Evaluation of a Spray-Dried CuO/MgAl2O4 Oxygen Carrier for the Chemical Looping with Oxygen Uncoupling Process

Abstract

The chemical looping with oxygen uncoupling (CLOU) process is a chemical looping combustion (CLC) technology that allows for the combustion of solid fuels with inherent CO2 separation. As in CLC technology, in the CLOU process, the oxygen necessary for fuel combustion is supplied by a solid oxygen carrier, which is moving between two reactors: the fuel and air reactors. The CLOU technology uses the property of some metal oxides (CuO, Mn2O3, and Co3O4), 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. In this work, a material prepared by spray drying containing 60 wt % CuO and 40 wt % MgAl2O4 as supporting material was evaluated as an oxygen carrier for the CLOU process using different installations. First, the oxygen release rate and the fluidization behavior, with regard to the agglomeration and attrition rate, were analyzed in a thermogravimetric analyzer (TGA) and in a batch fluidized bed, respectively. Then, the effects of the main operating conditions, such as the temperature, solids flow rate, and gas velocity in the fuel reactor, on the oxygen-carrier capability to release gaseous oxygen were analyzed in a continuous CLOU unit using N2 and CO2 as fluidization media. In addition, the effect of the oxygen concentration in the air reactor on the capability of the oxygen carrier to be regenerated was evaluated. The results obtained showed that this oxygen carrier has suitable characteristics for the CLOU process. Nevertheless, after 40 h of continuous operation at high temperatures, the particle integrity decreased significatively, indicating the need to improve the lifetime of this kind of material for use in an industrial CLOU process.