[Stoves] Emissions issues (B) with TLUD and Flame Cap devices (that make char) FW: Flame cap on top of finished TLUD pyrolysis

[Anderson, Paul]

Dear Stovers and Charists,   This is message    (B)

I am sending TWO messages (A & B with this same introductory comment) about emissions from char-making devices, specifically Flame Cap (FC) and TLUD.  The messages are long and unfortunately were not on any Listservs, and were with Paul Taylor (Paul T, not to be confused with Paul A.).   Paul T. is today on his way back to Australia.   We spoke before he left.   Here are the main issues:

1.  Paul  T. is working with several co-authors (Hans-Peter Schmidt and others) to finalize a paper about emissions from char-making devices.  They would like some additional data (probably already collected, but not in their hands yet, so please consider sharing, with appropriate recognition for your work.)

2.  A major issue is the emission of methane from FC and TLUD char-making devices.  Paul T. is mentioning how important methane emissions are.   And I was saying that stove testing has NOT been measuring methane.  Who has measured it?   (Jim Jetter????)  Is methane release from FC devices so high (when new fuel is added, there are spikes of emissions) that it virtually negates the carbon-negative advantages of sequestering biochar that is made by FC devices.   And by inference, does  that also apply to biochar made by TLUD devices, noting that new fuel is NOT added and the spikes do not occur in the batch process of TLUD devices larger or small.

Comments are welcome on each separate Listservs, with appreciation of efforts to share as private forwards to  those who are on only one or neither of the Listservs.  Please distinguish between Paul T. and Paul A. when making statements.  Paul A. is assisting.   Paul T. is the main person raising the issues.

Paul A.

Doc / Dr TLUD / Paul S. Anderson, PhD
Exec. Dir. of Juntos Energy Solutions NFP
Email:  psanders at ilstu.edu<mailto:psanders at ilstu.edu>       Skype:   paultlud
Phone:  Office: 309-452-7072    Mobile: 309-531-4434
Website:   www.drtlud.com<http://www.drtlud.com>

From: Paul Taylor <potaylor at bigpond.com>
Sent: Friday, December 21, 2018 8:21 PM
To: Anderson, Paul <psanders at ilstu.edu>
Subject: Re: Flame cap on top of finished TLUD pyrolysis

Communication with Hans-Peter re Email thread with Norm:

Dear Paul,  [meaning Paul T.]
your letter to Norm should be considered a piece of modern biochar history. Let's publish it and maybe extend it a bit for tBJ. We were proud for having brought the Kon-Tiki to > 80 countries but you are so right to point it out that it starts to become a burden to the environment and even the users itself. We have a responsibility of warning now and we should do it insistently based on the new paper to be published soon.
Yours Hans-Peter

Dear HP:  I certainly don't give up on the KT, and it provides a wonderful teaching tool that we need, and can use in our paper.
However, as their use expands beyond that, we have to be realistic in how people will actually run them, and calculate from there. We have to think like the Biosphere;  the biosphere cares nothing for how we deceive ourselves, but responds accurately to the inputs we actually provide.  There may be ways in some subsystems where the response is beneficial, if we can be careful enough.
If its useful I can collate it into tBJ article, as you advise, and it may provide some content for our paper.

=======================

Email thread with Paul Anderson re operations and emissions from TLUDs, Flame cap and hybrid kilns
Flow is from bottom email initiated by Paul Anderson.

Hi Paul [A.]:  Duel TLUD - Kon-Tiki mode runs a full TLUD - perhaps 90% full down to 40% full.  Then the flame cap mode is run on top of that, with the advantage of an already prepped ember and flame bed.

I have experimented with empty 1/2 and 2/3 200L drums and they will run in Kon-Tiki mode with effective vortex, bottom flooding and draining etc.  The Kon-Tiki specialization of the flame cap is focused on optimizing the inwardly rolling vortex in the kiln, which is driven by updraft outside the hot walls and by up-drafting combustion products above the kiln. The size of the vortex roll is half the diam of the drum, so about 28cm

The vortex brings air down into the center of the kiln in a strong downdraft, and momentum and suction drives it to the fresh fuel layer. The vortex also brings pyrogas up the walls for mixing with secondary air. Unburned smoke is rolled back down again for another loop.  Thus the vortex provides both PA for the pyrolysis in the depth of the kiln, SA for clean combustion, and also mixing of fuel gas and air.  It is self-regulating because the faster fuel is added (provided not so fast it quenches/cools/wets the flame), the stronger the convections and the stronger the vortex; the flows of PA and SA regulate accordingly.  My quantitative studies showed that these convection dynamics naturally provide sufficient PA for gasifying the wood, and SA for above stoichiometric (excess air) combustion.

This will work beautifully in an empty half drum or 2/3 drum. It helps to build a proper open rick pyre in the drum so it can be top lit at rim height; and any Kon-Tiki starts running better and faster as the fuel and heat builds up and the vortex becomes stronger.  However if the bed of embers is already created at 40% of full drum height at the end of a TLUD run then the vortex is already operating fully due to hot walls, hot embers and updraft.  This was illustrated in our first Kon-Tiki trails in 2014 by smoke-stick studies, and in a rectangular box/trough kiln quenched from above.  In the copious steam the inwardly rolling vortexes were extant on all side of the box, even though the char and steam temperature was only about 100C (video on my website).  These vortexes will be operating in a sufficiently sized TLUD in TLUD mode, provided combustor superstructure does not intrude into the natural vortex zone.

This also relates to why superstructure above a Kon-Tiki, such as a hood, if not carefully placed, will impede the self-regulating vortex and deteriorate operation and emissions.  The operation, safety and emissions of a KT can be refined with superstructure, it just must be designed carefully, and quite often will not be worth the expense except when safety and regulatory issues intrude.

I hope that better explains. The flame cap mode on a TLUD is not something that interferes with TLUD operation, which is run from full fuel load to completion and close-off of PA; and is not just throwing a bunch of fuel into the drum at any point.  Its a sequential operation involving full loading and complete running of a TLUD, followed by watchful management of the fuel entry and flame cap in the flame cap mode, and at least for me always striving to keep alive the friendly vortex.  The starting of the flame cap operation is shaky in an empty 200L drum, without bottom supply of air, but there is no start up at all in the duel operation.  At the end of TLUD operation (which replaces the start up) just start layering in the material at a size and rate suitable to maintain and grow a full flame cap (closing the TLUD PA, and adjusting TLUD superstructure if in the way).

Paul [T.}
--
Paul Taylor, PhD
Ed/Author: The Biochar Revolution
Transforming Agriculture and the Environment
http://www.thebiocharrevolution.com
http://www.ithaka-institut.org/en
http://www.biochar-journal.org/en
Phone, US: 1-415-233-7366
Skype: potaylor




On 12/4/18, 10:52 AM, "Anderson, Paul" <psanders at ilstu.edu> wrote:
Dear Paul T.,

Thank you for that clarification.   Very useful.   I agree with all, especially about flame-cap mode not being very applicable to the stove-size TLUDs, because of smaller diameter and, if being used with the concentrator lid, the lid itself can prevent the flame-cap from being close enough to the newly added fuel.

About the barrel size units, your experiences with Norm are enlightening.   As you say, in normal TLUD function, the barrel becomes approximately 40% full of char.   The empty top 60% means that the newly added fuel will be a considerable distance below the upper rim over which the air for flame-cap operation must pass.  It is flame CAP, not requiring the air (or much of it) to actually reach down all the way to the new fuel.

I would imagine that a 200 Liter barrel that is only 50% filled with fuel for TLUD operation would end up with only 20% of the bottom of the barrel with char.   That increased distance (80% of the barrel height) might just be too great for the flame cap to function.   That would be an interesting experiment, but only as an experiment because nobody is advocation TLUDs only half filled at the start.

Paul A.


Doc / Dr TLUD / Paul S. Anderson, PhD
Exec. Dir. of Juntos Energy Solutions NFP
Email:  psanders at ilstu.edu <mailto:psanders at ilstu.edu>        Skype:   paultlud
Phone:  Office: 309-452-7072    Mobile: 309-531-4434
Website:   www.drtlud.com<http://www.drtlud.com> <http://www.drtlud.com>


From: Paul Taylor <potaylor at bigpond.com>
Sent: Tuesday, December 4, 2018 1:29 PM
To: Anderson, Paul <psanders at ilstu.edu>; Norman Baker <ntbakerphd at gmail.com>; Kirk H. <gkharris316 at comcast.net>
Cc: Julien Winter <winter.julien at gmail.com>; biocharFIRST <wmknauss at gmail.com>; Art Donnelly <art.donnelly at gmail.com>; Vi Rapp <VHRapp at lbl.gov>; Dean Still <deankstill at gmail.com>; Ron Larson <rongretlarson at comcast.net>; jg45 at icloud.com; Ryan Thompson <ryan at mtnaireng.com>; Jarod Johnson <jjohnson0423 at hotmail.com>; Dave Lello <dave at lello.me>; Erin Peiffer <epeiffer1 at udayton.edu>
Subject: Re: Flame cap on top of finished TLUD pyrolysis

HI Paul A.: I was not intending to include stove operation in my point about flame cap operation after completion of a TLUD cycle.

A dual operation of a stove may also be of value, but requires those additional explorations you raise, partly because of the different geometry in small stoves. The question of how small the device can be relates most to convection/combustion dynamics, providing that fuel is sized and fed appropriately for vessel - it is not all added at once, so it is pyrolyzed piece by piece. Small SS funnels have been run in flame cap mode.

A Kon-Tiki mode operation (which is a flame cap device that is optimized for vortex convection dynamics, efficiency, ease of use, and nutrient quenching of the produced char) has been explored in terms of parameters of vessel size and geometry, feed rate etc, although I have not published my own work.  The vortex has a size determine by the properties of the air, and for effective vortex the vessel diameter is better above 50cm, and better with steeper walls, and improved with convection-designed heat shield.  That relates well to a 55g drum sized TLUD.

While a smaller diameter TLUD could be converted to flame cap operation it will operate less well in the vortex mixing mode, which will likely be also interfered with by the TLUD after-burner geometry.  That may be compensated for because stove TLUDs are being developed with sophisticated Natural Draft air control, which can be further refined to serve in flame cap mode as well.

The beauty of the Kon-Tiki is that the convection driven vortex provides both primary and secondary air for the pyrolysis and combustion, and the mixing of pyrogas and air, in an elegant, simple, self-regulating way.  The operation is open to view and the job is to manage and regulate the fuel increments.  A drum TLUD lends itself to continuation in that mode after closing off the primary air.

Another advantage of the dual operation (in the drum TLUDs I work with) is that it removes the dilemma of when to close off primary air and extinguish the TLUD.  TLUDs often don't operate ideally, so additional time is needed to carbonize stranded incompletely-carbonized biomass.  Norm and I solved this problem in the drum by doing a wet-carpet snuff and closing the vessel, thus  providing an anoxic environment and time for completion of carbonization in the dry red-hot char. We experimented with flaring at a small hole any further pyrogas produced (like in a pressure cooker hole - and we could also observe this at our thermocouple holes).

In duel operation, after the primary air is closed off, when the migratory pyrolysis front reaches the bottom, further carbonization can continue in the TLUD char, safely preserved in the bottom half of the vessel, while flame cap operation takes over in the top half fed by incremental fuel additions.  Further pyrogas evolved from the TLUD char in the bottom half is burned in the flame cap, so no smoky end at that point.

Generally a flame cap, at least in a Kon-Tiki, can be managed to avoid any smoky end, although there may be increased CO emissions.  Emission measurements do show very clean operation of a flame cap in a Kon-Tiki, marred intermittently by the disturbance of the flame cap which tends to occur when a piece of fuel is added.  Areas of quenched flame will lead to bursts of methane and particulate emission, which increase the time average emission readings, so, yes, the fuel introjections must be managed with awareness and understanding - as  most things must in our interconnected world.

Again, the transfer of this experience to TLUD stoves is not automatically of value because stoves have a primary purpose as cooking appliance, and economic, convenience, emission and cultural parameters enter on top of convection geometries and volume of char production.  In a drum TLUD it is clearly a potential benefit for all the reasons mentioned above and below. The goal in this case is clean convenient, economic bulk char production.  Some work and money goes into creating an effective, low-emission, convenient drum-sized TLUD, as Norm and I pursued.

A 200L drum TLUD produces about 80L of char, and when run in dual mode it can produce 180L, making more effective use of the machine and time capital.  That being said, routine "commercial" operations of TLUDs may rather forgo those benefits for simplification of routines and controls - just run more TLUDs at 40% vessel-volume efficiency!

Paul T.

On 12/4/18, 6:26 AM, "Anderson, Paul" <psanders at ilstu.edu> wrote:
To Paul T. and Norm and all,

What you wrote is very well stated about having a flame cap operation in a TLUD that has finished the pyrolysis of the migratory pyrolytic front (MPF).   It should be explained that well to everyone who works with or uses TLUD stoves.

A key part of that explanation is the statement:
>Running a TLUD to completion, then closing off the primary air and converting to flame cap mode

Without entry of more primary air (which comes in at the bottom), there is no loss of created charcoal.

When the primary air is left open, it is less clear that flame cap functions occur, or to what degree.  But closing the primary air makes the issue clear.

Research questions relate to how small of diameter (and for a specific fuel type) of the fuel container can the TLUD have and still have sufficient heat from the flame cap to cause the pyrolysis of the new fuel on the top of the non-burning charcoal.  Ambient temperature, wind, insulation, the entry of the "flame-cap-air" coming through the secondary air passages (vs. over an open top), and other factors could be significant.   One factor would be if the TLUD is ND or FA.

The questions also relate to whether the flame cap operation is for char making only or is also for having a cooking fire (which sets additional expectations).   For char making, this makes sense.   For cooking, there could be some issues.

Also, it is important to remember that a TLUD device has the ability to let additional air enter via the primary air inlet (and/or it could have leaks).  That would allow for some controlled amount of char-burning that might be crucial for maintaining sufficient heat above for the new fuel to pyrolyze.  Questions include:  what is the NET gain (or loss) of char?

Needed to be said also is that the new fuel on top needs to be added at an appropriate rate (interval and amount), and there is no known research about that rate, as far as I know.  We are at the interface of TLUD and Flame Cap technologies.

Paul A.

(Sometimes Norm (who has worked considerably with Paul Taylor) attributes things to   Paul   and even I am not sure if he means Paul A. or Paul T.    Paul T. has done major work with TLUD technology and should be appropriately recognized.)


Doc / Dr TLUD / Paul S. Anderson, PhD
Exec. Dir. of Juntos Energy Solutions NFP
Email:  psanders at ilstu.edu <mailto:psanders at ilstu.edu>        Skype:   paultlud
Phone:  Office: 309-452-7072    Mobile: 309-531-4434
Website:   www.drtlud.com<http://www.drtlud.com> <http://www.drtlud.com> <http://www.drtlud.com>


From: Paul Taylor <potaylor at bigpond.com>
Sent: Tuesday, December 4, 2018 1:23 AM

Subject: Re: Dates for TLUD Summit

Running a TLUD to completion, then closing off the primary air and converting to flame cap mode can preserve the TLUD char and continue to make biochar until the reaction vessel is filled.  This maximizes use of the volume of the vessel, and its heat shield if any, makes the device easy to start in the TLUD mode (primary air supply) and easy to continue in the flame cap mode (a nice base of coals and heat).  The vessel-shield-combustor-chimney arrangement of the hybrid can be optimized for the duel use, to exploit the natural convection flows that are exemplified in the Kon-Tiki, and to allow access to load fuel.  We discussed this while developing the ring of fire.  Those convection dynamics in fact provide insight to optimize some aspects of secondary air supply and mixing in a straight TLUD.

Paul


On 12/3/18, 9:40 AM, "Anderson, Paul" <psanders at ilstu.edu> wrote:

Norm, at another meeting last week (at Univ of Dayton), the presence of a flame cap in a TLUD stove was mentioned.   I see the two as being distinctly separate.   The presence of a flame above some biomass (sometimes a goodly distance above a layer of charcoal that covers the lower biomass) does not function in the same was as a flame cap in the sense that it is used (by Kelpie Wilson and others).    You may present your reasoning, but expect at least me to challenge that usage of the flame cap explanatory name.

Paul

Doc / Dr TLUD / Paul S. Anderson, PhD
Exec. Dir. of Juntos Energy Solutions NFP
Email:  psanders at ilstu.edu <mailto:psanders at ilstu.edu>        Skype:   paultlud
Phone:  Office: 309-452-7072    Mobile: 309-531-4434
Website:   www.drtlud.com<http://www.drtlud.com> <http://www.drtlud.com>  <http://www.drtlud.com> <http://www.drtlud.com>




-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20181222/75a48d80/attachment.html>