DEM-CFD model considering softening behavior of ore particles in cohesive zone and gas flow analysis at low coke rate in blast furnace

Since the cohesive zone has a great influence on the gas flow in the blast furnace, modeling of the cohesive zone is considered to be an important subject. In the cohesive zone, the softening and melting behavior of ore particles is affected by the load from the upper layer and the temperature distribution, and the pressure drop of the ore layer increases remarkably due to shrinkage of the ore particles. In this study, a model of the cohesive zone considering physical properties such as Young's modulus was developed on the basis of the discrete element method, which can track the individual motions of the numerous particles in a packed bed. To determine the appropriate Young's modulus of ore particles for the cohesive zone, element model calculations for a softening test under load were carried out, with particular attention to change in the void fraction. The optimized value of Young's modulus value was then introduced in the discrete element method and computational fluid dynamics (DEM-CFD) model. The changes of gas flow in the vicinity of the cohesive zone were visually expressed by this model. These results were similar to those of cold model experiments and the burden structure observed in the dissected blast furnace. The influence of the coke rate on the gas flow was also analyzed using the above model. The change in the gas flow under a low coke rate condition could be well recognized.