Effect of supports on the redox performance of pyrite cinder in chemical looping combustion

Chemical looping combustion (CLC) is a clean and efficient flame-free combustion technology, which combust the fuels by lattice oxygen from a solid oxygen carrier with inherent CO 2 capture. The development of oxygen carriers with low cost and high redox performance is crucial to the whole efficiency of CLC process. As the solid by-product from the sulfuric acid production, pyrite cinder presented excellent redox performance as an oxygen carrier in CLC process. The main components in pyrite cinder are Fe 2 O 3 , CaSO 4 , Al 2 O 3 and SiO 2 in which Fe 2 O 3 is the active component to provide lattice oxygen. In order to systematic investigate the functions of supports (CaSO 4 , Al 2 O 3 and SiO 2 ) in pyrite cinder, three oxygen carriers (Fe 2 O 3 -CaSO 4 , Fe 2 O 3 -Al 2 O 3 and Fe 2 O 3 -SiO 2 ) were prepared and evaluated in this study. The results showed that Fe 2 O 3 -CaSO 4 displayed high redox activity and cycling stability in the multiple redox cycles. However, both Fe 2 O 3 -Al 2 O 3 and Fe 2 O 3 -SiO 2 experienced serious deactivation during redox reactions. It indicated that the inert Fe-Si solid solution (Fe 2 SiO 4 ) was formed in the spent Fe 2 O 3 -SiO 2 sample, which decreased the oxygen carrying capacity of this sample. The XPS results showed that the oxygen species on the surface of Fe 2 O 3 -CaSO 4 could be fully recovered after the 20 redox cycles. It can be concluded that CaSO 4 is the key to the high redox activity and cycling stability of pyrite cinder.