CaO/H₂O Thermochemical Heat Storage Capacity of a CaO/CeO₂ Composite from CO₂ Capture Cycles

Abstract

In this work, a CaO/CeO2 composite was used in a process that coupled the calcium looping for CO2 capture and CaO/H2O thermochemical heat storage. A four fixed-bed reactor system was used to investigate the effects of cerium addition and calcination conditions of calcium looping on simultaneous CO2 capture and thermochemical heat storage capacity of the composite in the coupled process. The interaction effect of the coupled process on the CO2 capture and thermochemical heat storage capacity of the CaO/CeO2 composite was determined. The addition of CeO2 in the composite alleviates CaO sintering and promotes the diffusion of CO2 and steam in the coupled process. The composite with a CeO2 content of 10 wt % exhibits the highest simultaneous CO2 capture and heat storage capacities in the coupled process. The hydration conversion of the composite that experienced 10 calcium looping cycles and then 10 heat storage cycles is 0.87 mol/mol, which is 1.3 times as high as that of the limestone under the same conditions. The composite from calcium looping under the mild calcination condition possesses greater heat storage capacity than that under the severe calcination condition. The introduction of the heat storage cycles in the CO2 capture cycles apparently increases the CO2 capture capacity of the composite because of the improvement in the pore structure. When CO2 capture efficiency is 90%, the supply cost for the composite is lower, compared with that for limestone. The CaO/CeO2 composite seems promising in the process that coupled calcium looping and CaO/H2O heat storage.