Removal of H2S by spray-calcined calcium acetate

The effectiveness of wet-spraying calcium acetate as an alternative to lime stone and dolomite for the desulfurization of flue gases (in particular, H2 S removal from coal gas) has been investigated by experimental studies usin g drop tube (DTR) and fixed-bed flow reactors (FBR). Calcium acetate soluti on was spray-calcined in the DTR at temperatures of 1073 and 1323 K. At the lower temperature, conversions approaching 80% were found at the longest r esidence time studied, 0.8 s. On the other hand, the higher temperature con dition initially showed a much greater rate of calcination, indicated by gr eater conversion at shorter residence times, but was then followed by a muc h slower rate beyond 0.4 s. The final degree of conversion was in the regio n of 70%. Batches of spray-calcined calcium acetate (SCA), limestone, and d olomite, prepared in the DTR at 1323 K, to 70% conversion, were sulfided in the FBR at temperatures of 873 and 1173 K to assess their relative sulfur capture reactivities. Significantly higher conversions were achieved by the spray-calcined material, especially at the higher FBR temperature (1173 K) where a difference in conversion of more than 40% was observed. The physic al structure of the particles formed from wet-spray calcination were determ ined by electron microscopy and showed highly porous cenospheres with large internal voids and an outside surface characterized by "blowholes" of betw een 1 and 10 mu m in diameter. As a consequence, the available surface area for reaction with H2S is greater than with limestone or dolomite, producin g a 4-fold difference in the level of particle conversion.