SO removal by submicron absorbents synthesized via inhibition method: The product layer grows like parallel peaks.

Injecting calcium hydroxide powder into the flue gas is an effective strategy for SO removal. However, commercial calcium hydroxide has several disadvantages, including large particle size, low efficiency, and unsuitability for excessive grinding. In this work, sub-micron calcium hydroxide was synthesized by an inhibition method and its performance for SO removal from flue gas was investigated on a pilot-scale platform (120 Nm/h). When the concentration of sodium alginate solution was 100 mg/L, the average particle size of calcium hydroxide decreased from 13.66 µm to 0.84 µm, which improved the SO removal (92.1 %) and conversion of the absorbent. The results of the fixed-bed experiments indicate that the absorption kinetics of the reaction is consistent with the Bangham model. In addition, density functional theory verifies that calcium hydroxide captures SO by chemisorption. The AFM image shows that the calcium sulfate whiskers produced during the reaction grow like parallel peaks on the adsorbent surface. The calculations suggest that the driving force for SO adsorption originates from Ca-p orbital (Ca(OH)) and O-s orbital (SO) hybridization. This study complements the island growth mechanism for gas-solid two-phase reactions and provides an effective method for removing SO from flue gas in coal-fired power plants. In addition, it will provide an important reference for the development of submicron adsorbents.