud.com/?s=winter??? or easier to
> remember, go to the website and in the search box at the bottom of the
> Home page, type in ? ? ? winter? .
>
> Thank you, Julien, for your many contributions!!
>
> Paul
>
> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
> Email: psanders at ilstu.edu
> Skype: paultlud Phone: +1-309-452-7072
> Website: www.drtlud.com
>
> On 12/9/2017 10:13 AM, Julien Winter wrote:
> > Hi All;
> >
> > About three years ago, I ran a number of replicated experiments to
> > measure the temperature inside TLUD reactors. ?Some of it is
> > summarized here:
> >
> > http://www.biochar-bangladesh.org/wp-content/uploads/2015/
> 11/TLUD_BasicParameters.pdf
> >
> > http://www.ethoscon.com/wp-content/uploads/2015/04/
> Gasification-Temperatures-in-Natural-Draft-Top-Lit-Updraft-Gasifiers.pdf
> >
> > Cheers,
> > Julien
> >
> >
> > --
> > Julien Winter
> > Cobourg, ON, CANADA
> >
> >
> > _______________________________________________
> > Stoves mailing list
> >
> > to Send a Message to the list, use the email address
> > stoves at lists.bioenergylists.org
> >
> > to UNSUBSCRIBE or Change your List Settings use the web page
> > http://lists.bioenergylists.org/mailman/listinfo/stoves_
> lists.bioenergylists.org
> >
> > for more Biomass Cooking Stoves, News and Information see our web site:
> > http://stoves.bioenergylists.org/
> >
>
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> ------------------------------
>
> Message: 4
> Date: Sun, 10 Dec 2017 10:46:08 +0800
> From: lh cheng <lhkind at gmail.com>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Bangladesh TLUD (was Re: No subsidies in TLUD
> char peoduction
> Message-ID:
> <CAK2R_NeVFJHvJBNywNRQvKyOdn0SHjk4OsV+c1sC9=
> 6bfDeC4g at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Yes, you are right, Mr Albi, my present rocket stove have preheated
> secondary air supply, and third air. the secondary air holes is much less
> needed comparing TLUD stove, since much of it comes from under and through
> the red hot charcoal, ( so, ordinary rocket stove naturally have some very
> hot "secondary air" already). it burns everything into red/blue flame and
> white fine ashes, totally smokeless.
>
> 2017-12-09 15:32 GMT+08:00 Todd Albi <todd.r.albi at gmail.com>:
>
> > Ron:
> >
> > Not quite correct. Secondary combustion* is possible* with a rocket
> > stove. Our Survivor Rocket stove launched 5 years ago introduced
> preheated
> > ventilation ductwork at launch. In fact we only offer a primary &
> > secondary combustion design rocket stove. Thats why our stove
> incorporates
> > 360 degree ventilation through base of stove, tied to ventilation
> ductwork
> > behind combustion chamber walls. The double insulated walls allow
> > preheated air to travel behind firebox and mix at chimney base, before
> > exiting cooktop. Others have also now added preheated channels and
> > secondary gasification to rocket stoves. It is not an inclusive to TLUD
> > designs and can be adapted to any stove firebox.
> >
> >
> >
> > SilverFire Rocket stove on left & Hunter Chimney TLUD stove on right.
> > ??
> > Todd Albi, SilverFire
> >
> > On Fri, Dec 8, 2017 at 8:52 PM, Ronal W. Larson <
> rongretlarson at comcast.net
> > > wrote:
> >
> >> Paul:
> >>
> >> Yes on your item #1. My first response forgot about preheating
> secondary
> >> air - which is why I quickly added this point; heating secondary air
> is a
> >> big fuel conservation advantage. Generally not possible with rocket
> stoves
> >> - or even charcoal cookers. If not used for heating secondary air, that
> >> energy would have been just another loss mechanism.
> >>
> >> Yes also on your #2. I suspected their problem with a concrete inner
> >> cylinder was related to the secondary holes.
> >>
> >> But I think (not mentioned earlier) that there may be satisfactory ways
> >> to use only a single concrete cylinder and still get preheating of the
> >> secondary air. I?m thinking of some vertical piping or tubing - maybe in
> >> the concrete. It is not obvious that two cylinders must be used.
> Which is
> >> I guess your point.
> >>
> >> Re #3, if meant for me - I can probably find a way to get coconut
> >> husks/shells from some local restaurants - but better to ask others than
> >> myself. I am trying these days to defend biochar against other CDR
> >> approaches on 3 or 4 other internet lists . So not much time left for
> >> stoves - or experimenting with char in ground or elsewhere.
> >> Tremendous ignorance remains about biochar; the very positive
> Bangladesh
> >> soil experience will be very helpful in defending biochar, however
> >> produced. And, of course, in advancing TLUD technology. I?m writing
> about
> >> this elsewhere right now.
> >>
> >> Ron
> >>
> >>
> >> On Dec 7, 2017, at 6:51 AM, Paul Anderson <psanders at ilstu.edu> wrote:
> >>
> >> Ron,
> >>
> >> About the concrete inner (fuel) cylinder. Hard to be sure without
> >> actually observing it, but I suspect that:
> >> 1. The thermal mass is estracting heat, meaning cooler gases inside the
> >> chamber, with risk of insufficient temperature for ignition at the top,
> >> especially when nearing the end of pyrolysis.
> >>
> >> 2. Julien and Mahbubul can confirm about this: The concrete (or
> >> ceramic) inner cylinder does not have any of the side holes (24 in the
> >> metal version). Such holes allow for some "pilot light" effect after
> the
> >> char level is below a hole. I imagine that small holes would be very
> >> difficult to put into a concrete cylinder. However, maybe 3 or 6 holes
> >> could be created at strategic locations (to be discussed). They could
> be
> >> created in the following way:
> >> When the concrete is being poured (or soon after), place something
> >> like round toothpicks (about 2 mm size??) across the concrete, sticking
> out
> >> both sides. (might be at a place in the mould with holes that would
> leak
> >> concrete/water except that they would soon be "plugged" with the
> >> toothpicks. When the piece is dried, and used for the first time (or
> two
> >> or three times) the wood would burn out (or be drilled out or poked
> out),
> >> leaving the desired hole.
> >> Alternatively, do the same with larger diameter pieces like
> >> chopsticks. If the holes are too large (to be determined by
> >> experimentation), then they might be plugges slightly (in a variety of
> >> ways.).
> >>
> >> First, let's get more understanding of the 24 "pilot light" holes in the
> >> metal version.
> >>
> >> 3. How much supply of coconut shells (hard part) is there in your zone?
> >>
> >> Paul
> >>
> >> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
> >> Email: psanders at ilstu.edu
> >> Skype: paultlud Phone: +1-309-452-7072 <(309)%20452-7072>
> >> Website: www.drtlud.com
> >>
> >> On 12/6/2017 11:55 PM, Ronal W. Larson wrote:
> >>
> >> Julien cc List
> >>
> >> Thanks for the answers below. Good to hear that both users with and
> >> without land see value in making char. No new questions, two comments
> >>
> >> 1. Re a concrete inner cylinder, you said below ?..*but their
> >> smoke-free combustion was less reliable, and there were some gas burner
> >> issues to solve. ?*
> >> It is not obvious to me why either concern should occur, so I hope
> >> stovers everywhere could try this out. Seems likely to be cheaper (can
> >> even maybe cast in place) and hopefully longer lived. We know usual
> cheap
> >> steel has a limited life and the best steels are likely both not readily
> >> available and expensive.
> >> I forgot to congratulate on the two metal swinging ?doors? at the
> >> bottom. Nice solution.
> >>
> >> 2. Re fuels, the biochar list has had quite a lot of recent discussion
> >> of ?blue biochar? - where the source material is kelp or other seaweeds.
> >> Bangladesh is possibly already in that business, because of its ocean
> >> proximity. This could be a source of employment and a way to save
> forests
> >> while having a feedstock that should bring back needed minerals and
> >> fertilizer value. Beating the price of wooden blocks seems possible.
> >>
> >> Ron
> >>
> >> On Dec 6, 2017, at 10:05 PM, Julien Winter <winter.julien at gmail.com>
> >> wrote:
> >>
> >> Hello all;
> >>
> >> Thanks for you comments on the Akha-Biochar Project in Bangladesh.
> >>
> >> The cost and payback is not fully worked out, because it will take about
> >> a year for TLUD-biochar ecosystem to become established in community,
> and
> >> it will continue to evolve. The stove costs about $20 to make, this
> could
> >> be brought down as numbers of stoves increase. Also, we are still at
> the
> >> stove-prototype stage, so we can expect some modifications and fine
> >> tuning. Payback is developing, as farmers and gardeners discover the
> >> value of biochar for food production. We have "Farmer Biochar User
> Groups"
> >> that are conducting field trials, so they can learn from first-hand
> >> experience what biochar can do for them. There are also graduate
> students
> >> involved in gathering evidence to make recommendations on optimum
> >> application rates. It could take a couple of years at any one location
> for
> >> the local population to be able to place their own value on biochar, and
> >> what they are willing to pay for it.
> >>
> >> Whether people use the char themselves or sell it depends on their
> >> personal opportunities. There are many families that are landless.
> >> Presently, they see char sales as a way to earn cash or barter. They
> think
> >> that is a great idea; save fuel, cook faster, AND make biochar! People
> >> with land, especially farmers, see biochar as a way of making permanent
> >> improvements to the quality of their land, so expect that using biochar
> >> could have very substantial impact on their family's economic well
> being.
> >>
> >> I have been advocating using biochar in composting, or mixing it with
> >> manure before it goes onto the field. We need work on using it in human
> >> waste management.
> >>
> >> There is no shortage of good soil scientists and agronomists in
> >> Bangladesh to work on biochar technology.
> >>
> >> The outer concrete cylinder of the Akha stove is cast. We have made
> >> stoves with concrete reactors (lined with clay slip), but their
> smoke-free
> >> combustion was less reliable, and there were some gas burner issues to
> >> solve. That is not to say that concrete reactors will not work, but
> they
> >> need quite a bit of research and development, and a laboratory. Metal
> TLUD
> >> reactors, on the other hand, are well understood. About 24 small holes
> in
> >> the side wall of the metal reactor make the gasification of chunks of
> wood
> >> more reliable, and less prone loosing the gas flame. We use cast
> concrete
> >> (rather than clay) because it is easy to get concrete rings with flat
> >> surfaces at the top and bottom. The concrete components are made
> >> specifically for the Akha. There are many small business around who can
> >> cast concrete.
> >>
> >> Mahbubul has been working with different ratios of Portand cement,
> >> sawdust and biochar dust in the concrete. The more organics, the lower
> the
> >> heat capacity and heat conductivity of the stove body. Micro porosity is
> >> supposed to make concrete more resistant heat by providing spaces for
> >> minerals to expand into. Obviously there is a trade-off between adding
> >> organics and strength of the concrete. Different recipes are being
> tested
> >> in the field. It is all trial and error.
> >>
> >> Mahbubul has also worked with local ceramic artisans to make the massive
> >> stove components from clay. There very skilled people to work with, and
> >> kaolinitic clay, so ceramic components are possible. The more metal
> >> components on the stove that we can replace with ceramics the better,
> >> because all metal in Bangladesh is imported.
> >>
> >> The Akha is about 25% more efficient than a traditional stove. The Akha
> >> has gone through a water-boiling test at a laboratory in Dhaka, and was
> >> about 30% efficient at getting energy from wood into the water. The
> main
> >> view that the Akha saves 25% of the wood comes from household feedback.
> >> That is what the women tell us.
> >>
> >> The Akha-Biocahr Project has funding for its current intervention until
> >> 2019. It is enough to see if the TLUD-biochar technology will take root.
> >> If it does, then the technology may spread all by itself as local
> >> entrepreneurs see an opportunity. In fact, I think that if these
> >> technologies viable, then they will out of our control and unstoppable.
> >> The 'market' is 25 million homes. All the same, I am trying to raise
> money
> >> so that Mahbubul and crew remain as proponents and stakeholders in what
> >> they started. There is work to be done in developing compressed fuels,
> >> because there is not enough wood in the country. We need to monitor the
> >> impact on forest cover, and make sure that poorest households don't
> become
> >> energy-starved if the price of wood goes up.
> >>
> >> One other thing that will push TLUD-biochar technology forward is that
> >> sea-level rise could flood a third of the country, so soil productivity
> >> needs to increase.
> >>
> >> Cheers,
> >> Julien.
> >>
> >> --
> >> Julien Winter
> >> Cobourg, ON, CANADA
> >> _______________________________________________
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> ------------------------------
>
> Message: 5
> Date: Sun, 10 Dec 2017 03:03:21 +0000
> From: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
> To: Stoves <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Bangladesh TLUD (was Re: No subsidies in TLUD
> char peoduction
> Message-ID:
> <MWHPR22MB0784AF161D2089DEBF3E3D99B1360 at MWHPR22MB0784.
> namprd22.prod.outlook.com>
>
> Content-Type: text/plain; charset="utf-8"
>
> Dear Ron
>
> I see no systematic differences between the uses of the terms. You are
> trying to create some special meaning for quite ordinary processes of
> combustion.
>
> It is unfortunate you mix baseless assertions, projections of motive onto
> others and micro-aggressions ?into your erroneous analyses and combustion
> theory. It is wearying trying to separate your mistakes from your agendas.
>
> For the rest of our readers, these definitions may be useful:
>
> Primary air refers to that atmospheric oxygen used to convert a
> combustible fuel into a gaseous state through thermal decomposition. It is
> needed to combust gaseous fuels if the gas is not composed of molecules
> that can be oxidised directly (evaporated kerosene, for example).
>
> Secondary air is that atmospheric oxygen which is used to combust those
> ?gases at some location generally distinct from the solid fuel.
>
> Tertiary air is that atmospheric oxygen separately added to the gas
> combustion phase in order to complete the combustion and or to moderate the
> gas temperature? to fall within some desired range (for example a low-NOx
> burner or a fish dryer).
>
> While a TLUD's migrating pyrolytic front (MPF) can produce char from
> biomass, there are other methods of doing so. Two that have a higher
> theoretical char yield ?are the charcoal kilns designed by Chris Adams (the
> Adam Retort) and the World Stove. Their working principles are not the same
> as the TLUD. Both produce a combustible gas that is applied to a process
> outside the charring of biomass.
>
> In the char producing ?section of the Adam Retort there is no primary air
> supplied at all but it still has an MPF proceeding in a roughly horizontal
> direction. The World Stove supplies some primary air in the beginning but
> only secondary air later. Still later, primary air is again supplied if the
> operator wishes to burn the char produced.
>
> All three of these approaches have proven effective. Of the three, the
> Adam Retort has the highest char production fraction per kg of input
> material, the widest range of usable materials and the least possible
> preparation required. The seven drum kiln designed by Dr AD Karve operates
> on the same principles and is specialised to char leaves. A small
> percentage of the fuel ends up in the ground as biochar.
>
> A higher fraction of the char ends up in the ground? when it is produced
> using the earth pit charcoal production process. I have not seen this
> discussed on the Stoves list. An investigation by Cecil Cook in Mozambique
> into the ultimate destination of char conducted while working for
> ProBEC/GTZ showed that a considerable fraction of char produced ended up
> under the pot and the rest ended up on or in the ground, which you have
> termed variously as 'sequestration' and some form of fertilization.
>
> ?There is nothing magical or new about an MPF and it does not need a
> special vocabulary to describe it. In Southern California the devastating
> forest fires are leaving behind millions of smouldering tree stumps each of
> which has an MPF moving along its stump and major underground roots. This
> process is as old as fire. It is how the Terra Preta soils in the Amazon
> were created over 20,000 years of slash and burn agriculture. The
> Amerindians cultivated land that was already productive, they did not
> create it de novo. Cecil confirms they farm patches of land that are
> already productive, not random areas. He observed this when he was doing
> PhD field research while at Harvard.
>
> I hope others can get contribute to especially the technical aspects of
> the discussion. I will close with a reminder that the highest char
> production fraction I have encountered (45%) is the Hawaiian pressurised
> kiln which uses a controlled primary air supply and an MPF to char a five
> foot long log one foot in diameter in 45 minutes. "45 in 45".
>
> ?Amazing.
>
> Regards
> Crispin
> ?
> Todd:
>
> Thanks for the comment. I urge readers to visit
> https://www.silverfire.us/<https://eur03.safelinks.
> protection.outlook.com/?url=https%3A%2F%2Fwww.silverfire.
> us%2F&data=02%7C01%7C%7C2f4e87e571974e97b4cf08d53f3a03ae%
> 7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636484440759723211&sdata=
> 2uvPfW50fAZhf81ZYqCzad40wiN2th9I1xzu7%2BCy7wM%3D&reserved=0>. Some nice
> looking designs.
>
> I can?t quite accept your message below (and one from Crispin that we
> received 1:23 hours later). You are both using the terms primary and
> secondary in a different (not wrong - just different) sense from those of
> us interested in char-making. We char-makers (or at least the TLUD design
> - Nat Mulcahy and World Stove have a still different meaning to this
> nomenclature) use primary air (meaning oxygen) as something that is totally
> depleted at/near the pyrolysis front. No oxygen in the exiting pyrolysis
> gases, where they are met by secondary air (oxygen).
>
> I am pretty sure you and Crispin (who is also discussing char-using
> stoves) do not mean the above. Rather ?primary? means plenty of air
> (controllable to a minimum degree) to both create and consume char. Your
> and most Rockets (regardless of pre-heating) find char to be a defect; you
> would have preferred to consume it, I believe. (I?d love to hear that you
> welcome the char.) So your ?secondary? is to be sure that the ?small?
> amount of uncombusted gases leaving the fuel bed are combusted. I am NOT
> disputing your phrase below (?Secondary combustion is possible with a
> rocket stove?). I am only saying that secondary air is mandatory with
> TLUDs, and has a totally different function than ?primary? air. Most of
> your primary air consumes char.
>
> The dialog between Paul and myself below on secondary air is different
> than your own explanation below on its preheating.
>
> Do we agree that the terms ?primary? and ?secondary? have very different
> meanings in these two different parts of the stove world?
>
> Ron
>
>
> On Dec 9, 2017, at 12:32 AM, Todd Albi <todd.r.albi at gmail.com<mailto:
> todd.r.albi at gmail.com>> wrote:
>
> Ron:
>
> Not quite correct. Secondary combustion is possible with a rocket stove.
> Our Survivor Rocket stove launched 5 years ago introduced preheated
> ventilation ductwork at launch. In fact we only offer a primary &
> secondary combustion design rocket stove. Thats why our stove incorporates
> 360 degree ventilation through base of stove, tied to ventilation ductwork
> behind combustion chamber walls. The double insulated walls allow
> preheated air to travel behind firebox and mix at chimney base, before
> exiting cooktop. Others have also now added preheated channels and
> secondary gasification to rocket stoves. It is not an inclusive to TLUD
> designs and can be adapted to any stove firebox.
>
>
> <Snow Pair Fire.jpg>
> SilverFire Rocket stove on left & Hunter Chimney TLUD stove on right.
> ??
> Todd Albi, SilverFire
>
> On Fri, Dec 8, 2017 at 8:52 PM, Ronal W. Larson <rongretlarson at comcast.net
> <mailto:rongretlarson at comcast.net>> wrote:
> Paul:
>
> Yes on your item #1. My first response forgot about preheating secondary
> air - which is why I quickly added this point; heating secondary air is a
> big fuel conservation advantage. Generally not possible with rocket stoves
> - or even charcoal cookers. If not used for heating secondary air, that
> energy would have been just another loss mechanism.
>
> Yes also on your #2. I suspected their problem with a concrete inner
> cylinder was related to the secondary holes.
>
> But I think (not mentioned earlier) that there may be satisfactory ways to
> use only a single concrete cylinder and still get preheating of the
> secondary air. I?m thinking of some vertical piping or tubing - maybe in
> the concrete. It is not obvious that two cylinders must be used. Which is
> I guess your point.
>
> Re #3, if meant for me - I can probably find a way to get coconut
> husks/shells from some local restaurants - but better to ask others than
> myself. I am trying these days to defend biochar against other CDR
> approaches on 3 or 4 other internet lists . So not much time left for
> stoves - or experimenting with char in ground or elsewhere.
> Tremendous ignorance remains about biochar; the very positive Bangladesh
> soil experience will be very helpful in defending biochar, however
> produced. And, of course, in advancing TLUD technology. I?m writing about
> this elsewhere right now.
>
> Ron
>
>
> On Dec 7, 2017, at 6:51 AM, Paul Anderson <psanders at ilstu.edu<mailto:psa
> nders at ilstu.edu>> wrote:
>
> Ron,
>
> About the concrete inner (fuel) cylinder. Hard to be sure without
> actually observing it, but I suspect that:
> 1. The thermal mass is estracting heat, meaning cooler gases inside the
> chamber, with risk of insufficient temperature for ignition at the top,
> especially when nearing the end of pyrolysis.
>
> 2. Julien and Mahbubul can confirm about this: The concrete (or ceramic)
> inner cylinder does not have any of the side holes (24 in the metal
> version). Such holes allow for some "pilot light" effect after the char
> level is below a hole. I imagine that small holes would be very
> difficult to put into a concrete cylinder. However, maybe 3 or 6 holes
> could be created at strategic locations (to be discussed). They could be
> created in the following way:
> When the concrete is being poured (or soon after), place something
> like round toothpicks (about 2 mm size??) across the concrete, sticking out
> both sides. (might be at a place in the mould with holes that would leak
> concrete/water except that they would soon be "plugged" with the
> toothpicks. When the piece is dried, and used for the first time (or two
> or three times) the wood would burn out (or be drilled out or poked out),
> leaving the desired hole.
> Alternatively, do the same with larger diameter pieces like
> chopsticks. If the holes are too large (to be determined by
> experimentation), then they might be plugges slightly (in a variety of
> ways.).
>
> First, let's get more understanding of the 24 "pilot light" holes in the
> metal version.
>
> 3. How much supply of coconut shells (hard part) is there in your zone?
>
> Paul
>
>
> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
> Email: psanders at ilstu.edu<mailto:psanders at ilstu.edu>
> Skype: paultlud Phone: +1-309-452-7072<tel:(309)%20452-7072>
> Website: www.drtlud.com<https://eur03.safelinks.protection.outlook.
> com/?url=http%3A%2F%2Fwww.drtlud.com%2F&data=02%7C01%7C%
> 7C2f4e87e571974e97b4cf08d53f3a03ae%7C84df9e7fe9f640afb435aaaaaaaa
> aaaa%7C1%7C0%7C636484440759723211&sdata=%2F0G0WITanc4Qcg1Y7PLykyHh5m8pq
> wgSmbrNqKAMRT4%3D&reserved=0>
>
> On 12/6/2017 11:55 PM, Ronal W. Larson wrote:
> Julien cc List
>
> Thanks for the answers below. Good to hear that both users with and
> without land see value in making char. No new questions, two comments
>
> 1. Re a concrete inner cylinder, you said below ?..but their smoke-free
> combustion was less reliable, and there were some gas burner issues to
> solve. ?
> It is not obvious to me why either concern should occur, so I hope
> stovers everywhere could try this out. Seems likely to be cheaper (can
> even maybe cast in place) and hopefully longer lived. We know usual cheap
> steel has a limited life and the best steels are likely both not readily
> available and expensive.
> I forgot to congratulate on the two metal swinging ?doors? at the bottom.
> Nice solution.
>
> 2. Re fuels, the biochar list has had quite a lot of recent discussion of
> ?blue biochar? - where the source material is kelp or other seaweeds.
> Bangladesh is possibly already in that business, because of its ocean
> proximity. This could be a source of employment and a way to save forests
> while having a feedstock that should bring back needed minerals and
> fertilizer value. Beating the price of wooden blocks seems possible.
>
> Ron
>
> <snipped message from Julien not on this topic - to save badwidth>
>
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> ------------------------------
>
> Message: 6
> Date: Sun, 10 Dec 2017 03:06:39 +0000
> From: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
> To: Stoves <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Bangladesh TLUD (was Re: No subsidies in TLUD
> char peoduction
> Message-ID:
> <MWHPR22MB0784868E202FC5BE46EAF7B9B1360 at MWHPR22MB0784.
> namprd22.prod.outlook.com>
>
> Content-Type: text/plain; charset="us-ascii"
>
> What a great insight. What s the material called in the shelf?
>
> Thanks
> Crispin
>
>
>
> On 9 December 2017 at 15:45, Crispin Pemberton-Pigott
> <crispinpigott at outlook.com> wrote:
>
> > High alumina materials (above 60% Al2O3) are available in at least three
> formulations, all castable refractory materials. High alumina castable
> materials can take 1300 C if the normal bottom of the mine one is used.
> They are available for much higher Temps. Thermal conductivity is about
> 1.5. Some, fired to 1300 can take 1700 C thereafter.
>
>
> Yes you have mentioned these before but I was referring to what was
> known as ciment fondu, a cement that rapidly hardened and was used in
> marine applications. There was a civil engineering department that
> held a competition for the students in UK where a mould was made in
> the sand and a chicken wire mesh laid over it, this formed the steel
> reinforcement for a slip-formed concrete which was laid over the mesh,
> it hardened in minutes but then the tide came in and it set overnight.
> The students then recovered the shells and rowed them in a race around
> the bay.
>
> It got a very bad name when it was found to recrystallise over time
> and develop faults when uses in high rise buildings but I still used
> it for setting concrete fence posts as it sets so fast.
>
> It is calcium aluminates rather than calcium silicate in portland
> cement. I used it, with vermiculite aggregate,in one of my larger
> vortex burners in the conical roof but it soon failed as temperatures
> reached 1200C but it should cope better than portland cement at these
> lower temperatures we are talking about.
>
> Andrew
>
> _______________________________________________
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>
>
>
>
> ------------------------------
>
> Message: 7
> Date: Sun, 10 Dec 2017 04:42:32 +0000
> From: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
> To: "'Stoves (stoves at lists.bioenergylists.org)'"
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Bangladesh TLUD (was Re: No subsidies in TLUD
> char peoduction
> Message-ID:
> <MWHPR22MB07849B9E7F1E56A7A4F1C0C6B1360 at MWHPR22MB0784.
> namprd22.prod.outlook.com>
>
> Content-Type: text/plain; charset="utf-8"
>
> Dear Nikhil
>
> I recall he used the WBT of the day, probably WBT 3.1. I recall the values
> for the light insulative ceramic chamber was 22% and the heavy heat
> conductive chamber was 24% and he got a repeatedly higher value for the
> heavy conductive chamber.
>
> I have concluded the reason for this enhanced performance is to be noted
> late in the fire when the heat stored in the combustion chamber is returned
> to the fire as it wanes. It keeps the CO burning for longer late in the
> fire providing heat otherwise lost (chemical loss).
>
> An insulative chamber provides a hotter chamber sooner but this advantage
> is soon lose when heat migrates into the stove body and cannot return later
> at a rate sufficient to keep the chamber wall hot.
>
> >What he discovered is similar to common knowledge from my childhood - in
> samovars for heating bathwater. Designs with thicker copper retained heat
> better and fuel efficiency was higher; which mattered because in the city
> we used purchased charcoal.
>
> So where fuel is purchased there is a direct consequence for higher or
> lower fuel efficiency.
>
> >If you standardize the cooking experience and cooking behavior, I suppose
> you can adjust for the amount of heat that goes in the stove body but is
> not utilized for cooking experience.
>
> Ah, wait a minute. You have moved from assessing the performance of a
> defined system to assessing one aspect of its internal sub-systems revealed
> in:
>
> >And if you were to do that, you would come up with some computation of
> efficiency. Which I call "competing on fuel efficiency percentages is
> infantile business" because standardizing cooking behavior and cooking
> experience is infantilism.
>
> This completes the switcheroo. You have picked on the standardisation of a
> ?behaviour? (which I call a ?burn sequence?) and criticized the metric used
> to rate the performance of the whole system in use, but your family.
>
> >That has nothing to do with whether fuel efficiency matters or dominates
> consumer choice.
>
> That is a question outside the cooking system, residing entirely between
> the ears of the user. To optimise the performance on any metric of choice
> of feature, one often standardises the task to isolate the how one factor
> contributes to the overall performance.
>
> Standardising everything, as in a WBT performed by Aprovecho using their
> ?standard fuel? is a way to compare labs, and is used by the ISO in their
> determination of a lab?s ability to replicate results. To get ISO 17025
> certification, a lab has to replicate the results of another lab (save in
> one special case).
>
> >Testing and metrics ought to have a purpose.
>
> They do, and they have two broad categories of purpose: the determination
> of the performance on a sub-system metric, and their performance as a
> system. There is no point in reporting the performance of a system on the
> basis of how one of its sub-systems rates. Such sub-categories of
> performance may be interesting, such as the kW of heat generated per cubic
> foot of combustion chamber. That is a metric in the current National
> Standard of Mongolia for low pressure boilers. It is not a system
> performance metric, but it is required for reporting purposes. IT is an
> example of the design engineer?s interests leaking through to the final
> product. The fuel consumption, fuel flexibility, emissions, whatever might
> be a systems rating, is not improved by requiring such a metric, even
> though the engineers determine and track such arcane things.
>
> Fuel consumption is such a primary aspect of system performance it is
> worth including it even when the fuel in some communities is unlimited and
> freely available. This does not apply in most communities, or any community
> where effort is considered a cost.
>
> Regards
> Crispin in the snow today
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> ------------------------------
>
> Message: 8
> Date: Sat, 9 Dec 2017 23:00:23 -0600
> From: Paul Anderson <psanders at ilstu.edu>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID: <3c488495-225c-997d-261e-b74ec0d0495a at ilstu.edu>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> Crispin,??????? (Friends are not required to agree.)
>
> Some of what you wrote is correct, but you go too far or leave out some
> important distinctions, thereby implying that some things are equal,
> that is, some are not really as worthy and distinctive as others (Ron
> and Paul) have stated.? I give you four cases:
>
> 1.? Pyrolysis progresses (migrates) through a piece or pile of biomass
> as heat is able to penetrate.? True.?? The Adam retort (and other
> retorts) heat the biomass from many sides, but there is no flame (actual
> combustion) inside.? It is a stretch of language to say that the
> pyrolysis in the retort
> > has an MPF [migrating pyrolytic front] proceeding in a roughly
> > horizontal direction.
> Sorry, that should say "has external heating proceeding inward from
> several directions from the sides toward the center." ? It is no more of
> a "front" than having the heat in a home reach to the center of the
> house from all of the furnace duct registers in each room. Furthermore,
> the processes in a retort are in sequential order during numerous
> minutes to 1) heat virtually all of the biomass to drive off the
> moisture, then 2) add more heat to virtually all of the biomass to drive
> off the low-temperature volatiles to create torrified material, and than
> 3) to finally get the temperature hot enough to have actual pryrolysis,
> first in the 400 deg C range and then at higher temperatures if the
> external heating is continued.
>
> In sharp contrast, in a TLUD there is a distinctive zone of a few cm
> depth with actual small amounts of combustion (of some of the initial
> offgases).? That zone migrates through the pile of biomass, heating
> mainly by radiation a small layer of biomass below the MPF, then with?
> pyrolysis at a rather uniform temperature (generally from 450 to 700 C,
> depending on USER CONTROLED flow of primary air) to create the char as
> the gases move upward.
>
> You may choose to try to equate the two descriptions above, but that
> would diminish your credibility as a precision-seeking scientist. And to
> equate a smouldering tree stump to MPF is a stretch beyond a stretch.?
> Yes, there is fire there, and yes there is pyrolysis occuring.?? But
> such comparison is akin to saying that a ladybug and a moose are the
> same because both are living creatures; and in fact both are animals.??
> Even a petunia and a whale are both living organisms.? Scientific
> comparisons need precision and detail.
>
> 2.? Ron correctly pointed out that in normal operation of TLUD stoves,
> there is zero O2 that gets past the MPF.? That is vastly different from
> having so much primary air enter (as in Rocket stoves and other burners)
> that there is O2 moving upward above the fuel (where the? gases were
> created).? You are saying that is good as preheated secondary O2.?
> Maybe, but not really.? It is simply inadequate combustion, with the
> results of undesirable emissions. The excessive primary air (which you
> state should be secondary air) has had a cooling effect on the raw fuel
> that the combustion is trying to get hot enough to give off the
> pyrolytic gases.? In other words, that secondary air that has passed
> over the fuel is part of the problem, not part of a solution because it
> has taken heat away from the fuel.
>
> Your statements therefore are misleading, and a dis-service to any
> novice trying to understand the important differences about where and
> how primary and secondary air enters and performs.
>
> 3.? Tertiary air:?? Defined as either 1) the needed secondary air that
> did not get into the combustion zone soon enough (meaning that there was
> poor stove design) or 2) excess air that will lower the temperature of
> the hot gases (meaning that this "tertiary air" was NOT needed nor part
> of the combustion process).
>
> Either way, the concept of "tertiary air" is bogus in the context of
> cookstove combustion.? The objective is to get the combustion to be
> complete with the proper amounts of primary and secondary air at the
> correct times and places.
>
> 4.? You wrote:
> > This [MPF} process is ... how the Terra Preta soils in the Amazon were
> > created over 20,000 years of slash and burn agriculture.
> The origins of Terra Preta are still being debated by the experts in
> that field, which is certainly not your claimed field of expertise.
> > The Amerindians cultivated land that was already productive, they did
> > not create it /de novo/. Cecil confirms they farm patches of land that
> > are already productive, not random areas. He observed this when he was
> > doing PhD field research while at Harvard.
> I have great respect for Cecil Cook.?? But somehow what you have
> attributed to him and his work has not reach my attention previously. ?
> And I do not accept your statements. ? What happened thousands of years
> ago was not witnessed by Cecil.?? He could only observe the current day
> activities on lands that somehow became fertile.? You can take that
> topic to the Biochar Listserv, if you want to discuss it further.
>
> Sorry, I reject much of what you wrote.? I would not want you to be
> instructing people about TLUD stoves and char making and Terra Preta.??
> IMHO, your comments about pyrolysis in different devices reflect poorly
> on your credibikity regarding your other strongly expressed positions,
> but that is a topic for others to discuss.
>
> Paul
>
> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
> Email: psanders at ilstu.edu
> Skype: paultlud Phone: +1-309-452-7072
> Website: www.drtlud.com
>
> On 12/9/2017 9:03 PM, Crispin Pemberton-Pigott wrote:
> > Dear Ron
> >
> > I see no systematic differences between the uses of the terms. You are
> > trying to create some special meaning for quite ordinary processes of
> > combustion.
> >
> > It is unfortunate you mix baseless assertions, projections of motive
> > onto others and micro-aggressions ?into your erroneous analyses and
> > combustion theory. It is wearying trying to separate your mistakes
> > from your agendas.
> >
> > For the rest of our readers, these definitions may be useful:
> >
> > Primary air refers to that atmospheric oxygen used to convert a
> > combustible fuel into a gaseous state through thermal decomposition.
> > It is needed to combust gaseous fuels if the gas is not composed of
> > molecules that can be oxidised directly (evaporated kerosene, for
> > example).
> >
> > Secondary air is that atmospheric oxygen which is used to combust
> > those ?gases at some location generally distinct from the solid fuel.
> >
> > Tertiary air is that atmospheric oxygen separately added to the gas
> > combustion phase in order to complete the combustion and or to
> > moderate the gas temperature? to fall within some desired range (for
> > example a low-NOx burner or a fish dryer).
> >
> > While a TLUD's migrating pyrolytic front (MPF) can produce char from
> > biomass, there are other methods of doing so. Two that have a higher
> > theoretical char yield ?are the charcoal kilns designed by Chris Adams
> > (the Adam Retort) and the World Stove. Their working principles are
> > not the same as the TLUD. Both produce a combustible gas that is
> > applied to a process outside the charring of biomass.
> >
> > In the char producing ?section of the Adam Retort there is no primary
> > air supplied at all but it still has an MPF proceeding in a roughly
> > horizontal direction. The World Stove supplies some primary air in the
> > beginning but only secondary air later. Still later, primary air is
> > again supplied if the operator wishes to burn the char produced.
> >
> > All three of these approaches have proven effective. Of the three, the
> > Adam Retort has the highest char production fraction per kg of input
> > material, the widest range of usable materials and the least possible
> > preparation required. The seven drum kiln designed by Dr AD Karve
> > operates on the same principles and is specialised to char leaves. A
> > small percentage of the fuel ends up in the ground as biochar.
> >
> > A higher fraction of the char ends up in the ground? when it is
> > produced using the earth pit charcoal production process. I have not
> > seen this discussed on the Stoves list. An investigation by Cecil Cook
> > in Mozambique into the ultimate destination of char conducted while
> > working for ProBEC/GTZ showed that a considerable fraction of char
> > produced ended up under the pot and the rest ended up on or in the
> > ground, which you have termed variously as 'sequestration' and some
> > form of fertilization.
> >
> > ?There is nothing magical or new about an MPF and it does not need a
> > special vocabulary to describe it. In Southern California the
> > devastating forest fires are leaving behind millions of smouldering
> > tree stumps each of which has an MPF moving along its stump and major
> > underground roots. This process is as old as fire. It is how the Terra
> > Preta soils in the Amazon were created over 20,000 years of slash and
> > burn agriculture. The Amerindians cultivated land that was already
> > productive, they did not create it /de novo/. Cecil confirms they farm
> > patches of land that are already productive, not random areas. He
> > observed this when he was doing PhD field research while at Harvard.
> >
> > I hope others can get contribute to especially the technical aspects
> > of the discussion. I will close with a reminder that the highest char
> > production fraction I have encountered (45%) is the Hawaiian
> > pressurised kiln which uses a controlled primary air supply and an MPF
> > to char a five foot long log one foot in diameter in 45 minutes. "45
> > in 45".
> >
> > ?Amazing.
> >
> > Regards
> > Crispin
> > ?
> Ron Larson wrote:
> > Todd:
> >
> > Thanks for the comment. ?I urge readers to visit
> > https://www.silverfire.us/
> > <https://eur03.safelinks.protection.outlook.com/?url=
> https%3A%2F%2Fwww.silverfire.us%2F&data=02%7C01%7C%
> 7C2f4e87e571974e97b4cf08d53f3a03ae%7C84df9e7fe9f640afb435aaaaaaaa
> aaaa%7C1%7C0%7C636484440759723211&sdata=2uvPfW50fAZhf81ZYqCzad40wiN2th
> 9I1xzu7%2BCy7wM%3D&reserved=0>.
> > ?Some nice looking designs.
> >
> > I can?t quite accept your message below (and one from Crispin that we
> > received 1:23 hours later). ?You are both using the terms primary and
> > secondary in a different (not wrong - just different) sense from those
> > of us interested in char-making. ?We char-makers (or at least the TLUD
> > design - Nat Mulcahy and World Stove have a still different meaning to
> > this nomenclature) use primary air (meaning oxygen) as something that
> > is totally depleted at/near the pyrolysis front. ?No oxygen in the
> > exiting pyrolysis gases, where they are met by secondary air (oxygen).
> >
> > I am pretty sure you and Crispin (who is also discussing char-using
> > stoves) do not mean the above. ?Rather ?primary? means plenty of air
> > (controllable to a minimum degree) to both create and consume char.
> > ?Your and most Rockets (regardless of pre-heating) find char to be a
> > defect; ?you would have preferred to consume it, I believe. (I?d love
> > to hear that you welcome the char.) ?So your ?secondary? is to be sure
> > that the ?small? amount of uncombusted gases leaving the fuel bed are
> > combusted. ? I am NOT disputing your phrase below (?Secondary
> > combustion /is possible /with a rocket stove?). ?I am only saying that
> > secondary air is mandatory with TLUDs, and has a totally different
> > function than ?primary? air. ? Most of your primary air consumes char.
> >
> > The dialog between Paul and myself below on secondary air is different
> > than your own explanation below on its preheating.
> >
> > Do we agree that the terms ??primary? and ?secondary? have very
> > different meanings in these two different parts of the stove world?
> >
> > Ron
> >
> >
> >> On Dec 9, 2017, at 12:32 AM, Todd Albi <todd.r.albi at gmail.com
> >> <mailto:todd.r.albi at gmail.com>> wrote:
> >>
> >> Ron:
> >>
> >> Not quite correct.? Secondary combustion/is possible/ with a rocket
> >> stove.? Our Survivor Rocket stove launched 5 years ago introduced
> >> preheated ventilation ductwork at launch.? In fact we only offer a
> >> primary & secondary combustion design rocket stove. Thats why our
> >> stove incorporates 360 degree ventilation through base of stove, tied
> >> to ventilation ductwork behind combustion chamber walls. The double
> >> insulated walls allow preheated air to travel behind firebox and mix
> >> at chimney base, before exiting cooktop.? Others have also now added
> >> preheated channels and secondary gasification to rocket stoves. It is
> >> not an inclusive to TLUD designs and can be adapted to any stove
> >> firebox.
> >>
> >>
>
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> ------------------------------
>
> Message: 9
> Date: Sun, 10 Dec 2017 05:54:25 +0000
> From: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID:
> <MWHPR22MB0784E3241D4CCBEEF34FC61DB1360 at MWHPR22MB0784.
> namprd22.prod.outlook.com>
>
> Content-Type: text/plain; charset="utf-8"
>
> Dear Paul
>
> >Some of what you wrote is correct, but you go too far or leave out some
> important distinctions, thereby implying that some things are equal, that
> is, some are not really as worthy and distinctive as others (Ron and Paul)
> have stated.
>
> Of course there were things left out. I am happy you included below
> further refinements to the explanation.
>
> >1. Pyrolysis progresses (migrates) through a piece or pile of biomass as
> heat is able to penetrate. True. The Adam retort (and other retorts)
> heat the biomass from many sides, but there is no flame (actual combustion)
> inside. It is a stretch of language to say that the pyrolysis in the retort
> >>has an MPF [migrating pyrolytic front] proceeding in a roughly
> horizontal direction.
>
> Au contraire. The Adam Retort (which heats the biomass from under a
> portion of the bottom of the pile, not multiple sides) does indeed have a
> MPF and the combustion is fed by oxidation using oxygen liberated by the
> thermal decomposition of the fuel. There is no added oxygen, but oxygen
> there definitely is. There is enough oxygen in biomass to almost completely
> combust the hydrogen content. In practise the carbon and hydrogen are both
> involved in sustaining the MPF. Once the fuel is hot enough, the MPF can
> move through the pile without any additional heat required.
>
> >Sorry, that should say "has external heating proceeding inward from
> several directions from the sides toward the center."
>
> That is an incorrect description of the Adam Retort. There are retorts
> that function in the manner you describe. His is not one of them.
>
> >Furthermore, the processes in a retort are in sequential order during
> numerous minutes to 1) heat virtually all of the biomass to drive off the
> moisture, then 2) add more heat to virtually all of the biomass to drive
> off the low-temperature volatiles to create torrified material, and than 3)
> to finally get the temperature hot enough to have actual pryrolysis, first
> in the 400 deg C range and then at higher temperatures if the external
> heating is continued.
>
> That is true for some retorts, not the Adams Retort.
>
> >In sharp contrast, in a TLUD there is a distinctive zone of a few cm
> depth with actual small amounts of combustion (of some of the initial
> offgases). That zone migrates through the pile of biomass, heating mainly
> by radiation a small layer of biomass below the MPF, then with pyrolysis
> at a rather uniform temperature (generally from 450 to 700 C, depending on
> USER CONTROLED [sic] flow of primary air) to create the char as the gases
> move upward.
>
> The same also happens in a downdraft pyrolyser, and a bottom-pit updraft
> pyrolyser such as those produce by Hirendra Chakrabarti in India.
>
> The addition of a control feature makes the process variable, however it
> does not fundamentally change how the system works.
>
> >You may choose to try to equate the two descriptions above, but that
> would diminish your credibility as a precision-seeking scientist.
>
> There is no need for that kind of talk. First familiarise yourself with
> the systems under discussion. Seen from the side, an Adam Retort starts the
> MPF on the bottom right and it moves over a period of about 2 hours to the
> top left. Prof Lloyd can provide examples of sustained MPF?s moving
> horizontally underground in the Witbank area of South Africa without any
> addition of primary air. There are conditions where primary is required,
> and others when it is not. Tiny stoves require it.
>
> >And to equate a smouldering tree stump to MPF is a stretch beyond a
> stretch. Yes, there is fire there, and yes there is pyrolysis occuring.
> But such comparison is akin to saying that a ladybug and a moose are the
> same because both are living creatures; and in fact both are animals.
> Even a petunia and a whale are both living organisms. Scientific
> comparisons need precision and detail.
>
> That is why the discussion is on principles not ladybugs. A dry tree stump
> can be ignited to char the stump and the roots underground, and in the
> 1800?s one could buy a kit for doing so. I was told of a different method
> when I was young involving a steel pipe and kerosene. The point was to get
> the stump hot enough so that the pyrolysis would continue into the ground.
> The TLUD stove with an MPF is no more than a containerised version with
> controllable primary air.
>
> 2. Ron correctly pointed out that in normal operation of TLUD stoves,
> there is zero O2 that gets past the MPF. That is vastly different from
> having so much primary air enter (as in Rocket stoves and other burners)
> that there is O2 moving upward above the fuel (where the gases were
> created).
>
> Ron is correct about the O2. It is indeed different (I don?t know about
> ?vastly? from stoves where the fuel and flames are ?attached? to the solid
> fuel and the gases oxidise as and when they can. it is also true (but I
> didn?t expound on it) that within a fuel bed there are zones without no
> available O2, just as in the zone above the char.
>
> >You are saying that is good as preheated secondary O2.
>
> Functionally that is secondary air provided simultaneously, at least in
> some cases. My definitions are general cases and can be applied to the
> situation you describe.
>
> >Maybe, but not really. It is simply inadequate combustion, with the
> results of undesirable emissions.
>
> That is speculation and cannot be true in all cases.
>
> >The excessive primary air (which you state should be secondary air)...
>
> Which I state has the function of providing secondary air?
>
> >?has had a cooling effect on the raw fuel that the combustion is trying
> to get hot enough to give off the pyrolytic gases.
>
> That is not a general case. It could happen.
>
> >In other words, that secondary air that has passed over the fuel is part
> of the problem, not part of a solution because it has taken heat away from
> the fuel.
>
> That is not the case. What ?problem?? Heat passed through a metal wall to
> secondary air is not ?different heat? from that gained by air passing
> through a fuel bed, or along a hot combustion chamber wall. There are many
> roads to Rome. Air that is consumed after preheating is indifferent to hwo
> the heat was gained.
>
> >3. Tertiary air: Defined as either 1) the needed secondary air that
> did not get into the combustion zone soon enough (meaning that there was
> poor stove design)
>
> I see this as inaccurate on two counts: 1) the secondary air may be added
> in a way that decomposes complex gases further before final combustion, and
> 2) the bit about poor design is unfair comment. There are many good designs
> you may not know about.
>
> >?or 2) excess air that will lower the temperature of the hot gases
> (meaning that this "tertiary air" was NOT needed nor part of the combustion
> process).
>
> Tertiary air may be provided for a number of reasons, but normally to
> provide the oxygen needed to complete combustion with a desirable level of
> free O2 in the gases. Under certain circumstances, for example natural gas
> boilers, the level of free O2 is very low (1% by volume). To maintain such
> a low level of excess air it may be necessary to have tertiary or even more
> air injection points.
>
> >Either way, the concept of "tertiary air" is bogus in the context of
> cookstove combustion.
>
> That is opinion only, contradicted by existing technologies that use it.
> One of the highest performing stick-burning stoves available has tertiary
> air injection ? the Rocketworks stoves from Adrian Padt in Durban, tens of
> thousands of which are sold each year.
>
> >The objective is to get the combustion to be complete with the proper
> amounts of primary and secondary air at the correct times and places.
>
> That is true in some cases and not in others. Most Rocket stoves (per
> Aprovecho design guides) have only a single air entrance. The Rocketworks
> stoves have three distinct times and places.
>
> >4. You wrote:
> >>This [MPF} process is ... how the Terra Preta soils in the Amazon were
> created over 20,000 years of slash and burn agriculture.
> >The origins of Terra Preta are still being debated by the experts in that
> field, which is certainly not your claimed field of expertise.
>
> I am sorry to hear you talk about ?fields of expertise?. Facts in evidence
> speak for themselves and are not invalidated by any messenger claims.
>
> >>The Amerindians cultivated land that was already productive, they did
> not create it de novo. Cecil confirms they farm patches of land that are
> already productive, not random areas. He observed this when he was doing
> PhD field research while at Harvard.
>
> >I have great respect for Cecil Cook. But somehow what you have
> attributed to him and his work has not reach my attention previously.
>
> So what?
>
> >And I do not accept your statements.
>
> I don?t care. I cared to know, by interviewing him, how the Amerindians
> farmed and what role char had in their agriculture. I reported this
> previously to this list. Maybe you forgot. It is in the archives. At the
> time Ron replied that did didn?t accept the observational reports from
> Cecil who lived in the jungle for 4 years learning how their agricultural
> society functions.
>
> >What happened thousands of years ago was not witnessed by Cecil. He
> could only observe the current day activities on lands that somehow became
> fertile.
>
> He reported observations, the most important of which is that they do not
> practise slash and burn farming over whole areas, but only the fertile
> bits. The practice of slash and burning creates a lot of char in the
> ground, something contested by Ron at that time and diminished by your
> message regarding the tree stumps burning in California. If you don?t
> believe me, you can visit the area right now and witness the MPFs moving
> into the ground to charcoal the root systems. A major part of the work of
> firefighters is extinguishing these MPFs. This is sufficient to convince me
> they exist. If they exist, they are producing biochar in the ground.
>
> >You can take that topic to the Biochar Listserv, if you want to discuss
> it further.
>
> I have no interest in discussions on another list. I receive information
> from the Biochar-Ontario group.
>
> >Sorry, I reject much of what you wrote.
>
> Don?t be sorry. Learn and be happy! We are sharing perspectives here.
>
> >I would not want you to be instructing people about TLUD stoves and char
> making and Terra Preta.
>
> That is none of your business over which you have no control.
>
> >IMHO, your comments about pyrolysis in different devices reflect poorly
> on your credibikity [sic] regarding your other strongly expressed
> positions, but that is a topic for others to discuss.
>
> And I feel sometimes you could learn a thing or two before posting
> comments about other technologies. Like everyone else, I find your
> contributions worthy and partially correct.
>
> Perhaps there is something you could answer: Is there something about char
> making that requires or drives their proponents to make completely
> unnecessary personal attacks and derisive, inaccurate speculations about
> motives? Outside the agricultural sector and the production of
> char-enhanced fertilisers, I find the biochar enthusiasts as a group to be
> cloistered and fanatical, frequently engaging in divisive speech about
> something they have recently discovered.
>
> I should take a minute to compliment you, Xavier, Julien, Jonas Haller and
> Dr Nurhuda for being very open to exchange with me advice, explanations and
> observations without reservations about how or where the information
> originates. All of you have produced very interesting and effective
> products suited to certain communities.
>
> Best regards for a better burn
> Crispin
>
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> ------------------------------
>
> Message: 10
> Date: Sun, 10 Dec 2017 10:07:42 +0000
> From: Andrew Heggie <aj.heggie at gmail.com>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Bangladesh TLUD (was Re: No subsidies in TLUD
> char peoduction
> Message-ID:
> <CAPSaZeYYcBrD_mr3KsUO1q_2EOcncKd8LYkmDraA1-KMD6AWsw@
> mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> On 10 December 2017 at 03:06, Crispin Pemberton-Pigott
> <crispinpigott at outlook.com> wrote:
> > What a great insight. What s the material called in the shelf?
>
> Just ferrocement I think. The same can be done with portland cement
> but that takes days to cure and gain sufficient strength.
>
> I wasn't in the civil engineering department and no longer have
> contact with the schoolmate that did it. I think there were long term
> issues with the salty beach sand but these boats only needed to laste
> a day or so.
>
>
>
> ------------------------------
>
> Message: 11
> Date: Sun, 10 Dec 2017 08:32:36 -0700
> From: Gordon West <gordon.west at rtnewmexico.com>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID: <DDD0427A-3E0D-4CE9-BE15-10542E3056F1 at rtnewmexico.com>
> Content-Type: text/plain; charset="utf-8"
>
> I took a look at the Adams Retort design and watched a few videos. A
> couple of questions come to mind:
>
> 1) How does one determine that an MPF exists in an A-R?
>
> 2) I am not much of a chemist, but I would be interested to see an
> explanation of the reaction sequence where O2 is released and then burned
> in the MPF of an Adams Retort.
>
> It seems to me that if the external heat source is raising the temperature
> to the gasification point of the volatile components, thereby causing
> gasification (duh?), what purpose is the MPF serving?
>
> In a TLUD the MPF is burning some of the volatile gases to generate the
> heat needed to gasify un-pyrolyzed biomass.
>
> Gordon
>
>
>
> > On Dec 9, 2017, at 10:54 PM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com> wrote:
> >
> > Dear Paul
> >
> > >Some of what you wrote is correct, but you go too far or leave out some
> important distinctions, thereby implying that some things are equal, that
> is, some are not really as worthy and distinctive as others (Ron and Paul)
> have stated.
> >
> > Of course there were things left out. I am happy you included below
> further refinements to the explanation.
> >
> > >1. Pyrolysis progresses (migrates) through a piece or pile of biomass
> as heat is able to penetrate. True. The Adam retort (and other retorts)
> heat the biomass from many sides, but there is no flame (actual combustion)
> inside. It is a stretch of language to say that the pyrolysis in the retort
> > >>has an MPF [migrating pyrolytic front] proceeding in a roughly
> horizontal direction.
> >
> > Au contraire. The Adam Retort (which heats the biomass from under a
> portion of the bottom of the pile, not multiple sides) does indeed have a
> MPF and the combustion is fed by oxidation using oxygen liberated by the
> thermal decomposition of the fuel. There is no added oxygen, but oxygen
> there definitely is. There is enough oxygen in biomass to almost completely
> combust the hydrogen content. In practise the carbon and hydrogen are both
> involved in sustaining the MPF. Once the fuel is hot enough, the MPF can
> move through the pile without any additional heat required.
> >
> > >Sorry, that should say "has external heating proceeding inward from
> several directions from the sides toward the center."
> >
> > That is an incorrect description of the Adam Retort. There are retorts
> that function in the manner you describe. His is not one of them.
> >
> > >Furthermore, the processes in a retort are in sequential order during
> numerous minutes to 1) heat virtually all of the biomass to drive off the
> moisture, then 2) add more heat to virtually all of the biomass to drive
> off the low-temperature volatiles to create torrified material, and than 3)
> to finally get the temperature hot enough to have actual pryrolysis, first
> in the 400 deg C range and then at higher temperatures if the external
> heating is continued.
> >
> > That is true for some retorts, not the Adams Retort.
> >
> > >In sharp contrast, in a TLUD there is a distinctive zone of a few cm
> depth with actual small amounts of combustion (of some of the initial
> offgases). That zone migrates through the pile of biomass, heating mainly
> by radiation a small layer of biomass below the MPF, then with pyrolysis
> at a rather uniform temperature (generally from 450 to 700 C, depending on
> USER CONTROLED [sic] flow of primary air) to create the char as the gases
> move upward.
> >
> > The same also happens in a downdraft pyrolyser, and a bottom-pit updraft
> pyrolyser such as those produce by Hirendra Chakrabarti in India.
> >
> > The addition of a control feature makes the process variable, however it
> does not fundamentally change how the system works.
> >
> > >You may choose to try to equate the two descriptions above, but that
> would diminish your credibility as a precision-seeking scientist.
> >
> > There is no need for that kind of talk. First familiarise yourself with
> the systems under discussion. Seen from the side, an Adam Retort starts the
> MPF on the bottom right and it moves over a period of about 2 hours to the
> top left. Prof Lloyd can provide examples of sustained MPF?s moving
> horizontally underground in the Witbank area of South Africa without any
> addition of primary air. There are conditions where primary is required,
> and others when it is not. Tiny stoves require it.
> >
> > >And to equate a smouldering tree stump to MPF is a stretch beyond a
> stretch. Yes, there is fire there, and yes there is pyrolysis occuring.
> But such comparison is akin to saying that a ladybug and a moose are the
> same because both are living creatures; and in fact both are animals.
> Even a petunia and a whale are both living organisms. Scientific
> comparisons need precision and detail.
> >
> > That is why the discussion is on principles not ladybugs. A dry tree
> stump can be ignited to char the stump and the roots underground, and in
> the 1800?s one could buy a kit for doing so. I was told of a different
> method when I was young involving a steel pipe and kerosene. The point was
> to get the stump hot enough so that the pyrolysis would continue into the
> ground. The TLUD stove with an MPF is no more than a containerised version
> with controllable primary air.
> >
> > 2. Ron correctly pointed out that in normal operation of TLUD stoves,
> there is zero O2 that gets past the MPF. That is vastly different from
> having so much primary air enter (as in Rocket stoves and other burners)
> that there is O2 moving upward above the fuel (where the gases were
> created).
> >
> > Ron is correct about the O2. It is indeed different (I don?t know about
> ?vastly? from stoves where the fuel and flames are ?attached? to the solid
> fuel and the gases oxidise as and when they can. it is also true (but I
> didn?t expound on it) that within a fuel bed there are zones without no
> available O2, just as in the zone above the char.
> >
> > >You are saying that is good as preheated secondary O2.
> >
> > Functionally that is secondary air provided simultaneously, at least in
> some cases. My definitions are general cases and can be applied to the
> situation you describe.
> >
> > >Maybe, but not really. It is simply inadequate combustion, with the
> results of undesirable emissions.
> >
> > That is speculation and cannot be true in all cases.
> >
> > >The excessive primary air (which you state should be secondary air)...
> >
> > Which I state has the function of providing secondary air?
> >
> > >?has had a cooling effect on the raw fuel that the combustion is trying
> to get hot enough to give off the pyrolytic gases.
> >
> > That is not a general case. It could happen.
> >
> > >In other words, that secondary air that has passed over the fuel is
> part of the problem, not part of a solution because it has taken heat away
> from the fuel.
> >
> > That is not the case. What ?problem?? Heat passed through a metal wall
> to secondary air is not ?different heat? from that gained by air passing
> through a fuel bed, or along a hot combustion chamber wall. There are many
> roads to Rome. Air that is consumed after preheating is indifferent to hwo
> the heat was gained.
> >
> > >3. Tertiary air: Defined as either 1) the needed secondary air that
> did not get into the combustion zone soon enough (meaning that there was
> poor stove design)
> >
> > I see this as inaccurate on two counts: 1) the secondary air may be
> added in a way that decomposes complex gases further before final
> combustion, and 2) the bit about poor design is unfair comment. There are
> many good designs you may not know about.
> >
> > >?or 2) excess air that will lower the temperature of the hot gases
> (meaning that this "tertiary air" was NOT needed nor part of the combustion
> process).
> >
> > Tertiary air may be provided for a number of reasons, but normally to
> provide the oxygen needed to complete combustion with a desirable level of
> free O2 in the gases. Under certain circumstances, for example natural gas
> boilers, the level of free O2 is very low (1% by volume). To maintain such
> a low level of excess air it may be necessary to have tertiary or even more
> air injection points.
> >
> > >Either way, the concept of "tertiary air" is bogus in the context of
> cookstove combustion.
> >
> > That is opinion only, contradicted by existing technologies that use it.
> One of the highest performing stick-burning stoves available has tertiary
> air injection ? the Rocketworks stoves from Adrian Padt in Durban, tens of
> thousands of which are sold each year.
> >
> > >The objective is to get the combustion to be complete with the proper
> amounts of primary and secondary air at the correct times and places.
> >
> > That is true in some cases and not in others. Most Rocket stoves (per
> Aprovecho design guides) have only a single air entrance. The Rocketworks
> stoves have three distinct times and places.
> >
> > >4. You wrote:
> > >>This [MPF} process is ... how the Terra Preta soils in the Amazon were
> created over 20,000 years of slash and burn agriculture.
> > >The origins of Terra Preta are still being debated by the experts in
> that field, which is certainly not your claimed field of expertise.
> >
> > I am sorry to hear you talk about ?fields of expertise?. Facts in
> evidence speak for themselves and are not invalidated by any messenger
> claims.
> >
> > >>The Amerindians cultivated land that was already productive, they did
> not create it de novo. Cecil confirms they farm patches of land that are
> already productive, not random areas. He observed this when he was doing
> PhD field research while at Harvard.
> >
> > >I have great respect for Cecil Cook. But somehow what you have
> attributed to him and his work has not reach my attention previously.
> >
> > So what?
> >
> > >And I do not accept your statements.
> >
> > I don?t care. I cared to know, by interviewing him, how the Amerindians
> farmed and what role char had in their agriculture. I reported this
> previously to this list. Maybe you forgot. It is in the archives. At the
> time Ron replied that did didn?t accept the observational reports from
> Cecil who lived in the jungle for 4 years learning how their agricultural
> society functions.
> >
> > >What happened thousands of years ago was not witnessed by Cecil. He
> could only observe the current day activities on lands that somehow became
> fertile.
> >
> > He reported observations, the most important of which is that they do
> not practise slash and burn farming over whole areas, but only the fertile
> bits. The practice of slash and burning creates a lot of char in the
> ground, something contested by Ron at that time and diminished by your
> message regarding the tree stumps burning in California. If you don?t
> believe me, you can visit the area right now and witness the MPFs moving
> into the ground to charcoal the root systems. A major part of the work of
> firefighters is extinguishing these MPFs. This is sufficient to convince me
> they exist. If they exist, they are producing biochar in the ground.
> >
> > >You can take that topic to the Biochar Listserv, if you want to discuss
> it further.
> >
> > I have no interest in discussions on another list. I receive information
> from the Biochar-Ontario group.
> >
> > >Sorry, I reject much of what you wrote.
> >
> > Don?t be sorry. Learn and be happy! We are sharing perspectives here.
> >
> > >I would not want you to be instructing people about TLUD stoves and
> char making and Terra Preta.
> >
> > That is none of your business over which you have no control.
> >
> > >IMHO, your comments about pyrolysis in different devices reflect poorly
> on your credibikity [sic] regarding your other strongly expressed
> positions, but that is a topic for others to discuss.
> >
> > And I feel sometimes you could learn a thing or two before posting
> comments about other technologies. Like everyone else, I find your
> contributions worthy and partially correct.
> >
> > Perhaps there is something you could answer: Is there something about
> char making that requires or drives their proponents to make completely
> unnecessary personal attacks and derisive, inaccurate speculations about
> motives? Outside the agricultural sector and the production of
> char-enhanced fertilisers, I find the biochar enthusiasts as a group to be
> cloistered and fanatical, frequently engaging in divisive speech about
> something they have recently discovered.
> >
> > I should take a minute to compliment you, Xavier, Julien, Jonas Haller
> and Dr Nurhuda for being very open to exchange with me advice, explanations
> and observations without reservations about how or where the information
> originates. All of you have produced very interesting and effective
> products suited to certain communities.
> >
> > Best regards for a better burn
> > Crispin
> >
> > _______________________________________________
> > Stoves mailing list
> >
> > to Send a Message to the list, use the email address
> > stoves at lists.bioenergylists.org
> >
> > to UNSUBSCRIBE or Change your List Settings use the web page
> > http://lists.bioenergylists.org/mailman/listinfo/stoves_
> lists.bioenergylists.org
> >
> > for more Biomass Cooking Stoves, News and Information see our web site:
> > http://stoves.bioenergylists.org/
> >
>
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> ------------------------------
>
> Message: 12
> Date: Sat, 9 Dec 2017 16:35:16 -0500
> From: Nikhil Desai <ndesai at alum.mit.edu>
> To: Xavier Brandao <xav.brandao at gmail.com>
> Cc: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>, Crispin Pemberton-Pigott
> <crispinpigott at outlook.com>, Frank Shields <franke at cruzio.com>
> Subject: Re: [Stoves] Going back to 3-Stone Fire [Was Re: China and
> cookstoves]
> Message-ID:
> <CAK27e==hDxvAqLLfUuxHC8ZAh15is=epPR8CJ
> 2+qQdWdY+ajpg at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Xavier:
>
> Yours is not a broken record. Some record needs to be played again and
> again in the hope that somebody would listen.
>
> After all, parroting the virtues of WBT is no different. Another song,
> another record.
>
> I still don't know why this List matters to anything to do with WBT.
>
> I have asked you to cite evidence of who has been damaged by whom in
> forcing the use of WBT.
>
> I don't see anybody cares. Yes, CDM may be misled by WBT results, but Gold
> Standard has no concern in "voluntary carbon". They are prepared to be
> fooled by anything, so long as they earn their fees. WBT is handy.
>
> Neither CDM nor Gold Standard are accountable to anybody (but some
> hoity-toity experts ready to fume). Their earnings don't depend on stove
> test protocols or stove designs, only on making up CO2 reduction claims
> based on fNRB (fraction non-renewable biomass), which in t urn is a game
> of story-telling.
>
> Some designer and marketer of stoves may have a peeve -- as you and Crispin
> seem to have -- if their markets are distorted or disrupted by wrong test
> protocols.
>
> But that case hasn't been made yet. I remember some tales about WBT being
> forced by GACC - making its financial support conditional on WBT and
> particular type of testing equipment - upon some innocent governments. But
> not only do I find any demonstration of a "harm" - which becomes a basis
> for a claim, legal or in the marketplace for ideas or stoves - I realize
> that this is all a voluntary carnival, an orgy.
>
> Which is why Frank finds it every new year - time to toast a champagne for
> another year of wasting time and money on doing very little that may help
> poor cooks
>
> Nobody has any authority to establish the WBT or any other test protocol as
> a "standard". EPA doesn't. GACC doesn't. They - and their contractors - can
> do anything they want with impunity.
>
> I do not mind recreational use of drugs - er, models, theories - by
> youngsters. But they are not good for adults, and frequent, long-term use
> leads to addiction, with uncertain consequences.
>
> How and why did WBT come about? From the theory in 1970s that inefficient
> fuel use led to"forest" resource degeneration and loss.
>
> In some places and at certain times this was true. However, land has many
> uses and deforestation has many causes and growth/decline/loss patterns.
> Abstracting from some areas and generating an image of national and global
> resource loss due primary to fuel inefficiency was a theory with no facts.
> The converse argument - that more efficient stoves would prevent such
> resource loss or reverse it - was even less tenable.
>
> But some people - including you and Crispin here, one youngster, one
> middle-aged it seems - still enjoy the smoke. You seem to think that WBT
> predictions of "fuel savings" are a big deal. I don't. What does saving the
> fuel do and for whom?
>
> All I can say is that instead of my earlier question "Who is harmed by the
> use of WBT?" it's time now to ask "Who benefits from the use of WBT?"
>
> That would tell you all you need to know about why WBT has become an
> addiction. Pretend-science is built around manifestly falsifiable theories.
>
> Nikhil
>
>
>
>
> ------------------------
> Nikhil Desai
> (US +1) 202 568 5831
> *Skype: nikhildesai888*
>
> On Fri, Dec 8, 2017 at 4:54 PM, Xavier Brandao <xav.brandao at gmail.com>
> wrote:
>
> > Hello Frank,
> >
> >
> >
> > Ahah, there is indeed a pattern, you might have noticed it is usually the
> > following:
> >
> > 1. Someone, usually Ron or a member of the GACC, EPA, Aprovecho, D-Lab
> > or Winrock, innocently drops ? WBT is a great protocol to make stove
> > improvements ? or ? you know, there are many supporters of the WBT ?,
> > somewhere in a post, a handbook or a toolkit
> >
> > 2. Then, some of us howls in indignation, especially me. I start to rant
> > and sound like a broken record. Then I hand over, once again, the pile of
> > evidence, and ask some very simple straightforward questions.
> >
> > 3. Suddenly the one in 1. very kindly tells me, in a
> > ? ho-it-would-be-so-great-to-have-you-there ? fashion, to:
> >
> > a. Join the ISO-TC 285 discussions
> >
> > b. Join a certain conference in the United States
> >
> > c. Or becomes suddenly completely mute
> >
> > Often it is a., b. then c.
> >
> > 4. Then a few months pass by, and one beautiful day, we are back to step
> > 1.
> >
> >
> >
> > At this point it?s not a rabbit hole, it?s more like a rabbit loop, a
> > rabbit loophole.
> >
> >
> > Best,
> >
> >
> >
> > Xavier
> >
> >
> >
> >
> >
> >
> >
> > -----Message d'origine-----
> > De : Stoves [mailto:stoves-bounces at lists.bioenergylists.org
> > <stoves-bounces at lists.bioenergylists.org>] De la part de
> franke at cruzio.com
> > Envoy? : jeudi 7 d?cembre 2017 21:56
> > ? : ndesai at alum.mit.edu
> > Cc : Crispin Pemberton-Pigott; Discussion of biomass cooking stoves
> > Objet : Re: [Stoves] Going back to 3-Stone Fire [Was Re: China and
> > cookstoves]
> >
> >
> >
> >
> >
> > Dear Nikhil, Stovers,
> >
> >
> >
> > Always great news when we start a new year talking WBT. That because it
> > means we are not still down some rabbit hole someone has sent us to
> wallow
> > around for a few years on some useless idea only to come to the surface
> and
> > find us where we started (NOWHERE). But now starting at NOWHERE we must
> be
> > careful we are not diverted down another rabbit hole. Make sure all
> project
> > proposals involve the 6-Box system or parts of it. That involves both
> Field
> > and Lab work. Because that is the only way we get control over the
> > variables and move forward. A lot of work needs be done.
> >
> >
> >
> > Regards
> >
> > Frank Shields
> >
> > Gabilan Laboratory
> >
> >
> > <https://www.avast.com/sig-email?utm_medium=email&utm_
> source=link&utm_campaign=sig-email&utm_content=emailclient> Garanti
> > sans virus. www.avast.com
> > <https://www.avast.com/sig-email?utm_medium=email&utm_
> source=link&utm_campaign=sig-email&utm_content=emailclient>
> > <#m_-3021670524595202001_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> >
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> ------------------------------
>
> Message: 13
> Date: Sat, 9 Dec 2017 14:45:58 -0500
> From: Nikhil Desai <pienergy2008 at gmail.com>
> To: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
> Cc: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>, Todd Albi <
> todd.r.albi at gmail.com>
> Subject: Re: [Stoves] Bangladesh TLUD (was Re: No subsidies in TLUD
> char peoduction
> Message-ID:
> <CAK27e=m+GA7hvGFH9ujHnJ_DrM8qaG2kHYUzsXE4ZAXjRdK3Vg@
> mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Crispin:
>
> Did Peter Scott use WBT or CCT? Why are his findings significant except for
> "competing on fuel efficiency percentages"?
>
> What he discovered is similar to common knowledge from my childhood - in
> samovars for heating bathwater. Designs with thicker copper retained heat
> better and fuel efficiency was higher; which mattered because in the city
> we used purchased charcoal.
>
> Something similar from our charcoal cooking stoves - they had a cement
> layer sometimes, compared to another stove that didn't.
>
> If you standardize the cooking experience and cooking behavior, I suppose
> you can adjust for the amount of heat that goes in the stove body but is
> not utilized for cooking experience.
>
> And if you were to do that, you would come up with some computation of
> efficiency. Which I call "competing on fuel efficiency percentages is
> infantile business" because standardizing cooking behavior and cooking
> experience is infantilism.
>
> That has nothing to do with whether fuel efficiency matters or dominates
> consumer choice.
>
> Testing and metrics ought to have a purpose. In relation to a service
> standard and objective of the exercise. I compared EPA/WHO approach to
> stoves with that on diesel engines. That should say a lot.
>
> Nikhil
>
> --------
>
> On Sat, Dec 9, 2017 at 10:37 AM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com> wrote:
>
> > Dear Nikhil
> >
> > Competition on a fuel efficiency basis is independent of what happens
> > within a stove. The statement about heat invested in the stove body is
> > frequently made with the assumption that 'it is bad' to do so. This has
> > been erroneously promoted by certain organisations that insist in their
> > literature that the combustion chamber must be 'insulative' and have a
> low
> > thermal mass.
> >
> > Well, only one of 'us' has presented a study comparing light vs heavy
> with
> > the same design. That was Peter Scott at ETHOS some years ago. He
> > discovered that contrary to the self-proclaimed wisdom of the time , that
> > the heavy, non-insulative combustion chambers consistently out-performed
> > the light ones by about 10% of value for the efficiency metric.
> >
> > So, here we have Julien discussing the thermal mass of a stove with some
> > jumping in having adopted the incorrect assumption that overall, it is
> > invariably worse to have heat invested in a stove body, without having
> > replicated Peter's experiment.
> >
> > Observing that heat is invested in a stove body is a trivial exercise.
> > Stating what the overall effect on performance will be is far more
> > difficult. The impact is dependent on multiple factors including the
> > emissivity of the outside surface, and whether there are two or more
> layers
> > (shells).
> >
> > To find out which construction or material serves best, we perform
> > efficiency tests and compare numbers. Optimisation is done like that.
> >
> > Regards
> > Crispin
> >
> >
> > Todd:
> >
> > Didn't you mean exclusive rather than inclusive in "It is not an
> > inclusive to TLUD designs and can be adapted to any stove firebox. "?
> >
> > Crispin:
> >
> > If heat loss is insignificant, or only in relation to how it affects the
> > cooking experience, and that heat is stored in the stove for later use,
> you
> > are basically making my point that competing on fuel efficiency
> percentages
> > is infantile business.
> >
> > N
> >
> >
> >
> > On Sat, Dec 9, 2017 at 8:47 AM, Crispin Pemberton-Pigott <
> > crispinpigott at outlook.com> wrote:
> >
> >> Dear Paul and Julien
> >>
> >>
> >>
> >> I am responding to Paul?s comments on Julien?s earlier message.
> >>
> >>
> >>
> >> On Dec 7, 2017, at 6:51 AM, Paul Anderson <psanders at ilstu.edu> wrote:
> >>
> >>
> >>
> >> > 1. The thermal mass is estracting heat, meaning cooler gases inside
> >> the chamber, with risk of insufficient temperature for ignition at the
> top,
> >> especially when nearing the end of pyrolysis.
> >>
> >>
> >>
> >> Before anyone worries about heat going into the stove body, please
> >> perform the trivial calculation about *how much* heat we are talking
> >> about. Just because heat goes into a stove body does not mean a) it is
> >> significant, b) that it happens at a time that affects performance of
> the
> >> cooking experience, c) that it is not returned later in the session
> (which
> >> is cooking behaviour-dependent.) Yes, there is heat invested in the
> stove
> >> and usually it is a loss, but the other features of the stove may not
> only
> >> recover that heat through other energy paths, it may make the stove far
> >> more accessible by being cheap and easy to make from local materials.
> >>
> >>
> >> 2. The concrete (or ceramic) inner cylinder does not have any of the
> >> side holes (24 in the metal version). Such holes allow for some "pilot
> >> light" effect after the char level is below a hole.
> >>
> >>
> >>
> >> Dr Nurhuda?s very successful TLUD stove had such pilots sprinkled around
> >> the fuel chamber. The Vesto uses three holes only, and the purpose is to
> >> maintain pilot lights to ensure the flame never goes out. They are
> placed
> >> in a way that guarantees a small portion of char is burned and there is
> >> never a need to relight because of a gust of wind.
> >>
> >> Regards
> >>
> >> Crispin
> >>
> >>
> >>
> >>
> >
> >
> >
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> ------------------------------
>
> Message: 14
> Date: Sat, 9 Dec 2017 17:51:03 -0500
> From: Nikhil Desai <pienergy2008 at gmail.com>
> To: "Ronal W. Larson" <rongretlarson at comcast.net>
> Cc: Discussion of biomass <stoves at lists.bioenergylists.org>, Xavier
> Brandao <xav.brandao at gmail.com>, Crispin Pemberton-Pigott
> <crispinpigott at outlook.com>, Paul Anderson <psanders at ilstu.edu
> >,
> Julien Winter <winter.julien at gmail.com>
> Subject: Re: [Stoves] Going back to 3-Stone Fire [Was Re: China and
> cookstoves]
> Message-ID:
> <CAK27e=kT-i2K0e99=L-wnaCXm-kF1doR4PCsVJQps5MBf17L-w at mail.
> gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Dear Ron:
>
> All I can say is that you have made no case for the use of WBT by anybody
> who has an interest in standards of cooking and policy of regulating the
> stove business.
>
> That WBT is used by anybody and everybody for decades only confirms my view
> that the so-called stove science is built on fiction passed as theory.
> Groupthink. A religion of the faithful, peers praising pals. Means nothing
> to cooks.
>
> Nothing worthwhile can be said to inform stove design without keeping the
> user and her use patterns at the center, and addressing the regional,
> seasonal, and inter-family (even intra-family) variations in fuels, stove
> use, and, to keep up with the times, rapid changes in demographics,
> cultures, and food/cooking habits I have seen in many parts of the world.
>
> You wrote, "It is argued (by those especially who don?t have one) that
> stove testing laboratories (the main users of the WBT) are unnecessary. "
>
> Touche!
>
> Well, who makes stove testing laboratories use WBT - as you say "some
> version" of WBT - and why? In this country (US), EPA has neither
> promulgated nor approved ANY test protocol for cookstoves, so why are
> Americans spreading the WBT gospel in those parts of the world they know
> very little about?
>
> Nobody I know - not even myself - argues that stove testing laboratories
> are unnecessary. The fundamental question is, what is to be tested and why?
> Then there can be a debate on how to go about best measuring it.
>
> I for one believe that lab testing has its limits in showing anything that
> necessarily determines usability of a stove. The only thing a producer and
> distributor/installer may warrant is some limited definition of safety and
> durability, and perhaps not even that; no producer wants to be responsible
> for misuse of a stove causing a fire.
>
> With the Lima Consensus/IWA metrics and tiers, all I can say is that they
> are for some imaginary cooks and imaginary fuels. Sure, a stove designer
> would submit his stove to testing labs, but he would be stupid to design
> his stove to score on lab results and not on customers' preferences and
> desires.
>
> I hope you find a stove for biochar production that sells and is used. The
> theory behind TC-285 that somehow stoves ranking high on some metric will
> produce a high desired impact on the basic rationale for that metric is
> spurious.
>
> We are told that the four or five metrics are to be judged independently,
> so any test protocol would rate a particular stove as, say, XTi, YTj, ZTk,
> so on, where X is the metric, T the Tier corresponding to that metric, and
> i, j, k etc. are numbers from 1 to 4.
>
> The clear purpose of EPA/UNF manipulation of WHO in the TC-285 process is
> simply this -- anoint stoves NOT using solid fuels as Tier 4, then
> rationalize billions of dollars of funding to market those stoves and
> fuels, namely LPG.
>
> This is clear in the Rosenthal, et al. (2017) Implementation Science to
> Accelerate Clean Cooking for Public Health
> <https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=
> web&cd=1&cad=rja&uact=8&ved=0ahUKEwjjuO6Q_v3XAhURPN8KHVytB2UQFggpMAA&
> url=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%
> 2FPMC5226685%2F&usg=AOvVaw3ErScSEK1n6BL-WjcmxxXL>
> where
> they speak only of "In choosing among clean fuels or combinations (e.g.,
> LPG, biogas, alcohol, electricity, solar, tier 4 indoor emissions biomass
> stoves) and technologies .." endorsing the Johnson-Chiang view "These
> findings suggest that near exclusive, community-wide use of clean fuels is
> needed to meet the PM2.5 guideline and to maximize health benefits"
>
> In the name of "maximizing health benefits" - for which they have zero
> empirical basis, at most only HAPIT deceit - a propaganda is generated for
> "clean fuels".
>
> Which for all practical purposes rules out stoves using solid biomass.
>
> Back to TC-285 rigmarole. GACC said in 2014,
>
> "Develop a Cookstove Rating System and Voluntary Global Standards ?
>
> The sector has made considerable progress in the development of a consensus
> voluntary global standard. This standard will enable the rating of
> cookstoves by emissions, efficiency, safety, durability, *and
> affordability* *while
> allowing for differences in local conditions and user behavior.* Although
> the standards could take a variety of forms, *one mechanism that is
> currently being explored* is the establishment of international standards
> through the International Standards Organization. *Such an international
> consultative process will take time (perhaps as long as three years*), so
> in the near-term the sector should develop an interim tiered rating system
> to be used while a voluntary global standard is in formal development"
> (emphasis added)
>
>
> Three years have passed. In another three years, GACC is scheduled to fold.
> What has boiling water done for TC-285 along the lines of
> "affordability while allowing for differences in local conditions and user
> behavior?"
>
> I rest my case. TC-285 was invented to have an excuse for wasting time and
> money - to create an appearance that something useful was being done, while
> an "interim tiered rating system" using WBT was forced upon anybody who was
> gullible enough or afraid of offending Secretary Clinton.
>
> TC-285 has zero relevance and should be disbanded. Maybe that would happen
> when EPA funds for GACC and ANSI run out. Mere WBT and arguing about DE is
> a red herring.
>
>
> Nikhil
>
>
> On Sat, Dec 9, 2017 at 12:21 AM, Ronal W. Larson <
> rongretlarson at comcast.net>
> wrote:
>
> > Xavier, list and ccs
> >
> > I guess (being the only individual named) I have to take up the
> > challenge. This is no fun. I respond because I find your position on
> the
> > WBT to be devoid of value. I apologize for trying to get this out on the
> > day you sent it - and it is late.
> >
> > My evidence on the validity of the present WBT (especially including the
> > ?denominator equation? - ?DE? = e1/(1-e2) is below in several parts.
> If
> > you respond, please refer to my numbered points, so we can best
> understand
> > your reasoning.
> >
> > Part I- the WBT and DE
> > a. There are hundreds of articles using the WBT, with no issue of its
> > validity. Those that don?t use the DE also assume there is no char
> worth
> > keeping track of. I don?t see how that can be a valid reason for not
> using
> > a DE (and I think they all national stove documents use something like a
> > WBT).
> > b. I know of no article in a peer-reviewed technical journal that gives
> a
> > rationale for WBT or DE?s discontinuation. The topic seems unique to
> this
> > list
> > c. Working group 2 of the of the ongoing ISO TC-285 process recently
> > voted overwhelmingly to retain the ?DE?. I am not aware of even
> > unpublished critiques that make sense (and I ask for such to be part of
> > your response).
> > d. Working group #1 had a very small group ( I?ve heard 7?) carry a
> > virtual tie in saying that the DE should be removed. Last night, WG#1?s
> > leader, Professor Tami Bond said I (nd others) could forward an
> > explanatory private memo. Others can forward more, but I think these
> > sentences are important re the WBT and DE
> > "*There is a current draft in Working Group 2 regarding controlled
> > laboratory testing (it has a formal name that I can?t remember). Its
> > product is under revision after responding to comments from national
> > standard bodies, and has not been published yet. Some of its features
> have
> > received some of the same criticisms as were provided on the WBT that is
> in
> > wide public use, yet other contents are different, as happens through
> > discussion.?*
> > Dr. Bond is not here arguing for removal of the DE, but (unfortunately)
> > there will be some confusion because of a very small number who are
> > misinformed about the DE and voted in an irrational position that has
> benn
> > rebutted by the vast majority of those involved in this ISO process.
> > e. I say misinformed because both Professor Phillip Lloyd and Crispin
> > showed a few months ago they did not know how to use the DE, (Dr. Lloyd
> > pulled an arbitrary number out of the air in his use of the equation).
> > f. It is argued (by those especially who don?t have one) that stove
> > testing laboratories (the main users of the WBT) are unnecessary. They
> > mostly also seem to couple the WBT with un-needed procedures for CO and
> > particulates (because they don?t believe widely reported health
> > statistics). I say they are valid because they are so widely used.
> Often
> > used to save governments money (unhealthy citizens are drains on national
> > economies). These rejections of the utility of pollutant measurements
> are
> > almost identical to efforts to downplay climate impacts - caused by
> > pollutants.
> > g. Something like the WBT is used virtually everywhere. The only places
> > where I believe the DE is not used is where they have not considered
> > char-making to be possible or intelligent or some other unfathomable
> > reason. I challenge anyone who believes cha-making has the least bit of
> > value to give some other means for bringing char-making into the
> valuation
> > of a stove.
> >
> > Part II. Tiers Turning to use of the DE as used in the tier
> > structures (and I believe this is the main beef of those opposed to the
> WBT)
> > a. It is true that I argue for the WBT because char-making stoves turn
> > out well using the DE. Exceedingly well. It seems that those who argue
> > against the WBT and DE are associated with stoves that don?t do as well.
> > b. I do so now for climate reasons (earlier for forest preservation,
> > health, time-saving and money-making reasons). My experience on this
> list
> > is that a large majority of those who put down the WBT and the DE have
> zero
> > concern about the climate impacts of inefficient and polluting stoves
> (and
> > especially charcoal-using stoves). Such beliefs lack appreciation of
> > climate science; those persons must also have other motives - probably
> > money related.
> > c. I claim the Part I arguments justify its use and I am convinced the
> DE
> > is totally valid (and can only be obtained through a WBT. So I ask all
> who
> > respond to this to propose a better means of helping advance stove
> > performance than the tier approach with its present use of the DE
> results.
> > If not tiers, what?
> > d. This list has finally had this week a TLUD story from Bangladesh that
> > fully justifies use of the WBT and DE. If the DE was dropped from the
> tier
> > system (as some on this list have proposed), then the work of Julien and
> > his collaborators would be much delayed. To the disadvantage of those
> > finding a new source of added income.
> >
> > It?s late. I may have to add more - on Lima for instance.
> >
> > Ron
> >
> >
> >
> > On Dec 8, 2017, at 2:54 PM, Xavier Brandao <xav.brandao at gmail.com>
> wrote:
> >
> >
> > Hello Frank,
> >
> > Ahah, there is indeed a pattern, you might have noticed it is usually the
> > following:
> > 1. Someone, usually Ron or a member of the GACC, EPA, Aprovecho, D-Lab
> > or Winrock, innocently drops ? WBT is a great protocol to make stove
> > improvements ? or ? you know, there are many supporters of the WBT ?,
> > somewhere in a post, a handbook or a toolkit
> > 2. Then, some of us howls in indignation, especially me. I start to rant
> > and sound like a broken record. Then I hand over, once again, the pile of
> > evidence, and ask some very simple straightforward questions.
> > 3. Suddenly the one in 1. very kindly tells me, in a
> > ? ho-it-would-be-so-great-to-have-you-there ? fashion, to:
> > a. Join the ISO-TC 285 discussions
> > b. Join a certain conference in the United States
> > c. Or becomes suddenly completely mute
> > Often it is a., b. then c.
> > 4. Then a few months pass by, and one beautiful day, we are back to step
> > 1.
> >
> > At this point it?s not a rabbit hole, it?s more like a rabbit loop, a
> > rabbit loophole.
> >
> > Best,
> >
> > Xavier
> >
> >
> >
> > -----Message d'origine-----
> > De : Stoves [mailto:stoves-bounces at lists.bioenergylists.org
> > <stoves-bounces at lists.bioenergylists.org>] De la part de
> franke at cruzio.com
> > Envoy? : jeudi 7 d?cembre 2017 21:56
> > ? : ndesai at alum.mit.edu
> > Cc : Crispin Pemberton-Pigott; Discussion of biomass cooking stoves
> > Objet : Re: [Stoves] Going back to 3-Stone Fire [Was Re: China and
> > cookstoves]
> >
> >
> > Dear Nikhil, Stovers,
> >
> > Always great news when we start a new year talking WBT. That because it
> > means we are not still down some rabbit hole someone has sent us to
> wallow
> > around for a few years on some useless idea only to come to the surface
> and
> > find us where we started (NOWHERE). But now starting at NOWHERE we must
> be
> > careful we are not diverted down another rabbit hole. Make sure all
> project
> > proposals involve the 6-Box system or parts of it. That involves both
> Field
> > and Lab work. Because that is the only way we get control over the
> > variables and move forward. A lot of work needs be done.
> >
> > Regards
> > Frank Shields
> > Gabilan Laboratory
> >
> >
> > <https://www.avast.com/sig-email?utm_medium=email&utm_
> source=link&utm_campaign=sig-email&utm_content=emailclient> Garanti
> > sans virus. www.avast.com
> > <https://www.avast.com/sig-email?utm_medium=email&utm_
> source=link&utm_campaign=sig-email&utm_content=emailclient>
> > _______________________________________________
> > Stoves mailing list
> >
> > to Send a Message to the list, use the email address
> > stoves at lists.bioenergylists.org
> >
> > to UNSUBSCRIBE or Change your List Settings use the web page
> > http://lists.bioenergylists.org/mailman/listinfo/stoves_
> > lists.bioenergylists.org
> >
> > for more Biomass Cooking Stoves, News and Information see our web site:
> > http://stoves.bioenergylists.org/
> >
> >
> >
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> ------------------------------
>
> Message: 15
> Date: Sun, 10 Dec 2017 16:04:38 +0000
> From: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
> To: Gordon West <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID:
> <MWHPR22MB078436EEE94AD32D71A75B2BB1360 at MWHPR22MB0784.
> namprd22.prod.outlook.com>
>
> Content-Type: text/plain; charset="windows-1256"
>
> Dear gordon
>
> You almost nailed it. Heating some small portion of the biomass and the
> temperature of the nearby fuel (not all of it) is sufficient to ignite a
> reaction that can continue indefinitely provided there is sufficient
> insulation and the oxygen content of the fuel is sufficient.
>
> There are two approaches that will work, as I understand it: the first is
> the charring of underground biomass (or coal) in the absence of additional
> oxygen. Once started, it will continue until the fuel is exhausted.
>
> The other does not require heating, but uses compressed air (oxygen) to
> provide the necessary reaction oxygen rapidly enough to get the reaction to
> continue (the Hawaiian invention).
>
> An MPF is the front at which the heat releasing reaction takes place.
>
> You can also consider the way char is formed. In the initial stage the
> energy needed to drive off the endothermic volatiles is more than the
> energy released by oxidizing the gases using only the oxygen available in
> the fuel. As the system heats up, the energy gap between evaporating
> volatiles and exothermic reactions decreases. At some point, the gap is
> small enough for the released oxygen to continue in the absence of
> additional air.
>
> TLUDs are in general too small to see this take place. They cool off too
> easily so additional air much be provided to sustain the reaction, which
> burns the rest of the hydrogen and at least some of the carbon.
>
> An underground fire can continue for centuries. All it has to do is get
> started. Prof Lloyd can explain how these fires can even auto-ignite. You
> have probably heard of stacks of hay setting themselves on fire by
> decomposition of the material in a large enough pile to retain the heat.
> Once it reaches or exceeds about 290 C the reactions are exothermic and
> from there it is a short trip to charging temperatures. The whole haystack
> can turn to char save the cool exterior.
>
> Burning coal seams manufacture their own oxygen from water. Coal doesn't
> have enough oxygen to sustain a pyrolytic front unless it is really hot.
> But burn they do.
>
> You can determine if there is an MPF but putting in a set of thermocouples
> and watching the front pass by. A burning log in an open fire has an MPF
> inside working it's way to the centre. The whole log will be charred long
> before it splits open.
>
> The interesting thing about a packed bed gasifier is that it can make gas
> predictably and controllable from ?small sized fuel generally considered a
> waste material. It is no small achievement.
>
> Regards
> Crispin
>
>
> I took a look at the Adams Retort design and watched a few videos. A
> couple of questions come to mind:
>
> 1) How does one determine that an MPF exists in an A-R?
>
> 2) I am not much of a chemist, but I would be interested to see an
> explanation of the reaction sequence where O2 is released and then burned
> in the MPF of an Adams Retort.
>
> It seems to me that if the external heat source is raising the temperature
> to the gasification point of the volatile components, thereby causing
> gasification (duh?), what purpose is the MPF serving?
>
> In a TLUD the MPF is burning some of the volatile gases to generate the
> heat needed to gasify un-pyrolyzed biomass.
>
> Gordon
>
>
>
> On Dec 9, 2017, at 10:54 PM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com<mailto:crispinpigott at outlook.com>> wrote:
>
> Dear Paul
>
> >Some of what you wrote is correct, but you go too far or leave out some
> important distinctions, thereby implying that some things are equal, that
> is, some are not really as worthy and distinctive as others (Ron and Paul)
> have stated.
>
> Of course there were things left out. I am happy you included below
> further refinements to the explanation.
>
> >1. Pyrolysis progresses (migrates) through a piece or pile of biomass as
> heat is able to penetrate. True. The Adam retort (and other retorts)
> heat the biomass from many sides, but there is no flame (actual combustion)
> inside. It is a stretch of language to say that the pyrolysis in the retort
> >>has an MPF [migrating pyrolytic front] proceeding in a roughly
> horizontal direction.
>
> Au contraire. The Adam Retort (which heats the biomass from under a
> portion of the bottom of the pile, not multiple sides) does indeed have a
> MPF and the combustion is fed by oxidation using oxygen liberated by the
> thermal decomposition of the fuel. There is no added oxygen, but oxygen
> there definitely is. There is enough oxygen in biomass to almost completely
> combust the hydrogen content. In practise the carbon and hydrogen are both
> involved in sustaining the MPF. Once the fuel is hot enough, the MPF can
> move through the pile without any additional heat required.
>
> >Sorry, that should say "has external heating proceeding inward from
> several directions from the sides toward the center."
>
> That is an incorrect description of the Adam Retort. There are retorts
> that function in the manner you describe. His is not one of them.
>
> >Furthermore, the processes in a retort are in sequential order during
> numerous minutes to 1) heat virtually all of the biomass to drive off the
> moisture, then 2) add more heat to virtually all of the biomass to drive
> off the low-temperature volatiles to create torrified material, and than 3)
> to finally get the temperature hot enough to have actual pryrolysis, first
> in the 400 deg C range and then at higher temperatures if the external
> heating is continued.
>
> That is true for some retorts, not the Adams Retort.
>
> >In sharp contrast, in a TLUD there is a distinctive zone of a few cm
> depth with actual small amounts of combustion (of some of the initial
> offgases). That zone migrates through the pile of biomass, heating mainly
> by radiation a small layer of biomass below the MPF, then with pyrolysis
> at a rather uniform temperature (generally from 450 to 700 C, depending on
> USER CONTROLED [sic] flow of primary air) to create the char as the gases
> move upward.
>
> The same also happens in a downdraft pyrolyser, and a bottom-pit updraft
> pyrolyser such as those produce by Hirendra Chakrabarti in India.
>
> The addition of a control feature makes the process variable, however it
> does not fundamentally change how the system works.
>
> >You may choose to try to equate the two descriptions above, but that
> would diminish your credibility as a precision-seeking scientist.
>
> There is no need for that kind of talk. First familiarise yourself with
> the systems under discussion. Seen from the side, an Adam Retort starts the
> MPF on the bottom right and it moves over a period of about 2 hours to the
> top left. Prof Lloyd can provide examples of sustained MPF?s moving
> horizontally underground in the Witbank area of South Africa without any
> addition of primary air. There are conditions where primary is required,
> and others when it is not. Tiny stoves require it.
>
> >And to equate a smouldering tree stump to MPF is a stretch beyond a
> stretch. Yes, there is fire there, and yes there is pyrolysis occuring.
> But such comparison is akin to saying that a ladybug and a moose are the
> same because both are living creatures; and in fact both are animals.
> Even a petunia and a whale are both living organisms. Scientific
> comparisons need precision and detail.
>
> That is why the discussion is on principles not ladybugs. A dry tree stump
> can be ignited to char the stump and the roots underground, and in the
> 1800?s one could buy a kit for doing so. I was told of a different method
> when I was young involving a steel pipe and kerosene. The point was to get
> the stump hot enough so that the pyrolysis would continue into the ground.
> The TLUD stove with an MPF is no more than a containerised version with
> controllable primary air.
>
> 2. Ron correctly pointed out that in normal operation of TLUD stoves,
> there is zero O2 that gets past the MPF. That is vastly different from
> having so much primary air enter (as in Rocket stoves and other burners)
> that there is O2 moving upward above the fuel (where the gases were
> created).
>
> Ron is correct about the O2. It is indeed different (I don?t know about
> ?vastly? from stoves where the fuel and flames are ?attached? to the solid
> fuel and the gases oxidise as and when they can. it is also true (but I
> didn?t expound on it) that within a fuel bed there are zones without no
> available O2, just as in the zone above the char.
>
> >You are saying that is good as preheated secondary O2.
>
> Functionally that is secondary air provided simultaneously, at least in
> some cases. My definitions are general cases and can be applied to the
> situation you describe.
>
> >Maybe, but not really. It is simply inadequate combustion, with the
> results of undesirable emissions.
>
> That is speculation and cannot be true in all cases.
>
> >The excessive primary air (which you state should be secondary air)...
>
> Which I state has the function of providing secondary air?
>
> >?has had a cooling effect on the raw fuel that the combustion is trying
> to get hot enough to give off the pyrolytic gases.
>
> That is not a general case. It could happen.
>
> >In other words, that secondary air that has passed over the fuel is part
> of the problem, not part of a solution because it has taken heat away from
> the fuel.
>
> That is not the case. What ?problem?? Heat passed through a metal wall to
> secondary air is not ?different heat? from that gained by air passing
> through a fuel bed, or along a hot combustion chamber wall. There are many
> roads to Rome. Air that is consumed after preheating is indifferent to hwo
> the heat was gained.
>
> >3. Tertiary air: Defined as either 1) the needed secondary air that
> did not get into the combustion zone soon enough (meaning that there was
> poor stove design)
>
> I see this as inaccurate on two counts: 1) the secondary air may be added
> in a way that decomposes complex gases further before final combustion, and
> 2) the bit about poor design is unfair comment. There are many good designs
> you may not know about.
>
> >?or 2) excess air that will lower the temperature of the hot gases
> (meaning that this "tertiary air" was NOT needed nor part of the combustion
> process).
>
> Tertiary air may be provided for a number of reasons, but normally to
> provide the oxygen needed to complete combustion with a desirable level of
> free O2 in the gases. Under certain circumstances, for example natural gas
> boilers, the level of free O2 is very low (1% by volume). To maintain such
> a low level of excess air it may be necessary to have tertiary or even more
> air injection points.
>
> >Either way, the concept of "tertiary air" is bogus in the context of
> cookstove combustion.
>
> That is opinion only, contradicted by existing technologies that use it.
> One of the highest performing stick-burning stoves available has tertiary
> air injection ? the Rocketworks stoves from Adrian Padt in Durban, tens of
> thousands of which are sold each year.
>
> >The objective is to get the combustion to be complete with the proper
> amounts of primary and secondary air at the correct times and places.
>
> That is true in some cases and not in others. Most Rocket stoves (per
> Aprovecho design guides) have only a single air entrance. The Rocketworks
> stoves have three distinct times and places.
>
> >4. You wrote:
> >>This [MPF} process is ... how the Terra Preta soils in the Amazon were
> created over 20,000 years of slash and burn agriculture.
> >The origins of Terra Preta are still being debated by the experts in that
> field, which is certainly not your claimed field of expertise.
>
> I am sorry to hear you talk about ?fields of expertise?. Facts in evidence
> speak for themselves and are not invalidated by any messenger claims.
>
> >>The Amerindians cultivated land that was already productive, they did
> not create it de novo. Cecil confirms they farm patches of land that are
> already productive, not random areas. He observed this when he was doing
> PhD field research while at Harvard.
>
> >I have great respect for Cecil Cook. But somehow what you have
> attributed to him and his work has not reach my attention previously.
>
> So what?
>
> >And I do not accept your statements.
>
> I don?t care. I cared to know, by interviewing him, how the Amerindians
> farmed and what role char had in their agriculture. I reported this
> previously to this list. Maybe you forgot. It is in the archives. At the
> time Ron replied that did didn?t accept the observational reports from
> Cecil who lived in the jungle for 4 years learning how their agricultural
> society functions.
>
> >What happened thousands of years ago was not witnessed by Cecil. He
> could only observe the current day activities on lands that somehow became
> fertile.
>
> He reported observations, the most important of which is that they do not
> practise slash and burn farming over whole areas, but only the fertile
> bits. The practice of slash and burning creates a lot of char in the
> ground, something contested by Ron at that time and diminished by your
> message regarding the tree stumps burning in California. If you don?t
> believe me, you can visit the area right now and witness the MPFs moving
> into the ground to charcoal the root systems. A major part of the work of
> firefighters is extinguishing these MPFs. This is sufficient to convince me
> they exist. If they exist, they are producing biochar in the ground.
>
> >You can take that topic to the Biochar Listserv, if you want to discuss
> it further.
>
> I have no interest in discussions on another list. I receive information
> from the Biochar-Ontario group.
>
> >Sorry, I reject much of what you wrote.
>
> Don?t be sorry. Learn and be happy! We are sharing perspectives here.
>
> >I would not want you to be instructing people about TLUD stoves and char
> making and Terra Preta.
>
> That is none of your business over which you have no control.
>
> >IMHO, your comments about pyrolysis in different devices reflect poorly
> on your credibikity [sic] regarding your other strongly expressed
> positions, but that is a topic for others to discuss.
>
> And I feel sometimes you could learn a thing or two before posting
> comments about other technologies. Like everyone else, I find your
> contributions worthy and partially correct.
>
> Perhaps there is something you could answer: Is there something about char
> making that requires or drives their proponents to make completely
> unnecessary personal attacks and derisive, inaccurate speculations about
> motives? Outside the agricultural sector and the production of
> char-enhanced fertilisers, I find the biochar enthusiasts as a group to be
> cloistered and fanatical, frequently engaging in divisive speech about
> something they have recently discovered.
>
> I should take a minute to compliment you, Xavier, Julien, Jonas Haller and
> Dr Nurhuda for being very open to exchange with me advice, explanations and
> observations without reservations about how or where the information
> originates. All of you have produced very interesting and effective
> products suited to certain communities.
>
> Best regards for a better burn
> Crispin
>
> _______________________________________________
> Stoves mailing list
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> ------------------------------
>
> Message: 16
> Date: Sun, 10 Dec 2017 09:11:16 -0700
> From: Gordon West <gordon.west at rtnewmexico.com>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID: <C5B482ED-656A-4162-86ED-07CB568C644C at rtnewmexico.com>
> Content-Type: text/plain; charset="utf-8"
>
> BTW, the ?duh? was a comment directed at myself for saying the same thing
> twice in one sentence! Not a jab at anyone...
>
> Gordon
>
>
>
> > On Dec 10, 2017, at 8:32 AM, Gordon West <gordon.west at rtnewmexico.com>
> wrote:
> >
> > I took a look at the Adams Retort design and watched a few videos. A
> couple of questions come to mind:
> >
> > 1) How does one determine that an MPF exists in an A-R?
> >
> > 2) I am not much of a chemist, but I would be interested to see an
> explanation of the reaction sequence where O2 is released and then burned
> in the MPF of an Adams Retort.
> >
> > It seems to me that if the external heat source is raising the
> temperature to the gasification point of the volatile components, thereby
> causing gasification (duh?), what purpose is the MPF serving?
> >
> > In a TLUD the MPF is burning some of the volatile gases to generate the
> heat needed to gasify un-pyrolyzed biomass.
> >
> > Gordon
> >
> >
> >
> >> On Dec 9, 2017, at 10:54 PM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com <mailto:crispinpigott at outlook.com>> wrote:
> >>
> >> Dear Paul
> >>
> >> >Some of what you wrote is correct, but you go too far or leave out
> some important distinctions, thereby implying that some things are equal,
> that is, some are not really as worthy and distinctive as others (Ron and
> Paul) have stated.
> >>
> >> Of course there were things left out. I am happy you included below
> further refinements to the explanation.
> >>
> >> >1. Pyrolysis progresses (migrates) through a piece or pile of biomass
> as heat is able to penetrate. True. The Adam retort (and other retorts)
> heat the biomass from many sides, but there is no flame (actual combustion)
> inside. It is a stretch of language to say that the pyrolysis in the retort
> >> >>has an MPF [migrating pyrolytic front] proceeding in a roughly
> horizontal direction.
> >>
> >> Au contraire. The Adam Retort (which heats the biomass from under a
> portion of the bottom of the pile, not multiple sides) does indeed have a
> MPF and the combustion is fed by oxidation using oxygen liberated by the
> thermal decomposition of the fuel. There is no added oxygen, but oxygen
> there definitely is. There is enough oxygen in biomass to almost completely
> combust the hydrogen content. In practise the carbon and hydrogen are both
> involved in sustaining the MPF. Once the fuel is hot enough, the MPF can
> move through the pile without any additional heat required.
> >>
> >> >Sorry, that should say "has external heating proceeding inward from
> several directions from the sides toward the center."
> >>
> >> That is an incorrect description of the Adam Retort. There are retorts
> that function in the manner you describe. His is not one of them.
> >>
> >> >Furthermore, the processes in a retort are in sequential order during
> numerous minutes to 1) heat virtually all of the biomass to drive off the
> moisture, then 2) add more heat to virtually all of the biomass to drive
> off the low-temperature volatiles to create torrified material, and than 3)
> to finally get the temperature hot enough to have actual pryrolysis, first
> in the 400 deg C range and then at higher temperatures if the external
> heating is continued.
> >>
> >> That is true for some retorts, not the Adams Retort.
> >>
> >> >In sharp contrast, in a TLUD there is a distinctive zone of a few cm
> depth with actual small amounts of combustion (of some of the initial
> offgases). That zone migrates through the pile of biomass, heating mainly
> by radiation a small layer of biomass below the MPF, then with pyrolysis
> at a rather uniform temperature (generally from 450 to 700 C, depending on
> USER CONTROLED [sic] flow of primary air) to create the char as the gases
> move upward.
> >>
> >> The same also happens in a downdraft pyrolyser, and a bottom-pit
> updraft pyrolyser such as those produce by Hirendra Chakrabarti in India.
> >>
> >> The addition of a control feature makes the process variable, however
> it does not fundamentally change how the system works.
> >>
> >> >You may choose to try to equate the two descriptions above, but that
> would diminish your credibility as a precision-seeking scientist.
> >>
> >> There is no need for that kind of talk. First familiarise yourself with
> the systems under discussion. Seen from the side, an Adam Retort starts the
> MPF on the bottom right and it moves over a period of about 2 hours to the
> top left. Prof Lloyd can provide examples of sustained MPF?s moving
> horizontally underground in the Witbank area of South Africa without any
> addition of primary air. There are conditions where primary is required,
> and others when it is not. Tiny stoves require it.
> >>
> >> >And to equate a smouldering tree stump to MPF is a stretch beyond a
> stretch. Yes, there is fire there, and yes there is pyrolysis occuring.
> But such comparison is akin to saying that a ladybug and a moose are the
> same because both are living creatures; and in fact both are animals.
> Even a petunia and a whale are both living organisms. Scientific
> comparisons need precision and detail.
> >>
> >> That is why the discussion is on principles not ladybugs. A dry tree
> stump can be ignited to char the stump and the roots underground, and in
> the 1800?s one could buy a kit for doing so. I was told of a different
> method when I was young involving a steel pipe and kerosene. The point was
> to get the stump hot enough so that the pyrolysis would continue into the
> ground. The TLUD stove with an MPF is no more than a containerised version
> with controllable primary air.
> >>
> >> 2. Ron correctly pointed out that in normal operation of TLUD stoves,
> there is zero O2 that gets past the MPF. That is vastly different from
> having so much primary air enter (as in Rocket stoves and other burners)
> that there is O2 moving upward above the fuel (where the gases were
> created).
> >>
> >> Ron is correct about the O2. It is indeed different (I don?t know about
> ?vastly? from stoves where the fuel and flames are ?attached? to the solid
> fuel and the gases oxidise as and when they can. it is also true (but I
> didn?t expound on it) that within a fuel bed there are zones without no
> available O2, just as in the zone above the char.
> >>
> >> >You are saying that is good as preheated secondary O2.
> >>
> >> Functionally that is secondary air provided simultaneously, at least in
> some cases. My definitions are general cases and can be applied to the
> situation you describe.
> >>
> >> >Maybe, but not really. It is simply inadequate combustion, with the
> results of undesirable emissions.
> >>
> >> That is speculation and cannot be true in all cases.
> >>
> >> >The excessive primary air (which you state should be secondary air)...
> >>
> >> Which I state has the function of providing secondary air?
> >>
> >> >?has had a cooling effect on the raw fuel that the combustion is
> trying to get hot enough to give off the pyrolytic gases.
> >>
> >> That is not a general case. It could happen.
> >>
> >> >In other words, that secondary air that has passed over the fuel is
> part of the problem, not part of a solution because it has taken heat away
> from the fuel.
> >>
> >> That is not the case. What ?problem?? Heat passed through a metal wall
> to secondary air is not ?different heat? from that gained by air passing
> through a fuel bed, or along a hot combustion chamber wall. There are many
> roads to Rome. Air that is consumed after preheating is indifferent to hwo
> the heat was gained.
> >>
> >> >3. Tertiary air: Defined as either 1) the needed secondary air that
> did not get into the combustion zone soon enough (meaning that there was
> poor stove design)
> >>
> >> I see this as inaccurate on two counts: 1) the secondary air may be
> added in a way that decomposes complex gases further before final
> combustion, and 2) the bit about poor design is unfair comment. There are
> many good designs you may not know about.
> >>
> >> >?or 2) excess air that will lower the temperature of the hot gases
> (meaning that this "tertiary air" was NOT needed nor part of the combustion
> process).
> >>
> >> Tertiary air may be provided for a number of reasons, but normally to
> provide the oxygen needed to complete combustion with a desirable level of
> free O2 in the gases. Under certain circumstances, for example natural gas
> boilers, the level of free O2 is very low (1% by volume). To maintain such
> a low level of excess air it may be necessary to have tertiary or even more
> air injection points.
> >>
> >> >Either way, the concept of "tertiary air" is bogus in the context of
> cookstove combustion.
> >>
> >> That is opinion only, contradicted by existing technologies that use
> it. One of the highest performing stick-burning stoves available has
> tertiary air injection ? the Rocketworks stoves from Adrian Padt in Durban,
> tens of thousands of which are sold each year.
> >>
> >> >The objective is to get the combustion to be complete with the proper
> amounts of primary and secondary air at the correct times and places.
> >>
> >> That is true in some cases and not in others. Most Rocket stoves (per
> Aprovecho design guides) have only a single air entrance. The Rocketworks
> stoves have three distinct times and places.
> >>
> >> >4. You wrote:
> >> >>This [MPF} process is ... how the Terra Preta soils in the Amazon
> were created over 20,000 years of slash and burn agriculture.
> >> >The origins of Terra Preta are still being debated by the experts in
> that field, which is certainly not your claimed field of expertise.
> >>
> >> I am sorry to hear you talk about ?fields of expertise?. Facts in
> evidence speak for themselves and are not invalidated by any messenger
> claims.
> >>
> >> >>The Amerindians cultivated land that was already productive, they did
> not create it de novo. Cecil confirms they farm patches of land that are
> already productive, not random areas. He observed this when he was doing
> PhD field research while at Harvard.
> >>
> >> >I have great respect for Cecil Cook. But somehow what you have
> attributed to him and his work has not reach my attention previously.
> >>
> >> So what?
> >>
> >> >And I do not accept your statements.
> >>
> >> I don?t care. I cared to know, by interviewing him, how the Amerindians
> farmed and what role char had in their agriculture. I reported this
> previously to this list. Maybe you forgot. It is in the archives. At the
> time Ron replied that did didn?t accept the observational reports from
> Cecil who lived in the jungle for 4 years learning how their agricultural
> society functions.
> >>
> >> >What happened thousands of years ago was not witnessed by Cecil. He
> could only observe the current day activities on lands that somehow became
> fertile.
> >>
> >> He reported observations, the most important of which is that they do
> not practise slash and burn farming over whole areas, but only the fertile
> bits. The practice of slash and burning creates a lot of char in the
> ground, something contested by Ron at that time and diminished by your
> message regarding the tree stumps burning in California. If you don?t
> believe me, you can visit the area right now and witness the MPFs moving
> into the ground to charcoal the root systems. A major part of the work of
> firefighters is extinguishing these MPFs. This is sufficient to convince me
> they exist. If they exist, they are producing biochar in the ground.
> >>
> >> >You can take that topic to the Biochar Listserv, if you want to
> discuss it further.
> >>
> >> I have no interest in discussions on another list. I receive
> information from the Biochar-Ontario group.
> >>
> >> >Sorry, I reject much of what you wrote.
> >>
> >> Don?t be sorry. Learn and be happy! We are sharing perspectives here.
> >>
> >> >I would not want you to be instructing people about TLUD stoves and
> char making and Terra Preta.
> >>
> >> That is none of your business over which you have no control.
> >>
> >> >IMHO, your comments about pyrolysis in different devices reflect
> poorly on your credibikity [sic] regarding your other strongly expressed
> positions, but that is a topic for others to discuss.
> >>
> >> And I feel sometimes you could learn a thing or two before posting
> comments about other technologies. Like everyone else, I find your
> contributions worthy and partially correct.
> >>
> >> Perhaps there is something you could answer: Is there something about
> char making that requires or drives their proponents to make completely
> unnecessary personal attacks and derisive, inaccurate speculations about
> motives? Outside the agricultural sector and the production of
> char-enhanced fertilisers, I find the biochar enthusiasts as a group to be
> cloistered and fanatical, frequently engaging in divisive speech about
> something they have recently discovered.
> >>
> >> I should take a minute to compliment you, Xavier, Julien, Jonas Haller
> and Dr Nurhuda for being very open to exchange with me advice, explanations
> and observations without reservations about how or where the information
> originates. All of you have produced very interesting and effective
> products suited to certain communities.
> >>
> >> Best regards for a better burn
> >> Crispin
> >>
> >> _______________________________________________
> >> Stoves mailing list
> >>
> >> to Send a Message to the list, use the email address
> >> stoves at lists.bioenergylists.org <mailto:stoves at lists.bioenergylists.org
> >
> >>
> >> to UNSUBSCRIBE or Change your List Settings use the web page
> >> http://lists.bioenergylists.org/mailman/listinfo/stoves_
> lists.bioenergylists.org <http://lists.bioenergylists.
> org/mailman/listinfo/stoves_lists.bioenergylists.org>
> >>
> >> for more Biomass Cooking Stoves, News and Information see our web site:
> >> http://stoves.bioenergylists.org/ <http://stoves.bioenergylists.org/>
> >>
> >
> > _______________________________________________
> > Stoves mailing list
> >
> > to Send a Message to the list, use the email address
> > stoves at lists.bioenergylists.org
> >
> > to UNSUBSCRIBE or Change your List Settings use the web page
> > http://lists.bioenergylists.org/mailman/listinfo/stoves_
> lists.bioenergylists.org
> >
> > for more Biomass Cooking Stoves, News and Information see our web site:
> > http://stoves.bioenergylists.org/
> >
>
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>
> ------------------------------
>
> Message: 17
> Date: Sun, 10 Dec 2017 16:15:05 +0000
> From: Scott Zager <scott.zager at wildlands.biz>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID:
> <CY4PR11MB1704837FE39CFD26D3AD0E5DFD360 at CY4PR11MB1704.
> namprd11.prod.outlook.com>
>
> Content-Type: text/plain; charset="utf-8"
>
> Oh I get it for sure now that you explain it.
>
> Try not to beat yourself up about it. That?s my job.
>
> From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf
> Of Gordon West
> Sent: Sunday, December 10, 2017 9:11 AM
> To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
>
> BTW, the ?duh? was a comment directed at myself for saying the same thing
> twice in one sentence! Not a jab at anyone...
>
> Gordon
>
>
>
> On Dec 10, 2017, at 8:32 AM, Gordon West <gordon.west at rtnewmexico.com<
> mailto:gordon.west at rtnewmexico.com>> wrote:
>
> I took a look at the Adams Retort design and watched a few videos. A
> couple of questions come to mind:
>
> 1) How does one determine that an MPF exists in an A-R?
>
> 2) I am not much of a chemist, but I would be interested to see an
> explanation of the reaction sequence where O2 is released and then burned
> in the MPF of an Adams Retort.
>
> It seems to me that if the external heat source is raising the temperature
> to the gasification point of the volatile components, thereby causing
> gasification (duh?), what purpose is the MPF serving?
>
> In a TLUD the MPF is burning some of the volatile gases to generate the
> heat needed to gasify un-pyrolyzed biomass.
>
> Gordon
>
>
>
> On Dec 9, 2017, at 10:54 PM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com<mailto:crispinpigott at outlook.com>> wrote:
>
> Dear Paul
>
> >Some of what you wrote is correct, but you go too far or leave out some
> important distinctions, thereby implying that some things are equal, that
> is, some are not really as worthy and distinctive as others (Ron and Paul)
> have stated.
>
> Of course there were things left out. I am happy you included below
> further refinements to the explanation.
>
> >1. Pyrolysis progresses (migrates) through a piece or pile of biomass as
> heat is able to penetrate. True. The Adam retort (and other retorts)
> heat the biomass from many sides, but there is no flame (actual combustion)
> inside. It is a stretch of language to say that the pyrolysis in the retort
> >>has an MPF [migrating pyrolytic front] proceeding in a roughly
> horizontal direction.
>
> Au contraire. The Adam Retort (which heats the biomass from under a
> portion of the bottom of the pile, not multiple sides) does indeed have a
> MPF and the combustion is fed by oxidation using oxygen liberated by the
> thermal decomposition of the fuel. There is no added oxygen, but oxygen
> there definitely is. There is enough oxygen in biomass to almost completely
> combust the hydrogen content. In practise the carbon and hydrogen are both
> involved in sustaining the MPF. Once the fuel is hot enough, the MPF can
> move through the pile without any additional heat required.
>
> >Sorry, that should say "has external heating proceeding inward from
> several directions from the sides toward the center."
>
> That is an incorrect description of the Adam Retort. There are retorts
> that function in the manner you describe. His is not one of them.
>
> >Furthermore, the processes in a retort are in sequential order during
> numerous minutes to 1) heat virtually all of the biomass to drive off the
> moisture, then 2) add more heat to virtually all of the biomass to drive
> off the low-temperature volatiles to create torrified material, and than 3)
> to finally get the temperature hot enough to have actual pryrolysis, first
> in the 400 deg C range and then at higher temperatures if the external
> heating is continued.
>
> That is true for some retorts, not the Adams Retort.
>
> >In sharp contrast, in a TLUD there is a distinctive zone of a few cm
> depth with actual small amounts of combustion (of some of the initial
> offgases). That zone migrates through the pile of biomass, heating mainly
> by radiation a small layer of biomass below the MPF, then with pyrolysis
> at a rather uniform temperature (generally from 450 to 700 C, depending on
> USER CONTROLED [sic] flow of primary air) to create the char as the gases
> move upward.
>
> The same also happens in a downdraft pyrolyser, and a bottom-pit updraft
> pyrolyser such as those produce by Hirendra Chakrabarti in India.
>
> The addition of a control feature makes the process variable, however it
> does not fundamentally change how the system works.
>
> >You may choose to try to equate the two descriptions above, but that
> would diminish your credibility as a precision-seeking scientist.
>
> There is no need for that kind of talk. First familiarise yourself with
> the systems under discussion. Seen from the side, an Adam Retort starts the
> MPF on the bottom right and it moves over a period of about 2 hours to the
> top left. Prof Lloyd can provide examples of sustained MPF?s moving
> horizontally underground in the Witbank area of South Africa without any
> addition of primary air. There are conditions where primary is required,
> and others when it is not. Tiny stoves require it.
>
> >And to equate a smouldering tree stump to MPF is a stretch beyond a
> stretch. Yes, there is fire there, and yes there is pyrolysis occuring.
> But such comparison is akin to saying that a ladybug and a moose are the
> same because both are living creatures; and in fact both are animals.
> Even a petunia and a whale are both living organisms. Scientific
> comparisons need precision and detail.
>
> That is why the discussion is on principles not ladybugs. A dry tree stump
> can be ignited to char the stump and the roots underground, and in the
> 1800?s one could buy a kit for doing so. I was told of a different method
> when I was young involving a steel pipe and kerosene. The point was to get
> the stump hot enough so that the pyrolysis would continue into the ground.
> The TLUD stove with an MPF is no more than a containerised version with
> controllable primary air.
>
> 2. Ron correctly pointed out that in normal operation of TLUD stoves,
> there is zero O2 that gets past the MPF. That is vastly different from
> having so much primary air enter (as in Rocket stoves and other burners)
> that there is O2 moving upward above the fuel (where the gases were
> created).
>
> Ron is correct about the O2. It is indeed different (I don?t know about
> ?vastly? from stoves where the fuel and flames are ?attached? to the solid
> fuel and the gases oxidise as and when they can. it is also true (but I
> didn?t expound on it) that within a fuel bed there are zones without no
> available O2, just as in the zone above the char.
>
> >You are saying that is good as preheated secondary O2.
>
> Functionally that is secondary air provided simultaneously, at least in
> some cases. My definitions are general cases and can be applied to the
> situation you describe.
>
> >Maybe, but not really. It is simply inadequate combustion, with the
> results of undesirable emissions.
>
> That is speculation and cannot be true in all cases.
>
> >The excessive primary air (which you state should be secondary air)...
>
> Which I state has the function of providing secondary air?
>
> >?has had a cooling effect on the raw fuel that the combustion is trying
> to get hot enough to give off the pyrolytic gases.
>
> That is not a general case. It could happen.
>
> >In other words, that secondary air that has passed over the fuel is part
> of the problem, not part of a solution because it has taken heat away from
> the fuel.
>
>
> That is not the case. What ?problem?? Heat passed through a metal wall to
> secondary air is not ?different heat? from that gained by air passing
> through a fuel bed, or along a hot combustion chamber wall. There are many
> roads to Rome. Air that is consumed after preheating is indifferent to hwo
> the heat was gained.
>
> >3. Tertiary air: Defined as either 1) the needed secondary air that
> did not get into the combustion zone soon enough (meaning that there was
> poor stove design)
>
> I see this as inaccurate on two counts: 1) the secondary air may be added
> in a way that decomposes complex gases further before final combustion, and
> 2) the bit about poor design is unfair comment. There are many good designs
> you may not know about.
>
> >?or 2) excess air that will lower the temperature of the hot gases
> (meaning that this "tertiary air" was NOT needed nor part of the combustion
> process).
>
> Tertiary air may be provided for a number of reasons, but normally to
> provide the oxygen needed to complete combustion with a desirable level of
> free O2 in the gases. Under certain circumstances, for example natural gas
> boilers, the level of free O2 is very low (1% by volume). To maintain such
> a low level of excess air it may be necessary to have tertiary or even more
> air injection points.
>
> >Either way, the concept of "tertiary air" is bogus in the context of
> cookstove combustion.
>
> That is opinion only, contradicted by existing technologies that use it.
> One of the highest performing stick-burning stoves available has tertiary
> air injection ? the Rocketworks stoves from Adrian Padt in Durban, tens of
> thousands of which are sold each year.
>
> >The objective is to get the combustion to be complete with the proper
> amounts of primary and secondary air at the correct times and places.
>
> That is true in some cases and not in others. Most Rocket stoves (per
> Aprovecho design guides) have only a single air entrance. The Rocketworks
> stoves have three distinct times and places.
>
> >4. You wrote:
> >>This [MPF} process is ... how the Terra Preta soils in the Amazon were
> created over 20,000 years of slash and burn agriculture.
> >The origins of Terra Preta are still being debated by the experts in that
> field, which is certainly not your claimed field of expertise.
>
> I am sorry to hear you talk about ?fields of expertise?. Facts in evidence
> speak for themselves and are not invalidated by any messenger claims.
>
> >>The Amerindians cultivated land that was already productive, they did
> not create it de novo. Cecil confirms they farm patches of land that are
> already productive, not random areas. He observed this when he was doing
> PhD field research while at Harvard.
>
>
> >I have great respect for Cecil Cook. But somehow what you have
> attributed to him and his work has not reach my attention previously.
>
> So what?
>
> >And I do not accept your statements.
>
> I don?t care. I cared to know, by interviewing him, how the Amerindians
> farmed and what role char had in their agriculture. I reported this
> previously to this list. Maybe you forgot. It is in the archives. At the
> time Ron replied that did didn?t accept the observational reports from
> Cecil who lived in the jungle for 4 years learning how their agricultural
> society functions.
>
> >What happened thousands of years ago was not witnessed by Cecil. He
> could only observe the current day activities on lands that somehow became
> fertile.
>
> He reported observations, the most important of which is that they do not
> practise slash and burn farming over whole areas, but only the fertile
> bits. The practice of slash and burning creates a lot of char in the
> ground, something contested by Ron at that time and diminished by your
> message regarding the tree stumps burning in California. If you don?t
> believe me, you can visit the area right now and witness the MPFs moving
> into the ground to charcoal the root systems. A major part of the work of
> firefighters is extinguishing these MPFs. This is sufficient to convince me
> they exist. If they exist, they are producing biochar in the ground.
>
> >You can take that topic to the Biochar Listserv, if you want to discuss
> it further.
>
> I have no interest in discussions on another list. I receive information
> from the Biochar-Ontario group.
>
> >Sorry, I reject much of what you wrote.
>
> Don?t be sorry. Learn and be happy! We are sharing perspectives here.
>
> >I would not want you to be instructing people about TLUD stoves and char
> making and Terra Preta.
>
> That is none of your business over which you have no control.
>
> >IMHO, your comments about pyrolysis in different devices reflect poorly
> on your credibikity [sic] regarding your other strongly expressed
> positions, but that is a topic for others to discuss.
>
> And I feel sometimes you could learn a thing or two before posting
> comments about other technologies. Like everyone else, I find your
> contributions worthy and partially correct.
>
> Perhaps there is something you could answer: Is there something about char
> making that requires or drives their proponents to make completely
> unnecessary personal attacks and derisive, inaccurate speculations about
> motives? Outside the agricultural sector and the production of
> char-enhanced fertilisers, I find the biochar enthusiasts as a group to be
> cloistered and fanatical, frequently engaging in divisive speech about
> something they have recently discovered.
>
> I should take a minute to compliment you, Xavier, Julien, Jonas Haller and
> Dr Nurhuda for being very open to exchange with me advice, explanations and
> observations without reservations about how or where the information
> originates. All of you have produced very interesting and effective
> products suited to certain communities.
>
> Best regards for a better burn
> Crispin
>
> _______________________________________________
> Stoves mailing list
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>
>
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> ------------------------------
>
> Message: 18
> Date: Sun, 10 Dec 2017 16:33:05 +0000
> From: Scott Zager <scott.zager at wildlands.biz>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID:
> <CY4PR11MB170496989C99097C749FD0A2FD360 at CY4PR11MB1704.
> namprd11.prod.outlook.com>
>
> Content-Type: text/plain; charset="windows-1255"
>
> Dear stovers:
> The recent discussion inspired me to amend a working definition I have
> been writing for a glossary on biochar. I was hoping that perhaps more
> experienced stovers would be willing to review my definition of a TLUD. I
> would appreciate any comments for revision. Thank you.
>
> P.S. I am trying to define a ?Retort? next.
> TLUD (top-lit, up-draft) Pyrolyzer: TLUD gasifiers automatically make char
> while producing combustible energy. A TLUD is basically a canister filled
> with biomass to create a ?fuel bed?. TLUDs are either batch-fed or
> continuously-fed, biomass gasifiers that are loaded with a feedstock
> (biomass in the form of wood chips, pellets, briquettes, etc.). Air enters
> the canister through holes in a grate at the bottom of the cylinder. The
> fuel bed is ignited on top, burning some of the volatile gases to generate
> the heat needed to gasify un-pyrolyzed feedstock. The ignition front
> travels down through the fuel by heat radiating into the raw fuel, which
> dries it and initiates thermochemical conversion of the feedstock into char
> and wood-gas. The "ignition front" is actually a pyrolysis reaction within
> the canister that moves through the feedstock, in what is called a
> "Migratory Pyrolytic Front" (MPF). The ignition front is maintained by air
> (i.e., primary air) that enters the bottom of the cylinder. Residual char
> is left on top of the fuel bed as the MPF moves downward. The MPF creates a
> draft for primary air, which can be also supplemented and controlled by
> forced air pushed inward from fans. When the MPF reaches the bottom of the
> cylinder, the smoke-producing reaction is complete, and pyrolysis ends. At
> this point the char is removed from the cylinder. If the char is not
> removed, it may burn slowly from the bottom up unless the fire is snuffed
> out by the lack of oxygen. During pyrolysis, volatile gasses in the form of
> white smoke (wood-gas) dissipate upwards into a secondary combustion
> chamber where it is consumed to produce heat and carbon dioxide (mostly).
> The gas flame in the secondary chamber is supported by air (secondary air)
> entering through side-holes or a gap near the top of the cylinder. The
> primary and secondary air can move by natural draft, relying on the
> buoyancy of hot gasses to push air through the system, or draft air can be
> forced ? and controlled ? by using a variable-speed, small electric fan to
> push the air. The pyrolysis leaves behind char rather than ash for two
> reasons: (1) as the MPF moves downwards, it thermochemically transforms
> new fuel at a rate faster than oxygen is supplied to combust it, and (2)
> pyrolysis and the combustion of volatiles can occur much faster than the
> combustion of char, which requires a higher level of activation energy.1
> Continuously-fed TLUDs use augers to maintain the MPF in a stationary
> position by supplying new feedstock into the bottom of the cylinder while
> removing char through an upward port into a quenching container that
> extinguishes any reactions, cools the char and stores it.
>
>
> From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf
> Of Crispin Pemberton-Pigott
> Sent: Sunday, December 10, 2017 9:05 AM
> To: Gordon West <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
>
> Dear gordon
>
> You almost nailed it. Heating some small portion of the biomass and the
> temperature of the nearby fuel (not all of it) is sufficient to ignite a
> reaction that can continue indefinitely provided there is sufficient
> insulation and the oxygen content of the fuel is sufficient.
>
> There are two approaches that will work, as I understand it: the first is
> the charring of underground biomass (or coal) in the absence of additional
> oxygen. Once started, it will continue until the fuel is exhausted.
>
> The other does not require heating, but uses compressed air (oxygen) to
> provide the necessary reaction oxygen rapidly enough to get the reaction to
> continue (the Hawaiian invention).
>
> An MPF is the front at which the heat releasing reaction takes place.
>
> You can also consider the way char is formed. In the initial stage the
> energy needed to drive off the endothermic volatiles is more than the
> energy released by oxidizing the gases using only the oxygen available in
> the fuel. As the system heats up, the energy gap between evaporating
> volatiles and exothermic reactions decreases. At some point, the gap is
> small enough for the released oxygen to continue in the absence of
> additional air.
>
> TLUDs are in general too small to see this take place. They cool off too
> easily so additional air much be provided to sustain the reaction, which
> burns the rest of the hydrogen and at least some of the carbon.
>
> An underground fire can continue for centuries. All it has to do is get
> started. Prof Lloyd can explain how these fires can even auto-ignite. You
> have probably heard of stacks of hay setting themselves on fire by
> decomposition of the material in a large enough pile to retain the heat.
> Once it reaches or exceeds about 290 C the reactions are exothermic and
> from there it is a short trip to charging temperatures. The whole haystack
> can turn to char save the cool exterior.
>
> Burning coal seams manufacture their own oxygen from water. Coal doesn't
> have enough oxygen to sustain a pyrolytic front unless it is really hot.
> But burn they do.
>
> You can determine if there is an MPF but putting in a set of thermocouples
> and watching the front pass by. A burning log in an open fire has an MPF
> inside working it's way to the centre. The whole log will be charred long
> before it splits open.
>
> The interesting thing about a packed bed gasifier is that it can make gas
> predictably and controllable from ?small sized fuel generally considered a
> waste material. It is no small achievement.
>
> Regards
> Crispin
>
>
> I took a look at the Adams Retort design and watched a few videos. A
> couple of questions come to mind:
>
> 1) How does one determine that an MPF exists in an A-R?
>
> 2) I am not much of a chemist, but I would be interested to see an
> explanation of the reaction sequence where O2 is released and then burned
> in the MPF of an Adams Retort.
>
> It seems to me that if the external heat source is raising the temperature
> to the gasification point of the volatile components, thereby causing
> gasification (duh?), what purpose is the MPF serving?
>
> In a TLUD the MPF is burning some of the volatile gases to generate the
> heat needed to gasify un-pyrolyzed biomass.
>
> Gordon
>
>
>
> On Dec 9, 2017, at 10:54 PM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com<mailto:crispinpigott at outlook.com>> wrote:
>
> Dear Paul
>
> >Some of what you wrote is correct, but you go too far or leave out some
> important distinctions, thereby implying that some things are equal, that
> is, some are not really as worthy and distinctive as others (Ron and Paul)
> have stated.
>
> Of course there were things left out. I am happy you included below
> further refinements to the explanation.
>
> >1. Pyrolysis progresses (migrates) through a piece or pile of biomass as
> heat is able to penetrate. True. The Adam retort (and other retorts)
> heat the biomass from many sides, but there is no flame (actual combustion)
> inside. It is a stretch of language to say that the pyrolysis in the retort
> >>has an MPF [migrating pyrolytic front] proceeding in a roughly
> horizontal direction.
>
> Au contraire. The Adam Retort (which heats the biomass from under a
> portion of the bottom of the pile, not multiple sides) does indeed have a
> MPF and the combustion is fed by oxidation using oxygen liberated by the
> thermal decomposition of the fuel. There is no added oxygen, but oxygen
> there definitely is. There is enough oxygen in biomass to almost completely
> combust the hydrogen content. In practise the carbon and hydrogen are both
> involved in sustaining the MPF. Once the fuel is hot enough, the MPF can
> move through the pile without any additional heat required.
>
> >Sorry, that should say "has external heating proceeding inward from
> several directions from the sides toward the center."
>
> That is an incorrect description of the Adam Retort. There are retorts
> that function in the manner you describe. His is not one of them.
>
> >Furthermore, the processes in a retort are in sequential order during
> numerous minutes to 1) heat virtually all of the biomass to drive off the
> moisture, then 2) add more heat to virtually all of the biomass to drive
> off the low-temperature volatiles to create torrified material, and than 3)
> to finally get the temperature hot enough to have actual pryrolysis, first
> in the 400 deg C range and then at higher temperatures if the external
> heating is continued.
>
> That is true for some retorts, not the Adams Retort.
>
> >In sharp contrast, in a TLUD there is a distinctive zone of a few cm
> depth with actual small amounts of combustion (of some of the initial
> offgases). That zone migrates through the pile of biomass, heating mainly
> by radiation a small layer of biomass below the MPF, then with pyrolysis
> at a rather uniform temperature (generally from 450 to 700 C, depending on
> USER CONTROLED [sic] flow of primary air) to create the char as the gases
> move upward.
>
> The same also happens in a downdraft pyrolyser, and a bottom-pit updraft
> pyrolyser such as those produce by Hirendra Chakrabarti in India.
>
> The addition of a control feature makes the process variable, however it
> does not fundamentally change how the system works.
>
> >You may choose to try to equate the two descriptions above, but that
> would diminish your credibility as a precision-seeking scientist.
>
> There is no need for that kind of talk. First familiarise yourself with
> the systems under discussion. Seen from the side, an Adam Retort starts the
> MPF on the bottom right and it moves over a period of about 2 hours to the
> top left. Prof Lloyd can provide examples of sustained MPF?s moving
> horizontally underground in the Witbank area of South Africa without any
> addition of primary air. There are conditions where primary is required,
> and others when it is not. Tiny stoves require it.
>
> >And to equate a smouldering tree stump to MPF is a stretch beyond a
> stretch. Yes, there is fire there, and yes there is pyrolysis occuring.
> But such comparison is akin to saying that a ladybug and a moose are the
> same because both are living creatures; and in fact both are animals.
> Even a petunia and a whale are both living organisms. Scientific
> comparisons need precision and detail.
>
> That is why the discussion is on principles not ladybugs. A dry tree stump
> can be ignited to char the stump and the roots underground, and in the
> 1800?s one could buy a kit for doing so. I was told of a different method
> when I was young involving a steel pipe and kerosene. The point was to get
> the stump hot enough so that the pyrolysis would continue into the ground.
> The TLUD stove with an MPF is no more than a containerised version with
> controllable primary air.
>
> 2. Ron correctly pointed out that in normal operation of TLUD stoves,
> there is zero O2 that gets past the MPF. That is vastly different from
> having so much primary air enter (as in Rocket stoves and other burners)
> that there is O2 moving upward above the fuel (where the gases were
> created).
>
> Ron is correct about the O2. It is indeed different (I don?t know about
> ?vastly? from stoves where the fuel and flames are ?attached? to the solid
> fuel and the gases oxidise as and when they can. it is also true (but I
> didn?t expound on it) that within a fuel bed there are zones without no
> available O2, just as in the zone above the char.
>
> >You are saying that is good as preheated secondary O2.
>
> Functionally that is secondary air provided simultaneously, at least in
> some cases. My definitions are general cases and can be applied to the
> situation you describe.
>
> >Maybe, but not really. It is simply inadequate combustion, with the
> results of undesirable emissions.
>
> That is speculation and cannot be true in all cases.
>
> >The excessive primary air (which you state should be secondary air)...
>
> Which I state has the function of providing secondary air?
>
> >?has had a cooling effect on the raw fuel that the combustion is trying
> to get hot enough to give off the pyrolytic gases.
>
> That is not a general case. It could happen.
>
> >In other words, that secondary air that has passed over the fuel is part
> of the problem, not part of a solution because it has taken heat away from
> the fuel.
> That is not the case. What ?problem?? Heat passed through a metal wall to
> secondary air is not ?different heat? from that gained by air passing
> through a fuel bed, or along a hot combustion chamber wall. There are many
> roads to Rome. Air that is consumed after preheating is indifferent to hwo
> the heat was gained.
>
> >3. Tertiary air: Defined as either 1) the needed secondary air that
> did not get into the combustion zone soon enough (meaning that there was
> poor stove design)
>
> I see this as inaccurate on two counts: 1) the secondary air may be added
> in a way that decomposes complex gases further before final combustion, and
> 2) the bit about poor design is unfair comment. There are many good designs
> you may not know about.
>
> >?or 2) excess air that will lower the temperature of the hot gases
> (meaning that this "tertiary air" was NOT needed nor part of the combustion
> process).
>
> Tertiary air may be provided for a number of reasons, but normally to
> provide the oxygen needed to complete combustion with a desirable level of
> free O2 in the gases. Under certain circumstances, for example natural gas
> boilers, the level of free O2 is very low (1% by volume). To maintain such
> a low level of excess air it may be necessary to have tertiary or even more
> air injection points.
>
> >Either way, the concept of "tertiary air" is bogus in the context of
> cookstove combustion.
>
> That is opinion only, contradicted by existing technologies that use it.
> One of the highest performing stick-burning stoves available has tertiary
> air injection ? the Rocketworks stoves from Adrian Padt in Durban, tens of
> thousands of which are sold each year.
>
> >The objective is to get the combustion to be complete with the proper
> amounts of primary and secondary air at the correct times and places.
>
> That is true in some cases and not in others. Most Rocket stoves (per
> Aprovecho design guides) have only a single air entrance. The Rocketworks
> stoves have three distinct times and places.
>
> >4. You wrote:
> >>This [MPF} process is ... how the Terra Preta soils in the Amazon were
> created over 20,000 years of slash and burn agriculture.
> >The origins of Terra Preta are still being debated by the experts in that
> field, which is certainly not your claimed field of expertise.
>
> I am sorry to hear you talk about ?fields of expertise?. Facts in evidence
> speak for themselves and are not invalidated by any messenger claims.
>
> >>The Amerindians cultivated land that was already productive, they did
> not create it de novo. Cecil confirms they farm patches of land that are
> already productive, not random areas. He observed this when he was doing
> PhD field research while at Harvard.
> >I have great respect for Cecil Cook. But somehow what you have
> attributed to him and his work has not reach my attention previously.
>
> So what?
>
> >And I do not accept your statements.
>
> I don?t care. I cared to know, by interviewing him, how the Amerindians
> farmed and what role char had in their agriculture. I reported this
> previously to this list. Maybe you forgot. It is in the archives. At the
> time Ron replied that did didn?t accept the observational reports from
> Cecil who lived in the jungle for 4 years learning how their agricultural
> society functions.
>
> >What happened thousands of years ago was not witnessed by Cecil. He
> could only observe the current day activities on lands that somehow became
> fertile.
>
> He reported observations, the most important of which is that they do not
> practise slash and burn farming over whole areas, but only the fertile
> bits. The practice of slash and burning creates a lot of char in the
> ground, something contested by Ron at that time and diminished by your
> message regarding the tree stumps burning in California. If you don?t
> believe me, you can visit the area right now and witness the MPFs moving
> into the ground to charcoal the root systems. A major part of the work of
> firefighters is extinguishing these MPFs. This is sufficient to convince me
> they exist. If they exist, they are producing biochar in the ground.
>
> >You can take that topic to the Biochar Listserv, if you want to discuss
> it further.
>
> I have no interest in discussions on another list. I receive information
> from the Biochar-Ontario group.
>
> >Sorry, I reject much of what you wrote.
>
> Don?t be sorry. Learn and be happy! We are sharing perspectives here.
>
> >I would not want you to be instructing people about TLUD stoves and char
> making and Terra Preta.
>
> That is none of your business over which you have no control.
>
> >IMHO, your comments about pyrolysis in different devices reflect poorly
> on your credibikity [sic] regarding your other strongly expressed
> positions, but that is a topic for others to discuss.
>
> And I feel sometimes you could learn a thing or two before posting
> comments about other technologies. Like everyone else, I find your
> contributions worthy and partially correct.
>
> Perhaps there is something you could answer: Is there something about char
> making that requires or drives their proponents to make completely
> unnecessary personal attacks and derisive, inaccurate speculations about
> motives? Outside the agricultural sector and the production of
> char-enhanced fertilisers, I find the biochar enthusiasts as a group to be
> cloistered and fanatical, frequently engaging in divisive speech about
> something they have recently discovered.
>
> I should take a minute to compliment you, Xavier, Julien, Jonas Haller and
> Dr Nurhuda for being very open to exchange with me advice, explanations and
> observations without reservations about how or where the information
> originates. All of you have produced very interesting and effective
> products suited to certain communities.
>
> Best regards for a better burn
> Crispin
>
> _______________________________________________
> Stoves mailing list
>
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>
>
> ________________________________
> 1Julien. P. Winter (2015) http://www.biochar-bangladesh.
> org/technology_tlud/ (Download date: Dec 6, 2017).
> -------------- next part --------------
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> ------------------------------
>
> Message: 19
> Date: Sun, 10 Dec 2017 08:37:38 -0800
> From: <tmiles at trmiles.com>
> To: "'Discussion of biomass cooking stoves'"
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Summary of TC285 activities
> Message-ID: <008001d371d5$324546d0$96cfd470$@trmiles.com>
> Content-Type: text/plain; charset="utf-8"
>
> Tami,
>
>
>
> Thank you very much for preparing this. It is helpful to understand the
> ISO process and who is involved.
>
>
>
> Other links and documents are here: https://www.iso.org/committee/
> 4857971.html
>
>
>
> Tom
>
>
>
> From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf
> Of Bond, Tami C
> Sent: Saturday, December 09, 2017 8:40 AM
> To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
> Subject: [Stoves] Summary of TC285 activities
>
>
>
> Hello Stovers,
>
>
>
> A couple of days ago, I sent a message to a small group that included Ron
> Larson and Nikhil Desai to explain some activities in TC 285. I authorized
> them to provide that message to the Stoves list if they so desired. I am
> disappointed to find that Ron quoted my message out of context in
> discussion of the ?char-deducted metric.? I did not intend my message to
> support or critique any such discussion. My message to them is now
> reproduced in its entirety below.
>
>
>
> Regards
>
> Tami
>
>
>
> - - - - - -
>
>
>
> Small clarifications? bearing in mind that I do not know the context from
> which the discussion comes.
>
>
>
> If a paper used the phrase ?the ISO standardized Water Boiling Test, ISO
> 2014?, this citation was incorrect. There is no such thing. Papers do not
> always communicate citations correctly. I wish the engineering and science
> communities had cite-checking, like law journals, but we do not.
>
>
>
> If anyone is concerned about what an ISO product might be, a list of all
> official products is available on the ISO browsing platform:
> www.iso.org/obp <http://www.iso.org/obp>
>
> A negative, in my view, is that the text of the standards themselves is
> not publicly available and can be accessed only for a fee.
>
>
>
> TC-285 is an ISO technical committee that contains a few working groups.
> Most of the work is done in the working groups. It is probably more
> effective to critique a product specifically, rather than the entire TC285,
> which encompasses multiple endeavors.
>
>
>
> The working groups in TC 285 are (my shorthand here? all have more formal
> names)
>
> WG1: Conceptual Framework (completing a publication on harmonized terms &
> definitions; next working on a paper to provide a framework for evaluation)
>
> WG2: Laboratory Protocols (this group is author of the draft lab standard
> protocol; next working on a more contextualized test method)
>
> WG3: Field Testing (responding to comments on a draft document regarding
> field testing)
>
> WG4: Social Impact (preparing a draft standard or communication)
>
>
>
> Task groups also exist, for fuels and communications.
>
>
>
> There is a current draft in Working Group 2 regarding controlled
> laboratory testing (it has a formal name that I can?t remember). Its
> product is under revision after responding to comments from national
> standard bodies, and has not been published yet. Some of its features have
> received some of the same criticisms as were provided on the WBT that is in
> wide public use, yet other contents are different, as happens through
> discussion.
>
>
>
> Many people are members of WG2 and not the others, or other groups and not
> WG2. Thus, it doesn?t make sense to cast stones at the whole TC 285 for a
> particular issue with a product. The best thing to do is comment on a
> product itself through one?s national standards body, or get involved with
> the product itself, or work on a subsequent or parallel product, or write
> technical papers that can be taken up into the consideration of future
> products.
>
>
>
> Sally Seitz works for ANSI, which holds the current secretariat. She is
> involved in logistical and procedural matters. It is the Secretariat?s job
> to ensure that proper procedure is followed. At plenary meetings, there is
> also a representative from ISO.
>
> Neeraja Penumetcha also assists with logistics, as well as contributing
> technical content in (at least) the Fuels task group.
>
> Both of these people provide helpful guidance to people who are not so
> familiar with procedural matters.
>
>
>
> All the members are volunteers, although I believe the secretariat is
> supported. Some individuals may be formally supported by their
> organizations to engage in the work. Others, like me, use their own time
> and pay their own way to attend meetings. Standards work is not something
> people do if they are seeking appreciation or wealth.
>
>
>
> Ron or Nikhil, you are welcome to communicate this to the Stoves list, if
> it helps clear anything up. I have meant to write a message like this for a
> while, but have not taken the time until now.
>
>
>
> Tami
>
>
>
>
>
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> ------------------------------
>
> Message: 20
> Date: Sun, 10 Dec 2017 09:41:46 -0700
> From: Gordon West <gordon.west at rtnewmexico.com>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID: <F8863547-6A0B-4C2C-B954-0B6C5EFB46E8 at rtnewmexico.com>
> Content-Type: text/plain; charset="utf-8"
>
> Is there a report on monitoring an Adams retort MPF using thermocouples? I
> am still not successfully visualizing the process.
>
> I did a bit of a search of technical reports on the chemistry of woody
> biomass pyrolysis and have not yet found a reference to the release of O2
> from heating the feedstock and its subsequent recombination with other
> elements resulting in an MPF. Several analyses of syngas that I saw show
> plenty of oxygen but it is bound in various fuel molecules.
>
> Gordon
>
>
>
>
>
> > On Dec 10, 2017, at 9:04 AM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com> wrote:
> >
> > Dear gordon
> >
> > You almost nailed it. Heating some small portion of the biomass and the
> temperature of the nearby fuel (not all of it) is sufficient to ignite a
> reaction that can continue indefinitely provided there is sufficient
> insulation and the oxygen content of the fuel is sufficient.
> >
> > There are two approaches that will work, as I understand it: the first
> is the charring of underground biomass (or coal) in the absence of
> additional oxygen. Once started, it will continue until the fuel is
> exhausted.
> >
> > The other does not require heating, but uses compressed air (oxygen) to
> provide the necessary reaction oxygen rapidly enough to get the reaction to
> continue (the Hawaiian invention).
> >
> > An MPF is the front at which the heat releasing reaction takes place.
> >
> > You can also consider the way char is formed. In the initial stage the
> energy needed to drive off the endothermic volatiles is more than the
> energy released by oxidizing the gases using only the oxygen available in
> the fuel. As the system heats up, the energy gap between evaporating
> volatiles and exothermic reactions decreases. At some point, the gap is
> small enough for the released oxygen to continue in the absence of
> additional air.
> >
> > TLUDs are in general too small to see this take place. They cool off too
> easily so additional air much be provided to sustain the reaction, which
> burns the rest of the hydrogen and at least some of the carbon.
> >
> > An underground fire can continue for centuries. All it has to do is get
> started. Prof Lloyd can explain how these fires can even auto-ignite. You
> have probably heard of stacks of hay setting themselves on fire by
> decomposition of the material in a large enough pile to retain the heat.
> Once it reaches or exceeds about 290 C the reactions are exothermic and
> from there it is a short trip to charging temperatures. The whole haystack
> can turn to char save the cool exterior.
> >
> > Burning coal seams manufacture their own oxygen from water. Coal doesn't
> have enough oxygen to sustain a pyrolytic front unless it is really hot.
> But burn they do.
> >
> > You can determine if there is an MPF but putting in a set of
> thermocouples and watching the front pass by. A burning log in an open fire
> has an MPF inside working it's way to the centre. The whole log will be
> charred long before it splits open.
> >
> > The interesting thing about a packed bed gasifier is that it can make
> gas predictably and controllable from ?small sized fuel generally
> considered a waste material. It is no small achievement.
> >
> > Regards
> > Crispin
> >
> >
> > I took a look at the Adams Retort design and watched a few videos. A
> couple of questions come to mind:
> >
> > 1) How does one determine that an MPF exists in an A-R?
> >
> > 2) I am not much of a chemist, but I would be interested to see an
> explanation of the reaction sequence where O2 is released and then burned
> in the MPF of an Adams Retort.
> >
> > It seems to me that if the external heat source is raising the
> temperature to the gasification point of the volatile components, thereby
> causing gasification (duh?), what purpose is the MPF serving?
> >
> > In a TLUD the MPF is burning some of the volatile gases to generate the
> heat needed to gasify un-pyrolyzed biomass.
> >
> > Gordon
> >
> >
> >
> >> On Dec 9, 2017, at 10:54 PM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com <mailto:crispinpigott at outlook.com>> wrote:
> >>
> >> Dear Paul
> >>
> >> >Some of what you wrote is correct, but you go too far or leave out
> some important distinctions, thereby implying that some things are equal,
> that is, some are not really as worthy and distinctive as others (Ron and
> Paul) have stated.
> >>
> >> Of course there were things left out. I am happy you included below
> further refinements to the explanation.
> >>
> >> >1. Pyrolysis progresses (migrates) through a piece or pile of biomass
> as heat is able to penetrate. True. The Adam retort (and other retorts)
> heat the biomass from many sides, but there is no flame (actual combustion)
> inside. It is a stretch of language to say that the pyrolysis in the retort
> >> >>has an MPF [migrating pyrolytic front] proceeding in a roughly
> horizontal direction.
> >>
> >> Au contraire. The Adam Retort (which heats the biomass from under a
> portion of the bottom of the pile, not multiple sides) does indeed have a
> MPF and the combustion is fed by oxidation using oxygen liberated by the
> thermal decomposition of the fuel. There is no added oxygen, but oxygen
> there definitely is. There is enough oxygen in biomass to almost completely
> combust the hydrogen content. In practise the carbon and hydrogen are both
> involved in sustaining the MPF. Once the fuel is hot enough, the MPF can
> move through the pile without any additional heat required.
> >>
> >> >Sorry, that should say "has external heating proceeding inward from
> several directions from the sides toward the center."
> >>
> >> That is an incorrect description of the Adam Retort. There are retorts
> that function in the manner you describe. His is not one of them.
> >>
> >> >Furthermore, the processes in a retort are in sequential order during
> numerous minutes to 1) heat virtually all of the biomass to drive off the
> moisture, then 2) add more heat to virtually all of the biomass to drive
> off the low-temperature volatiles to create torrified material, and than 3)
> to finally get the temperature hot enough to have actual pryrolysis, first
> in the 400 deg C range and then at higher temperatures if the external
> heating is continued.
> >>
> >> That is true for some retorts, not the Adams Retort.
> >>
> >> >In sharp contrast, in a TLUD there is a distinctive zone of a few cm
> depth with actual small amounts of combustion (of some of the initial
> offgases). That zone migrates through the pile of biomass, heating mainly
> by radiation a small layer of biomass below the MPF, then with pyrolysis
> at a rather uniform temperature (generally from 450 to 700 C, depending on
> USER CONTROLED [sic] flow of primary air) to create the char as the gases
> move upward.
> >>
> >> The same also happens in a downdraft pyrolyser, and a bottom-pit
> updraft pyrolyser such as those produce by Hirendra Chakrabarti in India.
> >>
> >> The addition of a control feature makes the process variable, however
> it does not fundamentally change how the system works.
> >>
> >> >You may choose to try to equate the two descriptions above, but that
> would diminish your credibility as a precision-seeking scientist.
> >>
> >> There is no need for that kind of talk. First familiarise yourself with
> the systems under discussion. Seen from the side, an Adam Retort starts the
> MPF on the bottom right and it moves over a period of about 2 hours to the
> top left. Prof Lloyd can provide examples of sustained MPF?s moving
> horizontally underground in the Witbank area of South Africa without any
> addition of primary air. There are conditions where primary is required,
> and others when it is not. Tiny stoves require it.
> >>
> >> >And to equate a smouldering tree stump to MPF is a stretch beyond a
> stretch. Yes, there is fire there, and yes there is pyrolysis occuring.
> But such comparison is akin to saying that a ladybug and a moose are the
> same because both are living creatures; and in fact both are animals.
> Even a petunia and a whale are both living organisms. Scientific
> comparisons need precision and detail.
> >>
> >> That is why the discussion is on principles not ladybugs. A dry tree
> stump can be ignited to char the stump and the roots underground, and in
> the 1800?s one could buy a kit for doing so. I was told of a different
> method when I was young involving a steel pipe and kerosene. The point was
> to get the stump hot enough so that the pyrolysis would continue into the
> ground. The TLUD stove with an MPF is no more than a containerised version
> with controllable primary air.
> >>
> >> 2. Ron correctly pointed out that in normal operation of TLUD stoves,
> there is zero O2 that gets past the MPF. That is vastly different from
> having so much primary air enter (as in Rocket stoves and other burners)
> that there is O2 moving upward above the fuel (where the gases were
> created).
> >>
> >> Ron is correct about the O2. It is indeed different (I don?t know about
> ?vastly? from stoves where the fuel and flames are ?attached? to the solid
> fuel and the gases oxidise as and when they can. it is also true (but I
> didn?t expound on it) that within a fuel bed there are zones without no
> available O2, just as in the zone above the char.
> >>
> >> >You are saying that is good as preheated secondary O2.
> >>
> >> Functionally that is secondary air provided simultaneously, at least in
> some cases. My definitions are general cases and can be applied to the
> situation you describe.
> >>
> >> >Maybe, but not really. It is simply inadequate combustion, with the
> results of undesirable emissions.
> >>
> >> That is speculation and cannot be true in all cases.
> >>
> >> >The excessive primary air (which you state should be secondary air)...
> >>
> >> Which I state has the function of providing secondary air?
> >>
> >> >?has had a cooling effect on the raw fuel that the combustion is
> trying to get hot enough to give off the pyrolytic gases.
> >>
> >> That is not a general case. It could happen.
> >>
> >> >In other words, that secondary air that has passed over the fuel is
> part of the problem, not part of a solution because it has taken heat away
> from the fuel.
> >>
> >> That is not the case. What ?problem?? Heat passed through a metal wall
> to secondary air is not ?different heat? from that gained by air passing
> through a fuel bed, or along a hot combustion chamber wall. There are many
> roads to Rome. Air that is consumed after preheating is indifferent to hwo
> the heat was gained.
> >>
> >> >3. Tertiary air: Defined as either 1) the needed secondary air that
> did not get into the combustion zone soon enough (meaning that there was
> poor stove design)
> >>
> >> I see this as inaccurate on two counts: 1) the secondary air may be
> added in a way that decomposes complex gases further before final
> combustion, and 2) the bit about poor design is unfair comment. There are
> many good designs you may not know about.
> >>
> >> >?or 2) excess air that will lower the temperature of the hot gases
> (meaning that this "tertiary air" was NOT needed nor part of the combustion
> process).
> >>
> >> Tertiary air may be provided for a number of reasons, but normally to
> provide the oxygen needed to complete combustion with a desirable level of
> free O2 in the gases. Under certain circumstances, for example natural gas
> boilers, the level of free O2 is very low (1% by volume). To maintain such
> a low level of excess air it may be necessary to have tertiary or even more
> air injection points.
> >>
> >> >Either way, the concept of "tertiary air" is bogus in the context of
> cookstove combustion.
> >>
> >> That is opinion only, contradicted by existing technologies that use
> it. One of the highest performing stick-burning stoves available has
> tertiary air injection ? the Rocketworks stoves from Adrian Padt in Durban,
> tens of thousands of which are sold each year.
> >>
> >> >The objective is to get the combustion to be complete with the proper
> amounts of primary and secondary air at the correct times and places.
> >>
> >> That is true in some cases and not in others. Most Rocket stoves (per
> Aprovecho design guides) have only a single air entrance. The Rocketworks
> stoves have three distinct times and places.
> >>
> >> >4. You wrote:
> >> >>This [MPF} process is ... how the Terra Preta soils in the Amazon
> were created over 20,000 years of slash and burn agriculture.
> >> >The origins of Terra Preta are still being debated by the experts in
> that field, which is certainly not your claimed field of expertise.
> >>
> >> I am sorry to hear you talk about ?fields of expertise?. Facts in
> evidence speak for themselves and are not invalidated by any messenger
> claims.
> >>
> >> >>The Amerindians cultivated land that was already productive, they did
> not create it de novo. Cecil confirms they farm patches of land that are
> already productive, not random areas. He observed this when he was doing
> PhD field research while at Harvard.
> >>
> >> >I have great respect for Cecil Cook. But somehow what you have
> attributed to him and his work has not reach my attention previously.
> >>
> >> So what?
> >>
> >> >And I do not accept your statements.
> >>
> >> I don?t care. I cared to know, by interviewing him, how the Amerindians
> farmed and what role char had in their agriculture. I reported this
> previously to this list. Maybe you forgot. It is in the archives. At the
> time Ron replied that did didn?t accept the observational reports from
> Cecil who lived in the jungle for 4 years learning how their agricultural
> society functions.
> >>
> >> >What happened thousands of years ago was not witnessed by Cecil. He
> could only observe the current day activities on lands that somehow became
> fertile.
> >>
> >> He reported observations, the most important of which is that they do
> not practise slash and burn farming over whole areas, but only the fertile
> bits. The practice of slash and burning creates a lot of char in the
> ground, something contested by Ron at that time and diminished by your
> message regarding the tree stumps burning in California. If you don?t
> believe me, you can visit the area right now and witness the MPFs moving
> into the ground to charcoal the root systems. A major part of the work of
> firefighters is extinguishing these MPFs. This is sufficient to convince me
> they exist. If they exist, they are producing biochar in the ground.
> >>
> >> >You can take that topic to the Biochar Listserv, if you want to
> discuss it further.
> >>
> >> I have no interest in discussions on another list. I receive
> information from the Biochar-Ontario group.
> >>
> >> >Sorry, I reject much of what you wrote.
> >>
> >> Don?t be sorry. Learn and be happy! We are sharing perspectives here.
> >>
> >> >I would not want you to be instructing people about TLUD stoves and
> char making and Terra Preta.
> >>
> >> That is none of your business over which you have no control.
> >>
> >> >IMHO, your comments about pyrolysis in different devices reflect
> poorly on your credibikity [sic] regarding your other strongly expressed
> positions, but that is a topic for others to discuss.
> >>
> >> And I feel sometimes you could learn a thing or two before posting
> comments about other technologies. Like everyone else, I find your
> contributions worthy and partially correct.
> >>
> >> Perhaps there is something you could answer: Is there something about
> char making that requires or drives their proponents to make completely
> unnecessary personal attacks and derisive, inaccurate speculations about
> motives? Outside the agricultural sector and the production of
> char-enhanced fertilisers, I find the biochar enthusiasts as a group to be
> cloistered and fanatical, frequently engaging in divisive speech about
> something they have recently discovered.
> >>
> >> I should take a minute to compliment you, Xavier, Julien, Jonas Haller
> and Dr Nurhuda for being very open to exchange with me advice, explanations
> and observations without reservations about how or where the information
> originates. All of you have produced very interesting and effective
> products suited to certain communities.
> >>
> >> Best regards for a better burn
> >> Crispin
> >>
> >> _______________________________________________
> >> Stoves mailing list
> >>
> >> to Send a Message to the list, use the email address
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> >
> >>
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> >
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> ------------------------------
>
> Message: 21
> Date: Sun, 10 Dec 2017 10:46:28 -0600
> From: Paul Anderson <psanders at ilstu.edu>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>, Doc Anderson <
> psanders at ilstu.edu>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID: <1da283c5-7295-068b-768e-3eb03a8b282a at ilstu.edu>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> Crispin,
>
> A full response will be later.?? But here are a couple of statements:
>
> 1.? Yes, there is O (oxygen) in carbohydrates.?? But those atoms will
> not become available during drying or even during torrification.?? So
> the retorts will need to wait until pyrolysis temperatures are reached
> for any internal O to become available.
>
> 2.? Inside the retort, even with some ambient O2 present between the
> pieces of fuel at the start, there is no combustion (chemical
> combinations releasing heat from burning of O2) if there is no spark or
> spontaneous combustion.? And I think that if such a spark (or flame)
> came into an enclosed retort chamber with a mixture of oxygen and
> combustible gases, that there could be some risk of explosion. I have
> not heard of that happening in Adam retorts or other retorts.
>
> Other obligations at this time prevent further comments now.
>
> Paul
>
>
> Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
> Email: psanders at ilstu.edu
> Skype: paultlud Phone: +1-309-452-7072
> Website: www.drtlud.com
>
> On 12/9/2017 11:54 PM, Crispin Pemberton-Pigott wrote:
> >
> > Dear Paul
> >
> > *>*Some of what you wrote is correct, but you go too far or leave out
> > some important distinctions, thereby implying that some things are
> > equal, that is, some are not really as worthy and distinctive as
> > others (Ron and Paul) have stated.
> >
> > Of course there were things left out. I am happy you included below
> > further refinements to the explanation.
> >
> > >1. Pyrolysis progresses (migrates) through a piece or pile of biomass
> > as heat is able to penetrate.? True.?? The Adam retort (and other
> > retorts) heat the biomass from many sides, but there is no flame
> > (actual combustion) inside.? It is a stretch of language to say that
> > the pyrolysis in the retort
> >
> > >>has an MPF [migrating pyrolytic front] proceeding in a roughly
> > horizontal direction.
> >
> > Au contraire. The Adam Retort (which heats the biomass from under
> > a portion of the bottom of the pile, not multiple sides) does
> > indeed have a MPF and the combustion is fed by oxidation using
> > oxygen liberated by the thermal decomposition of the fuel. There
> > is no /added/ oxygen, but oxygen there definitely is. There is
> > enough oxygen in biomass to almost completely combust the hydrogen
> > content. In practise the carbon and hydrogen are both involved in
> > sustaining the MPF. Once the fuel is hot enough, the MPF can move
> > through the pile without any additional heat required.
> >
> > >Sorry, that should say "has external heating proceeding inward from
> > several directions from the sides toward the center."
> >
> > That is an incorrect description of the Adam? Retort. There are
> > retorts that function in the manner you describe. His is not one of them.
> >
> > >Furthermore, the processes in a retort are in sequential order during
> > numerous minutes to 1) heat virtually all of the biomass to drive off
> > the moisture, then 2) add more heat to virtually all of the biomass to
> > drive off the low-temperature volatiles to create torrified material,
> > and than 3) to finally get the temperature hot enough to have actual
> > pryrolysis, first in the 400 deg C range and then at higher
> > temperatures if the external heating is continued.
> >
> > That is true for some retorts, not the Adams Retort.
> >
> >
> > >In sharp contrast, in a TLUD there is a distinctive zone of a few cm
> > depth with actual small amounts of combustion (of some of the initial
> > offgases).? That zone migrates through the pile of biomass, heating
> > mainly by radiation a small layer of biomass below the MPF, then with?
> > pyrolysis at a rather uniform temperature (generally from 450 to 700
> > C, depending on USER CONTROLED [/sic/] flow of primary air) to create
> > the char as the gases move upward.
> >
> > The same also happens in a downdraft pyrolyser, and a bottom-pit
> > updraft pyrolyser such as those produce by Hirendra Chakrabarti in India.
> >
> >
> > The addition of a control feature makes the process variable, however
> > it does not fundamentally change how the system works.
> >
> >
> > >You may choose to try to equate the two descriptions above, but that
> > would diminish your credibility as a precision-seeking scientist.
> >
> > There is no need for that kind of talk. First familiarise yourself
> > with the systems under discussion. Seen from the side, an Adam Retort
> > starts the MPF on the bottom right and it moves over a period of about
> > 2 hours to the top left. ?Prof Lloyd can provide examples of sustained
> > MPF?s moving horizontally underground in the Witbank area of South
> > Africa without any addition of primary air. There are conditions where
> > primary is required, and others when it is not. Tiny stoves require it.
> >
> > >And to equate a smouldering tree stump to MPF is a stretch beyond a
> > stretch.? Yes, there is fire there, and yes there is pyrolysis
> > occuring.?? But such comparison is akin to saying that a ladybug and a
> > moose are the same because both are living creatures; and in fact both
> > are animals.?? Even a petunia and a whale are both living organisms.?
> > Scientific comparisons need precision and detail.
> >
> > That is why the discussion is on principles not ladybugs. A dry tree
> > stump can be ignited to char the stump and the roots underground, and
> > in the 1800?s one could buy a kit for doing so. I was told of a
> > different method when I was young involving a steel pipe and kerosene.
> > The point was to get the stump hot enough so that the pyrolysis would
> > continue into the ground. The TLUD stove with an MPF is no more than a
> > containerised version with controllable primary air.
> >
> >
> > 2.? Ron correctly pointed out that in normal operation of TLUD stoves,
> > there is zero O2 that gets past the MPF.? That is vastly different
> > from having so much primary air enter (as in Rocket stoves and other
> > burners) that there is O2 moving upward above the fuel (where the?
> > gases were created).
> >
> > Ron is correct about the O_2 . It is indeed different (I don?t know
> > about ?vastly? from stoves where the fuel and flames are ?attached? to
> > the solid fuel and the gases oxidise as and when they can. it is also
> > true (but I didn?t expound on it) that within a fuel bed there are
> > zones without no available O_2 , just as in the zone above the char.
> >
> > >You are saying that is good as preheated secondary O2.
> >
> > Functionally that is secondary air provided simultaneously, at least
> > in some cases. My definitions are general cases and can be applied to
> > the situation you describe.
> >
> > >Maybe, but not really.? It is simply inadequate combustion, with the
> > results of undesirable emissions.
> >
> > That is speculation and cannot be true in all cases.
> >
> > >The excessive primary air (which you state should be secondary air)...
> >
> > Which I state has the function of providing secondary air?
> >
> > >?has had a cooling effect on the raw fuel that the combustion is trying
> > to get hot enough to give off the pyrolytic gases.
> >
> > That is not a general case. It could happen.
> >
> > >In other words, that secondary air that has passed over the fuel is
> > part of the problem, not part of a solution because it has taken heat
> > away from the fuel.
> >
> > That is not the case. What ?problem?? Heat passed through a metal wall
> > to secondary air is not ?different heat? from that gained by air
> > passing through a fuel bed, or along a hot combustion chamber wall.
> > There are many roads to Rome. Air that is consumed after preheating is
> > indifferent to hwo the heat was gained.
> >
> >
> > >3.? Tertiary air: Defined as either 1) the needed secondary air that
> > did not get into the combustion zone soon enough (meaning that there
> > was poor stove design)
> >
> > I see this as inaccurate on two counts: 1) the secondary air may be
> > added in a way that decomposes complex gases further before final
> > combustion, and 2) the bit about poor design is unfair comment. There
> > are many good designs you may not know about.
> >
> > >?or 2) excess air that will lower the temperature of the hot gases
> > (meaning that this "tertiary air" was NOT needed nor part of the
> > combustion process).
> >
> > Tertiary air may be provided for a number of reasons, but normally to
> > provide the oxygen needed to complete combustion with a desirable
> > level of free O_2 in the gases. Under certain circumstances, for
> > example natural gas boilers, the level of free O_2 is very low (1% by
> > volume). To maintain such a low level of excess air it may be
> > necessary to have tertiary or even more air injection points.
> >
> >
> > >Either way, the concept of "tertiary air" is bogus in the context of
> > cookstove combustion.
> >
> > That is opinion only, contradicted by existing technologies that use
> > it. One of the highest performing stick-burning stoves available has
> > tertiary air injection ? the Rocketworks stoves from Adrian Padt in
> > Durban, tens of thousands of which are sold each year.
> >
> > >The objective is to get the combustion to be complete with the proper
> > amounts of primary and secondary air at the correct times and places.
> >
> > That is true in some cases and not in others. Most Rocket stoves (per
> > Aprovecho design guides) have only a single air entrance. The
> > Rocketworks stoves have three distinct times and places.
> >
> >
> > >4.? You wrote:
> >
> > >>This [MPF} process is ... how the Terra Preta soils in the Amazon
> > were created over 20,000 years of slash and burn agriculture.
> >
> > >The origins of Terra Preta are still being debated by the experts in
> > that field, which is certainly not your claimed field of expertise.
> >
> > I am sorry to hear you talk about ?fields of expertise?. Facts in
> > evidence speak for themselves and are not invalidated by any messenger
> > claims.
> >
> > >>The Amerindians cultivated land that was already productive, they
> > did not create it /de novo/. Cecil confirms they farm patches of
> > land that are already productive, not random areas. He observed
> > this when he was doing PhD field research while at Harvard.
> >
> > >I have great respect for Cecil Cook.?? But somehow what you have
> > attributed to him and his work has not reach my attention previously.
> >
> > So what?
> >
> > >And I do not accept your statements.
> >
> > I don?t care. I cared to know, by interviewing him, how the
> > Amerindians farmed and what role char had in their agriculture. I
> > reported this previously to this list. Maybe you forgot. It is in the
> > archives. At the time Ron replied that did didn?t accept the
> > observational reports from Cecil who lived in the jungle for 4 years
> > learning how their agricultural society functions.
> >
> > >What happened thousands of years ago was not witnessed by Cecil. He
> > could only observe the current day activities on lands that somehow
> > became fertile.
> >
> > He reported observations, the most important of which is that they do
> > not practise slash and burn farming over whole areas, but only the
> > fertile bits. The practice of slash and burning creates a lot of char
> > in the ground, something contested by Ron at that time and diminished
> > by your message regarding the tree stumps burning in California. If
> > you don?t believe me, you can visit the area right now and witness the
> > MPFs moving into the ground to charcoal the root systems. A major part
> > of the work of firefighters is extinguishing these MPFs. This is
> > sufficient to convince me they exist. If they exist, they are
> > producing biochar in the ground.
> >
> > >You can take that topic to the Biochar Listserv, if you want to
> > discuss it further.
> >
> > I have no interest in discussions on another list. I receive
> > information from the Biochar-Ontario group.
> >
> >
> > >Sorry, I reject much of what you wrote.
> >
> > Don?t be sorry. Learn and be happy! We are sharing perspectives here.
> >
> > >I would not want you to be instructing people about TLUD stoves and
> > char making and Terra Preta.
> >
> > That is none of your business over which you have no control.
> >
> > >IMHO, your comments about pyrolysis in different devices reflect
> > poorly on your credibikity [/sic/] regarding your other strongly
> > expressed positions, but that is a topic for others to discuss.
> >
> > And I feel sometimes you could learn a thing or two before posting
> > comments about other technologies. Like everyone else, I find your
> > contributions worthy and partially correct.
> >
> >
> > Perhaps there is something you could answer: Is there something about
> > char making that requires or drives their proponents to make
> > completely unnecessary personal attacks and derisive, inaccurate
> > speculations about motives?? Outside the agricultural sector and the
> > production of char-enhanced fertilisers, I find the biochar
> > enthusiasts as a group to be cloistered and fanatical, frequently
> > engaging in divisive speech about something they have recently
> > discovered.
> >
> > I should take a minute to compliment you, Xavier, Julien, Jonas Haller
> > and Dr Nurhuda for being very open to exchange with me advice,
> > explanations and observations without reservations about how or where
> > the information originates. All of you have produced very interesting
> > and effective products suited to certain communities.
> >
> > Best regards for a better burn
> >
> > Crispin
> >
> >
> >
> > _______________________________________________
> > Stoves mailing list
> >
> > to Send a Message to the list, use the email address
> > stoves at lists.bioenergylists.org
> >
> > to UNSUBSCRIBE or Change your List Settings use the web page
> > http://lists.bioenergylists.org/mailman/listinfo/stoves_
> lists.bioenergylists.org
> >
> > for more Biomass Cooking Stoves, News and Information see our web site:
> > http://stoves.bioenergylists.org/
> >
>
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> ------------------------------
>
> Message: 22
> Date: Sun, 10 Dec 2017 10:10:08 -0700
> From: Gordon West <gordon.west at rtnewmexico.com>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID: <EAFEFA45-2714-4F9D-B733-1FB2D74E0BBF at rtnewmexico.com>
> Content-Type: text/plain; charset="utf-8"
>
> I would like to add some context to my interest in MPFs. I will also post
> this on the biochar list, but as there is some relation to stoves I?m also
> keeping it here.
>
> Our systems are designed to be community-scaled ?industrial?, and because
> of that we have an interest in being able to modulate the pyrolysis
> reaction down to ?idle? when heat is not needed, then to start it back up
> on demand (in a continuous feed device, not a batch system). We have been
> able to do this, but not in a reliably smooth manner. So it is very
> important for us to understand the processes happening at the MPF in detail.
>
> One thing we know is that we can snuff the MPF by sealing off all external
> inputs of air. In our experiments, a small quantity of air leakage, from
> either the bottom through the biomass feedstock, or from the top coming
> down through finished char, keeps the MPF hot enough to restart upon the
> application of sufficient primary air. During idle it produces a small
> amount of very foul smelling gas that is of insufficient density to burn on
> its own. Seal off all air and the MPF snuffs completely within a short time
> and the MPF cools below ignition temperature.
>
> Gordon
>
>
>
>
> > On Dec 10, 2017, at 9:41 AM, Gordon West <gordon.west at rtnewmexico.com>
> wrote:
> >
> > Is there a report on monitoring an Adams retort MPF using thermocouples?
> I am still not successfully visualizing the process.
> >
> > I did a bit of a search of technical reports on the chemistry of woody
> biomass pyrolysis and have not yet found a reference to the release of O2
> from heating the feedstock and its subsequent recombination with other
> elements resulting in an MPF. Several analyses of syngas that I saw show
> plenty of oxygen but it is bound in various fuel molecules.
> >
> > Gordon
> >
> >
> >
> >
> >
> >> On Dec 10, 2017, at 9:04 AM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com <mailto:crispinpigott at outlook.com>> wrote:
> >>
> >> Dear gordon
> >>
> >> You almost nailed it. Heating some small portion of the biomass and the
> temperature of the nearby fuel (not all of it) is sufficient to ignite a
> reaction that can continue indefinitely provided there is sufficient
> insulation and the oxygen content of the fuel is sufficient.
> >>
> >> There are two approaches that will work, as I understand it: the first
> is the charring of underground biomass (or coal) in the absence of
> additional oxygen. Once started, it will continue until the fuel is
> exhausted.
> >>
> >> The other does not require heating, but uses compressed air (oxygen) to
> provide the necessary reaction oxygen rapidly enough to get the reaction to
> continue (the Hawaiian invention).
> >>
> >> An MPF is the front at which the heat releasing reaction takes place.
> >>
> >> You can also consider the way char is formed. In the initial stage the
> energy needed to drive off the endothermic volatiles is more than the
> energy released by oxidizing the gases using only the oxygen available in
> the fuel. As the system heats up, the energy gap between evaporating
> volatiles and exothermic reactions decreases. At some point, the gap is
> small enough for the released oxygen to continue in the absence of
> additional air.
> >>
> >> TLUDs are in general too small to see this take place. They cool off
> too easily so additional air much be provided to sustain the reaction,
> which burns the rest of the hydrogen and at least some of the carbon.
> >>
> >> An underground fire can continue for centuries. All it has to do is get
> started. Prof Lloyd can explain how these fires can even auto-ignite. You
> have probably heard of stacks of hay setting themselves on fire by
> decomposition of the material in a large enough pile to retain the heat.
> Once it reaches or exceeds about 290 C the reactions are exothermic and
> from there it is a short trip to charging temperatures. The whole haystack
> can turn to char save the cool exterior.
> >>
> >> Burning coal seams manufacture their own oxygen from water. Coal
> doesn't have enough oxygen to sustain a pyrolytic front unless it is really
> hot. But burn they do.
> >>
> >> You can determine if there is an MPF but putting in a set of
> thermocouples and watching the front pass by. A burning log in an open fire
> has an MPF inside working it's way to the centre. The whole log will be
> charred long before it splits open.
> >>
> >> The interesting thing about a packed bed gasifier is that it can make
> gas predictably and controllable from ?small sized fuel generally
> considered a waste material. It is no small achievement.
> >>
> >> Regards
> >> Crispin
> >>
> >>
> >> I took a look at the Adams Retort design and watched a few videos. A
> couple of questions come to mind:
> >>
> >> 1) How does one determine that an MPF exists in an A-R?
> >>
> >> 2) I am not much of a chemist, but I would be interested to see an
> explanation of the reaction sequence where O2 is released and then burned
> in the MPF of an Adams Retort.
> >>
> >> It seems to me that if the external heat source is raising the
> temperature to the gasification point of the volatile components, thereby
> causing gasification (duh?), what purpose is the MPF serving?
> >>
> >> In a TLUD the MPF is burning some of the volatile gases to generate the
> heat needed to gasify un-pyrolyzed biomass.
> >>
> >> Gordon
> >>
> >>
> >>
> >>> On Dec 9, 2017, at 10:54 PM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com <mailto:crispinpigott at outlook.com>> wrote:
> >>>
> >>> Dear Paul
> >>>
> >>> >Some of what you wrote is correct, but you go too far or leave out
> some important distinctions, thereby implying that some things are equal,
> that is, some are not really as worthy and distinctive as others (Ron and
> Paul) have stated.
> >>>
> >>> Of course there were things left out. I am happy you included below
> further refinements to the explanation.
> >>>
> >>> >1. Pyrolysis progresses (migrates) through a piece or pile of
> biomass as heat is able to penetrate. True. The Adam retort (and other
> retorts) heat the biomass from many sides, but there is no flame (actual
> combustion) inside. It is a stretch of language to say that the pyrolysis
> in the retort
> >>> >>has an MPF [migrating pyrolytic front] proceeding in a roughly
> horizontal direction.
> >>>
> >>> Au contraire. The Adam Retort (which heats the biomass from under a
> portion of the bottom of the pile, not multiple sides) does indeed have a
> MPF and the combustion is fed by oxidation using oxygen liberated by the
> thermal decomposition of the fuel. There is no added oxygen, but oxygen
> there definitely is. There is enough oxygen in biomass to almost completely
> combust the hydrogen content. In practise the carbon and hydrogen are both
> involved in sustaining the MPF. Once the fuel is hot enough, the MPF can
> move through the pile without any additional heat required.
> >>>
> >>> >Sorry, that should say "has external heating proceeding inward from
> several directions from the sides toward the center."
> >>>
> >>> That is an incorrect description of the Adam Retort. There are
> retorts that function in the manner you describe. His is not one of them.
> >>>
> >>> >Furthermore, the processes in a retort are in sequential order during
> numerous minutes to 1) heat virtually all of the biomass to drive off the
> moisture, then 2) add more heat to virtually all of the biomass to drive
> off the low-temperature volatiles to create torrified material, and than 3)
> to finally get the temperature hot enough to have actual pryrolysis, first
> in the 400 deg C range and then at higher temperatures if the external
> heating is continued.
> >>>
> >>> That is true for some retorts, not the Adams Retort.
> >>>
> >>> >In sharp contrast, in a TLUD there is a distinctive zone of a few cm
> depth with actual small amounts of combustion (of some of the initial
> offgases). That zone migrates through the pile of biomass, heating mainly
> by radiation a small layer of biomass below the MPF, then with pyrolysis
> at a rather uniform temperature (generally from 450 to 700 C, depending on
> USER CONTROLED [sic] flow of primary air) to create the char as the gases
> move upward.
> >>>
> >>> The same also happens in a downdraft pyrolyser, and a bottom-pit
> updraft pyrolyser such as those produce by Hirendra Chakrabarti in India.
> >>>
> >>> The addition of a control feature makes the process variable, however
> it does not fundamentally change how the system works.
> >>>
> >>> >You may choose to try to equate the two descriptions above, but that
> would diminish your credibility as a precision-seeking scientist.
> >>>
> >>> There is no need for that kind of talk. First familiarise yourself
> with the systems under discussion. Seen from the side, an Adam Retort
> starts the MPF on the bottom right and it moves over a period of about 2
> hours to the top left. Prof Lloyd can provide examples of sustained MPF?s
> moving horizontally underground in the Witbank area of South Africa without
> any addition of primary air. There are conditions where primary is
> required, and others when it is not. Tiny stoves require it.
> >>>
> >>> >And to equate a smouldering tree stump to MPF is a stretch beyond a
> stretch. Yes, there is fire there, and yes there is pyrolysis occuring.
> But such comparison is akin to saying that a ladybug and a moose are the
> same because both are living creatures; and in fact both are animals.
> Even a petunia and a whale are both living organisms. Scientific
> comparisons need precision and detail.
> >>>
> >>> That is why the discussion is on principles not ladybugs. A dry tree
> stump can be ignited to char the stump and the roots underground, and in
> the 1800?s one could buy a kit for doing so. I was told of a different
> method when I was young involving a steel pipe and kerosene. The point was
> to get the stump hot enough so that the pyrolysis would continue into the
> ground. The TLUD stove with an MPF is no more than a containerised version
> with controllable primary air.
> >>>
> >>> 2. Ron correctly pointed out that in normal operation of TLUD stoves,
> there is zero O2 that gets past the MPF. That is vastly different from
> having so much primary air enter (as in Rocket stoves and other burners)
> that there is O2 moving upward above the fuel (where the gases were
> created).
> >>>
> >>> Ron is correct about the O2. It is indeed different (I don?t know
> about ?vastly? from stoves where the fuel and flames are ?attached? to the
> solid fuel and the gases oxidise as and when they can. it is also true (but
> I didn?t expound on it) that within a fuel bed there are zones without no
> available O2, just as in the zone above the char.
> >>>
> >>> >You are saying that is good as preheated secondary O2.
> >>>
> >>> Functionally that is secondary air provided simultaneously, at least
> in some cases. My definitions are general cases and can be applied to the
> situation you describe.
> >>>
> >>> >Maybe, but not really. It is simply inadequate combustion, with the
> results of undesirable emissions.
> >>>
> >>> That is speculation and cannot be true in all cases.
> >>>
> >>> >The excessive primary air (which you state should be secondary air)...
> >>>
> >>> Which I state has the function of providing secondary air?
> >>>
> >>> >?has had a cooling effect on the raw fuel that the combustion is
> trying to get hot enough to give off the pyrolytic gases.
> >>>
> >>> That is not a general case. It could happen.
> >>>
> >>> >In other words, that secondary air that has passed over the fuel is
> part of the problem, not part of a solution because it has taken heat away
> from the fuel.
> >>>
> >>> That is not the case. What ?problem?? Heat passed through a metal wall
> to secondary air is not ?different heat? from that gained by air passing
> through a fuel bed, or along a hot combustion chamber wall. There are many
> roads to Rome. Air that is consumed after preheating is indifferent to hwo
> the heat was gained.
> >>>
> >>> >3. Tertiary air: Defined as either 1) the needed secondary air
> that did not get into the combustion zone soon enough (meaning that there
> was poor stove design)
> >>>
> >>> I see this as inaccurate on two counts: 1) the secondary air may be
> added in a way that decomposes complex gases further before final
> combustion, and 2) the bit about poor design is unfair comment. There are
> many good designs you may not know about.
> >>>
> >>> >?or 2) excess air that will lower the temperature of the hot gases
> (meaning that this "tertiary air" was NOT needed nor part of the combustion
> process).
> >>>
> >>> Tertiary air may be provided for a number of reasons, but normally to
> provide the oxygen needed to complete combustion with a desirable level of
> free O2 in the gases. Under certain circumstances, for example natural gas
> boilers, the level of free O2 is very low (1% by volume). To maintain such
> a low level of excess air it may be necessary to have tertiary or even more
> air injection points.
> >>>
> >>> >Either way, the concept of "tertiary air" is bogus in the context of
> cookstove combustion.
> >>>
> >>> That is opinion only, contradicted by existing technologies that use
> it. One of the highest performing stick-burning stoves available has
> tertiary air injection ? the Rocketworks stoves from Adrian Padt in Durban,
> tens of thousands of which are sold each year.
> >>>
> >>> >The objective is to get the combustion to be complete with the proper
> amounts of primary and secondary air at the correct times and places.
> >>>
> >>> That is true in some cases and not in others. Most Rocket stoves (per
> Aprovecho design guides) have only a single air entrance. The Rocketworks
> stoves have three distinct times and places.
> >>>
> >>> >4. You wrote:
> >>> >>This [MPF} process is ... how the Terra Preta soils in the Amazon
> were created over 20,000 years of slash and burn agriculture.
> >>> >The origins of Terra Preta are still being debated by the experts in
> that field, which is certainly not your claimed field of expertise.
> >>>
> >>> I am sorry to hear you talk about ?fields of expertise?. Facts in
> evidence speak for themselves and are not invalidated by any messenger
> claims.
> >>>
> >>> >>The Amerindians cultivated land that was already productive, they
> did not create it de novo. Cecil confirms they farm patches of land that
> are already productive, not random areas. He observed this when he was
> doing PhD field research while at Harvard.
> >>>
> >>> >I have great respect for Cecil Cook. But somehow what you have
> attributed to him and his work has not reach my attention previously.
> >>>
> >>> So what?
> >>>
> >>> >And I do not accept your statements.
> >>>
> >>> I don?t care. I cared to know, by interviewing him, how the
> Amerindians farmed and what role char had in their agriculture. I reported
> this previously to this list. Maybe you forgot. It is in the archives. At
> the time Ron replied that did didn?t accept the observational reports from
> Cecil who lived in the jungle for 4 years learning how their agricultural
> society functions.
> >>>
> >>> >What happened thousands of years ago was not witnessed by Cecil. He
> could only observe the current day activities on lands that somehow became
> fertile.
> >>>
> >>> He reported observations, the most important of which is that they do
> not practise slash and burn farming over whole areas, but only the fertile
> bits. The practice of slash and burning creates a lot of char in the
> ground, something contested by Ron at that time and diminished by your
> message regarding the tree stumps burning in California. If you don?t
> believe me, you can visit the area right now and witness the MPFs moving
> into the ground to charcoal the root systems. A major part of the work of
> firefighters is extinguishing these MPFs. This is sufficient to convince me
> they exist. If they exist, they are producing biochar in the ground.
> >>>
> >>> >You can take that topic to the Biochar Listserv, if you want to
> discuss it further.
> >>>
> >>> I have no interest in discussions on another list. I receive
> information from the Biochar-Ontario group.
> >>>
> >>> >Sorry, I reject much of what you wrote.
> >>>
> >>> Don?t be sorry. Learn and be happy! We are sharing perspectives here.
> >>>
> >>> >I would not want you to be instructing people about TLUD stoves and
> char making and Terra Preta.
> >>>
> >>> That is none of your business over which you have no control.
> >>>
> >>> >IMHO, your comments about pyrolysis in different devices reflect
> poorly on your credibikity [sic] regarding your other strongly expressed
> positions, but that is a topic for others to discuss.
> >>>
> >>> And I feel sometimes you could learn a thing or two before posting
> comments about other technologies. Like everyone else, I find your
> contributions worthy and partially correct.
> >>>
> >>> Perhaps there is something you could answer: Is there something about
> char making that requires or drives their proponents to make completely
> unnecessary personal attacks and derisive, inaccurate speculations about
> motives? Outside the agricultural sector and the production of
> char-enhanced fertilisers, I find the biochar enthusiasts as a group to be
> cloistered and fanatical, frequently engaging in divisive speech about
> something they have recently discovered.
> >>>
> >>> I should take a minute to compliment you, Xavier, Julien, Jonas Haller
> and Dr Nurhuda for being very open to exchange with me advice, explanations
> and observations without reservations about how or where the information
> originates. All of you have produced very interesting and effective
> products suited to certain communities.
> >>>
> >>> Best regards for a better burn
> >>> Crispin
> >>>
> >>> _______________________________________________
> >>> Stoves mailing list
> >>>
> >>> to Send a Message to the list, use the email address
> >>> stoves at lists.bioenergylists.org <mailto:stoves at lists.
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> >>
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> >>
> >
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> >
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>
> Message: 23
> Date: Sun, 10 Dec 2017 18:05:51 +0000
> From: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID:
> <MWHPR22MB0784902774E22AE112E6FEABB1360 at MWHPR22MB0784.
> namprd22.prod.outlook.com>
>
> Content-Type: text/plain; charset="utf-8"
>
> Dear Paul
>
> >1. Yes, there is O (oxygen) in carbohydrates. But those atoms will not
> become available during drying or even during torrification.
>
> The volatiles released during torrefaction are hydrocarbons and organic
> molecules that contain oxygen. I agree that the pyrolysis temperature must
> be reached to get a self-sustaining reaction. I can?t comment on the amount
> of O available and when. Torrefied pellets are brown from what ?
> caramelization of sugars? Maybe Tom Miles can comment.
>
> >2. Inside the retort, even with some ambient O2 present between the
> pieces of fuel at the start, there is no combustion (chemical combinations
> releasing heat from burning of O2) if there is no spark or spontaneous
> combustion.
>
> As soon as the fuel reaches the auto-ignition temperature, there is
> combustion. There is no need for a spark or flame to start. Long before
> that, the fuel start decomposing, releasing O, H and N as gases. In theory
> there could be a *poof* but the flame speed of the wet gas is very slow and
> you might not notice.
>
> >And I think that if such a spark (or flame) came into an enclosed retort
> chamber with a mixture of oxygen and combustible gases, that there could be
> some risk of explosion.
>
> The oxidation takes place within the fuel. There could only be an
> explosion if there were some free oxygen present in the freed gases.
>
> For those who want to look further into the chemistry of this process,
> there is a calculation made in the HTP analysis spreadsheet that calculates
> the air demand of the fuel based on the elemental composition of the fuel
> and the char remaining at the end. From an assumed need for all oxygen to
> come from air, the actual requirement for a TLUD making a lot of char is
> only 20% of the theoretical need for the whole fuel, because 80% is
> provided from the biomass itself.
>
> EA+1 = ?
>
> where ? is the total air demand. This calculation is incorrect. The real
> values for a TLUD are
>
> EA+0.2 = ?
>
> You only need to provide 1/6th of the theoretical oxygen requirement of
> the fuel, provided it is biomass and you want to make char.
>
> Do you remember list member Yuri in Russia talking about explosions in
> burning charcoal piles cause by dousing it with water? A reaction creates
> hydrogen and oxygen from the water. Those conditions don?t exist in the
> Adam Retort where there is no free O2 to speak of.
>
> Regards
> Crispin
>
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> ------------------------------
>
> Message: 24
> Date: Sun, 10 Dec 2017 18:05:48 +0000
> From: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID:
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> namprd22.prod.outlook.com>
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>
> Dear Gordon
>
> To be technical about it, the thermal decomposition of biomass releases O
> (not O2) as well as N and H in approximately the same ratio as they occur
> in the material.
>
> All that is required is to heat the fuel. If it is heated with inadequate
> oxygen available, some of the fuel will remain unburned. That naturally is
> the carbon, which is the most difficult to evaporate. The surface burns.
>
> As explained earlier, if the fuel is heated enough, a TLUD burning wood
> pellets would continue burning (pyrolysing) without any added air. As the H
> burned, it would release 120 MJ/kg and the carbon burned to CO would
> release about 8 MJ/kg. There is enough to keep the fire going if it is
> large enough and insulated.
>
> Regards
> Crispin
>
>
> From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf
> Of Gordon West
> Sent: 10-Dec-17 22:42
> To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
>
> Is there a report on monitoring an Adams retort MPF using thermocouples? I
> am still not successfully visualizing the process.
>
> I did a bit of a search of technical reports on the chemistry of woody
> biomass pyrolysis and have not yet found a reference to the release of O2
> from heating the feedstock and its subsequent recombination with other
> elements resulting in an MPF. Several analyses of syngas that I saw show
> plenty of oxygen but it is bound in various fuel molecules.
>
> Gordon
>
>
>
>
>
> On Dec 10, 2017, at 9:04 AM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com<mailto:crispinpigott at outlook.com>> wrote:
>
> Dear gordon
>
> You almost nailed it. Heating some small portion of the biomass and the
> temperature of the nearby fuel (not all of it) is sufficient to ignite a
> reaction that can continue indefinitely provided there is sufficient
> insulation and the oxygen content of the fuel is sufficient.
>
> There are two approaches that will work, as I understand it: the first is
> the charring of underground biomass (or coal) in the absence of additional
> oxygen. Once started, it will continue until the fuel is exhausted.
>
> The other does not require heating, but uses compressed air (oxygen) to
> provide the necessary reaction oxygen rapidly enough to get the reaction to
> continue (the Hawaiian invention).
>
> An MPF is the front at which the heat releasing reaction takes place.
>
> You can also consider the way char is formed. In the initial stage the
> energy needed to drive off the endothermic volatiles is more than the
> energy released by oxidizing the gases using only the oxygen available in
> the fuel. As the system heats up, the energy gap between evaporating
> volatiles and exothermic reactions decreases. At some point, the gap is
> small enough for the released oxygen to continue in the absence of
> additional air.
>
> TLUDs are in general too small to see this take place. They cool off too
> easily so additional air much be provided to sustain the reaction, which
> burns the rest of the hydrogen and at least some of the carbon.
>
> An underground fire can continue for centuries. All it has to do is get
> started. Prof Lloyd can explain how these fires can even auto-ignite. You
> have probably heard of stacks of hay setting themselves on fire by
> decomposition of the material in a large enough pile to retain the heat.
> Once it reaches or exceeds about 290 C the reactions are exothermic and
> from there it is a short trip to charging temperatures. The whole haystack
> can turn to char save the cool exterior.
>
> Burning coal seams manufacture their own oxygen from water. Coal doesn't
> have enough oxygen to sustain a pyrolytic front unless it is really hot.
> But burn they do.
>
> You can determine if there is an MPF but putting in a set of thermocouples
> and watching the front pass by. A burning log in an open fire has an MPF
> inside working it's way to the centre. The whole log will be charred long
> before it splits open.
>
> The interesting thing about a packed bed gasifier is that it can make gas
> predictably and controllable from ?small sized fuel generally considered a
> waste material. It is no small achievement.
>
> Regards
> Crispin
>
>
> I took a look at the Adams Retort design and watched a few videos. A
> couple of questions come to mind:
>
> 1) How does one determine that an MPF exists in an A-R?
>
> 2) I am not much of a chemist, but I would be interested to see an
> explanation of the reaction sequence where O2 is released and then burned
> in the MPF of an Adams Retort.
>
> It seems to me that if the external heat source is raising the temperature
> to the gasification point of the volatile components, thereby causing
> gasification (duh?), what purpose is the MPF serving?
>
> In a TLUD the MPF is burning some of the volatile gases to generate the
> heat needed to gasify un-pyrolyzed biomass.
>
> Gordon
>
>
>
> On Dec 9, 2017, at 10:54 PM, Crispin Pemberton-Pigott <
> crispinpigott at outlook.com<mailto:crispinpigott at outlook.com>> wrote:
>
> Dear Paul
>
> >Some of what you wrote is correct, but you go too far or leave out some
> important distinctions, thereby implying that some things are equal, that
> is, some are not really as worthy and distinctive as others (Ron and Paul)
> have stated.
>
> Of course there were things left out. I am happy you included below
> further refinements to the explanation.
>
> >1. Pyrolysis progresses (migrates) through a piece or pile of biomass as
> heat is able to penetrate. True. The Adam retort (and other retorts)
> heat the biomass from many sides, but there is no flame (actual combustion)
> inside. It is a stretch of language to say that the pyrolysis in the retort
> >>has an MPF [migrating pyrolytic front] proceeding in a roughly
> horizontal direction.
>
> Au contraire. The Adam Retort (which heats the biomass from under a
> portion of the bottom of the pile, not multiple sides) does indeed have a
> MPF and the combustion is fed by oxidation using oxygen liberated by the
> thermal decomposition of the fuel. There is no added oxygen, but oxygen
> there definitely is. There is enough oxygen in biomass to almost completely
> combust the hydrogen content. In practise the carbon and hydrogen are both
> involved in sustaining the MPF. Once the fuel is hot enough, the MPF can
> move through the pile without any additional heat required.
>
> >Sorry, that should say "has external heating proceeding inward from
> several directions from the sides toward the center."
>
> That is an incorrect description of the Adam Retort. There are retorts
> that function in the manner you describe. His is not one of them.
>
> >Furthermore, the processes in a retort are in sequential order during
> numerous minutes to 1) heat virtually all of the biomass to drive off the
> moisture, then 2) add more heat to virtually all of the biomass to drive
> off the low-temperature volatiles to create torrified material, and than 3)
> to finally get the temperature hot enough to have actual pryrolysis, first
> in the 400 deg C range and then at higher temperatures if the external
> heating is continued.
>
> That is true for some retorts, not the Adams Retort.
>
> >In sharp contrast, in a TLUD there is a distinctive zone of a few cm
> depth with actual small amounts of combustion (of some of the initial
> offgases). That zone migrates through the pile of biomass, heating mainly
> by radiation a small layer of biomass below the MPF, then with pyrolysis
> at a rather uniform temperature (generally from 450 to 700 C, depending on
> USER CONTROLED [sic] flow of primary air) to create the char as the gases
> move upward.
>
> The same also happens in a downdraft pyrolyser, and a bottom-pit updraft
> pyrolyser such as those produce by Hirendra Chakrabarti in India.
>
> The addition of a control feature makes the process variable, however it
> does not fundamentally change how the system works.
>
> >You may choose to try to equate the two descriptions above, but that
> would diminish your credibility as a precision-seeking scientist.
>
> There is no need for that kind of talk. First familiarise yourself with
> the systems under discussion. Seen from the side, an Adam Retort starts the
> MPF on the bottom right and it moves over a period of about 2 hours to the
> top left. Prof Lloyd can provide examples of sustained MPF?s moving
> horizontally underground in the Witbank area of South Africa without any
> addition of primary air. There are conditions where primary is required,
> and others when it is not. Tiny stoves require it.
>
> >And to equate a smouldering tree stump to MPF is a stretch beyond a
> stretch. Yes, there is fire there, and yes there is pyrolysis occuring.
> But such comparison is akin to saying that a ladybug and a moose are the
> same because both are living creatures; and in fact both are animals.
> Even a petunia and a whale are both living organisms. Scientific
> comparisons need precision and detail.
>
> That is why the discussion is on principles not ladybugs. A dry tree stump
> can be ignited to char the stump and the roots underground, and in the
> 1800?s one could buy a kit for doing so. I was told of a different method
> when I was young involving a steel pipe and kerosene. The point was to get
> the stump hot enough so that the pyrolysis would continue into the ground.
> The TLUD stove with an MPF is no more than a containerised version with
> controllable primary air.
>
> 2. Ron correctly pointed out that in normal operation of TLUD stoves,
> there is zero O2 that gets past the MPF. That is vastly different from
> having so much primary air enter (as in Rocket stoves and other burners)
> that there is O2 moving upward above the fuel (where the gases were
> created).
>
> Ron is correct about the O2. It is indeed different (I don?t know about
> ?vastly? from stoves where the fuel and flames are ?attached? to the solid
> fuel and the gases oxidise as and when they can. it is also true (but I
> didn?t expound on it) that within a fuel bed there are zones without no
> available O2, just as in the zone above the char.
>
> >You are saying that is good as preheated secondary O2.
>
> Functionally that is secondary air provided simultaneously, at least in
> some cases. My definitions are general cases and can be applied to the
> situation you describe.
>
> >Maybe, but not really. It is simply inadequate combustion, with the
> results of undesirable emissions.
>
> That is speculation and cannot be true in all cases.
>
> >The excessive primary air (which you state should be secondary air)...
>
> Which I state has the function of providing secondary air?
>
> >?has had a cooling effect on the raw fuel that the combustion is trying
> to get hot enough to give off the pyrolytic gases.
>
> That is not a general case. It could happen.
>
> >In other words, that secondary air that has passed over the fuel is part
> of the problem, not part of a solution because it has taken heat away from
> the fuel.
> That is not the case. What ?problem?? Heat passed through a metal wall to
> secondary air is not ?different heat? from that gained by air passing
> through a fuel bed, or along a hot combustion chamber wall. There are many
> roads to Rome. Air that is consumed after preheating is indifferent to hwo
> the heat was gained.
>
> >3. Tertiary air: Defined as either 1) the needed secondary air that
> did not get into the combustion zone soon enough (meaning that there was
> poor stove design)
>
> I see this as inaccurate on two counts: 1) the secondary air may be added
> in a way that decomposes complex gases further before final combustion, and
> 2) the bit about poor design is unfair comment. There are many good designs
> you may not know about.
>
> >?or 2) excess air that will lower the temperature of the hot gases
> (meaning that this "tertiary air" was NOT needed nor part of the combustion
> process).
>
> Tertiary air may be provided for a number of reasons, but normally to
> provide the oxygen needed to complete combustion with a desirable level of
> free O2 in the gases. Under certain circumstances, for example natural gas
> boilers, the level of free O2 is very low (1% by volume). To maintain such
> a low level of excess air it may be necessary to have tertiary or even more
> air injection points.
>
> >Either way, the concept of "tertiary air" is bogus in the context of
> cookstove combustion.
>
> That is opinion only, contradicted by existing technologies that use it.
> One of the highest performing stick-burning stoves available has tertiary
> air injection ? the Rocketworks stoves from Adrian Padt in Durban, tens of
> thousands of which are sold each year.
>
> >The objective is to get the combustion to be complete with the proper
> amounts of primary and secondary air at the correct times and places.
>
> That is true in some cases and not in others. Most Rocket stoves (per
> Aprovecho design guides) have only a single air entrance. The Rocketworks
> stoves have three distinct times and places.
>
> >4. You wrote:
> >>This [MPF} process is ... how the Terra Preta soils in the Amazon were
> created over 20,000 years of slash and burn agriculture.
> >The origins of Terra Preta are still being debated by the experts in that
> field, which is certainly not your claimed field of expertise.
>
> I am sorry to hear you talk about ?fields of expertise?. Facts in evidence
> speak for themselves and are not invalidated by any messenger claims.
>
> >>The Amerindians cultivated land that was already productive, they did
> not create it de novo. Cecil confirms they farm patches of land that are
> already productive, not random areas. He observed this when he was doing
> PhD field research while at Harvard.
> >I have great respect for Cecil Cook. But somehow what you have
> attributed to him and his work has not reach my attention previously.
>
> So what?
>
> >And I do not accept your statements.
>
> I don?t care. I cared to know, by interviewing him, how the Amerindians
> farmed and what role char had in their agriculture. I reported this
> previously to this list. Maybe you forgot. It is in the archives. At the
> time Ron replied that did didn?t accept the observational reports from
> Cecil who lived in the jungle for 4 years learning how their agricultural
> society functions.
>
> >What happened thousands of years ago was not witnessed by Cecil. He
> could only observe the current day activities on lands that somehow became
> fertile.
>
> He reported observations, the most important of which is that they do not
> practise slash and burn farming over whole areas, but only the fertile
> bits. The practice of slash and burning creates a lot of char in the
> ground, something contested by Ron at that time and diminished by your
> message regarding the tree stumps burning in California. If you don?t
> believe me, you can visit the area right now and witness the MPFs moving
> into the ground to charcoal the root systems. A major part of the work of
> firefighters is extinguishing these MPFs. This is sufficient to convince me
> they exist. If they exist, they are producing biochar in the ground.
>
> >You can take that topic to the Biochar Listserv, if you want to discuss
> it further.
>
> I have no interest in discussions on another list. I receive information
> from the Biochar-Ontario group.
>
> >Sorry, I reject much of what you wrote.
>
> Don?t be sorry. Learn and be happy! We are sharing perspectives here.
>
> >I would not want you to be instructing people about TLUD stoves and char
> making and Terra Preta.
>
> That is none of your business over which you have no control.
>
> >IMHO, your comments about pyrolysis in different devices reflect poorly
> on your credibikity [sic] regarding your other strongly expressed
> positions, but that is a topic for others to discuss.
>
> And I feel sometimes you could learn a thing or two before posting
> comments about other technologies. Like everyone else, I find your
> contributions worthy and partially correct.
>
> Perhaps there is something you could answer: Is there something about char
> making that requires or drives their proponents to make completely
> unnecessary personal attacks and derisive, inaccurate speculations about
> motives? Outside the agricultural sector and the production of
> char-enhanced fertilisers, I find the biochar enthusiasts as a group to be
> cloistered and fanatical, frequently engaging in divisive speech about
> something they have recently discovered.
>
> I should take a minute to compliment you, Xavier, Julien, Jonas Haller and
> Dr Nurhuda for being very open to exchange with me advice, explanations and
> observations without reservations about how or where the information
> originates. All of you have produced very interesting and effective
> products suited to certain communities.
>
> Best regards for a better burn
> Crispin
>
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> ------------------------------
>
> Message: 25
> Date: Sun, 10 Dec 2017 13:38:47 -0500
> From: alex english <aenglish444 at gmail.com>
> To: Discussion of biomass cooking stoves
> <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re:
> Bangladesh TLUD )
> Message-ID:
> <CA+6hwOopsxpxVpRx_dxD8u61W+oUNw7=9EmniYcUOw5dM29RBg at mail.
> gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Gordon,
> You may be asking for too much. Quality char and good combustion and an
> idle standby??....mans reach should exceed his grasp I suppose:)
> Alex
>
>
>
>
>
>
> On Sun, Dec 10, 2017 at 12:10 PM, Gordon West <gordon.west at rtnewmexico.com
> >
> wrote:
>
> > I would like to add some context to my interest in MPFs. I will also post
> > this on the biochar list, but as there is some relation to stoves I?m
> also
> > keeping it here.
> >
> > Our systems are designed to be community-scaled ?industrial?, and because
> > of that we have an interest in being able to modulate the pyrolysis
> > reaction down to ?idle? when heat is not needed, then to start it back up
> > on demand (in a continuous feed device, not a batch system). We have been
> > able to do this, but not in a reliably smooth manner. So it is very
> > important for us to understand the processes happening at the MPF in
> detail.
> >
> > One thing we know is that we can snuff the MPF by sealing off all
> external
> > inputs of air. In our experiments, a small quantity of air leakage, from
> > either the bottom through the biomass feedstock, or from the top coming
> > down through finished char, keeps the MPF hot enough to restart upon the
> > application of sufficient primary air. During idle it produces a small
> > amount of very foul smelling gas that is of insufficient density to burn
> on
> > its own. Seal off all air and the MPF snuffs completely within a short
> time
> > and the MPF cools below ignition temperature.
> >
> > Gordon
> >
> >
> >
> >
> > On Dec 10, 2017, at 9:41 AM, Gordon West <gordon.west at rtnewmexico.com>
> > wrote:
> >
> > Is there a report on monitoring an Adams retort MPF using thermocouples?
> I
> > am still not successfully visualizing the process.
> >
> > I did a bit of a search of technical reports on the chemistry of woody
> > biomass pyrolysis and have not yet found a reference to the release of O2
> > from heating the feedstock and its subsequent recombination with other
> > elements resulting in an MPF. Several analyses of syngas that I saw show
> > plenty of oxygen but it is bound in various fuel molecules.
> >
> > Gordon
> >
> >
> >
> >
> >
> > On Dec 10, 2017, at 9:04 AM, Crispin Pemberton-Pigott <
> > crispinpigott at outlook.com> wrote:
> >
> > Dear gordon
> >
> > You almost nailed it. Heating some small portion of the biomass and the
> > temperature of the nearby fuel (not all of it) is sufficient to ignite a
> > reaction that can continue indefinitely provided there is sufficient
> > insulation and the oxygen content of the fuel is sufficient.
> >
> > There are two approaches that will work, as I understand it: the first is
> > the charring of underground biomass (or coal) in the absence of
> additional
> > oxygen. Once started, it will continue until the fuel is exhausted.
> >
> > The other does not require heating, but uses compressed air (oxygen) to
> > provide the necessary reaction oxygen rapidly enough to get the reaction
> to
> > continue (the Hawaiian invention).
> >
> > An MPF is the front at which the heat releasing reaction takes place.
> >
> > You can also consider the way char is formed. In the initial stage the
> > energy needed to drive off the endothermic volatiles is more than the
> > energy released by oxidizing the gases using only the oxygen available in
> > the fuel. As the system heats up, the energy gap between evaporating
> > volatiles and exothermic reactions decreases. At some point, the gap is
> > small enough for the released oxygen to continue in the absence of
> > additional air.
> >
> > TLUDs are in general too small to see this take place. They cool off too
> > easily so additional air much be provided to sustain the reaction, which
> > burns the rest of the hydrogen and at least some of the carbon.
> >
> > An underground fire can continue for centuries. All it has to do is get
> > started. Prof Lloyd can explain how these fires can even auto-ignite. You
> > have probably heard of stacks of hay setting themselves on fire by
> > decomposition of the material in a large enough pile to retain the heat.
> > Once it reaches or exceeds about 290 C the reactions are exothermic and
> > from there it is a short trip to charging temperatures. The whole
> haystack
> > can turn to char save the cool exterior.
> >
> > Burning coal seams manufacture their own oxygen from water. Coal doesn't
> > have enough oxygen to sustain a pyrolytic front unless it is really hot.
> > But burn they do.
> >
> > You can determine if there is an MPF but putting in a set of
> thermocouples
> > and watching the front pass by. A burning log in an open fire has an MPF
> > inside working it's way to the centre. The whole log will be charred long
> > before it splits open.
> >
> > The interesting thing about a packed bed gasifier is that it can make gas
> > predictably and controllable from ?small sized fuel generally considered
> a
> > waste material. It is no small achievement.
> >
> > Regards
> > Crispin
> >
> >
> > I took a look at the Adams Retort design and watched a few videos. A
> > couple of questions come to mind:
> >
> > 1) How does one determine that an MPF exists in an A-R?
> >
> > 2) I am not much of a chemist, but I would be interested to see an
> > explanation of the reaction sequence where O2 is released and then burned
> > in the MPF of an Adams Retort.
> >
> > It seems to me that if the external heat source is raising the
> temperature
> > to the gasification point of the volatile components, thereby causing
> > gasification (duh?), what purpose is the MPF serving?
> >
> > In a TLUD the MPF is burning some of the volatile gases to generate the
> > heat needed to gasify un-pyrolyzed biomass.
> >
> > Gordon
> >
> >
> >
> > On Dec 9, 2017, at 10:54 PM, Crispin Pemberton-Pigott <
> > crispinpigott at outlook.com> wrote:
> >
> > Dear Paul
> >
> > *>*Some of what you wrote is correct, but you go too far or leave out
> > some important distinctions, thereby implying that some things are equal,
> > that is, some are not really as worthy and distinctive as others (Ron and
> > Paul) have stated.
> >
> > Of course there were things left out. I am happy you included below
> > further refinements to the explanation.
> >
> > >1. Pyrolysis progresses (migrates) through a piece or pile of biomass
> > as heat is able to penetrate. True. The Adam retort (and other
> retorts)
> > heat the biomass from many sides, but there is no flame (actual
> combustion)
> > inside. It is a stretch of language to say that the pyrolysis in the
> retort
> >
> > >>has an MPF [migrating pyrolytic front] proceeding in a roughly
> > horizontal direction.
> >
> > Au contraire. The Adam Retort (which heats the biomass from under a
> > portion of the bottom of the pile, not multiple sides) does indeed have a
> > MPF and the combustion is fed by oxidation using oxygen liberated by the
> > thermal decomposition of the fuel. There is no *added* oxygen, but oxygen
> > there definitely is. There is enough oxygen in biomass to almost
> completely
> > combust the hydrogen content. In practise the carbon and hydrogen are
> both
> > involved in sustaining the MPF. Once the fuel is hot enough, the MPF can
> > move through the pile without any additional heat required.
> >
> >
> > >Sorry, that should say "has external heating proceeding inward from
> > several directions from the sides toward the center."
> >
> > That is an incorrect description of the Adam Retort. There are retorts
> > that function in the manner you describe. His is not one of them.
> >
> > >Furthermore, the processes in a retort are in sequential order during
> > numerous minutes to 1) heat virtually all of the biomass to drive off the
> > moisture, then 2) add more heat to virtually all of the biomass to drive
> > off the low-temperature volatiles to create torrified material, and than
> 3)
> > to finally get the temperature hot enough to have actual pryrolysis,
> first
> > in the 400 deg C range and then at higher temperatures if the external
> > heating is continued.
> >
> > That is true for some retorts, not the Adams Retort.
> >
> > >In sharp contrast, in a TLUD there is a distinctive zone of a few cm
> > depth with actual small amounts of combustion (of some of the initial
> > offgases). That zone migrates through the pile of biomass, heating
> mainly
> > by radiation a small layer of biomass below the MPF, then with pyrolysis
> > at a rather uniform temperature (generally from 450 to 700 C, depending
> on
> > USER CONTROLED [*sic*] flow of primary air) to create the char as the
> > gases move upward.
> >
> > The same also happens in a downdraft pyrolyser, and a bottom-pit updraft
> > pyrolyser such as those produce by Hirendra Chakrabarti in India.
> >
> > The addition of a control feature makes the process variable, however it
> > does not fundamentally change how the system works.
> >
> > >You may choose to try to equate the two descriptions above, but that
> > would diminish your credibility as a precision-seeking scientist.
> >
> > There is no need for that kind of talk. First familiarise yourself with
> > the systems under discussion. Seen from the side, an Adam Retort starts
> the
> > MPF on the bottom right and it moves over a period of about 2 hours to
> the
> > top left. Prof Lloyd can provide examples of sustained MPF?s moving
> > horizontally underground in the Witbank area of South Africa without any
> > addition of primary air. There are conditions where primary is required,
> > and others when it is not. Tiny stoves require it.
> >
> > >And to equate a smouldering tree stump to MPF is a stretch beyond a
> > stretch. Yes, there is fire there, and yes there is pyrolysis occuring.
> > But such comparison is akin to saying that a ladybug and a moose are the
> > same because both are living creatures; and in fact both are animals.
> > Even a petunia and a whale are both living organisms. Scientific
> > comparisons need precision and detail.
> >
> > That is why the discussion is on principles not ladybugs. A dry tree
> stump
> > can be ignited to char the stump and the roots underground, and in the
> > 1800?s one could buy a kit for doing so. I was told of a different method
> > when I was young involving a steel pipe and kerosene. The point was to
> get
> > the stump hot enough so that the pyrolysis would continue into the
> ground.
> > The TLUD stove with an MPF is no more than a containerised version with
> > controllable primary air.
> >
> > 2. Ron correctly pointed out that in normal operation of TLUD stoves,
> > there is zero O2 that gets past the MPF. That is vastly different from
> > having so much primary air enter (as in Rocket stoves and other burners)
> > that there is O2 moving upward above the fuel (where the gases were
> > created).
> >
> > Ron is correct about the O2. It is indeed different (I don?t know about
> > ?vastly? from stoves where the fuel and flames are ?attached? to the
> solid
> > fuel and the gases oxidise as and when they can. it is also true (but I
> > didn?t expound on it) that within a fuel bed there are zones without no
> > available O2, just as in the zone above the char.
> >
> > >You are saying that is good as preheated secondary O2.
> >
> > Functionally that is secondary air provided simultaneously, at least in
> > some cases. My definitions are general cases and can be applied to the
> > situation you describe.
> >
> > >Maybe, but not really. It is simply inadequate combustion, with the
> > results of undesirable emissions.
> >
> > That is speculation and cannot be true in all cases.
> >
> > >The excessive primary air (which you state should be secondary air)...
> >
> > Which I state has the function of providing secondary air?
> >
> > >?has had a cooling effect on the raw fuel that the combustion is trying
> > to get hot enough to give off the pyrolytic gases.
> >
> > That is not a general case. It could happen.
> >
> > >In other words, that secondary air that has passed over the fuel is part
> > of the problem, not part of a solution because it has taken heat away
> from
> > the fuel.
> >
> > That is not the case. What ?problem?? Heat passed through a metal wall to
> > secondary air is not ?different heat? from that gained by air passing
> > through a fuel bed, or along a hot combustion chamber wall. There are
> many
> > roads to Rome. Air that is consumed after preheating is indifferent to
> hwo
> > the heat was gained.
> >
> > >3. Tertiary air: Defined as either 1) the needed secondary air that
> > did not get into the combustion zone soon enough (meaning that there was
> > poor stove design)
> >
> > I see this as inaccurate on two counts: 1) the secondary air may be added
> > in a way that decomposes complex gases further before final combustion,
> and
> > 2) the bit about poor design is unfair comment. There are many good
> designs
> > you may not know about.
> >
> > >?or 2) excess air that will lower the temperature of the hot gases
> > (meaning that this "tertiary air" was NOT needed nor part of the
> combustion
> > process).
> >
> > Tertiary air may be provided for a number of reasons, but normally to
> > provide the oxygen needed to complete combustion with a desirable level
> of
> > free O2 in the gases. Under certain circumstances, for example natural
> > gas boilers, the level of free O2 is very low (1% by volume). To maintain
> > such a low level of excess air it may be necessary to have tertiary or
> even
> > more air injection points.
> >
> > >Either way, the concept of "tertiary air" is bogus in the context of
> > cookstove combustion.
> >
> > That is opinion only, contradicted by existing technologies that use it.
> > One of the highest performing stick-burning stoves available has tertiary
> > air injection ? the Rocketworks stoves from Adrian Padt in Durban, tens
> of
> > thousands of which are sold each year.
> >
> > >The objective is to get the combustion to be complete with the proper
> > amounts of primary and secondary air at the correct times and places.
> >
> > That is true in some cases and not in others. Most Rocket stoves (per
> > Aprovecho design guides) have only a single air entrance. The Rocketworks
> > stoves have three distinct times and places.
> >
> > >4. You wrote:
> >
> > >>This [MPF} process is ... how the Terra Preta soils in the Amazon were
> > created over 20,000 years of slash and burn agriculture.
> >
> > >The origins of Terra Preta are still being debated by the experts in
> > that field, which is certainly not your claimed field of expertise.
> >
> > I am sorry to hear you talk about ?fields of expertise?. Facts in
> evidence
> > speak for themselves and are not invalidated by any messenger claims.
> >
> >
> > >>The Amerindians cultivated land that was already productive, they did
> > not create it *de novo*. Cecil confirms they farm patches of land that
> > are already productive, not random areas. He observed this when he was
> > doing PhD field research while at Harvard.
> >
> > >I have great respect for Cecil Cook. But somehow what you have
> > attributed to him and his work has not reach my attention previously.
> >
> > So what?
> >
> > >And I do not accept your statements.
> >
> > I don?t care. I cared to know, by interviewing him, how the Amerindians
> > farmed and what role char had in their agriculture. I reported this
> > previously to this list. Maybe you forgot. It is in the archives. At the
> > time Ron replied that did didn?t accept the observational reports from
> > Cecil who lived in the jungle for 4 years learning how their agricultural
> > society functions.
> >
> > >What happened thousands of years ago was not witnessed by Cecil. He
> > could only observe the current day activities on lands that somehow
> became
> > fertile.
> >
> > He reported observations, the most important of which is that they do not
> > practise slash and burn farming over whole areas, but only the fertile
> > bits. The practice of slash and burning creates a lot of char in the
> > ground, something contested by Ron at that time and diminished by your
> > message regarding the tree stumps burning in California. If you don?t
> > believe me, you can visit the area right now and witness the MPFs moving
> > into the ground to charcoal the root systems. A major part of the work of
> > firefighters is extinguishing these MPFs. This is sufficient to convince
> me
> > they exist. If they exist, they are producing biochar in the ground.
> >
> > >You can take that topic to the Biochar Listserv, if you want to discuss
> > it further.
> >
> > I have no interest in discussions on another list. I receive information
> > from the Biochar-Ontario group.
> >
> > >Sorry, I reject much of what you wrote.
> >
> > Don?t be sorry. Learn and be happy! We are sharing perspectives here.
> >
> > >I would not want you to be instructing people about TLUD stoves and char
> > making and Terra Preta.
> >
> > That is none of your business over which you have no control.
> >
> > >IMHO, your comments about pyrolysis in different devices reflect poorly
> > on your credibikity [*sic*] regarding your other strongly expressed
> > positions, but that is a topic for others to discuss.
> >
> > And I feel sometimes you could learn a thing or two before posting
> > comments about other technologies. Like everyone else, I find your
> > contributions worthy and partially correct.
> >
> > Perhaps there is something you could answer: Is there something about
> char
> > making that requires or drives their proponents to make completely
> > unnecessary personal attacks and derisive, inaccurate speculations about
> > motives? Outside the agricultural sector and the production of
> > char-enhanced fertilisers, I find the biochar enthusiasts as a group to
> be
> > cloistered and fanatical, frequently engaging in divisive speech about
> > something they have recently discovered.
> >
> > I should take a minute to compliment you, Xavier, Julien, Jonas Haller
> and
> > Dr Nurhuda for being very open to exchange with me advice, explanations
> and
> > observations without reservations about how or where the information
> > originates. All of you have produced very interesting and effective
> > products suited to certain communities.
> >
> > Best regards for a better burn
> > Crispin
> >
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--
Norbert Senf
Masonry Stove Builders
25 Brouse Road, RR 5
Shawville Québec J0X 2Y0
819.647.5092
www.heatkit.com
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