Thermodynamic Analysis and Kinetics Model of H2S Sorption Using Different Sorbents

摘要

Integrated gasification combined cycle (IGCC) power systems are being advanced worldwide for generating electricity from various fuels due to their high-energy efficiency, superior environmental performance, and low cost electricity in comparison to conventional power plants. Syngas produced from gasification process, primarily consists of CO, CO2, CH4, and H2, with certain content of contaminants, like sulfur compounds. These need to be removed prior to the utilization to avoid detrimental effects on the system equipments. Hot gas desulfurization (HGD) can improve the thermal efficiencies and lower the capital costs of the IGCC system due to the elimination of fuel gas cooling and associated heat exchangers. For this reason, various sorbents have been extensively studied to remove both inorganic and organic sulfur-containing compounds in situ or downstream of gasifiers. To efficiently evaluate the performance of different sorbents and optimize the desulfurization process, a kinetic and thermodynamic analysis of the sorption reaction(s) for sulfur removal from hot gases is necessary. In this work, dolomite, limestone, lime, and several metal oxides, like CuO, ZnO, FeO, and MnO were chosen as desulfurization sorbent candidates. Three simulated gases based on gas compositions obtained from typical gasifiers were used for the thermodynamic analysis of sorption with various sorbents for H2S removal. The H2S concentration in equilibrium was calculated using the software package Factsage version 5.4.1 (GTT Technologies). The thermodynamic analysis shows that the equilibrium H2S concentration associated with the sulfidation of different sorbent is astrong function of temperature compared with other conditional parameters. Copper, zinc, and manganese oxides have the most favorable thermodynamic property of H2S removal when the temperature is lower than 650° C Compared with other sorbents, dolomite, limestone, and lime have fairly similar removal abilities and exhibit quite different sorption tendencies as a function of the temperature. Finally, different sulfidation models were presented and the kinetics of sulfidation with calcium-based sorbent by using the unreacted shrinking core model with variable effective diffusivity will be further examined and covered in the future publications.