Effects and mechanisms of fluorite on the co-reduction of blast furnace dust and seaside titanomagnetite

Abstract

The co-reduction roasting and grinding magnetic separation‒of seaside titanomagnetite and blast furnace dust was investigated with and without fluorite addition at a reduction roasting temperature of 1250°C for 60 min, a grinding fineness of −43 μm accounting for 69.02wt% of the total, and a low-intensity magnetic field strength of 151 kA/m. The mineral composition, microstructure, and state of the roasted products were analyzed, and the concentrations of CO and CO2 were analyzed in the co-reduction roasting. Better results were achieved with a small fluorite dosage (≤4wt%) in the process of co-reduction. In addition, F− was found to reduce the melting point and viscosity of the slag phase because of the high content of aluminate and silicate minerals in the blast furnace dust. The low moisture content of the blast furnace dust and calcic minerals inhibited the hydrolysis of CaF2 and the loss of F−. Compared with the blast furnace dust from Chengdeng, the blast furnace dusts from Jiugang and Jinxin inhibited the diffusion of F− when used as reducing agents, leading to weaker effects of fluorite.