[Stoves] Understanding what TLUD means.... was Re: stoves and credits again

Sat Sep 30 14:00:24 CDT 2017

Dear Paul

>"TLUD" is the combustion processes associated with the Migratory Pyrolytic Front  (MPF). that creates the pyrolytic gases and leaves charcoal behind.  That does not change.  The other features of a "stove device" can be and are diverse.  And that is where we can find all of the variations that you mention.

I disagree at a fundamental level, and gave it some thought today before your message arrived. A TLUD means top lit and updrafting air flow. Nothing more. There are many stoves that operate in this fashion, and as I said before, I was taught this as a way to light low-smoke Boy Scout jamboree fires.

Having a pyrolytic front is something available to several modes of burning. The MN4.1 described a few days ago has a migrating pyrolytic front and is a crossdraft stove, with moving fuel! In fact the pyrolytic front itself remains pretty much in the same physical location, as the fuel moves down and forward under the gas burning zone. TLUD is not the only way to create such a zone. A downdraft gasifier also has a moving pyrolytic front, and if built well, it also remains in about the same position while the fuel moves downwards through the grate.

>If a stove COULD successfully operate with the MPF, it could be called a TLUD stove even if it can also be operated in other ways.

This is clearly no the case for downdraft stoves and cross draft stoves that operate continuously with a migrating pyrolytic front. The MN4.1 is not a TLUD. A SDC-1 is.

>But if it COULD be with the MPF, but if it is mostly NOT being used with the MPF, calling it a TLUD gasifier stove is misleading.

I disagree again no a definitions basis. A TLUD is a fire and air flow definition. A MFP is something that may or may not be seen – depending on how it is operated. John Davies’ packed bed gasifier had three things going on, had an MFP and a BLUD coke burning stage, but also could operate as a full-fuel burning gasifier.

Any TLUD that produces gas for combustion in a zone above is a gasifier. It does not have to produce char at all, because a char-making gasifier is a sub-set of all gasifiers.

>From my limited following of on-going Rocket stove designs and production, the shelf with associated tip-burning is often absent (by manufacturing or by user removal) but the name is still Rocket stove.  That is unfortunate, in part because the Rocket advantages are absent and should not be claimed by the different stove.

Well, that raises a question answered by Dean Still on this list some years ago. What is a Rocket Stove? He replied that it is any stove that incorporates all their design advice and features, with an emphasis on there being certain dimensional ratios involved. He was delineating a line between stoves claimed by be ‘rocket stoves’ in Uganda and those that were ‘real’ rocket stoves. I have to accept his definitions as he is leading that particular group of designs. A ‘rocket stove’ has a an elevated fuel shelf and no grate. That is why I frequently say that any (real) rocket stove can be improved by adding a grate, as per the Namibian Tso-tso or similar.

>I do not want the TLUD distinctiveness to be claimed if the MPF is not an active part of the operation  of a stove that claims to  be a TLUD.

Then you will have to create a new name that does not interfere with normal classification and terminology. A TLUD as you have created them, is a sub-set of TLUD’s. There are TLUD gasifiers made in Turkey that have not changed in design since 1959. Your definition does not include them because they are char-burning.

At a fuel-particle level, all fires have a MPF so you may have to think of some other way to characterise that particular sub-set of stoves you want to promote. Trying to ‘corner the name’ for a sub-set will not fly because there are other TLUD’s. I think it should be adequate to call them char-making TLUDs.

>Example:   If you filll a TLUD-capable fuel chamber with charcoal, there canNOT be a MPF.   Why?   Because there is no pyrolysis.

This is imply incorrect. There is pyrolysis of the carbonaceous. Would you like to see such a stove burning? The fuel burns down with a migrating pyrolytic front that leaves, for example, only half of the fixed carbon (pure coke) and burns off the volatiles, all the volatile carbon, and half the fixed carbon. If you track the temperature as the front moves down, it will behave exactly like one that burns at a lower temperature that makes char.

This is very easy to demonstrate. There are literally hundreds of Chinese semi-coked briquette burning TLUD stoves that operate in this manner, often used for heating water to go to radiators. They are extremely clean-burning and leave only ash at the end of the burn. They often produce less than 2 mg of PM2.5 per MJ delivered into the water.

>The fuel is ALREADY charcoal.   That operation might be driving off some  volatiles that then move upward, but that is not pyrolysis.

Please read what pyrolysis means:
++++++++++

1.    py·rol·y·sis
[pīˈräləsəs]<javascript:void(0)>
NOUN
1.     chemistry
decomposition brought about by high temperatures.
++++++++++
It says nothing about making char from an uncharred fuel. It is thermal decomposition. Coke or charcoal or even graphite can be decomposed by heat. Doing so continuously means it can be useful.

>Note:  TLUD is an acronym for "Top-Lit UpDraft".   But the acronym is now a distincitive name in its own right.

No, you have claimed to have this be so without perhaps thinking through the implications for hundreds of models of stove already on the market. The thermodynamics people who deal with combustion and write textbooks about it have described all sorts of things like this. Is there anything new on the market?  Charcoal makers in centuries past knew how to make a MPF to their advantage. Suddenly, it is different because it is done on a small scale? On what grounds? The Franklin pot-bellied stove patented in 1742 has an MPF in that is halfway between the 1688 downdraft MPF and the MN4.1 crossdraft, which is itself based at least conceptually on a common German ‘egg brick’ burning furnace.

>And it is associated with the MPF and with dry biomass fuels.   If some other process has ignition at the top and has upward moving air flows, it can have any name you want to give it, but not the name TLUD.

Both of these are not tenable statements. Combustors are first characterised by the ignition point, then the airflow direction, then the operating conditions such as MPF or other descriptor. The pyrolytic updraft gasifiers made by Hirendra Chakrabarti are biomass-burning top-lit, top loaded, updraft pyrolytic char-making gasifiers with an MPF that never reaches the bottom of the chamber. They make a very wet, high energy gas.

Anton Soedjarwo makes a biomass-burning bottom lit, down-draft, top-loaded, fluidised bed gasifier that produces zero char – nada! It also has a MPF that is dragged downwards and never reaches the top of the fuel charge.

An 8-tons-per-day Indian micro-cement plan is a top-lit, updraft, top loading, combustor that makes no combustible gas, has a MPF that is dragged down by the fuel and rises by the combustion of fuel. It burns coke at the bottom, semi-coked material in the middle, and pyrolyses at the top, with a lot of reduction (burning with oxygen) within the material above that is getting heated. In several respects this is akin to Hirendra’s gasifier except that he draws off the gas instead of applying the heat to the decomposition of limestone.

>As a rather absurd example, if there is a "Lignin Powered Gasifier" stove, it should not be called an LPG stove.

It would be a misprepresentative statement if it was not made clear that in that case LPG meant “lignin”.  In fact LP Gas stoves are often called that, rather than LPG stoves by the LP Gas association. Check and see if I am right.

>That would be misleading, would be false, and could probably cause some law suit from the big business of LPG.

They do not call themselves the LPG Association.
http://www.j-lpgas.gr.jp/en/about/
http://www.lpgasmagazine.com/category/national-propane-gas-association/
http://nigerialpgas.com/
http://propane.ca/quick-facts/
http://www.lpgasmagazine.com/tag/texas-propane-gas-association/
https://www.wlpga.org/event/international-lp-gas-seminar-tokyo/

>I doubt that LPG is a registered trademark, but misuse of those letters would cause trouble.

You cannot get into trouble using an unregistered trade mark.

If you want a unique identifier for biomass-burning char-making TLUDs like CharM-TLUDs.

Regards
Crispin

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