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

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, T-i decreases, T(10% )and T(40% )increase, Delta T increases when phi(CO) is 30%, Delta T decreases when phi(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. T-s and T-d increase sub- stantially, T-ds decreases, and Delta P-max and S decrease. An increase in phi(H-2) causes the softening-melting zone to move downward and become narrow, effectively improving the permeability. When 10% H-2 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 H-2 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. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.