China's Refractories

Abstract: The pyrometallurgy combined with hydrometallurgy process is commonly used for recovering valuable elements from spent lithium-ion batteries. To improve the corrosion resistance of heat treatment furnace lining materials in this process, SiC-Si₃N₄-C composite refractories were prepared by heat-treating at 800-1 400 °C for 3 h, using fine particles of spent iron ladle bricks (1-0.5 and <0.5 mm), silicon carbide (2-1, 1-0.5, and <0.5 mm), silicon nitride (<0.045 mm), and graphite as raw materials. The fine particles of spent iron ladle bricks were used to replace silicon nitride with the same particle size. The effects of the spent iron ladle brick fine particles additions (0, 12.12%, 26.25%, 36.38% and 48.5%, by mass) and the heat treatment temperatures (800, 1 000, 1 200 and 1 400 °C) on the properties of the composite refractories were studied. The results show that: (1) with the <1 mm spent iron ladle brick fine particles addition increasing, the bulk density of the samples changes slightly, the apparent porosity gradually decreases, the cold modulus of rupture (CMOR) increases, and the cold compressive strength (CCS) first decreases, then increases and finally decreases slightly; (2) with the heat treatment temperature rising, the bulk density of the samples first increases and then decreases, the apparent porosity gradually decreases, and the CCS and the CMOR increase; (3) when the temperature is 1 400 °C and the spent iron ladle brick fine particles completely replace the silicon nitride fine particles with the same particle size, the sample exhibits the best comprehensive performance, with the bulk density of 2.37 g · cm^-3, apparent porosity of 14.3%, CCS of 31.6 MPa, and CMOR of 9.0 MPa, and it has a good resistance to the corrosion of crushed spent lithium-ion battery materials at 1 000 °C.

Key words: spent lithium-ion battery recycling, heat treatment, SiC-Si₃N₄-C, spent iron ladle bricks, corrosion resistance