Modeling Freeze-Lining Formation: A Case Study in the Slag Fuming Process

Slag fuming (SF) is a metallurgical process designed to recycle Zn-containing slags derived from various industrial residues. To protect the reactor from corrosive molten slag, a deliberate as-solidified slag layer, known as a freeze lining (FL), is formed on the reactor walls using intense water-cooled jackets. In this article, a computational-fluid-dynamics-based model capable of simulating FL formation in a SF furnace is presented. To capture the complex multiphase flow dynamics, heat transfer, and FL formation during SF, a volume-of-fluid model is coupled with a mixture continuum solidification model. Three phases are considered: gas, liquid bulk slag, and solid slag (FL). Moreover, two types of FL are distinguished: one that solidifies on the reactor wall in the bulk slag region and another that solidifies on the reactor wall in the freeboard region owing to slag splashing. Comparisons between calculated FL thickness and heat fluxes and corresponding industrial data demonstrate satisfactory agreement. In this outcome, the robustness of the model is underscored and confidence in its accuracy is instilled. In the simulation results, valuable insights are provided into the evolution of the fuming process, particularly regarding the slag bath temperature, slag splashing dynamics, FL formation, local heat fluxes through the reactor wall, and global net energy balance.