Effect of Magnetic Field Intensity on Carbothermal Reduction Characteristics of Bayan Obo Iron Ore

The coal-based direct reduction process has been coupled with the magnetic field-enhanced reduction technique. The effects of the magnetic field intensity on reduction efficiency, phase changes of the iron-bearing minerals, and reduction kinetic behavior have been investigated. The results showed that the reduction efficiency of Bayan Obo iron ore increased with the increase of the magnetic field intensity and extending the reduction time. Under the conditions of magnetic field intensity, B = 1.0 T, reduction time t = 60 min, and reduction temperature T = 950°C, the metallization rate of Bayan Obo iron ore was 93.42%. The relationship between reduction efficiency and magnetic field intensity and reduction time was revealed by a response surface method. In all stages of reduction, the effect of magnetic field intensity on the reduction efficiency of Bayan Obo iron ore was greater than that of reduction time. The relationship between the three was: \({M}_{0\sim 60}\left(B,t\right)=- 17.31+2.35t+28.72B+0.6tB-0.02{t}^{2}-14.76{B}^{2}\) $M_{0\sim 60}\left(B,,,t\right)=-17.31+2.35t+28.72B+0.6tB-0.02t^2-14.76B^2$ . The magnetic field made the reaction material looser, which not only reduced the diffusion resistance of the reducing gas CO but also increased the adsorption potential of CO at the reaction interface. Compared with B = 0.0 T, for B = 1.0 T, the internal diffusion resistance and the interfacial chemical reaction rate were 5.08 times and 0.79 times higher, respectively.