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<DIV><FONT face=Arial>Dear Paul</FONT></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">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=paul.olivier@esrla.com href="mailto:paul.olivier@esrla.com">Paul
Olivier</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=stoves@lists.bioenergylists.org
href="mailto:stoves@lists.bioenergylists.org">Discussion of biomass cooking
stoves</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, June 14, 2013 9:09 PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Stoves] Insulation and
stove life</DIV>
<DIV><BR></DIV>
<DIV dir=ltr>
<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>
<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.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial># Certainly, channelling is a problem. It is caused by
"non-uniform fuel" (both size and density), that has too much "primary air
pressure." Unfortunately, once it starts, it tends to get worse. Additionally,
as the channel diameter increases, even more air tends to flow up through it,
creating a locally intense combustion condition. </FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial> 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.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial># Could to problem be reduced to an acceptable level, by
lightly spraying teh Ash plus biochar with a light spray of water from a
hand-operated sprayer bottle?</FONT><FONT
face=Arial><BR></DIV></DIV></DIV></DIV></DIV></DIV></DIV></DIV>
<DIV dir=ltr>
<DIV></FONT><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.</FONT></DIV><FONT face=Arial></FONT></DIV><FONT
face=Arial></FONT></BLOCKQUOTE>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV><FONT face=Arial># Yes, the fan pressure and flow must be controlled or
limited, in a way to prevent channelling, or "spouting" of the fuel
bed.</FONT></DIV>
<DIV><FONT face=Arial><BR> </DIV>
<DIV dir=ltr></FONT><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></FONT></DIV>
<DIV dir=ltr><FONT face=Arial># If the presence of dust is a problem, could
you not configure a very simple "Rice Hull De-duster"? The equivalent to a
"Seed Cleaner" that blew off teh dust and chaff, while allowing the hulls to
be recovered should work well. BTW.... "gasifier gas" is not "syngas". "syngas
is a gas of definite composition, intended for use as a 'feedgas to a
synthesis process." It would more accurately be called "Producer Gas", "Rice
Hull Gas", etc. <BR></DIV>
<DIV dir=ltr></FONT><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.</FONT></DIV><FONT face=Arial></FONT></BLOCKQUOTE>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV><FONT face=Arial><STRONG># Certainly, more dense pellets would permit
higher "under-bed pressure" without channelling. From a "big picture
standpoint", one can certainly reduce the tendency for channelling by
"de-dusting" the fuel, and then simply reducing the "under-bed
pressure."</STRONG></FONT></DIV>
<DIV><FONT face=Arial><BR></FONT><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.</FONT></DIV><FONT face=Arial></FONT></BLOCKQUOTE>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV><FONT face=Arial><STRONG># Simple pelletizing the rice hulls may not
reduce the tendency for dust and particulate emissions, in that with the
greater density, and reduced channelling tendency, one would be tempted to
increase the "under-bed pressure", to increase air flow, and heat output rate.
The 'local air velocity" may actually be high enough to scour off ash and
carry it out of the stove.</STRONG> </FONT></DIV><FONT
face=Arial>
<DIV><BR></FONT><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.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial># I would suggest that in a TLUD producing char, there
is still some "localized complete combustion", where it is possible for some
of the silica ash to be freed up from the char, so that it can be blown away.
Most would, of course, be trapped within the char. The higher the localized
velocity through the bed, then teh greater the likelihood of ash being carried
out of the stove with teh products of combustion.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial># What do you think of my previous suggestion of adding
Ca(OH)2 to the RH fuel, before combustion? Basically, the Rice Hulls could be
sprayed with "white-wash", and then be allowed to "sun dry." The idea is that
the reactive silica would react with the Ca(OH)2, to form a "Calcium Silicate"
of some sort, that would stay with the char, rather than venting into the
Living space.</FONT></DIV><FONT face=Arial></FONT></BLOCKQUOTE>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"><FONT
face=Arial>
<DIV dir=ltr>Best wishes,</DIV>
<DIV dir=ltr> </DIV>
<DIV dir=ltr>Kevin<BR><BR></DIV>
<DIV dir=ltr></FONT><FONT face=Arial>Thanks.<BR></DIV>
<DIV dir=ltr></FONT><FONT face=Arial>Paul Olivier<BR></DIV></FONT>
<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
style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote><U></U>
<DIV lang=EN-CA vlink="purple" bgcolor="white" link="blue">
<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>
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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>
<P>
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