Predicition of Stable and Unstable Flows in Blast Furnace Raceway Using Numerical Simulation Methods for Gas and Particles

We have numerically simulated the particle and gas flows in the raceway region in an actual blast furnace of which dimension is 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 simulations we have taken the existence of softening melting zones into account. The present calculation results indicate the raceway pattern, its fluctuations with various periods. The results also indicate the velocity distributions of coke, powder and gas, and packing ratio distributions of these particles. The dynamical characteristics fluctuate and are unstable. The highly packed coke and powder particle layers are formed in the lower core and in the lower wall regions under the tuyere due to the air and these particle flows. The high air velocity region appears in the layer between the softening melting zones and the highly packed furnace lower core region, and the unstable high air velocity region is produced near the furnace wall and on the raceway by the existence and the disappearance of softening melting zones. The coke and powder particles and the softening melting zones would yield the unstable state in the furnace. The powder particles circularly spread and make the circularly multi-layered powder particle clusters caused by the particle collisions and the breakage of clusters. Some of the powder particles flow upward and others are packed in the furnace lower core region by the particle and the air flows. Our calculated results present an unusual phenomenon example in the blast furnace, that is, the unusual high air velocity wide region touched to the furnace wall is formed due to the effect of the softening melting zones and the accumulation of small coke particles in the furnace center region.