Sorry - realized I didn't answer the original question: We measure temperature in the fuel bed.
JK On Mon, Jun 17, 2013 at 12:44 PM, Josh Kearns <[email protected]>wrote: > Using a 1-gal TLUD "Toucan" model in natural and forced air modes, we have > seen, pretty consistently, ND peak temps. 600-650 C, and FD peak temps > 900-950 C. This has been across feedstocks - wood pellets, sugarcane > bagasse pellets, bamboo chips, jatropha presscake pellets, pecan shells, > cherry pits. > > Temperature is controlled by draft, and we were lucky to achieve high > draft conditions in our 55-gal drum TLUD without applying a fan. Feedstock > granularity, density, and bed density had to be within an optimal range > however. High draft 55-gal TLUD chars from dense, uniform feedstocks (e.g. > eucalyptus branches 1-2-" dia cut into 4-6" segments) seem to offer > equivalent sorption performance as 1-gal FD chars made from wood pellets. > > Interestingly, temperatures have been more or less independent of > feedstock, but burn duration is longer with denser feedstocks. If > feedstocks are insufficiently dense, e.g. the bagasse pellets I made with > our crappy benchtop pelletizer, then they tend to burn up and the char > yield is very low if draft is high. > > Also, interestingly, feedstock did not seem to matter much for sorption of > our probe compounds (e.g herbicide), where peak temperatures were > consistent. This agrees with other work that finds peak temperature, and to > a lesser extent heating duration, to be controlling factors in product char > properties, with feedstock identity exerting less of an influence (except > insofar as feedstock identity exerts intrinsic effects on the pyrolysis > regime). > > JK > > > > On Mon, Jun 17, 2013 at 8:56 AM, Alex English <[email protected]>wrote: > >> >> >> 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 >> [email protected] >> >> to UNSUBSCRIBE or Change your List Settings use the web >> pagehttp://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/ >> >> >> >> _______________________________________________ >> Stoves mailing list >> >> to Send a Message to the list, use the email address >> [email protected] >> >> 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/ >> >> >> > > > -- > Josh Kearns > PhD Candidate, Environmental Engineering > University of Colorado-Boulder > Visiting Researcher, North Carolina State University > > Director of Science > Aqueous Solutions > www.aqsolutions.org > > Mobile: 720 989 3959 > Skype: joshkearns > > > > -- Josh Kearns PhD Candidate, Environmental Engineering University of Colorado-Boulder Visiting Researcher, North Carolina State University Director of Science Aqueous Solutions www.aqsolutions.org Mobile: 720 989 3959 Skype: joshkearns
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