Equilibrium prediction of acid gas partial oxidation with presence of CH4 and CO2 for hydrogen production

Thermodynamic study of equilibrium condition for the partial oxidation of acid gas (AG consisted of 7.7%N2/61.7%H2S/20.1%CO2/9.3%H2O/1.2%CH4) was carried out using minimum Gibbs free energy strategy. The equilibrium calculation was fulfilled by Gibbs reactor model in the Aspen Plus software and sensitivity analysis about ER (Equivalent Ratio), addition ratio of CH4 and CO2 were conducted to investigate the favorable working condition for various parameters. Three cases that partial oxidation of the sole AG, AG/CH4 and AG/CH4/CO2 were studied. The results of the first case revealed that significant H2 and S2 yields and low SO2 selectivity were achieved at 1600 K with ER of about 4 under pure oxygen application. Extra CH4 addition conducts a negative effect on equilibrium temperature for a fixed ER compared to the former case and acts as oxidation inhibitor for H2S while promising H2 yield is attainable at high ER. Excess CO2 can be converted to valuable CO at the expense of H2 yield via reverse water-gas shift reaction. Its oxidation medium characteristic also propels oxidation of H2S and S2 to improve SO2 selectivity at high temperature.