[Stoves] Charcoal Rocket Stove, Charing in a"low-cost retort kiln"ICPS

[adkarve]

Dear Crispin,
since the biomass to be charred is enclosed in a drum, it does not get any
oxygen. So any heat applied to the drum, from the outside, would not burn
the char already formed inside the drum. In case a small part of it were
actually to burn, the CO2 would drive the oxygen out and eextinguish the
fire.
Yours
A.D.Karve
----- Original Message -----
From: Crispin Pemberton-Pigott <crispinpigott at gmail.com>
To: Discussion of biomass cooking stoves <stoves at listserv.repp.org>
Sent: Monday, June 11, 2007 12:25 PM
Subject: Re: [Stoves] Charcoal Rocket Stove,Charing in a "low-cost retort
kiln"ICPS


> Dear Chris and Jim
>
> First, that is a good idea, Jim.  And it provokes a question for Chris:
>
> If I have an upside down Karve-drum with biomass in it and a hole in the
> bottom, and I roast it in an enclosure until the gases start to come out
> which feed the fire, and the fire burns with those gases only, does it
come
> to a stop by itself?  What if I keep supplying air to the system using,
say,
> a chimney drafting air through a system which is now nice and hot?  Will
it
> continue to burn at least some of the charcoal?
>
> I was looking at Jim's suggestion and thinking of the Hoffman kiln where
> there are perhaps 24 rooms linked in a chain.
>
> Stage One
> The charcoal could be made in one room and then if the fire was self
> extinguishing, it would go out by itself.  The hot combustion products
would
> be directed into the adjacent room two.  The next room would have to be
> ignited on command at a certain time.
>
> Stage Two
> The second room, in a Hoffman kiln, receives air preheated by passing
> through the first room.  This cools the first room and raises the thermal
> efficiency of room two.  If the charcoal in the closed , but perforated
> drums in room one does not continue to burn, the Hoffman principle will be
> useable.
>
> Stage Three
> The idea is that in room three, the exit gases from room two are
preheating
> the load even as the retained heat from room one preheats the air.  When
> room three is burning, both rooms one and two provide preheating.
> Meanwhile, the heat left over after pre-heating room three passes to room
> four and so on to the exhaust point.  In full swing, there are several
> cooling rooms giving up heat to the air going to the room-on-fire, and
> several getting preheated by the combustion products.  There are lots of
> gates that control the air so the process can move in a circle
continuously.
> This is how bricks are often made.  Such a process is extremely efficient.
> I measured 550 degrees preheating at CIMOC's brick factory in Boane
outside
> Maputo (just to put a number on it).
>
> With charcoal making, there is enough heat available in the biomass
> volatiles that there may be no need to light a fire more than once in the
> beginning.
>
> I foresee two problems: the drums will vanish in the hot, oxygen-rich air
> after a few 'rounds' and there might be a massive, unexpected  production
of
> unburned combustible gas somewhere in the middle of the system after it
gets
> going.
>
> Maybe it is safest to do it in a single 'charge' of perhaps 10 or 20 pairs
> of drums.  maybe even a single line.  Chris: how about a snake of mud
brick
> walls that allows one drum after another to be set alight in a chain?  The
> drums are put into a grid pattern but the fire proceeds in a snake-like
> fashion through them?
>
> Regards
> Crispin
>
>
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