Kinetics of isothermal reduction of carbon-containing silicomanganese dust

Abstract

Silicomanganese dust contains large amounts of valuables, such as Si and Mn, which can be used as raw materials for the smelting of silicomanganese. However, the direct addition of dust to the submerged arc furnace can influence the permeability of burden due to the fine particle size of dust, which results in incomplete reduction reactions during the smelting process. In this paper, silicomanganese dust, graphite powder, and other additives were pressed to form carbon-containing dust briquettes, and the self-reduction process of the dust briquettes was investigated through the isothermal thermogravimetric method with different carbon–oxygen (C/O) molar ratios, contents of fluxing agents, and reduction temperatures. Various reduction kinetic models for dust briquettes at different temperatures were established. The results show that the reaction fraction of the dust briquettes was about 90% at a C/O molar ratio of 1.2 with optimal reduction efficiency. The addition of CaF₂ contributed to the decrease in the melting point and viscosity of dust briquettes, which increased their reduction rate. As the reduction temperature increased, the reduction rate of dust briquettes increased. The reduction reaction rate of dust briquettes was controlled through gas-phase diffusion. Meanwhile, their reduction process was analyzed kinetically, with the reaction time of 5 min as the dividing line. The apparent activation energies for the two diffusion stages were 56.10 and 100.52 kJ/mol, respectively. The kinetic equations are expressed as [1 − (1 − f)^1/3]² = 0.69e^{−56100/(RT)}t and [1 − (1 − f)^1/3]² = 2.06e^{−100520/(RT)}t.

Keywords

silicomanganese dust / carbothermal reduction / isothermal reduction / kinetics

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