The comprehensive utilization of mass and heat of hot blast furnace slag and coordinated disposal of chromium-containing sludge to prepare glass-ceramic

Currently in steel enterprises, the mass and heat of hot blast furnace slag (BFS) are not fully recovered, and the produced chrome-containing sludge (CCS) poses a significant threat to the ecological environment. In this work, CCS together with other ingredients is added into hot BFS to produce high value-added glass-ceramic (GC), after the mixed molten slag is cooled down. The obtained GC shows excellent physical and chemical properties (bulk density: 2.76 g cm- 3, water absorption: 0.059%, compressive strength: 78 MPa, Vickers hardness: 7.54 GPa, acid resistance: 98.63 %, alkali resistance: 99.84 %, thermal conductivity: 1.049 W m- 1 degrees C- 1, and thermal expansivity: 6.56 x 10-6 m m- 1 degrees C- 1). These excellent physical and chemical properties render the as-prepared GC a high value-added building material. In addition, the leaching concentrations of total Cr element and Cr(VI) in the as-prepared GC are 1.6 mg L- 1 and 1.03 mg L-1, respectively, which are below the standard threshold for hazardous waste extraction toxicity. Compared with the traditional sintering method, the sensible heat of the hot BFS can be used as the thermal source in the molten slag cooling method, which can save a lot of energy. The use of hot BFS and CCS to produce high value-added GC not only fully utilizes the mass and heat of hot BFS but also fixes the Cr element in the CCS within the crystalline phase of GC, thereby eliminating the pollution of CCS to the environment.