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<DIV><FONT size=2 face=Arial>Marc,</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I have also been struggling with this transition
problem. It has become more pronounced since the rains started, so
humidity may be a contributing factor. Also, the ND-TLUD I am using has
turn-down capability and the transition problem seems to share some
similarities with turn-down problems. This makes sense because in both
cases the wood gas production is being reduced and the temperature of
the flame is lower. This made me think that perhaps the problem could be
addressed in the same way that turn-down is addressed, with either hot char or
pilot flame support. This has so far not worked with pilot flame
support. What has helped is giving the stove lots of primary air to
get the char hot before the flame reduces. Entering this phase with the
stove turned to a low setting always results in smoke. This is in keeping
with something that Crispin wrote about, using paper to cover excess primary
holes. When the pyrolysis front reaches the bottom, it burns the paper and
lets extra primary air in to heat the char, which helps get through this phase
without smoke. It might be a pain to add this paper to each burn.
</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Fuel depth may have some input
here. With a large load the char will start burning at the
bottom and will not be near the decreasing wood gas to heat and ignite
it. Directing air down onto the top of the char and heating some of it to
red hot may help. This is one of the methods of supporting turn-down by
using red hot char. Julian Winter once suggested a purched char method for
turn-down which did work. Placing a small amount of char or wood which
will become char in a wire basket inside the reactor just below the secondary
air inlet provides red hot char to support the secondary flame during
turn-down. This would have the deminishing transition wood-gas passing
through red hot char to be heated and ignited. This might work for
the transition and also provide turn-down. </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>The primary air in this phase will be used mainly
for the last bit of pyrolysis and the char will gradually increase burning as
the pyrolysis slows down. This produces a temperature low point before the
char heats up. Excess primary air just before this phase can heat the char
to keep the temperature up. Keeping the temperature up is
important.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Please post anything you might learn.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Kirk</FONT></DIV>
<DIV><FONT size=2 face=Arial>Santa Rosa, CA. USA</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=marquitusus@hotmail.com
href="mailto:marquitusus@hotmail.com">Marquitusus</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=stoves@lists.bioenergylists.org
href="mailto:stoves@lists.bioenergylists.org">stoves@lists.bioenergylists.org</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, December 12, 2014 1:01
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [Stoves] Smokeless
transition</DIV>
<DIV><BR></DIV>
<DIV dir=ltr>Hi Stovers,
<DIV><BR></DIV>
<DIV>There is a point in the TLUD process that I find specially difficult to
understand and control: the transition from wood gasification to char
gasification. Maybe you can help me to do it.</DIV>
<DIV><BR></DIV>
<DIV>At this point, <SPAN
style="FONT-SIZE: 15px"> when </SPAN><SPAN
style="FONT-SIZE: 12pt">the hydrocarbon fuel is near to
finish, </SPAN><SPAN style="FONT-SIZE: 12pt">my experiments with almond
husks as fuel for ND-TLUD shows 2 possible endings:</SPAN></DIV>
<DIV> 1- The flames in the burner
turns to blue color (due to high CO presence in gases) and the char pyrolisis
continues until ashes. No smoke present.</DIV>
<DIV> 2- The flames in the burner
extinguishes and the smoke appears.</DIV>
<DIV><BR></DIV>
<DIV>I made a lot of tests, with variations in ND-TLUD design (riser height,
quantity of primary and secondary air, type of concentrator, etc.) and
still I'm not able to say which factor combination is the answer for a
smokeless transition. Sometimes I have smoke, and sometimes I
don't. </DIV>
<DIV><BR></DIV>
<DIV>I suspect the answer has to do with chemical fuel composition, as w<SPAN
style="FONT-SIZE: 15px">hen I use wood pellets, almost never have
smoke.</SPAN></DIV>
<DIV><SPAN style="FONT-SIZE: 15px"><BR></SPAN></DIV>
<DIV><SPAN style="FONT-SIZE: 12pt">So this is the point where I am today. When
char gasification begins, I have to lower the primary air? Lower the secondary
air? How I can ensure the flame won't extinguish?</SPAN></DIV>
<DIV><SPAN style="FONT-SIZE: 12pt"><BR></SPAN></DIV>
<DIV><SPAN style="FONT-SIZE: 12pt">It would be very useful for me to read your
comments about this.</SPAN></DIV>
<DIV><SPAN style="FONT-SIZE: 12pt"><BR></SPAN></DIV>
<DIV><SPAN style="FONT-SIZE: 12pt">Thanks very much,</SPAN></DIV>
<DIV><SPAN style="FONT-SIZE: 12pt"><BR></SPAN></DIV>
<DIV><SPAN style="FONT-SIZE: 12pt">Marc</SPAN></DIV>
<DIV><BR></DIV>
<DIV><BR></DIV></DIV>
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