Analysis of the Possible Ways to Reduce Sulfur Content in Pig Iron

Abstract

With an approach to improve the strength performance and rate of blast-furnace smelting, especially when pulverized coal fuel is involved, the improvement of the hot coke strength has been considered. A crude oil additive is introduced into the coal charge in PJSC Novolipetsk steel mill (NLMK) to improve the quality of coke. This brings about an increase in coke sulfur resulting in the sulfur content growth in pig iron. Therefore, the task of finding ways to improve pig iron desulfurization in the blast furnace becomes important. The following are key factors that affect the pig iron desulfurization rate: slag basicity, the content of MgO oxide in the slag, the temperature of smelting products, and the slag viscosity. The purpose of this work deals with comparing the desulfurization efficiency through the improvement of the slag basicity and increasing the MgO content. An algorithm is developed based on known equations in order to achieve this goal. The increase of MgO content in the slag provides better input into pig iron desulfurization than the increase in slag basicity. In addition, an increase in MgO content by 1% results in growing slag to pig iron ratio amounting to 3.0 to 3.5 kg/MT. At the same time, an increase in basicity by 0.01 leads to an increase in the slag to pig iron ratio 4 to 5 kg/MT. Consequently, reducing the sulfur content in pig iron by controlling the slag basicity is less heat intensive. Recalculating to the reduced coke consumption rate, the difference in heat demand amounts to 0.4 to 0.5 kg/MT of pig iron. It is shown that the slag viscosity increases to a lesser extent than when caused by a basicity increase when MgO content grows in slag at a temperature of 1450°С.