[Gasification] small scale charcoal making design

[Benjamin Domingo Bof]

Jim; congratulations. If you make an cave under your drum making fire "OUTER" leaving to access hot gasses. When start to give white fumes you can control it open and shut upper plate. Never must appears "blue fumes" indicating fire into drum. Charcoal must be made under 500 Cent degrees for less volatiles wasted. Use firewood under three inches diameter without any hollow place avoiding to make chimneys. You car start with overflow of firewood more or less five inches high but when fuel shrinkage to an half part and fumes turn to blue and gas is flammable ; charcoal are ready. Dont hesitate to ask us for any question.
  Regards ;Benjamin

jim mason <jimmason at whatiamupto.com> escribió:
  On Nov 26, 2007 4:30 PM, Thomas Reed wrote:
> Dear Jim:
>
> But fire on the top, fresh wood on the bottom is best of all and gives a
> good yield of charcoal (20-30%) PLUS a very combustible and very steady
> operation, since each layer of wood has to heat the next one below.
>

but is this not going to consume some amount of the char, as the air
first meets the char, not the pyro smoke?

the scheme you suggest is really a stratified downdraft that has had
its fire top out, then continue to run. i've run a unit as such to
make charcoal, but have not really characterized its efficiency.
musing on it i thought it would be a rather inefficient char maker for
the above "consume" the char reasons. if the fire is internal, fire
on top or fire on bottom isn't going to make any difference. it is
still burning in the char.

the vertical barrel method benjamin proposes is oddly what a local at
our shop decided to make last night. he was the one who surfaced the
original link. he decided it would be easier to put the barrel
vertical, with a hole(s) in the bottom for the pyro smoke to escape,
with the starting wood fire well wrapped around this hole. this
appears to be what benjamin is describing. still a retort design, but
without any piping required.

this seems to me more difficult to get the heat back into the barrel.
heat goes up. surfaces to which you are transfering heat are best
placed perpendicular to the heat flow for better gas/solid contact. a
horizontal barrel gives you much more horizontally oriented surface
area. or maybe with 80% volitiles in biomass, having adequate heat
for charcoal making is not the issue.

(btw, by weight, biomass is around 20% fixed carbon, 80% volitiles.
but by energy, what is the ratio? around what percentage of energy
in biomass is in the fixed carbon vs the volitiles, ignoriing the
diversity of ways in which the volitiles can come out, depending on
temp and residence time? tim asked me this last night, and i didn't
have a ready answer. )


jim













> TOM REED BEF
>
> jim mason wrote:
> >> Here's the instructables method of feeding the smoke back into the fire:
> >> http://www.instructables.com/id/How-to-Make-some-Charcoal/
> >>
> >
> >
> > here is a nice design for a small scale retort type charcoal maker.
> > this is an improvement on the classic 55 gal drum charcoal retort as
> > the volitile gas out pipe is buried in a wood fire, so the smoke is
> > burned even before it is flammable by itself.
> >
> > the smoke problem on charcoal makers is during startup, when the smoke
> > is mostly steam, and thus not flammable. you need to vaporize all the
> > water out of the wood before the gas quality will get reasonably high
> > and burn. in practice, there will nearly always be some combination
> > of steam and tarry pyrolysis smoke. and the transition to an
> > adequately energy dense gas to burn can be long, and the smoke
> > produced voluminous.
> >
> > a retort design like the above is much more controllable than a "fire
> > in the bottom and raw biomass on the top" design. such are famously
> > smoky. properly started, this design can make charcoal without nasty
> > smoke.
> >
> > better insulation, flue gas control, and temp sensors could be added
> > for controlled temp char making.
> >
> > jim
> >
> >
> >
>
> --
> ÐÏ à¡± á
>
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-- 
--------------------------------------------------------------------------------
jim mason
website: www.whatiamupto.com
current project: mechabolic (http://www.mechabolic.org)
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