A mechanistic investigation of a calcium-based oxygen carrier for chemical looping combustion

Chemical looping combustion (CLC) has been suggested as an energy-efficient method for the capture of carbon dioxide from combustion. It is indirect combustion by the use of an oxygen carrier, which can be used for CO2 capture in power-generating processes. The possibility of CLC using a calcium-based oxygen carrier is investigated in this paper. In the air reactor air is supplied to oxidize CaS to CaSO4, where oxygen is transferred from air to the oxygen carrier; the reduction of CaSO4 to CaS takes place in the fuel reactor. The exit gas from the fuel reactor is CO2 and H2O. After condensation of water, almost pure CO2 could be obtained. The thermodynamic and kinetic problem of the reduction reactions of CaSO4 with CO and H2 and the oxidization reactions of CaS with O2 is discussed in the paper to investigate the technique possibility. To prevent SO2 release from the process of chemical looping combustion using a calcium-based oxygen carrier, thermochemical CaSO4 reduction and CaS oxidation are discussed. Thermal simulation experiments are carried out using a thermogravimetric analyzer (TGA). The properties of the products are characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray diffractometry (XRD), and the optimal reaction parameters are evaluated. The effects of reaction temperature, reductive gas mixture, and oxygen partial pressure on the composition of flue gas are discussed. The suitable temperature of the air reactor is between 1050 and 1150 °C and the optimal temperature of the fuel reactor between 900 and 950 °C.