Calcium-based regenerable sorbents for high temperature H 2 S removal

Abstract

Abstract Ca–Al–O regenerable sorbents with various calcium contents have been prepared by co-precipitation method for H 2 S removal at 850 °C. For the sorbent with a calcium content of 52.5 wt%, its sulfur capacity reached 36 g S/100 g sorbent. The saturated S/Ca molar ratios of the sulfided sorbents changed from 0.82 to 0.88, depending on the Ca content of sorbent. They are much higher than the case of pure CaO. Regeneration by diluted air, a cyclic oxidation/reduction process, or water vapor was applied for the regeneration of sulfided sorbents. The sulfided sorbent cannot be regenerated completely in the diluted air regeneration operation. It was completely regenerated in the oxidation/reduction process, in which the oxidation used 3% O 2 and the reduction used 10% H 2 . Repeating the oxidation/reduction 4 times, CaS was completely converted to CaO. Under such regeneration conditions, the sorbent performance was stable during 5 sulfidation–regeneration cycles. Sintering was observed in high O 2 concentration regeneration due to the strong exothermic reaction, which resulted in activity drop. During 6 cycles of steam regeneration with 81% H 2 O at 850 °C, the sulfur capacities of the regenerated sorbents with an initial calcium content of 61.2 wt% remained stable at 36 g S/100 g sorbent.