A novel method for modeling the phase change of iron ore particles in the cohesive zone of a blast furnace

Abstract

Cohesive zone plays a vital role in the stable operation of a blast furnace (BF), yet the complex phase change process of iron ore particles in this zone is still not well understood. In this study, a novel one-dimensional (1D) unsteady phase change model was developed to elucidate the heat transfer and melting mechanisms of iron ore particles. After model validation, the effects of several key operating parameters (e.g., particle diameter, gas velocity, initial temperature) on the phase change behavior of iron ore particles were analyzed, and the joint effect of multiple parameters was discussed. The results show that larger-sized iron ore particles possess lower specific surface areas, which in turn reduces their convective heat absorption capacity. Consequently, the distance from the solid-liquid phase interface to the particle surface increases, thereby slowing down the movement of the phase interface and prolonging the melting duration of the particles. Increasing the gas velocity and the initial temperature does not have a significant impact on reducing the duration of the complete melting process. Under the specified conditions, it is observed that increasing the gas velocity by 3-fold and 9-fold results in a reduction of the melting duration by 2.4% and 8.3%, respectively. Elevating the initial temperature of iron ore particles results in a decrease in the core-to-surface temperature difference, a slower heating rate, and a shorter duration to achieve melting. Among the factors affecting the melting process, the particle diameter is found to be the most significant in terms of the liquid phase precipitation, mushy zone thickness, and core-to-surface temperature difference of iron ore particles.