[Stoves] TLUD theory -- Fuel Bed Temperatures

[Paul Anderson]

My reply is below:

Paul S. Anderson, PhD  aka "Dr TLUD"
Email:  psanders at ilstu.edu   Skype: paultlud  Phone: +1-309-452-7072
Website:  www.drtlud.com

On 6/16/2013 9:57 PM, Julien Winter wrote:
> Dear stovers;
>
> What do we know about the temperature in the fuel bed of top-lit
> updraft gasifier stoves (TLUDs)?
In the document "All biochars are not created equal...." there is a 
discussion with data about fuel bed temperatures in TLUDs, with 
implications about biochars.
> http://www.drtlud.com/resources/publications-and-multimedia/psa-catalogue/ 
>
and at several other sites.

Quite similar in results to the attachment (in Julien's message) that 
used forced draft and reported higher temperatures, as expected.
> Kolb, T; Bleckwehl, S; Gehrmann, HJ; Seifert, H. 2008. 
> Characterisation of combustion
> behaviour of refuse derived fuel. Journal of the Energy Institute 81: 
> 1-6 DOI:
> 10.2179/174602208X269526

Paul


>
> 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
>
>
>
>
>
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