I have a combustion equation with C3H8 as fuel in a rich operation regime. I want to maximize H2 and CO. How can I do this 2 together? If I maximize them at the same time I get a equivalent ration of 3,33 but if I do it just for CO I get a equivalent ratio of 1,43
Dear Miguel,
The most important chemical reaction that govern the CO/H2 composition in the mixture is water-gas shift reaction given as
CO + H2O CO2 + H2 (1)
If we give sufficient time for equilibrium to occur, composition can be obtained using chemical equilibrium analysis. As the Eqn. (1) suggest that CO and H2 composition can be tailored using CO2 and H2O. So you can introduce CO2 or H2O in the unburnt fuel-oxidizer mixture to shift the equilibrium. However, simultaneous maximization of both CO and H2 looks contradictory to me. What i can say for sure is you can get any ratio (CO/H2) by properly controlling CO2 and H2O in mass fractions in the unburnt fuel-oxidizer stream. Feel free to discuss
Thank you very much for the answer Syed Mughees Ali , it was already helpfull, but I wasn't clear enough, the issue is not about time to get the equilibrium but how rich (amount of fuel in the combustion) should it be to dissociate CO2 in CO and C and also H2O do H2, I have a picture of the original equation (without dissociation). My goal is to increase the equivalence ratio (fi) to dissociate CO2 and H2O but doing it by so have the maximum of CO and H2
How are you calculating the composition by the above equation by element balance. Kindly specify. If answer is yes then you inherently assuming chemical equilibrium. Again my answer remains the same if you see the water-gas shift reaction you cannot maximize both simultaneously. As the equation given by you ( i am not sure if this will happen in reality) suggest for a given equivalence ratio 3/phi moles of CO2 and 4/phi moles of H2O will be produced if assume no dissociation.
As i understand with increase in phi the flame temperature will go down and so the equilibrium constant (Keq) increase leading to higher yield for H2. Similarly when phi is small but still rich (1.43) the flame temperature are large leading small Keq and hence larger yield for CO.
Follow the link for better understanding
http://www.wikiwand.com/en/Water-gas_shift_reaction
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