Understanding Slag Freeze Linings

Authors: Ata FallahMehrjardi Peter C Hayes Evgueni Jak

Publish Date: 2014/08/27

Volume: 66, Issue: 9, Pages: 1654-1663

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Abstract

Slag freeze linings the formation of protective deposit layers on the inner walls of furnaces and reactors are increasingly used in industrial pyrometallurgical processes to ensure that furnace integrity is maintained in these aggressive hightemperature environments Most previous studies of freezelinings have analyzed the formation of slag deposits based solely on heat transfer considerations These thermal models have assumed that the interface between the stationary frozen layer and the agitated molten bath at steadystate deposit thickness consists of the primary phase which stays in contact with the bulk liquid at the liquidus temperature Recent experimental studies however have clearly demonstrated that the temperature of the deposit/liquid bath interface can be lower than the liquidus temperature of the bulk liquid A conceptual framework has been proposed to explain the observations and the factors influencing the microstructure and the temperature of the interface at steadystate conditions The observations are consistent with a dynamic steady state that is a balance between I the rate of nucleation and growth of solids on detached crystals in a subliquidus layer as this fluid material moves toward the stagnant deposit interface and II the dissolution of these detached crystals as they are transported away from the interface by turbulent eddies It is argued that the assumption that the interface temperature is the liquidus of the bulk material represents only a limiting condition and that the interface temperature can be between T liquidus and T solidus depending on the process conditions and bath chemistry These findings have implications for the modeling approach and boundary conditions required to accurately describe these systems They also indicate the opportunity to integrate considerations of heat and mass flows with the selection of melt chemistries in the design of future high temperature industrial reactorsThe authors would like to thank the Australian Research Council Linkage program Rio Tinto Kennecott Utah Copper Corp Xstrata Technology Xstrata Copper BHP Billiton Olympic Dam Operation and Outotec Finland Oy for their financial support for the project Thanks are also given to Lloyd Nelson Anglo American Platinum Phil Mackey PJ Mackey Technology and Rodney Jones MINTEK for their valuable suggestions on industrial applications of freeze linings

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