Аннотация
This study investigates the feasibility of recovering ferroalloy from dust produced during the smelting of ferrosilicon manganese at the Taraz Metallurgical Plant LLP. Typically, the dust comprises (%wt.): MnO - 53.3; SiO 2 - 24.0; MgO - 5.4; CaO - 9.6; Al 2 O 3 - 3.8; Fe 2 O 3 - 1.5; ZnO - 1.8; PbO - 0.6. To determine the optimal process parameters, thermodynamic modelling was deployed using the HSC-5.1 software package to analyse results from a second-order rotatable experimental design (a Box-Hunter design). Dust was pelletised in a bowl granulator followed by electric smelting in combination with coke and steel chips in a single-electrode arc furnace with a power of up to 15 kV×A; the steel chips were added as a source of iron. The study shows that at equilibrium in the presence of iron, components of the dust reacted with carbon forming manganese silicides and FeSi at temperatures above 1300 º C and 1400 º C, respectively. By increasing the amount of carbon in the charge from 14 to 30% by weight of dust, the extraction of silicon and manganese into the alloy is increased to 44.7 and 92%, respectively, at a temperature of 1800 º C. The MnC22 and MnC25 grades of ferrosilicon manganese are obtained when the amount of carbon is equal to 20-30% by weight of dust, allowing 56.4-79.3% of Si and 67.7-84.3% of Mn to be extracted into the alloy over the temperature range of 1600-1800ºC. The time taken for electric smelting of the dust is reduced by 16-18% by increasing the amount of both carbon from 18 to 36% and steel chips from 2 to 6% which resulted in a corresponding increase in the extraction of Si and Mn into the alloy from 20.9 to 60% and 68.3-82.1%, respectively. Thermodynamic modelling of the system at equilibrium was deployed to determine the temperature effect on the distribution of silicon, manganese, zinc and lead in the "dust components - carbon - iron" system, the extraction efficiency of silicon, manganese and iron into ferroalloy, and the content of these metals in the alloy. The electric smelting produces grade MnC22 of ferrosilicon manganese from a combination of granular dust, 30% coke and 6% steel chips resulting in an alloy containing silicon and manganese at 20.5 and 65.8%, respectively.