Melting and Crystallization Behaviors of Mold Flux with the Addition of Waste Electrolyte

Abstract

The influence of waste fluoride electrolyte addition on key properties of mold flux is investigated, with the aim to convert the hazardous waste in electrolytic aluminum industry into treasure in steel industry. The results show that the initial melting temperature of mold fluxes decreases from 1614.40 K (1341.40 °C) to 1564.67 K (1291.67 °C), and the complete melting temperature decreases from 1704.45 K (1431.45 °C) to 1674.34 K (1401.34 °C) with the addition of waste electrolyte from 10.08 to 24.89 wt%. The crystallization of mold flux is enhanced, and its crystallization mechanism transforms from “constant nucleation rate and 2D growth” into “constant nucleation number and 3D growth” with the addition of waste electrolyte. The main precipitated crystals in mold fluxes are grossular (Ca3Al2(SiO4)3) and CaF2, but the phase transforms into gehlenite (Ca2(Al(AlSi)O7) at higher temperature. In addition, the crystallization activation energy is 13.80, 12.40, 12.01, 11.03, and 10.27 kJ mol−1, respectively, which further confirms that the addition of waste electrolyte can reduce the energy barrier of crystallization and promote the crystallization ability of mold flux.