Abstract
The solid flow plays an important role in blast furnace (BF) ironmaking. In the paper, the descending behavior of solid flow in BFs was investigated by a cold experimental BF model and numerical simulation via the discrete element method (DEM). To eliminate the flat wall effect on the structure of solid flow in lab observations, a cutting method was developed to observe the vertical section of the solid flow by inserting a transparent plate into the experimental BF model. Both the experimental and numerical results indicated that plug flow is the main solid flow pattern in the upper and middle zones of BFs during burden descending. Meanwhile, a slight convergence flow and a deadman zone form at the lower part of the bosh. In addition, the boundary between the plug flow and convergence flow in BFs was determined by analyzing the velocity of the burden in vertical directions and the Wilcox–Swailes coefficient (Uws). The results indicated that the Uws can be defined as a critical value to determine the solid flow patterns. When Uws ≥ 0.65, the plug flow is dominant. When Uws < 0.65, the convergence flow is dominant. The findings may have important implications to understand the structure of the solid flow in BFs.
Highlights
Blast furnaces (BFs) are complex metallurgical reactors that produce pig iron
The findings may have important implications to understand the structure of the solid flow in BFs
As for the phenomena shown in Figure 3c1, it can be found that when the wall effect was eliminated using the cutting method, the plug flow zone covers most of the area in the BF, which agrees well with the observation shown in the 3D full-circle
Summary
Blast furnaces (BFs) are complex metallurgical reactors that produce pig iron. During the ironmaking process for BFs, the layered coke and ore particles are charged into the top of the BF. The ore pellets are reduced during the process of burden descending and gradually become small and soft until they melt to liquid iron In such a complicated multiphase chemical reaction system, the descending behaviors of coke and ore in BFs directly affects the gas flow distribution, heat–mass transfer, and gas–solid reactions in the BF, which all play a significant role in achieving a smooth operation of the BF. To eliminate the wall effect, a novel cutting method for the burden was developed to observe internal structure of the solid flow in BFs. two numerical DEM sector models were used to verify the experimental models and examine the characteristics of solid flow under different burden layer conditions, such as full coke, layered coke/ore pellet, and mixed coke/ore pellet. The findings may have important implications to understand the structure of the solid flow in BFs
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