[Gasification] Filtering Pyrolisis Gas

[Thomas Reed]

Dear Doug, Rolf and all:

We need to be more specific when talking about various charcoal processes.

Kiln charcoal making is said to produce approximately 1/3 gas, 1/3 tar and
1/3 charcoal!  I believe that the true charcoal yield can't exceed the
lignin content of the wood which is typically around 20%, so the above
numbers are for a charcoal that has reabsorbed more of the tars/volatiles.

TLUD charcoal making in my stove typically produces 15-20% charcoal, in line
with the lignin content.  I recently burned Mesquite chips and got a yield
of 35%!  Mesquite is said to have 64% lignin!  This would seem to confirm
it.

Lignin is a hydrocarbon and not digested by organisms other than termites.
You find large logs of pure lignin in many forests.  This lignin breaks
across the grain because the cellulose carbohydrate has all been removed.

Incidentally, lignin evolved 400 M years ago when life emerged from the
ocean and began to occupy Gonwandaland.  Lignin is necessary for vascular
plants that carry water up hundreds of feet.  At that time, Earth had an
atmosphere of > 20% CO2 and trees grew faster than they could be
biodegraded.  The result was buried wood which then became buried and formed
our coal deposits.

You can easily calculate from the pressure of the atmosphere and the
diameter of the earth that our atmosphere weights 5.5E15 tons, and so
contains 1.1E15 tons of O2, generated by photosynthesis.  Normally the O2 is
consumed when plants die, but there must be ~ 4E15 tonnes of sequestered
carbon, mostly coal to permit us the luxury of 21% O2 in our atmosphere.

Let's not upset the balance too much or too fast.

TOM REED      BEF
On Fri, Apr 15, 2011 at 6:21 PM, doug.williams
<Doug.Williams at orcon.net.nz>wrote:

>
> *Hi Rolf,*
> **
> *In answer to these two questions:*
> **
> I have also thought about the  cold char acting as a filter for the tars in
>
> the distillation fumes so as to enrich the biochar with these, but so far I
>
> have never found any comments on this.
>
> *Charcoal makes a good filter for particulates, but if the pyrolisis gas
> from a charcoal kiln is anything less than say 475C, the tars will just
> condense and quickly block the filter bed. You will also find the gas ducts
> will block if the temperatures drop.*
>
> The filtered gases would go through an engine to be completely burnt.
>
> *Unfortunately, this would be very unlikely to succeed, as pyrolisis gas
> would need to be wet scrubbed to grab all the condensable tars. The toxic
> black liquor is then a environmental disposal issue.*
>
> What do you use as a binder?
>
> *Depending on the type densification, you can use the tar if collected
> from a condenser, or more user friendly starch powders from a variety of
> crops.
> *
> *Hope this will help to keep your hands clean (:-)*
> **
> *Doug Williams,*
> *Fluidyne.*
>
>
>
>
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-- 
Dr. Thomas B. Reed
The Biomass Energy Foundation
The BioChar Engineering Corporation
www.WoodGas.com
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