[ethos] RE: [Stoves] Charcoal Stoves (Thomas Reed)

Mon Jun 19 09:32:15 CDT 2006

Dear Paul,

Let's do it!

Best,

Dean

-----Original Message-----
From: Paul S. Anderson [mailto:psanders at ilstu.edu] 
Sent: Monday, June 19, 2006 4:47 AM
To: Dean Still
Cc: STOVES at LISTSERV.REPP.ORG
Subject: RE: RE: [ethos] RE: [Stoves] Charcoal Stoves (Thomas Reed)

Dean and all,

Because we are dealing with charcoal and an insulated chimney, here are two
issues that are related:

1.  Are the gases (we expect mainly CO) completely combusted in the 
lowest part
of the chimney, or does the combustion need the time and mixing in the 
vertical
chamber to obtain the combustion (and measured low CO reading at the top)?

To test this we need the existing structure that Dean has, and another 
one that
has a large-diameter insulated chimney into which the cooking pot could be
placed (with appropriate gap for flow of the hot gases and measured distance
from the coals to the bottom of the pot).

If the cold pot (even with boiling water, the insides of the pot are 
never above
100 C) is quenching the CO so that it cannot be combusted, then higher CO
readings will be found in the exit gases.

2.  As is already known to most Stovers, the improved air movement 
caused by the
chimney can also be created by a small fan.  The advantage of the fan is
that
the pot can then be down very close to the coals.

A controlled and measured comparison of fan vs. chimney would be very
informative.  With fans as one of the themes for Stove Camp this year, 
it would
be nice to have one run of this comparison done before the camp and then
available again to do it at the camp with attendees looking at changes of
variables such as fan velocity and chimney heights.

What has been done already concerning "forced-air" charcoal cookfires?

Paul
-- 
Paul S. Anderson, Ph.D., Geography professor - Emeritus
Telephone:  USA-309-452-7072 (residence and office)
Internet site:  www.ilstu.edu/~psanders
For my gasifier stoves info, go to:
http://bioenergylists.org/contributors#Paul_Anderson

Quoting Dean Still <dstill at epud.net>:

> Dear Kevin,
>
> The "tall insulated chimney" that Tom refers to was 33cm tall made from
> light weight fire brick material. The charcoal was placed at the bottom of
> this cylinder on a grate which allowed room air to pass up through the
> burning charcoal. We'll make a video of it this week.
>
> Best,
>
> Dean
>
> -----Original Message-----
> From: stoves-bounces at listserv.repp.org
> [mailto:stoves-bounces at listserv.repp.org] On Behalf Of Kevin Chisholm
> Sent: Sunday, June 18, 2006 7:20 PM
> To: tmiles at trmiles.com; 'stoves list'
> Cc: ethos at vrac.iastate.edu
> Subject: Re: RE: [ethos] RE: [Stoves] Charcoal Stoves (Thomas Reed)
>
> Dear Tom and Dean
> ----- Original Message -----
> From: "Tom Miles" <tmiles at trmiles.com>
> To: <tmiles at trmiles.com>; "'stoves list'" <stoves at listserv.repp.org>
> Cc: <ethos at vrac.iastate.edu>
> Sent: Sunday, June 18, 2006 11:45 PM
> Subject: RE: RE: [ethos] RE: [Stoves] Charcoal Stoves (Thomas Reed)
>
>
> ...del...>
>> Either way it looks like the techniques Dean has used to reduce CO (tall
>> insulated chimney - might improve CO and efficiency for a wide range of
>> charcoal qualities.
>>
> There is a lot of good to be said for chimneys:
> 1: They vent the products of combustion outside the living space, and
> virtually eliminatre concerns for Indoor Air Quality.
> 2: The draft they create allows the Strove Designer to get much better
> control over primary and secondary air, to give combustion which is much
> more complete.
> 3: They permit the efficient use of a wider range of fuel conditions, for
> example, smaller size, and higher moisture content.
>
> Up with Chimneys!! :-)
>
> Best wishes,
>
> Kevin
>
>> Tom
>>
>>
>> -----Original Message-----
>> From: stoves-bounces at listserv.repp.org
>> [mailto:stoves-bounces at listserv.repp.org] On Behalf Of John Hofmeyr
>> Sent: Sunday, June 18, 2006 4:52 PM
>> To: stoves list
>> Subject: Re: RE: [ethos] RE: [Stoves] Charcoal Stoves (Thomas Reed)
>>
>> Hi Tom and others,
>>
>> In Message-ID: < <mailto:44948947.5070903 at comcast.net>
>> 44948947.5070903 at comcast.net> Tom Reed wrote: 'The question of
>> "combustability" and efficiency is very complex.  Conventional charcoal
>> made
>> for cooking represents a "buffered endpoint" in charcoal making.'
>>
>>
>>
>> Questions were raised about the CV and volatiles content of charcoal with
>> respect to its efficiency in cooking. I wonder whether the fixed carbon
>> content is maybe a more important consideration, because this is the
value
>> which will translate into the utilisable energy, especially for grilling,
>> simmering and stewing.
>>
>> I introduce this idea, because, while the energy in the volatiles is
>> important for ignition, I think this energy is likely to be burnt off
>> rapidly?
>>
>> Therefore, would this energy only be useful, for example, to bring a pot
>> to
>> the boil?
>>
>> If yes, would the energy from the glowing charcoal be recoverable more
>> efficiently and over a longer period?
>>
>> And would this energy be maximised if the Fixed Carbon content of the
>> charcoal is maximised, but with balanced volatiles for ignition (about
>> 12-15%%, dry basis)?
>>
>>
>>
>> I think it is for this reason that the EU specifications for charcoal
tend
>> to require a fixed carbon content above 80%, to ensure smokeless burning
>> and
>> to avoid rapid burn-off  of volatiles.
>>
>>
>>
>> Further, on  Sent: Monday, June 05, 2006 3:35 PM Dean wrote: "2/3rds of
>> the
>> energy in wood is lost when making it into charcoal."
>>
>>
>>
>> Properly-carbonised wood returns ~70% of its CV as solid, in the form of
>> biocharcoal with Fixed Carbon >80%.
>>
>> By this I mean for example:
>>
>> 12000 tpa wood at 25% moisture equivalent to 9000 tpa bone dry at
>> 19GJ/ton,
>> yields 4000 tpa biocharcoal (80%FC) at 30GJ/ton.
>>
>>
>>
>> Regards,    John in Joburg
>>
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