Optimizing heat transfer and solidification crystallization in dry granulation of blast furnace slag

In the process of recovering waste heat from blast furnace slag, controlling the crystallization of slag is crucial for the safe and efficient operation of centrifugal granulation equipment and the effective utilization of granulated slag. In this study, a novel heat transfer model for slag solidification was proposed using the enthalpy method, incorporating circumferential asymmetric heat transfer and variable physical parameters. The model establishes a relationship between initial operating conditions and the quantity of precipitated slag crystals, providing a theoretical foundation for optimizing granulation bin size, preventing slag adhesion, and enhancing slag utilization. The research reveals a temperature disparity of over 300 K between the center and surface of slag grains. As the center temperature approaches the liquid-phase line, the slag enters a slow cooling interval that determines the crystallization quantity. The diameter of slag grains is identified as the most influential factor, with crystallization increasing from 0.90 % to 35.42 % as the diameter expands from 1 mm to 5 mm. The optimal conditions for desired crystallization are an initial temperature above 1711 K, a particle diameter below 2.2 mm, an air temperature under 838 K, and a particle flight speed above 8 m·s⁻¹. These insights guide practitioners in optimizing slag granulation processes.