Numerical Simulation of the 3D Asymmetric Inner States of an Ironmaking Blast Furnace Resulting From Circumferential Non-uniform Burden Distribution

The circumferential uniformity of burden distribution is of critical importance in maintaining the stable and efficient operation of blast furnaces (BFs). It significantly affects the circumferential gas distribution and the reduction process of ferrous materials. However, during the burden-charging process at the furnace top, circumferential non-uniformity inevitably occurs, especially for bell-less top BFs with parallel hoppers. So far, few studies have been reported on the effects of non-uniform burden distribution on the 3D asymmetric inner states of BFs. In this work, the effects of circumferential non-uniform ore-to-coke ratio on the cohesive zone (CZ) shape and location, multiphase flow, thermochemical behaviors, and overall BF performance are numerically studied. This is based on a recently developed 3D computational fluid dynamics (CFD) process model, which features the 3D-layered burden structure and CZ, trickling liquid flow, particle size degradation, and stockline variation. The results show that the high-temperature reducing gas generated in raceways is re-distributed during its ascending process to the furnace top due to the circumferential non-uniform ore-to-coke ratio and, hence, the bed permeability, leading to the increasing temperatures in the low ore-to-coke region but the decreasing ones in the high ore-to-coke region. This asymmetric thermal state results in the 3D inclined CZ, which increases the non-uniformities in gas pressure, and liquid mass flow rate and temperature at the slag surface. In addition, both the sinter reduction degradation and the coke size reduction due to gasification intensify in the high ore-to-coke region but attenuate in the low ore-to-coke region, which increases the BF non-uniformity of bed permeability, and hence, on the multiphase flow and thermochemical behaviors. Moreover, with the increase of circumferential non-uniform degree of ore-to-coke ratio, the average top gas temperature and average tuyere gas pressure slightly increase; however, the average liquid outlet temperature slightly decreases. The model comprehensively illustrates the 3D asymmetric inner states and overall performance resulting from non-uniform burden distribution, which provides an effective tool for BF operation and control in practice.