Re: GAS-L: IC Engine Using Dirty Gas?

[Claus Hindsgaul <claush@mek.dtu.dk>]

Wednesday March 21. 2001 07:37 vharris wrote:
> Do you have an opinion regarding whether or not an IC engine can be
> modified to run on hot / dirty producer gas?  If producer gas were run
> through a cyclone to eliminate most ash (the easy part), can an engine be
> operated at high enough temperature that tars won't condense prior to
> combustion?  Will tars mostly combust in an IC engine combustion chamber or
> do they just pass through the system mostly uncombusted?

Your question depends very much on the properties of the "dirty gas".

If you remove large particles, but the gas still contain SOOT, it may end up 
in the lubrication oil of the engine causing it to thicken. Well, soot is 
very similar to graphite, so depending on the engine, this may not be so bad. 
Change your oil more often.

If your gas contain LIGHT TARS (present in high amounts in up-draft 
gasifiers), some of these may be corrosive. Their willingness to combust in 
the engine rather than pass through to the exhaust is not well known (please 
prove me wrong :-) ). If they pass through, the carcinogenic PAHs should be a 
serious concern.
Some of the light tars will polymerise on the machinery surfaces leaving hard 
coatings on hot surfaces.
Currently research is going on here at DTU and RISOE in Denmark covering:
 (1) the breakdown of PAHs in IC engines fuelled by woodgas.
 (2) surface fouling caused by polymerisation of phenol and guaiacol.
This research is managed by Mr. Jesper Ahrenfeldt ja@mek.dtu.dk .

HEAVY TARS (much of the tars from downdraft gasifiers) condense at high 
temperatures (some do above 200-300C). You dont want to try to run your 
engine above these temperatures, so they will cause fouling. You'd better 
eliminate or remove these tars before fuelling your engine.

It all depends on your gas (and your engine)...

Sincerly
Claus Hindsgaul

-- 
Research Assistant Claus Hindsgaul
Danish Technical University (DTU), Dept. of Mechanical Engineering.
Phone: (+45) 4525 4174, Fax: (+45) 4593 5761
claush@mek.dtu.dk

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