Trials and other thoughts

["John Davies" <jmdavies@xsinet.co.za>]

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.