Re: Trials and other thoughts

["S.C. Bhattacharya" <bhatta@ait.ac.th>]

Mr. Davies,

I suggest you start from the point up to which we have arrived after a great
deal of  of work. The stove can be used for a variety applications. For example,
it will be used for a  few biomass-fired dryers (for fruits ) in the
Phillippines. We presented our preliminary work on drying using this stove in
the World Renewable Energy Congress in UK last year. The output of the stove
could be automatically controlled to maintain the dryer temperature (using a
mechanical device requring no electricity).

Other applications (like space heating, as suggested by you) should definitely
considered.

S.C. Bhattacharya

I suggest

John Davies wrote:

> Hi All,
>
> I have built an experimental inverted downdraft Stove/ Gasifier to burn
> twigs, small
> branches and small blocks of wood.
> While the results have been promising, several unwanted characteristics have
> emerged.
>
> 1  The flame will not light until there is enough gas to produce a flame
> about 6" in height.
>
> 2. The flame at the burner remains a yellow- orange colour., although no
> smoke is evident.
> reducing the primary air leads to a loss of flame. I just cannot achieve a
> blue flame.
>
> 3  The flame grows quickly to a height of about 18" ( about 10 minutes ) and
> then diminishes and dies as all the fuel has been converted to charcoal.
> This charcoal then burns in the gasifier with reducing heat until exhausted.
> ( about 40 minutes )
>
> Here is a brief description of the unit.
>
> The base/ ash container, is a 5Li paint tin with 8
> X 1/2" holes  around the perimeter half way up. Short steel rods are
> inserted to throttle the air. The next component  is the gasifier which is a
> 6" Dia. tube 8" long ( tin can with both ends removed ) with a stainless
> steel mesh grate.
> A 1/4" plate with a groove fits over the top with a 2" pipe 12" long forming
> the gas outlet.
> The burner at the top of the pipe is the 4" dia. can with 5mm holes as
> previously described by another member. A short chimney of about 12" is
> placed over the burner ( made from cans ).
>
> Any ideas to improve the system will be welcome. I will send a sketch to
> anybody, but do not have a website to put it on.
>
> In the beginning there was no heat insulation applied. The flame would not
> keep burning without heat applied under the burner. Insulation in the form
> of a ceramic wool blanket was wrapped around the gasifier, the 2" pipe and
> the burner unit which led to a self sustaining flame, which continued until
> the gas production was too low as at the beginning of the burn.
> It would appear that there is no control over the rate of burning ( gas
> production ) . Have I missed something.?
>
> I had a good look at the system below: Which would appear to give a
> controlled burn plus have a fuel bunker built in .  This was on the site a
> couple of weeks back. It requires a bit more work than piling a bunch of tin
> cans on top of each other but could be worth the trouble.
>
> > The details of a natural draft institutional gasifier stove we have
> developed
> > can be found at the web site of a regional research programme funded by
> Sida:
> >
> > www.retsasia.ait.ac.th
> >
>
> This system gasifies and burns the fuel in a similar manner to the
> GPCS system in a locomotive boiler, using a combined driving off of the
> volatiles and burning of the remaining char in sequence. The main
> differences being that the air / gas flow is horizontal instead of upward
> vertical, and that the gas combustion is separated from the gasifier.
> Secondly the fuel hopper above the gasifier gives gravity feed of the fuel
> instead of a horizontal screw feed, or hand stoking.   Well done to the
> development team.
>
> I believe that this system holds the greatest potential for a simple home
> heating system, being easily modified to include the 3 heating requirements
> of cooking, water heating and space heating. If a small extraction fan was
> placed at  the end of the chimney,most of the heat generated could be
> extracted for these uses. otherwise some heat together with a long chimney
> will be needed to draft the system. I also see it being adaptable to clean
> coal burning.
>
> Maybe this should be sent to the stoves site, but where is the dividing line
> ?
> Should I sign up there as well ?
>
> Regards,
> John Davies.

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S. C. Bhattacharya                  Voice : (66-2) 524 5403 (Off)
Professor                                                       524 5913 (Res)
Energy Program
Asian Institute of Technology    Fax   : (66-2) 524 5439
PO Box 4, Klong Luang                                516 2126
Pathumthani 12120                   ICQ   : 18690996
Thailand                            e-mail: bhatta@ait.ac.th
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