High temperature behaviour of a CuOh/γAl2O3 oxygen carrier for chemical-looping combustion

Chemical-looping combustion (CLC) is a combustion technology with inherent CO2 separation and, therefore, without energy losses. CLC is based on the transfer of oxygen from the air to the fuel by means of an oxygen carrier (OC) in the form of a metal oxide. The OC circulates between two interconnected reactors, the fuel (FR) and the air reactor (AR). To scale up the CLC process for industrial application OCs materials suitable to work at high temperatures are needed. So far, Cu-based OCs had been proved to fulfil the requirements for an OC material, although operating temperatures lower than 1073K are recommended. In this work, the behaviour of an impregnated Cu-based oxygen carrier (CuO-gamma Al2O3) was studied in a continuous CLC unit of 500 Wth during long-term tests using methane as fuel gas and FR temperatures up to 1173K and AR temperatures up to 1223K. The behaviour of the oxygen carrier on the process performance was evaluated taking into account important aspects such as combustion efficiency, resistance to attrition, fluidization behaviour and preservation of the oxygen transport capacity and reactivity. It was found that both T-FR and TAR had a great influence on the resistance to attrition of the particles. Stable operation for more than 60 h was only feasible at T-FR =1073 K and T-AR =1173 K. However agglomeration or deactivation of the particles was never detected in any of the temperatures used. This is the first time that a CuO-gamma Al2O3 DC, prepared by a commercial manufacturing method, and used at 1073 K in the FR and 1173 K in the AR exhibits such a good properties: high reactivity together with high mechanical durability and absence of agglomeration. This result opens new possibilities for the application of Cu-based materials in industrial-scale CLC processes. (C) 2011 Elsevier Ltd. All rights reserved.