Numerical investigation of burden distribution in ironmaking blast furnace

The influence of central coke charging mode on the burden surface shape and distribution of a blast furnace

The burden surface shape and distribution in the shaft directly affect the gas distribution, heat transfer and chemical reactions inside the blast furnace. The current study developed a three-dimensional model of bell-less top charging to investigate the influence of the “central coke charging/sub-central coke charging” (CCC/SCCC) mode on the burden surface shape, burden distribution, and mass percentage of ore-to-coke (O/C). The results showed that the burden height of the region between the middle and edge is low by applying the CCC mode, while there is a heap valley in the center and a heap top in the middle region when the SCCC mode was adopted. In radial direction, the mass percentage of bigger size coke in the middle region is largest for the CCC mode, while the largest of the mass percentage was obtained in the center region by applying the SCCC mode. In longitudinal direction, the mass percentages of bigger coke and ore at the top region are largest for both modes. Besides, the mass percentage of O/C increased and then decreased to zero at the center for both modes. And the maximum of the mass percentage of O/C were 7.63 and 7.38, respectively.

Calculation of Coke Layers Situation in the Cohesive Zone of Blast Furnace

Coke is the only batch component that does not soften in blast furnace thermal conditions. It is especially important at the temperatures of the cohesive zone forming because coke layers are the only gas-permeable charge. The aim of the work described in this article is the identification of individual coke layers situation in the cohesive zone. Numerical calculations of the cohesive zone situation are based on the horizontal below burden probe measures, however, coke layers are calculated using analytical geometry. The results can be presented as a bitmap; the individual and total area of the coke layers passing gases through the cohesive zone is also calculated. This form of results allows for subjective but quick assessment of the blast furnace operation by its crew.

Model-Based Analysis of Factors Affecting the Burden Layer Structure in the Blast Furnace Shaft

The distribution of burden layers in an ironmaking blast furnace strongly influences the conditions in the upper part of the process. The bed permeability largely depends on the distribution of ore and coke in the lumpy zone, which affects the radial gas flow distribution in the shaft. Along with the continuous advancement of technology, more information about the internal conditions of the blast furnace can be obtained through advanced measurement equipment, including 2D profiles and 3D surface maps of the top burden surface. However, the change of layer structure along with the burden descent cannot be directly measured. A mathematical model predicting the burden distribution and the internal layer structure during the descending process is established in this paper. The accuracy of the burden distribution model is verified by a comparison with experimental results. A sensitivity study was undertaken to clarify the role of some factors on the arising layer distribution, including the descent-rate distribution, the initial burden surface profile, and the charging direction through the charging matrix. The findings can be used as a theoretical basis to guide plant operations for optimizing the charging.