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<DIV><FONT face=Arial>Dear Paul</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Thanks very much for your detailed
explanation.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Fundamentally, a "Perfect" TLUD will work perfectly if it
has perfect fuel, perfect, required air volume, and perfect fan pressure (or
stack vacuum) to deliver the perfect air flow.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Given that you have "off-standard" fuel, with greater
average void space diameter, the pressure loss across the fuel bed will be
lower. The fan or stack will thus deliver more air through the bed. Thus, you
will get excess primary air flow, and if your secondary air porting was designed
for a bed with a greater pressure drop, you will get less secondary air
delivery; this will mess up your intended Secondary/Primary air
ratio.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>You can burn virtually any fuel in a TLUd, as long as it
is uniform, and the stove was designed to handle it. Change the fuel
significantly, and you need to change the design, to maintain the desired SA/PA
ratio. If you "change the fuel", but don't change the design, then the only way
to restore the system to "good operation" is to "modify the fuel" to one having
similar a pressure drop across the bed, similar to one for which the system
was designed. This is what you are effectively trying to do.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Assume, for example, that you have 4" long pieces of straw
as fuel. This will likely give you all the problems you note. Adding char can,
in theory, help increase the bed pressure drop. However, I am guessing that it
will be a real stinker to get the char particles distributed through the bed.
There will likely be "too much" in one area, and "too little" in another.
Channelling is thus very likely. What you will probably end up with is a fuel
bed having non-uniform flow properties, because of the large differences between
straw properties and char properties. Try mixing various percentages of char
with the straw, in a mixing bucket, then try to take "mixed fuel" from the
"mixing bucket" and place it in the stove. I am guessing that you should see the
non-uniformity of the fuel bed even before you ignite it.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>My guess is that your best bet would be to chop the straw,
so that it is free-flowing. This alone will make life very much easier for the
operator, and will enable a greater weight of fuel to be added to the stove.
Longer burn times between re-fuelling. Play with the air flow, simply by
obstructing the fan intake with a piece of paper or cardboard. Then see if you
can get your usual good combustion. If not, then consider re-drilling or
partially plugging, the SA air holes to get back to the correct PA/SA ratio
for good combustion.</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Is chopping the straw (or whatever the fuel is) an option
you can consider?</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>
<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=psanders@ilstu.edu href="mailto:psanders@ilstu.edu">Paul Anderson</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=biochar@yahoogroups.com
href="mailto:biochar@yahoogroups.com">biochar@yahoogroups.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=kchisholm@seaside.ns.ca
href="mailto:kchisholm@seaside.ns.ca">Kevin</A> ; <A
title=stoves@lists.bioenergylists.org
href="mailto:stoves@lists.bioenergylists.org">Discussion of biomass cooking
stoves</A> ; <A title=jss@bitmaxim.com href="mailto:jss@bitmaxim.com">James S.
Schoner</A> ; <A title=wastemin1@verizon.net
href="mailto:wastemin1@verizon.net">Hugh McLaughlin</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, May 06, 2013 11:23 AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Stoves] [biochar] Charcoal
as space filler in TLUD reactors</DIV>
<DIV><BR></DIV>
<DIV class=moz-cite-prefix>Kevin,<BR><BR>The objective of the filler is
two-fold: <BR><BR>One reason is precisely to reduce the
maximum flow of primary air. Without resistance, too much primary
air can race through the loose pile of biomass, reach too much of the biomass
at the same time, and have an excessive fire without much control.
Control simply by a "gate" at the entrance of the primary air is usually
insufficient.<BR><BR>Second reason is that burning embers at the top of
loosely packed fuel can sometimes fall to lower areas of the fuel bed and
ignite the raw fuel there. This defeats the process of the
pyrolysis front that starts at the top and should progress slowly and
uniformly downward through the bed of fuel. That migrating
pyrolytic front is THE most important and distinguishing feature of the TLUD
stoves. Ignition at the top and having updraft are not the
single-most defining characteristics of TLUD stoves (even though that is what
the name says). Maybe I should have called it Migrating Pyrolytic
Front Gasification (or MPFG), but TLUD is the accepted name
now. [And Tom Reed always thanks me for getting away from
the Inverted DownDraft (IDD) name that was not well
understood.]<BR><BR>Important note: When the pyrolytic front correctly
reaches the bottom of the batch of fuel, the combustion style changes to be
Bottom-Burning UpDraft (call it BBUD if you must have an acronym, but note
that at the start it was NOT IGNITED or lit at the bottom). And
there is no more migration/movement of a "gas-making" zone.
<BR><BR>Also note: When the batch has been pyrolyzed, the burning at the
bottom is "char-gasification" and can be at forge temperatures that can damage
the metal pieces. There is still restricted flow of primary
air. The hot gases go upward. IF additional raw
biomass fuel is placed onto the top of that charcoal, it will be heated,
dried, torrified, and eventually pyrolyzed, giving additional pyrolytic gases
that can be combusted where the incoming secondary air enters. But
this is NOT operating as a TLUD stove (with MPFG). This type of
bottom-burning gasifier is well illustrated by the Oorja stove (former BP, now
First Energy) in India. It has a cast-iron cup in the bottom to
protect the other metal parts, and that cup glows red-hot after continual
use. [Technical note: Stove testing should measure
separately the emissions during each of the different combustion modes instead
of just reporting averages that include emissions from two or more combustion
modes. I think we can do some of that at this summer's Stove Camps
at CREEC - Uganda and at Aprovecho - Oregon-USA where emissions equipment is
available.]<BR><BR>About terminology: A bucket stove or mud stove
or Rocket stove and many others can be ignited at the bottom of a container
and they do have updraft, BUT they are NOT GASIFIER devices. So
the designation BLUD is not relevant. UD and DD and TLUD are
designations historically for gasifiers, which means that the gases are
created in one place that is NOT the same place as the combustion or other use
of the
gases.<BR><BR>Paul
(James, please get this onto the drtlud.com website in edited
format.)<BR><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
5/6/2013 1:17 AM, Kevin wrote:<BR></DIV>
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<DIV><FONT face=Arial>Dear Paul</FONT></DIV>
<DIV> </DIV>
<BLOCKQUOTE style="BORDER-LEFT: #000000 2px solid">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV style="FONT: 10pt arial; BACKGROUND: #e4e4e4"><B>From:</B> <A
title=psanders@ilstu.edu href="mailto:psanders@ilstu.edu"
moz-do-not-send="true">Paul Anderson</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=stoves@lists.bioenergylists.org
href="mailto:stoves@lists.bioenergylists.org"
moz-do-not-send="true">Discussion of biomass cooking stoves</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=kchisholm@seaside.ns.ca
href="mailto:kchisholm@seaside.ns.ca" moz-do-not-send="true">Kevin</A> ;
<A title=biochar@yahoogroups.com href="mailto:biochar@yahoogroups.com"
moz-do-not-send="true">biochar@yahoogroups.com</A> ; <A
title=jss@bitmaxim.com href="mailto:jss@bitmaxim.com"
moz-do-not-send="true">James S. Schoner</A> ; <A
title=wastemin1@verizon.net href="mailto:wastemin1@verizon.net"
moz-do-not-send="true">Hugh McLaughlin</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, May 05, 2013 6:33
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Stoves] [biochar]
Charcoal as space filler in TLUD reactors</DIV>
<DIV><BR></DIV>
<DIV class=moz-cite-prefix>Kevin,<BR><BR>The "charcoal as filler" is not
about consuming the charcoal. </DIV>
<DIV class=moz-cite-prefix> </DIV>
<DIV class=moz-cite-prefix><FONT face=Arial># Sorry, I missed
that.</FONT></DIV>
<DIV class=moz-cite-prefix> </DIV>
<DIV class=moz-cite-prefix> The charcoal is "almost" non-active in
the pyrloysis of the new biomass. This is a discussion about
limiting air flows with a filler that mostly is inactive in environments
that are at 650 C without oxygen. </DIV>
<DIV class=moz-cite-prefix> </DIV>
<DIV class=moz-cite-prefix><FONT face=Arial># Why do you feel it would be
advantageous to limit air flow with an inert filler? If the char was
significantly larger or smaller than the biomass fuel, it could
significantly increase pressure drop through the bed, and would likely
reduce maximum flow. </FONT></DIV>
<DIV class=moz-cite-prefix> </DIV>
<DIV class=moz-cite-prefix><FONT face=Arial># Thanks.</FONT></DIV>
<DIV class=moz-cite-prefix> [ Note that I avoid
using the word "inert" in this discussion.]</DIV>
<DIV class=moz-cite-prefix> </DIV>
<DIV class=moz-cite-prefix><FONT face=Arial>Best
wishes,</FONT></DIV></BLOCKQUOTE>
<BLOCKQUOTE style="BORDER-LEFT: #000000 2px solid">
<DIV> </DIV>
<DIV><FONT face=Arial>Kevin</FONT></DIV>
<DIV class=moz-cite-prefix><BR><BR>Paul<BR></DIV>
<DIV class=moz-cite-prefix><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" moz-do-not-send="true">psanders@ilstu.edu</A> Skype: paultlud Phone: +1-309-452-7072
Website: <A class=moz-txt-link-abbreviated href="http://www.drtlud.com" moz-do-not-send="true">www.drtlud.com</A></PRE></DIV><BR></BLOCKQUOTE></DIV></DIV></DIV></BLOCKQUOTE><BR></BLOCKQUOTE></BODY></HTML>