Academic literature on the topic 'Smelten'

Thesis (MScEng) –Stellenbosch University, 2010<br>ENGLISH ABSTRACT: More mining houses are turning their attention to the processing of ore mined from the UG2 reef. This is mainly due to the depletion of the Merensky reef or the low availability of ore from the Platreef. With the higher UG2 ore concentration in the process feed, companies experience more problems with the processing of the ore due to its high chrome content. Although there are various possible solutions to the problems experienced in the processing of UG2 ore, very little of thise solutions are actually implemented in the industry. When smelting chrome-bearing ore, the chrome can go to any of three phases: matte phase, spinel phase or glass phase. If it reports to the furnace matte phase it can lead to problems in the down stream processing. When chrome forms part of the spinel phase it forms a solid, refractory-like material which, to an extent, is an unwanted material inside the furnace. Lastly the chrome can report to the glass phase (liquid phase) which is the more desireable phase to which chrome should report to since it will have little or no impact on downstream processing. There were four main objectives for this research project namely to conduct a literature review to understand the problem of chrome in the smelting process, to do an experimental simulation of a matte and slag phase in one crucible, to interpret the experimental results and compare the experimental results to thermodynamic predictions obtained using FactSageTM. From literature the following aspects were found to be important: Silica structures Research has shown that silica incorporates different metal ions into its structures. When the metal ions are incorporated into the silica structures they are seen as part of the glass phase. By incorporating cations such as chromium into the silica structure the structure is able to maintain its neutral electrical charge. Basicity of slag Oxides once melted will either donate or accept oxide ions. The group of oxides that are in excess will determine whether that specific slag is acidic or non acidic. This is important to our study since the basicity can determine the stability of the spinel phase. Partial pressures The partial pressure of the system is important since it forms part of the equilibrium constant calculations - meaning that partial pressures determine the stability of certain species. Currently different arguments exist as to how the sulphur pressure inside a molten bath is maintained. What is important, however, is that for the system in this research project a log oxygen partial pressure of -8 and a log sulphur partial pressure of -3.5 was chosen. These values were based on previous research done on PGM and copper smelting processes. Chrome deportment Previous research on chrome deportment shows a relationship between temperature and the amount of chromium dissolving into the glass phase as well as an increased chromium(II)oxide solubility (when compared to chromium(III)oxide) in a silicate melt. Regarding slag chemistry and chrome deportment very little work has been published for the system found in the PGM industry but it is mentioned that by adjusting certain slag additives (alumina, lime and silica) the chrome deportment can be manipulated. The scope of this project was to investigate the effect of chromium, lime and silica on chrome deportment. More specifically, the effect of lime. The reason being that lime was originally added as 10%wt of the feed stream in the processing of Merensky ore to act as a fluxing agent. With the new furnace design and higher power densities the slag are maintained at 200oC to 350oC higher than when Merensky ore was smelted. With these higher slag temperatures fluxing agents will play a smaller role meaning that lime additions become less important. Literature studies also showed that additional lime in a slag system can stabilize the spinel structure (which is an unwanted phase). Removing lime would be advantageous out of a chrome presepective as well as an economic point of view. The research was conducted in three sections namely the determination of the time required for this particular system to reach equilibrium, the investigation of different additives on chrome deportment using a controlled atmosphere and synthetic slags and, lastly, a comparison of the experimental results obtained to thermodynamic predictions. For the equilibration studies reaction time periods of 4,7,11 and 16 hours were used. From the results it was found that the alumina crucible dissolved into the glass phase continually. This indicated that equilibrium was not reached. However, a reaction time, rather than an equilibrium time, was chosen where the species and phases had enough time to react. This was based on literature, on observations of species diffusing between the matte and slag phase as well as on two-point analysis (diffusion gradients). A reaction time of nine hours was chosen With the reaction time fixed, the effect of different slag additives on chrome deportment was investigated. For the addition of chrome it was seen that an 1.5%wt increase in the starting material increased the chrome content of the slag phase by 0.025%wt. For the same increase in chromium in the starting materials the chrome content of the spinel phase increased by 2.1% indicating that chromium has a tendency to report to the spinel phase. The increase in chromium had a minor effect on the chrome content of the matte phase, however, since the chrome content only increased from 0.025%wt to 0.028%wt. Plotting the results showed that increasing the lime in the starting material decreases the chromium content in the glass phase. For the 39%wt silica system the chromium content in the glass phase decreased from 0.75%wt to 0.46%wt for an increase in the lime content from 1.7%wt to 7.3%wt. The same trend was seen for the 33%wt silica system. For the spinel phase an increase of 1.27%wt was seen when the lime content of the starting materials was increased from 1.7%wt to 10.1%wt for a 33%wt silica system. The same increase in lime increased the chrome content of the matte phase from 0.03%wt to 0.06%wt for a 33%wt silica system. Silica also proved to affect chrome deportment. Increasing the silica content of the starting materials from 25%wt to 39%wt increased the amount of chromium in the glass phase from 0%wt to 0.46%wt for a 10%wt lime system. The same effect is seen for a lower lime content except that more chromium were incorporated into the silica structure. A silica increase from 32.4%wt to 39%wt resulted in a chromium decrease from 5.2%wt to 0% in the spinel phase for a 10%wt lime system. The same trend was seen for the 1.5%wt lime system. An increase in the silica levels lead to an increase in the chrome level of the matte phase. When silica is increased from 32%wt to 39%wt the chrome content of the matte phase increased from 0.06%wt to 0.07%wt. The last part of the research project entailed the comparison of the trends observed with the experimental results to trends obtained from thermodynamic predictions. FactSageTM is a program that uses model equations to predict the Gibbs free energies for different phases. The program is therefore also able to predict the amount of different phases present at equilibrium. This is called thermodynamic ”optimization”. In section 6 trends that were observed from FactSageTM results are compared to the trends found in the experimental results. It is important to note that it is only trends that are evaluated and not actual values since FactSageTM calculations are for a system that is at equilibrium and (as explained above) this system is not at complete equilibrium. The comparison however was good. Several trends found in the experimental results were confirmed by the results from FactSageTM. These included the relationships of chromium fed versus chromium spinel, lime fed versus chromium spinel, lime fed versus chromium in glass, silica fed versus chromium in glass, silica fed versus chromium in spinel and silica fed versus chromium in matte. To conclude, slag additions can be used to manipulate chrome deportment to an extent. Secondly, FactSageTM can be used for thermodynamic predictions but a proper understanding as well as some form of validation of the specific system investigated is still needed. Due to time constraints and the difficulty of experimentally simulating this multi-phase system in the lab, only a few parameters were investigated. In order to obtain a more complete understanding of the system the effect of partial pressures and temperature should also be investigated.

En el presente documento se elabora el Planeamiento Estratégico de la empresa Ecosem Smelter. El plan estratégico es el resultado del análisis de los factores externos e internos de Ecosem Smelter, que permitieron identificar cuáles eran las principales oportunidades, amenazas, fortalezas, y debilidades. En ese sentido, a partir de la elaboración de las diferentes matrices, se establecerán las estrategias que permitan mejorar la competitividad de la empresa para cumplir con los objetivos de largo plazo y sus correspondientes objetivos a corto plazo, con la finalidad de poder alcanzar misión y visión trazada. Para lograr estos objetivos se propone incrementar los ingresos y la rentabilidad, a partir del mayor dinamismo comercial de sus principales líneas de negocio, como: carguío, transporte y descarga de mineral de cobre; chancado; y transporte de volquetes de MKPS, ofreciendo ventajas competitivas ante sus principales competidores, que le permita crecer de forma sostenible, y mantener su liderazgo, en la región Pasco.<br>This paper called Strategic Business Planning of Ecosem Smelter. This Strategic Business Planning is the result of analysis of the external and internal factors of the Ecosem Smelter, which identified what were the main opportunities, threats, strengths, and weaknesses. In that sense, was developed different matrices, strategic plans to improve the competitiveness of the corporation to meet long-term goals and their short-term goals, with the purpose to achieve mission and vision they will be established. To achieve these objectives, it is proposed to increase revenues and profitability, based on the greater commercial dynamism of its main business lines, such as: loading, transportation and discharge of copper ore; curses and transport of MKPS dump trucks, offering competitive advantages over its main competitors, which allows it to grow sustainably, and maintain its leadership, in the Pasco region.<br>Tesis

An experimental study of minor element elimination from copper smelter dust by vacuum calcination was carried out. The rationale for the study was to test the feasibility of vacuum calcination as a treatment to separate minor elements from copper smelter dusts and to recover the copper values in the dust.<br>The physical, chemical and mineralogical nature of copper smelter dust as received was characterized using ICP, AA, XRD, EDS etc. The prevailing mineralogical components of the dust were copper sulfate, lead sulfate and magnetite. It was observed that the dust particles consisted of spherical and irregular shaped agglomerated solid droplets.<br>Experiments were performed to measure the extent of removal of bismuth, arsenic, lead and zinc from copper smelter dust exposed to a vacuum in the range from 50 to 110 Pascal in the temperature range from 600 °C to 950 °C and for a time in the range from 30 minutes to 90 minutes. Fifty gram samples of smelter dust were used in each test. It was found that up to 97 % Bi, 99 % As and 99 % Pb eliminations from the dust were achieved in experiments, performed at 900 °C, in the pressure of 50~110 Pa and for a period of 60 minutes with the addition of copper concentrate in different ratios. (Abstract shortened by UMI.)

Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 2000.<br>Includes bibliographical references (p. 95).<br>In 1959 professor of archeology Beno Rothenberg began investigating the production of copper in the Sinai desert and Aravah region of southern Israel. He discovered over 650 previously unknown ancient copper mining and smelting sites. The Timna Valley is one of the most significant sites discovered and is believed to be the first site of copper production, beginning six-thousand years ago. Within this rich historical context, I propose to build an international center for desert studies and copper production in ancient societies. Faculty, students, and researchers will examine desert climate, vegetation, and wildlife. Equally important, they will study the process of mining and smelting copper. The center will also be open to individual tourists and larger groups. Following an introductory lecture, tourists will produce their own small samples of copper. The architecture of the building is driven from the nature of the smelting process. In this process, copper is chemically separated from impurities in a smelting furnace. Heavy metallic copper sinks to the bottom of the furnace. Slag forms above the copper and gas evaporates. The layers of the building mimic this process and are made from copper, slag, and glass. The overall design theme of the building also seeks to demonstrate a clear interaction between building, landscape, and environment.<br>by Mark J. Steinberg.<br>M.Arch.

Thesis (PhD)--Stellenbosch University, 2008.<br>ENGLISH ABSTRACT: The growing need to improve accounting accuracy, precision and to standardise generally accepted measurement methods in the mining and processing industries has led to the joining of a number of organisations under the AMIRA International umbrella, with the purpose of fulfilling these objectives. As part of this venture, Anglo Platinum undertook a project on the material balancing around its largest smelter, the Waterval Smelter. The primary objective of the project was to perform a statistical material balance around the Waterval Smelter using the Maximum Likelihood method with respect to platinum, rhodium, nickel, sulphur and chrome (III) oxide. Pt, Rh and Ni were selected for their significant contribution to the company’s profit margin, whilst S was included because of its environmental importance. Cr2O3 was included for its importance in as far as the difficulties its presence poses in smelting of PGMs. The objective was achieved by performing a series of statistical computations. These include; quantification of total and analytical uncertainties, detection of outliers, estimation and modelling of daily and monthly measurement uncertainties, parameter estimation and data reconciliation. Comparisons were made between the Maximum Likelihood and Least Squares methods. Total uncertainties associated with the daily grades were determined by use of variographic studies. The estimated Pt standard deviations were within 10% relative to the respective average grades with a few exceptions. The total uncertainties were split into their respective components by determining analytical variances from analytical replicates. The results indicated that the sampling components of the total uncertainty were generally larger as compared to their analytical counterparts. WCM, the platinum rich Waterval smelter product, has an uncertainty that is worth ~R2 103 000 in its daily Pt grade. This estimated figure shows that the quality of measurements do not only affect the accuracy of metal accounting, but can have considerable implications if not quantified and managed. The daily uncertainties were estimated using Kriging and bootstrapped to obtain estimates for the monthly uncertainties. Distributions were fitted using MLE on the distribution fitting tool of the JMP6.0 programme and goodness of fit tests were performed. The data were fitted with normal and beta distributions, and there was a notable decrease in the skewness from the daily to the monthly data. The reconciliation of the data was performed using the Maximum Likelihood and comparing that with the widely used Least Squares. The Maximum Likelihood and Least Squares adjustments were performed on simulated data in order to conduct a test of accuracy and to determine the extent of error reduction after the reconciliation exercise. The test showed that the two methods had comparable accuracies and error reduction capabilities. However, it was shown that modelling of uncertainties with the unbounded normal distribution does lead to the estimation of adjustments so large that negative adjusted values are the result. The benefit of modelling the uncertainties with a bounded distribution, which is the beta distribution in this case, is that the possibility of obtaining negative adjusted values is annihilated. ML-adjusted values (beta) will always be non-negative, therefore feasible. In a further comparison of the ML(bounded model) and the LS methods in the material balancing of the Waterval smelter complex, it was found that for all those streams whose uncertainties were modelled with a beta distribution, i.e. those whose distribution possessed some degree of skewness, the ML adjustments were significantly smaller than the LS counterparts It is therefore concluded that the Maximum Likelihood (bounded models) is a rigorous alternative method of data reconciliation to the LS method with the benefits of; -- Better estimates due to the fact that the nature of the data (distribution) is not assumed, but determined through distribution fitting and parameter estimation -- Adjusted values can never be negative due to the bounded nature of the distribution The novel contributions made in this thesis are as follows; -- The Maximum Likelihood method was for the first time employed in the material balancing of non-normally distributed data and compared with the well-known Least Squares method -- This was an original integration of geostatistical methods with data reconciliation to quantify and predict measurement uncertainties. -- For the first time, measurement uncertainties were modeled with a distribution that was non-normal and bounded in nature, leading to smaller adjustments<br>AFRIKAANSE OPSOMMING: Die groeiende behoefte aan rekeningkundige akkuraatheid, en om presisie te verbeter, en te standardiseer op algemeen aanvaarde meetmetodes in die mynbou en prosesseringsnywerhede, het gelei tot die samwewerking van 'n aantal van organisasies onder die AMIRA International sambreel, met die doel om bogenoemde behoeftes aan te spreek. As deel van hierdie onderneming, het Anglo Platinum onderneem om 'n projek op die materiaal balansering rondom sy grootste smelter, die Waterval smelter. Die primêre doel van die projek was om 'n statistiese materiaal balans rondom die Waterval smelter uit te voer deur gebruik te maak van die sogenaamde maksimum waarskynlikheid metode met betrekking tot platinum, rodium, nikkel, swawel en chroom (iii) oxied. Pt, Rh en Ni was gekies vir hul beduidende bydrae tot die maatskappy se winsmarge, terwyl S ingesluit was weens sy belangrike omgewingsimpak. Cr2O3 was ingesluit weens sy impak op die smelting van Platinum groep minerale. Die doelstelling was bereik deur die uitvoering van 'n reeks van statistiese berekeninge. Hierdie sluit in: die kwantifisering van die totale en analitiese variansies, opsporing van uitskieters, beraming en modellering van daaglikse en maandelikse metingsvariansies, parameter beraming en data rekonsiliasie. Vergelykings was getref tussen die maksimum waarskynlikheid en kleinste kwadrate metodes. Totale onsekerhede of variansies geassosieer met die daaglikse grade was bepaal deur ’n Variografiese studie. Die beraamde Pt standaard afwykings was binne 10% relatief tot die onderskeie gemiddelde grade met sommige uitsonderings. Die totale onsekerhede was onderverdeel in hul onderskeie komponente deur bepaling van die ontledingsvariansies van duplikate. Die uitslae toon dat die monsternemings komponente van die totale onsekerheid oor die algemeen groter was as hul bypassende analitiese variansies. WCM, ‘n platinum-ryke Waterval Smelter produk, het 'n onsekerheid in die orde van ~twee miljoen rand in sy daagliks Pt graad. Hierdie beraamde waarde toon dat die kwaliteit van metings nie alleen die akkuraatheid van metaal rekeningkunde affekteer nie, maar aansienlike finansiële implikasies het indien nie die nie gekwantifiseer en bestuur word nie. Die daagliks onsekerhede was beraam deur gebruik te maak van “Kriging” en “Bootstrap” metodes om die maandelikse onsekerhede te beraam. Verspreidings was gepas deur gebruik te maak van hoogste waarskynlikheid beraming passings en goedheid–van-pas toetse was uitgevoer. Die data was gepas met Normaal en Beta verspreidings, en daar was 'n opmerklike vermindering in die skeefheid van die daaglikse tot die maandeliks data. Die rekonsiliasies van die massabalans data was uitgevoer deur die gebruik die maksimum waarskynlikheid metodes en vergelyk daardie met die algemeen gebruikde kleinste kwadrate metode. Die maksimum waarskynlikheid (ML) en kleinste kwadrate (LS) aanpassings was uitgevoer op gesimuleerde data ten einde die akkuraatheid te toets en om die mate van fout vermindering na die rekonsiliasie te bepaal. Die toets getoon dat die twee metodes het vergelykbare akkuraathede en foutverminderingsvermoëns. Dit was egter getoon dat modellering van die onsekerhede met die onbegrensde Normaal verdeling lei tot die beraming van aanpassings wat so groot is dat negatiewe verstelde waardes kan onstaan na rekosniliasie. Die voordeel om onsekerhede met 'n begrensde distribusie te modelleer, soos die beta distribusie in hierdie geval, is dat die moontlikheid om negatiewe verstelde waardes te verkry uitgelsuit word. ML-verstelde waardes (met die Beta distribusie funksie) sal altyd nie-negatief wees, en om hierdie rede uitvoerbaar. In 'n verdere vergelyking van die ML (begrensd) en die LS metodes in die materiaal balansering van die waterval smelter kompleks, is dit gevind dat vir almal daardie strome waarvan die onserkerhede gesimuleer was met 'n Beta distribusie, dus daardie strome waarvan die onsekerheidsdistribusie ‘n mate van skeefheid toon, die ML verstellings altyd beduidend kleiner was as die ooreenkomstige LS verstellings. Vervolgens word die Maksimum Waarskynlikheid metode (met begrensde modelle) gesien as 'n beter alternatiewe metode van data rekosiliasie in vergelyking met die kleinste kwadrate metode met die voordele van: • Beter beramings te danke aan die feit dat die aard van die onsekerheidsdistribusie nie aangeneem word nie, maar bepaal is deur die distribusie te pas en deur van parameter beraming gebruik te maak. • Die aangepaste waardes kan nooit negatief wees te danke aan die begrensde aard van die verdeling. Die volgende oorspronklike bydraes is gelewer in hierdie verhandeling: • Die Maksimum Waarskynlikheid metode was vir die eerste keer geëvalueer vir massa balans rekonsiliasie van nie-Normaal verspreide data en vergelyk met die bekendde kleinste kwadrate metode. • Dit is die eerste keer geostatistiese metodes geïntegreer is met data rekonsiliasie om onsekerhede te beraam waarbinne verstellings gemaak word. • Vir die eerste keer, is meetonsekerhede gemoddelleer met 'n distribusie wat nie- Normaal en begrensd van aard is, wat lei tot kleiner en meer realistiese verstellings.

Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2006<br>Better metallurgical accounting practices are achieved through implementation of robust and accurate analytical techniques, in particular the sample preparation techniques involved, as well as characterization of all possible errors associated with such techniques and those associated with the characteristics of the materials to be analyzed. As a contribution to the AMIRA P754 project which aims at developing standards and tools for metal balancing, reconciliation and reporting from mine resource to final product, this thesis presents best practices for the characterization of ferrochrome smelter slag. The characterization ofthe slag is also essential for process control, and thus its implications to the performance of the smelting process are also discussed in this thesis. Slag samples from a ferrochrome smelter were analyzed using an XRF powder pellet analytical technique in contrast to the rep technique used at the plant laboratory, to determine their composition. This was done to evaluate the possibility of using XRF as an alternative technique to improve the turnaround times at the plant laboratory. It was found that the XRF analysis of the composite slag by pressed powder pellets could be performed rapidly, but because of the grain size effects resulted from the entrained alloy particles which could not pulverize well, the results were not accurate. This then led to the introduction of an extra stage (oxidation of the entrained alloy particles) in the sample preparation procedure, which prolonged the turnaround time by about 16 hours. However, an important achievement was that the entrained alloy particles could be oxidized into their oxides to obtain homogeneous samples and therefore representative sub-samples. This is an important improvement in the practices at the plant laboratory which involved excluding some of the entrained alloy particles and thus analyzing biased, non-representative samples. A rapid estimation of the percentage of the entrained alloy in slag was proven to be possible using a simple model (which relates density and the mass fraction of the entrained alloy), in conjunction with a density measuring device (a pycnometer). This ability serves as a significant improvement in the mass balancing and metallurgical accounting practices at ferrochrome producers. This thesis also describes the manner in which heterogeneity can be quantified as well as the errors associated with heterogeneity and their implications to the analysis results. Heterogeneity in ferrochrome slag has been found to depend significantly on the amount of alloy entrainment in slag, and therefore the slag viscosity, tapping temperature and chemical composition. One can therefore conclude that the sampling constant and therefore sample mass is dependent on furnace operating conditions.

Thesis (Ph.D.)--University of Cincinnati, 2009.<br>Advisors: Glenn Talaska PhD (Committee Chair), Paul Succop PhD (Committee Member), Mary Beth Genter PhD (Committee Member), James Mack PhD (Committee Member), Tania Carreon PhD (Committee Member). Title from electronic thesis title page (viewed April 26, 2009). Keywords: PAC; Offshore; exposure; biomonitoring; aluminium. Includes abstract. Includes bibliographical references.

The ideal aluminium smelting cell should operate at a fixed temperature and superheat. However, spatial and temporal operating strategies cause changes in temperature, which usually result in variations in superheat as well. Contrasting, in the long term, for mature cells the aluminium fluoride consumption is fairly accurately reflected by the soda and calcium oxide contents of the primary alumina. Therefore the poor control of aluminium fluoride concentration reflects the poor understanding of the causes of variation in aluminium fluoride concentration and molten bath mass within the cell. The aims of this thesis were to i. Develop a better understanding of how the dynamics of the aluminium smelting process impact process conditions ??? hence bath chemistry ii. Subsequently develop and evaluate diagnostic models that may be used to minimise the variations in chemistry in individual operating cells The key control feature to minimise adverse effects is Superheat. The ideal aluminium smelting cell should operate at a fixed temperature and superheat. However, spatial and temporal operating strategies cause changes in temperature, which usually result in variations in superheat as well. In this thesis industrial aluminium reduction cells and their material handling and dry scrubbing operation were analysed in respect to their energy and material balance. A number of experiments were carried out to study the influence of process parameters and operations on the state and path function of a cell. Bath inventory measurements lead to a better understanding of the underlying process behaviour, and it was obvious that energy and mass balance cannot be controlled independently. With regard to the response of bath inventory, bath and liquidus temperature to pot operation, the following interesting phenomena were identified: - some cells are active or inactive with respect to their response to aluminium fluoride additions - positive and negative voltage steps cause non-proportional changes in liquidus and bath temperatures - the liquidus temperature, bath volume and composition can respond rapidly to changes due to alumina feeding Successful application of the results and understanding developed in this research resulted in an energy requirement reduction of 1 kWh/kg