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 experiment ally the effects of pore structure on the performance of metal oxide s orbents during H2S removal from coal gas at high temperatures. Reactiv ity evolution (conversion vs time) experiments were carried out in a t hermogravimetric analysis apparatus using relatively broad ranges of p article size (53-350 mum), temperature (400-600-degrees-C), and H2S co ncentration (2500-10,500 ppm). The pore structure of fresh, heat-treat ed, and sulfided sorbents was analyzed by mercury porosimetry and nitr ogen adsorption using samples prepared in a fluidized or fixed-bed rea ctor under conditions similar to those used in the thermogravimetric a nalysis system. Strong effects of the pore structure of the sorbents o n their performance during desulfurization were revealed by our reacti vity and structure evolution data. The analysis of the experimental da ta showed that differences in the performance of sorbents of the same metal oxide can be explained on the basis of their different morpholog ical characteristics provided that an appropriate model for diffusion, reaction, and structure evolution in the interior of the reacting sor bent particles is employed.