Simulation of Motion and Heat Transfer Characteristics of Blast-Furnace Slag Particles in a Cyclone Separator

In the process of gas granulation of blast furnace slag, a cyclone separator serves to cool slag particles and separate them from hot air. This study focuses on modelling the cooling of slag particles in a cyclone separator. Simulations revealed the airflow field, temperature field and particle trajectory distribution within the cyclone separator. Key parameters such as particle size, flow rate, and air velocity were examined for their influence on operational parameters. The findings indicate that air and particles in the cyclone move around the wall, with lower air velocities and temperatures in the central region and higher values near the wall. In the range of inlet air velocity of 15–20 m/s, particle size of 1–5 mm, and particle flow rate of 1–9 kg/s, increasing the inlet air velocity, reducing the particle size, and decreasing the particle flow rate prolongs the particle residence time in the separator by about 3 s, reducing the exit temperature and enhancing the waste heat recovery efficiency. The overall waste heat recovery efficiency of the particle population can reach more than 60%. An orthogonal parameter table was employed to analyse the influence of these factors. The hierarchy of effect on temperature reduction was found to be particle size > slag flow rate > inlet airflow velocity > initial temperature of the slag particles. Finally, the equation correlating the waste heat recovery efficiency with the dimensionless number was derived, with a maximum deviation of 5.41% from the simulation results.