Sulfidation performance of MgO-modified calcium-based waste from calcium looping: Experimental and density functional theory study.

In this work, cycled MgO-modified calcium-based waste from calcium looping was used for H 2 S removal. The H 2 S removal performance of MgO-modified carbide slag from calcium looping was examined. The effect mechanism of MgO addition on H 2 S removal by CaO was analyzed using density functional theory calculation. MgO-modified carbide slag from calcium looping possesses the enhanced H 2 S removal performance. The sulfidation temperature as well as H 2 S concentration have large impacts on the sulfidation performance of cycled MgO-modified carbide slag, while experienced multiple calcium looping cycles has slight effect. The sulfidation conversion of MgO-modified carbide slag after 10 calcium looping cycles under the severe and mild calcination conditions are 0.82 and 0.96 mol/mol, respectively. MgO-modified carbide slag from calcium looping keeps the more porous microstructure because MgO mitigates the sintering of CaO. The theoretical calculation results show that the adsorption and dissociation of H 2 S on CaO (0 0 1) surface are promoted by MgO. The sintering resistance and sulfidation activity of CaO are enhanced by MgO addition, contributing to the excellent H 2 S removal by cycled MgO-modified carbide slag from calcium looping. Therefore, cycled MgO-modified carbide slag from calcium looping seems prospective to be used for H 2 S removal. [Display omitted] • MgO-modified carbide slag from calcium looping cycles is proposed for H 2 S removal. • Cycled MgO-modified carbide slag exhibits enhanced sulfidation performance. • MgO addition mitigates growth of CaO grains and pore plugging of carbide slag. • Effect mechanism of MgO on H 2 S removal by CaO is revealed by DFT calculation. • H 2 S adsorption and dissociation on CaO surface are promoted by MgO addition. [ABSTRACT FROM AUTHOR]