Dissociation Set

Chien

I have a problem. On the Star-CD, we always set chemical reaction or combustion formula in the "Local Source Model Definition". Today I want to build the dissociation phenomenon of natural gas combustion. But I can't set it successful. Because maybe I don't write right two-way reaction, which is CO + 0.5O2 <-> CO2. My setting is in the following... I entered the Reaction2, "CO +0.5O2 -> CO2", and "CO2 -> CO + 0.5O2" in the Reaction3. And then, in the Reaction4, "H2 + 0.5O2 -> H2O". In the Reaction5, "H2O -> H2 + 0.5O2". However, in the Reaction1, I enterd only "CH4 + 0.5O2 -> CO + 2H2". Errors appear in I/O prompt. This demonstrate that my set is wrong! How do I solve the problem?? And what is the right dissociation set??