CaO/Ca(OH)2 heat storage performance of hollow nanostructured CaO-based material from Ca-looping cycles for CO2 capture

Abstract

A hollow nanostructured CaO-based material fabricated from calcined limestone and glucose by hydrothermal carbonization method was proposed to be used in the process coupled Ca-looping for CO2 capture and CaO/Ca(OH)2 heat storage. The effects of hydrothermal temperature and interval in the preparation process on CO2 capture and heat storage capacities of the hollow CaO were studied. The interaction effect of Ca-looping and heat storage on the performance of the hollow CaO was determined. The hollow nanostructure of CaO decreases the diffusion resistance of CO2 and steam in its inner. The CO2 capture capacity of the hollow CaO reaches 0.45 g/g after 20 Ca-looping cycles, which is 1.7 times as high as that of limestone. The hollow CaO (hydrothermal temperature of 170 °C for 6 h) after 10 Ca-looping cycles achieves a heat storage capacity of 0.85 mol/mol during the subsequent heat storage cycles, which is 1.3 times as high as that of limestone. A few heat storage cycles improve pore structure of the sintered hollow CaO after Ca-looping cycles, so its CO2 capture capacity in the following Ca-looping cycle is enhanced by 94%. Thus, the hollow nanostructured CaO seems promising in the process coupled Ca-looping and CaO/Ca(OH)2 heat storage.