1.25b, d. Steady-state, one-dimensional, gas-phase flux calculation.
A flat plate of solid carbon is being burned in the presence of pure oxygen according to the reaction
Molecular diffusion of gaseous reactant and products takes place through a gas film adjacent to the carbon surface; the thickness of this film is 1.0 mm. On the outside of the film, the gas concentration is 40% CO, 20% O2, and 40% CO2. The reaction at the surface may be assumed to be instantaneous, therefore, next to the carbon surface, there is virtually no oxygen.The temperature of the gas film is 600 K, and the pressure is 1 bar. Estimate the rate of combustion of the carbon, in kg/m2-min.
Solution

CO (1), CO2 (2), O2 (3)
Calculate binary MS diffusivities from Wilke-Lee
Appendix C-2: Solution of the Maxwell-Stefan equations for a multicomponent mixture of ideal gases by orthogonal collocation (NC = 3).
Orthogonal collocation matrices
The pressure and temperature in the vapour phase are
The Maxwell-Stefan diffusion coefficicients are
The length of the diffusion path is
The density of the gas phase follows from the ideal gas law
Initial estimates of the fluxes
Initial estimates of the concentrations
Stoichiometric relations
(No oxygen)