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The exothermic reduction of CuO to Cu using a fuel gas as a source of heat to carry out the simultaneous calcination of CaCO 3 in a fixed bed has been evaluated. A dynamic pseudohomogeneous model has been developed to describe in detail the transient behavior of this operation. The experimental tests have been performed in a lab scale packed-bed reactor (i.d. × L = 38 mm × 920 mm) containing a mixture of CaO-and CuO-based particles (with 12 and 60 wt % of active phase, respectively). Preliminary heat-transfer studies have been carried out using inert gases at different temperatures to estimate the overall heat transfer coefficient of the system. An overall heat transfer coefficient of around 5 W/m 2 K has been obtained, which is a sufficiently low value to claim an operation close to adiabatic conditions. Hydrogen has been chosen as reducing gas. A Cu/ Ca molar ratio of 1.8 in the bed allows both the reduction and calcination fronts to advance together, with moderate maximum temperatures of around 870 °C, leaving behind totally converted solids. The effect of the solids temperature on the operation has also been evaluated. A rapid and complete reduction of CuO with H 2 has been achieved, even with starting temperatures slightly higher than 400 °C. However, the calcination of CaCO 3 was complete only in those zones of the bed where the temperature profile reached 870 °C.

A process scheme based on a series of fixed-bed reactors is presented as a possible alternative for carrying out the chemical looping combustion of methane at high pressure with ilmenite as oxygen carrier. The oxygen carrier is stationary and it is alternately exposed to reducing and oxidizing atmospheres by means of the periodic switching of the gas feeds (i.e., methane and air, respectively). Cyclones and filters for the separation of gases and solids are not needed in fixed-beds, which allows a more compact reactor design. Moreover, the operation at high pressure permits the use of highly efficient power cycles. However, more complex heat management strategies and switching valves able to function at very high temperatures are required in these systems. The continuous cyclic operation of a packed-bed chemical looping combustion process is described using a basic reactor model. A sequence of four stages: reduction, steam reforming, oxidation and heat removal ensures the production of a continuous high temperature and high pressure gas stream able to efficiently drive a gas turbine for power generation in combination with a steam cycle. At the same time, a concentrated stream of CO 2 suitable for transport and storage is also produced. The use of suitable recycles of the product gases makes it possible to control the progression of the reaction and the heat exchange fronts, which improves the heat management of the CLC process.The inclusion of steam methane reforming in the process allows the conversion of the ingoing methane to syngas, which enhances the reduction kinetics of the ilmenite and the overall combustion efficiency of the process. A preliminary design for an inlet flow of 10 kg/s of methane (500 MWt) has shown that a minimum of five reactors, 10 m long, with an inner diameter of 6.7 m, would be required to fulfil the overall process assuming cycles of 10 minutes with maximum pressure drops per stage of less than 6 %.These results demonstrate the potential of this novel technology for power generation in combination with CO 2 capture.

The Ca-Cu looping process allows a H 2-rich product gas to be obtained on the basis of the sorption enhanced reforming (SER) concept, while generating a concentrated stream of CO 2 suitable for geological storage or industrial use. Previous works have demonstrated that the Cu/CuO chemical loop provides a feasible alternative for regenerating the CO 2-sorbent required for the SER with potentially low energy penalties. In this work, the CuO reduction/CaCO 3 calcination operation, which is the key stage of the Ca-Cu looping process, is experimentally demonstrated in a fixed-bed reactor at TRL4 using pure methane as fuel gas. The effect of the temperature of the solids bed on the operation is also evaluated. A detailed characterization of both CuOand CaO-based materials resulting from the experiments has been carried out, revealing only minor changes in their textural properties, which demonstrates their high stability after successive oxidation-carbonation-reduction/calcination cycles.