Abstract
The ore-free zone in the center of the blast furnace throat is a major feature of the charging system, ensuring the permeability of the center. Factors that influence the formation of the ore-free zone need to be researched to increase the control precision. In this paper, on the basis of a 1:1 3D model of a blast furnace, the formation of an ore-free zone at the burden surface at the throat was simulated by using the discrete element method (DEM). The effects of burden line depth, batch weight, and distribution angle on the formation of ore-free zones were investigated. The results showed that with increasing burden line depth, the width of the ore-free zone increased, the thickness decreased, the ore-to-coke ratio decreased, and the central airflow developed. Only changing the ore batch weight affected the thickness and width of the ore-free zone and had a greater impact on the permeability of the ore-free zone. The greater the ore batch weight was, the worse the permeability, while changing the batch weight of both coke and ore mainly affected the thickness of the ore-free zone. The greater the batch weight of coke and ore was, the greater the thickness of the ore-free zone. In the case of changing only the angle of ore in the matrix, with the angle increasing, the ore-to-coke ratio around the ore-free zone decreased, the ore-to-coke ratio around the furnace wall increased, and the edge airflow was suppressed. In the case of changing the angle of coke and ore at the same time, with the simultaneous increase in both angles, the ore-free area was compressed in the direction of smaller charge segregation, the area with better permeability in the center of the furnace throat was reduced, and the central airflow was suppressed.