2012 Volume 98 Issue 7 Pages 341-350
Low reducing agent operation of large blast furnace has attracted a special attention from the background of the global warming. Because the coke ratio is reduced in this operation, causing a huge local ventilation resistance that causes operational problems, it has become increasingly necessary to understand the operation of blast furnace based on non-empirical phenomena. Among the most promising numerical approaches is a combination of the discrete element method (DEM) and computational fluid dynamics (CFD). In this study, particle-based model was newly developed, which considers heat transfer, mass transfer and chemical reactions in the shaft part of blast furnace. It became possible to analyze the three-dimensional discontinuous phenomena among particle with gas flow.
Because this model was developed to expand the spatial scale more than conventional analysis, the discontinuous factors made it possible to simulate by the behavior of discrete particles. The particle arrangement and the packed bed structure were evaluated for studying the flow structure, temperature and composition distribution. Remarkable change in the heat and mass transfer characteristic appeared in the interface between coke and ore layer, and near the wall. The ore and coke particle mixture system, which was expected to improve reducing rate due to the dense packing, is relatively-ineffective. Rather, a low permeability resistance improved reducing rate, it means convection effect was larger. Degree of freedom of particle arrangement is high, and its large influence on temperature and reaction distribution, it was able to show the usefulness of this model.