Dear Tim
----- Original Message -----
From: "Tim
Bollman" <tbollman@twlakes.net>
To:
<gasification@crest.org>
Sent:
Thursday, November 29, 2001 4:50 PM
Subject: GAS-L: Questions about
gasification
All,
I anticipate building a gasifier
system in the not too distant future and
two questions keep arising
about my "mental" plans.
1) Virtually all gasifirer designs I have
seen have been cyndrillical or
drum shaped.
>Is this due to
availability of drum shaped containers, to avoid bio mass
"bridging",
ease of construction, other, or all the above?
Yes, yes, yes, yes,
yes, and yes.
One of the "other considerations" is gas flow.......
hard to get gas to flow
to the corners.
>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).
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.
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 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 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 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.
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.
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.
Even better, if I can run my cook range, water heater
and propane refrigerator, I will be completely energy
independant......VERY COOL.
Thanks again
Tim
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