Browsing by Department "Metallurgy (MTG)"
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Item Advances in Modeling of Steel Solidification with IDS(IOP Publishing Ltd., 2019-06-17) Miettinen, J.; Louhenkilpi, S.; Visuri, V. V.; Fabritius, T.; University of Oulu; Metallurgy (MTG); Department of Chemical and Metallurgical EngineeringIDS (Inter-Dendritic Solidification) is a thermodynamic-kinetic software package that simulates phase changes, compound formation/dissolution, and solute distribution during solidification of steels as well as during their cooling/heating process after solidification. The software package also simulates solid-state phase transformations related to the austenite decomposition process at temperatures below 900/600 °C, and calculates thermophysical material properties from the liquid state down to room temperature. These data are needed in other models, such as heat transfer and thermal stress models, whose reliability heavily depends on the input data. The software package also features a database for thermodynamic, kinetic and microstructure data, as well as for several material properties. Owing to the short calculation times, the IDS tool is suitable for online applications. This paper presents IDS and its modules with the latest developments and validations, along with examples of modeling results.Item Behavior of Battery Metals Lithium, Cobalt, Manganese and Lanthanum in Black Copper Smelting(MDPI AG, 2020-03-02) Danczak, Anna; Klemettinen, Lassi; Kurhila, Matti; Taskinen, Pekka; Lindberg, Daniel; Jokilaakso, Ari; Metallurgy (MTG); School services, CHEM; Geological Survey of Finland; Department of Chemical and Metallurgical EngineeringRecycling of metals from different waste streams must be increased in the near future for securing the availability of metals that are critical for high-tech applications, such as batteries for e-mobility. Black copper smelting is a flexible recycling route for many different types of scrap, including Waste Electrical and Electronic Equipment (WEEE) and some end-of-life energy storage materials. Fundamental thermodynamic data about the behavior of battery metals and the effect of slag additives is required for providing data necessary for process development, control, and optimization. The goal of our study is to investigate the suitability of black copper smelting process for recycling of battery metals lithium, cobalt, manganese, and lanthanum. The experiments were performed alumina crucibles at 1300 °C, in oxygen partial pressure range of 10−11‒10−8 atm. The slags studied contained 0 to 6 wt% of MgO. Electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) techniques were utilized for phase composition quantifications. The results reveal that most cobalt can be recovered into the copper alloy in extremely reducing process conditions, whereas lithium, manganese, and lanthanum deport predominantly in the slag at all investigated oxygen partial pressures.Item Behavior of Nickel as a Trace Element and Time(2018) Klemettinen, Lassi; Avarmaa, Katri; Taskinen, Pekka; Jokilaakso, Ari; Department of Chemical and Metallurgical Engineering; Metallurgical Thermodynamics and Modelling; Metallurgy (MTG)For better understanding and maximal value utilization of the WEEE smelting process, the behavior and distribution of different trace elements must be known. In this study, the behavior of nickel as a trace element was studied in an equilibrium system with metallic copper—spinel saturated iron silicate slag (with 3 wt-% K2O)—iron aluminous spinel—gas. The experiments were conducted in alumina crucibles at 1300 °C, in oxygen pressure range of 10−10–10−5 atm. A time series of 15–60 min experiments was also conducted for investigating the formation rate of the primary spinel phase in the system. The results show that the distribution coefficient of nickel between metallic copper and liquid slag changes from approximately 70 to 0.4 along the increasing oxygen pressure range. In addition, a significant part of the nickel deports into the spinel phase. The spinel formation was investigated based on composition analysis results and visual observations from SEM-images.Item The CFD Modeling of Multiphase Flow in an SKS Furnace: The Effect of Tuyere Diameter and Bath Depth(SPRINGER, 2022-04) Song, Kezhou; Jokilaakso, Ari; Department of Chemical and Metallurgical Engineering; Metallurgy (MTG)CFD simulation using a multi-fluid VOF model on scaled-down SKS furnace multiphase flow was conducted, targeting the agitation performance under conditions of different tuyere diameters and bath depths, at a constant total gas volumetric flow rate. The results indicate that an increased bath depth contributes to the lateral movements of the matte and air phased, significantly promoting the agitation at the far side of the plumes. The characteristic of a deep bath allows larger tuyere diameters operated at a lower gas injection speed, to achieve comparatively smaller low velocity regions and dead zones. In addition, the wall shear stress was found to correlate with the distribution of low-velocity regions. Since the selections of tuyere diameter and bath depth are of major importance in the optimizing of flow fields, the results from this simulation offer good references for the future operation and design of SKS furnaces and other similar industrial vessels.Item Cleaner Recycling of Spent Lead-Acid Battery Paste and Co-Treatment of Pyrite Cinder via a Reductive Sulfur-Fixing Method for Valuable Metal Recovery and Sulfur Conservation(Multidisciplinary Digital Publishing Institute (MDPI), 2019-08) Li, Yun; Yang, Shenghai; Taskinen, Pekka; Chen, Yongming; Tang, Chaobo; Jokilaakso, Ari; Central South University; Department of Chemical and Metallurgical Engineering; Metallurgy (MTG)This study proposes a cleaner lead-acid battery (LAB) paste and pyrite cinder (PyC) recycling method without excessive generation of SO2. PyCs were employed as sulfur-fixing reagents to conserve sulfur as condensed sulfides, which prevented SO2 emissions. In this work, the phase transformation mechanisms in a PbSO4-Na2CO3-Fe3O4-C reaction system were studied in detail. Furthermore, the co-treatment of spent LAB and PyCs was conducted to determine the optimal recycling conditions and to detect the influences of different processing parameters on lead recovery and sulfur fixation. In addition, a bench-scale experiment was carried out to confirm the feasibility and reliability of this novel process. The results reveal that the products were separated into three distinct layers: slag, ferrous matte, and crude lead. 98.3% of lead and 99% of silver in the feed materials were directly enriched in crude lead. Crude lead with purity of more than 98 wt.% (weight percent) was obtained by a one-step extraction. Lead contents in the produced matte and slag were below 2.7 wt.% and 0.6 wt.%, respectively. At the same time, 99.2% total sulfur was fixed and recovered.Item Dynamic modelling of molten slag-matte interactions in an industrial flash smelting furnace settler(2018) Jokilaakso, Ari; Khan, Nadir; Metallurgy (MTG); School services, CHEM; Department of Chemical and Metallurgical EngineeringDepleting copper resources and advancing technologies have challenged industries to develop more viable, adaptable and cost efficient processes using also secondary raw materials in copper production. This study is targeting to that goal by dynamic modelling of flow and heat transfer coupled with chemical kinetics in an industrial scale flash smelting furnace settler using commercial CFD software ANSYS Fluent. First, different physical phenomena occurring inside the settler, for example, settling and separation of the matte/slag phases, and heat transfer between slag/matte phases and settler walls are studied. Secondly, reaction kinetics between matte and slag, and between slag/matte and settler walls, and impurity element distribution will be studied. This would also include phase changes phenomena due to these reactions and the flow of the reaction gases inside the settler. Settling of polydispersed droplets, their coagulation, breakage, and WEEE particle behavior are further targets of the modelling work.Item The efficiency of scrap Cu and Al current collector materials as reductants in LIB waste leaching(Elsevier Science B.V., 2021-08) Chernyaev, Alexander; Partinen, Jere; Klemettinen, Lassi; Wilson, Benjamin P.; Jokilaakso, Ari; Lundström, Mari; Department of Chemical and Metallurgical Engineering; Metallurgy (MTG); Hydrometallurgy and CorrosionThis current study addresses the role of copper and aluminum - typical major components of current collector scrap from battery manufacturing plants - in the leaching of pre-treated LiCoO2-rich battery waste concentrate at industrially relevant process conditions (T = 60 °C, [H2SO4] = 2 M, S/L = 200 g/L). An empirical model has been constructed which demonstrates that the effects of both copper and aluminum are significant. Both elements have independent and linear impacts on cobalt extraction and acid consumption. The model predicts that either 11 g of copper (0.75 Cu/Co, mol/mol), 4.8 g of aluminum (0.7 Al/Co, mol/mol) or a combination of both are required for full cobalt extraction from 100 g of sieved industrial battery waste concentrate. Aluminum was shown to influence cobalt leaching although it was less effective (47%) when compared to copper (66%) in terms of current efficiency due to associated side reactions, such as excess H2 formation. Aluminum has several possible reaction routes for LiCoO2 reduction; in parallel or in series via H2 formation, Cu2+ cementation and/or Fe3+ reduction, whereas copper acts solely through Fe3+ reduction. These results indicate that by using copper scrap, in preference to the more typical hydrogen peroxide, the CO2 footprint of the battery leaching stage could be decreased by at least 500 kg of CO2 per ton of recycled cobalt. In contrast, the use of aluminum, although promising, is less attractive due to the challenges related to its removal during subsequent solution purification.Item Experimental Investigation of Pyrometallurgical Treatment of Zinc Residue(2018) Rämä, Minna; Jokilaakso, Ari; Klemettinen, Lassi; Salminen, Justin; Taskinen, Pekka; Department of Chemical and Metallurgical Engineering; Metallurgy (MTG); Davis, Boyd; Moats, M; Wang, SIron containing leach residues like jarosite and goethite from electrolytic zinc production contain many valuable metals and harmful substances. These metals and substances should be removed in order to obtain an acceptable, stable and reusable product, and maximize economic feasibility as well as minimize environmental footprint. In this work, the processing of jarosite leach residue was studied in laboratory scale experiments under oxidizing and reducing conditions at high temperatures. First, the pretreated material was melted and oxidized to produce a melt of metal oxides. Second, the oxide melt was reduced in CO –CO2 atmosphere. Target after the reduction step was to obtain a clean slag and a liquid metal or speiss phase that collects the valuable metals , such as silver . The kinetics of the thermal processing were studied for determining optimal times and conditions for the aforementioned process steps. The preliminary results show that the process is thermodynamically feasible, and the desired phases can be obtained in the experimental conditions investigated.Item Iron activity measurements and spinel-slag equilibria in alumina-bearing iron silicate slags(Elsevier Science, 2021-02-25) Klemettinen, Lassi; Avarmaa, Katri; Jokilaakso, Ari; Taskinen, Pekka; Department of Chemical and Metallurgical Engineering; Metallurgy (MTG)Alumina is a common substance deporting in copper smelting slags when various secondary copper fractions, e.g. e-scrap or WEEE, are used as feedstock as such or along with primary sulphide concentrates. Properties of iron-silicate slags at high alumina concentrations, in the iron-alumina spinel saturation, have been studied at 1300 °C by a high temperature equilibration-quenching method combined with EPMA (electron probe microanalysis) phase composition data from the polished sections. The equilibrations were performed in fixed oxygen activity with platinum or palladium powder, which dissolved iron from the slag and generated a heterogeneous equilibrium system, characterised by the general equilibrium criterium in isothermal and isobaric conditions, as. μalloy(Fe) = μslag(Fe) = μspinel(Fe). This criterium was used for measuring experimentally iron activities of molten silicate slags. The locations of the spinel-liquid slag tie-lines were also determined in the oxygen partial pressure range of 10−6–10−10 atm. A comparison with the recent critical thermodynamic assessments of the Fe–O–Al2O3 system indicates that the iron-alumina spinel-corundum phase boundary in silica-containing systems as a function of oxygen partial pressure is too steep and thus the assessed databases do not match with the experimental data of this study. The liquid slag domain from silica to iron oxide saturation is also smaller than expected earlier, as the spinel primary phase boundary locates at higher silica concentrations than e.g. obtained in the assessments of the Mtox database.Item A New Pyrometallurgical Recycling Technique for Lead Battery Paste without SO2 Generation(2018) Li, Yun; Chen, Yongming; Tang, Chaobo; Yang, Shenghai; Klemettinen, Lassi; Rämä, Minna; Wan, Xingbang; Jokilaakso, Ari; Department of Chemical and Metallurgical Engineering; Central South University; Metallurgy (MTG)An innovative lead recycling process from scrap lead-acid battery paste is presented. The novelty in the process is avoiding SO2 generation and emission by using reductive sulfur-fixing technique. Iron-bearing secondary wastes produced from metallurgical industry were utilized as sulfur-fixing agent to capture sulfur in the form of FeS (s) instead of generation of SO2 (g). Molten Na2CO3 salt was added to the smelting system to speed the reactions and improve valuable metals’ recovery and sulfur-fixation efficiency. Furthermore, this process can simultaneously co-treat various lead and iron-bearing wastes. At the same time, some precious metals, such as Au and Ag, contained in iron-bearing wastes can be recovered. The feasibility and reliability of this process was investigated thermodynamically and experimentally with the help of HSC 9.0 database and XRD and SEM-EDS analysis. A possible reaction mechanism and path in PbSO4-Fe2O3-Na2CO3-C smelting system was also clarified.Item Novel method to study volatile trace elements in electric furnace nickel slag cleaning(2019) Hellsten, Niko; Taskinen, Pekka; Jokilaakso, Ari; Latostenmaa, Petri; Department of Chemistry and Materials Science; Department of Chemical and Metallurgical Engineering; Metallurgy (MTG); Boliden Harjavalta OyExperimental studies of the equilibrium behavior of easily vaporizing elements, such as As, Pb and Sb, at atmospheric pressures and in pyrometallurgical process temperatures is challenging. Previ-ously, systems containing volatile elements have been studied using conventional methods with closed vessels or by adding sufficient amounts of the volatile materials to the starting mixtures to retain them in the system after experiment. However, some of these previously used techniques often lack sufficient accuracy and involve concentration gradients typical to non-equilibrium sys-tems. In addition, external control of the gas atmosphere is difficult, which limits the use of these techniques. Thus, innovative experimental techniques to study the equilibria in systems involving volatile elements are needed.Item Optimization of the CCT Curves for Steels Containing Al, Cu and B(SPRINGER, 2021-06) Miettinen, Jyrki; Koskenniska, Sami; Somani, Mahesh; Louhenkilpi, Seppo; Pohjonen, Aarne; Larkiola, Jari; Kömi, Jukka; University of Oulu; Metallurgy (MTG); Department of Chemical and Metallurgical EngineeringNew continuous cooling transformation (CCT) equations have been optimized to calculate the start temperatures and critical cooling rates of phase formations during austenite decomposition in low-alloyed steels. Experimental CCT data from the literature were used for applying the recently developed method of calculating the grain boundary soluble compositions of the steels for optimization. These compositions, which are influenced by solute microsegregation and precipitation depending on the heating/cooling/holding process, are expected to control the start of the austenite decomposition, if initiated at the grain boundaries. The current optimization was carried out rigorously for an extended set of steels than used previously, besides including three new solute elements, Al, Cu and B, in the CCT-equations. The validity of the equations was, therefore, boosted not only due to the inclusion of new elements, but also due to the addition of more low-alloyed steels in the optimization. The final optimization was made with a mini-tab tool, which discarded statistically insignificant parameters from the equations and made them prudently safer to use. Using a thermodynamic-kinetic software, IDS, the new equations were further validated using new experimental CCT data measured in this study. The agreement is good both for the phase transformation start temperatures as well as the final phase fractions. In addition, IDS simulations were carried out to construct the CCT diagrams and the final phase fraction diagrams for 17 steels and two cast irons, in order to outline the influence of solute elements on the calculations and their relationship with literature recommendations.Item The Oxidation of Copper in Air at Temperatures up to 100 °C(MDPI AG, 2021-10-25) Aromaa, Jari; Kekkonen, Marko; Mousapour, Mehrdad; Jokilaakso, Ari; Lundström, Mari; Department of Chemical and Metallurgical Engineering; Advanced Manufacturing and Materials; Metallurgy (MTG); Hydrometallurgy and Corrosion; Department of Mechanical EngineeringThe aim of this study was to investigate the oxidation kinetics of copper at low temperatures (60 °C to 100 °C) in air by isothermal thermogravimetric analysis (TGA) and quartz crystal microbalance (QCM). The weight change in thermogravimetric tests showed periodic weight increase and decrease. In thermogravimetric tests the mass of the copper sample increased until the oxidation gradually slowed down and finally started to decrease due to cracking and spalling of the oxide formed on the surface. In QCM tests using electrodeposited copper film, the weight change was rapid at the beginning but slowed to a linear relationship after few minutes. Temperature and exposure time appeared to have a large effect on oxide film thickness and composition. With QCM, oxidation at 60–80 °C produced less than 40 nm films in 10 days. Oxidation at 90–100 °C produced 40 nm thick films in a day and over 100 nm films in a week. Although SEM-EDS analyses in TGA tests indicated that oxygen was adsorbed on the copper surface, neither XRD patterns nor Raman spectroscopy measurements showed any trace of Cu2O or CuO formation on the copper surface. Electrochemical reduction analysis of oxidized massive copper samples indicated that the oxide film is mostly Cu2O, and CuO develops only after several days at 90–100 °C.Item Phase equilibria and liquid phase behavior of the K2O-CaO-SiO2 system for entrained flow biomass gasification(Elsevier BV, 2020-04-01) Santoso, Imam; Taskinen, Pekka; Jokilaakso, Ari; Paek, Min; Lindberg, Daniel; Department of Chemical and Metallurgical Engineering; Metallurgy (MTG)Experimental data of solid-liquid phase equilibria in the K2O-CaO-SiO2 systems vital for many technologies and industrial applications are very limited and even not available at some primary phase fields. In the present study, by using Equilibration-Quenching-Phase compositional analysis (EPMA/EDS) method, liquidus compositions in equilibrium with pure solid SiO2, CaO·SiO2, 3CaO·2SiO2, 2CaO·SiO2, K2O·6CaO·4SiO2 and K2O·2CaO·2SiO2 compounds and 2CaO·SiO2 solid solution were measured. By knowing the evaporation behavior of K2O during the equilibration process, specific initial mixtures could be selected to obtain liquidus data for targeted final equilibrium assemblages. EPMA and EDS analysis results were compared. The experimental data obtained in the present study were discussed and compared with the results from previous experimental investigations and the assessed ternary phase diagrams. Some novel experimental data of the liquid at single and double solid phase saturations were obtained in the present studyand they can be used to correct and support the predictions and thermodynamic assessments of the K2O-CaO-SiO2 system. Present investigation reports liquidus projections and detailed phase relations among the phases in isothermal sections at 1000, 1100, 1200, 1300 and 1400 °C. Viscosity calculations of the liquid at different compositions between 1000 and 1400 °C also have been made. A combination of phase equilibria study and the viscosity predictions in the present investigation provides suitable temperature and ash composition regions for optimal flow properties of the slag in entrained flow biomass combustion or gasification processes.Item Reaction Behavior of Na2SO4-Containing Copper Matte Powders in a Simulated Flash Converting Process(SPRINGER, 2021-10) Yu, Feng; Xia, Longgong; Zhu, Yinbin; Jokilaakso, Ari; Liu, Zhihong; Central South University; Tongling Nonferrous Metals Group Holding Co Ltd.; Metallurgy (MTG); Department of Chemical and Metallurgical EngineeringSodium sulfate accumulation in the water system is a common problem in the production of primary metals from sulfide minerals. In flash smelting-flash converting copper smelters, when molten copper matte quenched in industrial water to produce matte granules, Na2SO4 precipitated and entered the system, which had negative influence on the matte converting process. The reaction behaviors of copper matte powder containing Na2SO4 have been studied through thermodynamic calculation and single-particle experiments. Calculated results showed that a liquid sulfate phase, Na2S containing copper matte, and Cu-Na alloy may form in the processing conditions of the converting process. The influence of the Na2SO4 dosage, fluxing conditions, and processing temperature has been systematically studied, and the results obtained showed that: (1); Na2SO4 physically precipitated on matte particles, and the Cu-Na alloy phase was found within copper phase in reacted particles; (2); Na2SO4 contamination hindered oxygen transfer by forming a low melting sulfate phase, and the de-sulfuration rate of matte powder changed dramatically along with the variation in Na2SO4 amount; (3); CaO flux was able to promote the converting reactions and Na2SO4 transformation; (4); Na2SO4 melt and formed a sulphate layer on matte particles at 1000 degrees C, Cu-Na alloy phase was found in samples collected at 1200 degrees C, and Cu-Na-O phase was detected in blister copper at 1600 degrees C.Item Recycling of tellurium via copper smelting processes(SPRINGER, 2020-03) Klemettinen, Lassi; Avarmaa, Katri; Sukhomlinov, Dmitry; O'Brien, Hugh; Taskinen, Pekka; Jokilaakso, Ari; Department of Chemical and Metallurgical Engineering; Metallurgy (MTG); Geological Survey of FinlandThe modern world continuously demands more raw materials for manufacturing all kinds of products. Nowadays, the lifetime of a single product can be very short, as is the case with electronic appliances. Waste electrical and electronic equipment (WEEE) is one of the fastest growing waste categories, and one of the most promising recycling routes for WEEE is to use it as a feed material in pyrometallurgical copper smelting. This article presents new experimental observations regarding the behavior of tellurium in secondary copper smelting process, and compares the results to primary smelting experiments. In secondary smelting conditions, most of tellurium distributed into the copper phase, and the distribution coefficient between copper and slag decreased with increasing oxygen partial pressure. In the primary smelting experiments, most of tellurium was vaporized into flue dusts, and the distribution coefficient between copper matte and slag increased with increasing oxygen pressure, i.e. increasing matte grade.Item Review on interaction between slag, steel and inclusions in secondary steelmaking(2018) Holappa, Lauri; Nurmi, Sonja; Jokilaakso, Ari; Department of Chemical and Metallurgical Engineering; Metallurgy (MTG)The refining function of slags in ladle metallurgy comprises of desulphurization and capture of inclusions, which are removed from the steel melt in the course of deoxidation procedure. In that task, the interaction between the two phases, slag and steel is active and highly beneficial. Further, the slag has a passive, shrouding role when it protects steel from atmospheric oxidation and heat losses. In some cases, slag can even have negative influences as a reoxidation source and eventual origin of harmful inclusions in steel. Conventionally, inclusions in steel are understood as deoxidation products, remained in the steel after the deoxidation process. These, “intrinsic” inclusions are then related to the steel composition i.e. determined by the deoxidizing components in steel, generally Al but even Si, Mn and Ca. However, in intensive ladle treatment the role of the top slag is not only the receiver of inclusions from the steel but pronounced chemical interaction between the liquid slag and metal can take place. Consequently, a component with low activity in the slag e.g. SiO2 can intensify deoxidation by silicon. By contrast, CaO has a high activity in basic ladle slags and it can interact with steel and bring CaO into inclusions. As a consequence, the type of inclusions can remarkably change. The current paper examines the fundamentals of interaction phenomena between slag, steel and inclusions via thermodynamic calculations, experimental results from steel industry, and observations on related research in the literature.Item A Study of Selenium and Tellurium Distribution Behavior, Taking the Copper Matte Flash Converting Process as the Background(SPRINGER, 2021-02) Yu, Feng; Liu, Zhihong; Ye, Fengchun; Xia, Longgong; Jokilaakso, Ari; Central South University; Metallurgy (MTG); Department of Chemical and Metallurgical EngineeringSingle particle experiments were carried out in the present study. An industrial copper matte powder, containing 68.04 wt.% Cu, 0.50 wt.% Se and 0.08 wt.% Te was taken as the starting material. Se and Te phase assemblies and distribution behaviors were systematically investigated in the air atmosphere. It was found that Se reported to blister copper, matte, and oxide phase, whilst Te will enrich in oxide phases, including phases in the Fe-Si-Te-O, Ca-Fe-Te-O, and Ca-Te-O-(S) systems. As the temperature increases, the selenium and tellurium content in the copper and matte phases decreases. The introduction of CaO flux, and typical impurities of Pb and Si, had significant influence on Se and Te distribution. The results revealed that CaO addition and Si impurity accelerated the removal of Se and Te from the copper and matte phases, but Pb impurity increased Se and Te in Cu-rich phases.Item Thermal Analysis and Optimization of the Phase Diagram of the Cu-Ag Sulfide System(MDPI AG, 2022-01-14) Tesfaye, Fiseha; Lindberg, Daniel; Sukhomlinov, Dmitry; Taskinen, Pekka; Hupa, Leena; Åbo Akademi University; Department of Chemical and Metallurgical Engineering; Metallurgy (MTG)Thermal stabilities of selected ternary phases of industrial interest in the Ag-Cu-S system have been studied by the calorimetric and electromotive force techniques. The ternary compounds Ag1.2 Cu0.8 S (mineral mackinstryite) and AgCuS (mineral stromeyerite) were equilibrated through high-temperature reaction of the pure Cu2 S and Ag2 S in an inert atmosphere. The synthesized single solid sample constituting the two ternary phases was ground into fine powders and lightly pressed into pellets before calorimetric measurements. An electrochemical cell incorporating the two equilibrated phase and additional CuS as a cathode material was employed. The measurement results obtained with both techniques were analyzed and thermodynamic properties in the system have been determined and compared with the available literature values. Enthalpy of fusion data of the Ag-richer solid solution (Ag,Cu)2 S have also been determined directly from the experimental data for the first time. The thermodynamic quantities determined in this work can be used to calculate thermal energy of processes involving the Ag-Cu-S-ternary phases. By applying the obtained results and the critically evaluated literature data, we have developed a thermodynamic database. The self-developed database was combined with the latest pure substances database of the FactSage software package to model the phase diagram of the Ag2 S-Cu2 S system.Item Thermodynamic assessment of ZnO-SiO2 system(Nonferrous Metals Society of China, 2018-09-01) ISOMÄKI, Iikka; ZHANG, Rui; XIA, Long gong; HELLSTEN, Niko; TASKINEN, Pekka A.; KTH Royal Institute of Technology; Central South University; Metallurgy (MTG); Department of Chemical and Metallurgical EngineeringZnO-containing slags are common in pyrometallurgical processing of the base metals and steel. This caused the interest to the thermodynamics of the ZnO-SiO2 system. A complete literature survey, critical evaluation of the available experimental data and a thermodynamic optimization of the phase equilibria and thermodynamic properties of the system ZnO-SiO2 at 1.013×105 Pa are presented. The molten oxide was described as an associate solution. The properties of liquid were reassessed and enthalpy term of the Gibbs energy of solid Zn2SiO4 was re-fitted to be compatible with the new data in the willemite primary phase field. The thermodynamic data set agrees well with the recent experimental observations. It can be used for predicting, e.g., the thermodynamic properties and the domains of the phase diagram, like critical point of the liquid miscibility gap, with a better accuracy than using the previous assessments. A set of optimized model parameters were obtained, reproducing the reliable thermodynamic and phase equilibrium data within their experimental errors from 298 K to liquidus temperatures, over the entire composition range. The created database can be used in a Gibbs energy minimization software to calculate the thermodynamic properties and the phase diagram sections of interest.
