[Stoves] Bangladesh TLUD (was Re: No subsidies in TLUD char peoduction

Sat Dec 9 21:03:21 CST 2017

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: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<https://eur03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.drtlud.com%2F&data=02%7C01%7C%7C2f4e87e571974e97b4cf08d53f3a03ae%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636484440759723211&sdata=%2F0G0WITanc4Qcg1Y7PLykyHh5m8pqwgSmbrNqKAMRT4%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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