The prediction and representation of phase equilibria and physicochemical properties in complex slag systems
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The Prediction and Representation of Phase Equilibria and Physicochemical Properties in Complex Slag Systems E. JAK, A. KONDRATIEV, S. CHRISTIE, and P.C. HAYES The development of new experimental techniques for the determination of phase equilibria in complex slag systems, chemical thermodynamic, and viscosity models is reported. The new experimental data, and new thermodynamic and viscosity models, have been combined in a custom-designed computer software package to produce limiting operability diagrams for slag systems. These diagrams are used to describe phase equilibria and physicochemical properties in complex slag systems. The approach is illustrated with calculations on the system FeO-Fe2O3-CaO-SiO2-Al2O3 at metallic iron saturation, slags produced in coal slagging gasifiers, and in the reprocessing of nonferrous smelting slags. This article was presented at the Mills Symposium “Molten Metals, Slags and Glasses-Characterisation of Properties and Phenomena” held in London in August 2000. I. INTRODUCTION
RECOGNIZING the importance of slag chemistry to metal smelting and refining processes, there has been an ongoing research effort over many decades to experimentally determine phase equilibria and physicochemical properties of slags.[1-4] Much of the fundamental understanding of these systems has been derived from the study of binary and ternary systems. This approach is justified on two counts: (a) the complexity of the chemical interactions of the components, which cannot be accurately predicted from first principles; and (b) the magnitude of the task of experimentally determining the behavior for all combinations of composition, oxygen potential, and temperature to characterize these systems. In practice, primary metal smelting slags contain many chemical components because these are present in the ore feed. With the pressure to optimize the efficiencies of plant operations to improve economic performance, there is a need to provide more adequate descriptions of chemistry of industrial slags than are currently available. The development of chemical thermodynamic models and their ability to provide in mathematical terms descriptions of many component systems, combined with greatly increased computing power, has significantly enhanced our capacity to describe the behavior of complex slag systems.[5–8] These models can be used to provide a trend analysis to the operator, or, if sufficiently accurate, can be incorporated into the control systems of industrial operations. However, these thermodynamic models can only be as accurate as the experimental data used in their construction. It has become clear from the database development undertaken by the present authors that the availability of data in complex systems is a E. JAK, Research Director, is with Centre for Coal in Sustainable Development, Brisbane, Australia, and PYROSEARCH, Pyrometallurgy Research Centre, School of Engineering, The University of Queensland, St Lucia, Queensland, 4072, Australia. A. KONDRATIEV, Postgraduate St
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