| Institution: | 1. State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China;2. Key Laboratory of Clean Chemical Engineering in Universities of Shandong, College of Chemical Engineering, Qingdao University of Science & Technology, Qingdao, 266042, China;1. School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China;2. Department of Chemical & Biochemical Engineering, Western University, London, Ontario, N6A 3K7, Canada;3. Institute of Shaoxing, Tianjin University, Zhejiang, 312300, China;1. College of New Energy, China University of Petroleum (East China), Qingdao, 266580, China;2. Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing, 100190, China;1. Department of Epidemiology and Environmental Health, School of Public and Health Professions, University at Buffalo, Buffalo, 14214, USA;2. Department of Earth Science and Geography, California State University, Dominguez Hills, Carson, 90747, USA;3. Department of Environmental Science, Baylor University, Waco, 76798, USA;1. State Key Laboratory of Separation Membranes and Membrane Processes, National Center for International Joint Research on Separation Membranes, Tiangong University, Tianjin, 300387, China;2. Tianjin Key Laboratory of Hollow Fiber Membrane Materials and Processes (Tiangong University), Tianjin, 300387, China;1. School of Environment and Safety Engineering, North University of China, Taiyuan, 030051, China;2. Shanxi Engineering Technology Research Center for Ultrafine Powder, North University of China, Taiyuan, 030051, China;3. School of Chemistry and Chemical Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China;4. Institute of Occupational Health of Ordnance Industry, Xi''an, 710065, China |
| Abstract: | Selenium pollution by coal utilization is of increasing concern. Calcium-iron (Ca–Fe) oxygen carriers (OCs) and alkali metal ions have strong inhibitory effects on selenium, which can reduce the emissions of selenium vapor. The retention mechanisms of selenium by Fe2O3, CaFe2O4, Ca2Fe2O5 and bottom ash are investigated during chemical looping gasification (CLG). Iron-based OC can oxidize H2Se(g) to SeO2(g); furthermore, lattice oxygen is released by Fe2O3, contributing to the formation of an Fe–O–Se structure to retain selenium and form selenite. Because calcium ferrite is poorly oxidizing, it cannot oxidize H2Se(g), but the CaO produced when OCs are reduced can react with H2Se(g) to form CaSe(s), and this process can be promoted by H2S(g). The best retention rates reached 32.301% when Ca2Fe2O5 was used. In the cyclic experiment, the selenium retention of the bottom ash gradually increases. Alkali metal ions in bottom ash are the main factor in retaining selenium. Ca2+ and Mg2+ do not easily vaporize due to their high melting points; therefore, their selenium retention is significantly better than that of K+ and Na+. This research provided a new idea for the removal of selenium by using OCs and bottom ash particles during CLG. |
