Impact of load changes on the carbonator reactor of a 1.7 MWth calcium looping pilot plant

This work analyses the performance of a Calcium Looping (CaL) carbonator reactor that captures CO2 from a power plant operating under large load changes. Several experimental campaigns have been conducted in La Pereda 1.7 MWth CaL pilot plant where the carbonator inlet flue gas velocity varied between 2.0 and 5.3 m/s, leading to large changes in the particles entrainment rate and the solids inventory. These tests showed that CaL systems using circulating fluidized bed reactors are highly flexible. Modest gas velocities translate into high CO2 capture efficiencies because circulation rates equivalent to CaO/CO2 molar ratios similar to 10-12 can still be maintained, while carbonator solids inventories are relatively large. Under high carbonator gas velocities, a sorbent with high CO2 carrying capacity is necessary to guarantee high CO2 capture efficiencies. In these conditions, the recirculation of a fraction of the exiting particles towards the bottom of the carbonator proved to be useful for moderating the solids circulation rate between reactors, increasing the particles residence time in the carbonator and sustaining high CO2 capture efficiencies. For load increases, staging the flue gas entering the carbonator helped to sustain high CO2 capture efficiencies thanks to maintaining the solids inventory at the bottom of the reactor.