Study of transient processes in a blast furnace based on the heat exchange scheme analysis

Abstract

A blast furnace is a complicated metallurgical facility, which is characterized by considerable delay and inertia in the flow of heat and mass exchange. Therefore, the analysis of transient processes based on modern ideas about heat transfer is an important issue in solving technological problems of blast furnace smelting managing. A two-stage heat transfer scheme along the height of a blast furnace of modern technology presented. When studying the thermal state of a blast furnace as a control object, it is advisable to divide it into two thermal zones - the upper zone and the lower zone. The border between the zones is located in the upper part of the mixed reduction region, between the start level of coke carbon gasification and the horizon below which iron oxides are directly reduced. It was shown, that the upper and lower thermal zones have fundamental differences in heat exchange conditions and are interconnected through the index of iron direct reduction degree. The transient processes of silicon variation in the hot metal studied at variation of iron ore load, natural gas flow rate, temperature and humidity of the hot blast, oxygen content in the hot blast and slag basicity. It was shown that the oscillatory transition process is observed in case, after applying the perturbation, it will have the opposite effect on the thermal conditions of the lower and the upper stages of heat exchange in the blast furnace. The iron ore load, hot blast humidity and slag basicity were found to be the most predictable input parameters affecting the concentration of silicon in hot metal. Change in oxygen concentration in hot blast and natural gas consumption have an alternating character of influence on thermal conditions of the blast-furnace hearth. At that, the characteristics of the transient processes of blast furnaces through various channels of action vary and depend significantly on the properties of the smelted raw materials, design and operational parameters of the furnaces