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<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Dear all,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I have seen blue flames in my heat storing stove under natural draft using wood logs in char combustion stage, when the logs have been broken into
pieces. It is CO burning as has been discussed here by others. Later the blue flame disappears due to lower bed temperature so that CO cannot burn but goes to chimney.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I have also calculated this phenomena. One can see blue flames (CO is burning) if the thickness of bed of char particles and air rate are suitable.
If the bed is too thick, blue flames are inside the bed, increasing gas temperature and gasification takes place above producing CO from the bed. (This CO could be burned if somehow oxygen could be mixed and temperature of the gas is high enough). If the
bed is too thin, excess air (due to lower flow resistance) cools the gas so that CO is not burning or it burning rate is very low. So it needs suitable bed thickness and air rate which are difficult to maintain with natural draft.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">As Richard Stanley has experienced, blue flame is very sensitive to air rate. I noticed this when calculating the burning with a model. The calculation
was based on iteration and on an initial guess. I was astonished that depending on this initial guess I got, not a chaotic solution, but two different stable (quasi)steady state solutions for the temperature and species distributions in the char bed, a high
temperature solution and a low temperature solution. Conclusion is that both solutions could be right (CO is either burning or it is not). It depends on the burning history of the stove which solution is the right one. It the fire is disturbed and cooled
down a little, CO does not burn but if it remains hot, CO can burn.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I throw small twigs in the end stage to get some CO escaping to chimney to burn in the volatiles flames, increase the draft and speed up the burning
of residual char at the end of the heating.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Jaakko
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Stoves [mailto:stoves-bounces@lists.bioenergylists.org]
<b>On Behalf Of </b>Erin Rasmussen<br>
<b>Sent:</b> 24. elokuuta 2013 0:15<br>
<b>To:</b> 'Discussion of biomass cooking stoves'<br>
<b>Subject:</b> Re: [Stoves] Blue Flame -- Natural Draft -- Rice Husk<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Calibri","sans-serif"">Hey that's exciting. I've seen blue flame with wood pellets on occasion, but only on the edges of my stick built fires.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Calibri","sans-serif""><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Calibri","sans-serif"">Nice work Marc!
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Calibri","sans-serif"">Erin
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-family:"Calibri","sans-serif""><o:p> </o:p></span></p>
<div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Stoves [<a href="mailto:stoves-bounces@lists.bioenergylists.org">mailto:stoves-bounces@lists.bioenergylists.org</a>]
<b>On Behalf Of </b>Marc-Antoine Pare<br>
<b>Sent:</b> Thursday, August 22, 2013 8:34 PM<br>
<b>To:</b> Discussion of biomass cooking stoves<br>
<b>Subject:</b> [Stoves] Blue Flame -- Natural Draft -- Rice Husk<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Hi everyone,<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">I've managed to repeat blue flames consistently in a rice husk stove using only natural draft.<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">Anyone seen this before? I am only aware of forced air stoves that achieve blue flames.<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">The photo below is just a teaser. The lighting is terrible and you can't make out the column of blue flame because I'm shooting straight down.<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">The smell is also quite motivating. Usually you get acquainted with the "smell of defeat" with rice husk, since poor combustion smells quite strong. So far, achieving odor on par with forced air units.<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">More soon...<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">This will be part of a completely Open Source project<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><img border="0" width="267" height="237" id="_x0000_i1025" src="cid:image001.png@01CEA8C3.09B2E090" alt="Inline image 1"><o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US">marc<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><a href="http://notwandering.com" target="_blank">notwandering.com</a><o:p></o:p></span></p>
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