Recovery of CaO by Reductive Decomposition of Spent Gypsum in a CO−CO2−N2 Atmosphere

Reductive decomposition of spent CaSO 4 was studied using a packed-bed reactor to regenerate an alternative CaO sorbent. The reactor was operated at various process conditions including an increasing CO concentration, CO/CO 2 concentration ratio (0.067-1), and temperature (1123-1273 K). In all cases, N 2 was used as a balancing gas. The regeneration of CaO from CaSO 4 was found to be most effective in the CO-CO 2 -N 2 atmosphere and strongly depended on the CO/ CO 2 concentration ratio. At 1273 K, an apparent conversion value of 0.91 for the decomposition of CaSO 4 to CaO was obtained in a 2 vol % CO and 30 vol % CO 2 atmosphere. On the other hand, in a CO-N 2 atmosphere, CaS was predominantly produced. The SO 2 absorption capacity of CaO regenerated from CaSO 4 was higher than that of limestone-calcined CaO. A larger pore diameter of the regenerated CaO was considered to be responsible for the higher SO 2 absorptivity.