Carbide slag is modified by a dual-effect modification method into a thermochemical energy storage material

Abstract

Although calcium carbide slag is a kind of solid waste, but it is a promising raw material for preparing direct solar energy storage materials. In this study, we investigated the preparation of calcium carbide slag as an efficient solar energy storage material by a dual-effect modification method of doping inert metal compound stabilizers and pore-forming templating agents, and explored its performance in the CaO/CaCO3 thermochemical energy storage cycling system in a double-fixed-bed reactor. The results showed that the optimally formulated energy storage material CSMn10 (in which the molar ratio of Ca2+ to Mn2+ was 90:10) was analyzed by X-ray diffraction (XRD) and confirmed that its main component was CaO, and Mn2O3 and CaMnO3 were generated in it, and the presence of Mn2O3 and CaMnO3 not only inhibited the sintering of the calcium oxide grains in the cycling process but also enhanced the alkalinity of the material. They also enhance the alkalinity of the material and promote the generation of oxygen vacancies, which are all favorable to the carbonation reaction. After 20 cycles, the energy storage density of the material CSMn10 was 1508.23 kJ/kg; its average solar absorptivity was as high as 72.99%, which was 7.19 times higher than that of the unmodified calcium carbide slag (CS), and this phenomenon is mainly attributed to the introduction of manganese acetate, which greatly enhances the cycling stability and light absorbing ability of the material. In summary, the dual-effect calcium carbide slag modification method proposed in this study is not only simple and environmentally friendly, but also effectively utilizes industrial solid waste and provides a new method for the preparation of solar energy storage materials.