Thermodynamic equilibrium analysis of water-gas shift reaction using syngases-effect of CO2 and H2S contents

Thermodynamic equilibrium of water-gas shift reaction (WGSR) under various temperatures, pressures and steam-to-CO (SIC) ratios was analyzed by Gibbs free energy minimization method. Coal-derived syngases with various CO2 and H2S contents were used as the feedstock. Based on the obtained results, it was found that CH4 and carbon formations were enhanced when syngas CO2 content increases. Carbon-free WGSR can be resulted using high SIC ratio. However, CH4-free WGSR cannot be resulted even with low SIC ratios. From the H2O conversion and H-2 yield variations, the temperature at which reverse WGSR occurs can be identified and found to decrease with the increase in SIC ratio. Solid CaO sorbent was employed for both CO2 and H2S removals in WGSR when sour syngas was used as the feedstock. It was found that WGSR performance was enhanced due to the CO2 and H2S removals by CaO. The H2S concentration can be decreased with decreased SIC ratio while increasing the reaction pressure was not favourable for H-2 production and H2S removal in WGSR with CaO. Because WGSR performance enhancement due to CO2 and H2S removals occurred at high temperature, catalysts can be eliminated in sorption-enhanced WGSR. (C) 2017 Elsevier Ltd. All rights reserved.