Influence of rotary disk configurations on droplets characteristics in molten slag granulation for waste heat recovery

•The influence of disk configurations on droplets characteristics is investigated.•The droplets size, droplets size distributions, filament mass fraction and particle uniformity were analyzed.•A correlation of dm for four types of disks is presented.•The majority of the droplets size is populated in the range of 0.2–1.0 mm.•The flat/arc-edge disks represent a superior uniformity compared with the other disks. The influence of rotary disk configurations on droplets characteristics in molten slag ligament granulation was investigated by using the high-speed camera visualized system. Rosin/Paraffin mixture was adopted as the analogue of the molten slag according to the similarity theory. Four groups of disks with different configurations were studied. The droplets characteristics, such as droplets size, droplets size distributions, filament mass fraction and particle uniformity were analyzed. Generally, the droplets mean diameters (dm) decreases by increasing the rotary speed (ω) or disk diameter (D), and increases slightly by increasing the liquid flow rate (Q). Based on the experimental data, a simple correlation of dm for four types of disks is presented. The majority of the droplets size is populated in the range of 0.2–1.0 mm for all ω and Q, which accounts for over 70% mass fraction. The ω has significant influence on droplets size distribution and particle uniformity. The flat/arc-edge disk configurations can contribute to produce the narrower size range of droplets and obtain the superior particle uniformity compared to the other two types of disks. In the ligament breakup mode, the filament mass fraction reduces by increasing Q or decreasing ω. Meanwhile, the liquid film breakup mode also has significant impact on the formation of filament.