Alkaline absorbents for SO₂ and SO₃ removal: A comprehensive review

Injection of an alkaline absorbent into the flue gas can significantly reduce SO₂ and SO₃ emissions. The article presents alkaline absorbents employed in industrial processes to remove SO₂ and SO₃ from flue gases, detailing their characteristics and applications across various process conditions. It summarizes the mechanisms and influencing factors behind SO₂ and SO₃ removal, outlines the impact of multi-component gases, particularly SO₂, on SO₃ removal in actual flue gases, and elucidates this competitive phenomenon from a theoretical standpoint. The article compares the application scenarios and efficiencies of alkaline absorbents across different processes, identifies the optimal combinations of various absorbents and processes, and proposes a synergistic approach for the removal of SO₂ and SO₃. The findings demonstrate that by injecting calcium- or sodium-based absorbents into dry processes, SO₂ and SO₃ can be removed efficiently and cost-effectively, with process optimization and absorbent modifications further enhancing the SO_x removal efficiency. In the future, by blending two or more absorbents and applying them to dry processes, a synergistic removal of SO₂ and SO₃ can be achieved.