Investigation of Freeze Linings in Copper Containing Slag Systems

摘要

Slag freeze linings are increasingly used in industrial pyrometallurgical processes to ensure furnace integrity is maintained in aggressive high temperature environments. Most previous studies of freeze linings have analysed the formation of slag deposits based on heat transfer models. The focus of the present research is to determine the impact of chemistry on the microstructures, thickness, stability and heat transfer characteristics of the frozen deposit. The formation of the freeze linings is studied under controlled laboratory conditions using an air-cooled "cold finger" that is immersed into a synthetic slag bath heated in an induction furnace. The temperature profile across the deposit is also been measured. A Cu-Fe-Si-Al-O slag has been selected for study; the primary phase for the slag has been shown to be delafossite and liquidus temperature of the slag has been determined. The phase assemblages and microstructures of the deposits formed in the cold finger experiments differ significantly from those anticipated from equilibrium cooling of the slag. The freeze lining deposits have been found in general to consist of several different layers. Starting from the cold wall these layers consist of glass; glass with microcrystalline precipitates; multiphase sub-liquidus material containing delafossite and cuprite crystal phase assemblages and high-silica metastable liquid that was separated from the bulk liquid (closed layers); phase assemblages containing delafossite and cuprite crystals and a high-silica liquid phase that is connected to the bulk liquid (open layers), and the outer layer containing a complex mixture of liquid and solid phases. The findings have significant practical implications, and potential for the improved design and operation of industrial metallurgical furnaces.