[Stoves] 40% yield of charcoal

[Michael J Antal]

Dear Peter: our supercritical water that you refer to below was aimed at hydrogen production from wet biomass.  One feature of supercritical water gasification of biomass is that it produces no char.  Consequently, the papers you refer to have nothing to do with our charcoal research.  If you are interested in our charcoal research, please contact me and I will be glad to send you the appropriate papers.  Regards, Michael.

----- Original Message -----
From: Peter Singfield <snkm at btl.net>
Date: Saturday, June 9, 2007 9:05 am
Subject: Re: [Stoves] 40% yield of charcoal
To: stoves at listserv.repp.org

> 
> 
> 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 
> advantagebeing 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 
> duringthe 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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