Carbonate looping experiments in a 1Â MWth pilot plant and model validation

Carbonate looping is an efficient post-combustion CO2 capture technology using limestone based sorbents. A carbonate looping pilot plant consisting of two interconnected circulating fluidized bed (CFB) reactors with a thermal capacity of 1 MWth has been designed and erected at Technische Universität Darmstadt. The pilot plant has been operated for >1500 h in fluidized bed mode, thereof >400 h with CO2 capture. The heat for the endothermic regeneration of CaO in the calciner was provided by combustion of either propane or pulverised coal with O2 enriched air. High CO2 absorption efficiencies of up to 85% in the carbonator were achieved for long periods. Taking the CO2 produced by oxyfuel-combustion in the calciner into account, the pilot plant was operated with total CO2 capture rates above 90%. A process model for the carbonate looping pilot plant has been developed with ASPEN PLUS™. A 1D CFB model has been implemented in the process model to determine the effect of hydrodynamics within a fast fluidized bed on the CO2 absorption rate in the carbonator. Operating conditions of a selected test campaign where used as boundary conditions. The results of process simulations show good agreement of calculated CO2 absorption rate with experimental data. Hence, this process model can be considered as a reliable tool for scale-up of the process.