[Stoves] Understanding TLUDs, MPF and more. (was Re: Bangladesh TLUD )

[Crispin Pemberton-Pigott]

Dear Frank

The charts provided to the thermogrametric analyser results show that the partial decomposition of the biomass is exothermic, and that there is a large spike in heat released at 360 C. Some of the gas production (distillation) you are witnessing is driven by that heat. If it cools rapidly, that heat is lost and there is no more fuel to convert. Above that temperature the gas production is driven by external heat.

So the answer is part and part, if the biomass is not well insulated. Given enough insulation, the biomass not only self-pyrolyses, it can experience thermal runaway as the heat released is more than the heat needed to pyrolyse the next fuel particle.

Regards
Crispin


From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Andrew Heggie
Sent: 14-Dec-17 22:29
To: Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] Understanding TLUDs, MPF and more. (was Re: Bangladesh TLUD )



On 13 December 2017 at 05:43, Frank Shields <franke at cruzio.com<mailto:franke at cruzio.com>> wrote:

This is an interesting topic and one i have wondered about. When packing hard a pipe with biomass then flushing with N2 then placing in an oven to heat from the outside to a temperature to 550c a lot of gases come out the small hole at the end.  That will ignite if the door is opened and O2 contact. I have wondered if any heat is being produced in the pipe itself? or all from external heat? If there is it can't be much because the temperature advances at a continuous rate. Should you see the temperature jump well above 550c its because air leaked in to the furnace and there is a flame.

Frank it is interesting  what you seem to be showing when opening the door is that the pyrolysis offgas coming out of the hole is above its auotignition point.  What would be relevant to the current discussion is :
1 the temperature variation inside the tube

2 the varying analysis of the composition of offgas as the tube heats up.

Andrew
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