Development of a Thermodynamic Database for Copper Smelting and Converting

L'introduction de la modélisation thermodynamique dans la pratique de la production pyrométallurgique du cuivre pourrait augmenter significativement l'efficacité économique et le respect de l'environnement par l'industrie. Une base de données thermodynamiques fiable, en combinaison avec le logiciel de minimisation de l'énergie de Gibbs, est capable de prédire le bilan énergétique, la distribution des éléments, les transformations de phases au cours du procédé chimique. Mis en œuvre dans le couplage contrôle/simulation, la base de données thermodynamiques et le logiciel pourront réhausser l'automatisation du procédé à un nouveau niveau. L'objectif de cette thèse est le développement de la base de données capable de prédire les propriétés thermodynamiques et les équilibres de phases dans le système chimique de base pour la production pyrométallurgique du cuivre, à savoir le système Al–Ca–Cu–Fe–Mg–O–S–Si. Cela implique l'évaluation critique et l'optimisation thermodynamique des données expérimentales disponibles pour toutes les phases. La base de données est auto-cohérente, c'est-à-dire que les phases solides, liquides et gazeuses sont évaluées simultanément. 4 systèmes binaires, 5 systèmes ternaires, 7 systèmes quaternaires, 2 systèmes quinaires et 1 système à six composants ont été évalués ou réévalués. Le projet est réalisé en étroite collaboration avec le groupe Pyrosearch (Université de Queensland, Australie), qui a effectué des expériences cruciales. Certains des systèmes mentionnés ci-dessus ont été optimisés avec T. Hidayat. En outre, 4 systèmes ternaires et 5 systèmes quaternaires ont été optimisés par T. Hidayat en collaboration avec le présent auteur et ont été rapportés dans une autre thèse de doctorat [1]. En particulier, les phases du métal liquide et de la matte ont été décrites comme une solution unique en utilisant le Formalisme Quasichimique Modifié dans l’approximation des paires. La solution a été construite en utilisant un sous-réseau et les espèces non chargées: (CuI, CuII, FeII, FeIII, O, S). De cette façon, le modèle est capable de décrire un large écart à la stoechiométrie de la phase sulfurée en direction de l'excès de métal ou de l'excès de soufre et d'oxygène. La solubilité de l'oxygène dans la phase sulfurée est correctement décrite. Le modèle prend en compte l'existence de compositions d’ordonnancement maximal à courte distance entre premiers voisins au voisinage de Cu2O, CuO, FeO, Fe2O3, Cu2S et FeS et il prédit les changements drastiques de P(O2) et P(S2) à ces compositions. Il évalue précisément les solubilités du soufre et de l'oxygène dans la zone métallique de la solution. Il peut être utilisé pour prédire les équilibres solides-liquides dans les systèmes chimiques contenant les phases d'oxyde et de sulfure à des pressions partielles d'oxygène faibles et élevées. La solution de laitier est modélisée à l’aide du Formalisme Quasichimique Modifié dans l’approximation des quadruplets. Les cations sont chargés et placés sur un sous-réseau séparé de celui des anions : (Al3+; Ca2+, Cu1+, Fe2+, Fe3+, Mg2+, Si+4)(O2-, S2-). Ce modèle tient compte de l'ordre à courte distance entre les cations seconds voisins {cations basiques (Ca2+, Fe2+, etc.) et acides (Si4+)}, tandis que l'ordre à courte distance entre les premiers voisins est supposé être complet. Les bases de données pour les sous-systèmes d'oxydes optimisées auparavant, ré-optimisées et récemment obtenues ont été combinées et complétées avec les composants à base de soufre. La base de données de laitier résultante est capable de décrire les relations de phases dans les systèmes d'oxydes, ainsi que les capacités du soufre. L'effet du soufre sur la solubilité du cuivre dans les scories est démontré et modélisé. Ceci est d'une importance primordiale pour l'industrie qui s’efforce d’éviter les pertes de cuivre dans les scories. L'effet du calcium sur la solubilité du cuivre et du soufre dans le laitier de fayalite est modélisé quantitativement pour la première fois. Le cuivre et le calcium sont ajoutés dans la base de données de la spinelle d'une manière thermodynamiquement compatible. La base de données de la spinelle peut être utilisée pour estimer l'usure des matériaux réfractaires et pour surveiller les conditions permettant d’éviter la précipitation de spinelle ; cette dernière pouvant provoquer l'occlusion des réacteurs. Cette base de données est capable de prédire la distribution des cations entre les sous-réseaux ; ce qui est important pour les applications électroniques. La capacité prédictive de la base de données est testée au cours de la simulation d'un four de fusion. Les résultats des calculs sont comparés aux données d’usine. Un très bon accord est démontré lors de l'estimation des bilans d’énergie et de matière et lors de la prédiction des distributions d'éléments entre les sorties du four. Ainsi, la base de données thermodynamiques pour les applications dans la production pyrométallurgique du cuivre que nous avons développée dans le cadre de ce projet est la plus précise et la plus complète au monde. Elle est destinée à être utilisée avec le logiciel FactSageTM. En utilisant les méthodes affinées dans cette étude, d'autres éléments peuvent être facilement ajoutés à la base de données. Les travaux se poursuivent actuellement par l'ajout de Co, Pb, Ni et Zn. ---------- Introduction of thermodynamic modeling into the practice of the pyrometallurgical copper production may significantly increase the economic efficiency and environmental friendliness of the industry. A reliable thermodynamic database in combination with the Gibbs energy minimizing software is able to predict the energy balance, distribution of elements, phase transformations during the chemical process. Implemented in the control/simulation package, such thermodynamic database and software will be able to raise the process automation to a new level. The goal of this thesis is the development of the database able to predict the thermodynamic properties and phase equilibria in the basic chemical system for the pyrometallurgical copper production, which is the Al–Ca–Cu–Fe–Mg–O–S–Si system. This involves the critical evaluation and thermodynamic optimization of available experimental data for all phases. The database is self-consistent, i.e. solid, liquid and gas phases are assessed simultaneously. 4 binary, 5 ternary, 7 quaternary, 2 quinary and 1 six-component system were evaluated or re-evaluated. The project is performed in close collaboration with the Pyrosearch group (University of Queensland, Australia), who performed some crucial experiments. Some of the above-mentioned systems were optimized together with T. Hidayat. In addition, 4 ternary and 5 quaternary systems were optimized by T. Hidayat in co-operation with the present author and reported in another Ph.D. thesis [1]. In particular, liquid metal and matte phases were described as one solution using the Modified Quasichemical Formalism in the pair approximation. The solution was built using one sublattice and uncharged species: (CuI, CuII, FeII, FeIII, O, S). In this way, the model is able to describe wide deviations from stoichiometry in the sulfide phase towards excess metal or excess sulfur and oxygen. The oxygen solubility in the sulfide phase is correctly described. The model takes into account the existence of compositions of maximum first nearest neighbor short-range ordering near Cu2O, CuO, FeO, Fe2O3, Cu2S and FeS and predicts the drastic changes in P(O2) and P(S2) at these compositions. It accurately estimates the solubilities of sulfur and oxygen in metal region of the solution. It can be used to predict solid-liquid equilibria in chemical systems containing sulfide and oxide phases at low and high oxygen partial pressures. The slag solution was modeled within the Quasichemical Formalism in quadruplet approximation. Cations are charged and placed in a separate sublattice from anions: (Al3+, Ca2+, Cu1+, Fe2+, Fe3+, Mg2+, Si+4)(O2-, S2-). The model of this type takes into account the second nearest neighbor short-range ordering between basic (Ca2+, Fe2+, etc.) and acidic (Si4+) cations, while the first nearest neighbor short range ordering between metals and non-metals is assumed to be complete. Previously optimized, re-optimized and newly obtained databases for oxide subsystems were combined together and complemented with sulfide components. The resulting slag database is able to describe phase relations in oxide systems, as well as sulfide capacities. The effect of sulfur on the solubility of copper in slag is demonstrated and modeled. This is of primary importance for the industry which is trying to avoid copper losses into slag. The effect of calcium on the solubility of copper and sulfur in fayalite slag is modeled quantitatively for the first time. Copper and calcium were added into the spinel database in a thermodynamically consistent way. The spinel database may be used to estimate the wearing of refractory materials and to monitor the conditions to prevent the spinel precipitation, which might cause occlusions of reactors. It is able to predict cation distribution between sublattices, which is important for electronic applications. The predictive ability of the database was tested during the simulation of a smelting furnace. The calculation results are compared with the plant data. Very good agreement is demonstrated in the estimation of energy and mass balance and in the prediction of element distributions between outputs of the furnace. Thus, the thermodynamic database for the applications in the pyrometallurgical production of copper, developed during the course of this project, is the most accurate and complete in the world. It is intended to be used with the FactSageTM software. Using the methods, refined in this study, more elements can be easily added to the database. The work currently continues on the addition of Co, Pb, Ni and Zn to the database. [1] T. Hidayat, "Equilibria Study of Complex Silicate-based Slag in the Copper Production," Ph.D. thesis, The University of Queensland, 2013

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

Critical assessment and thermodynamic modeling of the Cu-As system

Thermodynamic assessment and modeling of the Cu-As system are presented. The experimental dataset includes phase equilibrium data, activity measurements, heat contents, enthalpies of formation and mixing. The liquid phase and two non-stoichiometric copper arsenide solid solutions are developed within the framework of the Modified Quasichemical Model (MQM) in pair approximation. It is demonstrated that the unconventional choice of model for solid solution phases is beneficial for this particular system. The resulting set of model parameters will be a part of a large multicomponent thermodynamic database. It is aimed for predictions of phase equilibria, heat balance and distribution of elements in arsenic-containing chemical systems in pyrometallurgical copper and lead industrial operations

Thermodynamic assessment of the CaO–Cu2O–FeO–Fe2O3 system

Thermodynamic assessment of the CaO–CuO–FeO–FeO system is presented. Effects of temperature and P(O) on the phase equilibria involving slag, solubility of copper and the Fe/Fe ratio in slag have been modeled using available experimental data. Subsolidus phase equilibria and concentration of iron in liquid copper were evaluated as well. Different ways of representing phase equilibria in a quaternary system are illustrated. The slag model, [Ca, Cu, Fe, Fe][O], was developed using the Modified Quasichemical Model (MQM). Liquid metal phase is modeled using the MQM, but as a separate solution, (Cu, Fe, O). Spinel phase is modeled using the Compound Energy Formalism (CEF) and takes into account the solubility of copper and calcium. A thermodynamic database produced in the present study can be used for predictions in pyrometallurgical processing of copper involving calcium ferrite slags. The database is internally consistent with the binary and ternary sub-systems published earlier, as well as with higher-order systems. It works in the environment of FactSage, ChemApp, ChemSheet and SimuSage software packages

Thermodynamic modeling of the Pb-S and Cu-Pb-S systems with focus on lead refining conditions

Thermodynamic modeling of the Pb-S and Cu-Pb-S systems is presented. All available experimental data in these systems are collected, assessed and used to optimize the model parameters. For the liquid phase, a solution (Cu, Pb, S) is developed using the modified quasichemical model in pair approximation. Liquid copper, liquid lead metal, as well as matte phases are described using single solution with miscibility gaps. Earlier thermodynamic assessments available in the literature did not include all the data on the solubility of Cu and S in liquid Pb at low temperatures, 900\ua0°C (1123\ua0K), a significant discrepancy among different sets of literature data and existing thermodynamic assessments is revealed. Preliminary experiments are performed with the goal to understand the nature of the problem and to develop the methodology based on high-temperature equilibration, rapid quenching and electron probe x-ray microanalysis. The results of this study help to select accurate literature results in the optimization of model parameters. The resulting database is applicable to calculate slag/matte/metal distribution of lead in copper smelting and converting, as well as for predictions in the lead smelting and fire refining

Thermodynamic assessment and database for the Cu-Fe-O-S system

The previously obtained thermodynamic databases for the Cu–Fe–S, Cu–Fe–O, Fe–O–S and Cu–O–S ternary systems have been combined and used to predict thermodynamic equilibria in the quaternary Cu–Fe–O–S system. The available experimental data were compared with model predictions. Minor modifications of model parameters were required to better describe the experimental points in the quaternary system; the effect of these changes was verified in the ternary subsystems. The procedure was developed to calculate the isothermal sections of the phase diagram of the quaternary system inside the tetrahedron. The liquid phase over the whole composition range from metallic liquid to sulfide melt to oxide melt has been described by a single model developed within the framework of the quasichemical formalism. The obtained self-consistent set of model parameters can be used as a basis for the development of a thermodynamic database for simulation of copper smelting and converting

Recent advances in research for non-ferrous smelting and recycling

As metal smelting and recycling pyrometallurgical systems become increasingly more complex the need for advanced experimental and thermodynamic modelling techniques that accurately describe the chemistries of these systems are becoming more widely appreciated. These techniques can be used to predict the optimum process conditions in terms of, for example, charge composition, temperature and oxygen partial pressure, and the partitioning of elements between phases and different process streams. To provide fundamental information on these multi-component, multi-phase equilibria it has been necessary to develop new research methodologies and techniques. An approach that has proven to be particularly successful and useful for non-ferrous systems has been the integrated research program undertaken at PYROSEARCH. The experimental studies involve high temperature equilibration in controlled gas atmospheres, rapid quenching and direct measurement of compositions of equilibrium phases with electron probe X-ray microanalysis (EPMA). The thermodynamic modelling, undertaken using the computer package FactSage with the quasi-chemical model for the liquid slag phase, is closely integrated with the parallel experimental research. Experiments are planned to provide specific data for thermodynamic model development as well as for pseudo-ternary liquidus diagrams, which can be used directly by process operators. Thermodynamic assessments are used to identify priorities for experiments. Experimental and modelling studies are combined into an integrated research program contributing to, and enhancing outcomes of, each other and of the overall program. Importantly, these novel approaches have enabled measurements to be made in systems that could not previously be characterised, for example, due to uncontrollable reactions with container materials or changes in bulk composition due to vapour phase reactions. It is now possible to obtain fundamental phase equilibria data on liquidus, solid and liquid solutions in not only low order systems but also for the more complex multi-component multi-phase systems encountered in industrial practice. The new data and models can now be applied to provide a clearer understanding of process chemistry and how this knowledge can be used to assist in improvements of the processes. The approach is illustrated in the paper with several examples of applications to non-ferrous pyrometallurgical systems, including copper, lead and tin

Critical thermodynamic re-evaluation and re-optimization of the CaO–FeO–Fe2O3–SiO2 system

Comprehensive literature review, critical re-assessment and thermodynamic re-optimization of phase diagrams and thermodynamic properties of all phases have been carried out for the CaO–FeO–FeO–SiO system. Thermodynamic assessments of this system were previously published, however some of them were incomplete or described only limited range of compositions. In addition, more recent important experimental data have been available after previous assessments. The Modified Quasichemical model is used to describe the Gibbs energy of the liquid slag. The monoxide, wollastonite, α-CaSiO and α’-CaSiO solid solutions are described using the random mixing Bragg-Williams model. Spinel, olivine, pyroxene and melilite solid solutions are modelled using sublattice model based on the Compound Energy Formalism. A set of optimized parameters for the thermodynamic models has been obtained which reproduces all available experimental data within the experimental uncertainties from sub-solidus to above the liquidus temperatures at all compositions and atmosphere conditions