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Crispin,<br>
<br>
Your key sentence is this:
<blockquote type="cite"> Whether one can do it [with only the oxygen
atoms in the biomass] in tin cans on a small scale is a different
matter.
</blockquote>
You conveniently glide past the fact that what we are really
interested in on this Stoves Listserv IS about stoves that are of
small scale.<br>
<br>
What you provide below is quite idealized, in perfect condition,
shown in theory and a chemical formula. Maybe that way it might be
confirmed by a chemist as being true, but it certainly is of minimal
relevance to solving the cookstove problems of impoverished people.
<br>
<br>
The term "splitting hairs" comes to mind. I looked at what you
wrote, but I certainly did not seriously study it. You comments
might be rignt, but your comments are of minimal or no relevance. <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>
<div class="moz-cite-prefix">On 12/12/2017 8:27 PM, Crispin
Pemberton-Pigott wrote:<br>
</div>
<blockquote type="cite"
cite="mid:MWHPR22MB078485086DCB9B53D63242C0B1350@MWHPR22MB0784.namprd22.prod.outlook.com">
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<div class="WordSection1">
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Dear
Andrew and All<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">Now
that everyone is or is not a chemist, it is time to end the
fun.<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">This
is the major point made by you and Paul.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div>
<p class="MsoNormal"><b><span lang="EN-US">></span></b>My
point remaining that to release heat from wood you need to
add oxygen and the fact the wood already has oxygen
containing molecules within it is irrelevant.<br>
<br>
<o:p></o:p></p>
<p class="MsoNormal">I am suggesting that this is incorrect.
Whether one can do it in tin cans on a small scale is a
different matter.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">There are two possible processes that can
take place without oxygen (heating fuel without the addition
of any air at all). They are<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Auto-catalysis<o:p></o:p></p>
<p class="MsoNormal">Auto-pyrolysis<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The first is what I described using a
chemically balanced equation to demonstrate that there is
enough oxygen in biomass to combust 93.6% of the hydrogen.
This is true, but auto-catalysis (the reformation of all the
bonds to provide a re-ordering in a new form to provide H2O
and CO2 as the only outputs) does not take place in biomass.
It is true that
<i>in a fire</i> this could happen, and does, but it is not
true that it can happen without a fire, even though all the
elements are present to do so.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Correction:<o:p></o:p></p>
<p class="MsoNormal">The calculated energy available was using
Tom Reed’s formula is for the energy released upon the
complete combustion of the fuel. I pointed to the 93.6% of
hydrogen combustion which is not the same as 100%
combustion. So the actual energy available for the
re-ordering of the chemistry of biomass without adding air
is 0.5 MJ less than for the full oxidation of the hydrogen.
The heat available using only the internal O is 1.7 MJ/kg
for dry biomass. That is theoretical and based on the
chemical mass balance that would result from auto-catalysis
of the elements. As I said, auto-catalysis does not happen
below 1000 degrees. It is very likely to happen above 2700 C
which would require a reactor beyond our common materials.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">On the matter of auto-pyrolysis of
biomass, this <i>does</i> happen in the complete absence of
air, and this is the key point of the conversation.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Here is a plot of the energy released by
the heating of biomass in an inert environment:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><img style="width:4.725in;height:2.325in"
id="Picture_x0020_1"
src="cid:part1.FB7314A9.28277341@ilstu.edu" class=""
height="223" width="454"><o:p></o:p></p>
<p class="MsoNormal">Please note the spike in heat released at
360-400 C. That is the cellulose (etc) breaking down. There
is a net release of energy. The charts come from
<a
href="http://onlinelibrary.wiley.com/doi/10.1002/pol.1968.150061202/full"
moz-do-not-send="true">here</a>. (H/T Philip Lloyd)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">“<span lang="EN-ZA">An application of TGA
technique to elucidate the chain reaction mechanism of
cellulose pyrolysis is discussed.”<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The reference to a chain reaction is the
way they describe the self-sustaining, auto-pyrolysis of
cellulose. There is an investment of energy at 320 C and
strong release of energy at 360. The TGA charts above show
what happens with other fuel components. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Once it starts, it can continue until
there is no raw biomass left to react, provided it is not
cooled at a rate greater than the net gain in energy. In an
ideal container there would be thermal runaway: the rate of
heat release would increase. This reaction (shown above)
takes place in the absence of air.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">This second phenomenon is not dependent
on the chemical balance (which while theoretically possible,
does not happen in biomass at a realisable temperature).
Auto-pyrolysis actually happens. Additional studies
investigating the energy needed/released are <a
href="http://onlinelibrary.wiley.com/doi/10.1002/app.1970.070140518/full"
moz-do-not-send="true">
here</a> and <a
href="http://onlinelibrary.wiley.com/doi/10.1002/app.1989.070371203/full"
moz-do-not-send="true">
here</a>.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If readers can accept the results of
these experiments (showing the auto-pyrolysis taking place
and validation of the theoretical exothermic reactions
proven) there are implications for the stove makers. One is
that as biomass can pyrolyse without any air at all (as
demonstrated) we can drop the claim that it doesn’t. <o:p>
</o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">>…if I am wrong I admit it, I am also
not a chemist nor ever claimed to be.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am wrong several times a day. I don’t
see why you shouldn’t be affected by those same experiences.
We have on this list a chemist in the shape and likeness of
Prof Philip Lloyd, I believe the past president of the South
African Institute of Chemical Engineers (I hope I have the
name correct).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards<o:p></o:p></p>
<p class="MsoNormal">Crispin<o:p></o:p></p>
</div>
</div>
<br>
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</pre>
</blockquote>
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