Effect of Sodium Bromide on CaO-Based Sorbents Derived from Three Kinds of Sources for CO2 Capture

The calcium looping (CaL), which applies carbonation/calcination cyclic reactions of a CaO sorbent, has received extensive attention for postcombustion CO2 capture. However, as the number of cyclic reactions increased, the capture efficiency of regenerated CaO decreased rapidly. Sodium doping was proposed for modification of a CaO sorbent, but there was little research on whether sodium doping had a good effect on different kinds of sorbents. In this paper, three different kinds of calcium-based sorbents, i.e., CaCO3, dolomite, and SG-CaO, were modified by NaBr to explore the effect of sodium on CO2 capture performance. The results showed that the modification effects of sodium on three kinds of precursors were different. For CaCO3, the modification effect of sodium doping was the best. After 50 cycles, the sorption capacity of CaO/NaBr was over 3.5 times that of an unmodified sorbent; for dolomite, sodium had a moderate effect during initial cycles and then showed obvious improvement in the stability of the sorbent, the sorption capacity of the modified dolomite increased by over 30% after 50 cycles; for the SG-CaO, sodium had a negative effect, the sorption capacity of the modified sorbent decreased by about 30% after 50 cycles. When the atmosphere contained SO2, the doping of an alkali metal also showed a certain effect.