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<DIV><FONT face=Arial size=2><STRONG>Hi John And
Colleagues,</STRONG></FONT></DIV>
<DIV><STRONG><FONT face=Arial size=2></FONT></STRONG> </DIV>
<DIV><STRONG><FONT face=Arial size=2>As I am back to access my computer today
after a week away, I see a question that needs an answer relating to a DIY
gasifier using the Fluidyne gas making principles.</FONT></STRONG></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I have a gasifier (Fluidyne design) that works
excellently with two inch chunks of wood, but when we switched to burning
briquettes (compressed shavings and sawdust) everything changed so much that we
no longer can sustain gas production, plus have extreme amounts of slipped char
and cyclone particulates.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>In a downdraft gasifier that has a sealed
fuel hopper, the stack gases that form around the fuel is mainly wet steam. Any
waste fine materials that are just compressed, swell and fall apart usually
before the reach carbonization. This then fills the interstitial space with
fines, and increases the pressure drop across the bed. It shuts the gasifier
down, and yes you get large amounts of fines in the outlet gas, usually due
to channelling through the reduction zone. Combustible gas can still be made in
such circumstances, but will contain tar and a lot of CO2.</STRONG></DIV>
<DIV><BR>Has anyone experience in gasifying such fuel?</DIV>
<DIV> </DIV>
<DIV><STRONG>We have tested many of these briquetted combinations over the
years, and learnt long ago, that the only briquetting process suitable for
sealed hopper downdraft gasifiers, are made in a screw press type, with heated
dies to obtain a thermally bonded briquette. We tested these in Germany in
our Pacific Class, and behaved very similar to wood blocks. You can see one on
the Fluidyne Archive under Agricultural Fuels. <A
href="http://www.fluidynenz.250x.com">www.fluidynenz.250x.com</A>
Compressed briquettes are best suited as combustion fuel in a boiler or
stoves, not a gasifier.</STRONG></DIV>
<DIV> </DIV>
<DIV>The swelling from steam in the hopper causes bridging that did not occur
with the chunks, but that should be easily overcome, perhaps with a monorator
hopper?</DIV>
<DIV>Thanks,<BR>John Blount <BR><BR><STRONG>The swelling is the first
stage of disintegration, by which time the fuel can be quite soggy and not want
to carbonize until it begins to enter the oxidation zone at the nozzles. The
original fuel size block, either wood or briquette, does not change shape until
it enters the oxidation phase, then, a segmentation process begins of the char.
Because of the amount of fines released by compressed briquettes, the surface
areas increase rapidly changing all the gas making parameters, which end up
blocking the reduction zone.</STRONG></DIV>
<DIV><STRONG>A monorator hopper would not change the way the fuel segments at
oxidation, and possibly the only way that I can see you using these compressed
briquettes, is to see if they can be pre-carbonized in a charcoal making
process. I doubt if this would provide the thermal bonding of the
fines, which releases the lignin bonding (I think), and they might still
fall apart.</STRONG><BR><BR><STRONG>Hope that explains your
situation.</STRONG></DIV>
<DIV><STRONG>Doug Williams,</STRONG></DIV>
<DIV><STRONG>Fluidyne Gasification.</STRONG></FONT></DIV></BODY></HTML>