Activated Semi-coke in SO₂ Removal from Flue Gas: Selection of Activation Methodology and Desulfurization Mechanism Study

Activated semi-coke, an economical carbonaceous material, is employed in the removal of SO₂ from simulated flue gas of an industrial power plant. Activation by four commonly used agents, including CO₂, KOH, ZnCl₂, and H₃PO₄, is studied in detail, which demonstrates that the sample treated with KOH at high temperature presents the best performance on removal of SO₂. Further investigation on the physical and chemical properties reveals that both optimized pore structure and increased amount of active sites of activated semi-coke could contribute to the high desulfurization capacity. The semi-coke activated with KOH is selected to discuss possible mechanisms of the adsorption and desorption processes. Performances with variation of desulfurization temperatures evidence that physically adsorbed SO₂ can transform into chemically adsorbed SO₂, which is significantly affected by temperature. Desulfurization behaviors under different flue gas compositions show that oxidation of SO₂ to SO₃ plays a key role in SO₂ removal. By the analyzing desorption behavior of the samples, a reactive intermediate, C­(O) complex, is proposed to be generated by dissociated chemisorption of O₂ onto the surface of activated semi-coke, which serves as the dominating active site in oxidation of SO₂. Besides, activated semi-coke exhibits several favorable properties in this study that could offer the prospect for further application in industrial desulfurization