[Stoves] TLUD theory -- Fuel Bed Temperatures

[Alex English]

Julien,
Josh Kearns has posted graphs of bed temperatures.

I data logged a T-LUD on wood pellets
http://www.bioenergylists.org/stovesdoc/English/bigtop2.htm

Switching units I have choked primary air as low as possible while 
maintaining a flame. That corresponded to a peak fuel bed temperature of 
480 C.
My impression, though unmeasured, that the gas composition was different 
than at high temperatures. I hav also pushed the TLUD with a high 
pressure blower and at no time did it fail to produce combustible gasses.

Alex


On 16/06/2013 10:57 PM, Julien Winter wrote:
> 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
>
>
>
>
>
> _______________________________________________
> Stoves mailing list
>
> to Send a Message to the list, use the email address
> stoves at lists.bioenergylists.org
>
> to UNSUBSCRIBE or Change your List Settings use the web page
> http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
>
> for more Biomass Cooking Stoves,  News and Information see our web site:
> http://stoves.bioenergylists.org/
>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20130617/7aad70db/attachment.html>