Investigation of attempts to improve cyclic CO2 capture by sorbent hydration and modification

A three-part experimental program was carried out to investigate possible methods to improve sorbent reversibility during cyclic calcination/carbonation using one limestone and one dolomite. In the first part, the different roles of steam and water are discussed and investigated. Steam addition during carbonation and calcination did not help to significantly achieve good reversibility. Hydration, especially with low-temperature steam and liquid water, is promising to help improve sorbent reversibility by regenerating favorable pore size distributions; however, a carbonate layer inhibited hydration. Preliminary tests were also conducted on possible agents that might improve CO2 capture efficiency and sorbent cyclic performance. An similar to 1: 1 molar ratio of CaO to Al2O3 showed promising results on a free-lime basis. A series of other tests did not give promising results, but provided information relevant to developing synthetic CO2 sorbents. It was also found that CO can regenerate CaO from CaSO4 formed during co-capture of SO2 and CO2, but the rate of reduction is too slow to be of practical interest.