CaO/Ca(OH)2 thermochemical heat storage of carbide slag from calcium looping cycles for CO2 capture

Abstract

Carbide slag is an industrial waste generated from ethylene gas production in chlor-alkali plants. Here, a novel system coupling calcium looping and CaO/Ca(OH)2 thermochemical heat storage using carbide slag were proposed to simultaneously capture CO2 and store heat. For CaO/Ca(OH)2 thermochemical heat storage, the hydration/dehydration performance of original carbide slag and carbide slag that experienced calcium looping cycles for CO2 capture was investigated. The performances of the two types of carbide slag with and without chlorine were compared. The dehydration conversions of carbide slag improved with the increase of dehydration temperature. The chlorine content has no apparent effect on the hydration/dehydration performance of original carbide slag. However, for CO2 capture, carbide slag with high chlorine content shows lower carbonation conversion than that of carbide slag without chlorine. The hydration/dehydration conversions of carbide slag that experienced CO2 capture cycles are lower than those of original carbide slag. For carbide slag with chlorine, the hydration conversion can be improved by more than one CO2 capture cycle. Therefore, carbide slag that experienced various CO2 capture cycles is still suitable to be used in CaO/Ca(OH)2 thermochemical heat storage although calcium looping has an adverse effect on the hydration/dehydration performance of carbide slag.