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1
Labonté, Germain 1960. "Electrochemical potentials in flotation systems : measurement, interpretation and applications". Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63825.
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2
Penberthy, Catharina Johanna. "The effect of mineralogical variation in the UG2 chromitite on recovery of platinum-group elements". Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-11282005-113358/.
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3
Stange, Wayne. "Towards more effective simulation of minerals processing systems". Thesis, University of the Witwatersrand, Johannesburg, 1988. http://hdl.handle.net/10539/21140.
Testo completoAbstract (sommario):
Two aspects of the computer simulation of minerals processing systems were
investigated in order to facilitate more effective use of simulation technology.
A user-interface was designed and combined with an existing simulator
executive, resulting in the implementation of a user-friendly microcomputer based
minerals processing simulator, MicroSim. Ease of use was achieved by
consideration of the needs of the user of such a program. This resulted in the use
of graphical methods for information input and output. Efficient form-filling
techniques were developed for numerical data entry and editing.
Models for the carbon-in-pulp adsorption process and for continuous gold
leaching were derived. The CIP models were derived using a population balance
approach. The method of characteristics and the method of moments were found
to be particularly useful in solving the resulting equations. Besides being
important processes in themselves, the integration of these models into MicroSim
provided valuable experience regarding the use of such models in a simulator.AC 2016
4
Alves, Paula Regina. "The carbonatite-hosted apatite deposit of Jacupiranga, SE Brazil: styles of mineralization, ore characterization and association with mineral processing". Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/prayb4_09007dcc804f7bd9.pdf.
Testo completoAbstract (sommario):
Thesis (M.S.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 9, 2008) Includes bibliographical references (p. 131-139).
5
Cline, Jean Schroeder. "Physical and chemical aspects of fluid evolution in hydrothermal ore systems". Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-09162005-115029/.
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6
Van, der Merwe Josias Willem. "Dissolution of sphalerite minerals from Rosh Pinah tailings". Pretoria : [s.n.], 2003. http://upetd.up.ac.za/thesis/available/etd-04282005-124139.
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7
Dai, Qiang. "Simulation of packed column jigging". Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=783.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains xiii, 131 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 61-64).
8
Maree, Westhein Bethren. "Froth flotation of an Nkomati mineral ore using mixtures of thiol collectors". Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2512.
Testo completoAbstract (sommario):
Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.Nickel, a valuable base metal, is the predominant product from the Nkomati mine in South Africa. High-grade nickel mineral ores (2%) from the Massive Sulphide Body have been depleted leaving those of low grade (0.3%). The beneficiation of this ore presents a challenge to the minerals processing industry. In response, batch froth flotation tests were used to explore the effects of mixtures of potassium amyl xanthate (PAX) and IPETC (Isopropyl ethyl thionocarbamate) on the grades and recoveries of nickel. In the mixtures, the xanthate accounted for 95.5, 90, 85 and 80 mole% respectively. Generally an increase in the nickel grade and recovery was observed with the mixtures relative to PAX. IPETC gave a significant increase in the cumulative water recovery with a significant decrease in cumulative nickel grade relative to PAX. PAX gave the highest cumulative nickel grade for the singular collector tests (1.9%), while obtaining the lowest cumulative recovery (77%). Out of the collector mixtures, mixtures 85% PAX: 15% IPETC and 90% PAX: 10% IPETC produced the joint highest cumulative grades (1.8%). These mixtures both gave recoveries of 82%. Collector mixture 95.5% PAX: 4.5% IPETC gave the second highest grade (1.7%) and the highest nickel recovery (85%). Although there were differences in the cumulative nickel grades and recoveries there were statistically no significant improvements observed with the use of the mixtures of PAX and IPETC in comparison to the industry mixture (95.5% SIBX: 4.5% IPETC). Tests were performed using the three best performing collector mixtures at molar dosages of 1.3, 0.65 and 0.325mmol/t. The highest cumulative nickel grades were obtained at the lowest collector dosages (at a molar dosage of 0.325mmol/t of 95.5% SIBX: 4.5% IPETC) with collector mixture 95.5% PAX: 4.5% IPETC being the most selective with a nickel grade of 2%. It was also observed that an increase in collector dosage, generally increased the cumulative nickel recovery with collector mixture 95.5% PAX: 4.5% IPETC at a molar dosage of 1.3mmol/t gave the highest cumulative recovery out of the tested mixtures (85%). The study also indicated that an increase in selectivity (i.e. cumulative grade) was at the expense of cumulative recovery. With a decrease in dosage, there was no significant improvement in the cumulative nickel grade and recovery for the tested mixtures compared to the industry mixture. There was however a significant decrease in the water recoveries achieved with PAX and collector mixtures 95.5% PAX: 4.5% IPETC at a molar dosage of 1.3mmolg/t of as well as mixture 90% PAX: 10% IPETC at a molar dosage of 0.65mmol/t.
9
Vianna, Sérgio Maurício S. M. "The effect of particle size, collector coverage and liberation on the floatability of galena particles in an ore /". [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18153.pdf.
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10
Купин, А. И., e А. В. Азарян. "Обобщенный алгоритм принятия решений для 1 стадии рудообогатительной фабрики". Thesis, Издательство СумГУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/25231.
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11
Kloppers, Lourens Marthinus. "Froth flotation of a Merensky platinum bearing ore with various THIOL collectors and their mixtures". Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2481.
Testo completoAbstract (sommario):
Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.The Bushveld igneous complex in northern South Africa has the largest deposit of platinum group elements (PGE) in the world. In trace amounts, these are closely associated with base metal sulphides (BMS). Froth flotation is used to beneficiate these PGE ores. The process constitutes a bulk sulphide recovery. Improvement of recovery of the BMS is required to maximise the recovery of PGEs. The performance of the froth flotation process is largely dependent on the chemical additives used and these chemicals have been extensively studied. Mixtures of collectors are widely used in the flotation of sulphide and platinum group mineral (PGM) ores. A range of performance benefits for the use of mixtures over pure collectors have been observed on many systems. These include improved valuable metal grades and recoveries, lower reagent dosage requirements, improved rates of flotation and enhanced recovery of coarse particles. Improvements observed with mixtures of chemical reagent have been attributed to synergism; defined as the interaction of two or more agents to produce a combined effect greater than the sum of their individual effects. Synergism is highly desired in froth flotation. For this study, mixtures of thiol collectors were used in batch froth flotation tests in an attempt to identify synergism between the different collectors on flotation performance of a typical platinum ore from the Merensky reef. Flotation performance was evaluated in terms of grades and recoveries of copper and nickel, and the rate of metal flotation. Single thiol collectors of xanthate (SIBX), a dithiocarbamate (DTC) and a dithiophosphate (DTP) were evaluated to determine the effect of functional group on flotation performance. SIBX was then used in mixtures with both DTC and DTP at various molar ratios to establish whether synergism occurs between these collectors on this particular platinum ore. Molar ratios of 90:10, 80:20, 70:30 60:40 and 50:50 were considered with SIBX being the major component. Further tests were conducted with the addition of a carboxymethyl cellulose depressant to the collector mixtures.
12
Wanigasekara-Mohotti, Don Kripalath. "Optimisation for the synthesis of mineral processing flowsheets". Thesis, The University of Sydney, 1999. https://hdl.handle.net/2123/27597.
Testo completoAbstract (sommario):
‘Minerals’ is a heuristic—based computer aided design system that implements an evolutionary design methodology to synthesise mineral beneficiaring flowsheets. It has been under developement at the University of Sydney since the 1970s by various post graduate students under the guidance of Professor R. G. H. Prince. In its previous development phases, the models were improved and new process units added. As a consequence, the optimiser used by ‘Minerals’ was no longer able to function properly and a “make do” optimser was implemented.
13
Viljoen, Willemien. "Phase relations in the system Cu-Fe-Ni-S and their application to the slow cooling of PGE matte". Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-10132005-100921/.
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Van, Dyk Jacobus Philippus. "Process development for the production of beneficiated titania slag". Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-10122009-144157/.
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15
Luttrell, Gerald H. "Hydrodynamic studies and mathematical modeling of fine coal flotation". Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/49828.
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16
Latti, Anna Dewetia. "The textural effects of multiphase mineral systems in liberation measurement /". [St. Lucia, Qld.], 2006. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19407.pdf.
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17
Crane, Martin John, University of Western Sydney, of Science Technology and Environment College e of Science Food and Horticulture School. "Geochemical studies of selected base metal minerals from the supergene zone". THESIS_CSTE_SFH_Crane_M.xml, 2001. http://handle.uws.edu.au:8081/1959.7/232.
Testo completoAbstract (sommario):
Acid leaching of different natural chrysocolla samples under ambient conditions demonstrated that the chemical and chrystallographic inhomogenity significantly affects the rate and that it is virtually impossible to use the mineral as a model for the kinetics of hydrometallurgical processing of copper ores.Dissolution experiments, stability diagrams,and X-ray powder diffraction studies are undertaken and studied in this research and results are given.It is found that a complete solid solution series exists in Nature with most tungstenian wulfenites and molybdenum stolzites containing a range of compositions. The first occurrence of a molybdenum stolzite from Broken Hill, Australia, which also contains small amounts of chromium is noted.Raman microprobe spectroscopy has proven to be a very quick and effective non-destructive method for semi-quantitative analysis of the wulfenite-stolzite and powellite-scheelite solid-solution series and in detecting very small amounts of substituted chromate in wulfenite, stolzite and anglesiteDoctor of Philosophy (PhD)
18
Steinberg, W. S. "Development of a control strategy for the open slag bath furnaces at Highveld Steel and Vanadium Corporation Ltd". Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-07062009-115433.
Testo completo
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Jesus, Wanderson Grazielli Mendes de. "Análise do processo de adequação da usina de Conceição 1". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/180143.
Testo completoAbstract (sommario):
Esta dissertação está baseada no trabalho desenvolvido para adequar a usina de Conceição 1 (da Vale S.A.) para o processamento de itabiritos compactos e semi compactos, situada em Itabira-MG. Até 2014, a usina de Conceição 1 foi alimentada com hematitas e itabiritos friáveis e produzia cerca de 22 Mt/ano. Com o consumo progressivo das reservas de minérios friáveis, tornou-se necessário que a usina processasse minérios mais competentes e com menor teor de Fe: itabiritos compactos e semi compactos (40%Fe). Até então, este material era considerado estéril, uma vez que os circuitos de beneficiamento não possuíam capacidade para transformá-lo em concentrados, tendo em vista às exigências de mercado. Portanto, o principal objetivo deste trabalho foi analisar o processo de ramp-up para aumentar a capacidade de alimentação da planta para 34 Mt/ano. O dimensionamento dos equipamentos, desenho dos circuitos, bem como as premissas adotadas durante o projeto de adequação serão apresentados neste estudo. Comparando a curvas de ramp-up prevista à praticada, notou-se que houve perdas mássicas consideráveis. Dentre os principais fatores responsáveis, está a grande quantidade de materiais compactos alimentados à usina com granulometria e, talvez, dureza maior do que poderia ser previsto. Os teores de ferro na alimentação da flotação e a qualidade dos concentrados (sínter feed e pellet feed) mostraram-se um pouco abaixo, também, do previsto, porém satisfatórios A estratégia de divisão por fases teve forte impacto positivo, evitando perdas maiores, pois reduziu o número de dias de parada consideravelmente. O desenvolvimento do projeto, denominado FRAGCOM (fragmentação e cominuição), pode ter ajudado a revelar as soluções para os problemas encontrados: este visou a obter melhorias no processo de desmonte e, consequentemente, na cominuição. Os resultados analisados de alguns testes deste projeto mostraram que, na britagem, a usina atingiu maiores taxas de produtividade nesta ocasião. Dado que a britagem é o primeiro circuito de processamento (um gargalo), isto é um fator relevante. Para estes testes foi utilizada uma razão de carga maior no desmonte. Com esta e outras melhorias, uma maior quantidade de material compacto pôde ser processado. Por fim, os resultados mostraram que a falta de aderência da curva de produção prevista com respeito à praticada, deveu-se entre outros fatores, à maior dificuldade de alimentação do circuito de moagem, impactado pelo baixo rendimento operacional da britagem.This dissertation is based on the work developed to adapt the plant of Conceição 1 (Vale S.A.) to the processing of compact and semicompact itabirites, located in Itabira-MG, southeastern Brazil. Conceição 1 plant was fed with friable hematite and itabirite and produced 22 Mt/year) until 2014. With the progressive consumption of friable ore reserves, it became necessary to process more competent and lower grade ores: compact and semicompact itabirites. Until then, this material was considered waste, since the beneficiation circuits did not have the capacity to transform it into concentrates, especially regarding market requirements. Therefore, the main objective of this work was to analyze the ramp up process in order to fed 34Mt/year. The adopted strategies and their impacts on ramp up process to achieve the production rate were analyzed. Equipment scaling, circuit design, as well as, premises and tests, which were performed during the adaptation project, are presented in this study. Comparing the planned ramp-up curve to the implemented curve, it was noted considerable mass losses. The amount of compacts that fed the plant with particle size and perhaps hardness greater than could be predicted is among main responsible factors The content of Fe in the feed of the flotation and the quality of the concentrates (sinter feed and pellet feed) was a little lower than was expected, but satisfactory. The phasing strategy had a strong positive impact, avoiding greater losses, as it considerably reduced the number of shutdown days. The development of the FRAGCOM (fragmentation and comminution) project may have helped to reveal solutions to the encountered problems: this project aimed to improve the blasting process and, consequently, the comminution. The results of some tests of this project showed that the crushing achieved higher productivity rates at that time. Since crushing is the first processing circuit (a bottleneck), this is a relevant factor. For these tests, a higher blasting load ratio was used. With this and other improvements, a greater amount of compact material could be processed. Finally, the results suggested that the mass losses occurred greater difficulty in feeding the grinding circuit, impacted by the low operational efficiency of the crushing.
20
Du, Preez Rudolph C. "Effect of lime additions and bulk chromium content on chromium deportment in smelter matte-slag systems". Thesis, Stellenbosch : Stellenbosch University, 2010. http://hdl.handle.net/10019.1/17459.
Testo completoAbstract (sommario):
Thesis (MScEng) –Stellenbosch University, 2010ENGLISH 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.
21
Becker, Megan. "The mineralogy and crystallography of pyrrhotite from selected nickel and PGE ore deposits and its effect on flotation performance". Thesis, Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-09272009-100136/.
Testo completo
22
Santos, Joel Martins dos. "Comparação entre rotas tradicionais de beneficiamento de minérios para a concentração de alumínio metálico em escórias". Universidade Tecnológica Federal do Paraná, 2013. http://repositorio.utfpr.edu.br/jspui/handle/1/1481.
Testo completoAbstract (sommario):
A etapa final da reciclagem do alumínio, após coleta, classificação e limpeza é sua transformação em ligas comerciais através da fundição do metal reciclado e sua correção química. Um dos impactos relevantes deste processo é a geração de escórias que representa um dos principais fatores de custo. A escória é um subproduto que surge na superfície do metal líquido decorrente da sua oxidação, da presença de impurezas nas sucatas e da adição de sais fundentes. Normalmente são ricas em alumínio metálico sob a forma de pequenas gotículas que se aprisionam em seu interior e podem levar a perdas consideráveis de produtividade. Pelo seu conteúdo em alumínio metálico, essas escórias têm valor de mercado para as indústrias especializadas em sua recuperação, normalmente com técnicas piro metalúrgicas. Porém frações granulométricas finas, menores que 0,15 mm, trazem dificuldades para a recuperação do alumínio contido. Neste trabalho foram investigadas duas rotas tradicionais de beneficiamento de minérios para a avaliação da concentração de alumínio contido em escórias de alumínio: (I) atricionamento em tambor rotativo e (II) a britagem. Em ambas utilizou-se de uma sequência de operação auxiliar de separação granulométrica. Para comparar a eficiência entre as duas rotas verificou-se a concentração do alumínio presente em produtos granulométricos obtidos em ambas. Outro fator comparativo foi o indicador energético denominado WI (Work Index). Este parâmetro é característico da indústria de processamento mineral e representa a energia consumida pela técnica ou rota empregada. Para a caracterização do concentrado de alumínio nas duas rotas foram utilizadas técnicas por via úmida com medição de hidrogênio, fluorescência de raios-X e pirometria em forno a indução. As avaliações dos concentrados revelaram aumento do alumínio metálico contido à medida que ocorria a redução na granulometria do material potencializando sua recuperação.The final step of recycling aluminum, after collection, classification and cleaning is its transformation into commercial alloy using recycled metal and its chemical correction. One of the relevant impacts in this process is the creation of slags that represent one of the main cost factors. The slag is a byproduct that appears on the surface of liquid metal due to its oxidation, from the presence of impurities in the scraps and in addition of salts fluxes. Usually they are rich in metallic aluminum in the form of small droplets which are captured inside and can lead to a considerable loss of productivity. By its content in metallic aluminum, these slags have market value for industries specialized in recovery, usually with pyrometallurgy technique. However slim granulometries fractions, smaller than 0.15 mm, bring difficulties for the recovery of aluminum contained. This paper investigated two traditional routes of ore improvement in order to evaluate the concentration of the aluminum contained into the aluminum slags: (I) attrition in tumbling barrel and (II) crushing. In both were used a sequence of auxiliary operation for granulometric distribution. In order to compare its efficiency between the two routes it was verified, in both, the concentration of aluminum present into the granulometric products obtained. Another comparative factor was the energetic indicator denominated by WI (Work Index). This parameter is a characteristic from the industries of mineral processing and it represents the energy consumed by the techniques or routes applied. For the characterization of concentrated aluminum on the two routes techniques used were wet-way with measurement of hydrogen, x-ray fluorescence and induction furnace pyrometry. The evaluation for the concentrated revealed an increase of metallic aluminum contained as occurred into the particle size reduction of the enhacing material in its recovery.
23
Groenewald, Jacobus Willem de Villiers. "Modelling and control of an autogenous mill using a state space methodology and neural networks". Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52940.
Testo completoAbstract (sommario):
Thesis (MScEng)--University of Stellenbosch, 2002.ENGLISH ABSTRACT: Metallurgical processes are often high dimensional and non-linear making them difficult to understand, model and control. Whereas the human eye has extensively been used in discerning temporal patterns in historical process data from these processes, the systematic study of such data has only recently come to the forefront. This resulted predominantly from the inadequacy of previously used linear techniques and the computational power required when analysing the non-linear dynamics underlying these systems. Furthermore, owing to the recent progress made with regard to the identification of non-linear systems and the increased availability of computational power, the application of non-linear modelling techniques for the development of neural network models to be used in advanced control systems has become a potential alternative to operator experience. The objective of this study was the development ofa non-linear, dynamic model of an autogenous mill for use in an advanced control system. This was accomplished through system identification, modelling and prediction, and application to control. For system identification, the attractor was reconstructed based on Taken's theorem making use of both the Method Of Delays and singular spectrum analysis. Modelling consisted of the development of multi-layer perceptron neural network, radial basis function neural network, and support vector machine models for the prediction of the power drawn by an autogenous mill. The best model was subsequently selected and validated through its application to control. This was accomplished by means of developing a neurocontroller, which was tested under simulation. Initial inspection of the process data to be modelled indicated that it contained a considerable amount noise. However, using the method of surrogate data, it was found that the time series representing the power drawn by the autogenous mill clearly exhibited deterministic character, making it suitable for predictive modelling. It was subsequently found that, when using the data for attractor reconstruction, a connection existed between the embedding strategy used, the quality of the reconstructed attractor, and the quality of the resulting model. Owing to the high degree of noise in the data it was found that the singular spectrum analysis embeddings resulted in better quality reconstructed attractors that covered a larger part of the state space when compared to the method of delays embeddings; the data embedded using singular spectrum analysis also resulting in the development of better quality models. From a modelling perspective it was found that the multi-layer perceptron neural network models generally performed the best; a multi-layer perceptron neural network model having an appropriately embedded multi-dimensional input space outperforming all the other developed models with regard to free-run prediction success. However, none of the non-linear models performed significantly better than the ARX model with regard to one-step prediction results (based on the R2 statistic); the one-step predictions having a prediction interval of 30 seconds. In general the best model was a multi-layer perceptron neural network model having an input space consisting of the FAG mill power (XI), the FAG mill load (X2), the FAG mill coarse ore feed rate (X3), the FAG mill fine ore feed rate (X4), the FAG mill inlet water flow rate (X7) and the FAG mill discharge flow rates (X9, XIO). Since the accuracy of any neural network model is highly dependent on its training data, a process model diagnostic system was developed to accompany the process model. Linear principal component analysis was used for this purposes and the resulting diagnostic system was successfully used for data validation. One of the models developed during this research was also successfully used for the development of a neurocontroller, proving its possible use in an advanced control system.
AFRIKAANSE OPSOMMING: Metallurgiese prosesse is gewoonlik hoogs dimensioneel en nie-lineêr, wat dit moeilik maak om te verstaan, modelleer, en te beheer. Alhoewel die menslike oog alreeds wyd gebruik word om temporale patrone in historiese proses data te onderskei, het die sistematiese studie van hierdie tipe data eers onlangs na vore gekom. Dit is hoofsaaklik na aanleiding van die onvoldoende resultate wat verkry is deur van voorafgaande lineêre tegnieke gebruik te maak, asook die beperkende berekenings vermoë wat beskikbaar was vir analise van onderliggend nie-lineêre dinamiese stelsels. 'n Verder bydraende faktor is die onlangse vordering wat gemaak is met betrekking tot die identifikasie van nie-lineêre stelsels en die toename in beskikbaarheid van rekenaar-vermoë. Die toepassing van nie-lineêre modellerings tegnieke vir die ontwikkeling van neurale netwerke om gebruik te word in gevorderde beheerstelsels, het 'n potensiële alternatief geword tot operateur ondervinding. Die doelwit van hierdie studie was die ontwikkeling van 'n gevorderde beheerstelsel vir 'n outogene meul gebaseer op 'n nie-lineêre, dinamiese model. Dit is bereik deur middel van stelsel-identifikasie, modellering en voorspelling, en laastens implementering van die beheerstelsel. Vir stelsel-identifikasie is die attraktor van die stelsel bepaal soos gebaseer op Taken se teorema deur gebruik te maak van beide die metode van vertraging en enkelvoudige spektrum analise. Modellering van die stelsel vir die voorspelling van krag-verbruik deur die outogene meul het bestaan uit die ontwikkeling van multilaag-perseptron-neurale netwerke, radiaalbasisfunksie-neurale netwerke, en steunvektor-masjien-modelle. Die beste model is daarna gekies vir validasie deur middel van toepassing vir beheer. Dit is bereik deur 'n neurobeheerder te ontwikkel en te toets deur middel van simulasie. Die aanvanklike inspeksie van proses data wat gebruik sou word vir modellering het egter getoon dat die data 'n aansienlike hoeveelheid geraas bevat. Nietemin, deur die gebruik van 'n surrogaat-data-metode, is dit bevind dat die tyd-reeks wat die krag verbruik van die outogene meul beskryf, duidelik deterministiese karakter toon en dat dit dus wenslik is om 'n nie-lineêre voorspellings-model, soos 'n neurale netwerk te gruik. Gevolglik is gevind dat, wanneer die data vir attraktor hersamestelling gebruik word, 'n verband bestaan tussen die ontvouing-strategie wat gebruik word, die kwaliteit van die gerekonstrueerde attraktor, en die kwaliteit van die daaropvolgende model. As gevolg van die geraas in die data is gevind dat die ontvouing gebaseer op enkelvoudige spektrum analise 'n beter kwaliteit attraktor hersamestelling lewer. So ook is gevind dat 'n groter deel van die toestandruimte gedek word in vergelyking met die metode van vertraging-ontvouing. Deur gebruik te maak van enkelvoudige spektrum-analise, het die dataontvouing ook beter kwaliteit modelle opgelewer. Vanuit 'n modellerings-perspektief is gevind dat die multilaag-perseptron-neurale netwerk-modelle in die algemeen die beste gevaar het. 'n Multilaag-perseptronneurale netwerk met 'n gepaste ontvoude multidimensionele invoer-spasie het die beste gevaar van al die ontwikkelde modelle met betrekking tot vryloopvoorspellings. Geen van die nie-lineêre modelle het egter beduidend (op 'n R2 basis) beter gevaar as die ARX model wanneer daar na die eenstap-voorspellings (oor 'n 30 sekonde interval) gekyk word nie. Die multilaag-perseptron-neurale netwerk met 'n invoer-spasie bestaande uit die meul krag-verbruik (XI), die meullading (X2), die meul growwe-erts voertempo (X3), die meul fyn-erts voertemp ('4), die meul inlaat-water vloeitempo (X7) en die meul uitlaat vloeitempo's (X9, XIO) het in die algemeen die beste gevaar. Aangesien die akkuraatheid van emge neurale netwerk afhanklik is van die data waarmee dit aanvanklik opgestel is, is 'n diagnostiese proses modelontwikkel om die proses-model te vergesel. Lineêre hoofkomponent analise is vir hierdie doel aangewend en die gevolglike diagnostiese stelsel is suksesvol aangewend vir datavalidasie. Een van die modelle ontwikkel gedurende hierdie navorsing is ook suksesvol gebruik vir die ontwikkeling van 'n neurobeheerder wat dien as bewys dat die model goed gebruik kan word in 'n gevorderde beheerstelsel.
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Coetzee, Lodewicus Charl. "Robust nonlinear model predictive control of a closed run-of-mine ore milling circuit". Thesis, Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-09272009-103725/.
Testo completo
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Crane, Martin John. "Geochemical studies of selected base metal minerals from supergene zone /". View thesis, 2001. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030721.132607/index.html.
Testo completoAbstract (sommario):
Thesis (PhD) -- University of Western Sdyney, 2001."A thesis presented in accordance with the regulations governing the award of the degree of Doctor of Philosophy, University of Western Sydney" "November 2001" Bibliography: leaves 249 - 254.
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Swanepoel, Francois. "Estimation of particle size distributions in mineral process systems using acoustic techniques". Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51746.
Testo completoAbstract (sommario):
Thesis (MEng)--Stellenbosch University, 2000.ENGLISH ABSTRACT: A desire to increase the efficiency of the comminution process in mineral process systems has led to the need of determining the size distribution of ore particles at various stages in the system. The objective of this research is to investigate the feasibility of the use of an acoustic sensor for measuring particle size distribution. The acoustic signal generated when the particles impact on a cantilever bar is analysed using digital signal processing techniques. As rocks fall onto a metal bar, the bar vibrates. The vibrations contain information th a t is extracted to determine the size of particles tha t impacted on the bar. The bar is modelled as a linear system which is excited by impulses (impact of particles). The response of the bar is deconvolved from the acoustic signal to obtain an impulse whose amplitude is proportional to the energy of the impact. In order to improve size estimates, deconvolution is performed using a statistical model of the impulse sequence (Bernoulli-Gaussian) and then estimated using MAP estimation. Size estimates are not only a function of the mass of particles, but also on the exact position of impact on the bar. Since there is always a variation in the position of impact, size estimates are erroneous. It was found that the position of impact can be determined as to reduce variances dramatically. Due to physical sampling in space, the sensor has a bias towards larger particles. We show how this can be represented mathematically and removed. This project is mainly concerned with rocks in the +8-25mm (+0,7-22 gram) size range.
AFRIKAANSE OPSOMMING: Vergruising van erts in die mineraalbedryf verg groot hoeveelhede energie. Daar is ’n behoefte gei'dentifiseer orn hierdie proses meer effektief te maak. Aangesien die effektiwiteit van ’n meul ’n funksie is van die ertsgroottes wat gemaal word, kan partikel grootte inligting aangewend word om effektiwiteit te bevorder. Die doel van hierdie tesis is om die lewensvatbaarheid van ’n akoestiese sensor vir die doel van partikelgrootte estimasie, te ondersoek. Erts partikels wat val vanaf ’n vervoerband op ’n kantelbalk, veroorsaak dat die balk vibreer. Deur hierdie vibrasies te meet en verwerk, kan inligting aangaande partikel grootte verkry word. Die stelsel word gemodelleer as ’n lineere sisteem met impulse as intree. Die geobserveerde sein is die konvolusie tussen die intree impulse en die impulsweergawe van die sisteem. Deur gebruik te maak van ’n statistiese model en MAP-estimasie, word die effek van die sisteem gedekonvuleer vanaf die geobserveerde sein om ’n benadering van die intree impuls sein te verkry. Die amplitudes van die impulse word gebruik as ’n aanduiding van partikel massa. Partikelgroottes soos benader deur die stelsel, is ’n funksie van die die posisie waar die partikel die balk tref. Deur van patroonherkenning tegnieke gebruik te maak, word die posisie van impak bepaal om sodoende grootte benaderings aan te pas en die variansie van grootte verspreidings te verminder. As gevolg van die feit dat partikels gemonster word deurdat slegs ’n klein persentasie van die hele omvang van partikels ondersoek word, onstaan daar ’n oorhelling ( “bias” ) na groter partikels. Die kans dat groter partikels die balk tref is groter as vir klein partikels. ’n Wiskundige model vir hierdie verskynsel word voorgestel en gewys hoe die die oorhelling geneutraliseer kan word. Hierdie projek het te doen met ertsgroottes +8-25mm (+0,7-22 gram).
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Andrews, Lesley. "Base metal losses to furnace slag during processing of platinum-bearing concentrates". Diss., Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-01222009-172643/.
Testo completo
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Deursen, Caio Moreira Van. "Métodos de desaguamento e disposição de rejeito da bauxita: estudo de caso e avaliação econômica". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3134/tde-23022017-103826/.
Testo completoAbstract (sommario):
Cerca de 230 milhões de toneladas de bauxita são produzidas por ano e, destas, 60 milhões são provenientes de operações que beneficiam esta bauxita usando água como meio para separar as frações mais finas. Como consequência do beneficiamento, estima-se que mais de 25 milhões de toneladas de rejeito sejam dispostas todo ano. Estas frações têm grandes quantidades de caulinita, um argilomineral de difícil desaguamento. Estes sólidos estão tipicamente em uma suspensão com água a cerca de 15% de concentração em massa antes de operações de desaguamento. As formas de desaguamento variam, bem como as opções de disposição. Este texto discorre sobre opções de desaguamento como sedimentação natural, espessamento, filtragem e centrifugação. Também se discorre sobre alternativas de disposição. Estas são condicionadas pela concentração de sólidos do material a ser disposto e são a disposição hidráulica em diques ou reaterro na mina. Após a descrição de cada uma das alternativas, são feitas análises de combinações destas formas de desaguamento e disposição, além de uma avaliação do fluxo de caixa livre descontado acumulado para cada uma. Esta abordagem, feita para um caso específico, permite avaliar qual opção implica em menor despesa financeira para a operação. Foram feitas considerações para avaliar características não econômicas de cada uma das operações, como o consumo de água, área ocupada pelo depósito, perigos de cada opção e seus descomissionamentos. A opção que apontou menor desembolso no período da operação, bem como a minimização de perigos, é o desaguamento com centrífugas e disposição do material reaterrando áreas lavradas.More than 230 million tonnes of bauxite are produced each year and, from these, nearly 60 million come from operations that use water to beneficiate the ore, separating the finer fractions. By reason of this mineral treatment, it is estimated that more than 25 million dry tonnes of reject are disposed each year. The finer fractions have high kaolinite concentrations, a challenging to dewater mineral. These solids are typically in a suspension with about 15% solids concentration in mass before any dewatering. Both the dewatering options and disposal possibilities may vary. This text discusses dewatering options such as natural settling, thickening, filtering and centrifugation. It also describes alternatives of disposing the material. These options depend on the water concentration and consist of hydraulic disposition or using the dewatered material as mine backfill. After describing each alternative, an analysis of possible combinations among those is made along with an accumulated discount free cash flow evaluation for each one. Considerations were made to evaluate non-economic characteristics of each operation including the water consumption, surface occupied, operational hazards, decommissioning and closure. The option that has shown the lowest cost during the life of the operation, simultaneously reducing operational hazards is dewatering with centrifuges and using the material as backfill in mined out areas.
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Убай, Юсеф Саламах Аль Мададха, Юсеф Саламах Аль Мададха Убай e Jusef Salamakx Al Madadkha Ubay. "Автоматичний контроль ступеня здрібнення руди в технологічних комплексах флотаційного та магнітного збагачення". Thesis, Видавництво НГУ, 2010. http://ir.nmu.org.ua/handle/123456789/90.
Testo completoAbstract (sommario):
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.13.07 – Автоматизація процесів керування. Національний гірничий університет. Дніпропетровськ, 2010Диссертация на соискание ученой степени кандидата технических наук по специальности 05.13.07 – автоматизація процессов управления. Национальный горный університет. Днепропетровск, 2010
Dissertation on scientific degree of Candidate of Technical Science on specialty 05.13.07 – Automation of processes of commanded. – National Mining University, Dnipropetrovsk, 2010
Дисертація присвячена вирішенню актуальної науково-технічної проблеми автоматичного контроля ступеня здрібнення руди в технологічних комплексах флотаційного та магнітного збагачення на основі встановлення нових закономірностей розділення та кореляції продуктів здрібнення руди у робочих зонах збагачувальних апаратів та використання промислових флотаційних машин та магнітних сепараторів як природних аналізаторів ступеня здрібнення руди. Науково обґрунтовані функціонально-алгоритмічні структури та технічні вимоги до систем автоматичного контролю ступеня здрібнення руди та до систем автоматичного управління технологічними комплексами флотаційного та магнітного збагачення. Результати роботи впроваджені в проект і можуть бути використані на флотаційних та магнітозбагачувальних фабриках руд кольорових та чорних металів.
Решена актуальная научно-техническая задача научного обоснования метода автоматического контроля степени измельчения руд черных и цветных металлов, а именно недоизмельчения, оптимального измельчения и переизмельчения руд при их обогащении на основании косвенной оценки степени раскрытия минералов, что позволило разработать функционально-алгоритмические структуры систем автоматической оптимизации процессов измельчения и классификации руд, повышающие эффективность процесса обогащения. Это позволило повысить извлечения металлов в концентраты, повысить металлургическую ценность концентратов руд черных и цветных металлов. Предложен новый критерий оптимизации процессов измельчения и классификации руды – минимум коэффициента корреляции между массовыми долями металла в концентрате и хвостах обогатительного аппарата, который предложено использовать в качестве анализатора раскрытия руды. Получены новые уравнения регрессии связующие критерии эффективности разделения при обогащении руд и коэффициент корреляции между массовыми долями металла в концентрате и хвостах обогатительного аппарата, что позволяет обосновать новый критерий автоматической оптимизации процессов рудоподготовки и обогащения руд. Научно обоснованы технические требования к функционально-алгоритмическим структурам систем автоматического контроля и оптимизации крупности помола руды в цикле измельчения и классификации, что позволяет повысить извлечение металлов в концентраты руд черных и цветных металлов и их металлургическую ценность. Разработана система автоматического контроля массовой доли железа в хвостах магнитного сепаратора, которая прошла экспериментальные исследования в промышленных условиях. Точность контроля массовой доли железа составила менее 5%относительных единиц. Разработана система автоматического контроля степени измельчения железной руды, построенная на базе промышленного магнитного сепаратора. Выполнены сравнительные экспериментальные исследования системы автоматической оптимизации технологического комплекса флотационного обогащения медной руды в условиях горно-металлургического комбината «Эрдэнэт». Сравнивалась эффективность двух критериев оптимизации: максимальная производительность по готовому (– 0,074 мм) классу крупности продукта измельчения и предлагаемый критерий косвенной оценки раскрытия руды – минимум коэффициента корреляции между массовыми долями металла в концентрате и хвостах. Предложенный критерий оптимизации позволил повысить извлечение меди в концентрат на 6,07%, а извлечение молибдена на 10,09%. Выполнены сравнительные испытания предложенной автоматизированной системы автоматической оптимизации цикла измельчения железных руд по критерию минимума коэффициента корреляции между массовыми долями железа в концентрате и хвостах с системой автоматического регулирования массовой доли железа в концентрате магнитного сепаратора в условиях Лебединского ГОКа. Предложенная система повысила извлечение железа в концентрат на 7,2% относительных единиц и качество концентрата на 2,19%.
The dissertation is devoted to solving actual scientific problem of increasing efficiency of automated control of degree of ore grinding for optimizing of teсhnological complexes of flotation and magnetic concentration of ore by using industrial magnetic separator and flotation machine as technical means of automation and establishing new regularites of separation in working zones of separator. Technical requirement to the systems of automated control and optimization of technological complexes of flotation and magnetic concentration are established. Functional schemes of the systems of automated control and optimization of technological complexes of concentration are suggested. The results of experimental researches the systems of automated control and optimization have shown their efficiency.
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Mukepe, Kahilu Moise. "Identification and control of wet grinding processes: application to the Kolwezi concentrator". Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209562.
Testo completoAbstract (sommario):
Enhancing mineral processing techniques is a permanent challenge in the mineral and metal industry. Indeed to satisfy the requirements on the final product (metal) set by the consuming market, control is often applied on the mineral processing whose product, the ore concentrate, constitutes the input material of the extractive metallurgy. Therefore much attention is paid on mineral processing units and especially on concentration plants. As the ore size reduction procedure is the critical step of a concentrator, it turns out that controlling a grinding circuit is crucial since this stage accounts for almost 50 % of the total expenditure of the concentrator plant. Moreover, the product particle size from grinding stage influences the recovery rate of the valuable minerals as well as the volume of tailing discharge in the subsequent process.The present thesis focuses on an industrial application, namely the Kolwezi concentrator (KZC) double closed-loop wet grinding circuit. As any industrial wet grinding process, this process offers complex and challenging control problems due to its configuration and to the requirements on the product characteristics. In particular, we are interested in the modelling of the process and in proposing a control strategy to maximize the product flow rate while meeting requirements on the product fineness and density.
A mathematical model of each component of the circuit is derived. Globally, the KZC grinding process is described by a dynamic nonlinear distributed parameter model. Within this model, we propose a mathematical description to exhibit the increase of the breakage efficiency in wet operating condition. In addition, a relationship is proposed to link the convection velocity to the feed ore rate for material transport within the mills.
All the individual models are identified from measurements taken under normal process operation or from data obtained through new specific experiments, notably using the G41 foaming as a tracer to determine material transport dynamics within the mills. This technique provides satisfactory results compared to previous studies.
Based on the modelling and the circuit configuration, both steady-state and dynamic simulators are developed. The simulation results are found to be in agreement with the experimental data. These simulation tools should allow operator training and they are used to analyse the system and to design the suitable control strategy.
As the KZC wet grinding process is a Multi-Input Multi-Output (MIMO) system, we propose a decentralized control scheme for its simplicity of implementation. To overcome all the control issues, a Double Internal Model Control (DIMC) scheme is proposed. This strategy is a feedforward-feedback structure based on the use of both a modified Disturbance Observer (DOB) and a Proportional-Integral Smith-Predictor (PI-SP). A duality between the DOB and PI-SP is demonstrated in design method. The latter is exploited to significantly simplify the design procedure. The designed decentralized controllers are validated in simulation on the process linearized model. A progressive implementation of the control strategy is proposed in the context of the KZC grinding circuit where instrumentation might not be obvious to acquire./
Améliorer les techniques de traitement de minerais est un défi permanent dans l'industrie des minéraux et des métaux. En effet, pour satisfaire aux exigences du produit fini (métal ) fixées par le marché de consommation, la commande automatique est souvent appliquée à l'usine du traitement de minerais dont le produit, le concentré, constitue la matière première de la métallurgie extractive. Une attention particulière est donc dévolue aux unités de traitement de minerais et en particulier aux concentrateurs. Comme le processus de réduction des dimensions granulométriques du minerai est l'étape critique d'un concentrateur, il s'avère que la commande d'un circuit de broyage est cruciale, car ce stade représente près de 50 % des dépenses totales de l' usine de concentration. De plus, la dimension granulométrique du produit de l'étape de broyage influe sur le taux de récupération des minéraux utiles ainsi que sur le volume des rejets du processus ultérieur.
La présente thèse porte sur une application industrielle, à savoir le concentrateur de Kolwezi (KZC qui est un circuit de broyage humide à double boucle fermée. Comme tout processus industriel de broyage humide, ce procédé présente une problématique de commande complexe et difficile en raison de sa configuration et des exigences relatives aux caractéristiques du produit. En particulier, nous nous intéressons à la modélisation de ce procédé et à proposer une stratégie adéquate de commande dans le but de maximiser le débit de production tout en respectant les exigences quant à la finesse et à la densité de la pulpe produite.
Un modèle mathématique de chaque composant du circuit a été déterminé. Globalement, le processus de broyage de KZC est décrit par un modèle dynamique non linéaire à paramètres distribués. Dans ce modèle, une description mathématique de l'augmentation de l'efficacité du broyage en milieu humide est proposée. En outre, nous avons proposé une relation liant la vitesse de convection au débit d'alimentation de minerais dans le modèle du transport de la matière à l'intérieur des broyeurs.
Tous les modèles mathématiques ont été identifiés à partir de mesures prises sur le procédé en fonctionnement d'équilibre stable ou à partir des données obtenues grâce à des nouvelles expériences spécifiques, notamment en utilisant le moussant G41 comme traceur pour déterminer la dynamique de transport de la matière dans les broyeurs. Cette technique a produit des résultats cohérents par rapport aux études antérieurs réalisées au moyen du traceur colorant ou radioactif.
Les simulateurs statique et dynamique ont été développés sur la base de la modélisation mathématique et de la configuration du circuit. Les résultats des simulations sont en accord avec les données expérimentales. Ces outils de simulation devraient permettre la formation des opérateurs et ont été utilisés pour analyser le système et concevoir la stratégie de commande la plus appropriée.
Comme le processus de broyage humide de KZC est un système à plusieurs grandeurs d'entrée et plusieurs grandeurs de sortie, nous avons proposé une structure de commande décentralisée en raison de sa simplicité de mise en œuvre .Afin de surmonter tous les problèmes de commande, un schéma de commande à double modèle interne (CDMI) est proposée. Cette stratégie est une structure à anticipation - rétroaction basée sur l'utilisation d'un observateur de perturbations (OBP) et d'un Prédicteur de Smith doté d'un régulateur Proportionnel-Intégral (PS-PI). Une dualité entre l'OBP et le PS-PI est démontrée dans la méthode de conception. Cette propriété est exploitée pour simplifier considérablement la procédure de conception. Les régulateurs décentralisés ainsi conçus sont validés en simulation sur le modèle linéarisé du procédé. Une mise en œuvre progressive de la stratégie de commande est proposée dans le contexte du circuit de broyage de KZC où l'instrumentation peut ne pas être évidente à acquérir.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
31
Ford, Merrill Anthony. "Simulation of ore dressing plants". Thesis, 2015. http://hdl.handle.net/10539/16662.
Testo completo
32
Makhula, Mpho Johanna. "Beneficiation of fine ores using the Longi wet high magnetic separator". Thesis, 2014. http://hdl.handle.net/10539/18081.
Testo completoAbstract (sommario):
Magnetic separation has been used since 1955 for processing a variety of minerals from iron
ore in steel production to the desulphurisation of coal. The accumulation of such fines and
slimes during mining operations and the increasing global demand for quality products
motivated the use of the semi-continuous pilot wet high intensity magnetic separator
(WHIMS) introduced in 2008. Its unique features were considered to be favourable for
beneficiating a Sishen low grade hematite-rich ore and an ash-rich Witbank coal.
An automated Mineral Liberation Analyser (MLA) was used to characterise the size
distribution of the hematite-rich material thereby providing an estimated grade at the same
time. This type of analysis characterises mineral types in terms of particle size and elemental
composition, specific density, weight percent, area of particle, particle shape, circularity and
equivalent circle diameter. However, for this research study only size and elemental
composition were considered.
The application of the Longi LGS 500 WHIMS for beneficiating a low grade South African
iron ore material was investigated by determining the effects of changing the operating
parameters of pulp solids, magnetic field intensity and the pulsation frequency. This was
followed by a 33 full factorial design which consisted of twenty seven (27) test matrix, with
mass yield of concentrate and Fe grade selected as the main responses to the changing of the
parameters. The results obtained were validated using the analysis of variance (ANOY A) and
the mathematical model, which showed the variables as being significant to the investigation
process, thus rejecting the null hypothesis. The significance of the variables was in the order
of magnetic field intensity followed by pulsation frequency and lastly the percentage pulp
solids. The model predictions and actual data were in good agreement, reporting regression
coefficients ranging between 0.83 and 0.94. It was shown that a single stage magnetic
separation has the potential to produce a 55% Fe product.
33
Ross, Edwin Harm. "Measurement by use of the rotating cylinder technique of the rate of the solution of Winterveld chromite ore in slag". Thesis, 2015. http://hdl.handle.net/10539/19232.
Testo completo
34
Steenkamp, Joalet Dalene. "Beneficiation of an ilmenite waste stream containing undesirable levels of chromite". 2003. http://upetd.up.ac.za/thesis/available/etd-09232008-121624.
Testo completo
35
Sekgarametso, Katlego. "Flotation of non-sulphide PGM ores - Optimization of flotation reagent suite and conditions". Thesis, 2018. https://hdl.handle.net/10539/27276.
Testo completoAbstract (sommario):
A dissertation submitted to the faculty of Engineering and the Built Environment,
University of Witwatersrand, Johannesburg, in fulfilment of the requirements for
the degree of Master of Science in Engineering
November 2018The aim of this study is to improve the flotation of non-sulphide PGM ores from the Mimosa Mine in the Great Dyke of Zimbabwe by evaluating a variety of collector reagents that have not been tested on such material before and applying a full factorial experimental design to investigate the effects of the main primary collector, co-collector and depressant on PGM recovery and grade. The mineralogical studies by XRD revealed that the non-sulphide PGM ore had substantial amounts of gangue material, comprising of 45% quartz, 21% chabazite and 33% of magnetite. The ICP-OES analysis showed that this particular non-sulphide PGM ore is a low-grade ore with an average 4E head assays of 2.37ppm. In the preliminary flotation stage, three reagent suites made up of (i) a collector, (ii) a co-collector and (iii) a depressant i.e. (SIBX, DTP, M98B); (SIBX, C7133, M98B) and (SIBX, AM810, M98B) respectively were tested. It was observed that (SIBX, AM810, M98B) reagent suite gave the best performance with respect to both recovery and grade of the PGM concentrate from the ore. Attempts were made to optimize the dosage levels of the 3 reagents. The optimization studies revealed that 78.5% Pt and 69.3% Pd can be recovered at grades of 17.90g/t Pt and 9.44g/t Pd respectively. This represents a significant upgrade for the roughing stage from the 1.42g/t Pt and 0.85g/t Pd in the feed. These results were obtained at optimized dosages of 86g/t SIBX and 80g/t AM810, with depressant M98B at 50g/t. The observations from the experiments indicated that recovery of PGEs was on the upward trend as the dosage of hydroxamate was increasing hence the effect of the hydroxamate co-collector was further tested at higher dosages while fixing SIBX at 100g/t. The experiments were carried out using 50g/t, 60g/t, 70g/t and 80g/t hydroxamate (AM810) with the depressant M98B at 50g/t. It was observed that the Pt recovery only increased slightly with increasing hydroxamate (AM810) dosage.
E.R. 2019
36
Steenkamp, J. D. (Joalet Dalene). "Beneficiation of an ilmenite waste stream containing undesirable levels of chromite". Diss., 2003. http://hdl.handle.net/2263/28141.
Testo completoAbstract (sommario):
Please read the abstract in the section, 00front, of this document (Role and responsibility of the author)Dissertation (MEng)--University of Pretoria, 2008.
Materials Science and Metallurgical Engineering
unrestricted
37
Grey, IE. "Applications of solid state chemistry to minerals and mineral processing". Thesis, 2003. https://eprints.utas.edu.au/20005/13/Grey_thesis_front_matter.pdf.
Testo completoAbstract (sommario):
Throughout his career, a consistent aim of the candidate's research has been to apply the methods of solid state chemistry to solve metallurgical and mineral processing problems, while maintaining and developing his disciplinary skills and techniques. The work has thus involved parallel inputs to fundamental research and to applied research for mining and manufacturing companies.
The candidate's scientific specialisation is in crystallography and phase equilibria. In crystallography he has worked on the determination of the structures of complex minerals and synthetic materials and the elucidation of structural principles relating different structure types. The structures are often complicated by problems such as microdomain formation, pseudosymmetry, metamictisation and diffuse diffraction effects due to short range order and the candidate has developed expertise in solving and refining such structures, where conventional methods cannot be applied. In phase equilibria studies he has specialised in the determination of high temperature solid/gas phase relations in systems involving elements in different oxidation states. He has developed appropriate experimental procedures involving controlled gaseous atmospheres and microbalance techniques and has applied these techniques to reactions of industrial importance.
The attached list of publications reflects the candidate's specialised expertise in the fields of crystallography and phase equilibria. The publications can be grouped into three main categories:
1. Postgraduate and postdoctoral research (and ongoing collaboration).
2. Structure systematics in mineral and synthetic systems.
3. Fundamental support for mineral processing projects.
38
Tom, Phakamile. "Optimization of dense medium cyclone plant for the beneficiation of low grade iron ore with associated high proportion of near-density material at Sishen Iron Ore Mine". Thesis, 2016. http://hdl.handle.net/10539/20042.
Testo completoAbstract (sommario):
A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the Degree of Master of Science in Engineering (Metallurgy and Materials Engineering) July 2015The research report is premised on three aspects which are critical in the heavy mineral beneficiation. These aspects are classified as (i) understanding the densimetric profile of the available ore body, (ii) understanding the properties of the heavy medium utilised at the plant to beneficiate the ore, and (iii) the automation and modelling of the processing plant in order to maximise plant efficiency. Ore characterisation is mainly focused on understanding the densimetric profile of the ore body, in order to determine the probability of producing a saleable product as well as predicting the expected yields and quality. This is done to utilise the endowment entrusted upon the operating entity by the government and shareholders to treat the mineral resource to its full potential. Understanding of the beneficiation potential of the ore body will assist the mine planning and processing plant to optimise the product tons and quality. This will ensure the marketing plans are in accordance with the expected product as beneficiation will vary depending on the mining block reserves. The mining blocks have potential to produce varying product grades with different recoveries. Ore characterisation was conducted on the GR80 mining block, low-grade stockpiles (i.e. C-grade ore reserves & Jig discard and dense medium separation (DMS) run-of-mine (ROM) material. The GR80 material was characterised as having low proportion of near-density material and would be easy to beneficiate as well as produce high volumes of high grade product. Furthermore, it was revealed that the 2014 DMS ROM had an increased proportion of low-density material; however this material was also had low proportion of near-density material. The low-grade stockpiles was characterised by high proportion of near density material, which necessitate the beneficiation process to operate at high density in excess of 3.8 t/m3. Maintaining a higher operating density requires more dense medium which leads to viscosity problems and impact performance. The characterisation of the FeSi medium was imperative to understand its behaviour and potential influence on beneficiation of low-grade stockpiles and mining blocks with elevated proportion of near-density material. As the proportion of near-density waste material increases in the run-of-mine (ROM), it is necessary to beneficiate the material at elevated operating medium densities. However, when cyclones are operated at high densities, the negative influence of the medium viscosity becomes more apparent and thus influences the separation efficiency. Heavy medium, ferrosilicon (FeSi) characterisation looked at identifying the effects of viscosity on the FeSi stability and whether there would be a need for a viscosity modifier. Thus, the importance of controlling the stability, viscosity, and density of the medium cannot be under-estimated and can very often override the improvements attainable through better designs of cyclones. Furthermore, the slurry mixture of the heavy medium utilised for the purpose of dense medium separation should be non-detrimental to the effectiveness of separation in the DMS Fine cyclone plant. Medium characterisation showed that removal of ultra-fines leads to unstable media as indicated by faster settling rates. This would result in medium segregation in the beneficiation cyclone thereby leading to unacceptable high density differential which will negatively impact the cut-point shift and cause high yield losses to waste. The overall control of the metallurgical processes at Sishen’s Cyclone Plant is still done on manually and thus operation still varies from person-to-person and/or from shift-to-shift. This result in some of the process data and trends not being available online as well as being captured inaccurately. Furthermore, this negatively affects the traceability and reproducibility of the production metallurgical key performance indicators (KPI’s) as well as process stability and efficiency. It has been demonstrated that real-time online measurements are crucial to maintaining processing plant stability and efficiency thereby ensuring that the final product grade and its value is not eroded. Modelling and automation of the key metallurgical parameters for the cyclone plant circuit was achieved by installation of appropriate instrumentation and interlocking to the programmable logic control (PLC). This allowed for the control of the correct medium sump level, cyclone inlet pressure, medium-to-ore ratio as well as online monitoring of density differential as “proxy” for medium rheological characteristics. The benefit of modelling and simulation allows the virtual investigation and optimisation of the processing plant efficiency as well as analysis of the impact of varying ore characteristics, throughput variations and changing operating parameters. Therefore it is imperative that all cyclone operating modules are operated at the same efficiency which can be achieved by optimized process through proper automation and monitoring, thereby improving the total plant profitability. Keywords: dense medium separation; densimetric profile; dynamic modelling; FeSi rheology; iron-ore beneficiation; process automation; process control.
39
Craig, Ian Keith. "Robust controller specification and design for a run-of-mine milling circuit". Thesis, 1993. https://hdl.handle.net/10539/24289.
Testo completoAbstract (sommario):
A thesis submitted to the Faculty of Engineering, University of the Witwatersrand,
Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy.A new approach to the problem ofdesigning a control system for a run-of-mine (ROM) milling circuit is described. The ROM mill control problem is formalized in terms or a general linear system synthesis and analysis framework. Using this framework, u-synthesis and analysis is applied to a model of an industrial ROM milling circuit. The milling circuit uncertainty structure is obtained from plant perturbation tests. Correlations of plant parameter uncertainties and the choice of the location of uncertainty weights within the plant transfer function matrix structure, are discussed. Some comments are made as to possible sources of the plant uncertainties, and practical measures that can be taken to minimize them. The choice of performance weighting functions is discussed with regard to the economic and process-related importance of each plant output and issues of implementation such as the sampling rate to be used. A u-controller is obtained which provides robust performance in the face of significant model uncertainties. This controller is tested on a real industrial ROM milling circuit It is shown that the u-controller could be made to work on an industrial plant. Practical problems encountered are discussed, and reasons are given as to why the behaviour of the physical system differs form that observed in computer simulations. (Abbreviation abstract)
AC 2018
40
Corbett, Lance Brendan. "The viability of beneficiating vanadium pentoxide to ferrovanadium in South Africa". Thesis, 1992. http://hdl.handle.net/10539/23589.
Testo completoAbstract (sommario):
A research report submitted to the Faculty of Mining Engineering.
University of Witwatersrand, Johannesburg, in partial fulfillment of the
requirements for the degree of Master of Science in EngineeringHlstorically South Africa has enjoyed a privileged position with its vast natural resource base in that it has.not needed to generate wealth but has merely explored this base, The only true way to create wealth, is to add value to a commodity by means of beneficiation, South Africa is the world's largest producer of vanadium accounting for approximately 70% of the western world's requirements. Unfortunately the South African producers of vanadium mainly export vanadium in the form of slag and pentoxide, instead or ferrovanadium and other prime alloys. ( Abbreviation abstract)
AC 2018
41
Ravindran, Indira. "Beneficiation Studies On Molybdenite Ore From Harur Area, Tamil Nadu". Thesis, 1999. https://etd.iisc.ac.in/handle/2005/2387.
Testo completoAbstract (sommario):
Molybdenum is a versatile alloying and refractory metal of strategic importance. In India almost all molybdenite is obtained currently as st byproduct from copper and uranium deposits. The present Indian production is only about 66 tonnes while the demand is over 1000 tomes. It thus becomes important to explore newer deposits of molybdenum and develop efficient beneficiation strategies to recover the metal. A potential source of primary
rnolybdenite has been found in the Ham area of Dharmapuri district in Tamil Nadu.
In the present investigation, taking into consideration the importance of the problem beneficiation studies have been undertaken on core - drill molybdenite ore samples from the Hanu area. Initially, detailed characterization of the molybdenite ore has been carried out with respect to its mineralogy and chemical composition. The X-ray diffkactogam of the ore has also been recorded These studies have indicated that quartz and sericite are the major
minerals followed by carbonates and feldspar. Among the sulphide minerals, pyrite is dominant with trace amounts of galena, sphalerite, chalcopyrite and molybdenite. The molybdenum content in the ore sample has been determined to be about 0.1%. Liberation studies have revealed that molybdenum is more or less uniformly distributed in the different size fractions from 1.7 mm down below to 75 microns. However, mineralogical analysis of the different size fractions has indicated that about 85% of the molybdenite is liberated. from associated silicate and carbonates below 2 12 microns.
The results of the flotation kinetic tests have shown that percentage recovery and grade of molybdenum foLZow an inverse relationship with time. Studies carried out to evaluate different reagent - combinations, reveal that optimum values of grade and recovery could be achieved using kerosene and M1IBC. Further, these studies have shown that flotation time of 4 minutes is adequate, as beyond this time the grade of molybdenum is found to deteriorate.
Detailed mesh-of-grind studies have indicated that 20 minutes of grinding yields optimum values of molybdenum and lead in the float product and this time was fixed for all subsequent experiments.
Preliminary experiments conducted to evaluate djfferent depressants for galena have shown that satisfactory results are obtained only with sodium dichromate. Optimisation studies performed to arrive at the dosage of sodium dichromate have shown that the addition of 0.25kg/t of sodium dichromate gives optimum results with respect to overall recovery and grade of molybdenum, copper and lead in the float and tailing fractions. In a similar manner, the optimum dosage of kerosene (collector for molybdenite) has been arrived at to be 0.8kg/t taking a holistic view of the grades and recoveries of the different metal values of interest. Based on the studies carried out with respect to optimization of the mesh-of-grind, depressant and collector concentrations, it became apparent that a grade of about 0.8% Mo only could be achieved with over 80% recovery. The redeeming feature however was that over 90% of the feed could be rejected at the rougher flotation stage itself with a negligence loss of about 0.02% Mo in the tailings.
It was thus considered logical to further upgrade the Mo content by regrinding. An extensive flotation campaign was therefore mounted, adopting the following strategies:
(1) Ist stage regrinding and one cleaning
(2) IInd stage regrinding and three cleanings
(3) IIIrd stage regrinding and two cleanings
Based on the first stage regrinding tests it was found that by regrinding to 100% passing 106 microns, the Mo assay could be enhanced to over 32% from a initial value of about 0.1% in the feed. The enrichment ratio at this stage corresponds to about 340.After the second stage regrinding followed by three stages of cleaning, close to 75% recovery of Mo with an assay value of about 52% could be achieved, further enhancing the enrichment ratio to about 540. A few experiments were conducted using sodium cyanide during second stage regrinding tests and it was found that copper assay could be brought down to 0.3% from about 0.8%, without affecting the grade of lead and molybdenum. The results of the third stage regrinding tests have highlighted that a final concentrate assaying about 55% molybdenum with over 70% recovery could be obtained. It is worthy to mention that the concentrate so produced meets the specification of metallurgical grade molybdenite. The overall enrichment ratio obtained, commencing from a feed assaying 0.1% Mo, corresponds to about 580.
In order to explore the efficacy of organic depressants, which are more acceptable on environmental grounds, detailed flotation studies were carried out using dextrin with particular emphasis on galena depression. A series of experiments was carried out in an identical manner to those conducted using sodium dichromate. Here again, three stages of regrinding/cleanings test where carried out, akin to those performed using sodium dichromate. A dextrin concentration of 0.01 kg/t was found to be an optimum value from the point of grade, wt. % recovery and distribution of molybdenum, lead and copper in the cleaner concentrate.
It is noteworthy that after second stage regrinding followed by four stages of cleaning, the molybdenum assay value has significantly improved from 16% to about 53% with over 70% recovery. Another notable feature is that copper content in the concentrate is only about 0.2% even without the addition of sodium cyanide. The results of the third stage regrinding/cleaning tests have shown marginal improvement in the molybdenum assay values without affecting the grade of copper and lead. On a comparative basis, it can be inferred that dextrin holds promise to be used as a potential substitute for the inorganic depressants such as sodium dichromate and sodium cyanide. On the basis of the extensive investigations carried out on the beneficiation of molybdenite ore, a comprehensive flowsheet has been developed.
42
Ravindran, Indira. "Beneficiation Studies On Molybdenite Ore From Harur Area, Tamil Nadu". Thesis, 1999. http://etd.iisc.ernet.in/handle/2005/2387.
Testo completoAbstract (sommario):
Molybdenum is a versatile alloying and refractory metal of strategic importance. In India almost all molybdenite is obtained currently as st byproduct from copper and uranium deposits. The present Indian production is only about 66 tonnes while the demand is over 1000 tomes. It thus becomes important to explore newer deposits of molybdenum and develop efficient beneficiation strategies to recover the metal. A potential source of primary
rnolybdenite has been found in the Ham area of Dharmapuri district in Tamil Nadu.
In the present investigation, taking into consideration the importance of the problem beneficiation studies have been undertaken on core - drill molybdenite ore samples from the Hanu area. Initially, detailed characterization of the molybdenite ore has been carried out with respect to its mineralogy and chemical composition. The X-ray diffkactogam of the ore has also been recorded These studies have indicated that quartz and sericite are the major
minerals followed by carbonates and feldspar. Among the sulphide minerals, pyrite is dominant with trace amounts of galena, sphalerite, chalcopyrite and molybdenite. The molybdenum content in the ore sample has been determined to be about 0.1%. Liberation studies have revealed that molybdenum is more or less uniformly distributed in the different size fractions from 1.7 mm down below to 75 microns. However, mineralogical analysis of the different size fractions has indicated that about 85% of the molybdenite is liberated. from associated silicate and carbonates below 2 12 microns.
The results of the flotation kinetic tests have shown that percentage recovery and grade of molybdenum foLZow an inverse relationship with time. Studies carried out to evaluate different reagent - combinations, reveal that optimum values of grade and recovery could be achieved using kerosene and M1IBC. Further, these studies have shown that flotation time of 4 minutes is adequate, as beyond this time the grade of molybdenum is found to deteriorate.
Detailed mesh-of-grind studies have indicated that 20 minutes of grinding yields optimum values of molybdenum and lead in the float product and this time was fixed for all subsequent experiments.
Preliminary experiments conducted to evaluate djfferent depressants for galena have shown that satisfactory results are obtained only with sodium dichromate. Optimisation studies performed to arrive at the dosage of sodium dichromate have shown that the addition of 0.25kg/t of sodium dichromate gives optimum results with respect to overall recovery and grade of molybdenum, copper and lead in the float and tailing fractions. In a similar manner, the optimum dosage of kerosene (collector for molybdenite) has been arrived at to be 0.8kg/t taking a holistic view of the grades and recoveries of the different metal values of interest. Based on the studies carried out with respect to optimization of the mesh-of-grind, depressant and collector concentrations, it became apparent that a grade of about 0.8% Mo only could be achieved with over 80% recovery. The redeeming feature however was that over 90% of the feed could be rejected at the rougher flotation stage itself with a negligence loss of about 0.02% Mo in the tailings.
It was thus considered logical to further upgrade the Mo content by regrinding. An extensive flotation campaign was therefore mounted, adopting the following strategies:
(1) Ist stage regrinding and one cleaning
(2) IInd stage regrinding and three cleanings
(3) IIIrd stage regrinding and two cleanings
Based on the first stage regrinding tests it was found that by regrinding to 100% passing 106 microns, the Mo assay could be enhanced to over 32% from a initial value of about 0.1% in the feed. The enrichment ratio at this stage corresponds to about 340.After the second stage regrinding followed by three stages of cleaning, close to 75% recovery of Mo with an assay value of about 52% could be achieved, further enhancing the enrichment ratio to about 540. A few experiments were conducted using sodium cyanide during second stage regrinding tests and it was found that copper assay could be brought down to 0.3% from about 0.8%, without affecting the grade of lead and molybdenum. The results of the third stage regrinding tests have highlighted that a final concentrate assaying about 55% molybdenum with over 70% recovery could be obtained. It is worthy to mention that the concentrate so produced meets the specification of metallurgical grade molybdenite. The overall enrichment ratio obtained, commencing from a feed assaying 0.1% Mo, corresponds to about 580.
In order to explore the efficacy of organic depressants, which are more acceptable on environmental grounds, detailed flotation studies were carried out using dextrin with particular emphasis on galena depression. A series of experiments was carried out in an identical manner to those conducted using sodium dichromate. Here again, three stages of regrinding/cleanings test where carried out, akin to those performed using sodium dichromate. A dextrin concentration of 0.01 kg/t was found to be an optimum value from the point of grade, wt. % recovery and distribution of molybdenum, lead and copper in the cleaner concentrate.
It is noteworthy that after second stage regrinding followed by four stages of cleaning, the molybdenum assay value has significantly improved from 16% to about 53% with over 70% recovery. Another notable feature is that copper content in the concentrate is only about 0.2% even without the addition of sodium cyanide. The results of the third stage regrinding/cleaning tests have shown marginal improvement in the molybdenum assay values without affecting the grade of copper and lead. On a comparative basis, it can be inferred that dextrin holds promise to be used as a potential substitute for the inorganic depressants such as sodium dichromate and sodium cyanide. On the basis of the extensive investigations carried out on the beneficiation of molybdenite ore, a comprehensive flowsheet has been developed.
43
Kahn, Riyard. "Optimisation of reagent addition during flotation of a nickel sulphide ore at the Nkomati Mine concentrator". Thesis, 2017. http://hdl.handle.net/10539/22965.
Testo completoAbstract (sommario):
A dissertation submitted to the faculty of Engineering and the Built Environment, University of Witwatersrand in fulfilment of the requirements for the degree of Master of Science in Engineering
28 January 2017Batch scale laboratory testwork was conducted to evaluate collector and depressant addition on flotation performance of a nickel sulphide ore. The objectives of the study were to: 1. develop an understanding of the effects of collector and depressant dosage, and its interactive effects, on flotation performance and 2. determine the effect of stage dosing collector and depressant on flotation performance. Testwork was conducted on the Nkomati Main Mineralized zone orebody, a nickel sulphide orebody in the Mpumulanga Province of South Africa consisting of pentlandite, chalcopyrite, pyrrhotite, pyrite and magnesium bearing silicates. Characterisation testwork was conducted, including mineralogy on the major plant streams (by QEMSCAN) and a process survey. The results indicated that there was potential to increase the recovery of coarse pentlandite and that major nickel losses were observed in ultrafine pentlandite. Milling optimisation requires the minimisation of ultrafine generation while ensuring adequate liberation of the course nickel. Stage dosing of collector at nodal points (where more than one stream meets) is currently practiced on the plant, however, its effect had not yet been quantified on the plant or in the laboratory. Stage dosing of depressant is currently practiced on the cleaner flotation stage, however, this too has not been compared to upfront dosage on its own. Significant gangue depression was noted specifically for the cell at which stage dosing was done. The current study would provide an understanding of the current practices with the possibility of offering improvements. The addition of collector progressively improved the hydrophobicity of the sulphide minerals and gangue (with particular emphasis on magnesium bearing gangue), improving recovery significantly. As a result of additional gangue recovery at the higher collector dosages, increased depressant dosages were required to maximise nickel recovery. The collector improved valuable mineral recovery, however, gangue recovery was increased simultaneously, albeit at a reduced rate or in reduced quantities. Furthermore, increased gangue entrainment was evident at higher collector dosages from the increase in water recovery. Excessive depressant addition destabilised the froth phase by the rejection of froth stabilising gangue, which resulted in reduced recovery of the valuable minerals. Therefore, a careful balance must be maintained in order to maximise nickel recovery. Iron recovery was markedly increased at higher reagent dosages, indicative of increased pyrrhotite recovery. Pyrrhotite, although containing nickel, reduces the concentrate grade and may need to be depressed in the latter stages of flotation to ensure the final concentrate specification is achieved. This is an important observation as any improvement in nickel recovery in the roughing stages must be evaluated against the subsequent effect on the cleaning stages. Stage dosing both collector and depressant, individually and collectively, proved to be beneficial by improving the nickel recovery. Stage dosing of both collector and depressant produced higher recoveries than stage dosing of the reagents individually. The time at which the reagent is dosed also proved to have an effect on the performance with an increased dosage in the latter stages providing the highest recovery. The typical recovery by size performance for flotation is characterised by low recovery of fines and coarse with an optimum recovery of an intermediate size fraction. Stage dosing ensures that fine particles are recovered with minimal reagent addition upfront, thereby, coarser particles can be effectively recovered once the high reagent consuming fines are removed. The results have indicated that stage dosing improved the recovery of both coarse and fine particles, whilst reducing the recovery of the intermediate size fraction. Stage dosing can be implemented for two reasons: 1. maximising recovery 2. minimising reagent consumption to achieve the same recovery as upfront dosing A financial evaluation should be conducted to quantify the optimum operating solution. Minimising reagent consumption could be beneficial under conditions of very low commodity prices and excessive reagent costs.
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Buswell, Andrew Mark. "An electrochemical investigation into the floatability of pyrrhotite". Thesis, 1998. http://hdl.handle.net/10539/22047.
Testo completoAbstract (sommario):
A dissertation submitted to the Faculty of Engineering, University of the
Witwatersrand, in fulfillment of the requirements for the degree of Mastel' of
Science in Engineering
Johannesburg 1998Impala's Minerals Processing Plant in the Rustenburg Area, South Africa, uses flotation to beneficiate precious metal bearing ores from the Bushveld Complex. Pyrrhotite is one of the sulphide minerals that is targeted but it is the least amenable to current flotation conditions having the lowest recovery. Electrochemical techniques (mixed potential measurements, cyclic voltammetry and current transient techniques) were used to study the relevant reactions on the surface of pyrrhotite mineral electrodes. Aspects investigated included the oxidation of the mineral in aqueous alkaline solutions, activation by copper sulphate, kinetics of oxygen reduction and the adsorption of isobutyl xanthate. Mixed potential measurements of mineral electrodes were taken in batch flotation test work. In addition a novel qualitative measure of hydrophobicity was investigated. The oxidised surface of pyrrhotite is likely to be covered with iron hydroxides and a sulphur rich sub-lattice. No direct evidence was found for the activation of pyrrhotite by copper sulphate in alkaline solutions. It was shown however that activation could be achieved in mildly acidic media and that the surface remained activated if subsequently exposed to alkaline conditions. When achieved under acidic conditions activation was observed to enhance the degree of interaction between the mineral and the xanthate collector. Also copper sulphate appeared to aid the formation of a more hydrophobic surface (as indicated by the hydrophobicity tests). Copper activation conducted in acidic media did not significantly enhance the kinetics of oxygen reduction, a reaction seen as crucial to the adsorption of xanthate. No evidence was found for the initial chemisorption of xanthate onto the mineral surface. However evidence was found for the oxidation of xanthate to dixanthogen at sufficiently anodic potentials. It Was concluded that the relatively poor flotation performance of pyrrhotite could be combated by minimising the extent of the oxidation, adding reagents as soon as possible before the mineral becomes extensively oxidised and by removing surface hydroxides through lowering the pH during conditioning.
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45
Ramlall, Nigel Valentino. "An investigation into the effects of UG2 Ore variability on froth flotation". Thesis, 2013. http://hdl.handle.net/10413/11262.
Testo completoAbstract (sommario):
South Africa is the world’s largest producer of platinum group elements (PGEs). Mining
takes place in the Bushveld Complex, and recent statistics, (Mudd, 2010), showed that the
UG2 reef is the main source of production, accounting for approximately 60% of world
mining production. However, recovery by flotation is complicated by variations in the
mineral composition, the need to grind fine and entrainment of chromite, which has an
adverse effect on the subsequent smelting of the concentrate. The recovery of PGEs is
variable, and it is influenced by PGE feed properties such as degree of liberation, mineral
type and grain size. Conventional rougher batch flotation tests on drill core samples do not
provide sufficient information for predicting plant performance.
The aim of this research was to develop a rigorous method for the testing of UG2 drill core
samples. A rougher-cleaner flotation test procedure was developed, and statistical tests were
applied to select an appropriate model, which included entrainment of hydrophilic minerals.
Fifty UG2 samples from across the Bushveld were milled at a fixed energy input, and the
new test procedure was applied to derive model parameters for all samples. There was a
significant variability in the PGE recovery, and typical feed characteristics such as PGE feed
grade and grind did not show a clear link to the PGE recovery. This was due to the complex
mineralogy of the PGE minerals and variations in ore hardness. Hence, a statistical modelling
algorithm was used to determine the factors affecting PGE recovery, and an empirical model
was developed, which relates the PGE recovery to feed properties. The model can be used to
estimate PGE recovery based on feed properties. Samples which had a high base metal
content (e.g. high nickel to iron ratio) had a high PGE recovery, and samples which were
altered (e.g. high Rb/Sr ratio and loss on ignition) had a low PGE recovery.
Depressant addition is used in PGE flotation to control the recovery of gangue, but it also
affects the flotation of composite PGE/gangue particles. Seven of the fifty UG2 samples were
selected for a more detailed investigation, using a more advanced batch flotation test and a
mineralogical liberation analysis. The advanced batch flotation test was a new development,
in which flotation model parameters were derived simultaneously for flotation after two
stages of grinding and a combined cleaning stage. The effect of a range of depressant
additions was also modelled. The floatable PGE fraction, determined from batch modelling,
was linked to the mineralogical liberation analysis of the feed. The model is the first of its
kind, and it makes it possible to predict the mineralogical characteristics of the feed from
flotation data.
A spread-sheet simulator was developed, to demonstrate how batch data (from the advanced
flotation test) could be used to predict plant performance. Scale-up parameters were derived
by using pilot-plant data for one of the ores. The spread-sheet was then used to optimise the
plant design and depressant addition for an ore, while constraining, the mass of concentrate
and the chromite content. The example showed that there was an optimum depressant
addition and rougher-cleaner volume capacity for an ore.
The gambit of this study was the linking of feed chemical assay and mineralogical properties
to PGE recovery. The application of mineralogical tests and modelling of data from the
advanced flotation test has demonstrated that the link is relatively complex.Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2013.
46
Beyeme, Zogo Jean-Clement. "Beneficiation potential of low-grade iron ore from a discard lumpy stockpile and fines tailings dam at Beeshoek mine, Northern Cape Province, South Africa". Thesis, 2010. http://hdl.handle.net/10210/3415.
Testo completoAbstract (sommario):
M.Sc.An estimated 98% of the iron ore exploited in the world is used in the manufacture of pig iron and steel, which are non-substitutable backbones of modern society. The rapid increase of world steel production over the last few years, driven mainly by economic growth in China, have required an equal increase in iron ore production, from 876.8 Mt in 2006 to 948.1 Mt in 2007. The increased rate of exploitation of iron ores has resulted in a rapid depletion of known high-grade iron ore deposits. This, in turn, has led to a dramatic increase of prices, especially for highly thought-after high-grade lumpy iron ores from BIF-hosted deposits. In the absence of any major new discoveries of high-grade iron ore deposits, mining companies have turned to lower-grade materials to assess their beneficiation potential to expand their production base and beneficiation capacity, in order to satisfy future demand. Within this existing framework, this research project was initiated to assess the beneficiation potential of low-grade lumpy stockpiles and high-grade iron ore fines at Beeshoek Iron Ore Mine, owned by Assmang Ltd. The mine is located 7 km West of Postmasburg, in the Northern Cape Province of South-Africa, and processes currently 5.60 million tons of uncontaminated run-of-mine ore per annum. Crushing, washing, classification and jigging are used to produce 2.12 million tons of (37.8% of ROM) of lumpy iron ore product. The balance (3.48 million tons) is currently not used, but is stockpiled or discarded. This includes 0.90 million tons (16.2% of ROM) of ore-grade fines, 0.86 million tons (15% of ROM) of tailings sludge and 1.74 million tons (31% of ROM) of lumpy low grade material. Both ore-grade fines and low-grade lumpy material are discarded separately; they are currently considered as waste. The low-grade lumpy is stockpiled while the fines are used to fill-in mined-out open pits. The evaluation of the beneficiation potential of these two material streams is the main goal of this study. Representative samples were collected from ore-grade fines and the current stockpile for low-grade lumpy material. Hand sorting and lithological categorization of the lumpy material facilitated petrographic and mineralogical studies using light and scanning electron microscopy, as well as X-ray powder diffraction studies. Major and trace element geochemistry were determined using X-ray fluorescence spectrometry and titrimetry (to accurately determine the concentration of iron). Whole rock densities were determined for all lithotypes recognized in the low-grade lumpy material. The grain size distribution was determined for the lumpy materials by actual measurement of the diameter of a representative number of particles, and for fines by sieve analysis. Fines beneficiation tests were conducted using spiral separation and simple classification tests. Washing was used as additional beneficiation method on the fines.
47
Viljoen, Willemien. "Phase relations in the system Cu-Fe-Ni-S and their application to the slow cooling of PGE matte". Thesis, 2002. http://hdl.handle.net/2263/28674.
Testo completo
48
Moodley, Taswald Llewelyn. "The development of an experimental technique for UG-2 ore flotation". Thesis, 2013. http://hdl.handle.net/10413/11216.
Testo completoAbstract (sommario):
Production of platinum and associated metals is a major source of revenue for South Africa. Significant losses occur in the concentrating stage (10 to 15 per cent) and this research is focused on optimising platinum flotation. Research begins by conducting laboratory batch flotation tests. However, subsequent pilot-plant tests often produce different results. It is believed these differences arise from the artificial nature of laboratory techniques. This project was focused on improving flotation techniques in the laboratory.
The largest source of platinum in South Africa is the UG2 reef and two samples of this ore were used for testing: ‘good’ and ‘bad’ ore. These had different characteristics with regards to the recovery of PGMs and the presence of talc. The latter is an unwanted floatable mineral, which must be depressed to prevent excessive recovery.
The conventional laboratory test procedure makes use of batch tests in various sizes of flotation cells. The procedure was made more realistic, by using four stages of flotation, rather than just two, to mimic a typical platinum flotation plant. The use of four stages made it possible to separate the fast-floating and slow-floating stages and to control froth conditions accordingly. Attention was also given to the fact that in laboratory tests, water is often added to the ‘cleaner’ stage of flotation, to make up the level. Experiments showed that this dilution, which does not take place in practice, had a significant impact on overall efficiency.
A method of measuring frother concentration was developed and used to determine the realistic level of frother in cleaning tests. Tests at these levels of frother concentration showed that significant improvements could be made to plant performance, by making use of a thickener to reduce the frother concentration in the cleaning stages.
The improved test procedure was used on both good and bad ores, and the effect of regrinding was also tested. A combined solids recovery of 2 % over both cleaners was targeted for all test work. At this recovery, the regrinding of the bad ore increased the PGM recovery from 67 to 76 per cent at the cost of an additional 8 g/t depressant.
An investigation of the effect of frother concentration in the cleaning stage, using good ore, demonstrated that that rejection of chromite could be improved significantly by reducing frother concentration. The tests mimicked the use of a thickener to separate some of the water with a high concentration of frother. Tests conducted on the good ore showed that use of two thickeners, as opposed to none, reduced the Cr2O3 content of the final concentrate from 4.2 to 3.2 per cent for the equivalent concentrate mass and PGM recovery. The depressant requirement was also reduced from 67 to 55 g/t. These tests provided insight on how to improve performance on a platinum flotation plant, particularly when floating the bad ore.
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Penberthy, Catharina Johanna. "The effect of mineralogical variation in the UG2 chromitite on recovery of platinum-group elements". Thesis, 2002. http://hdl.handle.net/2263/29887.
Testo completoAbstract (sommario):
Platinum-group elements (pGEs) are recovered from UG2 chromitite by milling and flotation. The mechanisms involved during beneficiation of this type of ore are still poorly understood, partly because of its complex nature. Image-analysis techniques were used to characterise the mineralogy ofUG2 chromitite from diverse geological environments, as well as the milling and flotation products derived from each of these ores. Postmagmatic alteration ofUG2 chromitite has a profound effect on the mineralogy, chemistry and recovery characteristics of the UG2 chromitite. Relatively unaltered UG2 chromitite consists predominantly of chromite and primary silicates, mostly bronzite and plagioclase with minor phlogopite, and small amounts of secondary silicates such as talc and chlorite. Trace quantities of base-metal sulphides, predominantly pentlandite, pyrrhotite and chalcopyrite ± pyrite, generally occur at chromite-silicate grain boundaries. PGEs are present both as discrete PGE minerals, and, to a lesser extent, sub-microscopically in other phases, mostly palladium and rhodium in pentlandite. The PGE mineral assemblage is characterised by sulphide minerals, mostly braggite, cooperite, nickeloan malanite and laurite, and is closely associated with the base¬metal sulphides. Recovery of PGE minerals is strongly dependent on the degree of liberation, with liberated PGE minerals and PGE minerals associated with liberated base-metal sulphides, the fastest-floating particles. PGE minerals report to flotation tailings predominantly as fine-grained inclusions in coarse silicate particles. In places, the footwall rocks have been replaced by iron-rich ultrabasic pegmatoid. As a result of interaction with Fe- and Ti-rich fluids, the chromite grains in the UG2 chromitite have been enlarged due to sintering, and the PGE mineral assemblage replaced by one consisting predominantly of laurite, Pt-Fe alloy and other non¬sulphide PGE minerals. The non-sulphide PGE mineral grains appear to be slower ¬floating than sulphide PGE minerals. Low temperature hydrothermal alteration appears to have caused relatively widespread alteration of the UG2 chromitite in some areas, resulting in corrosion and redistribution of sulphide minerals, as well as the replacement of primary magmatic silicates by secondary silicates such as pumpellyite, epidote, prehnite, albite, talc, chlorite and quartz. Ore from such areas are characterised by a base-metal sulphide assemblage consisting predominantly of millerite, chalcopyrite, and pyrite. Base¬metal sulphide and PGE minerals occur in fine-grained intergrowths with silicates, resulting in poor liberation. In the samples investigated, composite particles were often faster-floating than expected, at least partly due to the presence of naturally floatable talc. The effect of faulting on the mineralogy of the UG2 chromitite probably depends on distance from the fault zone, and possibly also timing of faulting, and can cause cataclasis of the ore. Where cataclasis occurred, broken mineral grains are cemented by secondary, hydrous silicates. Liberation of base-metal sulphides and PGE minerals are poor, and recoveries consequently very low. It was demonstrated that reasonable estimates of total PGE+Au recovery can be made from the mineralogical characteristics ofUG2 chromitite ore. Based on the mineralogy of ore from a specific area, provision can be made for appropriate adjustments to metallurgical flowsheets.Thesis (PhD)--University of Pretoria, 2006.
Geology
Unrestricted
50
Hlabangana, Nkosikhona. "Investigation of the joint comminution and leaching process for a gold ore: an attainable region approach". Thesis, 2016. http://hdl.handle.net/10539/22446.
Testo completoAbstract (sommario):
A thesis submitted to the Faculty of Engineering and The Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering
Johannesburg
12 September 2016Comminution and leaching unit processes play a major role in extracting valuable minerals from ore. Most of the research reported in the literature has focused on optimising individual unit operations rather than on integrating the whole process. This thesis develops an integrated approach to mineral processing systems and flow sheets and is intended to create a methodology for process synthesis that can be applied throughout the extractive metallurgical industry. This could lead to improved efficiency in the overall process by obtaining optimum recovery and, most important, a reduction in energy and material costs. In order to illustrate the methodology a particular example was chosen, namely optimizing the joint comminution and leaching of a particular gold ore. In this investigation laboratory scale grinding and leaching profiles for a gold feed sample (1700–850 μm) were measured. In a laboratory mill various combinations of grinding media, filling level and ball size were investigated, and of the three ball sizes used (10, 20 and 30mm) breakage was most pronounced for the 20 mm. Thus for instance it was also established that when using a higher filling ( =30%) and a ball size of 30 mm, more energy was consumed but less liberation occurred, thus a lower amount of gold was extracted during a 24-hour leaching period. Finally, the breakage kinetics of the gold ore was looked at. Using a standard population model the breakage and selection function parameters were successfully calculated. An investigation into the dissolution kinetics of gold ore in a solution of NaCN was also done. These were found to depend on the stirring rate, reaction temperature, particle diameter and the concentration of the leachant. The rate increased with the stirring speed, reaction temperature and leachant concentration, but decreased when the particle size was greater. The activation energy for the dissolution was estimated at about 3 kcal/mol. Furthermore, the linear relationship between the rate constant and the reciprocal of the square of the particle size is a strong indication that the gold dissolution process is diffusion-controlled. The experimental results were well-fitted to a shrinking core model. In attempting to understand the results, the researcher carried out a number of experiments that involved an investigation into the relationship between comminution and leaching in terms of energy usage and particle size, the former to establish the most efficient application of energy, and the latter to identify the degree of fineness that would ensure optimal recovery. The Attainable Region (AR) method was then used to establish ways of finding the leaching and milling times required to achieve minimum cost (maximise profit). No work on utilizing the AR technique to minimise the cost of milling and leaching on a real industrial ore has previously been published. The investigation aims to show how the AR technique can be used to develop ways of optimising an industrial process that includes milling and leaching. The experimental results were used to show how this method could be successfully applied to identifying opportunities for higher efficiency when performing these operations. The approach however is general and could in principle be used for any two or more unit operations in determining how the product from one unit should be prepared to feed to the next unit so as to optimize the overall process.
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