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<p><font size="+1">This is an interesting topic and one i have
wondered about. When packing hard a pipe with biomass then
flushing with N2 then placing in an oven to heat from the
outside to a temperature to 550c a lot of gases come out the
small hole at the end. That will ignite if the door is opened
and O2 contact. I have wondered if any heat is being produced in
the pipe itself? or all from external heat? If there is it can't
be much because the temperature advances at a continuous rate.
Should you see the temperature jump well above 550c its because
air leaked in to the furnace and there is a flame. <br>
</font></p>
<p><font size="+1">Frank<br>
</font></p>
<p><font size="+1"> </font><br>
</p>
<br>
<div class="moz-cite-prefix">On 12/12/17 9:07 PM, Paul Anderson
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:574f61e1-cdf9-ea49-70b4-35bb72fac45a@ilstu.edu">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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" moz-do-not-send="true">psanders@ilstu.edu</a>
Skype: paultlud Phone: +1-309-452-7072
Website: <a class="moz-txt-link-abbreviated" href="http://www.drtlud.com" moz-do-not-send="true">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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<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:part3.7197C453.29814005@cruzio.com" class=""
width="454" height="223"><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>
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<pre class="moz-signature" cols="72">--
Frank Shields
444 Main Street Apt. 4205
Watsonville, CA 95076
(831) 246-0417 cell
<a class="moz-txt-link-abbreviated" href="mailto:franke@cruzio.com">franke@cruzio.com</a></pre>
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