Dynamic analysis of liquid permeability in the dripping zone of blast furnace and reaction behavior at the slag-coke interface

Abstract

The dripping zone connects the cohesive zone and the hearth, it is one of the key areas of the blast furnace (BF). This study aims to explore the mechanism of the dripping process in BF. The dripping experiments under different conditions were carried out. Dynamics of liquid permeability in the dripping zone was analyzed, the reaction behavior at the slag-coke interface was investigated, and the consumption of coke in the dripping zone was clarified. The results show that: The retention ratio increases with the increase of Al2O3 content. The increase in retention ratio is related to the viscosity of slag. Once the Al2O3 content in slag increases, Si4+ coordination polymer ions in tetrahedra will be replaced by Al3+ cations, forming a tetrahedral structure of [AlO4]5– tetrahedron. The retention ratio decreases with the increase of FeO content. The dissociation of free oxygen ions (O)2– from FeO increases the concentration of free oxygen ions (O)2– in slag, this reduces the viscosity of slag. The presence of FeO can compensate for the increase in retention ratio caused by Al2O3. The quantitative relationship between retention ratio and Al2O3 content and FeO content in slag is obtained. The reduction reaction of FeO occurs at the slag-coke interface, the molten iron takes on the shape of small iron beads, which is the result of multiple small droplets gathering. The reduction of TiO2 is carried out by a series of reactions, the Ti exhibits a granular embedding state in molten iron, its color is darker than that of molten iron and its particles have distinct edges and corners. In the slag-coke area of retained sample, the reduction reaction occurs between coke and oxides in slag. The carbon will be consumed, resulting in a decrease in particle size. In the iron-coke area of retained sample, the carburization reaction occurs in large quantities due to the carbon content of molten iron in hearth is undersaturated, coke is further consumed.