Using the Sol–Gel-Derived CuO/CuAl2O4 Oxygen Carrier in Chemical Looping with Oxygen Uncoupling for Three Typical Coals

Chemical looping with oxygen uncoupling (CLOU) without the coal gasification that limits the efficiency in ordinary chemical looping combustion (CLC) is a very promising approach for CO2 capture in the combustion of solid fuels. In the present work, the sol–gel-derived CuO/CuAl2O4 oxygen carrier was evaluated in terms of its ability to release gaseous oxygen in an oxygen-deficient atmosphere and its reactivity with coal in a laboratory-scaled fluidized-bed reactor at 850, 885, 900, 925, and 950 °C. Three typical Chinese coals of different coal ranks, GP coal (anthracite), FG coal (bituminous), and SL coal (lignite), were used as fuels in the CLOU experiments. The effects of the fuel-reactor temperature and coal rank on the carbon conversion rate, combustion efficiency, and CO2 yield were investigated. Nearly complete conversion of coals was attained. The conversion from carbon to CO2 can be enhanced if the temperature increases. Meanwhile, the combustion efficiency would be reduced because of the loss of partially unconverted products, such as H2 and CO, in the reduction process at a higher temperature. Experimental results also suggest that a higher reaction rate but lower combustion efficiency can be attained when the coal of a lower rank is used.