[Gasification] Fuel, sizes........

Greg Manning a31ford at gmail.com
Sun Nov 28 09:09:20 CST 2010

OK, First off, Greetings List(s)!


 Since my accidental discovery of smaller feedstock sizes about a week ago,
I've been doing some tests (ok, mad scientist stuff), to the acceptable
"Minimum" size level in my downdraft units.

 For those that do not know me, briefly, I build smaller downdraft gasifiers
(under 250KwT) I do NOT go bigger than that, I have my reasons.

I've been using a "standard" sized woodchip, typical of most small
industrial units (NOT your home "shredder/mulchers") generally 15-30 hp

These chippers produce, for the most part, chips about 3 x 3 x 0.25 cm chips
(3/4 x 3/4 x 3/16") and down to the point of dirt, or mash.

6 - 7 years ago, I had settled on a rotary screen design using a "fines"
screen of  0.63 x 0.63 cm  (1/4 x 1/4") square openings. this has been my
"smaller" size since then. (Until this week, we have always discarded
anything that was considered "fines", used these as mulch or horse bedding).

Upon the somewhat accidental use of a fines pile as feedstock, much to my
surprise, the unit accepted the fines for the most part, for about 8 hours
of operation, (these where raw fines, directly from under the rotary drum),
Yes the gasifier did eventually plug up and shut down BUT, not knowing what
was going on at the time (I did NOT know the unit was running on fines) I
was perplexed as to what had caused the problem, upon investigation, and
finding that the worker had inadvertently used this pile, instead of the
correct one, and finding out the length of the time the unit had ran on
them, I undertook the new question of "how small I can go" in feedstock

As it turns out, the unit will run consistently on a much smaller chip size
than originally thought. We have since changed the fines screen in the
rotary screener to 3/16" round holes (punched panel) on an offset pattern
(68% opening) the ratio change is as follows:

 Original 1/4 x 14" square openings, ratio of fines to acceptable feedstock
30% fines, 70% feedstock

 New  3/16" round openings, 10 - 13% fines, 87 - 90% acceptable.

Hoping that this information is useful to someone.
Kindest regards:
Greg Manning,
Canadian Gasifier Ltd.  (www.cangas.ca)
Building Hi-Performance Gasifiers, Since 2001

Brandon, Manitoba, Canada
1 (204) 726-1851

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