[Stoves] Adding value to charcoal from TLUD stoves

Paul Anderson psanders at ilstu.edu
Tue Apr 1 23:17:59 CDT 2014


Julien,

I will raise a few questions with Steve Peterson (by phone) to seek some 
clarification about his report.   One topic is that both the retort 
chars and the "gasification chars" are the result of pyrolysis.   One 
main difference is anoxic vs. oxic (oxygen present) processes.

You asked:
> 2)  Is there any difference [regarding biochar] between forced and 
> natural draft TLUDs?
Clearly yes.   See the TLUD rest results section in "All biochars are 
not created equal...." (2009) available several places, including at 
http://www.drtlud.com/resources/

This document also discusses oxic and anoxic aspects.

Hugh McLaughlin is a leading expert on this and about the question about 
subjecting chars to high heat AFTER PRODUCTION in order to improve their 
characteristics.   Hugh is the principal author of the "All 
biochars...." paper, which IMO should be part of the basic instruction 
about biochar differences as far as chemical properties are concerned 
(not dealing with soils and plants).

Paul

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

On 4/1/2014 9:04 PM, Julien Winter wrote:
> Hello Rajan and all;
>
> The point you raise about allowing for a few minutes of the 
> char-burning phase to heat the charred fuel and drive off any left 
> over volatiles is a good one.
>
> The height of the TLUD combustion chamber is likely to be important, 
> because the top of a tall column of charcoal may not get hot enough to 
> drive off volatiles by char-burning. In addition, the top of a 
> tall column will have experienced a longer time for tars to condense 
> during the flaming-pyrolysis phases than a shorter column.  I have 
> made some grimy wood-pellet biochar in a stove pipe TLUD.
>
> Not driving off the volatiles will result in fine pore space of the 
> biochar being occluded.  Perhaps that is what was going on with the 
> following research:
>
> Peterson, S. 2013. Comparison of gasification and pyrolysis methods 
> for preparing biochar from corn stover and wheat straw.
>
> http://biochar.illinois.edu/Peterson.pdf
>
> In this Powerpoint presentation, he shows that TLUD biochar had a 
> lower surface area than biochar made by pyrolysis.
>
> I think there are some questions to answer:
>
> 1)  Is it commonly the case the a short period of char-burning will 
> raise the temperature of the bed of char sufficiently to drive off all 
> condensed volatiles?
>
> 2)  Is there any difference between forced and natural draft TLUDs?
>
> 3)  How recalcitrant to decomposition is tar in soil, and in 
> particular, tar embedded on biochar?  Is the occlusion of pore space 
> long-term?
>
> And a final comment.  Users of TLUDs will have to learn how to drive 
> them properly if they want to make good quality biochar.
>
> Thanks, Rajan, for your observations.
>
> Cheers,
>
> Julien.
>
>
>
> -- 
> Julien Winter
> Cobourg, ON, CANADA
>
>
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