Thermodynamic equilibrium analysis of combined carbon dioxide reforming with steam reforming of methane to synthesis gas

Thermodynamics equilibrium analysis of carbon dioxide reforming of methane combined with steam reforming to synthesis gas was studied by Gibbs free energy minimization method to understand the effects of process variables such as temperature, pressure and inlet CH4/H2O/CO2 ratios on product distributions. For this purpose, the calculations were carried out at total pressures of 1 and 20 bar, and at ranges of temperature and steam-to-carbon ratios of 200–1200 °C and 0–0.50, respectively. The results revealed that carbon dioxide reforming of methane combined with steam reforming process was controlled by different reactions with regard to the operating temperature, pressure and varying feed compositions. The H2/CO product ratio could be modified by changing the relative concentration of steam and CO2 in the feed, temperature and pressure, depending on the downstream application.

Research highlights► Addition of steam-to dry reforming resulted in increase CH4 activity and H2/CO ratio. ► Methane, CO2 conversions and H2/CO ratios decreased with increasing pressure. ► Combined DR-SR process is controlled by different reactions for varying T, P and feed composition. ► Product composition can be modified by varying H2O/CO2 ratio in the feed, T and P.