EFFECTS OF PORE STRUCTURE ON THE PERFORMANCE OF COAL-GAS DESULFURIZATION SORBENTS

Two commercially available ZnO sorbents differing in porosity and pore size distribution were used as model solids to investigate experimentally the effects of pore structure on the performance of metal oxide sorbents during H2S removal from coal gas at high temperatures. Reactivity evolution (conversion vs time) experiments were carried out in a thermogravimetric analysis apparatus using relatively broad ranges of particle size (53-350 mum), temperature (400-600-degrees-C), and H2S concentration (2500-10,500 ppm). The pore structure of fresh, heat-treated, and sulfided sorbents was analyzed by mercury porosimetry and nitrogen adsorption using samples prepared in a fluidized or fixed-bed reactor under conditions similar to those used in the thermogravimetric analysis system. Strong effects of the pore structure of the sorbents on their performance during desulfurization were revealed by our reactivity and structure evolution data. The analysis of the experimental data showed that differences in the performance of sorbents of the same metal oxide can be explained on the basis of their different morphological characteristics provided that an appropriate model for diffusion, reaction, and structure evolution in the interior of the reacting sorbent particles is employed.