Numerical simulation of continuous solidification process for blast furnace slag droplets

The crystallization behavior of granulated blast furnace slag droplets during cooling reduces their commercial value. In order to investigate the solidification characteristics of droplets under varying cooling conditions, a numerical simulation of the continuous solidification process was performed by integrating a droplet flight model with an enthalpy-based slag crystallization model. The results show that an increase in droplet size leads to a significant increase in the distance required for surface crust formation, and also results in an increase in the average crystalline phase content after cooling. Droplet size becomes a key factor governing solidification behavior and crystalline phase growth by influencing internal heat conduction rates and cooling uniformity. A 5-mm molten droplet at 15 m/s initial velocity requires 16 m horizontal flight to avoid remelting during cooling; increasing the primary fluidized bed convective heat transfer coefficient from 70 W·m⁻²·K⁻¹ to 150 W·m⁻²·K⁻¹ shortens this distance to 12 m. Two-stage molten droplet cooling must be matched: extending flight distance during surface crust formation reduces bed cooling intensity requirements, while increasing bed cooling intensity decreases granulation device size.