Denis Shishin

Thermodynamic Optimization of the Ca-Fe-O System

The present study deals with the thermodynamic optimization of the Ca-Fe-O system. All available phase equilibrium and thermodynamic experimental data are critically assessed to obtain a self-consistent set of model parameters for the Gibbs energies of all stoichiometric and solution phases. Model predictions of the present study are compared with previous assessments. Wüstite and lime are described as one monoxide solution with a miscibility gap, using the random mixing Bragg-Williams model. The solubility of CaO in the “Fe3O4” magnetite (spinel) phase is described using the sublattice model based on the Compound Energy Formalism. The effect of CaO on the stability of the spinel phase is evaluated. The liquid CaO-FeO-Fe2O3 slag is modeled using the Modified Quasichemical Formalism. Liquid metal phase is described as a separate solution by an associate model.

Improved Copper Smelter and Converter Productivity Through the Use of a Novel High-Grade Feed

Copper sulphide processing technologies face increasing pressures associated with decreasing concentrate grade leading to increasing thermal inefficiency and lower productivity. Impurity concentrations are on average increasing, creating potential environmental risk and additional treatment costs. In copper flash smelters dust, partially oxidised materials and fume formed from the condensation of volatile impurities, are routinely recycled to the feed. In the converting stage the heat balance is maintained by charging anode reverts and other inert materials. In both cases, the thermal energy available from sulphide oxidation is not fully utilised or optimised. The productivities of both smelter and converter stages can be potentially increased through the addition of a high copper, low iron, low impurity precipitated copper product. Calculations are carried out for fayalite smelter and calcium ferrite converter slags using an optimised FactSage thermodynamic database. The potential for significant increases in smelter and converter productivities using existing technologies are predicted.

Multicomponent Thermodynamic Databases for Complex Non-ferrous Pyrometallurgical Processes

The pyrometallurgical production and recycling of non-ferrous metals involves the use of complex feed stocks, having a wide range of chemical compositions from sources that include mineral sulphide concentrates, high value obsolete materials and process wastes. The commercial viabilities of these operations hinge on the ability to extract value from these materials. Increasingly, modern computer-based tools are used to describe and predict process outcomes, including mass and heat balances, the partitioning of elements and phase equilibria. At the heart of these predictive tools are thermodynamic databases that describe the fundamental chemical properties of a system and all the components present. A comprehensive research program has been established to develop an accurate, self-consistent thermodynamic database describing all gas-slag-matte-metal-speiss-solid phases in the system Cu2O-PbO-ZnO-Al2O3-CaO-MgO-FeO-Fe2O3-SiO2-S-(As-Bi-Sb-Sn-Ag-Au). The database can be used in conjunction with the FactSage computer platform. The accuracy of the database and its application to industrial practice is demonstrated.

Investigation of the influence of heat balance shifts on the freeze microstructure and composition in aluminum smelting bath system: Cryolite-CaF2-AlF3-Al2O3

In an aluminum electrolysis cell, the side ledge forms on side walls to protect it from the corrosive cryolitic bath. In this study, a series of laboratory analogue experiments have been carried out to investigate the microstructure and composition of side ledge (freeze linings) at different heat balance steady states. Three distinct layers are found in the freeze linings formed in the designed Cryolite-CaF2-AlF3-Al2O3 electrolyte system: a closed (columnar) crystalline layer, an open crystalline layer, and a sealing layer. This layered structure changes when the heat balance is shifted between different steady states, by melting or freezing the open crystalline layer. Phase chemistry of the freeze lining is studied in this paper to understand the side ledge formation process upon heat balance shifts. Electron probe X-ray microanalysis (EPMA) is used to characterize the microstructure and compositions of distinct phases existing in the freeze linings, which are identified as cryolite, chiolite, Ca-cryolite, and alumina. A freeze formation mechanism is further developed based on these microstructural/compositional investigations and also thermodynamic calculations through the software—FactSage. It is found that entrapped liquid channels exist in the open crystalline layer, assisting with the mass transfer between solidified crystals and bulk molten bath.

Integrated Experimental and Modelling Research for Non-Ferrous Smelting and Recycling Systems

The chemistries of industrial pyrometallurgical non-ferrous smelting and recycling processes are becoming increasingly complex. Optimisation of process conditions, charge composition, temperature, oxygen partial pressure, and partitioning of minor elements between phases and different process streams require accurate description of phase equilibria and thermodynamics which are the focus of the present research. The experiments involve high temperature equilibration in controlled gas atmospheres, rapid quenching and direct measurement of equilibrium phase compositions with quantitative microanalytical techniques including electron probe X-ray microanalysis and Laser Ablation ICP-MS. The thermodynamic modelling is undertaken using computer package FactSage with the quasi-chemical model for the liquid slag phase and other advanced models. Experimental and modelling studies are combined into an integrated research program focused on the major elements Cu-Pb-Fe-O-Si-S system, slagging Al, Ca, Mg and other minor elements. The ongoing development of the research methodologies has resulted in significant advances in research capabilities. Examples of applications are given.

Case Study on the Application of Research to Operations—Calcium Ferrite Slags

The Top Submerged Lance (TSL) technology, developed in the 1970s, is now widely used for the processing of a range of materials. TSL technology for continuous converting was first patented in the 1990s. The process is based on the use of calcium ferrite slag. Although this slag system had been applied elsewhere the phase equilibria had not been thoroughly investigated. This lead to a collaboration between the Process Technology group of Mount Isa Mines, now part of Glencore, and the Pyrometallurgy Innovation Centre (PYROSEARCH) at The University of Queensland. Through multiple research programs this complex system was successfully investigated. The results were then implemented within thermodynamic modelling tools. This combined new knowledge was then applied to the design and industrial implementation of the TSL continuous converting technology, ISACONVERT™. This paper describes the key findings of the research and how this was applied to the industrial implementation of the technology.

Advanced Thermochemical Fundamental and Applied Research to Improve the Integrity of the Steel Water Jacketed Furnace at Port Pirie

Lead blast furnace water-jacket stability was investigated by examining samples from the Port Pirie Lead Smelter. The compositions of the phases formed in the samples were analysed using Scanning Electron Microscopy (SEM) and Electron Probe X-ray Microanalyser (EPMA). Phase equilibria analysis and thermodynamic modelling was undertaken using FactSage with latest thermodynamic database for the slag/matte/metal/speiss/solids multi-component Cu2O–PbO–ZnO–Al2O3–CaO–MgO–FeO–Fe2O3–SiO2–S major and As–Bi–Sb–Sn–Ag–Au minor elements system. Results indicated that the stability of the water-jacket steel wall without freeze-lining is influenced by formation of the complex Fe-rich speiss phase at critical As concentrations. The integrity of the furnace walls with freeze-lining is critically dependent of the stability of the oxide-based freeze-lining which is dependent on various factors including most critical one—the proportion of solids determined by the slag chemistry and fluxing. Thermodynamic modelling of the lead blast furnace operation indicated limiting thermochemical conditions for the water-jacket stability. Factors and controls critical to the water-jackets integrity are discussed.

Modelling of liquid phases and metal distributions in copper converters: transferring process fundamentals to plant practice

ABSTRACT The quantity and accuracy of fundamental data available on copper smelting and converting systems has greatly increased over the past several decades. Engineers need no longer rely on approximations and interpolation of chemical behaviour from idealised or simplified low-order systems. Sophisticated thermodynamic databases and dedicated thermodynamic computer platforms make it possible to predict the outcomes of complex multicomponent, multiphase reactions, and to present this information in forms that are useful for industrial practice. In the present paper a summary and review of phase equilibria data on key Cu-Fe-O-S sub-systems including Ca, Si and minor elements, is provided, as are examples of the application of thermodynamic and thermochemical calculations to the modelling of copper converting. As further information on chemical behaviour and integration with process models become available these sophisticated predictive tools and approaches will become increasingly used to improve metallurgical process design and efficiency, and to optimise the productivity of integrated copper production operations.

High-temperature experimental and thermodynamic modelling research on the pyrometallurgical processing of copper

Uncertainty in the metal price and competition between producers mean that the daily operation of a smelter needs to target high recovery of valuable elements at low operating cost. Options for the improvement of the plant operation can be examined and decision making can be informed based on accurate information from laboratory experimentation coupled with predictions using advanced thermodynamic models. Integrated high-temperature experimental and thermodynamic modelling research on phase equilibria and thermodynamics of copper-containing systems have been undertaken at the Pyrometallurgy Innovation Centre (PYROSEARCH). The experimental phase equilibria studies involve high-temperature equilibration, rapid quenching and direct measurement of phase compositions using electron probe X-ray microanalysis (EPMA). The thermodynamic modelling deals with the development of accurate thermodynamic database built through critical evaluation of experimental data, selection of solution models, and optimization of models parameters. The database covers the Al-Ca-Cu-Fe-Mg-O-S-Si chemical system. The gas, slag, matte, liquid and solid metal phases, spinel solid solution as well as numerous solid oxide and sulphide phases are included. The database works within the FactSage software environment. Examples of phase equilibria data and thermodynamic models of selected systems, as well as possible implementation of the research outcomes to selected copper making processes are presented.

Thermodynamic modelling of liquid slag-matte-metal equilibria applied to the simulation of the Peirce-Smith converter

Computer simulation plays an increasingly important role in improving the environmental and economic performance of pyrometallurgical extraction processes. The thermodynamic description of the chemical systems involved is at the core of such advanced simulation software. A thermodynamic database has been developed to describe the phase relations and chemical reactions in the Al—Ca—Cu—Fe—Mg—O—S—Si chemical system with support from the leading copper producers. The database contains model parameters for gas, liquid slag, liquid matte and metal, spinel and numerous solid phases. Models based on the Modified Quasichemical Formalism were used for the slag, matte and liquid metal. The internal consistency of the database provides accurate and reliable predictions outside of the usual operating conditions. The development of the database was closely integrated with the experimental studies of this chemical system. The database works in the environment of FactSage software. The application of thermodynamic modelling is illustrated by the example of the Peirce-Smith converter.