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

[Mark Ludlow]

Drew,

At atmospheric pressure, steam is H2O at least until 816 degC (that's as
high as my steam tables go). What happens at the interface of this
superheated vapor and glowing charcoal is different from the behavior
outside of this local zone.

I'm not certain what Dr. Reed refers to when he implies that
exothermic=free. It seems to me that chemical energy that may have been
available to subsequent useful combustion is spent in the conversion. The
fact that it is exothermic implies that the results of the reaction will be
at a lower free energy level. I've been wrong before!

Mark

-----Original Message-----
From: gasification-bounces at listserv.repp.org
[mailto:gasification-bounces at listserv.repp.org] On Behalf Of drew
Sent: Friday, November 24, 2006 4:47 PM
To: Thomas Reed
Cc: gasification at listserv.repp.org
Subject: Re: [Gasification] Blue water gas...... Why bother?

The water shift reaction can happen at 500C ?   I would love to hear 
more about it.    Am I correct in saying that a secondary function of 
steam injection/water gas shift at this point could be to quench the 
gas, keeping any CO from converting to CO2 and C (soot)?   
    Does this mean that steam at 750 deg, is not H2O as a gas but two 
separate free gasses, and if so what would be the lowest temp at which 
separation occurs?   

Drew



Thomas Reed wrote:

> 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


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