Carbonation, Regeneration, and Cycle Stability of the Mechanically Activated Ca(OH)2 Sorbents for CO2 Capture: An In Situ X-ray Diffraction Study

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 SOx 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.

Combined removal of SO3 and HCl by modified Ca(OH)2 from coal-fired flue gas

As treatments for mainstream pollutants in coal-fired power plants have been established, the control of non-conventional pollutants, such as SO₃ and HCl, is gradually gaining attention. In this study, combined SO₃ and HCl removal is proposed based on SO₃ removal by absorber injection. However, it is challenging to selectively absorb SO₃ and HCl from SO₂-rich atmospheres. Therefore, Ca(OH)₂ was modified via ball milling and doping with CuO for the combined removal of SO₃ and HCl. The results showed that ball milling reduced the particle and grain sizes of Ca(OH)₂, which increased the active sites of Ca(OH)₂ and prolonged reaction time. After modification by ball milling, SO₃ absorption per mg of Ca(OH)₂ increased by 40 %. However, HCl removal efficiency was difficult to improve by modifying Ca(OH)₂ using only ball milling under SO₃ and SO₂ atmospheres. Therefore, the dechlorination capacity of Ca(OH)₂ was improved by adding ions during the ball milling process. Doping of Ca(OH)₂ with Cu²⁺ changed its crystal structure, weakened the diffusion resistance of HCl, and improved Ca(OH)₂ utilization. Additionally, it increased the energy of Ca(OH)₂ to adsorb HCl.