Development of an electric arc furnace steel slag-based ceramic material for high temperature thermal energy storage applications

This paper details the development process of ceramics made out of 100% electric arc furnace (EAF) steel slag, to be used as a shaped homogenous thermal energy storage (TES) media in packed-bed thermocline systems for high-temperatures industrial waste heat recovery, concentrated solar power (CSP), and Carnot batteries applications, among others. The main objective of this study was to investigate the influence of different process parameters on the properties of the resulting ceramics. The samples have been characterized in terms of bulk density, apparent solid density, and water absorption to identify the best values for different process parameter. The best properties were obtained for samples prepared with heat-treated slag powders, pressed at 300 MPa and fired at 1300 °C for 8 h under a static air atmosphere. The optimal bulk density was 3.1 g/cm3, and the water absorption was 1.2%wt. The measured specific heat capacity was 1026, 1181 and 1216 J/(kg.K) at 200, 400 and 600 °C, respectively, while the thermal conductivity values were 1.53, 1.50 and 1.37 W/(m.K) at the same temperatures. This work confirms the feasibility of manufacturing TES ceramics out of EAF steel slags, using equipment and techniques well-known in the refractory industry.