Compensation effect of ZnO desulfurization and SO_2 fixing by CaO at high temperatures is discussed. Experiments showed that both the H_2S removal and SO_2 fixing were first under surface reaction control before the eventual grain diffusion control. The thermal gravimetric data were obtained during change of reaction atmosphere or additive used for a series of samples and were well simulated by using equivalent grain model. There were linear relationships between logarithms of the pre-exponential factor lnk_0, lnD_0 and activation energies E_a, E_D, respectively. Furthermore, the compensation effect could be explained based on assumption of exponential energy distribution function over crystal surface and its inner as well. There existed different kinetic behavior when operating temperature was above or below the isokinetic temperature T_S. Above the isokinetic temperature T_S, the greater the activation energy, the higher activity the desulfurizer/SO_2 fixer had. It appeared that the grain diffusion of sulfur contained ion was very different from the molecule diffusion in pore.

Key words: DESULFURIZATION, ZINC OXIDE, HYDROGEN SULFIDE, SULFUR DIOXIDE, ACTIVATION ENERGY