Study On Multi - Field Coupling Simulation And Silicon Smelting Reaction Process Of Industrial Silicon Smelting Furnace

The silicon production process is conducted in a submerged arc furnace (SAF), of which the experiment detection is difficult and the reaction structure complicated, whereas numerical simulation and thermodynamic calculation are the useful tools to study this process.In this paper, a 3D finite element model of an SAF used for silicon production was proposed to simulate the distributions of electromagnetic, flow and temperature field in the furnace. The effects of the specific resistance of furnace charge and the stand-off distance of plasma arc on physics fields in furnace were also investigated. And the results show that the skin effect and the proximity effect produced by three phase AC current cause heterogeneous distribution of current density within the electrodes, while the shape and position of the metal separators set among electrodes can change the influence of proximity effect; the maximum Joule heat power in the arc zone is 2.2 MW/m3, the maximum electromagnetic force, melt velocity, current density, magnetic field intensity in the molten pool is separately 1.308 N,0.497 m/s,91742.955 A/m2 and 20156.055 A/m, the maximum temperature and temperature gradient is respectively 2359.92℃ and 1680.42℃/m; the melt flow pattern is extremely complicated, within which there are swirl and mutual flow form, etc; with the increasing of charge resistance, the maximum magnetic field intensity in the molten pool become only 1.30% higher, but the maximum electromagnetic force and melt velocity is separately 4.01% and 10.26% lower; when the height of arc is increased, the maximum magnetic field intensity in the molten pool become only 1.43% lower, but the maximum electromagnetic force and melt velocity is separately 5.48% and 15.27% higher; feeding high resistance charge and pushing the electrode position down can be beneficial to enhancing the smelting temperature in furnace.HSC Chemistry thermodynamic software was utilized to study the reduction process of silica, whose results indicate that this process consists of four steps; considering the effects of kinetic factors, the author illustrated the reduction process of SiO2 with shrinking core model. On that basis, the ideal reaction structure in silicon smelting was assumed to consist of 6 reactions, among which, the mathematical reasoning indicates, there are and only 3 valid reactions. And the author derived that deposition molar quantity of SiC equals to the difference between the combustion loss of carbon and the exhaust loss of SiO with off-gas. Meanwhile, the author’s research achievements also imply that alkali salts or oxides and Fe-containing substances is feasible to restrain and dispose bottom rising in furnace.