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<DIV><FONT face=Arial size=2><STRONG>Hi Mark and
Colleagues,<BR></STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2>> The question I have (what have I missed?) is
why the char from either<BR>> pyrolysis or gasification, from identical
feedstocks, would have higher or<BR>> lower ash? </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>There would seem to be the old issue of
terminology at work here, and added to this all the variations of the processes
being used. If the char is being made without air present to oxidize some of the
char, then ash is going to be minimal, as will the pH.</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2><STRONG></STRONG></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG> It was been explained to me many
years ago, that char resulting from gasification (downdraft in our case), is
highly porous and slightly activated. As a portion of the higher up char
dropping fresh from the distillation zone is consumed to create the oxidation
and exothermic heat to drive the whole process, this ash then cannot avoid
entering the porous char as the two descend into the reduction zone. Possibly
you could wash it out if there was a need to do so.</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>>I realize that feedstocks that slag on grates
during gasification<BR>> could affect this, but that aside: are we claiming
that a ton of chips<BR>> gasified v. a ton of chips pyrolyzed would have
substantially different<BR>> effects on soil pH? </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>The only time I have seen slagging is when
there is dirt or siliceous formations in the feedstock. Fast growing coppice tip
wood and leaves are full of potassium and sodium, and these are high ashing
fuels. You can also get higher ash in the gasification char if the beds are
operating more in a combusting mode rather than oxidation. The amount of pH
always affects how the growing medium behaves, so yes, there would be a
measurable difference between the char types.</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>>Potassium hydroxide is hard to gasify; where
does it go<BR>> or why is it less available? </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>Until the ash forms via oxidation of the
char, it's not released, not coated with tar.</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Or are we saying because gasifier char is a<BR>>
smaller (%) by-product--than pyrolysis char--its ash components will be at
a<BR>> lower concentration? </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><STRONG><FONT face=Arial size=2>It depends on who is saying what, and in
which context. High density chars produced from a retort for cooking and coking
applications should have in most cases, little or no ash at all. High
density raw fuels passing through a gasifier, give you the higher
quality chars with porosity and ash, which provide the soil bacteria with a
habitat to process the nutrients. High density chars probably may not
be the perfect bacteria habitat, but would help reduce soil particle
agglomeration. There is always more to learn about these things if you need to
know(:-)</FONT></STRONG></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>>Certainly, kg-for-kg of feedstock the
total amount of<BR>> ash will remain constant...won't it?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>Without a doubt absolutely
correct.</STRONG></FONT></DIV>
<DIV><FONT face=Arial size=2><STRONG></STRONG></FONT> </DIV>
<DIV><FONT face=Arial size=2><STRONG>--------------</STRONG></DIV>
<DIV><STRONG></STRONG> </DIV>
<DIV><STRONG>The above comments have been made as a result of controlling ash
formations resulting from high temperature gasification. More recent involvement
with char making systems, and the expertise of those involved with end use
applications, suggests that chars are not created equal, and we should be
careful on how we talk about them, or recommend their
application.</STRONG></DIV>
<DIV><STRONG>Hope this helps.</STRONG></DIV>
<DIV><STRONG></STRONG> </DIV>
<DIV><STRONG>Doug Williams,</STRONG></DIV>
<DIV><STRONG>Fluidyne Gasification</STRONG>.</DIV>
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