Centrifugal granulation performance of liquid with various viscosities for heat recovery of blast furnace slag

Centrifugal granulation is a crucial step in the most promising heat recovery technique for molten blast furnace slag. Facing the fact that slag viscosity changes during the granulation process, in the present work, visualization experiments were conducted for centrifugal granulation of mixture liquids by a spinning disc. Then, the effect of liquid viscosity on granulation performance was discussed. It was found that the increase in liquid viscosity resulted in granulation mode translation under the same disc rotating speed and liquid flow rate, that is, from direct droplet formation mode to ligament formation mode. The Sauter Mean Diameter of the granulated droplets was increased and the droplets size distribution was narrowed with increasing liquid viscosity. Meanwhile, the ligament number increased in direct drop formation mode while decreased in ligament formation mode as the liquid viscosity was increased. Furthermore, for a specific mixture liquid, the increase in flow rate also resulted in the translation from direct droplet formation mode to the ligament formation mode and from ligament formation mode to the film formation mode in the end. The critical flow rate for this translation was found for various liquid mixtures. Finally, dimensionless correlations were developed to predict the average diameter and critical flow rate, and the analogy analysis was applied to the molten blast furnace slag.