Regenerable mixed metal oxide sorbents are the prime candidates for the removal of hydrogen sulfide (the main pollutant) from the hot coal gas in the simplified integrated gasification combined cycle (IGCC) processes. As part of the sulfur removal process development, Carbona Corp. is developing fluidized bed reactor models for scale-up. It is essential for this work to apply a reliable and simple correlation for the conversion rate of zinc titanate or hydrogen sulfide in the sulfidation reaction. Two different models, the unreacted shrinking core (USC) model and overlapping grain (OG) model, are applied to this purpose. The parameter values obtained from ambient pressure tests are compared with those reported earlier for zinc titanates. Potential reasons for the differences are discussed. In the modeling of high-pressure sulfidation data, reaction rate constants from the literature are used, thus leaving the product layer diffusion coefficient as a fitting parameter. The values obtained indicate a linear dependence on process pressure.