Influence of the Properties of Blast Furnace Slag on Cast Iron Heating at Pulverized Coal Injection

In the course of the studies at two industrial blast furnaces, we established a change in the characteristics of slag mode and cast iron heating, resulting from the transition to the pulverized coal fuel injection with a decrease in basicity of CaO/SiO2 slag from 1.16 to 1.10 and from 1.20 to 1.12 units. It was shown that depending on a particular influence of alumina and magnesia in the slag composition, as well as on their ratio, a decrease in slag basicity can be accompanied by both an increase and a decrease in viscosity. During the research, the dependence between slag viscosity at the temperature of 1,400 °C and chemical heating of cast iron heating at the outlet was established. According to obtained data, an increase in slag viscosity by 0.1 Pа∙s was accompanied by an increase in silica concentration in cast iron by 0.08–0.1 %.The relation of physical heating of metal with slag basicity and stoichiometry was established. It was shown that a decrease in basicity of (CaO+MgO)/SiO2 by 0.1 units led to a decrease in cast iron temperature by 30 °C. Such a substantial effect of basicity of metal heating indicates the need to take this influence into account not only to control the blast furnace process, but also to state the thermal balance of steel smelting.It was shown that in the studied range of slag compositions, the influence of magnesia on heating of cast iron is limited. A slight influence of MgO on physical heating of metal was pronounced at a magnitude of the ratio Al2O3/MgO that is close to unity.Results of present research could be used to improve control over blast furnace smelting in terms of taking into consideration slag influence on heating of cast iron