Gas Permeability Improvement Mechanism at the Blast Furnace Cohesive Zone by Mixed Coke Charging in Ore Layer and Effect of Coke Mixing for Different Cohesive Zone Condition on Gas Permeability

A major operational problem in increasing pulverized coal rate and decreasing coke rate must be the increased pressure drop or the worsened gas permeability at the lower part of the blast furnace. In order to decrease the pressure drop at the blast furnace cohesive zone (CZ) under low coke rate operation, this study has focused on mixed coke charging in the ore layer. Results obtained by numerical analysis and experiments are as follows:(1) Numerical analysis using DEM (Discrete Element Method) clarified the change in the cohesive ore bed structure with mixed coke charging and the formation conditions of gas path in the bed. Also, DEM-CFD (DEM and Computational Fluid Dynamics) analysis enabled us to find a gas permeability improvement mechanism and an optimum coke mixing ratio for different CZ conditions before applying the technology.(2) Experiments in blast furnace hot model demonstrated the decreased pressure drop at the CZ by mixed coke charging in the ore layer. The experimental results abided by the numerical analysis results.