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<div class="moz-cite-prefix">AT ETHOS a few years back (2010 I
think), Bryan Wilson gave an excellent presentation on an improved
combustion charcoal stove. The ETHOS website doesn't seem to have
a link for it. <br>
I believe this is the the one,<br>
<a
href="http://www.envirofit.org/products/?sub=cookstoves&pid=12">http://www.envirofit.org/products/?sub=cookstoves&pid=12</a><br>
<br>
Alex<br>
<br>
<br>
<br>
On 18/09/2013 5:37 AM, Saastamoinen Jaakko wrote:<br>
</div>
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<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Dear
Frank and Crispin,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">the main DIRECT product in the reaction of
carbon with oxygen is CO but also some CO2 is directly
formed. CO that is formed can be oxidized to CO2
(CO+½O2=CO2) at high enough temperatures in the vicinity of
carbon particle or in later stage in the gas flow. So there
are different zones along the gas flow in carbon particle
layer when air (or gas) is flowing upwards through it:
<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoListParagraph"
style="margin-left:54.0pt;text-indent:-36.0pt;mso-list:l0
level1 lfo1">
<!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><span style="mso-list:Ignore">I)<span
style="font:7.0pt "Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">Zone where exothermic reaction C+½O2=CO takes
place (but some CO2 is also formed). Here the gas
temperature is rather low because it is close to the inlet
and the gas has not heated up enough. So CO is not burning
well. <o:p></o:p></span></p>
<p class="MsoListParagraph"
style="margin-left:54.0pt;text-indent:-36.0pt;mso-list:l0
level1 lfo1">
<!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><span style="mso-list:Ignore">II)<span
style="font:7.0pt "Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">Zone where the gas temperature becomes high
enough so that also the exothermic reaction CO+½O2 =CO2
(enhanced by H2O) takes place in the gas. This leads to even
higher local temperature along the gas flow so that
exothermic reactions (C+½O2=CO and CO+½O2=CO2) take place at
even higher rate. Here also the endothermic reaction
CO2+C=2CO takes place because the char temperature is high
enough. This rrwaction adjust the temperature level
preventing it to increase very high. Then at the location,
where all oxygen is consumed, the gas temperature and CO2
concentration reach the maximum values. <o:p></o:p></span></p>
<p class="MsoListParagraph"
style="margin-left:54.0pt;text-indent:-36.0pt;mso-list:l0
level1 lfo1">
<!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><span style="mso-list:Ignore">III)<span
style="font:7.0pt "Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">After that the carbon reacts with CO2 producing
carbon monoxide in endothermic gasification reaction
CO2+C=2CO. The gas is cooled due to this endothermic
reaction. If the layer is very thick, the gas is cooled to a
temperature at which the reaction rate C+CO2=2CO becomes
very low.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">So some conclusions:<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoListParagraph"
style="text-indent:-18.0pt;mso-list:l1 level1 lfo2"><!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><span style="mso-list:Ignore">1.<span
style="font:7.0pt "Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">For a thin layer, there is only zone I
producing CO.
<o:p></o:p></span></p>
<p class="MsoListParagraph"
style="text-indent:-18.0pt;mso-list:l1 level1 lfo2"><!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><span style="mso-list:Ignore">2.<span
style="font:7.0pt "Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">For thicker layer (zone II), the exit gas
contains much CO2 and some CO. The exit gas is hot and CO
may be burned introducing (preheated) secondary air. The
exit gas is hottest if the thickness of the layer is just in
the intermediate transfer regime from zone II to III.
<o:p></o:p></span></p>
<p class="MsoListParagraph"
style="text-indent:-18.0pt;mso-list:l1 level1 lfo2"><!--[if !supportLists]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><span style="mso-list:Ignore">3.<span
style="font:7.0pt "Times New Roman"">
</span></span></span><!--[endif]--><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">For a thick layer, the gas contains much CO and
some CO2. Its temperature is low and it is difficult to burn
CO without highly preheated secondary air.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">The reaction CO+½O2=CO2 can take place also in
the other direction. This reverse reaction (dissociation) of
carbon dioxide is not significant at temperatures <1800
K.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">Regards
<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">Jaakko<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"
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>Frank Shields<br>
<b>Sent:</b> 18. syyskuuta 2013 0:55<br>
<b>To:</b> 'Discussion of biomass cooking stoves'<br>
<b>Subject:</b> Re: [Stoves] Charcoal stove design<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:teal"
lang="EN-US">Dear Crispin,<o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:teal"
lang="EN-US"><o:p> </o:p></span></b></p>
<p class="MsoNormal"><b><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:teal"
lang="EN-US">So the CO2 > CO is endothermic. But still
needs carbon. As I see it the only difference is the
temperature changing as the gases move around the pot.
Wondering if the reading could be affected by temperature?
Perhaps amount of gas entering the instrument or
something? Interesting. Could hydrogen react with one of
the oxygen in CO2 making water leaving CO? <o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:teal"
lang="EN-US"><o:p> </o:p></span></b></p>
<p class="MsoNormal"><b><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:teal"
lang="EN-US">Frank<o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:teal"
lang="EN-US"><o:p> </o:p></span></b></p>
<div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext"
lang="EN-US"> Stoves [<a moz-do-not-send="true"
href="mailto:stoves-bounces@lists.bioenergylists.org">mailto:stoves-bounces@lists.bioenergylists.org</a>]
<b>On Behalf Of </b>Crispin Pemberton-Pigott<br>
<b>Sent:</b> Tuesday, September 17, 2013 2:01 PM<br>
<b>To:</b> 'Discussion of biomass cooking stoves'<br>
<b>Subject:</b> Re: [Stoves] Charcoal stove design<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-CA">My conclusion is the CO splits endothermically.
It does not happen in stoves with high EA.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-CA">Crispin<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-CA"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-CA"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-CA"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:olive"
lang="EN-US">Dear Crispin,<o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:olive"
lang="EN-US"><o:p> </o:p></span></b></p>
<p class="MsoNormal"><b><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:olive"
lang="EN-US"><snip><o:p></o:p></span></b></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-CA"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-CA">I found that directly above the middle of a
good stove (under the pot) there is zero CO – I was amazed.
But nearer the edges there is more.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:olive"
lang="EN-CA"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><i><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:olive"
lang="EN-CA">[Frank >] How is that possible? I
thought going from CO2 > CO could only occur be in a
bed of char. This is very strange.
<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:olive"
lang="EN-CA"><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:olive"
lang="EN-CA">Regards<o:p></o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:olive"
lang="EN-CA"><o:p> </o:p></span></i></b></p>
<p class="MsoNormal"><b><i><span
style="font-size:14.0pt;font-family:"Calibri","sans-serif";color:olive"
lang="EN-CA">Frank<o:p></o:p></span></i></b></p>
</div>
<br>
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