Chemical-Looping Combustion (CLC) is an emerging technology for CO

Chemical-Looping Combustion (CLC) is a combustion technology with CO 2 capture that is characterized by its low energy penalties because the CO 2 separation is inherent to the process. The CLC concept is based on the transfer of oxygen from the combustion air to fuel by means of an oxygen carrier (OC) in the form of a metal oxide. The OC circulates

a b s t r a c tChemical-looping combustion (CLC) is a combustion technology with inherent CO 2 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 1073 K are recommended.In this work, the behaviour of an impregnated Cu-based oxygen carrier (CuO-␥Al 2 O 3 ) was studied in a continuous CLC unit of 500 Wth during long-term tests using methane as fuel gas and FR temperatures up to 1173 K and AR temperatures up to 1223 K.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 T AR 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-␥Al 2 O 3 OC, 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.

a b s t r a c tChemical-Looping Combustion (CLC) is an emerging technology for CO 2 capture because separation of this gas from the other flue gas components is inherent to the process and thus no energy is expended for the separation. Natural or refinery gas can be used as gaseous fuels and they may contain different amounts of sulphur compounds, such as H 2 S and COS. This paper presents the combustion results obtained with a Cu-based oxygen carrier using mixtures of CH 4 and H 2 S as fuel. The influence of H 2 S concentration on the gas product distribution and combustion efficiency, sulphur splitting between the fuel reactor (FR) and the air reactor (AR), oxygen carrier deactivation and material agglomeration was investigated in a continuous CLC plant (500 W th ). The oxygen carrier to fuel ratio, , was the main operating parameter affecting the CLC system. Complete fuel combustion were reached at 1073 K working at values ≥1.5. The presence of H 2 S did not produce a decrease in the combustion efficiency even when working with a fuel containing 1300 vppm H 2 S. At these conditions, the great majority of the sulphur fed into the system was released in the gas outlet of the FR as SO 2 , affecting to the quality of the CO 2 produced. Formation of copper sulphide, Cu 2 S, and the subsequent reactivity loss was only detected working at low values of ≤ 1.5, although this fact did not produce any agglomeration problem in the fluidized beds. In addition, the oxygen carrier was fully regenerated in a H 2 S-free environment. It can be concluded that Cu-based oxygen carriers are adequate materials to be used in a CLC process using fuels containing H 2 S although quality of the CO 2 produced is affected.

Waste management generated from a Chemical-Looping Combustion (CLC) plant using copper based materials is analyzed by two ways: the recovery and recycling of the used material and the disposal of the waste. A copper recovery process coupled to the CLC plant is proposed to avoid the loss of active material generated by elutriation from the system. Solid residues obtained from a 10 kWth CLC prototype operated during 100 hours with a CuO-Al 2 O 3 oxygen carrier prepared by impregnation were used as raw material in the recovery process. Recovering efficiencies of 80 % were obtained in the process, where the final products were an eluate of Cu(NO 3 ) 2 and a solid. The eluate was used for the preparation of new oxygen carriers by impregnation, which exhibited high reactivity for reduction and oxidation reactions as well as adequate physical and chemical properties to be used in a CLC plant. The proposed recovery process highly decreases the amount of natural resources (Cu and Al 2 O 3 ) employed in a CLC power plant as well as the waste generated in the process. To determine the stability of the different solid streams during deposition in a landfill, these were characterized with respect to their leaching behavior according to the European Union normative. The solid residue finally obtained in the CLC plant coupled to the recovery process (composed by Al 2 O 3 and CuAl 2 O 4 ) can be classified as a stable non-reactive hazardous waste acceptable at landfills for non-hazardous wastes.