Se Capture by a CaO-ZnO Composite Sorbent during the Combustion of Se-Rich Stone Coal

Selenium can be emitted to the environment during the combustion of Se-rich stone coal, both polluting the air and wasting a scarce resource of Se. In this work, the nanosized metal oxides ZnO, Al2O3, and Fe3O4 were combined with CaO to form composite materials. These were investigated as sorbents for the removal of Se from the flue gases generated by Se-rich stone coal combustion over the temperature range of 700-1000 degrees C during laboratory scale testing. It was found that these composite materials, especially those containing ZnO and Fe3O4, exhibited higher adsorption efficiency than pure CaO. The highest adsorption efficiency of 95.46% was obtained with the CaO-ZnO composite sorbent under optimized experimental conditions. FT-IR and X-ray diffraction results indicated that the adsorbed Se was predominantly in the form of CaSeO3, with a minor amount of ZnSeO3. Both the formation of ZnSeO3 and the enhanced reaction interface contribute to the higher adsorption of Se on the CaO-ZnO composite sorbent as compared with pure CaO. These newly developed CaO-ZnO composite materials show potential as sorbents for the capture and recovery of Se during industrial-scale Se-rich stone coal combustion.