Freeze-Lining Formation Under Natural and Forced Flow Conditions

Abstract This study presents an integrated experimental and numerical investigation of freeze-lining (FL) formation during the solidification of molten slag under natural and forced flow conditions. Laboratory experiments involved immersing a gas-cooled probe into molten slag contained in a crucible. Continuous probe cooling promoted FL growth, while controlled crucible rotation imposed forced convection. This setup enabled in situ monitoring of FL evolution under different conditions and provided high-fidelity data for model calibration and validation. Measurements included FL thickness evolution, temperature profiles near the crucible wall and within the solidifying layer, and the thermal response of the internal gas cooling. A CFD model was developed using an enthalpy-based mixture continuum approach, extended to incorporate centrifugal, Coriolis, and Euler forces within the Boussinesq approximation to enable a physically sound simulation of rotating slag systems. The model achieved good agreement with experimental measurements, with minor deviations attributed to thermocouple positioning uncertainties. The simulation results demonstrated that crucible rotation shifts the internal flow from buoyancy-driven recirculation to a toroidal mixing pattern, creating a more uniform temperature field that significantly alters FL evolution. Thermal boundary conditions were determined through systematic inverse modeling, including the convective heat transfer coefficient at the slag–gas interface and the probe heat flux. Notably, the gas-side heat flux measurements was found to overestimate the effective slag-side heat flux by approximately 75 pct, a finding with direct practical implications for future cooled probe experiments. The model validation under both static and rotating conditions advances the predictive capability of FL models and provides a benchmark dataset relevant to refractory protection and energy efficiency in pyrometallurgical processes.