Dissertations / Theses on the topic 'Mineral Processing'
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1
Al-Bassam, Ahmed Z. Mohamed Hussein. "Mineral processing using deep eutectic solvents." Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/42876.
Abstract:
Processing sulfur containing minerals is one of the biggest sources of acute anthropogenic pollution particularly in the form of acid mine drainage. Sulfur-based minerals are generally roasted to convert them to the oxide, producing SO2 or leached in acid producing H2S. This study attempts to show an innovative method for processing sulfide-based minerals using a deep eutectic solvent (DES), Ethaline, which is a mixture of choline chloride and ethylene glycol. It is shown that pyrite can be solubilised by both electrochemical oxidation and reduction in a DES. A novel method is demonstrated to investigate the redox properties of minerals using a paste made from the mineral powder in a DES. The first bulk electrochemical dissolution of pyrite is shown without the formation of H2S or SO2. The solubilised species are investigated using cyclic voltammetry UV-vis spectroscopy and EXAFS. In all cases for the iron minerals studied, it was found that the electrochemistry of the counter ion and not the metal, controlled the ease of dissolution. It is also shown that the soluble species, including elements such as arsenic, can be recovered electrochemically which could potentially decrease acid mine drainage. The electrochemical properties of other iron–sulfur and iron–arsenic minerals are also presented and compared to those of pyrite. The final part of this study uses different cell designs in an endeavour to optimise the space-time-yield of the electrochemically assisted digestion of jarosite. It was found that the electrochemical digestion of material was up to 20 faster than the chemical dissolution. It was, however found that formation of insoluble precipitates, particularly of lead and zinc sulfates affected the performance of the separator membranes and this could decrease the yield of digested metal. The presence of high concentrations of iron salts led to passivating films on the zinc surface during cementation.
2
Basnayaka, Lahiru Rasanga. "Influence of Clay on Mineral Processing Techniques." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/74929.
Abstract:
This PhD thesis investigated the influence of kaolin and bentonite clays in the ore on flotation, filtration and centrifugal concentration. The results showed that the presence of particularly bentonite in the ore had a detrimental effect on flotation and filtration. The information generated from this work will advance our knowledge as well as provide important information for plant metallurgists. The project, therefore, is essential for the mineral industry that process clay-containing ores.
3
Agbolosoo, Emmanuel Kwami. "Mineral processing in a less developed country: Bauxite processing in Ghana." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185546.
Abstract:
The purpose of this dissertation is to evaluate the feasiblity of alumina production in Ghana to replace imported alumina for the production of aluminum. It spells out the conditions which led to the existing bauxite-alumina-aluminum trade in the country. The structure of the economy of Ghana is examined to show the contributions of the important sectors to the total income of the country, and its dependence on a few export commodities for revenue. The plan to build a dam for the generation of hydroelectric power was linked to the establishment of an integrated aluminum industry based on the exploitation of domestic bauxite reserves. As the country could not finance the project alone, foreign assistance was sought. VALCO, a subsidiary of Kaiser and Reynolds, was formed to undertake the project. The agreement reached with VALCO was that a smelter would be built to use imported alumina for ten years, during which time a refinery would be built to feed the smelter from domestic sources. However, after ten years this could not be achieved, and the smelter continues to use imported alumina. A model of the world aluminum economy is used for analyzing the sensitivity of price to production and consumption expansion. The results show that industry demand is sensitive to the level of industrial activities in the developed countries, and less sensitive to the own price and cross price variables of aluminum in both the short and long run. On the other hand, supply is inelastic to the own price and the rate of capacity utilization in the short run, but elastic to both variables in the long run. An appraisal of opening a bauxite mine and an alumina refinery at Kibi is undertaken. The results show the levels of bauxite and alumina prices and the costs of construction at which the project is feasible. The shadow values and weights used are permittd to vary with changes in the economy's foreign trade and the balance of payments.
4
Gwamba, John. "Pearl millet : influence of mineral biofortification and simple processing technologies on minerals and antinutrients." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/60808.
Abstract:
Pearl millet is an important staple food in rural Africa. However, the mineral bioavailability of pearl millet is low due to its high content of antinutrients, particularly phytate. This research investigated the effects of mineral biofortification, steeping/lactic acid fermentation and parboiling alone and in combination with abrasive decortication of pearl millet grain on its mineral and antinutrient contents. Six normal varieties and two mineral biofortified hybrids were investigated.
There was considerable variability in mineral content among the varieties. Iron content ranged from 3.0 to 9.6 mg /100 g and zinc from 3.0 to 4.8 mg /100 g. The mineral biofortified hybrids Dhanashakti and ICMH 1201 had substantially higher iron (21-68%) and zinc (15-39%) contents compared to the normal varieties. Phytate content differed substantially, with levels from 830 to 1360 mg /100 g. There was no definite trend between the phytate content of normal and mineral biofortified types.
Decortication did not cause significant losses in zinc, but resulted considerable iron losses (mean 31%) across the varieties. There were minimal effects of steeping/lactic acid fermentation and parboiling on iron and zinc contents. Mineral biofortified hybrids were associated with high iron and zinc content after all processing treatments. Decortication of raw grain substantially reduced phytate (mean 24%) and by a further 12 percentage points when applied after steeping/lactic acid fermentation. Parboiling plus decortication was less effective in reducing phytate content. The critical phytate: iron molar ratio of <1, above which iron absorption is seriously impaired, was not achieved with any of the processes. However, steeping/lactic acid fermentation plus decortication and parboiling plus decortication reduced the phytate: zinc molar ratio to below the critical level of <15 in some varieties. Generally, the mineral biofortified hybrids had improved phytate: mineral molar ratios than the normal varieties for both raw and processed grains. Decortication greatly reduced total phenolic content (mean 24%) across the varieties and by an additional 14 percentage points after steeping/lactic fermentation and parboiling.
Abrasive decortication in combination with steeping/lactic acid fermentation is an effective way of reducing phytate content in pearl millet grain, and hence somewhat improving estimated iron and zinc availability. It is recommended that the process is utilised to a greater extent in pearl millet food processing. Parboiling is also effective in phytate reduction, and can be adopted. Because mineral biofortified pearl millet hybrids have much higher iron and zinc contents, their breeding and cultivation should be promoted in rural Africa.Dissertation (MSc)--University of Pretoria, 2016.
Food Science
MSc
Unrestricted
5
Goh, Siew Wei Chemistry Faculty of Science UNSW. "Application of surface science to sulfide mineral processing." Awarded by:University of New South Wales. School of Chemistry, 2006. http://handle.unsw.edu.au/1959.4/32912.
Abstract:
Surface spectroscopic techniques have been applied to facets of the flotation beneficiation and hydrometallurgical extraction of sulfide minerals to enhance the fundamental understanding of these industrially important processes. As a precursor to the determination of surface chemical composition, the sub-surface properties of some sulfide minerals that have not previously been fully characterised were also investigated. The electronic properties of ??-NiS and ??-NiS (millerite), Ni3S2 (heazlewoodite), (Ni,Fe)9S8 (pentlandite), CuFe2S3 (cubanite), CuFeS2 (chalcopyrite), Cu5FeS4 (bornite) and CuS (covellite) were investigated by conventional and synchrotron X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy augmented by ab initio density of state calculations and NEXAFS spectral simulations. Particular aspects studied included the relationship between sulfur coordination number and core electron binding energies, the higher than expected core electron binding energies for the sulfur in the metal-excess nickel sulfides, and the formal oxidation states of the Cu and Fe in Cu-Fe sulfides. It was concluded that the binding energy dependence on coordination number was less than previously believed, that Ni-Ni bonding was the most likely explanation for the unusual properties of the Ni sulfides, and that there was no convincing evidence for Cu(II) in sulfides as had been claimed. Most of the NEXAFS spectra simulated by the FEFF8 and WIEN2k ab initio codes agreed well with experimental spectra, and the calculated densities of states were useful in rationalising the observed properties. XPS, static secondary ion mass spectrometry (SIMS) and NEXAFS spectroscopy were used to investigate thiol flotation collector adsorption on several sulfides in order to determine the way in which the collector chemisorbs to the mineral surface, to differentiate monolayer from multilayer coverage, and to characterise the multilayer species. It was found that static SIMS alone was able to differentiate monolayer from multilayer coverage, and together with angle-resolved NEXAFS spectroscopy, was also able to confirm that 2-mercaptobenzothiazole interacted through both its N and exocyclic S atoms. The altered layers formed on chalcopyrite and heazlewoodite during acid leaching were examined primarily by means of threshold S KLL Auger electron spectroscopy, but no evidence for buried interfacial species was obtained.
6
Vorster, Werner. "The effect of microwave radiation on mineral processing." Thesis, University of Birmingham, 2001. http://etheses.bham.ac.uk//id/eprint/309/.
Abstract:
Between 50% and 70% of the total energy used in the extraction process may be attributed to comminution. Microwave pre-treatment has been suggested as a means to decrease the energy requirements. A variety of mineral ores have been investigated and the effects of microwave radiation quantified in terms of the mineralogy, changes in the Bond Work Index, flotability and magnetic separation. It has been shown that microwave pre-treatment is most effective for coarse grained ores with consistent mineralogy consisting of good microwave absorbers in a transparent gangue (up to a 90% decrease in Bond work index for Palabora copper ore) whereas fine grained ores consisting predominantly of good absorbers are not affected as well (a reduction of only 25% in work index for Mambula ore). Although the mineralogy of minerals are affected by exposure to microwave radiation, flotability and magnetic separation characteristics have been shown not to be adversely affected, unless the microstructure is completely destroyed after prolonged microwave exposure. Computer simulations have shown that significant changes to comminution circuits are possible as a result of microwave induced work index reductions (three mills reduced to one). Purpose-built microwave units may hold the solution for more efficient mineral extraction in the near future.
7
Wanigasekara-Mohotti, Don Kripalath. "Optimisation for the synthesis of mineral processing flowsheets." Thesis, The University of Sydney, 1999. https://hdl.handle.net/2123/27597.
Abstract:
‘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.
8
Treloar-Bradford, Stephen Hall. "The application of artificial intelligence to mineral processing control." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239885.
9
Okibe, Naoko. "Moderately thermophilic acidophiles and their use in mineral processing." Thesis, Bangor University, 2002. https://research.bangor.ac.uk/portal/en/theses/moderately-thermophilic-acidophiles-and-their-use-in-mineral-processing(9c8b82ee-27ad-453e-baf6-9afb284c7735).html.
Abstract:
This research project focused on moderately thermophilic acidophilic microorganisms and their role in the oxidation of pyrite. A major objective of the work was to assess the relative efficiencies of defined combinations of moderate thermophiles in oxidising pyrite under defined conditions. In addition, various aspects of the physiology and phylogeny of moderately thermophilic acidophiles were investigated. Moderately thermophilic acidophiles, including novel acidophiles (a thermotolerant Leptospirillum and a Ferroplasma sp. ), were isolated from a commercial stirred-tank pilot plant. Pyrite oxidation by mixed cultures of different combinations of moderate thermophiles, including the novel isolates, was assessed in preliminary shake flask experiments. Data from these experiments were used to select microbial consortia in later experiments in temperature- and pH-controlled bioreactors. These involved monitoring rates of mineral oxidation, and relative numbers of the different microorganisms included in the original inoculum, using a plating technique in conjunction with a molecular approach (FISH). The results from the pyrite oxidation studies indicated that mixed populations of acidophiles may accentuate or diminish the rates and extent of pyrite oxidation, relative to pure cultures. The thermotolerant Leptospirillum isolate was found to be unable to oxidise a pyrite concentrate when grown in pure culture, though this inhibition was overcome when the iron-oxidiser was grown in mixed cultures with various Grampositive acidophiles. Investigation of the effects of fifteen individual and mixtures of flotation chemicals on moderately thermophilic acidophiles revealed different degrees of toxicities of the different reagents and sensitivities of the microorganisms, with the Leptospirillum isolate generally being the most sensitive of those tested. The phenomenon of pH-related ferric iron toxicity to moderately thermophilic and mesophilic Gram-positive bacteria was also investigated. ARDREA (Amplified Ribosomal DNA Restriction Enzyme Analysis) using the 16S rRNA gene sequences of known acidophilic bacteria, was refined and developed, and applied successfully to identify moderate thermophiles isolated from environmental samples.
10
Jirestig, Jan A. "High intensity and high gradient magnetic separation in mineral processing." Doctoral thesis, Luleå tekniska universitet, 1994. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25815.
Abstract:
Natural minerals often lack well defined magnetic susceptibilities. Instead they must be thought of as occurring in a susceptibility range where the bulk susceptibility is affected by present impurities. Inclusions or foreign atoms in solid solution may alter a materials magnetic properties to a large extent. Mixed particles of dia andlor paramagnetic materials display a linear relationship while ferromagnetic inclusions involve a demagnetisation factor. The susceptibility distribution of value minerals in relation to gangue in the ore is the most important factor governing magnetic separation performance. Until recently, high gradient and high intensity separators of matrix type were exclusively used in wet processing. Now, new dry separators are extending the particle range for dry, fine particle separation. The capture characteristics of the matrix has been shown to change with the magnetic field strength. The separation cut is more precise at high fields, at low fields the capture probability graph cants. By superimposing the capture function on the susceptibility distribution of an ore, it is shown that materials containing value minerals at either high or low susceptibility is ideal for HGMS separation. Complex ores carrying value and gangue minerals distributed over a wide susceptibility range are unfavourable. The former situation is common in industrial mineral processing and in the upgrading of flotation concentrates. The latter susceptibility distribution is very common in complex sulphide ore feeds.Godkänd; 1994; 20070429 (ysko)
11
Aydin, Gulsen. "Use Of Waste Pyrite From Mineral Processing Plants In Soil Remediation." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613900/index.pdf.
Abstract:
Pyrite (FeS2) is commonly present in complex sulphide ores in significant amounts. After the enrichment of such ores by flotation, pyrite is either produced as a separate concentrate and sold to acid manufactures or removed and disposed off as tailing. Due to lack of demand from manufacturers, most of pyrites is usually disposed off as tailing. Therefore, pyrite is usually a waste from complex sulphide ores. Yet, it may be a remediation additive for calcareous soils and calcareous- alkali soils deficient in Fe and other micronutrients such as Cu, Zn and Mn. Waste pyrite may be also an alternative amendment to gypsum because of the production of sulphuric acid which is effectively used in the reclamation of calcareous alkali soils.
The effectiveness of adding waste pyrite and sulphuric acid produced from waste pyrite to calcareous-alkali soil (Sarayköy-Ankara) and calcareous soil (Gaziantep) was studied under laboratory conditions. Pure gypsum was also used as an amendment for the comparison of the effectiveness of waste pyrite in the reclamation of alkali soils. Gypsum, powder waste pyrite and sulphuric acid were applied to the soil with reference to the gypsum requirement (GR) of the soils. Greenhouse pot tests were carried out with wheat as test plant to determine the effect of waste pyrite treatment on the plant yield (wheat) and on the amount of micronutrient (Fe, Cu, Zn, Mn) essential for plant growth. Hazard potential of pyritic tailings in terms of heavy metal contamination was also taken into account. The results showed that the soil pH and exchangeable sodium percentage (ESP), indicators of alkalization, decreased upon pyrite addition to calcareous- alkali soils of Saraykö
y-Ankara. It was also found that pyritic tailings were effective in the increasing level of essential micronutrients (Fe, Cu, Zn and Mn) for plant growth in both soils. This was ascertained by the dry matter yield of the plants in the green house pot tests. Heavy metal toxicity caused by pyrite which is a rightful concern remained well below the legal limits in the soils. Thus, it was concluded that the application of pyritic tailings promoted rapid amelioration of calcareous-alkali soil (Saraykö
y-Ankara) and calcareous soil (Gaziantep) with no deleterious heavy metal contamination.
12
Ketata, Chefi. "Knowledge-assisted stochastic evaluation of sampling errors in mineral processing streams." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq39321.pdf.
13
Koermer, Scott Carl. "The Application of Mineral Processing Techniques to the Scrap Recycling Industry." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/63994.
Abstract:
The scrap metal recycling industry is a growing industry that plays an important role in the sustainability of a large global metal supply. Unfortunately, recycling lacks many standards, and test procedures in place for mineral processing. These standards and practices, if used in recycling, could aid recyclers in determining and achieving optimal separations for their plant.. New regulations for scrap imports into China make it difficult to obtain the metal recoveries that have been achieved in the past. In order to help scrap yards adhere to the new regulations the Eriez RCS eddy current separator system was tested in full scale. The principles this system uses, called circuit analysis, have been used by the mining industry for years, and can be used with any separation system. The Eriez RCS system surpassed the requirements of the Chinese regulations, while simultaneously increasing the recovery of metals. In order to further analyze eddy current separator circuits, tree analysis was attempted for single eddy current separators, as well as more complex circuits mimicked using locked cycle tests. The circuits used in the locked cycle test were a rougher-cleaner, a rougher-scavenger, and a rougher-cleaner-scavenger. It was found that it is possible to use tree analysis to compare different eddy current separator circuits using the same settings, however standards for this practice need to be established for it to be useful. Using the data analysis methods developed for this particular tree analysis, the rougher-cleaner-scavenger test had the best performance overall. This is the same result as the full scale testing done on the Eriez RCS system, but more testing should be conducted to confirm the data analysis techniques of calculating theoretical efficiency, recovery efficiency, and rejection efficiency.Master of Science
14
Johnston, Glen Harvey George. "Evaluation of radiation and dust hazards associated with mineral sand processing." Thesis, Queensland University of Technology, 1988. https://eprints.qut.edu.au/35942/1/35942_Johnston_1988.pdf.
Abstract:
Possible health hazards have been investigated in a mineral sand processing plant to determine the risks to workers contributed by four principal sources:
(i) External gamma radiation ii) Inhaled radioactivity in airborne dust particles (iii) Inhaled activity from airborne radon and radon daughter isotopes
(iv) Respirable free silica Gamma radiation surveys of the plant working environs using
a portable survey meter indicated possible exposure rates
ranging from 70 nSv h-1 to a maximum of 50 μsv h- 1 (near a large pile of monazite sand). The average exposure rate was 400 nSv h-1 • Assuming 100% worker occupancy time under this average rate, then a possible gamma radiation dose of 1 mSv could be received in one working year (2000 hours exposure). Airborne dust sampling in the dry mill of the process plant comprising samples obtained from a portable personal air sampler, stationary high volume samples and cascade impactor samples indicated an average gross alpha-activity or concentration range of 0.02 to 0.16 Bq m-3 (average = .07 Bq m-3 ), with an average activity median aerodynamic diameter (AMAD) of 3.2μm and an activity ratio of 2.4(± 0.4) activity air concentration value average thorium/uranium
1. The average alpha is about 12% of the
recommended derived air concentration limit.
Airborne radon-222 gas released from mineral sand products as detected using solid state nuclear track detectors (CR- 9 plastic). Gas concentrations in the dry mill were found to range from 30 to 220 Bq m~ (average= 35 ± 15 Bq m-3 ). Compared to an equilibrium equivalent recommended limit of
1500 Bq m-3 (International Commission on Radiological
Protection), the average radon-222 concentration is some 2% of the limit. X-ray diffraction measurements on eleven (11) samples of respirable dust revealed four (4) samples having quartz concentrations exceeding the recommended limits. The average percent quartz content in the plant was determined to (by mass) of airborne dust
be (22 + 7)%, with an average quartz mass concentration of 0.8 ± 0.5 mg m-3 •
This may be compared with a mass concentration limit of
0.93 mg m-3 > which places the average quartz concentration
at 86 % of the limit.
Respirable dust in the plant is the chief source of hazard from both a radiological and non-radiological standpoint. General recommendations for reduction of risk include: (i) Reduction of dust from the working environment (possibly enclosing and ventilating dust
producing machinery); (ii) Wearing of efficient respiratory protection apparatus by workers;
(iii)Reduction of worker occupancy time in dust
affected areas.
15
Pinto, Thiago César de Souza. "Aplicação de técnicas clássicas para polpas não floculadas de dimensionamento de espessadores aplicadas a suspensões de salmoura e lodo biológico." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3134/tde-01042009-101018/.
Abstract:
O espessamento é uma operação unitária que tem como finalidade separar, por diferença de massa específica entre o sólido e o líquido, sólidos suspensos em meio fluido, pela ação da gravidade. É bastante empregado industrialmente em processos contínuos no adensamento de polpas e minérios, em unidades com reação de precipitação e no tratamento de efluentes, dentre outros. Os equipamentos que realizam esta operação, chamados espessadores, são, em geral, tanques abertos de formato cilíndrico, instalados no eixo vertical com a entrada da suspensão na parte superior central, de fundo ligeiramente cônico para a retirada da polpa espessada e calha circulando o topo para descarga do líquido clarificado. As várias técnicas de projeto destas unidades contínuas são comumente baseadas em ensaios de bancada com provetas. Não é raro ocorrerem para os mesmos dados experimentais, áreas de projeto com desvios superiores a 50%. O presente trabalho visou verificar a validade das técnicas de seleção de TALMADGE-FITCH, ROBERTS e FLUXO DE SÓLIDOS, para o dimensionamento de espessadores industriais com salmoura e lodo biológico. Foram realizados para este fim, ensaios de espessamento em provetas com as próprias suspensões industriais, calculadas as áreas pelas técnicas supracitadas e comparadas com os resultados das secções dos equipamentos contínuos industriais. Os desvios médios dos diâmetros para cada técnica em relação ao espessadores industriais apresentaram contra a segurança dos equipamentos um valor de 42% para o método de Talmadge-Fitch, 45,5% para Roberts e 43,5% para o método do Fluxo de sólidos. Concluiu-se, para as condições estudadas, que os métodos de provetas utilizados forneceram valores na mesma ordem de grandeza e que requerem um fator de escala para o dimensionamento das unidades industriais contínuas.Thickening is a unit operation that has the goal of solid-liquid separation. The principle of this separation is the difference of specific weight between solid and liquid. This unit operation is used in mineral industries, to ore concentrate, wastewater, and others. The tanks called thickeners are usually open, with the feed on the top of the equipment. The solids discharge is done trough the bottom in a conical shape. The most techniques of sizing thickeners are based on graduated cylinders, and it is a common get result that has a difference area in about 50%. This happens because security coefficient, difficulties for results interpretation and scales factors. This research has the goal to apply the techniques of selection of Solids Flux, Roberts and Talmadge-Fitch in graduated cylinders. These methods are classical for thickener sizing. A comparison has been made between the results by those methods with the data obtained from continuous industrial units for salt solution and biological brine. The shunting line for the techniques obtained was 42% for Talmadge-Fitch, 45,5% for Roberts and 43,5% for Solid Flux in the relationship with industrial thickeners. In conclusion, for the studied condition, all methods showed values in the same order and requires a scale factors to sizing the continuous thickeners.
16
Van, Tonder Erika. "The effect of ore blends on the mineral processing of platinum ores." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10982.
Abstract:
Includes abstract.Includes bibliographical references (leaves 96-101).
This thesis investigates the effect of ore blends on milling and flotation performance. Anglo Platinum's Waterval UG2 concentrator in Rustenburg processes ore from various shafts.
17
Jeffries, Cameron. "Radiological exposure due to radioactivity carrying aerosols in a mineral sand processing plant." Thesis, Queensland University of Technology, 2002. https://eprints.qut.edu.au/37123/7/37123_Digitised%20Thesis.pdf.
Abstract:
Mineral sand processing involves a radiological risk due to uranium and thorium series isotopes. Characterising the radioactive aerosol requires measurement of the activity size distribution and the isotopic composition of the aerosol. This is a time consuming process requiring long sampling times and sample counting after a suitable delay time. As a result a number of weeks are required to complete analysis of the activity size distribution. Instrumentation is now available that determines the number and mass distribution within a matter of minutes.
Measurements of activity, number and mass distribution and total activity concentration were made at six sites in the Consolidated Rutile Limited dry processing mill at Pinkenba, Queensland. The activity distribution was measured using a cascade impactor. The number distribution was measured using an Aerodynamic Particle Sizer. The mass distribution was measured with the impactor of two samples and was calculated from the measured number size distributions. The activity distribution was counted twice with a six month gap to test the effect of in growth of 210Po from attached 210Pb. It was concluded that 210Po in growth has a negligible effect on the measured activity size distributions.
The activity and mass distributions measured by the impactor were compared. The impactor measured mass distribution was compared to the APS calculated mass distribution. The activity distribution was compared with the number and mass distributions determined by the APS. Agreement was found between the activity and APS mass distribution. The results show that the activity distribution could be determined quickly by measuring the mass distribution with the APS and applying the total activity concentration.
18
Cleaver, Adam Alexander. "Mixed cultures in mineral processing bioreactors : development of phylogenetic probes for culture analysis." Thesis, University of Warwick, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246794.
19
Simpson, D. E. "Mathematical modelling and analysis of the uncertainty of networks of mineral processing operations." Thesis, University of Greenwich, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233851.
20
Wilson, John M. D. (John Murray Duff) Carleton University Dissertation Earth Sciences. "Mineralogical characteristics which affect mineral processing of Faro and Vangorda Ores, Yukon, Canada." Ottawa, 1995.
21
Robinson, Katie Jane. "Electrochemical studies of rare earth and transition metals in molten NaCl-KCl." Thesis, Imperial College London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296988.
22
Kerbey, Mark Henry. "Tag deposition kinetics and selectivity in the magnetic tagging of mineral suspensions." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312285.
23
Karlkvist, Tommy. "Selectivity in Calcium mineral flotation - An analysis of novel an existing approaches." Doctoral thesis, Luleå tekniska universitet, Mineralteknik och metallurgi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-63132.
24
Hallén, Mattias. "Comminution control using reinforcement learning : Comparing control strategies for size reduction in mineral processing." Thesis, Umeå universitet, Institutionen för fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-153273.
Abstract:
In mineral processing the grinding comminution process is an integral part since it is often the bottleneck of the concentrating process, thus small improvements may lead to large savings. By implementing a Reinforcement Learning controller this thesis aims to investigate if it is possible to control the grinding process more efficiently compared to traditional control strategies. Based on a calibrated plant simulation we compare existing control strategies with Proximal Policy Optimization and show possible increase in profitability under certain conditions.
25
Kam, Kiew M. "Simulation and implementation of nonlinear control systems for mineral processes." Thesis, Curtin University, 2000. http://hdl.handle.net/20.500.11937/2383.
Abstract:
Differential geometric nonlinear control of a multiple stage evaporator system of the liquor burning facility associated with the Bayer process for alumina production at Alcoa Wagerup alumina refinery, Western Australia was investigated.Mathematical models for differential geometric analysis and nonlinear controller synthesis for the evaporator system were developed. Two models, that were structurally different from each other, were used in the thesis for simulation studies. Geometric nonlinear control structure, consisting of nonlinear state feedback control laws and multi-loop single-input single-output proportional-integral controllers, were designed for the industrial evaporator system. The superiority of the geometric nonlinear control structure for regulatory control of the evaporator system was successfully demonstrated through computer simulations and real-time simulator implementation. The implementation trial has verified the practicality and feasibility of these type of controllers. It also re-solved some practical issues of the geometric nonlinear control structure for industrial control applications. In addition, the implementation trial also established a closer link between the academic nonlinear control theory and the industrial control practices.Geometric nonlinear output feedback controller, consisting of the geometric nonlinear control structure and reduce-order observer was proposed for actual plant implementation on the evaporator system on-site. Its superior performance was verified through computer simulations, but its feasibility on the evaporator system on-site has yet to be investigated either through simulator implementation or actual plant implementation. This investigation was not performed due to the time constraint on the preparation of this thesis and the inavailability of the plant personnel required for this implementation.Robust nonlinear control structures that are simple and computationally efficient have been proposed for enhancing the performance of geometric nonlinear controllers in the presence of plant/model mismatch and/or external disturbances. The robust nonlinear control structures are based on model error compensation methods. Robustness properties of the proposed robust nonlinear control structures on the evaporator system were investigated through computer simulations and the results indicated improved performance over the implemented geometric nonlinear controller in terms of model uncertainty and disturbance reductions.A software package was developed in MAPLE computing environment for the analysis of nonlinear processes and the design of geometric nonlinear controllers. This developed symbolic package is useful for obtaining fast and exact solutions for the analysis and design of nonlinear control systems. Procedures were also developed to simulate the geometric nonlinear control systems. It was found that MAPLE, while it is superior for the analyses and designs, is not viable for simulations of nonlinear control systems. This was due to limitation of MAPLE on the physical, or virtual, memory management. The use of both symbolic and numeric computation for solutions of nonlinear control system analysis, design and simulation is recommended.To sum up, geometric nonlinear controllers have been designed for an industrial multiple stage evaporator system and their simplicity, practicality, feasibility and superiority for industrial control practices have been demonstrated either through computer simulations or real-time implementation. It is hoped that the insights provided in this thesis will encourage more industry-based projects in nonlinear control, and thereby assist in closing the widening gap between academic nonlinear control theory and industrial control practice.Keywords: geometric nonlinear control, input-output linearization, multiple stage evaporator, robust geometric nonlinear control, control performance enhancement.
26
Ericksson, Cristiane. "Estudo de caso, replicação, padronização e otimização de técnicas de tratamento de gemas : processos de tingimento de ágata do Rio Grande do Sul." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/172053.
Abstract:
A ágata do sul do Brasil apresenta colorações pouco interessantes ou salientes, sendo predominante os tons acinzentados. Tais qualidades foram fatores determinantes para o início do processo de tingimento de ágata do Rio Grande do Sul, no século XVIII. Atualmente, o segmento mineral, apresenta carências relacionadas a tecnologias e processos de produção, além de infraestruturas inadequadas, resultando em prejuízo para as comunidades produtoras. Nesse cenário, a pesquisa se estrutura para avaliar técnicas operacionais viáveis para o setor, objetivando a melhoria do valor agregado às gemas beneficiadas e qualidade na cor. Para o desenvolvimento do tratamento de ágatas, o sistema foi replicado, padronizado e otimizado no Laboratório LAPROM da UFRGS e Centro Tecnológico de Pedras, Gemas e Joias do Rio Grande do Sul. A amostragem foi classificada em quatro padrões e analisada em espectrofotômetro em três etapas distintas. Ao término, se tem a comparação dos resultados do tingimento otimizado e o industrial, com as curvas de distribuição espectral medidas antes e após o tratamento termoquímico da ágata. Com o sistema otimizado, foi possível reduzir custos operacionais, tempo de energia envolvida no sistema, além de manter e elevar a qualidade da cor, sendo possível estabelecer relação com aspectos quanti e qualitativos dos reagentes utilizados.The agate of the south of Brazil presents not much interesting or salient colorations, being predominant the grayish tones. These qualities were determining factors for the beginning of the agate dyeing process in Rio Grande do Sul, in the 18th century. Currently, the mineral segment presents deficiencies related to technologies and production processes, as well as inadequate infrastructures, resulting in loss to the producing communities. In this scenario, the research is structured to evaluate viable operational techniques for the sector, aiming to improve the value added to the gems benefited and color quality. For the development of the agate treatment, the system was replicated, standardized and optimized in the LAPROM Laboratory of the UFRGS and Centro Tecnológico de Pedras, Gemas e Joias do Rio Grande do Sul. The sampling was classified in four standards and spectrophotometer analyzed in three different phases. In conclusion, is compared the optimized and industrialized dyeing results, with the spectral distribution curves measured before and after the thermochemical treatment of the agate. With the optimized system, it was possible to reduce operating costs, energy time involved in the system, as well as keep and elevate color quality and being possible to establish relationship with quantitative and qualitative aspects of the reagents used.
27
Schropp, Christian [Verfasser]. "Integrated mineral processing in underground mining operations and impact on the mine project / Christian Schropp." Düren : Shaker, 2019. http://d-nb.info/1198599790/34.
28
Kam, Kiew M. "Simulation and implementation of nonlinear control systems for mineral processes." Curtin University of Technology, School of Chemical Engineering, 2000. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=10063.
Abstract:
Differential geometric nonlinear control of a multiple stage evaporator system of the liquor burning facility associated with the Bayer process for alumina production at Alcoa Wagerup alumina refinery, Western Australia was investigated.Mathematical models for differential geometric analysis and nonlinear controller synthesis for the evaporator system were developed. Two models, that were structurally different from each other, were used in the thesis for simulation studies. Geometric nonlinear control structure, consisting of nonlinear state feedback control laws and multi-loop single-input single-output proportional-integral controllers, were designed for the industrial evaporator system. The superiority of the geometric nonlinear control structure for regulatory control of the evaporator system was successfully demonstrated through computer simulations and real-time simulator implementation. The implementation trial has verified the practicality and feasibility of these type of controllers. It also re-solved some practical issues of the geometric nonlinear control structure for industrial control applications. In addition, the implementation trial also established a closer link between the academic nonlinear control theory and the industrial control practices.Geometric nonlinear output feedback controller, consisting of the geometric nonlinear control structure and reduce-order observer was proposed for actual plant implementation on the evaporator system on-site. Its superior performance was verified through computer simulations, but its feasibility on the evaporator system on-site has yet to be investigated either through simulator implementation or actual plant implementation. This investigation was not performed due to the time constraint on the preparation of this thesis and the inavailability of the plant personnel required for this implementation.Robust ++nonlinear control structures that are simple and computationally efficient have been proposed for enhancing the performance of geometric nonlinear controllers in the presence of plant/model mismatch and/or external disturbances. The robust nonlinear control structures are based on model error compensation methods. Robustness properties of the proposed robust nonlinear control structures on the evaporator system were investigated through computer simulations and the results indicated improved performance over the implemented geometric nonlinear controller in terms of model uncertainty and disturbance reductions.A software package was developed in MAPLE computing environment for the analysis of nonlinear processes and the design of geometric nonlinear controllers. This developed symbolic package is useful for obtaining fast and exact solutions for the analysis and design of nonlinear control systems. Procedures were also developed to simulate the geometric nonlinear control systems. It was found that MAPLE, while it is superior for the analyses and designs, is not viable for simulations of nonlinear control systems. This was due to limitation of MAPLE on the physical, or virtual, memory management. The use of both symbolic and numeric computation for solutions of nonlinear control system analysis, design and simulation is recommended.To sum up, geometric nonlinear controllers have been designed for an industrial multiple stage evaporator system and their simplicity, practicality, feasibility and superiority for industrial control practices have been demonstrated either through computer simulations or real-time implementation. It is hoped that the insights provided in this thesis will encourage more industry-based projects in nonlinear control, and thereby assist in closing the widening gap between academic nonlinear control theory and industrial control ++
practice.Keywords: geometric nonlinear control, input-output linearization, multiple stage evaporator, robust geometric nonlinear control, control performance enhancement.
29
Harris, Jeff R. "Processing and integration of geochemical data for mineral exploration: Application of statistics, geostatistics and GIS technology." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6421.
Abstract:
Geographic Information Systems (GIS) used in concert with statistical and geostatistical software provide the geologist with a powerful tool for processing, visualizing and analysing geoscience data for mineral exploration applications. This thesis focuses on different methods for analysing, visualizing and integrating geochemical data sampled from various media (rock, till, soil, humus), with other types of geoscience data. Different methods for defining geochemical anomalies and separating geochemical anomalies due to mineralization from other lithologic or surficial factors (i.e. true from false anomalies) are investigated. With respect to lithogeochemical data, this includes methods to distinguish between altered and un-altered samples, methods (normalization) for identifying lithologic from mineralization effects, and various statistical and visual methods for identifying anomalous geochemical concentrations from background. With respect to surficial geochemical data, methods for identifying bedrock signatures, and scavenging effects are presented. In addition, a new algorithm, the dispersal train identification algorithm (DTIA), is presented which broadly helps to identify and characterize anisotropies in till data due to glacial dispersion and more specifically identifies potential dispersal trains using a number of statistical parameters. The issue of interpolation of geochemical data is addressed and methods for determining whether geochemical data should or should not be interpolated are presented. New methods for visualizing geochemical data using red-green-blue (RGB) ternary displays are illustrated. Finally data techniques for integrating geochemical data with other geoscience data to produce mineral prospectivity maps are demonstrated. Both data and knowledge-driven GIS modeling methodologies are used (and compared) for producing prospectivity maps. New ways of preparing geochemical data for input to modeling are demonstrated with the aim of getting the most out of your data for mineral exploration purposes. Processing geochemical data by sub-populations, either by geographic unit (i.e., lithology) or by geochemical classification and alteration style was useful for better identification of geochemical anomalies, with respect to background, and for assessing varying alteration styles. Normal probability plots of geochemical concentrations based on spatial (lithologic) divisions and Principal Component Analysis (PCA) were found to be particularly useful for identifying geochemical anomalies and for identifying associations between major oxide elements that in turn reflect different alteration styles. (Abstract shortened by UMI.)
30
Kan, Wen Hao. "The Development of Ferrous Metal Matrix Composites for Use in the Mining and Mineral Processing Industry." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/18272.
Abstract:
The mining and mineral processing industries feature very harsh service environments that often severely limit the service life of components and equipment used. High Cr white cast irons are usually the material of choice for many high wear applications that also require some amount of corrosion resistance. The excellent wear performance of these alloys is attributed to both a volume fraction of hard Cr carbides (a ceramic phase) and a hard, corrosion resistant ferrous matrix. These alloys present, however, poor fracture toughness. This thesis proposes that stainless steel matrix composites reinforced with ceramic particles that are harder than Cr carbides could potentially be viable alternatives to conventional high Cr white cast irons by being able to achieve greater wear performance with little detriment to corrosion resistance and toughness. As the eventual goal is for the manufacturing of large-scale mining components through direct melting and casting, the density of the ceramic particles used should be similar to that of molten steel to prevent the particles from sinking or floating. For this reason, Nb-based carbides are proposed as the reinforcements. Additionally, depending on the type of stainless steel matrix used, a wide range of mechanical and chemical properties are achievable, allowing these composites to be used in environments that are deemed unsuitable for high Cr white cast irons. This thesis shows that different stainless steel grades can be effectively reinforced with Nb-based carbides, with martensitic stainless steel composites easily surpassing the wear performance of high Cr white cast irons without compromising corrosion resistance despite having a lower volume fraction of ceramic reinforcement phases. The latter also implies a better toughness for the metal matrix composite.
31
Muryanto, Stefanus. "The role of impurities and additives in the crystallisation of gypsum." Thesis, Curtin University, 2002. http://hdl.handle.net/20.500.11937/2038.
Abstract:
Scale formation is one of the persistent problems in mineral processing and related industries. One of the main components of the scale is frequently gypsum or calcium sulphate dihydrate (= CaS04.2H20). Gypsum is formed through the process of crystallisation, and it is well known that crystallisation process is significantly affected by the presence of admixtures. Industrially, scale formation occurs in an environment which is very rarely free from the presence of admixtures. In a typical mineral processing industry, certain types of admixtures are present, which may include metallic ions (e.g. originated from corrosion products) and certain types of the flotation agents used. The effect of admixtures on crystallisation kinetics and cyclical morphology can be very significant, even if they are present in trace amounts. It is important to emphasise that the effects are generally specific, that there is no unified theory that applies to all and every situation. The present study has investigated the effect of certain admixtures on gypsum crystallisation, and was accomplished in three phases of experiments: (1) seeded batch crystallisation; (2) seeded continuous crystallisation, and (3) once through flow system under isothermal condition. The three phases of the work used equimolar solutions of CaC12 and Na2SO4 to produce CaS04 which is the precipitating species. The seeded batch crystallisation experiment explored the effect of two flotation agents commonly used in mineral processing plants: (1) sodium isopropyl xanthate (= SIPX) and, (2) isopropyl thionocarbamate. The experiments were performed at 25, 35, and 45°C, respectively. The initial concentration of the crystallising solution was 2,000 ppm of Ca 21 and it reached the equilibrium concentration values of between 1,000 and 8,00 ppm of Ca 2+ in 90 minutes.The effect of the two selected admixtures on crystallisation was measured by continuous monitoring of the desupersaturation of the crystallising solution with time, which subsequently resulted in the determination of the crystallisation rate constant. The results arc as follows. Firstly, the admixtures selected (either individually or in combination) were able to retard the growth rate of gypsum. In the absence of any admixture, the second order rate constant was between 1,405 x 10-6 and 1,561 x 10-6 ppm-1 min-1. Addition of SIPX at a typical plant dosing level 0.200 g/L) reduced the rate constant to 475 x 10-6 PPM-1 min', while isopropyl thionocarbamate at a typical plant dosing level (= 0.070 g/L) decreased the rate constant to 254 x 10-6 ppm-1 min-'. However, addition of a combination of the two admixtures, each at a typical plant concentration level, reduced the rate constant to 244 x 10-6 ppm-1 min-1, which was only slightly below that in the presence of isopropyl thionocarbamate. Thus, in these batch crystallisation studies, isopropyl thionocarbamate seemed to be dominant over SIPX. Secondly, the batch crystallisation system in the current work did not show any induction time. It was concluded that the seeds added into the batch system could be capable of eliminating the induction time. Thirdly, the reduced growth rate of the gypsum crystals as affected by the admixtures was probably caused by the adsorption of admixtures onto the crystal surface. The second phase of the project involved a seeded continuous (MSMPR) crystalliser. Some parameters used in this experiment (mean residence time, agitation speed and type of one admixture) were taken from the batch experiment carried out in the first phase of the project.Three admixtures were chosen for the seeded continuous crystallisation: (1) SIPX, (2) Fe3+, (3) Zn2-, and they were used either individually on in combination with each other. SIPX was chosen as it is one of the most common flotation agents used in mineral processing. Metallic ions: Fe3+ and Zn2+ were selected, since they were found in substantial amounts in both scale samples and process water in certain minerals processing industries. In general, the admixtures tested were found to be able to inhibit the crystal growth rates, but to enhance the nucleation rates. In addition, the growth rate was found to be dependent on crystal size, and hence, a correlation between these two parameters and the admixture concentration was formulated. For a fixed level of concentration (f 700 ppm of Ca z+ at steady state) and crystal surface area, it was proved that for each crystallisation temperature: 25 and 40°C, the correlation function can be represented as G = k Lα (1 +C)β where: G = linear growth rate, micron/hour; k, α, and β = dimensionless constants; L = (sphere equivalent) crystal size, micron; C = concentration of the admixtures used, ppm. For both the crystallisation temperatures used, the correlation function shows that the growth rate is significantly dependent on crystal size, but a weak function of admixture concentrations. The mechanism of crystal growth inhibition was assumed to be that of adsorption of admixtures onto the active growth sites, thereby decreasing or stopping the growth. Similar to the first phase of the present study, this seeded continuous crystallisation also showed no induction time. The third phase of the project investigated the gypsum scale formation in a oncethrough pipe flow system under isothermal condition and in the presence of admixtures.Four types of pipe materials were tested: PVC, brass, copper and stainless steel. Two admixtures were selected: SIPX and Fe3+. The behaviour of the gypsum scale formation was measured as the mass of the gypsum scale deposited on the substrate per unit area of the pipe surface. Within the range of the experimental conditions applied in this scale formation study, the following results were obtained. Firstly, the mass of the gypsum scale increased with concentration (in the range: 2,000 to 6,000 ppm of Ca t+) and that the correlation between the mass and the concentration can be represented by quadratic functions. Secondly, the mass of the gypsum scale decreased with increasing concentration of the admixtures used. Thirdly, the flow rate of the scaling solutions (in the range: 0.4 to 1.3 cm/sec) did not significantly affect the mass of the gypsum scale. PVC produced the highest mass of gypsum scale, followed by brass, copper, and stainless steel, respectively. Fourthly, the presence of admixtures caused the surface of the scale deposit to become rougher than was the case in a pure system, and longer scaling experimental times resulted in denser scale deposits. In this scale formation project, the induction time was investigated. In contrast with the first and the second phase of the projects, the induction time in the scale gypsum formation experiment was significant. At a concentration of 2,000 ppm of Ca 2+' pure gypsum solutions had induction times of about 105 minutes at 18.3°C and 97 minutes at 20.3°C. In the presence of 10 ppm of SIPX, the scaling solution at 2,000 ppm of Ca2+ and 19.2°C had an induction time of 1,400 minutes. The present study produced three important findings.Firstly, the presence of Fe 3+ or sodium isopropyl xanthate (SIPX) reduced the growth rate of gypsum crystallised either in a vessel (= a continuous crystalliser) or in a pipe flow system. Secondly, the rate of growth of gypsum crystals was found to be consistently higher in the vessel than in the pipe flow system. The rate of growth of the pure gypsum in the crystalliser at 25°C was 0.0389 kg/ m2 hour while those in the pipe flow system were between 0.0289 and 0.0202 kg/m2 hour, depending on the pipe material and the scaling solution flow rate. Thirdly, with respect to gypsum scaling, PVC was the least favourable material, followed by brass and copper, while the most favourable was stainless steel. It is believed that the present study has significantly contributed to the understanding of the effect of admixtures on crystallisation of gypsum, especially in relation to the scale formation.
32
Boshoff, Genevieve Ann. "Development of integrated biological processing for the biodesalination of sulphate- and metal-rich wastewaters." Thesis, Rhodes University, 1999. http://hdl.handle.net/10962/d1003958.
Abstract:
The substantial pollution threat to the South African environment from acid mine drainage (AMD) effluents has been well documented. Due to the juvenile nature of acidity in these flows, any remediation strategies implemented will need to function effectively and at low cost for long periods of time. The widespread use of sulphate reducing biological systems for the treatment of such effluents, and in particular large volume flows, has been limited. The supply of inexpensive electron donor and carbon sources, as well as appropriate reactor designs capable of handling large volume flows, have been identified as among the principal factors limiting development of this technology. The broad aim of the research programme reported here was to undertake an evaluation of the feasibility of an algal-bacterial integrated ponding system for the treatment of AMD, and the waste stabilisation pond (WSP) as an appropriate reactor design for this application. The study attempted to demonstrate the feasibility of individual unit operations in a proposed process train using complex organic carbon serving as the electron donor source for the sulphate reducing bacteria (SRB). Studies were undertaken as laboratory and pilot-scale investigations. Tannery effluent was shown to be a functional carbon source for biological sulphate reduction, with effective removal of sulphate and organics being recorded. In turn, the use of biological sulphate reduction for the treatment of tannery effluent was demonstrated. Algal biomass was shown in laboratory studies to function as an effective carbon source for biological sulphate reduction. It is known that micro-algae produce large quantities of photosynthate which is released to the growth medium under conditions of physiological stress. The potential for the use of photosynthate production in high rate algal ponding systems and its manipulation and use as a sustainable carbon source for sulphate reduction was investigated. Growth of a mixed culture of Dunaliella under conditions of light, temperature and salinity stress demonstrated production of large quantities of organic carbon. However, growth was inhibited at high temperatures. An elevation of salinity levels led to a decrease in growth of Dunaliella, but to increased organic carbon production. Spirulina spp., on the other hand, grew well at higher temperatures but showed the highest organic carbon production, and release to the medium, under low light conditions. These results led to a proposed process for the integration of algal ponding into an integrated system for the treatment of AMD. The algal biomass may be fed into the anaerobic digester as a carbon source, or it may be passed into a High Rate Algal Pond (HRAP) where it is stressed to enhance the organic carbon content. This can then be fed into the anaerobic digester as a carbon source. The impact of high levels of sulphide in the water feeding to the algal growth compartment was investigated. Spirulina spp. isolated from a tannery waste stabilisation pond was shown to be a sulphidophilic strain of cyanobacterium, capable of being adapted to high concentrations of sulphide. Dunaliella salina on the other hand was less tolerant. These results demonstrated the practical use of algal biomass providing an oxygen-rich cap for odour control on the surface of the facultative pond as well for the secondary treatment of sulphide-rich overflow to the High Rate Algal Pond. The ability of micro-algae to elevate the pH of their surrounding environment was evaluated as a functional precipitant and neutralisation reagent for acidic metal containing wastewater. Spirulina spp. was shown to perform effectively. D. salina was less functional in this environment. Anacystis spp. was effective in elevating the pH of a defined medium as well as a zinc-rich effluent. These results indicated the practicality of a neutralising function for algal ponds in the treatment of AMD. Metal removal in the system was found to be a combined function of sulphide precipitation, removal by binding to micro-algal biomass and extracellular polymeric substances. The feasibility of waste stabilisation ponding technology use for the treatment of large volume AMD effluents was provisionally demonstrated. It was shown that complex carbon sources would be used as efficient electron donors for sulphate reduction. The integration of algal ponding into the system provides for the generation of a sustainable carbon source, odour control with the recycling of oxygen-rich water onto the top of the facultative pond, secondary treatment of the anaerobic digester overflow, and the neutralisation of the incoming acidic effluents and removal of heavy metals. Integration of the individual unit operations, the feasibility of which has been provisionally demonstrated in this study, into a continuous process train is being investigated in follow-upstudies.
33
Gantenbein, Daniel. "Development of mineral particle surfaces for the adsorption of pitch from wood processing and recycling of paper." Thesis, University of Plymouth, 2012. http://hdl.handle.net/10026.1/1175.
Abstract:
During the production of paper in paper mills, detrimental wood resin is released into the water circuit of the mill during the pulping process of the wood into fibres. This wood resin, termed pitch, can detrimentally deposit on the paper and on the paper machine equipment. The deposits mark the paper or can lead to a tear of the paper web involving a loss of output and a reduction in paper quality. Furthermore, the wood resinous compounds in paper mill effluents need to be reduced in order to minimise their toxic effects on water organisms. Talc has been the benchmark for many years as a mineral additive in pitch control. Since the papermaking process has changed over the years, the concept of mineral addition needs to be redefined and adopted towards the new circumstances. By understanding the fundamentals behind the adsorption of wood resin compounds from aqueous systems on to talc new mineral additives can be developed. A model for the determination of the aspect ratio of platy and rod-like particles has been developed, based on commonly available characterisations such as particle size, specific surface area and shape. It was found that the adsorption capacity of a mineral is directly proportional to its specific surface area, but only within its mineral family. Including the effect of surface hydrophilicity and hydrophobicity allowed fine tuning of the adsorption capacity of newly developed calcium carbonate grades. Furthermore, size exclusion effects, in porous, high surface area modified calcium carbonate, were seen to hinder complete coverage of the surface area by wood resin. With increasing pH, the adsorption efficiency of talc for colloidal wood resin was found to decrease. Under these alkaline conditions, which are common in modern paper making processes, talc preferentially adsorbed dissolved species. The use of the newly developed surface treated and modified calcium carbonates allowed more efficient adsorption of the colloidal fraction and, therefore, represent an efficient alternative to talc in pitch control. An increase in temperature led to an increased adsorption capacity of talc. This observation indicates the type of interaction tat controls the adsorption of hydrophobic pitch particles onto talc, i.e. the entropically favoured release of water from the hydrophobic talc surface as well as the hydrophobic methylene backbone of the hemicellulose.
34
Cruz, Eva Brunilda. "A Comprehensive Dynamic Model of the Column Flotation Unit Operation." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30748.
Abstract:
The core of this project was the development of a column flotation dynamic model that can reasonably predict the changes in the concentrations of all solid and bubble species, along the full column height. A dynamic model of a process is normally composed of a set of partial or ordinary differential equations that describe the state of the process at any given time or position inside the system volume. Such equations can be obtained from fundamental material and/or energy balances, or from phenomenological derivations based on knowledge about the behavior of the system. A phenomenological approach referred to as population balance modeling was employed here.
Initially, a two-phase model was formulated, which represents the behavior of the gas phase in a frother solution. The column was viewed as consisting of three main regions: a collection region, a stabilized froth and a draining froth. Experiments were carried out, based on conductivity techniques, for obtaining empirical data for model validation and parameter estimation. After testing the two-phase model, the equations for the solid species were derived. Consideration of the effects of bubble loading, slurry density and slurry viscosity on bubble rise velocity and, therefore, on air fraction is included in the model. Bubble coalescence in the froth is represented as a rate phenomenon characterized by a series of coalescence efficiency rate parameters. Auxiliary equations that help describe the settling of free particles, the buoyancy of air bubbles, and the processes of attachment and detachment, were also developed and incorporated into the model. The detachment of solids from the bubbles in the froth zones was attributed to coalescence, and it was assumed to be proportional to the net loss of bubble surface area.
Almost all parameters needed to solve the model equations are readily available. The set of differential equations that comprise the model can be solved numerically by applying finite difference approximation techniques. An iteration has to be performed, which involves calculating the product flowrate at steady state, modifying the tailings rate and solving the model again until a mass balance is satisfied.Ph. D.
35
Al-Ali, Safaa Hussein Ali. "Mineralogy and mineral processing to optimise recovery of synchysite-(Ce) and apatite from carbonatite at Songwe Hill, Malawi." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/28823.
Abstract:
Rare earth elements (REE) are considered as critical and non-substitutable metals for electronics and green technology. A greater diversity of supply is needed and the REE occur in a wide range of REE- and REE-bearing minerals within different ore deposit types. The beneficiation processes for REE ores can vary widely based on their mineralogy and texture. It is, therefore, essential to understand the mineralogical characteristics when designing processing routes. Little research was carried out on this topic until the last few years, apart from bastnäsite, monazite, and xenotime, and most REE minerals in deposits currently under exploration are poorly understood in terms of processing characteristics. This geometallurgical study brings together the results of process mineralogy and minerals processing to recover synchysite-(Ce) and apatite from the carbonatite at Songwe Hill, Malawi. This deposit is unusual because it is a potential carbonatite source of both LREE and HREE. Results from previous flowsheet development studies on this deposit suggest that flotation is the most promising processing route and therefore this study concentrated on testing this hypothesis. It sought to understand the mineralogy better in order to predict processing response and carried out a series of flotation experiments to improve the processing efficiency. It also investigated the fundamental magnetic properties of the rare earth fluorcarbonate minerals (including synchysite) and established for the first time that there is a systematic variation in their properties that can be applied to minerals processing. Eight samples of REE carbonatite drill core, crushed to 1700 μm, and a composite sample ground to 53 μm and 38 μm were used throughout this research. Automated mineralogy (QEMSCAN®) was applied to determine the mineralogical characteristics of the ore deposit. This utilised a novel species identification protocol (SIP) for REE minerals in carbonatites, which was validated by electron microscopy (SEM-EDS), and electron probe microanalysis (EPMA). The principal REE minerals at Songwe are the REE fluorcarbonates, synchysite-(Ce) and also parisite-(Ce). These are challenging minerals for automated mineralogical techniques owing to their chemical similarity and common occurrence either as bladed (needle-like) crystals, which is the main textural type at Songwe Hill, or as syntaxial intergrowths. However, using the SIP developed in this study, the QEMSCAN® can distinguish between these minerals based on the Ca content and can also recognise syntaxial intergrowths on a scale of about > 20 μm. The Songwe Hill carbonatite hosts about 6 wt% to 10 wt% of REE- and REE-bearing minerals. Apatite hosts the more valuable HREE in addition to P2O5, followed by synchysite-(Ce)/parisite-(Ce) (mainly synchysite-(Ce)), and minor florencite-(Ce), which host the LREE. These minerals are commonly associated with the predominant gangue minerals, ankerite and calcite, and, to a lesser extent Fe- Ox/CO3 and K-feldspar, strontianite and baryte. Fundamental magnetic properties of pure REE fluorcarbonate single crystal minerals using a vibrating sample magnetometer (VSM) were determined. The magnetic susceptibility is highly dependent on the mineral composition. It is positive (paramagnetic) for bastnäsite-(Ce) and gradually decreases as the amount of Ca increases in parisite-(Ce), becoming negative (diamagnetic) for the Ca-rich member of the series, röntgenite. Synchysite-(Ce) in this deposit was experimentally determined by magnetic separation and behaved as a diamagnetic mineral. This can be explained by the layered structure common to the REE fluorcarbonate series minerals. Selected laboratory scale mineral processing experiments including magnetic separation and froth flotation were performed. Pre-concentration tests by magnetic separation showed a recovery of 84% for P2O5, 80% for Y2O3, and 76% for Ce2O3 in the non-magnetic product, with gangue minerals rejection of about 49% for ankerite and 48% for Fe-Ox/CO3 to the magnetic product. Apatite and synchysite-(Ce) loss to the magnetic product is mainly the result of their association with the paramagnetic minerals i.e. ankerite and Fe-Ox/CO3 as indicated by automated mineralogy. A spectrophotometer was utilised to measure the solubility of the organic chemical reagents including fatty acids and lignin sulphonate in different alkaline solutions and to determine the appropriate operating parameters for bench flotation tests. The results indicated that the solubility of fatty acids increased with increasing the pH value from 8.5 to 10.5, while the opposite was observed for lignin sulphonate. 35 bench-scale froth flotation tests under a wide range of chemical and operating conditions including pH modifiers and dosages, soluble and insoluble collectors, depressants, temperature, and conditioning time were performed. The results demonstrated that fatty acids and lignin sulphonate are sensitive to changes in pH, conditioning time, and temperature. These factors significantly affected flotation efficiency. A recovery of 86% for P2O5 and 74% for both of Y2O3 and Ce2O3 with TREO upgrading from 1.6 wt% to 3.8 wt% at a mass pull of 31% were achieved under a constant pulp pH of 9.5, elevated temperature, and long conditioning time. This study suggests that combining magnetic separation and froth flotation techniques to pre-concentrate and upgrade the REE- and REE-bearing minerals, should be considered further to minimise the cost of the chemical reagents used in froth flotation and gangue leaching.
36
Soto, Chris. "Do Clay Minerals affect the thickener operationin Chuquicamata mine, Calama, Chile?" Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-77458.
Abstract:
Chuquicamata mine mineralogy has been studied performing both X-Ray Diffraction (XRD) and X-RayFluorescence (XRF) to determine whether there is any influence in the thickener operations. Thetargeted minerals were the clay group because of their detrimental effect on mining operations asmodify the rheology of the suspensions. The operation stages most affected by the presence of the clayminerals are gravity separation, milling, conveyor belts, flotation and specially thickener operations. Inorder to cope with Chuquicamata production, the plant is constantly fed from a neighboring ore calledRadomiro Tomic (RT) ore, a secondary sulfide enrichment. At Chuquicamata, the thickener operatorfeedback has been pointed out that every time the concentrator plant is fed in high ratio with this so-called RT ore the mineral processing is hindered. For this reason, RT ore samples from a criticaloperation day were sent to Sweden for mineralogical analysis. In addition, flotation tailings from thethree Chuquicamata concentrator plants were also sent aimed to perform thickener pilot tests. In thismanner, it was seen if it could be possible to achieve new operational strategies in Chuquicamatathickener operations given the current Chuquicamata mineralogy and physical conditions in the flotationtailings.From the XRD analysis, the following clay minerals were identified in order of abundance: Illite>>Kaolinite>SmectiteThus, illite reached up to 23.3vol% being the highest clay amount, followed by lower case kaolinite up to2.5% and up to 1% of smectite values correspond for the RT sample. However, the clay content in theflotation tailings samples were less than expected. Also, clay Crystallinity was also assessed for its abilityto interfere negatively with the pulp rheology, and the results showed that there is a strong link amongpoor crystallized smectite clay with the semi-autogenous mill compare to those samples where themilling was performed in the traditional steel media. Along with the three clay minerals found, quartz,potassic feldspar, and plagioclase were also identified, accounting for up to 76% of the representativesample. The silicate minerals are thought to be problematic in Chuquicamata thickener operations givenits high amount, especially in <2 µm size.For the thickener tests, three types of polyacrylamide were used plus the current Chuquicamataflocculant. Prior to the sedimentation batch test, the rheology of the flocculants was measured in arange of 0.02%w/w to 1%. It was found that flocculant concentrations between 0.02 to 0.05%w/w themost suitable in terms of avoiding suspension rheology increase. After establishing suitable flocculantconcentrations solutions, these were used in the thickener pilot tests at conditions similar to thoseperformed in Chuquicamata thickener operations. Two criteria were used to analyze the bestsedimentation conditions: Initial settling rate (ISR); and Turbidimeter. At pH in a range of 11-12 and 15%solid, bridging flocculation probed to be the most suitable conditions for Chuquicamata thickeneroperations. Moreover, a polyacrylamide blend was tested aiming to achieve high sedimentationperformances. The flocculant blend reached both the highest initial sedimentations rate up to 48m/hand turbidity values below 20NTU at addition rate 5g/t and 7g/t. On the other hand, Chuquicamatacurrent flocculant only reached the highest values of 36m/h and turbidity of 40NTU at an addition rateof 5g/t. In this way, the current work established that conditions at Chuquicamata thickener operation 4can be improved by understanding the absorption process among particle-polymer and mineralogy ofthe mine.Hence, the implication of this work to Chuquicamata mine is a better knowledge of its mineralogyespecially concerned with it is believed that clay minerals are not the only mineralogical factors thatcould be hindering thickener operations in Chuquicamata. Other factors that also could be problematicare: high content of silicates; clay crystallinity, particle size and mixed clay. In addition, the improvementin the thickener sedimentation operations will bring better use of the water by increasing therecirculation towards the concentrator area in a friendly way with the environment and communitiesthat also demand water in the arid region of the Atacama Desert.
37
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.
Abstract:
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).
38
Cai, Wenlong. "Application of network flow and zero-one programming to open pit mine design problems." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184797.
Abstract:
An algorithm which adopts a moving cone approach but is guided by maximal network flow principles is developed. This study argues that from a network flow point of view, the re-allocation problem is a major obstacle to prevent a simulation oriented pit design algorithm from reaching the optimum solution. A simulation oriented pit design algorithm can not resolve the re-allocation problem entirely without explicit definition of predecessors and successors. In order to preserve the advantages of moving cone algorithm and to improve the moving cone algorithm, the new algorithm trys to avoid the re-allocation situations. Theoretical proof indicates that the new algorithm can consistently generate higher profit than the popular moving cone algorithm. A case study indicates that the new algorithm improved over the moving cone algorithm (1% more profit). Also, the difference between the new algorithm and the rigorous Lerchs-Grossmann algorithm in terms of generated profit is very insignificant (0.015% less). The new algorithm is only 2.08 times slower than the extremely fast moving cone algorithm. This study also presents a multi-period 0-1 programming mine sequencing model. Once pushbacks are generated and the materials between a series of cutoffs are available for each bench of every pushback, the model can quickly answer, period by period, what is the best (maximum or minimum) that can be expected on any one of these four items: mineral contents, ore tonnages, waste tonnages and stripping ratios. This answer is based on a selected cutoff and considers the production capacity defined by the ore tonnage, the desired stripping ratio and the precedence constraints among benches and pushbacks. The maximization of mineral contents is suggested to be the direct mine sequencing objective when it is permissible. Suggestions also are provided on how to reduce the number of decision variables and how to reduce the number of precedence constraints. A case study reveals that the model is fast and operational. The maximization of mineral contents increases the average grades in early planning periods.
39
Opoubou-Lando, Serge-Driver. "Mineralogical characterisation of chromite in the UG2 Reef from Waterval Mine, Western bushveld : implications for minerals processing." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4380.
Abstract:
Thesis (MSc (Earth Sciences))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: The Bushveld Complex of South Africa contains three of the most important platinum deposits in the world namely the Merensky Reef, the Upper Group Two (UG2) chromitite reef and the Platreef. These three ore bodies are principally beneficiated by froth flotation. During the beneficiation of chromite hosted PGE’s by froth flotation, chromite represents the principal gangue mineral. This is particularly true for the UG2 main seam. An excess of more than 3% in mass of chromite in the PGM concentrate is known to result in significant problems in the downstream processing and extraction of PGEs. The variability in texture and composition of chromite due to its primary crystallization and subsequent modification by the development of potholes or through IRUP intrusions are thought to influence the flotation behaviour of the UG2 main seam chromitite ore. This study conducted at Waterval Mine investigated the role of mineralogical characteristics of chromites on the flotation performance of three different environments for the UG2 main seam: (1) “normal” UG2 main seam; (2) UG2 main seam affected by pothole formation; and (3) UG2 main seam affected by IRUP intrusion. This was achieved through an extensive petrographic investigation of the chromites from each environment, to individually characterise their primary textures. This was followed by compositional characterisation of the chromite from each environment. Finally the flotation performance of the ore from each environment was investigated, using small scale batch flotation experiments, to establish any linkage between the textures, the composition and the flotation performance of the chromite from different environments. In this study it was found that the UG2 normal reef and the UG2 reef affected by pothole formation are both principally characterised by primary mineralogical features comprising mainly fine‐grained chromite as the cumulate phase and orthopyroxene and plagioclase as intercumulate phases. These two reef types were also found to be identical in the composition of the chromites present. In addition, in both of these almost unaltered reef types it was found that chromite showed small recoveries by flotation. On the other hand, it was found that the UG2 affected by IRUP intrusion was affected by post‐magmatic alteration that had overprinted primary textures and compositional features. This resulted in the replacement of primary minerals by secondary alteration assemblages. Orthopyroxene was iii replaced by serpentine, chlorite, amphibole and talc, while plagioclase is replaced by sericitic alteration. Furthermore, this alteration also resulted in modification of the chromite compositions. The compositional change in the chromites from the IRUP reef type resulted in Fe and Ti enrichment of chromite with increasing magnetic properties, and Cr, Al and Mg depletion. The alteration also resulted in the coarsening of chromite in the IRUP affected main seam reef particularly at the bottom and the top of the main seam. These compositional and textural modifications, principally the post‐magmatic alteration of intercumulate orthopyroxene, resulted in a greater recovery of chromite by flotation in the concentrate from the IRUP affected ore compared to the two other two ore types where there was small amount of chromite recovered. The characterisation of the recovered chromite revealed that the principal reason for chromite flotation was caused by the mineral association of chromite with hydrophobic Si, Mg, Fe rich phases, principally altered orthopyroxene and associated serpentine, chlorite, amphibole and talc. This investigation showed that the difference in mineralogical and flotation performances of chromite from the different UG2 main seam reef types was caused by the postcrystallisation alteration of cumulate and intercumulate phases due to the emplacement of IRUPs. Although IRUP affected UG2 main seam ore is not currently processed, it could be processed much more rapidly than the other two types of UG2 main seam ores because of its softer character resulting in shorter milling times. This is most likely a function of the presence of alteration phases and the presence of coarser chromite grains, as well as already brecciated chromite grains. Savings associated with the shorter milling time of this ore type are perhaps offset by the cost of the higher dosages of depressant required to suppress the floatable chromite in this ore type. However, given the energy cost of longer milling times, the cost of the depressant is likely to be insignificant. Moreover, the processing of the UG2 main seam ore affected by IRUP intrusion would also require a different approach to extraction of the ore to keep it separate from the normal reef ore.
40
Shashikala, A. R. "Role Of Interfacial Phenomena In Bioprocessing Of Minerals Using Bacillus Polymyxa." Thesis, Indian Institute of Science, 2001. https://etd.iisc.ac.in/handle/2005/246.
Abstract:
In recent years there has been growing interest in bio-mineral processing due to its low operating costs and its application in processing lean-grade ores. Bioprocessing is a good alternative to conventional hydrometallurgy process in mineral processing. In recent times microorganisms have been used as surface modifiers in processes such as froth flotation and flocculation. The surface properties of microbes and minerals such as zeta potential and surface hydrophobicity play a major role in determining adhesion of microorganisms to minerals and hence, the efficiency of flocculation and flotation. These properties also depend on solution conditions such as pH and ionic strength. Adhesion of microorganisms to mineral surfaces can alter the surface properties of the minerals. Such surface modification imparting hydrophobicity or hydrophilicity is used in flocculation and flotation of fine particles.
In this research work the effect of ionic strength and pH in deteraiining the surface properties and hence adhesion of the bacterium Bacillus polymyxa to minerals such as hematite, quartz and coal has been studied in detail. The effect of the ionic strength and pH on the electrokinetics of the minerals and bacteria and its subsequent effect on adhesion and flocculation were investigated in detail. Contact angle measurements along with the zeta potential results were used to calculate the interaction energies between the mineral and the microorganism to establish a mechanism for the interaction.
The following major conclusions can be drawn from this study. Results indicate that increase in the ionic strength significantly changes the zeta potential of hematite and bacteria without varying the isoelectric point. Increase in the ionic strength caused very little change in the zeta potential of quartz and coal. The adhesion of bacterial cells on to the minerals was found to be dependent on pH, ionic strength and conditioning time. Adhesion of bacterial cells was found to be more on hematite and coal when compared to quartz. The adsorption isotherms of Bacillus polymyxa cells with respect to all the three minerals were found to obey Langmuir isotherm. Flocculation studies demonstrated that the settling rate of hematite and coal was enhanced in presence of bacterial cells and electrolyte. However quartz settled much slower under the same conditions indicating that the quartz particles are being dispersed. Thus, selective flocculation of hematite and coal is possible which can be used in separating them from quartz effectively.
The different components of total interaction energy arising from Lifshitz-van der Waal forces, acid/base forces and electrostatic forces were calculated using the van Oss approach. Calculation of the components of the acid base free energy showed that coal and hematite were hydrophobic compared to quartz and the bacterium. From total interaction energy calculation based on the extended DLVO theory, hematite and coal were found to have a net negative interaction energy in acidic pH values and hence attractive forces are predominant. Quartz was found to have a net repulsive energy at all the pH values at low ionic strengths but increase in ionic strength the interaction energy become attractive. The AGLW values of quartz was found to be attractive which is probably responsible for bacterial adhesion onto quartz.
41
Shashikala, A. R. "Role Of Interfacial Phenomena In Bioprocessing Of Minerals Using Bacillus Polymyxa." Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/246.
Abstract:
In recent years there has been growing interest in bio-mineral processing due to its low operating costs and its application in processing lean-grade ores. Bioprocessing is a good alternative to conventional hydrometallurgy process in mineral processing. In recent times microorganisms have been used as surface modifiers in processes such as froth flotation and flocculation. The surface properties of microbes and minerals such as zeta potential and surface hydrophobicity play a major role in determining adhesion of microorganisms to minerals and hence, the efficiency of flocculation and flotation. These properties also depend on solution conditions such as pH and ionic strength. Adhesion of microorganisms to mineral surfaces can alter the surface properties of the minerals. Such surface modification imparting hydrophobicity or hydrophilicity is used in flocculation and flotation of fine particles.
In this research work the effect of ionic strength and pH in deteraiining the surface properties and hence adhesion of the bacterium Bacillus polymyxa to minerals such as hematite, quartz and coal has been studied in detail. The effect of the ionic strength and pH on the electrokinetics of the minerals and bacteria and its subsequent effect on adhesion and flocculation were investigated in detail. Contact angle measurements along with the zeta potential results were used to calculate the interaction energies between the mineral and the microorganism to establish a mechanism for the interaction.
The following major conclusions can be drawn from this study. Results indicate that increase in the ionic strength significantly changes the zeta potential of hematite and bacteria without varying the isoelectric point. Increase in the ionic strength caused very little change in the zeta potential of quartz and coal. The adhesion of bacterial cells on to the minerals was found to be dependent on pH, ionic strength and conditioning time. Adhesion of bacterial cells was found to be more on hematite and coal when compared to quartz. The adsorption isotherms of Bacillus polymyxa cells with respect to all the three minerals were found to obey Langmuir isotherm. Flocculation studies demonstrated that the settling rate of hematite and coal was enhanced in presence of bacterial cells and electrolyte. However quartz settled much slower under the same conditions indicating that the quartz particles are being dispersed. Thus, selective flocculation of hematite and coal is possible which can be used in separating them from quartz effectively.
The different components of total interaction energy arising from Lifshitz-van der Waal forces, acid/base forces and electrostatic forces were calculated using the van Oss approach. Calculation of the components of the acid base free energy showed that coal and hematite were hydrophobic compared to quartz and the bacterium. From total interaction energy calculation based on the extended DLVO theory, hematite and coal were found to have a net negative interaction energy in acidic pH values and hence attractive forces are predominant. Quartz was found to have a net repulsive energy at all the pH values at low ionic strengths but increase in ionic strength the interaction energy become attractive. The AGLW values of quartz was found to be attractive which is probably responsible for bacterial adhesion onto quartz.
42
Lira, Bonates Eduardo Jorge. "Analysis of truckshovel dispatching policies using computer simulation." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65406.
43
Muryanto, Stefanus. "The role of impurities and additives in the crystallisation of gypsum." Curtin University of Technology, Department of Chemical Engineering, 2002. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14305.
Abstract:
Scale formation is one of the persistent problems in mineral processing and related industries. One of the main components of the scale is frequently gypsum or calcium sulphate dihydrate (= CaS04.2H20). Gypsum is formed through the process of crystallisation, and it is well known that crystallisation process is significantly affected by the presence of admixtures. Industrially, scale formation occurs in an environment which is very rarely free from the presence of admixtures. In a typical mineral processing industry, certain types of admixtures are present, which may include metallic ions (e.g. originated from corrosion products) and certain types of the flotation agents used. The effect of admixtures on crystallisation kinetics and cyclical morphology can be very significant, even if they are present in trace amounts. It is important to emphasise that the effects are generally specific, that there is no unified theory that applies to all and every situation. The present study has investigated the effect of certain admixtures on gypsum crystallisation, and was accomplished in three phases of experiments: (1) seeded batch crystallisation; (2) seeded continuous crystallisation, and (3) once through flow system under isothermal condition. The three phases of the work used equimolar solutions of CaC12 and Na2SO4 to produce CaS04 which is the precipitating species. The seeded batch crystallisation experiment explored the effect of two flotation agents commonly used in mineral processing plants: (1) sodium isopropyl xanthate (= SIPX) and, (2) isopropyl thionocarbamate. The experiments were performed at 25, 35, and 45°C, respectively. The initial concentration of the crystallising solution was 2,000 ppm of Ca 21 and it reached the equilibrium concentration values of between 1,000 and 8,00 ppm of Ca 2+ in 90 minutes.The effect of the two selected admixtures on crystallisation was measured by continuous monitoring of the desupersaturation of the crystallising solution with time, which subsequently resulted in the determination of the crystallisation rate constant. The results arc as follows. Firstly, the admixtures selected (either individually or in combination) were able to retard the growth rate of gypsum. In the absence of any admixture, the second order rate constant was between 1,405 x 10-6 and 1,561 x 10-6 ppm-1 min-1. Addition of SIPX at a typical plant dosing level 0.200 g/L) reduced the rate constant to 475 x 10-6 PPM-1 min', while isopropyl thionocarbamate at a typical plant dosing level (= 0.070 g/L) decreased the rate constant to 254 x 10-6 ppm-1 min-'. However, addition of a combination of the two admixtures, each at a typical plant concentration level, reduced the rate constant to 244 x 10-6 ppm-1 min-1, which was only slightly below that in the presence of isopropyl thionocarbamate. Thus, in these batch crystallisation studies, isopropyl thionocarbamate seemed to be dominant over SIPX. Secondly, the batch crystallisation system in the current work did not show any induction time. It was concluded that the seeds added into the batch system could be capable of eliminating the induction time. Thirdly, the reduced growth rate of the gypsum crystals as affected by the admixtures was probably caused by the adsorption of admixtures onto the crystal surface. The second phase of the project involved a seeded continuous (MSMPR) crystalliser. Some parameters used in this experiment (mean residence time, agitation speed and type of one admixture) were taken from the batch experiment carried out in the first phase of the project.
Three admixtures were chosen for the seeded continuous crystallisation: (1) SIPX, (2) Fe3+, (3) Zn2-, and they were used either individually on in combination with each other. SIPX was chosen as it is one of the most common flotation agents used in mineral processing. Metallic ions: Fe3+ and Zn2+ were selected, since they were found in substantial amounts in both scale samples and process water in certain minerals processing industries. In general, the admixtures tested were found to be able to inhibit the crystal growth rates, but to enhance the nucleation rates. In addition, the growth rate was found to be dependent on crystal size, and hence, a correlation between these two parameters and the admixture concentration was formulated. For a fixed level of concentration (f 700 ppm of Ca z+ at steady state) and crystal surface area, it was proved that for each crystallisation temperature: 25 and 40°C, the correlation function can be represented as G = k Lα (1 +C)β where: G = linear growth rate, micron/hour; k, α, and β = dimensionless constants; L = (sphere equivalent) crystal size, micron; C = concentration of the admixtures used, ppm. For both the crystallisation temperatures used, the correlation function shows that the growth rate is significantly dependent on crystal size, but a weak function of admixture concentrations. The mechanism of crystal growth inhibition was assumed to be that of adsorption of admixtures onto the active growth sites, thereby decreasing or stopping the growth. Similar to the first phase of the present study, this seeded continuous crystallisation also showed no induction time. The third phase of the project investigated the gypsum scale formation in a oncethrough pipe flow system under isothermal condition and in the presence of admixtures.
Four types of pipe materials were tested: PVC, brass, copper and stainless steel. Two admixtures were selected: SIPX and Fe3+. The behaviour of the gypsum scale formation was measured as the mass of the gypsum scale deposited on the substrate per unit area of the pipe surface. Within the range of the experimental conditions applied in this scale formation study, the following results were obtained. Firstly, the mass of the gypsum scale increased with concentration (in the range: 2,000 to 6,000 ppm of Ca t+) and that the correlation between the mass and the concentration can be represented by quadratic functions. Secondly, the mass of the gypsum scale decreased with increasing concentration of the admixtures used. Thirdly, the flow rate of the scaling solutions (in the range: 0.4 to 1.3 cm/sec) did not significantly affect the mass of the gypsum scale. PVC produced the highest mass of gypsum scale, followed by brass, copper, and stainless steel, respectively. Fourthly, the presence of admixtures caused the surface of the scale deposit to become rougher than was the case in a pure system, and longer scaling experimental times resulted in denser scale deposits. In this scale formation project, the induction time was investigated. In contrast with the first and the second phase of the projects, the induction time in the scale gypsum formation experiment was significant. At a concentration of 2,000 ppm of Ca 2+' pure gypsum solutions had induction times of about 105 minutes at 18.3°C and 97 minutes at 20.3°C. In the presence of 10 ppm of SIPX, the scaling solution at 2,000 ppm of Ca2+ and 19.2°C had an induction time of 1,400 minutes. The present study produced three important findings.
Firstly, the presence of Fe 3+ or sodium isopropyl xanthate (SIPX) reduced the growth rate of gypsum crystallised either in a vessel (= a continuous crystalliser) or in a pipe flow system. Secondly, the rate of growth of gypsum crystals was found to be consistently higher in the vessel than in the pipe flow system. The rate of growth of the pure gypsum in the crystalliser at 25°C was 0.0389 kg/ m2 hour while those in the pipe flow system were between 0.0289 and 0.0202 kg/m2 hour, depending on the pipe material and the scaling solution flow rate. Thirdly, with respect to gypsum scaling, PVC was the least favourable material, followed by brass and copper, while the most favourable was stainless steel. It is believed that the present study has significantly contributed to the understanding of the effect of admixtures on crystallisation of gypsum, especially in relation to the scale formation.
44
Toledo, Nataly Maria Viva de. "Use of fruit processing by-products for the development of cookies: physicochemical, nutritional, technological and sensory aspects." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/11/11141/tde-13032019-181241/.
Abstract:
The present study aimed at characterizing pineapple, apple and melon by-products and evaluating their potential as an ingredient for the partial substitution of wheat flour in cookie formulations. The addition of fruit by-products contributed to rise the cookies fiber content. Melon by-product was prominent for its mineral content, whereas apple by-product presented more relevant results for phenolic compounds and antioxidant capacity (DPPH and ABTS). Such behaviors reflected in the cookie formulations. Eight phenolic compounds (vanillic acid, gallic acid, sinapic acid, salicylic acid, p-coumaric acid, catechin, epicatechin and rutin) were identified and quantified by HPLC in both the by-products and cookies. Regarding the antinutritional factors and mineral bioavailability, it was observed that the addition of fruit by-products in cookies reduced the contents of phytate and oxalate and promoted changes in calcium, iron and zinc bioavailability. Facing the technological aspects, it was observed that the use of by-products interfered in the color of the cookies, making them slightly darker and also weakened the gluten formed, promoting variations in diameter and expansion factor. On the other hand, it was observed that increasing concentrations of by-products led to higher values of hardness, making the cookies firmer and crunchier. In the sensory point of view, it was verified that the cookie with 15% of pineapple by-product demonstrated the highest acceptance, followed by cookies with 15% of apple by-product, control and 15% of melon by-product. By quantitative descriptive analysis (QDA), it was found that the addition of fruit by-products altered the sensory profile of the cookies. From the results obtained, it can be concluded that the fruit by-products are potential ingredients for cookie formulation, attributing to them specific physicochemical, technological, nutritional and sensory properties which can vary according to the by-products employed.O presente estudo visou caracterizar subprodutos de abacaxi, maçã e melão e avaliar seu potencial como ingrediente para substituição parcial de farinha de trigo em formulações de biscoitos. A adição de subprodutos de frutas contribuiu para elevar o teor de fibras dos biscoitos. O subproduto de melão se destacou por seu conteúdo mineral, enquanto que o subproduto de maçã apresentou resultados mais relevantes para compostos fenólicos e capacidade antioxidante (DPPH e ABTS). Tais comportamentos se refletiram nas formulações de biscoitos. Oito compostos fenólicos (ácido vanílico, ácido gálico, ácido sinápico, ácido salicílico, ácido p-cumárico, catequina, epicatequina e rutina) foram identificados e quantificados por HPLC tanto nos subprodutos como nos biscoitos. Com relação aos fatores antinutricionais e biodisponibilidade mineral, observou-se que a adição de subprodutos de frutas em biscoitos diminuiu os teores de fitato e oxalato e promoveu mudanças na biodisponibilidade de cálcio, ferro e zinco. Frente aos aspectos tecnológicos, observou-se que o uso de subprodutos interferiu na cor dos biscoitos, tornando-os levemente mais escuros e também enfraqueceu a rede de glúten formada, promovendo variações do diâmetro e fator de expansão. Por outro lado, observou-se que quanto maior a concentração de subprodutos, maiores foram os valores de dureza (textura), sendo as amostras consideradas mais firmes e crocantes. Do ponto de vista sensorial, verificou-se que o biscoito com 15% de subproduto de abacaxi foi o que demonstrou maior aceitação, seguido pelos cookies com 15% de subproduto de maçã, controle e 15% de subproduto de melão. Por meio de análise descritiva quantitativa (ADQ), observou-se que a adição de subprodutos de frutas alterou o perfil sensorial dos biscoitos. A partir dos resultados obtidos, concluiu-se que os subprodutos de frutas se apresentam como potenciais ingredientes para formulações de cookies, atribuindo-lhes propriedades físico-químicas, tecnológicas, nutricionais e sensoriais específicas as quais podem variar de acordo com o subproduto empregado.
45
Alexander, Jennifer Mary. "Optical properties of mineral dust aerosol including analysis of particle size, composition, and shape effects, and the impact of physical and chemical processing." Diss., University of Iowa, 2015. https://ir.uiowa.edu/etd/1819.
Abstract:
Atmospheric mineral dust has a large impact on the earth’s radiation balance and climate. The radiative effects of mineral dust depend on factors including, particle size, shape, and composition which can all be extremely complex. Mineral dust particles are typically irregular in shape and can include sharp edges, voids, and fine scale surface roughness. Particle shape can also depend on the type of mineral and can vary as a function of particle size. In addition, atmospheric mineral dust is a complex mixture of different minerals as well as other, possibly organic, components that have been mixed in while these particles are suspended in the atmosphere. Aerosol optical properties are investigated in this work, including studies of the effect of particle size, shape, and composition on the infrared (IR) extinction and visible scattering properties in order to achieve more accurate modeling methods.
Studies of particle shape effects on dust optical properties for single component mineral samples of silicate clay and diatomaceous earth are carried out here first. Experimental measurements are modeled using T-matrix theory in a uniform spheroid approximation. Previous efforts to simulate the measured optical properties of silicate clay, using models that assumed particle shape was independent of particle size, have achieved only limited success. However, a model which accounts for a correlation between particle size and shape for the silicate clays offers a large improvement over earlier modeling approaches. Diatomaceous earth is also studied as an example of a single component mineral dust aerosol with extreme particle shapes. A particle shape distribution, determined by fitting the experimental IR extinction data, used as a basis for modeling the visible light scattering properties. While the visible simulations show only modestly good agreement with the scattering data, the fits are generally better than those obtained using more commonly invoked particle shape distributions.
The next goal of this work is to investigate if modeling methods developed in the studies of single mineral components can be generalized to predict the optical properties of more authentic aerosol samples which are complex mixtures of different minerals. Samples of Saharan sand, Iowa loess, and Arizona road dust are used here as test cases. T-matrix based simulations of the authentic samples, using measured particle size distributions, empirical mineralogies, and a priori particle shape models for each mineral component are directly compared with the measured IR extinction spectra and visible scattering profiles. This modeling approach offers a significant improvement over more commonly applied models that ignore variations in particle shape with size or mineralogy and include only a moderate range of shape parameters.
Mineral dust samples processed with organic acids and humic material are also studied in order to explore how the optical properties of dust can change after being aged in the atmosphere. Processed samples include quartz mixed with humic material, and calcite reacted with acetic and oxalic acid. Clear differences in the light scattering properties are observed for all three processed mineral dust samples when compared to the unprocessed mineral dust or organic salt products. These interactions result in both internal and external mixtures depending on the sample. In addition, the presence of these organic materials can alter the mineral dust particle shape. Overall, however, these results demonstrate the need to account for the effects of atmospheric aging of mineral dust on aerosol optical properties.
Particle shape can also affect the aerodynamic properties of mineral dust aerosol. In order to account for these effects, the dynamic shape factor is used to give a measure of particle asphericity. Dynamic shape factors of quartz are measured by mass and mobility selecting particles and measuring their vacuum aerodynamic diameter. From this, dynamic shape factors in both the transition and vacuum regime can be derived. The measured dynamic shape factors of quartz agree quite well with the spheroidal shape distributions derived through studies of the optical properties.
46
Tammia, Rasmus. "Modeling and Control of Lime Addition in a Flotation Process." Thesis, Linköpings universitet, Reglerteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-139331.
Abstract:
Flotation is an important and versatile mineral processing technique that is used to separate hydrophobic materials from hydrophilic. This technique makes it possible to mine complex ores that otherwise would have been regarded as uneconomic and non-beneficial. In this case flotation is used to separate copper from the unwanted gangue. The addition of lime is used to control the pH level in the flotation’s pulp, which governs the selectivity of the process, i.e. which minerals are recovered. Currently, fluctuating concentration grades of the produced metals have been observed in Boliden Aitik. Therefore, Boliden proposes a new control strategy which aims to maintain a constant ratio between the added lime and the incoming ore flow, but at the same time ensuring that the pH level is maintained within allowed limits. The aim of this thesis is to develop a model that captures the most essential dynamics of a process stage where lime is added, and then evaluate the suggested control strategy by studying suitable control structures. A linear model describing the system dynamics in a specific operating region is obtained by conducting step response experiments on the process. The model is then used to obtain a model describing the disturbances of the process, thereby yielding a complete model that describes the most important dynamics. The most promising control structure utilizes the concept of selective control, where a ratio controller is allowed to maintain a constant ratio as long as the pH level is within allowed boundaries. The pH level is maintained within the boundaries with upper and lower bound pH controllers that utilize the concept of an equivalent control objective (known as the strong acid equivalent) in order to achieve satisfying pH control. The results show that the control structure is able to maintain a constant ratio, and also ensure that the pH level is kept within the allowed limits. A cascade inspired pH ratio controller is also studied and evaluated. The results show that this pH ratio controller is only able to maintain a constant ratio as long as the incoming ore flow is constant. However, the outcomes also suggest that the concentration grades are either sensitive to variations in the ratio between added reagent and incoming ore flow, or that there is something else that causes them to vary.
47
Guiral, Vega Juan Sebastian. "Textural and Mineralogical Characterization of Li-pegmatite Deposit: Using Microanalytical and Image Analysis to Link Micro and Macro Properties of Spodumene in Drill Cores. : Keliber Lithium Project, Finland." Thesis, Luleå tekniska universitet, Mineralteknik och metallurgi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70422.
Abstract:
Lithium represents one of the strategic elements for the rest of the 21st century due to its increasing demand in technological applications. Therefore, new efforts should be focused on the optimization of mineral characterization processes, which link the ore properties with its behaviour during downstream processes. These efforts should result in reducing operational risks and increasing resources utilization. The methodology presented in this study is based on the application of several classification techniques, aiming the mineral and textural characterization of two spodumene pegmatite deposits within the Keliber Lithium Project. Twelve textural classes have been proposed for the textual classification of the ore, which have been defined through the recognition of the main mineral features at macro- and micro-scale. The textural classification was performed through the application of drill core logging and scanning electron microscopy. Six classes are proposed to describe the characteristics of the spodumene ore. Six additional classes describe the main properties of the rocks surrounding the ore zone. Image analysis was implemented for the generation of mineral maps and the subsequent quantification of spodumene and Li2O within the analysed drill core images. The image segmentation process was executed in Fiji-ImageJ and is based on eight mineral classes and a set of seven feature extraction procedures. Thus, quantification of spodumene and Li2O is estimated by textural class. Hyperspectral images were used as a reference for assessing the estimations made through images analysis. A machine learning model in Weka allowed forecasting the behaviour of the twelve textural classes during spodumene flotation. This model is fed by metallurgical data from previous flotation tests and uses Random Forest classifier. The proposed methodology serves as an inexpensive but powerful approach for the complete textural characterization of the ore at Keliber Lithium Project. It provides information about: (1) mineral features at different scales, (2) spatial distribution of textures within the pegmatite body, (3) quantification of spodumene and Li2O within the drill cores and (4) processing response of each textural class. However, its application requires wide knowledge and expertise in the mineralogy of the studied deposits.Thesis Presentation.
Textural and Mineralogical Characterization of Li-pegmatite Deposit: Using Microanalytical and Image Analysis to Link Micro and Macro Properties of Spodumene in Drill Cores. Keliber Lithium Project, Finland.
48
Udoudo, Ofonime. "Modelling the efficiency of an automated sensor-based sorter." Thesis, University of Exeter, 2010. http://hdl.handle.net/10036/118786.
Abstract:
For future development of automated sensor-based sorting in the mining industry, an improvement in the separation efficiency of the equipment is desirable. This could be achieved through a better understanding of the identification and separation aspects of the automated sorter. For automated sorters that undertake separation through the use of compressed air jets, the problem of poor separation efficiency has been linked with co-deflection losses. Co-deflection losses occur as particles meant to pass on to the ‘accept’ bin are co-deflected with the particles (which are to be deflected) meant to go to the ‘reject’ bin. To study co-deflection losses and suggest means of improving automated sorter separation efficiency, this research investigates the effects of particle size, shape, throughput, together with the proportion of particles (out of the total test batch) required to be deflected on separation efficiency. The effect of the air valve configuration on separation efficiency was also studied. Presented also is a mathematical model which could be used to predict automated sorter separation efficiency. All separation efficiency investigations were undertaken using a TiTech Combisense© (BSM 063) automated sorter. Samples of granite were sized into -20+15mm, -15+10mm and -10+6mm size fractions and grouped into cubic and flaky shape fractions. These fractions were then divided into two with one portion painted for colour separation efficiency investigations. The separation efficiency results confirmed earlier research indicating that particle size and the fraction requiring deflection affects separation efficiency, with separation efficiency decreasing with a decrease in particle size and an increase in throughput. It was observed that co-deflection loss occurs when correctly identified ‘accept’ particles are co-deflected due to their close proximity to ‘reject’ particles that are to be deflected. Observations from the tests indicate that an increase in the proportion of particles requiring deflection increases the probability of finding ‘accept’ particles in close proximity to ‘reject’ particles leading to co-deflections. Monte Carlo simulations were used to produce a random distribution of particles on the conveyor belt as would be obtained from actual investigations. From these simulations particle proximity relationships and particle co-deflections were studied. Results indicate that the Monte Carlo simulations under-predicts particle proximity associations. The effect of shape on co-deflection was investigated with results indicating that flaky shaped particles produce higher number of co-deflections compared to cubic shaped particles. It was also observed that the valve sensitivity determined from valve opening and closing times is of importance to the selectivity (precision) of the separating air jets. A mathematical separation efficiency model is presented which contains two variables, the belt loading (calculated using particle size, shape and throughput) and the particle fraction of the total test batch that are to be deflected (% deflection). The separation efficiency can be calculated once these two variables are determined.
49
Andersson, Emil. "Online Metallurgical Mass Balance and Reconciliation." Thesis, Umeå universitet, Institutionen för fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-185252.
Abstract:
In mineral processing, one of the most important and versatile separation methods is flotation. Flotation utilizes the different surface properties of the valuable minerals in the ore to separate them from the less valuable gangue material in the ore. Crushed and ground ore is mixed with water and fed into flotation tanks. In the flotation tanks, the particles of valuable mineral are made hydrophobic. That way, they can be floated by attaching to air bubbles and gather on top of the flotation tank as froth. This froth, containing higher concentrations of valuable mineral, is recovered and then processed further. The flotation circuit is controlled and maintained using measurements on the mass flows and grades of different materials. Due to economical, practical, and technological limitations, these measurements are performed at a chosen number of points in the circuit and at discrete points in time. Poor measurement data can have devastating consequences if the operators are left with limited information and errors in the circuit remain undetected. The accuracy of the acquired measurements is improved by performing mass balance and reconciliation. Traditionally, mass balance uses the sum of the total mass flows and the average grades over long times to avoid including the internal mass of the circuit in the calculations. It is desirable to perform mass balance directly to allow for faster intervention if any failures occur in the circuit during the on-line process. This report describes an on-line dynamic approach towards mass balancing and reconciliation of the mass flows and grades in a flotation circuit. Here, physical models of the flotation circuit are used to construct mass balance constraints using interpolation and test functions and the mass balance problem is posed as an optimization problem. The optimization problem is to adjust the assay such that the residual, the difference between the measured and the adjusted assay, is minimized while maintaining mass balance. An implementation in MATLAB and tests on synthetic data show that the dynamic formulation of mass balance does adjust 'erroneous' measurements such that mass balance is fulfilled. Given this result, there are still important aspects of the implementation that have to be addressed. The model uses the unknown and cell specific parameters flotation rate and recovery. Thus, these must be found or properly modeled. This report proposes a possible model for flotation rate as well as a strategy to find the recovery. The requirements of accuracy and speed of the implementation are also discussed. Possible next steps of this project is to further confirm a time effective implementation using synthetic data. Consequently, the implementation can be adapted for natural data in order to verify correctness of models.I malmanrikning, är flotation en av de viktigaste och mest mångsidiga metoderna. Flotation utnyttjar de fysikaliska ytegenskaperna som partiklar av värdemineral har för att separera dessa från det mindre värdefulla gråberget i malmen. Krossad och mald malm blandas med vatten och matas in i flotationstankar. I flotationstankarna görs partiklarna av värdemineral hydrofobiska. På så vis kan de fästa sig vid luftbubblor och flyta till ytan och bilda ett skum. Detta skum samlas sedan ihop och behandlas vidare eftersom det innehåller en högre koncentration av värdemineral. Flotationskretsen styrs och underhålls med hjälp av mätningar av massflödena och halterna av de olika ämnena som finns i kretsen. På grund av ekonomiska, praktiska, och teknologiska hinder kan dessa mätningar bara göras på ett utvalt antal punkter i kretsen samt bara vid diskreta tillfällen. Felaktigt data kan ha förödande konsekvenser om operatörerna lämnas med begränsad information och processen fortlöper med oupptäckta fel. Mätsäkerheten kan förbättras med hjälp av massbalansering och haltjustering. Traditionellt görs massbalansering genom att summera den totala massan som löpt genom kretsen samt medelvärden av halterna över lång tid för att undvika att räkna in den interna massan i systemet. Det är önskvärt att utföra massbalansering direkt för att möjliggöra snabbare ingrepp ifall fel uppstår i kretsen under den fortlöpande processen. Denna rapport beskriver en dynamisk lösning för massbalansering och justering av massflöden och halter i en flotationskrets. Här används fysikaliska modeller av kretsen för att konstruera bivillkor för massbalans med hjälp utav interpolation och testfunktioner och massbalanseringsproblemet ställs upp som ett optimeringsproblem. Optimeringen sker genom att justera mätserien så att residualen, skillnaden mellan det uppmätta värdet och det justerade värdet, minimeras under uppfyllande av mass balans. En implementation i MATLAB och tester på syntetisk data visar att den dynamiska formuleringen av massbalans justerar de felaktiga mätvärdena så att massbalans uppfylls. Med det resultatet i åtanke, finns det fortfarande viktiga aspekter av implementationen som bör tas hänsyn till. Modellen använder de okända och cellspecifika parametrarna flotationshastighet och utbytet och dessa måste kunna bestämmas för att denna modell ska kunna användas. Ett förslag på modellering av flotationshastigheten föreslås i rapporten. Dessutom ges förslag på strategier att hitta utbytet. Kraven på noggrannhet och snabbhet diskuteras också. Möjliga nästa steg för projektet är att vidareutveckla en tidseffektiv implementation genom att använda syntetiska data. Därefter kan en implementation för naturligt data verifiera modellerna.
50
Hill, David T. "Removal of trace elements from coal using a multiple-property processing circuit." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-01242009-063125/.