[Stoves] Charcoal from waste - home cooking or other markets? (Re: Crispin, Anand Karve)

Thu Oct 6 10:07:06 CDT 2016

Dear Dr. A.D. Karve & list

"Charcoal gas"  was slightly poor terminology on my part.  It will be a mix
of CO, H2, N2  with a little CO2 and traces of CH4.

There is the water gas reaction of H20 + C  to CO and 2H2  and the
reduction of CO2 into 2CO  when it comes into contact with orange hot
carbon.

Charcoal makes for a much simpler gasifier - because you don't have to
handle the problems of tar generation, as you would with a wood gasifier.

With charcoal available from biomass - and formed by extrusion into
convenient briquettes  - it makes the fuel handling a lot simpler,
briquettes can be stacked up in a pipe (or pipes)  and burn sequentially -
descending by gravity into the hearth of the gasifier.

Engine exhaust can be used to dry and pyrolyse the fresh briquettes and the
water content and CO2 in the engine exhaust is beneficial to the
gasification process - and helps moderate the temperature of the hottest
parts.

Ken

On 6 October 2016 at 06:30, Anand Karve <adkarve at gmail.com> wrote:

> Dear Ken,
> I looked up the sites quoted by you but I found the process to be quite
> complicated, using a lot of very elaborately designed hardware.   When you
> mention "charcoal gas", do you mean water gas (CO + H2)?  Water gas is
> relatively easy to produce. One can demonstrate its generation by
> introducing a small amount of water into a burning charcoal fire. As soon
> as the water hits the charcoal, a blue flame emerges from the fire.  I was
> told that water gas can also be used as fuel in an internal combustion
> engine.
> Yours
> A.D.Karve
>
> ***
> Dr. A.D. Karve
>
> Chairman, Samuchit Enviro Tech Pvt Ltd (www.samuchit.com)
>
> Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)
>
> On Wed, Oct 5, 2016 at 1:39 PM, Ken Boak <ken.boak at gmail.com> wrote:
>
>>
>> Dear Crispin, Anand, and stoves list,
>>
>> Regarding waste charcoal and other uses of charcoal fuel:
>>
>> I have recently restarted a project I was first involved in back in 2010,
>> which is the production of a biomass gasifier for village scale power
>> generation.
>>
>> This involved the conversion of a Lister 6hp engine to spark ignition to
>> allow it to run on syn-gas from a wood chip gasifier.
>>
>> My experiments were conducted at a workshop held at All Power Labs, of
>> Berkeley, California,  in February of 2010 and later in Spring of 2012 -
>> when I was fortunate enough to be working at APL for six months of 2012.
>>
>> During that time myself and a team of fellow enthusiasts converted the
>> Lister to spark ignition and proved that it would run at the elevated
>> compression ratio of 17:1 - as common in small diesel engines. This allowed
>> the Lister to perform well on syn-gas without the usual loss of performance
>> associated with running a standard low compression engine on gas.
>>
>> Since the initial experimental phase, I have come to believe that the
>> woodchip gasifier is a hard beast to tame, and that a charcoal gasifier is
>> a much simpler and forgiving technology and better suited to construction
>> and operation and repair - particularly in the rural setting.
>>
>> So this opens up the question of supplying charcoal in a form that is
>> compatible with the gasifier and in a quantity that satisfies the demand of
>> village scale distributed heat and power systems.
>>
>> The solution that I am currently researching is a charcoal gasifier that
>> has a pre-pyrolyser - as a means of producing the charcoal as an
>> intermediate fuel from assorted biomass.  The pyrolyser is initially driven
>> from the waste heat of the diesel exhaust and supplemented by the heat from
>> burning the pyrolysis gases, volatiles and tars - which otherwise would
>> potentially cause a problem later in the valve gear of the diesel engine.
>>
>> Whilst some say that converting biomass to char is wasteful in terms of
>> energy, and also prone to generating high levels of noxious pollutants,
>>  the solution of having a closed torrefier, closely coupled to the charcoal
>> gasifier, that consumes all pyrolysis gases - and makes the associated heat
>> available for other purposes - such as water heating, drying, roasting,
>> cooking, boiling etc  reduces the pollution to a minimum.
>>
>> It also allows a wide range of otherwise "difficult" agricultural waste
>> products to the converted to charcoal fuel in a form that can be used for
>> running the converted engine.  This includes the leaves, tree trimmings,
>> nut shells, husks, stones/pits, sawdust etc and any other wide variety of
>> waste products to be converted and used effectively as fuel for heat and
>> electrical and/or mechanical  power for running small agri-processing
>> machines
>>
>> In my estimation somewhere between 1.5 and 2kg of dry biomass will be
>> needed to produce 1kWh of electricity using a charcoal gasifier.
>>
>> For every kWh of electrical power produced about 4kWh of high grade waste
>> heat either as hot air for drying or hot water at 60C + will be available.
>>
>> For those requiring a refresher on the design of the charcoal gasifier -
>> I recommend a paper from 1942 "The Making of the Kalle Gasifier"  submitted
>> to the list by Tom Miles nearly 10 years ago
>>
>> http://gasifiers.bioenergylists.org/kallegas
>>
>> Additionally for small scale charcoal gasifiers made from scrap materials
>> - I suggest Gary Gilmore's design from 2010/11 - which is described in a 3
>> part YouTube series
>>
>> https://www.youtube.com/watch?v=srLETKDrwto
>>
>>
>> And from 2013 - his Simple-Fire gasifier
>>
>> https://www.youtube.com/watch?v=KAJXdaCQ6uQ
>>
>>
>>
>>
>> regards
>>
>>
>> Ken
>>
>> London
>>
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