Evaluation of the cycling performance of a sorbent for H2S removal and simulation of desulfurization-regeneration processes

High temperature gas desulfurization is an efficient and environmentally-friendly process for syngas purification. This paper investigated the cycling behaviors of iron oxide/red clay desulfurization sorbents within 12 desulfurization-regeneration cycles in a fixed-bed quartz reactor. The results showed that the sulfur capacities of the regenerated sorbents reduced to less than 50% with all the regeneration rates of the sorbents exceeded 70.15%. The surface and structural properties of the sorbents in the desulfurization-regeneration cycles were characterized by XRD, XPS, SEM, BET and elemental mapping analyses. According to XRD analyses, the particle size of the sorbents gradually increased with the number of desulfurization-regeneration cycles. These cycles reduced the surface area and blocked the pore structure, which have a contribution on the degenerated desulfurization performances of regenerated sorbents. The XPS and EDS spectra indicated the existence of the sulfur-containing compounds in the cycled sorbents, contributing to the lowered regeneration rate of the sorbents. The concentrations of iron and oxygen on the surface decreased over the repeated cycles, which are adverse to the adsorption of acidic H2S. A simulation model was created using COMSOL Multiphysics software to predict the performance and characteristics of the desulfurization-regeneration processes and elucidate its specific mechanism in the desulfurization and regeneration reactions. The comparison between predictions using COMSOL and experimental results were also conducted. Although there are deviations observed in the comparison, the simulated results match the experimental data to a large degree and show the feasibility of the COMSOL Multiphysics in the study of desulfurization and regeneration. (C) 2017 Elsevier B.V. All rights reserved.