Sustainable production of ultrahigh-temperature thermal energy storage particles from molten steel slag

Steel slag (SS), a high-volume byproduct (150 kg/ton steel) with severe disposal burdens, poses critical environmental challenges. To transform this waste into value, we propose the novel TERSEG protocol–a sustainable valorization route that, for the first time, simultaneously enables ultrahigh-temperature thermal energy storage (TES) particle production from molten SS via centrifugal granulation and recovers its >1400 °C waste heat. By modifying molten SS with blast furnace slag (BFS) to drastically reduce its viscosity by ∼90% (to 0.23 Pa s at 1500 °C), we overcome prior barriers to granulation. The engineered particles (1-3 mm) exhibit exceptional thermal stability (<1% mass loss over 10 cycles at 400-1000 °C), good sphericity (axis ratio of 1.5), and low porosity (<4%), making them ideal TES materials. This approach recovers >1400 °C waste heat and converts hazardous slag into functional materials. The TES particle production scalability is demonstrated via an empirical correlation validated across broad operational conditions. This approach pioneers a sustainable valorization route that simultaneously recovers >1400 °C waste heat and converts hazardous slag into functional TES materials. This work provides a circular economy strategy for the steel industry, diverting slag from landfills, reducing industrial CO2 footprint, and advancing net-zero goals.