Kinetic and Thermodynamic Study of the Wet Desulfurization Reaction of ZnO Sorbents at High Temperatures

Abstract

Hot gas conditioning is a remarkable stage for decreasing typical and harsh contaminants of syngas produced in the biomass gasification process. Downstream contaminants containing hydrogen sulphide (H2S) can significantly deteriorate fuel stream conversion reactors and fuel cell systems. Thus, an effective gas cleaning stage is required to remove critical streams that endanger the whole pathway toward the biomass conversion process. In this work, we studied H2S capture from biofuel syngas by using a kinetic deactivation model to analyze the effect of the operating conditions on the adsorption performance. Furthermore, the particle sorbent influence on other reactions, such as methane reforming and water gas shift (WGS), were also evaluated. Breakthrough curves were plotted and fitted following a first-order linearized deactivation model to perform both the H2S adsorption capacity and thermodynamic analysis. Moreover, the influence of the operating conditions was studied through a breakthrough curve simulation. By using the Arrhenius and Eyring–Polanyi expressions, it was possible to calculate the activation energy and some thermodynamic parameters from the transition state theory. Finally, a mathematical analysis was performed to obtain the diffusion coefficient (D) and the kinetic reaction constant (k¯0) of H2S gas within ZnO particles, considering a spherical geometry.