2021 Volume 61 Issue 12 Pages 2979-2990
With the depletion of high-grade iron ore and increase in amount of steel scrap, a new ironmaking process utilizing both low-grade iron ore and/or steel scrap is required. The blast furnace and packed bed type partial smelting reduction process (PSR) are the most prospective reactors. When steel scrap is used as an iron source, the hot metal composition should be precisely controlled, because tramp elements such as Cu, Sn, Ni, and Cr are dissolved in hot metal. An analysis model was developed to simulate the equilibrium of the slag–metal reaction at the bottom of such reactors. The effect of scrap ratio (iron mass ratio of scrap to scrap and sinter) on hot metal and molten slag composition was thermodynamically analyzed and the optimal composition of hot metal under controlled temperature and PO2 was investigated. Si and Mn were found to be significantly oxidized relative to the equilibrium state, and the S content was equal to that at equilibrium under a blast furnace condition. As the scrap ratio increased, the Si, Mn, and P contents decreased. The Si content decreased to 0.1 mass% at T = 1773 K and PO2 > 10−13 atm or at PO2 = 3.03×10−15 atm and T < 1690 K, whereas the phosphorus content decreased at 1773 K and PO2 > 10−12 atm when the scrap ratio was 0.5. PSR is expected to produce hot metal with a low impurity content by controlling the oxygen partial pressure at the bottom of the furnace.