[Gasification] Producer gas without nitrogen

[Charles Frame]

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 <adkarve at gmail.com>:



> 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)
>