Calcium looping, CaL, is rapidly developing as a postcombustion CO 2 capture technology because its similarity to existing power plants using circulating fluidized bed combustors, CFBC. In this work we present experimental results from a pilot built to demonstrate the concept at the MW th scale. The pilot plant treats 1/150 of the flue gases of an existing CFBC power plant ("la Pereda") and it has been operated in steady state for hundreds of hours of accumulated experimental time. The pilot includes two 15 m height interconnected circulating fluidized bed reactors: a CO 2 absorber (or carbonator of CaO) and a continuous CaCO 3 calciner operated as an oxy-fuel CFBC. Operating conditions in the reactors are resembling those expected in large CaL CO 2 capture systems in terms of reactor temperatures, gas velocities, solid compositions and circulation rates and reaction atmospheres. The evolution of CO 2 capture efficiencies, solid properties (CO 2 carrying capacity and CaO conversion to CaCO 3 and CaSO 4) have been studied as a function of key operating conditions. It is demonstrated that CO 2 capture efficiencies over 90% are feasible with a supply of active CaO slightly over the molar flow of CO 2 entering the carbonator. Closure of carbon and sulphur balances has been satisfactory during steady state periods. A basic reactor model developed from smaller test facilities seems to provide a reasonable interpretation of the observed trends. This should facilitate the further scale up of this new technology.

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