[Stoves] SPAM: ***SPAM*** Re: Design for a stove/heater for making biochar
Crispin Pemberton-Pigott
crispinpigott at outlook.com
Wed Feb 22 17:32:46 CST 2023
.Here are some photos from that upgrading exercise in 2010. First note that there was too much air getting into the lowest part of the fuel bed. Here are the holes remaining:
[cid:image003.png at 01D946DA.A40BC570]
The plate at the bottom is the one that would be adjusted up or down to vary the treatment of the char. As shown above, the fire has not yet started.
Here is the fire with added secondary air. These days I would do it differently – larger holes, further down, none towards the top of the chamber.
[cid:image004.png at 01D946DA.A40BC570]
This plate was added to the top.
[cid:image006.png at 01D946DA.77C14530]
Pot on:
[cid:image001.png at 01D946DB.4396D1C0]
The char as it dropped out. Note the metal covering some of the original holes.
[cid:image007.png at 01D946DA.77C14530]
Good combustion most of the time:
[cid:image008.png at 01D946DA.77C14530]
That is a CO/CO2 ratio of 0.2%. This is (almost) only obtainable with biomass when there is a clearly defined gasification process going on. High performance biomass and coal gasifiers can reach and sustain 0.03% if the excess air is under 90% (this means O2 concentration in the exhaust is <9.5%).
Regards
Crispin
-----Original Message-----
From: Tom Miles <tmiles at trmiles.com>
Sent: Wednesday, February 22, 2023 13:03
To: ajheggie at gmail.com; Discussion of biomass cooking stoves <stoves at lists.bioenergylists.org>
Cc: Crispin Pemberton-Pigott <crispinpigott at outlook.com>
Subject: Re: SPAM: [Stoves] ***SPAM*** Re: Design for a stove/heater for making biochar
Great suggestion. Thanks. I wondered if anyone had optimized the stove for combustion. Rice husks tend to smolder. Removing char faster than it is consumed has become a common way to make char. I like the adjustable gate and water quench.
T R Miles Technical Consultants Inc.
tmiles at trmiles.com<mailto:tmiles at trmiles.com>
Sent from mobile.
> On Feb 22, 2023, at 1:40 PM, ajheggie at gmail.com<mailto:ajheggie at gmail.com> wrote:
>
> Thanks for remembering the Mayon Turbo Stove Crispin, I was impressed
> with it but it had slipped my mind.
>
> Andrew
>
>> On Wed, 22 Feb 2023 at 17:56, Crispin Pemberton-Pigott
>> <crispinpigott at outlook.com<mailto:crispinpigott at outlook.com>> wrote:
>>
>> Dear Ashok
>>
>>
>>
>> There is a stove called the Mayon Turbo Stove designed by Roger Samson from REAP Canada in Montreal. This stove has been made is multiple countries. It is a rice hull gasifier. It can cook one pot. I suppose you could put an oven on top to bake.
>>
>>
>>
>> The relevance is that there is a cone-shaped fuel holder that is filled around the periphery with the flame burning in the centre, up a sort of short chimney. The fuel falls down the cone to reach choke point. That choke point can be made larger, smaller or adjustable.
>>
>>
>>
>> When the rice hull gasifies, it becomes char. As the char falls to the choke point, it can either fall out as char or be held for longer (because the choke is smaller) so it burns to ash. Your choice. If you created an adjustable choke point, probably a flat round horizontal place attached to a central threaded bar, you could have different sorts of treatment (in terms of temperature) and different yield percentages. The hot char falls out of the bottom onto the ground. You could just as easily have it fall out into a shallow bucket of water.
>>
>>
>>
>> This is a very clean burning stove and runs well on rice hull which is often a poor cooking fuel. It can be refuelled as you wish, which is unusual for a true biomass gasifier. You can reach Roger at rogerenroute at gmail.com<mailto:rogerenroute at gmail.com>. I think he sells drawings or some such. Not sure at the moment. It has been around for a long time, originally used in the Philippines.
>>
>>
>>
>> I have worked on this stove with some of his interns to improve the heat transfer efficiency and fuel combustion %, not to make char but to burn the fuel more completely. The idea of adjusting the outlet at the bottom to “tune for char” was not thought of at that time, but it was clearly an option. It is important to know that the original design, which features a short air pipe or two, did not have the correct air supply and a considerable improvement was made by altering the size and placement of the cold air entry from below. To optimise this you have to have a combustion analyser. If the drawings are from the 90’s, then this change has not been incorporated. As I recall the original design has far too much air entering the pyrolysis zone so the gas exit temperature (impinging on the pot) was cooled by it. The excess air level in a reasonable gasifier should be between 90% and 110% when building at the artisan level.
>>
>>
>>
>> You will see from the photos at the link above that it can be used tog gasify all manner of wood chips and agriwaste.
>>
>>
>>
>> Best regards
>>
>> Crispin
>>
>>
>>
>> New Dawn Engineering Inc
>>
>> Alberta
>>
>> Canada
>>
>> From: Stoves <stoves-bounces at lists.bioenergylists.org<mailto:stoves-bounces at lists.bioenergylists.org>> On Behalf Of
>> Ashok Mathur
>> Sent: Tuesday, February 21, 2023 6:30
>> To: Discussion of biomass cooking stoves
>> <stoves at lists.bioenergylists.org<mailto:stoves at lists.bioenergylists.org>>; ajheggie at gmail.com<mailto:ajheggie at gmail.com>
>> Subject: [Stoves] Design for a stove/heater for making biochar
>>
>>
>>
>> Dear All,
>>
>> This note is a slight deviation from the discussion on bio-char.
>>
>> Usually bio-char is made in drums that exclude air and are heated by electricity.
>>
>> Because of high capital costs and running costs, bio-char becomes uneconomical for farmers to use.
>>
>> Rice husk and rice straw are two materials that are freely available. They both can be used as the fuel to heat bio-char as well as the material that is pyrolyzed to make the bio-char.
>>
>> When they are coated with a slurry of sand and soil containing iron ore, they make a super bio-char for growing rice. There may be some disagreement with that statement but keep it aside for the moment. The ash produced is a good soil amendment.
>>
>> Has anybody designed/knows about an apparatus for producing bio-char using this material as a fuel and a substance to pyrolyze?
>>
>> Regards
>>
>> Ashok
>>
>> PS I am also looking for use of these materials to make baking ovens for biscuits and bread, flatbread etc.
>>
>>
>>
>> On Tuesday, February 21, 2023 at 05:34:37 PM GMT+5:30, ajheggie at gmail.com<mailto:ajheggie at gmail.com> <ajheggie at gmail.com<mailto:ajheggie at gmail.com>> wrote:
>>
>>
>>
>>
>>
>>> On Tue, 21 Feb 2023 at 03:06, Ronal Larson <rongretlarson at comcast.net<mailto:rongretlarson at comcast.net>> wrote:
>>>
>>> Although the term Pyrolysis used - and looks like a TLUd in some ways, there was zero mention of char. I’m pretty sure all the char was consumed - which is OK. Much better than starting with char made badly, and he’s probably right he has a clean stove.
>>
>> Yes he definitely says it is burned out to ash, so the top down burn
>> and the diffuse secondary flame will morph into an updraught charcoal
>> burn until only ash remains. This is interesting in itself as the
>> char will be burning out with a low superficial velocity of air and
>> I wonder what the implications of carbon monoxide in the exhaust are
>> if a secondary flame is not sustained in this second phase (and I
>> don't believe it can be).
>>
>> It wouldn't be that difficult to arrange for the air to be totally
>> shut off when the pyrolysis front reached the bottom but this too may
>> have implications for unburnt products at the end.
>>
>> Perceived wisdom is that to gasify the char in an updraught gasifier
>> and have a secondary flame of carbon monoxide would require ramping
>> up the superficial velocity of the air, probably requiring a fan.
>> This is normally avoided in TLUD devices because the temperature gets
>> far too high for the container.
>>>
>>> The most interesting thing for me was the material seems to be a cast ceramic.
>>
>> Yes I didn't pick up on what was in the concrete mix but it would be
>> something dense for it to function as a masonry stove, albeit top lit.
>> Probably high alumina cement??
>>
>> I wonder if Norbert Senf is still reading here and would like to comment?
>>
>> Andrew
>>
>>
>>
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