Demonstration of chemical-looping with oxygen uncoupling (CLOU) process in a 1.5 kWth continuously operating unit using a Cu-based oxygen-carrier

Abstract

Chemical-looping with oxygen uncoupling (CLOU) process is a chemical-looping combustion (CLC) technology that allows the combustion of solid fuels with inherent CO2 separation. As in the CLC technology, in the CLOU process the oxygen necessary for the fuel combustion is supplied by a solid oxygen-carrier, which contains a metal oxide. The CLOU technology uses the property of the copper oxide which can generate gaseous oxygen at high temperatures. The oxygen generated by the oxygen-carrier reacts directly with the solid fuel, which is mixed with the oxygen-carrier in the fuel-reactor. The reduced oxygen-carrier is transported to the air-reactor where it is oxidized by air. The flue gases from the fuel-reactor are only CO2 and H2O, since fuel is not mixed with air. This work demonstrates the proof of the concept of the CLOU technology burning coal in a 1.5kWth continuously operated unit consisting of two interconnected fluidized-bed reactors. A bituminous coal was used as fuel. An oxygen-carrier prepared by spray drying containing 60wt.% CuO and MgAl2O4 as supporting material was used as oxygen-carrier. The effects of fuel-reactor temperature, coal feeding rate, and solids circulation flow rate on the combustion and on the CO2 capture efficiencies were investigated. Fast reaction rates of oxygen generation were observed with the oxygen-carrier and full combustion of coal was attained in the plant using a solids inventory≈235kg/MWth in the fuel-reactor. In addition, values close to 100% in carbon capture efficiency were obtained at 960°C. Results obtained are analyzed and discussed in order to be useful for the scale-up of a CLOU process fuelled with coal.