Behavior of magnesium in the desulfurization process of molten iron with magnesium vapor produced in-situ by aluminothermic reduction of magnesium oxide

Abstract

The behavior of magnesium in the desulfurization process of molten iron with magnesium vapor produced in-situ by the aluminothermic reduction of magnesium oxide has been investigated. The magnesium concentration first increased rapidly, reaching the maximum, and then decreased gradually to a very low level. The magnesium concentration of the molten iron was mainly that of the dissolved magnesium and the following decrease in the magnesium concentration was due to the evaporation from the melt surface and the mass transfer of the dissolved magnesium to the bubble surface. Under the present experimental conditions, the magnesium concentration increased with increasing temperature, pellet mass, carrier gas flow rate and decreasing initial sulfur concentration. Decreasing the pellet mass and increasing initial sulfur concentration made the desulfurization efficiency higher and decreased the amounts of magnesium dissolving into the melt and leaving the melt. The equilibrium relation between [ppmMg] and [ppmS] did not conflict with the present experimental results at temperatures from 1 553 to 1 673 K. A mathematical model for analyzing the behavior of magnesium in the present desulfurization process has been developed. The calculated magnesium and sulfur concentrations are well consistent with the experimental results. The calculated results demonstrate that the existence of the peak of magnesium concentration is reasonable. The present mathematical model can also explain the effects of pellet mass and initial sulfur concentration on the behavior of magnesium injected into the melt.