REACTION BETWEEN H2S AND ZINC-OXIDE TITANIUM-OXIDE SORBENTS .2. SINGLE-PELLET SULFIDATION MODELING

In the temperature range of primary interest, 650-760 °C, the reaction between H2S and a desulfurization sorbent composed of 1.5 ZnO:1.0 TiO2(designation L-3140) can be described by a special case of the unreacted core model in which the global reaction rate is controlled by mass transfer and product layer diffusion resistances. Effective diffusivities through the product layer predicted by the random pore model show reasonable agreement with best-fit effective diffusivities determined by numerical methods. Although the magnitudes of the predicted and best-fit values differ, on average, by about 33%, the observed effects of temperature and pressure are consistent with random pore model predictions. Mass-transfer coefficients predicted by a modified Froessling equation differ from best-fit values by an average of only 15%. However, neither the effect of pressure nor the effect of temperature is adequately described. This is attributed to the fact that chemical reaction resistance is not truly negligible near the beginning of the reaction so that best-fit mass-transfer coefficients actually reflect both mass-transfer and reaction effects. © 1990, American Chemical Society. All rights reserved.