Thermodynamic analysis of dry reforming of CH4 with CO2 at high pressures

Abstract

Thermodynamic equilibrium of dry reforming of methane (DRM) was studied by Gibbs free energy minimization at elevated pressures. CH4 and CO2 conversions, carbon formation, H2 yield, H2/CO ratio and H2O formation were used to characterize the DRM performance using the reaction temperature as the primary parameter. The result shows that DRM is unfavorable at high pressure. CO2 and CH4 conversions decrease while the carbon formation increases as the pressure increases. With increasing CO2/CH4 ratio in the reaction, CH4 conversion is enhanced, carbon formation is suppressed, but CO2 conversion is lower due to the excess CO2 supply. The simulation results indicated that the introduction of inert gas in the system did not produce a significant effect on DRM performance.The performances of combined DRM and partial oxidation of methane (POM) and combined DRM and methane-steam reforming (MSR) were also studied to suppress the carbon formation. It was found that carbon formation can be reduced by introducing oxygen. However, the resulted H2/CO ratio is less than 1. Introducing H2O into the reaction system can eliminate carbon formation when amount of H2O is large. However, the system must be operated at high temperature to produce high CH4 and CO2 conversions.