Development of theoretical foundations for the hot metal desulfurization with magnesium reduced by the heat from exothermal transformations

Abstract

The process of hot metal desulfurization by magnesium, reduced by the heat from exothermic reactions, has been investigated. Our research into the thermodynamics of magnesium oxide reduction in line with various protocols has established that it is in principle possible to reduce magnesium oxide by carbon, silicon, manganese, iron, and aluminum. We have calculated starting temperatures for MgO reduction by iron, manganese, silicon, aluminum, and carbon, which are 2,956, 2,546, 2,313, 1,585 and 1,875 °C, respectively. It has been determined that the most rational method to reduce magnesium oxide is the process based on binding the products of reduction into a CaAl 2 O 4 compound. Based on the established rational conditions for magnesium oxide reduction, the exothermic mixture for hot metal desulfurization was calculated, %: MgO – 15.0; FeO – 56.0; CaO – 7.0; Al – 22.0. Experimental study has confirmed the most successful technical solution for the introduction of the calculated exothermic mixture to the melt aimed at desulfurization, which implies the application of a device for the introduction of active reagents into the melt, which is equipped with a chamber that collapses under the influence of the heat of liquid hot metal. Its use makes it possible to achieve the mean level of desulfurization of 65–70 %. We have performed, under industrial conditions, an experimental desulfurization of chromium hot metal using the designed exothermic mixture. According to the research conducted, the achieved degree of hot metal desulfurization in a ladle was at the level of 38 %; for the material of castings ‒ at the level of 45.7 %. Thus, there is a reason to argue about resource and energy savings when applying the proposed technology for the out-of-furnace hot metal desulfurization by reduced magnesium