Structurally improved CaO-based sorbent by organic acids for high temperature CO2 capture

Abstract

The acidification-decomposition process was used to enhance the performance of the natural limestone. A series of potential organic acids was employed to modify limestone to produce CaO-based sorbents for high temperature CO2 capture. The organic acids studied include formic acid, acetic acid, propionic acid, citric acid monohydrate, oxalic acid dihydrate, lactic acid, l-(−)-malic acid, and l-(+)-tartaric acid. Particularly, the latter three are novel acids used for the first time to modify limestone to obtain the CaO-based sorbents. The cyclic carbonation–calcination performance of the sorbents was investigated. All the sorbents, except the one modified by formic acid, exhibit the improved performance for capturing CO2. In particular, the novel sorbent modified by l-(+)-tartaric acid (S–T) shows the best cyclic performance with a high carbonation conversion of ∼36% at the 26th cycle, almost twice of that of unmodified sorbent. The superior performance of this sorbent was also found when tested under the simulated oxy–fuel atmosphere (realistic calcination atmosphere for post-combustion CO2 capture). It is believed that the improved structure by organic acid, which is in favor of mitigating the sintering and loss of specific surface area (SSA), has contributed to the superior performance of the sorbent.