Change and mechanism analysis of the softening-melting behavior of the iron-bearing burden in a hydrogen-rich blast furnace

Abstract

The effect of hydrogen-rich smelting on the softening-melting behavior of the iron-bearing burden in a blast furnace (BF) was analyzed by simulating the actual burden structure of the BF and by studying the changes in the softening-melting behavior of the iron-bearing burden as well as the reaction behavior and interface characteristics of coke and slag-iron in the high-temperature zone. The influence mechanism of the softening-melting behavior of the iron-bearing burden after hydrogen-rich smelting in the BF was analyzed. The results show that after hydrogen-rich smelting in the BF, Ti decreases, T10% and T40% increase, ΔT increases when ϕ(CO) is 30%, ΔT decreases when ϕ(CO) is 40%, and the shrinkage rate decreases significantly at the same temperature. The assimilation of the burden is weakened, and the smelting reduction erosion of coke is decreased. Ts and Td increase substantially, Tds decreases, and ΔPmax and S decrease. An increase in ϕ(H2) causes the softening-melting zone to move downward and become narrow, effectively improving the permeability. When 10% H2 is used instead of 10% CO, the softening-melting zone becomes narrow and moves to the high-temperature zone, and the permeability of the burden improves, which shows that the influence of H2 on the softening-melting zone is stronger than that of CO. After hydrogen-rich smelting, at 1673 K, the metallic iron phase gradually changes from a fragmental distribution to a flaky distribution, and the amount of molten slag and iron infiltrated into the pores of coke decreases. In addition, the amount of nonreduced wustite decreases substantially; the ash content on the coke surface is high; and hydrogen-rich smelting increases the temperature at which the slag phase and the ash on the coke surface fuse together. At 1713 K, a large amount of slag accumulates at the reaction interface of coke and hinders the carburization of iron.