Re: GAS-L: Gasifier questions

["Kevin Chisholm" <kchishol@fox.nstn.ca>]

Dear Tim
...del...
>I envision a retangular hopper with a triangular grate/reaction/pyrolisis
chamber. Am I crazy?

Why would you want to do this?
>I am basing my design on a very effective wood fired boiler that I have
seen (Menonite made).

There is a major difference; in a gasifier, the gases must flow through the
bed. They don't have to in a boiler.

>The fire box was deep and wide and tilted down to a point in the back of
the stove. This made it easy to load and obviated bridging problems. The
design I envision would also allow differing sizes of "hoppers" to be used,
to allow for system size adjustment etc.

>I don't deal with circular fabrication as well as I do with flat surfaces
and planes. I am a structural guy...no longer mechanical....sigh.
Additionaly, my "shop" isn't such that I can undertake anything but the most
rudimentary fabrication.

OK... then find a round tank. :-)

> As to air flow at the corners, I anticipate feeding the process with a
standard size black iron pipe cast into a ferro concrete grate, said pipes
being fed via a double manifold. I will position said oxygen supplies to
minimize the "corner" effect.  I also intend to stagger the feed pipes side
to side to minimize any areas in the reaction area that might result in less
than maximum reaction.

I think you wil find that a round system will be much better, in terms of
the potential to get uniform reaction. This will certainly be the case for
chipped fuels. With stick wood, a case can be made for rectangular gasifying
chambers, but wood lengths should be very uniform, and close to the length
of the gasifying chamber.

>I am still analysing the description of the Imbert gasifier in my copy of
"Handbook of Biomass Downdraft Gasifier Engine sytems". I suspect the final
layout and design will only be determined by experience with a working
gasifier.

2) Rather than using the gas at the time of generation, I plan to compress
it (similar to LPG) for use later or as needed.

> Is there compelling reasons for NOT doing this?

Yes, indeed. The capital, energy, and maintenance costs associated with a
compressor.

>OK, here's the deal. I am off-grid. Supplying electricity for a fan is a
"no-go" situation for me. Additionally, I intend to filter my gas with a wet
system filter (gravity fed water-bath over charcoal filter). After
filtration, I intend to further cool my gas, as well as precipitate any
remaining tar in my gas with a counter weighted "accumulator" surrounded by
a water bath/cooler/seal.

>It is my intention to size the accumulator and hopper such that the fuel in
the hopper is close to exhausion at about the time that the accumulator
reaches capacity. The counter weights on the accumulator will be sized to
provide the neccessary draft thru the reaction chamber......thus no
electricity required for operation.

 The interior of the accumulator is under vacuum? If there is any
possibility of air leaks, then you might be making explosive mixtures.
However, it is a cute concept to generate draft without a fan.

>The compressor  would, in this case consist of a suitable small horse power
engine that would be run at the begining of the gasification cycle to
compress the gas into storage tanks, return the accumulator to it's empty
position and fill the cooling water gravity feed tank all at once. Said
engine to be fed by the already produced=and coloed gas. All the above being
done as the hopper was being re-filled, the pre-drier filled, the fire
restarted, flaring off the "pre-gas".......etc.

I gather you are running a "batch" type of peration?

>I anticipate compressing to 180 psi at ambient temps (30 to 90 F) in order
to avail myself of commonly available LPG valves, tanks, fittings and
gauges.

180 psi isn't much. You will need very large tankage to store a decent
amount of energy.

> As noted above, my intent is to use readily available  "off the shelf"
components to minimize costs. My LPG guy tells me their systems are rated at
180 psi.

Just because they are available and will work under your selected conditions
doesn't mean its a good idea.

What do you want ot use the gas to accomplish?

>In the first incarnation of this system, I would like to replace the 5
gallons of gasoline that I purchase each week for electrical generation. I
would like the system to operate well enough that I could store enough
"energy" for a week or two in advance. LPG storage tanks are relatively
cheap, if you have sufficent gas of decent quality to fill them with.

Have you determined how many LPG storage tanks you would require to store
the energy content of 1 gallon of gasoline at these low pressures?

>Eventually, I would like this system to supplant all my fuel needs for 2
trucks, 2 tractors, 2 generators, and my wifes' car.........and if I can
replace my wood stove with a thermostatically controlled natural gas heater
run on wood gas......GREAT.

Is there a possibility that you might be better off converting the
generators to gasifier fuel, and use direct wood heating for your home?

>Even better, if I can run my cook range, water heater and propane
refrigerator, I will be completely energy independant......VERY COOL.

Yes, it would be neat.

Kindest regards,

Kevin Chisholm



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