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<div class="moz-cite-prefix">Julien,<br>
<br>
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.<br>
<br>
You asked:<br>
<blockquote type="cite"><font face="Tahoma">2) Is there any
difference [regarding biochar] between forced and natural
draft TLUDs? <br>
</font></blockquote>
<font face="Tahoma">Clearly yes. See the TLUD rest results
section in "All biochars are not created equal...." (2009)
available several places, including at </font><a class="moz-txt-link-freetext" href="http://www.drtlud.com/resources/">http://www.drtlud.com/resources/</a><br>
<br>
This document also discusses oxic and anoxic aspects.<br>
<br>
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).<br>
<br>
Paul<br>
<pre class="moz-signature" cols="72">Doc / Dr TLUD / Prof. Paul S. Anderson, PhD
Email: <a class="moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a>
Skype: paultlud Phone: +1-309-452-7072
Website: <a class="moz-txt-link-abbreviated" href="http://www.drtlud.com">www.drtlud.com</a></pre>
On 4/1/2014 9:04 PM, Julien Winter wrote:<br>
</div>
<blockquote
cite="mid:CALv4xTwJvEuTvntVHtxY5G6dEgN_uNAtuph90MYSJZdtnMQ9oA@mail.gmail.com"
type="cite">
<div dir="ltr">
<div>Hello Rajan and all;</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>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:
<p><font face="Tahoma"><font face="Tahoma">Peterson, S. 2013.
Comparison of gasification and pyrolysis methods for
preparing biochar from corn stover and wheat straw. </font></font></p>
<p><font face="Tahoma"><a moz-do-not-send="true"
href="http://biochar.illinois.edu/Peterson.pdf">http://biochar.illinois.edu/Peterson.pdf</a></font></p>
<p><font face="Tahoma">In this Powerpoint presentation, he
shows that TLUD biochar had a lower surface area than
biochar made by pyrolysis.</font></p>
<p><font face="Tahoma">I think there are some questions to
answer:</font></p>
<p><font face="Tahoma">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?</font></p>
<p><font face="Tahoma">2) Is there any difference between
forced and natural draft TLUDs?</font></p>
<p><font face="Tahoma">3) How recalcitrant to
decomposition is tar in soil, and in particular,
tar embedded on biochar? Is the occlusion of pore space
long-term?</font></p>
<p><font face="Tahoma">And a final comment. Users of TLUDs
will have to learn how to drive them properly if they want
to make good quality biochar.</font></p>
<p><font face="Tahoma">Thanks, Rajan, for your observations.</font></p>
<p><font face="Tahoma">Cheers,</font></p>
<p><font face="Tahoma">Julien.</font></p>
<br clear="all">
<br>
-- <br>
</div>
<div dir="ltr">Julien Winter<br>
Cobourg, ON, CANADA<br>
</div>
</div>
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