Simultaneous CO2 capture and heat storage by a Ca/Mg-based composite in coupling calcium looping and CaO/Ca(OH)2 cycles using air as a heat transfer fluid

Abstract

The simultaneous CO₂ capture and heat storage performances of the Ca/Mg-based composite prepared from carbide slag and dolomite in a process coupling calcium looping and CaO/Ca(OH)₂ heat storage using air as a heat transfer fluid were investigated. In the coupling process, the spent CaO-based material experiencing multiple CO₂ capture cycles was employed in the CaO/Ca(OH)₂ heat storage process, and then the cycled material was again used to capture CO₂. When the mass ratio of CaO/MgO in the composite is 90 : 10, it exhibits the highest heat storage capacity of 0.53 mol mol⁻¹ and a heat storage density of 0.90 GJ t⁻¹ after 30 heat storage cycles. The adverse effect of CO₂ in air as the heat transfer fluid on CaO/Ca(OH)₂ heat storage capacity is overcome by the introduction of calcium looping cycles. By introducing a calcium looping cycle after the 10th and 20th heat storage cycles, the subsequent heat storage capacities of the composite are improved by 31% and 57%, respectively. The CO₂ capture reactivity of the composite is also promoted by the introduction of heat storage cycles. Therefore, the simultaneous efficient CO₂ capture and heat storage using the Ca/Mg-based composite is achieved in the process coupling calcium looping and CaO/Ca(OH)₂ cycles.