<div dir="ltr"><div><div><div><div><div><div><div><div><div>Kevin,<br><br></div>You write: <font face="Arial"><i>Rice Hulls are very interesting. While they have a high
percentage of highly siliceous ash, complete combustion could potentially make
the ash available in a hazardous manner. In Paul O's case, where he is
interested in char making, I would guess that most of the siliceous components
would remain embedded within the char particles, in a safe and non-hazardous
manner. However, some ash particles would be liberated in that some of the char
would be burned in the pyrolysis process.</i><br><br></font></div><font face="Arial">If, in a TLUD, air does not flow up the reactor in a uniform manner, channeling occurs, and zones that are incredibly hot are created. If the biomass contains amorphous silica, some of this silica will surely be converted into cristobalite at such high temperatures. When this mixture of biochar and ash containing cristobalite is removed from the reactor and handled, it would be so easy for the operator to breathe this deadly mixture.<br>
<br></font></div><font face="Arial">The possibility of channeling is minimized if the biomass is thoroughly uniform. Also in the design of the stove, one has to be careful that the fan is not too powerful. Turning up a powerful fan a bit too high will cause channeling.<br>
<br></font></div><font face="Arial">Also rice hulls from most mills that I have seen in Vietnam are not properly dedusted. Consequently there is always some particulate matter in the syngas. This particulate matter might also contain cristobalite.<br>
<br></font></div><font face="Arial">One simple way to solve these two problems is to use a pelleted fuel. Here the flow of air will be perfectly uniform. The pellet is relatively heavy and is not easily displaced within the reactor by a powerful fan. Also the pellet does not have much dust associated with it.<br>
<br></font></div><font face="Arial">So as you see, I have been working for several years on a unit to gasify loose rice hulls. But in the last few weeks I have begun to have serious doubts about the safety of such an apparatus. I feel strongly that the rice hull should be pelleted if it is to be used safely within a stove.<br>
<br></font></div><font face="Arial">Also please do not think about directly combusting any form of biomass that contains appreciable amounts of amorphous silica. For example, burning rice hull pellets is not a very good idea. And yet sadly, this is what is happening to most rice hull pellets in Vietnam. Imagine the poor workers who handle this ash.<br>
<br></font></div><font face="Arial">Thanks.<br></font></div><font face="Arial">Paul Olivier<br></font></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sat, Jun 15, 2013 at 1:01 AM, Kevin <span dir="ltr"><<a href="mailto:kchisholm@ca.inter.net" target="_blank">kchisholm@ca.inter.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><u></u>
<div link="blue" bgcolor="white" vlink="purple" lang="EN-CA">
<div><font face="Arial">Dear Crispin</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">Thanks very much for your helpful comments. </font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">Clearly, a chimney that vents products of combustion
outside the Living Space is advantageous, compared to a stove system that vents
into the Living Space. </font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">I was aware of the great importance of the size of the
Particulate Matter. Basically, "big dirt particles" are not nearly as bad as are
fine particles that can lodge deep in the lungs. Clearly also, "more bad-sized
particles", with "bad type composition", are worse than fewer "safer sized
particles", of "relatively neutral composition.</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">The only way to "digitize the generalities" is with a
scientifically sound test program that identifies and then measures the relevant
parameters. Once numbers have been attached to the relevant parameters, then it
is relatively easy to determine whether or not a given stove system is "safe" or
"hazardous."</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">Rice Hulls are very interesting. While they have a high
percentage of highly siliceous ash, complete combustion could potentially make
the ash available in a hazardous manner. In Paul O's case, where he is
interested in char making, I would guess that most of the siliceous components
would remain embedded within the char particles, in a safe and non-hazardous
manner. However, some ash particles would be liberated in that some of the char
would be burned in the pyrolysis process. </font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">Best wishes,</font></div>
<div><font face="Arial"></font> </div>
<div><font face="Arial">Kevin</font></div>
<div><font face="Arial"></font> </div>
<div>----- Original Message ----- </div>
<blockquote style="BORDER-LEFT:#000000 2px solid;PADDING-LEFT:5px;PADDING-RIGHT:0px;MARGIN-LEFT:5px;MARGIN-RIGHT:0px">
<div style="FONT:10pt arial;BACKGROUND:#e4e4e4"><b>From:</b>
<a title="crispinpigott@gmail.com" href="mailto:crispinpigott@gmail.com" target="_blank">Crispin
Pemberton-Pigott</a> </div>
<div style="FONT:10pt arial"><b>To:</b> <a title="stoves@lists.bioenergylists.org" href="mailto:stoves@lists.bioenergylists.org" target="_blank">'Discussion of biomass cooking
stoves'</a> </div>
<div style="FONT:10pt arial"><b>Sent:</b> Friday, June 14, 2013 10:51
AM</div><div class="im">
<div style="FONT:10pt arial"><b>Subject:</b> Re: [Stoves] Insulation and
stove life</div>
<div><br></div>
</div><div><div class="h5"><div>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt">Dear
Kevin<u></u><u></u></span></p>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt">I
would like to add that using a fan will in all likelihood create much more
flyash than without one. The advantage of a chimney is that the tends to suck
the ash up the chimney, whereas a fan tends to blow it up from below into
whatever outlet it can find. The difference in the room will be large,
obviously.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt">Secondly
the size of the PM matters a lot. If the pyrolysis process releases very fine
siliceous matter with a gentle push from a fan, that material can easily rise
through the fuel bed.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt">So
we should be investigating size, total mass, chemical composition and whether
the stove draws it from the stove and room or pushes it up from
below.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt">Maybe
it is of no consequence at all, maybe it is a hazard.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt">Regards<br>Crispin<u></u><u></u></span></p>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="FONT-FAMILY:'Calibri','sans-serif';COLOR:#1f497d;FONT-SIZE:11pt"><u></u> <u></u></span></p>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<p class="MsoNormal"><span style="FONT-FAMILY:'Arial','sans-serif'">Dear
Rebecca</span><u></u><u></u></p></div>
<div>
<p class="MsoNormal"> <u></u><u></u></p></div>
<div>
<p class="MsoNormal"><span style="FONT-FAMILY:'Arial','sans-serif'">Firstly, I
am concerned about the "Cristobalite Link" below, in that it seems to overlap
"silica", "cristobalite", and other forms of quartz. See: <a href="http://www.quartzpage.de/gen_mod.html" target="_blank">http://www.quartzpage.de/gen_mod.html</a> showing
how various forms of quartz exist at various
temperatures.</span><u></u><u></u></p></div>
<div>
<p class="MsoNormal"><span style="FONT-FAMILY:'Arial','sans-serif'">Note that
"cristobalite" is one specific crystalline phase of
quartz.</span><u></u><u></u></p></div>
<div>
<p class="MsoNormal"> <u></u><u></u></p></div>
<div>
<p class="MsoNormal"><span style="FONT-FAMILY:'Arial','sans-serif'">Secondly,
what is important is the "respirable" dust that is actually respired.
</span><u></u><u></u></p></div>
<div>
<p class="MsoNormal"> <u></u><u></u></p></div>
<div>
<p class="MsoNormal"><span style="FONT-FAMILY:'Arial','sans-serif'">It is well
known that respiring "silica dust" can cause "Silicosis". It is well known
that "Small Particulate Matter emissions" from virtually any poor stove can
cause serious health problems. Hence, the effort to design "stove systems"
that minimize "Small Particulate Matter Emissions" into the living space,
where they can potentially be respired.</span><u></u><u></u></p></div>
<div>
<p class="MsoNormal"> <u></u><u></u></p></div>
<div>
<p class="MsoNormal"><span style="FONT-FAMILY:'Arial','sans-serif'">Rice Hull
Ash, even at 90% silica in the ash pit, is not a problem, in that it is in the
ash pit, where it is not respired. On the other hand, an "apparently superior
fuel" that only had say 25% silica content in the ash pit would be vastly more
hazardous, if it vented 10 or 100 times as much ash into the living space, in
respirable form.</span><u></u><u></u></p></div>
<div>
<p class="MsoNormal"> <u></u><u></u></p></div>
<div>
<p class="MsoNormal"><span style="FONT-FAMILY:'Arial','sans-serif'">This is
where competent and meaningful stove design and testing comes into play.
</span><u></u><u></u></p></div>
<div>
<p class="MsoNormal"> <u></u><u></u></p></div>
<div>
<p class="MsoNormal"><span style="FONT-FAMILY:'Arial','sans-serif'">As has been
said many times, "It is not so much the fuel, but the stove system design,
that is good or bad."</span><u></u><u></u></p></div>
<div>
<p class="MsoNormal"> <u></u><u></u></p></div>
<div>
<p class="MsoNormal"><span style="FONT-FAMILY:'Arial','sans-serif'">Best
wishes,</span><u></u><u></u></p></div>
<div>
<p class="MsoNormal"> <u></u><u></u></p></div>
<div>
<p class="MsoNormal"><span style="FONT-FAMILY:'Arial','sans-serif'">Kevin</span><u></u><u></u></p></div>
<div>
<p class="MsoNormal"> <u></u><u></u></p></div></div>
</div></div><p>
</p><hr><div class="im">
<p></p>_______________________________________________<br>Stoves mailing
list<br><br>to Send a Message to the list, use the email
address<br><a href="mailto:stoves@lists.bioenergylists.org" target="_blank">stoves@lists.bioenergylists.org</a><br><br>to UNSUBSCRIBE or Change
your List Settings use the web
page<br><a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a><br><br>for
more Biomass Cooking Stoves, News and Information see our web
site:<br><a href="http://stoves.bioenergylists.org/" target="_blank">http://stoves.bioenergylists.org/</a><br><br></div><p></p></blockquote></div>
<br>_______________________________________________<br>
Stoves mailing list<br>
<br>
to Send a Message to the list, use the email address<br>
<a href="mailto:stoves@lists.bioenergylists.org">stoves@lists.bioenergylists.org</a><br>
<br>
to UNSUBSCRIBE or Change your List Settings use the web page<br>
<a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a><br>
<br>
for more Biomass Cooking Stoves, News and Information see our web site:<br>
<a href="http://stoves.bioenergylists.org/" target="_blank">http://stoves.bioenergylists.org/</a><br>
<br>
<br></blockquote></div><br><br clear="all"><br>-- <br>Paul A. Olivier PhD<br>26/5 Phu Dong Thien Vuong<br>Dalat<br>Vietnam<br>
<br>Louisiana telephone: 1-337-447-4124 (rings Vietnam)<br>Mobile: 090-694-1573 (in Vietnam)<br>Skype address: Xpolivier<br><a href="http://www.esrla.com/" target="_blank">http://www.esrla.com/</a>
</div>