Chemical-Looping with Oxygen Uncoupling of Different Coals Using Copper Ore as an Oxygen Carrier

Chemical-looping with oxygen uncoupling (CLOU) has been considered as a revolutionary technology for low-energy consumption CO2 capture. In this work, the performance of copper ore in the CLOU processes for diverse ranks of coal was examined in a batch-scale fluidized-bed at various temperatures. Typical Chinese coals (GaoPing anthracite, FuGu bituminous coal, and ShengLi lignite) were used as fuel. The effects of temperature and coal rank on the redox behavior, carbon conversion rate, and instantaneous rates of char conversion and oxygen generation were first investigated. It was found that both increasing the reactor temperature and decreasing the coal rank had beneficial effects on the carbon conversion rate, instantaneous rates of char conversion, and oxygen generation. In the CLOU processes of coal, the rate-limiting step was the burning of coal char with oxygen of low concentration if the oxygen carrier (OC) was excess to coal. And for higher-rank coals like anthracite, the rate-limitation effect was also greater. Then, two additional CLOU tests of anthracite were conducted to examine the accelerative effect of gasification agents. The results demonstrated that introducing the gasification agent (steam or CO2) into the fuel-reactor can increase the instantaneous char conversion rate of high-rank coal. Scanning electron microscopy-energy dispersive X-ray spectroscopy results showed that the porous structure of the used copper ore particles was partly blocked by the adhesion of fly ash. To be noted, all used copper ore particles presented a porous structure, and no serious agglomeration phenomenon was detected within the CLOU process, except for high-volatile lignite at 950 degrees C.