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Gordon and Crispin, (First of 3 replies to about a dozen
messages on this topic. Not in any special order. I thank everyone
for their comments.)<br>
<br>
There is O in the carbohydrates. And during pyrolysis /
carbonization, carbon is left behind. Chemical compositions have
changed. But that does not mean that the O is "freed" to combust.
Pyrolytic gases are essentially "smoke" that is with lots of tars
and long-chain hydrocarbons. Note, long-chain hydROcarbons that
will take oxygen atoms with them up into the combustion zone where
the secondary air is present.<br>
<br>
I do not know how much O of biomass hydrocarbons becomes freed, but
certainly not all of it, and maybe not much it. I hope that some
combustion chemist can clarify about this. <br>
<br>
I appreciate Crispin's reply statement in a differnent recent
message (copied below) and I hope for some chemist to be able to
reply.
<blockquote type="cite">
<p class="MsoNormal"><span style="color:windowtext"> </span></p>
<p class="MsoNormal"><span style="color:windowtext">For those who
want to look further into the chemistry of this process, there
is a calculation made in the HTP analysis spreadsheet that
calculates the air demand of the fuel based on the elemental
composition of the fuel and the char remaining at the end.
From an assumed need for all oxygen to come from air, the
actual requirement for a TLUD making a lot of char is only 20%
of the theoretical need for the whole fuel, because 80% is
provided from the biomass itself.</span></p>
<p class="MsoNormal"><span style="color:windowtext"> </span></p>
<p class="MsoNormal"><span style="color:windowtext">EA+1 = λ</span><span
style="color:windowtext"></span></p>
<p class="MsoNormal"><span style="color:windowtext"> </span></p>
<p class="MsoNormal"><span style="color:windowtext">where λ is the
total air demand. This calculation is incorrect. The real
values for a TLUD are</span><span style="color:windowtext"></span></p>
<p class="MsoNormal"><span style="color:windowtext"> </span></p>
<p class="MsoNormal"><span style="color:windowtext">EA+0.2 = λ</span><span
style="color:windowtext"></span></p>
<p class="MsoNormal"><span style="color:windowtext"> </span></p>
<p class="MsoNormal"><span style="color:windowtext">You only need
to provide 1/6<sup>th</sup> of the theoretical oxygen
requirement of the fuel, provided it is biomass and you want
to make char.</span></p>
<p class="MsoNormal"><span style="color:windowtext"> </span></p>
</blockquote>
<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>
<div class="moz-cite-prefix">On 12/10/2017 12:05 PM, Crispin
Pemberton-Pigott wrote:<br>
</div>
<blockquote type="cite"
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<div class="WordSection1">
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Dear
Gordon<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">To
be technical about it, the thermal decomposition of biomass
releases O (not O2) as well as N and H in approximately the
same ratio as they occur in the material.
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">All
that is required is to heat the fuel. If it is heated with
inadequate oxygen available, some of the fuel will remain
unburned. That naturally is the carbon, which is the most
difficult to evaporate. The surface burns.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">As
explained earlier, if the fuel is heated enough, a TLUD
burning wood pellets would continue burning (pyrolysing)
without any added air. As the H burned, it would release 120
MJ/kg and the carbon burned to CO would release about 8
MJ/kg. There is enough to keep the fire going if it is large
enough and insulated.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Regards<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Crispin<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #E1E1E1
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span
lang="EN-US"> Stoves
[<a class="moz-txt-link-freetext" href="mailto:stoves-bounces@lists.bioenergylists.org">mailto:stoves-bounces@lists.bioenergylists.org</a>]
<b>On Behalf Of </b>Gordon West<br>
<b>Sent:</b> 10-Dec-17 22:42<br>
<b>To:</b> Discussion of biomass cooking stoves
<a class="moz-txt-link-rfc2396E" href="mailto:stoves@lists.bioenergylists.org"><stoves@lists.bioenergylists.org></a><br>
<b>Subject:</b> Re: [Stoves] Understanding TLUDs, MPF
and more. (was Re: Bangladesh TLUD )<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Is there a report on monitoring an Adams
retort MPF using thermocouples? I am still not successfully
visualizing the process.<o:p></o:p></p>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">I did a bit of a search of technical
reports on the chemistry of woody biomass pyrolysis and have
not yet found a reference to the release of O2 from heating
the feedstock and its subsequent recombination with other
elements resulting in an MPF. Several analyses of syngas
that I saw show plenty of oxygen but it is bound in various
fuel molecules.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<div>
<div>
<div>
<div>
<p class="MsoNormal"><span style="color:black">Gordon<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
</div>
</div>
</div>
<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
</div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><o:p> </o:p></p>
</div>
<br>
</div>
</div>
</blockquote>
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