Dissertations / Theses on the topic 'Smelten'

Thesis (MScEng) –Stellenbosch University, 2010
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.
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.
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.
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.
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.
Includes bibliographical references (p. 95).
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.
by Mark J. Steinberg.
M.Arch.

Thesis (PhD)--Stellenbosch University, 2008.
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
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
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.
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

Arsenic is a well-known lung carcinogen in humans. In 2006, IARC upgraded inorganic lead as a possible human carcinogen (2A). The aim of this thesis has been to evaluate the lung cancer mortality and incidence in long-term exposed primary lead smelter workers and also to estimate present exposures to arsenic and lead in relation to those occurring in the past. The basic cohort (N=3832 workers; hired before 1967 and followed up from 1950-1981; SMR comparisons with general and local reference populations) showed an excess of deaths for total mortality, malignant neoplasms (e.g. lung and stomach cancer), ischaemic heart diseases, and cerebrovascular diseases compared to the general population. In a subcohort of lead workers (N=437; regular blood lead sampling since 1950) only the raised SMR for lung cancer (162) was sustained. In a follow-up study of the basic cohort (N=3979), a subcohort of lead exposed workers (N=1992) was formed. The expected mortality in 1955-1987 and cancer incidence in 1958-1987 were calculated relative to county rates. A cumulative blood lead index (CBLI) was used for dose-response analyses. The lung cancer incidence was raised in the total cohort (SIR 2.8; 95 % CI 2.1 3.8). A higher lung cancer risk was observed in workers hired before 1950 (SIR 3.6; 95 % CI 2.6-5.0). The increased lung cancer risks were further elevated in the subcohort of lead exposed workers, especially in the highest exposed subgroup (SIR 5.1; 95 % 2.0-10.5; latency period of 15 y). No excesses of other malignancies were observed. The increased relative risks for lung cancer may have been caused by interactions between inorganic lead and other substances at the smelter, e.g. arsenic. To further analyze the effects from inorganic lead, two subcohorts of workers at the lead departments were formed from the original cohort (N=3979), one of 710 workers and the other of 383 workers. The lung cancer incidence was raised in both subcohorts (Lead subcohort 1; SIR 2.4; 95 % CI 1.2-4.5; Lead subcohort 2; SIR 3.6; 95 % CI 1.2-8.3). Among the 10 workers that had developed lung cancer in lead subcohort 1 all but one had a considerable exposure also to arsenic. Thus, a possible interaction effect between lead and arsenic may explain the increased lung cancer risks. To further elucidate the impact from lead and arsenic a case control study was undertaken. In the basic cohort (N=3979), 46 male workers had contracted respiratory malignancies. They were compared with 141 agematched male referents from the primary smelter by conditional logistic regression analysis using smoking habits, cumulative blood lead and air arsenic exposure as predictor variables. The lung cancer cases showed a significantly higher smoking rate than referents (Odds ratio, OR = 4.0; 95 % CI 1.6-10.1; p=0.003). When restricted to smokers, the cumulative arsenic air exposure index, but not the lead exposure indices, were significantly higher among the cases (OR=1.07; 95 % CI 1.02-1.11; p = 0.005). Accordingly, cumulative arsenic exposure and smoking were identified as significant risk factors for the development of lung cancer in the final analyses, while lead exposure was not a significant risk factor. However, inorganic lead still may play a minor role in the multifactorial genesis of lung cancer. These studies describe risks from exposures occurring from time periods before 1950 up to 1981. Because of the long latency period for lung cancer, exposures after 1970 probably have had limited impact on the reported results. Compared to the levels in the early 1970´s present exposures to arsenic are lower by a factor of ten or more and risks probably correspondingly lower.

Thesis (M.A.)--University of Missouri-Columbia, 2007.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on November 5, 2007) 9 unnumbered blank pages at end of manuscript. Includes bibliographical references.

Minor element (As, Sb, Bi, Pb, Ni) behavior, control and removal techniques in the conventional copper smelting/electrorefining process was studied. The analysis was based on the information collected from an exhaustive literature review, the visit of 23 smelters, 14 electrorefineries and consultations at 15 different institutes specialized in the field.
Data was collected for several types of matte smelting furnaces such as Outokumpu flash, INCO flash, Mitsubishi S-furnace, Teniente Converter, Noranda Process Reactor, Isasmelt and reverberatory. Behavior in Peirce-Smith converting furnaces, Mitsubishi C-furnace, Noranda Continuous Converter and Kennecott-Outokumpu Flash Converting Furnace was also discussed.
The effect of various matte smelting furnace operating parameters such as matte grade, oxygen enrichment, concentration in feed, other minor constituents and temperature on minor element partition to gas and distribution coefficient (wt% matte/wt% slag) was analyzed theoretically and validated with industrial data when possible. Because fewer data were available, only a brief comparison between the elimination in traditional batch converting and new continuous converting processes was performed. The behavior of minor elements in electrorefining was described from a theoretical viewpoint. (Abstract shortened by UMI.)

Le procédé de l’électrolyse Hall-Héroult demeure la méthode principale pour la production mondiale de l’aluminium primaire depuis son invention en 1887. L'utilisation de cathodes mouillables au lieu de cathodes de carbone usuelles a été proposée afin de réduire de plus de 10% de la consommation d'énergie électrique du procédé, ce qui constitue plus de 35% de coûts de la production de l'aluminium. Cependant, à cause des conditions sévères qui prévalent dans le bain d'électrolyse, la fabrication d'une bonne cathode mouillable a été un défi au cours des 60 dernières années et aucune cathode mouillable commerciale n’est encore disponible sur le marché mondial. Dans ce projet, une nouvelle céramique poreuse a été développée par frittage sans pression de TiB2 avec additif de Ti-Fe pré-allié. Ce matériau possède les propriétés requises pour servir de cathode mouillable. Dans cette étude doctorale, le frittage en phase liquide sans pression a été choisi comme méthode de consolidation permettant la fabrication de grandes pièces à un coût relativement bas. Des essais ont été réalisés afin de comprendre l'effet de différentes conditions de traitement y compris la composition d'additif, la température de frittage, le temps de broyage, et la pré-alliage des additifs sur les propriétés physiques, mécaniques et métallurgiques ainsi que le comportement de mouillage et la stabilité des spécimens dans l'aluminium liquide. Après l'ajustement des paramètres de procédé, le matériau sélectionné a été fabriqué par le mélange de TiB2 en poudre avec 10% en poids d'additif 7Ti-3Fe pré-allié dans le broyeur à billes à haute énergie pendant 30 min, suivi par un pressage à 150 MPa et un frittage sous atmosphère de Ar/H2 à 1650°C pendant 1 h. Une microstructure sans fissures avec une distribution uniforme de pores, une densité maximale relative de 91%, une résistance à la flexion de 300 MPa et une résistivité électrique de 54 μΩ.cm ont donc été obtenues. Une goutte d’aluminium a très bien mouillé la surface de l'échantillon et une solidification isotherme s'est produite lors de sa pénétration due à l'interaction avec les additifs métalliques et la formation des phases TiAl3 et Fe4Al13. Malgré la dissolution des additifs métalliques, le matériau développé a montré une excellente stabilité après exposition dans l'aluminium fondu à 960°C pour une durée maximale de 5 jours tout en maintenant sa forme, et aucun signe d’expansion ou de gonflement n’ont été observés. Les analyses microstructurales ont révélé la formation de ponts de TiB2 entre les particules, en présence de phase liquide de Ti-Fe au cours du frittage, et donc la formation d’un squelette TiB2 qui est la cause de la stabilité du matériau développé dans l'aluminium liquide. Par conséquent, ce matériau est proposé en tant qu’un candidat fiable pour l'application en tant que cathodes mouillables dans la production d'aluminium.
Hall-Héroult electrolysis process has been the major method for world production of primary aluminum since its invention in 1887. The use of wettable cathodes instead of usual carbon cathodes has been proposed to reduce more than 10% of the electrical energy consumption of the process which constitutes more than 35% of the aluminum production costs. However, due to the severe conditions of the electrolysis bath, the fabrication of a proper wettable cathode has been a challenge during the last 60 years and no commercial wettable cathode is available in the world market yet. In this project, a novel porous ceramic by pressureless sintering of TiB2 with pre-alloyed Ti-Fe additives was developed. This material showed to meet the required properties to be used as wettable cathode. In this doctoral study, the pressureless sintering in the presence of liquid phase was selected as the consolidation method allowing the fabrication of large parts at relatively lower temperatures and costs. Experimental efforts were made in order to understand the effect of different processing conditions including additive composition, sintering temperature, milling time and pre-alloying of additives on the physical, mechanical and metallurgical properties as well as wetting behavior and stability in liquid aluminum of specimens. Based on the results of the adjustment of processing parameters, the selected material was fabricated by mixing of TiB2 powder and 10 wt% pre-alloyed 7Ti-3Fe additive in high energy ball mill for 30 min, compacting under the pressure of 150 MPa to prepare the green parts, and sintering under Ar/H2 atmosphere at 1650C for 1 h. Uniform crack-free microstructure with even distribution of pores as well as maximum relative density of 91%, bending strength of 300 MPa and electrical resistivity of 54 µΩ.cm were accordingly obtained. Aluminum drop wetted the surface of the specimen very well and isothermal solidification occurred during its penetration due to the interaction with the metallic additives and the formation of TiAl3 and Fe4Al13 phases. Despite of the dissolution of metallic additives, this material showed excellent stability after being exposed to molten aluminum at 960C for up to 5 days by maintaining its shape and no sign of expansion or swelling was observed. Microstructural investigation revealed the precipitation of inter-particle bridges of TiB2 nature in the presence of Ti-Fe liquid phase during sintering forming a TiB2 skeleton, which is the cause of the stability of the developed material in liquid aluminum. This material is proposed as a reliable candidate for application as wettable cathodes in aluminum smelting.

The contribution that sulphur, in the form of sulphates, has on ill health is still a focal point of many a study, especially in environmental studies depicting the effects that particulate air pollution has on health. Although the implication of sulphur on particulate matter is not yet well defined, numerous studies do state that the presence of sulphur on particulate matter contributes to poor health. Sulphur adhered to dust has been associated with cardiovascular mortality and the ability to bring about pathological lung changes, which correlate with changes seen in asthma. There are currently no information regarding the possibility of sulphur loading on particulate dust in a platinum smelter, and consequently, the associated health risk is undefined. Aim: This study aimed to quantify the sulphur content of inhalable and respirable dust in a platinum smelter, as well as to explore the possibility of a correlation between sulphur dioxide exposure and the sulphur content of dust. Method: Three potential high risk activities around the furnaces were identified, and personal sampling was conducted on workers concerned with these tasks. Multi–dust sampling was conducted using an IOM sampler (SKC®) fitted with both a MCE filter and a foam insert. Simultaneously, personal sulphur dioxide exposure was monitored using a Dräger Pac® 7000. The gross airflow direction and velocity was recorded in the proximity of the furnaces, together with relative humidity and dry bulb temperature. Area samples were also obtained with the goal of being subjected to electron microscopy and to determine the pH of the dust. Data was Box–Cox transformed to normalise the distribution, and the transformed data was used for further statistical calculations. Results: Environmental factors were similar on the different floors of the smelter. Sulphur was present on both the respirable and inhalable dust fractions, and the highest sulphur percentage was recorded on the tapping floor. The sulphur content of respirable dust was significantly higher (p = 0.03) than the sulphur content of the IOM foam dust (inhalable and thoracic portion combined). A medium correlation with statistical significance was obtained between respirable sulphur and the SO2 concentration of the ceramic workers (r = 0.27; p < 0.05), as well as the foam sulphur and the SO2 concentrations of the paste loaders (r = 0.32; p < 0.05). No significant correlation could be found between SO2 concentrations and sulphur content of particles when all the samples were considered. Conclusion: Environmental differences recorded on the different floors did not significantly influence sulphur loading. Sulphur contained in smaller particles (respirable dust) is significantly higher than that of the larger particles sampled possible because of an increase in oxidation of SO2 due to an increase in surface area available for sulphur loading in the smaller aerodynamic fraction. The sulphur could however also be attributed to the escape of sulphur containing iron pyrite via the electrodes.
Thesis (MSc (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2012.

Assim como diversos setores industriais, a indústria do alumínio primário está sujeita a incertezas não somente de flutuações de preços, por se tratar de uma commodity, mas de garantias de suprimentos estratégicos, as quais podem se tornar críticas em momentos de crise de falta de abastecimento ou de forte elevação de custo. No caso da indústria do alumínio primário brasileira cujas plantas, conhecidas como smelters, são altamente dependentes do suprimento de energia elétrica, o investimento em co-geração pode se tornar não somente uma proteção, ou hedge contra falta de energia, mas também uma nova fonte de valor, o que é um importante fator de tomada de decisão no momento de investir nessa alternativa. Esta dissertação avalia por metodologia de Opções Reais o valor agregado obtido pela capacidade de auto-suficiência de um smelter hipotético. Os resultados obtidos sugerem que esse valor é significativo.
As occurs with many industrial sectors, the aluminum industry is subject to several uncertain variables, not only regarding prices fluctuations, but mostly with respect to strategic supplies, which can become critical in moments of crisis or cost increases. In the specific case of the Brazilian primary aluminum industry, whose smelters are highly dependent on electricity supply, investment in cogeneration may be viewed not only as a hedge against energy shortages but also as a source of value, which can be an important factor in the decision making process for capital investment in this area. In this dissertation we use the Real Options approach to model the value obtained by self-sufficiency in electricity for a hypothetical smelter. The results suggest this value may be significant.

The Rammelsberg deposit in the Harz mountains in Germany is among the largest metal deposits in the world and has been in continuous use for more than a millennium. There is much controversy as to the nature of the metals produced and the processes involved from the ores of this deposit. This thesis deals with the largest and most accurately excavated smelting site of the high medieval period in the Harz mountains called Huneberg and may be regarded as typical for region and period. Traditionally historians connect the Rammelsberg with silver production, the mining historians, however point out that the deposit is too poor in silver and that copper was produced in the high medieval period. Modern economical literature classifies the Rammelsberg as a lead-zinc deposit. To contribute towards the understanding of these questions an archaeometric study of archaeometallurgic waste- and byproducts, such as slag, furnace lining, furnace wall, litharge and spilled metal drops was undertaken. It builds the base of the interpretation of the metallurgical activities that have taken place at the Huneberg and is contrasted with previous studies. It is suggested that copper, lead and silver in form of argentiferous lead were produced on site, using a complex multi-step process, taking full advantage of the numerous structural features of the site, e.g. the three furnaces present on the site. Successive smelting episodes produced black copper of increasing purity as well as a rather rich argentiferous lead. Because the site is similar to may other sites it is further suggested the mode of metal production at the Huneberg followed a more or less stringent set of recipes and traditions. The mass of 1600 kg slag recovered from the site suggest a copper production of some 600 kg or less, depending on the ore quality. Lead is thought to have been produced in similar quantities, which in turn would mean that the site produced also 1.4 kg of silver during its operation.

It has long been known that Soderberg aluminum smelters are a large source of anthropogenic polycyclic aromatic hydrocarbons in the environment. The atmospheric fate of polycyclic aromatic hydrocarbons is of importance to the aluminum industry in Canada due to their environmental persistence and potential health effects. For Soderberg smelters, the fate of facility emissions is of concern due to the involuntary nature of exposure by the general public in the surrounding regions. Excellent relationships between benzo[a]pyrene and polycyclic aromatic hydrocarbons between different types of Soderberg facilities and raw material formulations were found in the occupational environment during this investigation. This was followed by the comparison of emission profiles of a horizontal stud Soderberg aluminum smelter with profiles measured in a network of sampling stations in the adjacent community. The results suggested that benzo[a]pyrene may be less stable than the majority of the polycyclic aromatic hydrocarbons. An analysis of different sampling sites across Canada revealed that station profiles in the vicinity of Soderberg facilities were different from those found for sites impacted by steel plants, traffic and domestic heating. To explain some of the observed differences, it was hypothesized that polycyclic aromatic hydrocarbons on particulate matter approach a relatively stable profile that is based on the particle characteristics and source intensities. Particle size distribution measurements in the vicinity of the horizontal stud Soderberg aluminum smelter indicated that the majority of the polycyclic aromatic hydrocarbons were associated with particle aerodynamic diameter less than 3 mum. Furthermore, the cascade impactor measurements indicated that there was a sampling artifact of polycyclic aromatic hydrocarbons in-situ during sampling. Relationships for the levels of polycyclic aromatic hydrocarbons from 1997-2002 confirmed that ben

Thesis (M.Sc (Physiology)) --University of Limpopo, 2015
Objective This study assesses whether noise levels above legal limits of 85 dB(A) that can result in noise-induced hearing loss are present in areas where employees are supposed to work and to verify that such areas are demarcated as noise zones at the Polokwane Platinum Smelter. Background and motivation Excessive noise is a global health hazard with considerable social and physiological impact, including the development of noise-induced hearing loss (NIHL). Noise is a major hazard in many workplaces. It is estimated that more than 30 million workers (almost 1 in 10) are exposed to unsafe noise in their work places. NIHL is the second most self-reported occupational illness or injury in the United States. Amongst miners, more than 90% of the population reports hearing problems by the age of 55 years. Noise exposure is prevalent in construction, foundries, agriculture, transport, industry and mining-related activities. The prevalence of NIHL has not changed much in the past two decades. Therefore, a hearing conservation programme is an important issue in the smelter as certain areas are denoted as noise areas. Study design A cross-sectional study design with a group of utility workers at the Polokwane Platinum Smelter, as the experimental group, and a group of undergraduate Bachelor of Science students at the University of Limpopo (Turfloop Campus) served as a control group. Method A sound level meter was used to measure the noise levels where the utility group performs their technical work. Data were analysed using the Statistical Package for the Social Sciences (SPSS) computer program. Results The average noise measured in various locations of the Polokwane Platinum Smelter was between 62.6 dB(A) and 105.1 dB(A). The results indicated that workers at the Polokwane Platinum Smelter are over exposed to noise in certain work areas if they work eight hours in the area. Areas where the average noise level was above noise rating limit of 85 dB(A) were demarcated as noise zones as an additional protective measure. Employees also use hearing protective devices, when they are working in noise zones, to control personal noise exposure. This is in accordance with the Occupational Health and Safety Act No. 85 of 1993 as amended eleventh edition (OHS Act 85/93). Conclusion In the present study, noise levels in certain areas exceeded the noise rating limit of 85 dB(A). However such areas are clearly demarcated as noise areas and employees accessing those area must wear earmuffs or earplugs. Possibilities of employees developing hearing loss overtime exist, if employees work for eight hours or longer in demarcated areas and do not adhere to the existing Hearing Conservation Program (HCP) implemented at the Polokwane Platinum Smelter. Noise levels at the Polokwane Platinum Smelter should be monitored regularly.
University of Limpopo

The Hall-Heroult process for the electrolytic production of aluminium from alumina is a costly and difficult to control process that has remained little changed since the early 1900's. A decreasing trend in the real profitability of the process since 1930 has made it necessary for aluminium smelting companies to reduce the expenditure in all aspects of the process in order to remain viable. The most significant proportion of the costs of production is the utilisation of the electrical energy required to produce the aluminium but improvements such as the rebuilding of the cell superstructure in modern low resistance materials are precluded by the capital costs involved. It is generally only possible to make improvements by changes in operational procedure and the control strategy. The introduction of computer control and data logging systems has reduced the manual involvement in cell operation and has allowed control strategies to be standardised on all cells within a smelter. Although the data logging facilities have increased the amount of data that can be collected and improved the understanding of the operation of aluminium smelting cells, the control of remains difficult due to the lack of data that can be continuously monitored, in particular the alumina concentration in the electrolyte. In this work, a mathematical model for the dynamic simulation of aluminium smelting cells is developed. A simulation program is then written incorporating the exact control algorithms from Anglesey Aluminium's GEL TROl computer control system for half-break cells. The aim of the simulation is to study the effects of different operating conditions and control strategies upon the operation of the cell. The simulation is developed to be modular in nature allowing different control systems and cell models to be easily incorporated and tested. The model is evaluated against data from Anglesey Aluminium's halfbreak cells and is successful in predicting the behaviour of these cells. The simulation is also used in plant trials to investigate the effects of different metal tapping schedules.

Physical and mathematical modelling studies have been performed to investigate liquid flow driven by a horizontally injected gas. The experimental work consisted of water velocity measurements made at 100 locations within a plexiglass tank. Air was introduced into the tank through a series of side-mounted tuyeres, and the effect of air flowrate on water recirculation velocity was observed. The results of the experiments indicate that the maximum water velocity occurs at the water surface. The effect of bubbles coalescing from adjacent tuyeres was observed with increasing air flowrate, and was found to diminish the water recirculation rate. The mathematical model employed a variant of the Marker and Cell (MAC) technique to compute fluid flow with a free surface. The model predictions indicate that the flow in the experimental tank is largely driven by water flowing across the free surface. Based on this knowledge, qualitative predictions of the flow regimes in a Peirce-Smith copper converter and a zinc slag fuming furnace were made.
Applied Science, Faculty of
Mining Engineering, Keevil Institute of
Graduate

Thesis (Ph.D.)--University of Melbourne, Dept. of Chemical Engineering, 2003.
System requirements: Windows PC, CD-Rom drive. CD-Rom contains the appendices, experimental data, and various video clips. Typescript (photocopy). Includes bibliographical references (leaves 209-216).

The equilibrium distribution measurements of As, Sb and Bi between molten copper and white metal and molten copper and matte were conducted to evaluate the activity coefficients of these impurity elements in copper smelting matte. The experimental results were analyzed through comparison and reconciliation with data in the literature. The following equations, based on a liquid standard state, were obtained for ᵞAs, ᵞSb and ᵞBi in white metal coexisting with copper phase at 1,150-1,200°C. Ln ᵞAs = -2.49 + 0.186 NAs; Ln ᵞSb = -1.23 + 23.5 NSb; Ln ᵞBi = 3.01 + 14.0 NBi where Ni represents the mole fraction of the element Bi in white metal. Analysis of the data demonstrated that a major factor in removing As, Sb and Bi in matte during smelting involves careful control of the sulfur pressure, ie. matte's sulfur content, the optimum matte composition's being those that approach the Cu₂S-FeS pseudo binary.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.
Includes bibliographical references (leaves 63-66).
Introduction: Research on the metallurgy of archaeological artifacts has focused primarily on the examination of objects to reveal their design, their composition, the properties of the material people selected to achieve the design, and the fabrication processes used in managing the metal to produce the end product. Recently that focus has begun to broaden, and archaeologists are taking a step back to investigate the earliest stages of prehistoric metal processing that precede object manufacture, namely ore mining and extractive metallurgy. However, little archaeological work on mining and extraction has been accomplished to date, in part because so few metal processing sites have been identified. These sites are very difficult to find because of the lack of standing architecture, particularly smelting installations. Prehistoric smelting furnaces tend to be small and are either excavated beneath the ground surface or are above ground but made of impermanent materials.
by Antonella I. Alunni.
S.B.

The general lack of senior management concern about maintenance activity in industry over the last 20 years, revealed in government surveys. is reflected in the limited literature and virtual absence of research into the principles of organisation theory applied to maintenance organisation structures. This thesis seeks to aleviate this situation by following a systems - contingency approach in a research and comparative analysis of maintenance organisations in the aluminium industry. The key design elements involved in the structure of these maintenance organisations are identified. They are found to be departmentation. size/shape. role of senior maintenance manager. roles of maintenance engineers. roles of maintenance foremen. intra-departmental co-ordination. and inter-departmental co-ordination with production and engineering groups. Those factors. primarily human factors. upon which these design elements may be contingent are proposed and the significance of their impact predicted. Their inter-dependence and influencing mechanisms are described with the aid of a set of systems models. The relationship between changes in the maintenance organisation structure and improvement in maintenance and business performance is demonstrated. together with proposed methods for identifying and measuring that improvement. On the basis of this research. the analysis and design of each key element is possible. and a rational approach to the design of a whole maintenance organisation structure in an aluminium smelting firm can be proposed. It is demonstrated that much of this approach 1s equally relevant to the design of maintenance organisation structures in other process industries.

From the 1950’s to the 1980’s, research in Rwanda highlighted the country’s significant archaeological potential, including some of the earliest evidence for iron production in sub-Saharan Africa. However, years of civil war culminated in the 1994 genocide and the country was left devastated. Further archaeological research to develop the potential already indicated was inappropriate. In 2006 this research project, to explore Rwanda’s past iron smelting traditions, was accepted by the Institute of National Museums in Rwanda. Six months of fieldwork followed, including survey and the excavation of six newly located iron production sites. Archaeometallurgical samples collected in the field have been analysed at the Institute of Archaeology using a variety of different analytical techniques, and the results generated have been interpreted. Thus, aspects of the production techniques represented at each of the smelting locations investigated during this research have been illuminated. This first systematic exploration of diachronic change within iron smelting traditions in Southern Rwanda has revealed two and a half millennia of dynamic technologies embedded within wider society. A chronological framework has been defined to provide a sound basis for the consideration of the results, which include a high-resolution understanding of Early Iron Age smelting techniques and an appreciation of smelting traditions during the Middle Iron Age. Technological traditions have been contextualised within broader Great Lakes, and specifically Rwandan, history, and the significant potential for such high-resolution studies has been demonstrated.

Thesis (Ph. D.)(Metallurgical Engineering)--University of Pretoria, 2004.
Title from opening screen (viewed March 14, 2005). Summaries in English and Afrikaans. Includes bibliographical references.

Sulphuric acid obtained as a byproduct of non-ferrous metal ore smelting is often the mandatory result of stringent environmental policies adopted in the industrialized countries to limit sulphur dioxide emissions. For the primary copper industry in the southwestern U.S., improvement of sulphuric acid marketing and distribution economies is a critical factor. In this thesis, through a comparison of the European and U.S. sulphuric acid market structure and organization, both the opportunity and the implications of adopting European acid marketing practices are discussed. A more centralized system of acid distribution, as in the European model, if applied to the U.S. smelter acid market, proves to be potentially beneficial for net revenue enhancement. A rationalization of the logistic aspects could substantially reduce acid transportation costs, allow repayment of at least average variable costs of production and improve southwestern smelter acid competitiveness in the domestic markets.

The modelling of two key areas of transport phenomena in a new polymetallic smelter has been achieved by using both mathematical andphysical models to investigate optimum operating conditions. A study of oxygen mass transfer caused by multiple top-blown, subsonic gas jets contacting water flowing in a full-scale channel model of the smelter converting hearth has been carried out. A liquid phase solute mass transfer model that incorporates a flowing liquid phase has been developed. It has been used to compare mass transfer for both open-packed and close-packed multiple lance arrays of 2.26 mm, 4.95 mm, 10.95 mm and 24.40 mm nozzles delivering the same quantity of gas. It was found that for fewer lances of the larger nozzle diameters, up to a 75% reduction in liquid phase mass transfer occurred especially for the close-packed configurations. This restriction of mass transfer will result in reduced metal losses in the analogous smelter situation. Over a wide range of channel flowrates the mass transfer coefficient was found to be independent of water velocity. A computer model that predicts the amount of fog formation in the zinc vacuum condenser of the smelter for binary vapour/gas mixtures has identified operating conditions most susceptible to vapour fogging and subsequent metal losses. A fog problem is most likely to occur in condensable mixtures with high vapour concentrations and low initial quantities of superheat, and at low cooling wall temperatures as well as at high total pressures. Any lead in a Pb/Zn/N\({_2}\) condensable mixture will fog heterogeneously at least 400°C before zinc droplets form and act as condensation nuclei for the zinc vapour. An engineering approach to estimating quantities of homogeneous fog formation has been developed and is used to analyse the performance of the Imperial Smelting Furnace zinc condenser and the Port Pirie Vacuum Dezincing Unit.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 109).
Through the identification of phases and their isotopic composition and variability, an assessment of the applicability of uranium decay series dating to El Manchon slags was made. El Manchon is the only Mesoamerican site to exhibit smelting technology. Uranium series dating is typically used on geologically old natural material, but the El Manchon slags were not suitable for other dating techniques. There are four requirements of uranium series dating: measurable presence of appropriate isotopes, cogenetic phases within the material, isotopic fractionation between phases, and the ability to physically separate the phases. This is the first attempt to date archaeological material with the uranium series dating method. Petrographic reflected light microscopy was used to identify the phases in the slags. Electron beam microanalysis was used to identify the chemical composition of the identified phases. Ion beam microanalysis was used to assess the isotopic fractionation between the phases. Electron pulse disaggregation, hand-sorting, and magnetic separations were performed to separate the phases. The slags are composed of four different phases: a silica-melt phase, a quartz-like phase, a copper phase, and a copper-iron-sulfide phase. These four phases are in abundant presence with sufficient isotopic fractionation to make the El Manchon slags suitable for uranium series dating.
by Violetta Wolf.
S.B.