Frank - Whether the upper char is fouled by organics coming off of lower pyrolysis zone in a TLUD is a function of operating temperature, which is a function of draft. TLUDs with sufficient draft make some of the best char out there.
http://www.wcponline.com/pdf/October2012Kearns.pdf The trick is to keep the draft high enough, and thus the char bed hot enough, to not condense tars during the burn. We looked at herbicide uptake using pine pellet char from a 1-gal natural draft "Toucan". Char from the bottom layer had about 35% greater sorption capacity for herbicide than char taken from the top layer. We have not measured, but I would speculate this difference to decrease in a high-draft scenario. Josh On Mon, May 6, 2013 at 12:52 PM, Frank Shields <[email protected]> wrote: > Dear Stovers, > > It seems that a TLUD would make poor quality biochar. There are only two > hot > spots. One is the flame front and the second the flame heating the pot. As > the flame front migrates down through new biomass volatiles come off and > hit > cooler conditions above in the left over char where I would think > condensation of organics would occur. This is good as a cleaner gas goes up > to the secondary air to combust and heat the pot. But the char is left with > tars. This could be better for used as charcoal for other cooking but would > make very poor biochar for the garden - if this is what happens. > > Regards > > Frank > > > Thanks > > Frank Shields > > BioChar Division > Control Laboratories, Inc. > 42 Hangar Way > Watsonville, CE 95076 > > (831) 724-5422 tel > (81) 724-3188 fax > [email protected] > www.controllabs.com > > > > > > _______________________________________________ > 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
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