Dear Pete
An "ideal situation" would be if you had a constant flow rate of air, which you
then flowed through such chips screened to different sizes. Then you could
measure the pressure drop across a length of the bed. This would tell you just
how much pressure drop various sizes of chips would give you. Then you could
decide how small a chip size you could consider using.
"Too small a chip" will likely give tar, unless the gasifier is specifically
designed to handle such fine chip sizes. However, this is a lesser concern for
gasifiers producing "Heating Grade Gas."
Best wishes,
Kevin
----- Original Message -----
From: Pete & Sheri
To: 'Discussion of biomass pyrolysis and gasification'
Sent: Wednesday, April 11, 2012 6:59 PM
Subject: Re: [Gasification] Wood Chip classificaton
Hi, Kevin.
Thanks for the input. I had better go out and check the sizes of my screens.
I realize that the APA gauge is focused on thin chips for pulping. But you
folks have been telling me that I need thicker chips (in relation to the length
and height). I have actually been using a 3 screen system, with a smaller
screen (1/4" X ΒΌ") to get the dust out before I even think of saving anything.
But even with the 1X1 screen, I could get chips that are only 1/32" thick,
and therefore, very light in weight.
I am learning that those chips may be okay in some circumstances, but I want
to be able to see the difference for myself.
I still have a long way to go.
Pete Stanaitis
----------------
From: [email protected]
[mailto:[email protected]] On Behalf Of Kevin
Sent: Wednesday, April 11, 2012 2:47 PM
To: Discussion of biomass pyrolysis and gasification
Subject: Re: [Gasification] Wood Chip classificaton
Dear Pete
I would suggest that a simpler, and better way to evaluate wood chips is to
use a "Two Screen System." For example, if you used square mesh screen with
1/2"x1/2", and 1"x1" openings, you would end up with 3 products:
1: +1"
2: -1", + 1/2"
3: -1/2"
The APA Gage is intended for a different purpose... to give a reflection of
wood fibre length, because that is what is important to Pulp Mills. For
gasifier applications, uniformity of size, and the percentage of void space is
what is important. The "two screen system" should give screened chips from
"between the screen decks" that are much more uniform, and having much better
gas flow characteristics.
Best wishes,
Kevin
----- Original Message -----
From: Pete & Sheri
To: [email protected]
Sent: Wednesday, April 11, 2012 3:37 PM
Subject: [Gasification] Wood Chip classificaton
My only interest for gasifier fuel is wood chips. If I can't understand
them and make them work well, I won't be using a gasifier at all.
I know this may be old news to many of you, but I recently found a couple
of ways to characterize wood chips. Although there are plenty of good systems
out there the best ones are way to complex and expensive for me.
So, I am using a simple gauge from the APA (American Pulpwood Association.
My simple page to explain the process is at:
http://www.spaco.org/Woodgas/WoodChipMeasurement.htm
It has links to a couple of in-depth sources for understanding wood chips,
too.
Pete Stanaitis
----------------
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