Modeling and analysis of S-sorption with ZnO in a transport reactor

A mathematical model was developed to describe the sulfidation of zinc oxide sorbents in a transport reactor. The model incorporated both kinetic and hydrodynamic effects. A variable property grain model was applied to account for the kinetic reaction of hydrogen sulfide with zinc oxide. Grain radius was assumed to vary under the combined effect of sintering and extend of reaction. All model parameters were obtained from literature correlations or independent experimental measurements. The model predictions were validated against experimental data from a bench-scale transport reactor. Tests were conducted with 70μm ZnO particles in a nitrogen stream with 1% H2S at 2100 kPa and 811 K. The sorbent was recycled through the system to simulate 10 passes through the reactor. Significant improvement in the comparison with experimental results was achieved when compared to a constant property grain model. The model was also used to perform a sensitivity analysis on the effect of operating temperature, pressure, H2S concentration, and particle size on the hot gas desulfurization performance.