Korkean sulamispisteen oksidien (CaO, Al2O3, Cr2O3) liukoisuus nestemäiseen kuparioksidiin

Thermodynamic databases consisting of carefully acquired phase equilibrium and thermochemical data for oxide systems are an invaluable tool towards optimization and improved control of current copper making processes. Fluxing, which is the main control procedure in copper smelting processes can be fully optimized by employing an accurate thermodynamic database. The result of optimization is a controlled process, which is both efficient in utilization of input materials and versatile to continually changing raw materials. Because a thermodynamic database for metal making processes cannot be modelled solely from first principle calculations, experimental phase equilibrium data is critical in obtaining a consistent database relevant for industrial applications. In this study, an equilibration and quenching technique was adapted to acquire experimental phase equilibria data for selected systems in temperature and composition ranges either poorly known or not previously investigated. For the system Cu-O-CaO in oxidizing conditions, new experimental liquidus data between 1300 and 1500 deg C are presented in this study. In the system Cu-O-CaO-Al2O3, experimental phase equilibria of the triple points of the system by the quenching technique are presented for the first time. Prior to this study, phase equilibria of the system Cu-O-CaO-Al2O3 has not been experimentally studied, otherwise equilibria of the system was estimated by extrapolations. The liquidus of the system Cu-O-Cr2O3 has also been investigated by the equilibration technique for the first time. Experimental results of this thesis reveal that liquidus data for simple oxide systems of copper are poorly known and currently insufficient to accurately predict higher order systems. The experimental phase equilibria data acquired in this dissertation will improve prediction of high order oxide systems for process metallurgy.Termodynaamiset tietokannat, jotka sisältävät huolellisesti mitattua faasitasapainodataa ja termodynaamisia ainearvoja oksidisysteemeille, ovat korvaamattomia työkaluja kuparin valmistusmenetelmien optimoinnissa ja prosessin parantamisessa. Fluksaus, joka on kuparin sulatuksen pääasiallinen hallintamenetelmä, voidaan optimoida käyttämällä näitä tarkkoja termodynaamisia tietokantoja. Optimoinnin tuloksena saavutetaan hallittu valmistusmenetelmä joka on sekä tehokas syötemateriaalin käytössä, että joustava pystyen vastaamaan jatkuvasti vaihtuviin raaka-aineisiin. Koska termodynaamista tietokantaa metallinvalmistusmenetelmiä varten ei voida mallintaa puhtaasti laskennallisesti, kokeellinen faasitasapainodata on kriittistä yhtenäisen, teollisille sovelluksille merkityksellisen tietokannan kehittämiselle. Tässä työssä sovellettiin tasapainotus- ja sammutusmenetelmää faasitasapainodatan mittaamiseksi valituille systeemeille ennestään tuntemattomilla lämpötila- ja koostumusalueilla. Tässä työssä on mitattu uusia tasapainoarvoja Cu-O-CaO-systeemissä hapettavissa olosuhteissa lämpötilavälillä 1300 deg C - 1500 deg C. Cu-O-Al2O3-CaO-systeemin faasitasapainoa kolmoispisteissä mitattiin tässä työssä ensimmäistä kertaa sammutusmenetelmällä. Aikaisemmissa malleissa systeemin faasitasapainot on arvioitu ekstrapoloimalla kokeellisen tiedon puutteen takia. Myös Cu-O-Cr2O3-systeemin likvidusta on tutkittu sammutus- ja tasapainotusmenetelmällä ensimmäistä kertaa. Väitöstyön kokeelliset tulokset paljastavat, että yksinkertaisten kuparioksidisysteemien likvidus on huonosti tunnettu ja tällä hetkellä riittämätön mahdollistaakseen monikomponenttisten systeemien tarkan ennustamisen. Tässä väitöstyössä saadut tulokset parantavat monikomponenttisten oksidisysteemien ennustuksen luotettavuutta prosessimetallurgiassa

Measurement of surface tension in base metal sulphide mattes by an improved sessile drop method

Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: See item for full textAFRIKAANSE OPSOMMING: Sien item vir voltek

Selective reductive leaching of cobalt and lithium from industrially crushed waste Li-ion batteries in sulfuric acid system

Recycling of valuable metals from secondary resources such as waste Li-ion batteries (LIBs) has recently attracted significant attention due to the depletion of high-grade natural resources and increasing interest in the circular economy of metals. In this article, the sulfuric acid leaching of industrially produced waste LIBs scraps with 23.6% cobalt (Co), 3.6% lithium (Li) and 6.2% copper (Cu) was investigated. The industrially produced LIBs scraps were shown to provide higher Li and Co leaching extractions compared to dissolution of corresponding amount of pure LiCoO2. In addition, with the addition of ascorbic acid as reducing agent, copper extraction showed decrease, opposite to Co and Li. Based on this, we propose a new method for the selective leaching of battery metals Co and Li from the industrially crushed LIBs waste at high solid/liquid ratio (S/L) that leaves impurities like Cu in the solid residue. Using ascorbic acid (C6H8O6) as reductant, the optimum conditions for LIBs leaching were found to be T = 80 °C, t = 90 min, [H2SO4] = 2 M, [C6H8O6] = 0.11 M and S/L = 200 g/L. This resulted in leaching efficiencies of 95.7% for Li and 93.8% for Co, whereas in contrast, Cu extraction was only 0.7%. Consequently, the proposed leaching method produces a pregnant leach solution (PLS) with high Li (7.0 g/L) and Co (44.4 g/L) concentration as well as a leach residue rich in Cu (up to 12 wt%) that is suitable as a feed fraction for primary or secondary copper production.Peer reviewe

Phase equilibria and thermodynamic evaluation of the Fe-V-O system in air

The Fe-V-O system in air was studied experimentally ranging from 700 °C to 1450 °C by high-temperature equilibration, quenching, scanning electron microscope and microprobe analysis. The thermodynamic evaluation was performed with FactSage 7.0. The solubility of V2O5(s) in Fe2O3(s) was described with the compound energy formalism. The properties of the liquid phase were described with both the quasichemical model and the associate species model. A set of self-consistent thermodynamic parameters were estimated within acceptable error limits. The calculated phase diagram of Fe-V-O in air is presented and compared to experimental observations and other literature data.Peer reviewe

Design of optimal electrolyte circulation based on the kinetic modelling of copper dissolution in silver electrorefining

Copper is the major impurity dissolved in silver electrorefining which potentially accumulates in the electrolyte during the process and co-deposits onto the cathode surface, decreasing the product quality. The study investigated the dissolution kinetics of copper in silver electrorefining as a function of wt%Cu in the industrial electrolyte ranges of 40–100 g/dm3 [Ag+], 5–15 g/dm3 [HNO3] and 20–60 g/dm3 [Cu2+] at 25–45 °C. The results showed that Cu dissolved at a higher rate in comparison to silver and that the two kinetic models developed have good accuracy and validity. From the models, optimal electrolyte circulation parameters were simulated to avoid [Cu2+] accumulation in the electrolyte. As a conclusion, processing 1% Cu anodes at the critical [Cu2+]/[Ag+] ratio of 0.8 in the electrolyte requires an inlet of [Ag+] of 2.3–3.3 and tolerates [Cu2+] of 0.14–0.47 times that of the [Ag+] and [Cu2+] in the bulk electrolyte, respectively. Furthermore, electrolyte with higher [Ag+] provides the benefit of reduced electrolyte circulation flowrate and increased tolerance of wt%-Cu in the silver anodes.Peer reviewe

Thermal Conductivity of Solidified Industrial Copper Matte and Fayalite Slag

The thermal conductivity of various copper matte and fayalite slag was measured using laser flash analysis, a non-steady state measurement method. Industrial matte and slag samples were taken in such a way that their composition represented typical process conditions. Thermal conductivities for solid copper matte (average 64% Cu) were found to be from 1.2 W m−1 K−1 at 300°C to 2.1 W m−1 K−1 at 900°C. Because arsenic is one of the most important impurities in copper matte, its effect on thermal conductivity was investigated with As-doped matte samples up to 0.59% As. The results showed substantially lower thermal conductivity, between 0.5 W m−1 K−1 and 1.3 W m−1 K−1 at 300–900°C with low As matte, behavior that is analogous to that of a semiconductor. The data obtained showed that the thermal conductivity of copper matte increased linearly with temperature, but the gradient was small. The thermal conductivity of slags was found to be between 1.6 W m−1 K−1 and 1.9 W m−1 K−1, values that are consistent with earlier studies.Peer reviewe

Phase equilibria and thermodynamic evaluation of the Ti-V-O system in air

The Ti-V-O system was studied experimentally from 700 °C to 1500 °C by high-temperature equilibration, quenching, scanning electron microscope and Energy-Dispersive X-Ray spectroscopy. The solubility of titanium in the slag is less than 3 mol% at 1500 °C and the vanadium solubility in the rutile phase reached a maximum of 7.8 mol% at 1400 °C. The thermodynamic evaluation was performed with FactSage 7.0. The solubility of vanadium in the rutile phase was developed within the framework of the compound energy formalism. The properties of the liquid phase were described with the quasichemical model. A set of self-consistent thermodynamic parameters was estimated well within acceptable limits. The calculated phase diagram of the Ti-V-O system in air is presented and compared to experimental observations and other phase diagram data from literature.Peer reviewe

Phase equilibria and thermodynamic evaluation of the Fe-V-O system in air

Please read abstract in the article.The Glencore Chair in Pyrometallurgical Modelling at the University of Pretoria.https://www.elsevier.com/locate/calphad2019-12-01hj2018Materials Science and Metallurgical Engineerin

Phase equilibria and thermodynamic evaluation of the Ti-V-O system in air

The Ti-V-O system was studied experimentally from 700 °C to 1500 °C by high-temperature equilibration, quenching, scanning electron microscope and Energy-Dispersive X-Ray spectroscopy. The solubility of titanium in the slag is less than 3 mol% at 1500 °C and the vanadium solubility in the rutile phase reached a maximum of 7.8 mol% at 1400 °C. The thermodynamic evaluation was performed with FactSage 7.0. The solubility of vanadium in the rutile phase was developed within the framework of the compound energy formalism. The properties of the liquid phase were described with the quasichemical model. A set of self-consistent thermodynamic parameters was estimated well within acceptable limits. The calculated phase diagram of the Ti-V-O system in air is presented and compared to experimental observations and other phase diagram data from literature.The Glencore Chair in Pyrometallurgical Modelling at the University of Pretoria, South Africa.https://www.elsevier.com/locate/calphad2019-12-01hj2018Materials Science and Metallurgical Engineerin