I have "lurked" on this list for many years--I suppose it's now time
to come out of the closet. I built my first working gasifier in 1983
after reading the Mother Earth News article on their wood-gas truck. I
would guess that most of the "old-timers" who built gasifiers took
their inpiration from that article also.
Back then, I had read a little about molecular sieves, but in those
pre-Internet days information was hard to find. I had always been
curious about how such a low-BTU gas, composed of 65% Nitrogen, and
the rest Carbon Monoxide, and to a much lesser degree Hydrogen, traces
of CH4 (methane) and un-converted CO2 could even power an IC engine AT
ALL!! Considering that cleaned and filtered wood gas, as it enters the
carbeuretor is mixed yet AGAIN with atmospheric air containing about
78% Nitrogen in about a 1--1.1 ratio--before being burned in the
cylinder combustion chambers, the combustible portion of wood gas is
quite small. The huge quantities of Nitrogen just "go along for the
ride" and contribute NOTHING (so far as I am aware!) But since my old
Allis-Chalmers WD-45 4 cylinder tractor, and a single-cylinder 13HP
electrical generator ran reasonably well on wood gas I became a
believer.
I knew 30 years ago that there obviously were industrial processes for
separation of Nitrogen from Oxygen. Every time I exchanged Oxygen
cylinders on my welding rig took a big bite out of my budget, so I
assumed that the separation process must be prohibitively
expensive--especially for putzing around making wood gas.
I read with much interest an article in Popular Science circa
mid-to-late 1980's about Tom Reed's project in Colorado with an
oxygen-injected stratified gasifier. I always wondered what became of
that project, but suspected that the cost of, and amount of, oxygen
required kept the project from ever being commercialized. (I know that
Dr. Reed still contributes periodically to this list, so perhaps many
folks would be grateful for a historical update on that project. ;-))
I haven't done much with gasification for the past 25 years. It was
just a fun hobby that gave way to more important matters--like earning
a living! But I can't help but feel that with all the improvements and
breakthroughs in materials science, micro-controller sensors and
actuators, catalysts, etc. that gasification could become a viable
alternative energy option IF the Nitrogen problem could be solved.
I have a gut feeling that feeding pure oxygen into a gasifier to
produce nitrogen-free gas might be a net-energy loser. On the other
hand, instead of cumbusting wood-gas in an IC engine using atmospheric
air containing 78% nitrogen, why not inject pure oxygen into the
carbeuretor mixer with the wood gas? Instead of a ratio of woodgas to
air of 1:1.1 would be ratio not change to 5:1 woodgas to pure oxygen?
Without all the nitrogen dilution, it seems that the cumbustible
mixture in the cylinder would contain much more energy and deliver
that much greater a force to the piston\'s down-stroke. It seems that
an on-board oxygen generator with reserve storage could then scavenge
some power from the vehicle engine to continuously provide the oxygen
quantities required. Could oxygen generators ever be made in such mass
quantities as to be cost-effective used in this way?
Perhaps a greatly modified engine would be required to use oxygen with
woodgas. I've always been disturbed by how it is physically possible
for a virtually un-modified IC engine to burn wood gas and deliver
ONLY a 50---60% power de-rating burning woodgas at 150BTU/ft(cubic)as
opposed to say, Propane at 1000BTU/ft (cubic) or Natural Gas at
1200BTU/ft(cubic)? Does this mean that an ideal fuel for an IC engine
need only have 300BTU/ft(cubic) to deliver power at 100%, and
therefore gasoline, propane, and natural gas are all way too BTU-rich
to be using as engine fuels?
I've read that after fuel is combusted in an IC engine that only
8--12% of the energy in the fuel actually propels the vehicle due to
mechanical losses in the engine itself, and in the drive train to the
wheels. Does this mean that such mechanical losses are unavoidable and
would be the same even if the prime mover was an electric motor? Or
does it mean that the step at which fuel is converted into mechanical
energy through combustion in the engine is a huge energy loser?
I've also read that most of the "nasty" by-products in automotive
exhaust have the word "nitrous" in them. Is that because the
combustion air contains 78% (benign) Nitrogen which becomes fouled in
the presence of the combustion of fuel and oxygen?
O.K. I think I just thought of the answer to why one can't use 100%
oxygen to fuel an IC engine using conventional fuels. My cutting
torch, because of the 100% oxygen mixed with acetylene can generate
temps up to 7000F. I can guess an IC engine would run so hot that it
would seize up in no time--maybe even melt. Bad idea! But then, maybe
with BTU-poor woodgas, that wouldn't be a problem? Enough rambling....
To anyone who's read this far, I apologize if I've wasted your time. I
just have questions and speculations that I've never seen any good
answers to. To anyone who can take the time to enlighten me, either
on- or off-list I'd be most grateful.
Chuck Frame
c/o Yonsei University
YSKLI
Seoul, KOREA Quoting Anand Karve <[email protected]>:
Dear Friends,
thanks for enlightening me about molecular sieves. From the information
received from members of the gasification and pyrolysis group, it appears
to be within the realm of possibility to produce pyrolysis gas without
nitrogen. This opens up the possibility of bottling nitrogen free producer
gas and using it as automotive fuel. Even a TLUD stove would burn much
better if supplied with primary air without nitrogen.
Yours
A.D.Karve
--
***
Dr. A.D. Karve
Trustee & Founder President, Appropriate Rural Technology Institute (ARTI)
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