Thermodynamic Equilibrium Analysis of Hydrogen Production Via Dry Reforming of Methane Process Using Gibbs Free Energy Minimization Method

In this paper, the thermodynamic equilibrium analysis of dry reforming of methane was performed by Aspen Plus software in order to increase the selectivity of hydrogen, elimination of carbon and adjust the H2/CO ratio. Equilibrium calculations were performed using Gibbs free energy minimization method. The effect of CO2/CH4 molar ratio (0-6), pressure (0.5-20 bar) and reaction temperature (300-1100 K) on equilibrium conversion rate, products selectivity and carbon formation were evaluated. The results showed that increasing the temperature and decreasing the molar ratio of CO2 / CH4 has positive effect on the rate of hydrogen selectivity, so that at the molar ratio of less than one CO2 / CH4 and temperature range above 1000 K, the rate of hydrogen selectivity reaches 100%. In contrast, with increasing pressure at constant temperature, the rate of hydrogen selectivity decreases, indicating the negative effect of the pressure on the rate of hydrogen selectivity. Carbon is the main by-product of dry reforming of methane, which must be removed in order to optimize operating conditions. At the ratio of CO2 / CH4 =1-6, with increasing the temperature and especially in the temperature range of 300-1000K, the amount of carbon formation decreases, but with increasing pressure, the amount of carbon production has an upward trend. On the other hand, with increasing the temperature, the conversion rate of carbon dioxide first decreases and then, with further increase in temperature, increases. In addition, the adjustment of H2/CO ratio of the syngas was performed for using in various processes, which can be achieved to the desired value by changing the CO2/CH4 ratio and pressure.