Numerical Simulation of Effect of Tuyere Angle and Wall Scaffolding on Unsteady Gas and Particle Flows Including Raceway in Blast Furnace

Abstract

We have performed the numerical simulation for the particle and gas flows in the raceway region in a blast furnace of which dimension is almost the same as that of the commercial blast furnace using Distinct Element Method for the computation of the multi-body interaction among coke particles, Hard Sphere Model for two body interaction of powder particles based on Direct Simulation of Monte-Carlo Method, and Finite Difference Method for the numerical analysis of Navier–Stokes equations with the interaction terms between gas and particles for the gas flows. In the present simulation we have calculated the particle and gas flows in the raceway regions in which tuyere angles are 0, 3, 7 and 11 degree downward. The downward inclination of tuyere means that the air injects to the higher pressure side. This would stabilize the air flow and the raceway would become stable. However if the inclination angle is too high, the flow becomes unstable by various conditions near the bottom of blast furnace. The coke particle flow rate from the center region of blast furnace and its flow width increase with increasing the tuyere downward angle from the horizontal and attains the maximum value at near 7 degree. It means that the coke particle flow becomes widely uniform at about 7 degree tuyere angle except the region near the furnace wall.
We have also calculated the effect of scaffolding on the furnace wall on the particle and gas flows. The coke particle flow distributions with scaffolding on the wall become narrower. The scaffolding is nearer to the raceway, the effect of that becomes stronger. The raceway is not spherical and becomes unstable in cases with scaffolding on the wall. The coke particle velocity becomes higher by the narrow coke particle flow distribution caused by the existence of the scaffolding on the wall and it concentrates coke particles on the upper part of raceway near the furnace wall. The coke particle flow is dammed by the scaffolding and the wide area in which the coke particle velocity is very low is formed on the scaffolding. The gas flow distribution with scaffolding becomes non-uniform, particularly in the area between the softening melting cohesive zones and the scaffolding due to their interaction. The gas flow is also dammed up by the scaffolding and softening melting cohesive zones. The existence of scaffolding near softening melting cohesive zones strongly affects the gas flow.