[Stoves] CO/CO2 compositions from equilibrium and pyrolysis...

[Thomas Reed]

Dear Alex and all:

It is important to distinguish between thermodynamically stable and 
"prompt" CO.  C and CO2 react according to the Boudouard equation

C + CO2 ==> 2 CO

The equlibrium favors CO2 at low temperatures (below 700 C) and CO at 
high temperatures(above 900C).  However, kinetically the forward 
direction is very fast and makes CO easily, while the reverse reaction 
requires a catalyst and is much slower. 

We calculated the data I showed for equilibrium conditions.  However, it 
neglects "prompt CO" formed from less stable biomass during the initial 
pyrolysis stage. 
I believe that once a C is attached to and O as in C6H12O6 sugars and 
C6H10O5 cellulose and starch, it is released as CO during pyrolysis.  
This accounts for the high CO at pyrolysis temperataure (450 C).

Lots of mysteries remain.

Yours truly,  TOM REED        BEF



Alex and Christine English wrote:
> Dear All, especially Dean,
>
> Perhaps Dean could extinguish the flame on the charcoal maker he is working with,
> and get us a CO/CO2 ratio and PM on the unignited gases and aerosols.
>
> Years ago I measured CO and CO2 before the flame in a T-LUD and got quite different 
> results from those quoted below. If I remember it was ~ 10% CO and 20% CO2.
>
> Alex
>
>   
>> However, the flaming pyrolysis in the WoodGas stove produces a gas that 
>> is closer to
>>
>> H2 - 31%; CO-27%; CO2-7%; H2O-5%; CH4 - 2%; and N2 - 25%.  The energy 
>> content is 210 BTU/ft3 or 8.4 MJ/m3.
>>
>>     
>
>
>
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