Feasibility analysis of ternary feed mixtures of methane with oxygen, steam, and carbon dioxide for the production of methanol synthesis gas

The feasibility of ternary feed mixtures of CH4 with O-2, H2O, and CO2 is analyzed in relation to the production of methanol syngas. Stoichiometric constraints are formulated in terms of three parameters characterizing the steam, partial oxidation, and carbon dioxide reforming reactions of methane. The equilibrium analysis is conducted using the methanol balance ratio mu and methane slip fraction chi as explicit design parameters. General results are derived for the feasibility of each ternary feed combination as a function of pressure and temperature in the range 1 < mu < 3 under carbon-free conditions. Numerical calculations indicate that CH4/O-2/CO2 feeds can be used in single-stage adiabatic reformers at low values of mu, but the produced syngas requires further treatment. Reforming based on CH4/O-2/H2O feeds is endothermic at mu greater than or equal to 2 under typical reaction conditions, thus requiring the application of a two-stage process involving primary and secondary reformers. Utilization of CH4/O-2/H2O feeds in single-stage adiabatic reactors is feasible for mu = 1.7-1.9, yielding syngas which can be upgraded by partial CO2 removal. The endothermic CH4/CO2/H2O feed combination is always feasible for 1 < mu < 3.