Recent Advances in CaSO4 Oxygen Carrier for Chemical-Looping Combustion (CLC) Process

Chemical-looping combustion (CLC) is a novel combustion technology with inherent separation of the greenhouse gas CO2 and low NOx (NO, NO2, N2O) emissions. In CLC, the solid oxygen carrier supplies the stoichiometric oxygen needed for CO2 and water formation, resulting in a free nitrogen mixture. The performance of oxygen carrier is the key to CLC's application. A good oxygen carrier for CLC should readily react with the fuel (fuel reactor) and should be re-oxidized upon being contacted with oxygen (air reactor). In this case, the behavior of CaSO4 as an oxygen carrier for a CLC process, reacting with gas fuels (e. g., CO, H-2, and CH4) and solid fuels (e. g., coal and biomass), has been analyzed. The performance of the oxygen carrier can be improved by changing the preparation method or by making mixed oxides. Generally, Al2O3, SiO2, etc., which act a porous support providing a higher surface area for reaction, are used as the inert binder to increase the reactivity, durability, and fluidizability of the oxygen carrier particles. Further, simulation analysis of a CLC process based on CaSO4 oxygen carrier was also analyzed. Finally, some important tendencies related to CaSO4 oxygen carrier in CLC technology are put forward.