Effect of Pore Size Distribution of Calcium Oxide High-Temperature Desulfurization Sorbent on Its Sulfurization and Consecutive Oxidative Decomposition

CaS formed from the CaO sorbent during desulfurization in coal gasifiers must be converted to CaSO 4 before disposal. CaS is mainly decomposed to CaO and SO 2, and then the CaO is converted to CaSO 4 by SO 2 in the presence of H 2 O and O 2 . However, the inner portion of the CaS particles cannot be converted to CaO and CaSO 4, because the pores are plugged and oxidative gases (H 2 O and O 2 ) cannot come into contact with the interior of the CaS particles. In this study, the effect of the pore-size distribution of the CaO sorbent on the sulfurization and consecutive oxidative decomposition of the formed CaS in the presence of H 2 O at high temperature have been investigated, using three samples with different pore structures but similar surface areas. The following results have been obtained: (i) the macroporous CaS can be easily converted, because the oxidative decomposition of the macroporous CaS occurs without pore plugging; (ii) pores with a size of >100 nm in the sorbent can have an important role during the sulfurization and consecutive decomposition of the formed CaS; and (iii) the molar CaO/CaSO 4 ratio in the decomposed CaS sample is affected by the pore structure.