Simulation of Slag Freeze Layer Formation: Part I. Experimental Study

This study was conducted to understand the freeze layer formation and heat transfer that is required to design cooling systems in pyrometallurgical operations in which a frozen slag layer is used to protect the furnace wall. Similar Grashof and Prandtl numbers for operating furnaces were obtained in a 200-mm square cavity differentially heated on the sides containing an aqueous solution of calcium chloride. The solid front was tracked using a digital camera, and the temperature field was measured with thermocouples. The flow velocity field was measured using the two-dimensional particle image velocimetry technique. Experiments were conducted over a range of superheat conditions, and the solidification front was planar (i.e., neither cellular nor dendritic) because the system slowly approached steady state. The two-phase zone comprised particles circulating slowly with the liquid in the bulk of the cavity; at the vertical walls, velocities were higher.