[Stoves] why can't we use wood gas directly in an i.c. engine?

[Crispin Pemberton-Pigott]

Dear AD

 

I toured a few days ago a 250 kW gasifier built by YDD head Anton. It is a
semi-fluidised bed palm oil waste processing unit with a very interesting
split reactor, one side heated by steam. It has a ceramic catalyst that
looks like clay sand. It produces virtually zero tar. The stuff normally
'scrubbed' or condensed or washed out is simply not there because it is
fully reacted to gas.

 

As to why it has to be removed from engine fuel? The longer the chain of the
molecule (tars are long) the longer it takes to burn. In the
time-temperature-turbulence equation, engines provide very little 'time'.
If the residence time is very short (which it is, inside an engine
combustion chamber) it combusts incompletely, gumming up the piston. Anton's
system solves this by doing a better job of reacting it. The raw fuel is
available in vast quantities.

 

If you recall I sent some pictures last year of a 135 kW unit outside
Battambang in Cambodia. Tom Miles says there are 220 or so of them in the
country. It is an Indian design and produces waste products (black gunk)
that are causing pollution problems. The answer of course is simply not to
create the stuff. An interim treatment method is to dry it and feed the
black stuff back into the process. But obviously the answer is to deal with
it initial problem, not install subsystems to mitigate it.

 

If you put the tarry gas into a 6/1 Lister engine at 500 RPM I think it
would do well - better than in an 1800 RPM truck engine.

 

Regards

Crispin

 

 

Dear Stovers,

 fuel in the form of a combustible gas seems to be a pre-requisite for an
internal combustion engine. Even liquid fuels are atomised before
introducing them into the cylinder of an i.c.engine. Wood gasifies when
heated, but this gas is used in internal combustion engines only after
filtering out the tar. Why is it necessary to filter out the tar? Tar is
combustible and it is gaseous if the temperature is high. Stoves which
provide secondary air with the help of a fan have shown that the wood gas
can be completely burned, along with the tar, if enough air is provided to
it. So why filter out the tar before using wood gas in an i.c.engine?

Yours

A.D.Karve

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