Refractory monolithics as a containment of CaCl2–KCl–NaCl eutectic ternary chloride salt mixture for solar thermal storage

Solar thermal technologies are sustainable, relatively safer, and cost-effective renewable energy supplies. Theoretically, the efficiency of solar thermal power plants increases with increasing working temperatures. Solar thermal power plants hardly exceed the operating temperature of 500°C due to various limitations, such as the degradation of their components and linings (mainly alloys). In this paper, a recently proposed cost-effective high-temperature chloride salt mixture that can operate up to 750°C was tested against refractory monolithics (castables) as containment materials. Low-cement castables (LCC,a type of monolithic refractory) were designed to meet the desired chemical, physical, and mechanical properties. The interaction between the refractory monolithics and the energy storage materials (molten chloride salt mixture) was investigated using X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive X-ray spectroscopic analysis (SEM-EDS), and so on. The castables designed with mullite aggregates (M) have more impurities and thermal conductivity but lower porosity than hibonite aggregates (B). Negligible salt corrosion and minimal penetration were observed for both samples, but sample B did not show refractory contamination in salt.