Analysis of the Slag Mode of Blast Furnace Melting Using Model Decision Support Systems

Abstract

Abstract: The paper presents a balance model of the blast-furnace process improved by the researchers from the Ural Federal University and Magnitogorsk Iron and Steel Works. It generally represents a system of deterministic dependencies characterizing the thermal, reduction, gas dynamics, blast, and slag modes of blast-furnace melting. The basic principle underlying the model is full-scale mathematical modeling. Indicators characterizing the process of the final slag for implementation of the normal slag mode of blast-furnace melting (the slag viscosity at temperatures ranging from 1350 to 1550°C, as well as the values of slag viscosity gradients) were proposed. The slag viscosity gradient along with the acceptable ranges of slag viscosity at different slag temperatures are used in modeling the slag mode as the limiting factors for the diagnosis of slag mode. Selection of the limit values of each of the ranges and the viscosity gradient is carried out by the expert evaluation method. The structure of the model for calculating the parameters of the final slag is considered. Using a mathematical model of the blast-furnace process, the analysis of the slag mode of blast-furnace melting was performed according to the actual indicators of their operation. It was established that desulfurizing ability of the slag is insufficiently used; as a result, the smelted cast iron has a down-graded quality in terms of both the sulfur and silicon content. Due to the changes in the slag mode characteristics, other conditions being equal, it is possible to get a positive effect on the gas permeability in the slag formation zone; the gas reducing ability and productivity of the blast furnace increase; the coke consumption decreases. The authors present the results of design calculations of the performance indicators of the furnaces of the Magnitogorsk Iron and Steel Works when changing the composition of loaded materials. Recommendations on the slag optimal basicity are given. Calculations showed that the optimal values of basicity of the final slag, which ensure its maximum liquid mobility, for the operating conditions of blast furnaces of the Magnitogorsk Iron and Steel Works are 1.04–1.05 for the CaO/SiO2 ratio and 1.30–1.32 for the (CaO + MgO)/SiO2 ratio. © 2022, Allerton Press, Inc.