[Stoves] 40% yield of charcoal

[Peter Singfield]

Dear AD;

Very interesting indeed. I have much of the Hawaii work achieved on my hard
drive -- but most of that to do with super critical water. 

The India demystified report is a clear indicator of the process.

You mention:

>This charcoal is
>however of a poor quality, because when one ignites it in a stove, the
>volatiles escape from it, giving rise to smoke and soot.

Meaning a stove specially designed to combust such fuel need be developed.
I am quite sure the one I have on my bench now will -- 

Also -- one could experiment using such as a gasifier fuel -- the advantage
being it is a quite "uniform" fuel -- should always have the same humidity
-- and fuel value -- unlike whole biomass fuels exhibit.

The Hawaiian process used pressures of 28 MPa (4061 PSI) 

This to reform biomass directly to synthesis gas -- and ran at 720 C -- in
a super critical water bath device.

The biomass being introduced as a water based slurry.

Make good sense to go for pyrolysis -- and at but 200 C

You mentioned:

>The
>volatiles that normally escape from the biomass in the process of pyrolysis,
>are not allowed to escape because the biomass is under pressure.

Considering that as "saturated steam of 200 C" -- pressures would be:

220 PSI

Also a much more reasonable working environment.

Is that indeed the operating pressures of their experiments??

Further -- if one vented steam -- replacing with sufficient water during
the pyrolysis -- to maintain a steam flow of 200 C -- that steam would be
easy to separate (simple condenser) from any pyrolysis gasses so produced
-- and those gasses could then fuel this conversion. Which -- though would
result in a lower percentage yield -- would produce -- potentially -- a
cleaner charcoal.

Peter / Belize


At 11:37 AM 6/9/2007 +0530, you wrote:
>Dear Stovers,
>For the last couple of years we have been reading in this forum about a
>charcoal making process that yielded almost 40% char. This process was
>developed in Hawaii. All that was revealed about this process was that it
>was conducted under pressure.
>A chemical technologist in Pune (India), with whom we are collaborating in
>another project, demystified this particular charcoal making process.
>According to him, the Hawaiian process mimicked the formation of mineral
>coal in nature, where biomass got heated while buried under tons of soil and
>rock. One can imitate this process in a laboratory by filling wet biomass in
>a pressure vessel and heating it to 200 degrees celsius.  The water in the
>biomass gets converted into steam, which exerts pressure on the biomass. The
>volatiles that normally escape from the biomass in the process of pyrolysis,
>are not allowed to escape because the biomass is under pressure. As a
>result, the tar is retained in the charcoal, adding to the weight of the
>charcoal. That is the secret of the 40% charcoal yield. This charcoal is
>however of a poor quality, because when one ignites it in a stove, the
>volatiles escape from it, giving rise to smoke and soot. Autoclaving
>distillery effluents with high organic content at 200 degrees C, under
>pressure, is already being practised in some distilleries in India, as a
>measure of pollution control.
>Yours
>A.D.Karve
>
>
>
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