Reaction Kinetics and Simulation Models for Novel High-Temperature Desulfurization Sorbents: Final Report.

摘要

A kinetic study of two mixed-metal oxide sorbents (zinc ferrite and zinc titanate) was conducted to obtain kinetic data at the temperatures and pressures typically encountered in coal gasifiers. These sorbents are used to remove H2S from the hot coal- derived gases and can be subsequently regenerated for use in a cyclical operation. The qualitative behavior of zinc titanate was found to be quite similar. Sulfidation kinetic rate increased with H2S concentration, slightly increased with temperature, increased with pressure at a constant H2S mol fraction with pressure at a constant H2S partial pressure, and increased with decreasing pellet diameter. The regeneration rates of both zinc ferrite and zinc titanate increased with temperature, O2 concentration, and pressure at a constant O2 mole fraction. The formation of zinc sulfate was found to be significant during regeneration of zinc ferrite at sufficiently low temperatures, high pressures, and high O2 concentrations. Reducing gas concentrations of 65-75% (H2 + CO) simulating the output from the Texaco gasifier operated in the oxygen-blown mode were used to assess the impact on sorbent performance. The shrinking core kinetic model was found to fit the experimental data very well. Correlations were made using a priori estimates of all parameters including diffusivity and mass transfer coefficients. Quantitative agreement was best obtained by treating the diffusivity term and/or the mass transfer term as best fit parameters. 22 refs., 69 figs., 18 tabs.