[Stoves] TLUD theory -- Fuel Bed Temperatures

[Julien Winter]

Dear stovers;

What do we know about the temperature in the fuel bed of top-lit
updraft gasifier stoves (TLUDs)?

Almost all features of TLUD function are affected by the temperature
of the fuel bed.  This includes the combustion quality of the effluent
gases, the stability and momentum of the reaction, water boiling rate,
the quality of biochar, the yield of biochar, the nature of effluent
particles, production of crystobalites, production of polynuclear
aromatic hydrocarbons, etc.

In the last 30 years, temperature data has been published for
laboratory bench-top reactors that were, ostensibly, forced-air TLUDs.
 Most of this work was done to understand the function of moving grate
gasifiers for urban waste and biomass fuels (and even earlier research
on coal).  Along with other measurements, temperature observations
were used to calibrate computer simulations.

An example of bench-top TLUD data is attached as a pdf.

These bench-top TLUDs do not cover the range of conditions experienced
in the real world of feral TLUD cookstoves.

What observations are there on fuel bed temperatures in TLUD cookstoves?

What range of temperatures are possible for a functional stove?  If
the reaction is too cool, we just get incombustible shouldering smoke.
 Will the stove function poorly if the temperature is too high and
most of the gases oxidized to CO2 within the bed?  Is there a sweet
spot temperature range, and does it vary between fuels (e.g., grass,
chips, pellets, briquettes)?


Just as an aside, someone should make virtual TLUD stove for testing
theories and teaching.  That shouldn't be too hard for pellets.

Cheers,
Julien-the-eyebrowless



-- 
Julien Winter
Cobourg, ON, CANADA
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