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<div class="moz-cite-prefix">Dear Jaakko,<br>
<br>
Thank you for your excellent message. It is also helpful about
understanding charcoal-burning stoves, which tend to have a rather
shallow thickness of char.<br>
<br>
Can you please elaborate more about the
<blockquote type="cite"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"
lang="EN-GB">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. </span></blockquote>
<br>
Paul<br>
<pre class="moz-signature" cols="72">Paul S. Anderson, PhD aka "Dr TLUD"
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>
On 9/3/2013 8:56 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"
lang="EN-GB">Dear all,<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">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
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">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
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">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
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">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
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>
<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""
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
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>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>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""
lang="EN-US">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
style="font-family:"Calibri","sans-serif""
lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""
lang="EN-US">Nice work Marc!
<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""
lang="EN-US">Erin
<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""
lang="EN-US"><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
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
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>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>
</div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<div>
<div>
<p class="MsoNormal"><span lang="EN-US">Hi everyone,<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<div>
<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>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<div>
<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>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<div>
<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>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<div>
<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>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">More soon...<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">This will be part of
a completely Open Source project<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"><img
id="_x0000_i1025"
src="cid:part2.07000200.03050008@ilstu.edu"
alt="Inline image 1" width="267" height="237"
border="0"><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
</div>
<div>
<div>
<p class="MsoNormal"><span lang="EN-US">marc<o:p></o:p></span></p>
<div>
<p class="MsoNormal"><span lang="EN-US"><a
moz-do-not-send="true"
href="http://notwandering.com" target="_blank">notwandering.com</a><o:p></o:p></span></p>
</div>
</div>
</div>
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