Modelling of performance of zinc ferrites as high-temperature desulfurizing sorbents in a fixed-bed reactor

The performance of zinc ferrites as desulfurization sorbents at high temperature was evaluated. Sorbents were prepared by calcination, at 650 and 1100 degrees C, of mixtures of bulk oxides in three different stoichiometries. To calculate the global reaction rate of sulfidation in a thermogravimetric experiment, a grain model with variable properties was developed. The predicted and experimental results were in good agreement. Under the test conditions, the intrinsic reactivity and the diffusion of the reactant gas across the sulfide film on the particle were rate-limiting. These results were confirmed by SEM-EDX analysis of sulfur over a particle cross-section. The calculated global reaction rates of sulfidation were used in a simple model to predict the breakthrough curves at different space velocities in a fixed-bed reactor. The theoretical and experimental results were largely in agreement. (C) 1997 Elsevier Science Ltd.