[Gasification] Blue water gas...... Why bother?

[Thomas Reed]

Drew and All:

I generally agree - conventional producer gas burns very cleanly, leanly 
and quickly. 

However, when it leave the charcoal reaction zone the temperature is 
typically 750 C.  At this temperature the watergas shift reaction is 
very fast and converts extra H2O according to:

CO + H2O <==> CO2 + H2

This reaction is EXO thermic (and so, free) but at lower temperatures, 
(500C) for higher conversion you need time and a catalyst. 

I recently posted the thermodynamics of the Boudouard reaction.  Maybe 
I'll post this too if anyone's interested.

TOM REED      BEF

drew wrote:
> I agree with Doug, as far as I can tell, there is no point in converting 
> a low heat low hydrogen high CO gas to a high heat high hydrogen gas for 
> most uses, this is especialy true for gas to be used in IC engines.    
> The conversion requires energy, and will most often be inefficent 
> reducing the finial total energy available in the output gas.      There 
> may be some applications where a clean hydrogen gas from biomass is 
> desired (fuel cells?) but even then it would have to be carefuly 
> calculated as to weather it would be more efficent to use a conventional 
> imbert style system to run a genset, using electrolysis to split water, 
> and resulting in a pure gas stream.    It has been clearly shown that 
> the gas output from conventional gassifiers (when properly run by 
> knowlageable operators) has more than enough hydrogen to speedily ignite 
> the high CO gas produced.     Unless there is a very clearly defined 
> need for the higher flame speed gas, it doesn't seem to be worth 
> spending much time on.  
>
> Incidentaly I think (I have not tested this) a simple way of doing it 
> (inefficent though) using an imbert style system would be to use a small 
> double wall pipe that proceeds up the center of the reduction tube 
> through the grate,  the inner pipe would be a longer, going slightly 
> farther up the reduction tube, and the reduction tube would likely need 
> to be longer than is standard.   The inner tube would inject steam (care 
> would need to be taken not to reverse the gass flow in the system),  the 
> steam would react with the hot char reducing the char to CO, and leaving 
> the H free,   the resultant gasses are drawn down reduction tube along 
> side the steam tube, and then drawn into the outer pipe by suction.    
> The gas resulting from the normal gassification process exits as normal, 
> but it's heat value is reduced.      There are quite a few variations on 
> this idea, but the question seems to be why bother, given that IC 
> engines don't require it?
>
> My to bits
> Drew
>
>