Numerical Simulation of Burden Descending Behavior in Oxygen Blast Furnace

Abstract

In consideration of the environmental degradation and global scarcity of coking coal resource, substituting coke with coal and improving the gas utilization are the developing trends of ironmaking technology. Oxygen blast furnace, an ironmaking technology with top gas recycling, is most likely to be used in large-scale industrial manufacture considering its advantages of high productivity, high pulverized coal injection rate, low coke rate, high top gas calorific value, etc. The purpose of this paper is to make a little contribution to this technology on burden descending behavior in the metallurgical process. The results would provide reference for the design and operation of oxygen blast furnace. In the complex metallurgical processes with countercurrent multi-phase reactions, solid material motion plays important roles in the process since it determines the path and the residence time of the solid reactants as well as the stress distribution. The continuum model is often employed in the kinetic process analysis for its simplicity and low computational load. In this study, a viscous flow model based on the Navier-Stokes equation was developed to investigate the behavior of solid flow in oxygen blast furnace. A three dimensional experimental apparatus was constructed to observe burden descending behavior. According to concerned experimental results, it show that the interaction between the burden and the wall is not significant in shaft zone of the furnace. The descending burden maintains initial pattern until it reaches the lower part where the size of the cross section starts to reduce and the strong friction appears obviously in the tracked materials. Consequently, slip boundary condition with the Fanning equation was used for computations to describe the friction between solid flow and the wall or the dead zone. In addition, the position and the gas flow rate of the upper tuyeres were investigated. It was demonstrated that if the upper tuyeres are higher than the top of the belly, the position will strongly influence the solid flow distribution. Thus, gas velocity must be limited in a proper range to keep the solid flow falling down smoothly. By analysis of various solid viscosities, it is shown that solid flow patterns are not sensitive to solid viscosity within certain range.