[Gasification] slose coupling ic and gasifier (was Re: waterinjection of producer gas fired ic engines)

[Doug Williams]

Jim,

You suggest:

> such an afterburner might also be a reasonable way to extract the
> extra 6-10% carbon left in the charash in a downdraft gasifier.  pack
> it around the afterburner so its pyrolysis gases either enter the
> afterburner stream, or off gas into the gasifier itself, to be
> consumed in the combustion zone.

The waste char from the gasification process does not contain any pyrolisis 
gases, as they are produced in the distillation phase of wood into charcoal. 
If you want to make this char into gas with CO2, the temperature of the CO2 
passing "through" the char would need to be at least 1,000C, because 
reduction of carbon into CO stops at around 850C.

Using the waste heat to dry the fuel wood before gasification is one of the 
best uses for this heat if you do not have a use for hot water. Heat can be 
put back into the gasifier via the fuel hopper casing, rather than internal 
heat exchangers which can impead fuel flow.  This can create problems of 
distillation gasses forming faster than normal, which results in a 
fluctuation of the gas quality over the fuel charge consumption.

<like the kahle gasifier, which uses 20% recycled
>CO2 from the ic motor, with nice gains in efficiency from doing so

The Kahle gasifier is a charcoal gasifier, and it's design required the 
blast temperature of the charcoal to be quenched using the exhaust CO2, to 
prevent a melt down situation of the moving gas exit assembly. In this one 
instance, incandecent char temperature of over 1,000 C, can crack the C02 
into C0 and improve the efficience, but you cannot do this to a wood 
gasifier and get the same results.

> watch the heat, C, H and O go round and round.  the world is on fire .

Only if you can make it into gas first :-)

Hope this helps,
Regards,
Doug Williams,
Fluidyne Gasification.