[Stoves] Designation of TLUD gasifier devices.

Crispin Pemberton-Pigott crispinpigott at outlook.com
Mon Sep 21 00:50:46 CDT 2015


Paul

 

You just can't just make stuff up.

 

We talked about this years ago and the direction of gas flow is the first
categorisation of devices. If you have included in your book that a TLUD
which does not separate gas combustion from the gas generation is not a
TLUD, even if it is, you will have to change the book. 

 

You can easily have a bottom lit downdraft stove that is not a gasifier. You
can just as easily have one that is - depending on whether there is a
pyrolysis zone that is very short of air and is creating gas at a rate that
it cannot burn within the fuel bed. The gas escapes and burns below the
grate. 

 

Wood can be burned in both modes in a downdraft fashion. It can just as well
burn upwards in both modes. The difference between them is related to the
air flow and O2 availability in the gas generation zone, do you agree?  Tom
Reed proposes that the superficial velocity of the air dictates whether the
system is a pyrolyser or a gasifier.

 

'Any old fire' is not a characterisation of gas flow direction or the
separation of generation from final combustion.

 

I would hold that there are three states: TLUD burning, TLUD gasification,
and TLUD pyrolysation. Exactly the same divisions can be made for cross
draft and downdraft combustors.

 

To my surprise I found out from Hirendra in India that he is making BLUD
gasifiers - lots of them, and big too. I had never heard you talk about this
layout. The fire is on the bottom and the MPF is rising through the fuel,
the flow of air and gases is upwards. The fuel is continuously added from
the top, and the ash is removed from the bottom. It runs continuously 24/7.

 

That is clearly a BLUD gasifier, as it does not produce charcoal so it is
not a pyrolyser. Do I have that correct? I am following your lead on this.
It is not a TLUD and it is refuellable which is a very big deal.

 

It means you could be having a micro-gasifier that is refuellable (from the
top or just to the side), while creating gases that rise to a combustor
above the top - clear separation from the gas generation zone. It does not
have a hot char zone through which the gases rise. How is it we have not
heard this system being described here before? He has been making them for
years.

 

Regards

Crispin

 

 

Dear readers,

 

All readers are advised that some people insist on using a valid GASIFIER
term of TLUD when referring to other types of fires because there is
ignition at the top of a fuel pile and the air flow is 

upward.   And they do this without regard to the GASIFIER structure that 

allows the creation of the gases to be separate in time and space from 

the burning (or other usage) of the created gases.   The creation and 

the burning of the gases can be very close, but they CAN be separated.   

For example, the top flame (the secondary combustion) can be extinguished in
a TLUD gasifier (but not in just any old bucket or open fire).

 

Paal Wendelbo observed the Norwegian resistance fighters having top 

lighting of open campfires, and they were not using gasifier devices.   

40 years later he contained that pyrolysis and gas burning processes inside
metal cylinders and had the start of what is today called TLUD gasifiers.

 

Today, after 30 years of development of TLUD stoves and other true
micro-gasifiers that now have respectable recognition, it is becoming trendy
to call other things TLUDs when they are not or are mere shadows 

of what is involved with gasifier stoves.   There are no "terminology 

police" or copyrights on TLUD.   Readers need to be aware of the details 

of the actual operations, regardless of what it is being called.

 

Readers are encouraged to use as a reference the book on
Micro-gasification.... by Christa Roth (GIZ publisher) and my article
"Micro-gasification Terminology...", both of which are available in the 

Quick Picks list on my website    <http://www.drtlud.com> www.drtlud.com

 

I did not invent TLUD gasifiers, but I did give them that name 10 years 

ago.   People can use the words top lit and up draft to describe other 

things, but the acronym TLUD should appropriately refer to a reasonably well
defined TYPE OF GASIFIER DEVICE, most specifically as a cookstove or
char-maker.  Use of that TLUD designation for other devices is a form of
mimicry and getting on a bandwagon, or worse, which is just to make
confusion.

 

Dr TLUD

 

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