SO₃ 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 SO₃ 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 SO₃ removal from flue gas was investigated on a pilot-scale platform (120 Nm³/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 SO₃ 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 SO₃ 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 SO₃ adsorption originates from Ca-p orbital (Ca(OH)₂) and O-s orbital (SO₃) hybridization. This study complements the island growth mechanism for gas-solid two-phase reactions and provides an effective method for removing SO₃ from flue gas in coal-fired power plants. In addition, it will provide an important reference for the development of submicron adsorbents.