Дисертації з теми "Froth flotation"
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1
Hanumanth, G. S. "Froth flotation of china clay." Thesis, Swansea University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637217.
Анотація:
An experimental and theoretical study of froth flotation separation of kaolinite from other associated minerals of china clay is presented herein. A new laboratory flotation equipment has been designed and built for the above study. Its novel features are discussed. Effects of physico-chemical variables such as pH, initial solid concentration of feed, froth height and air flowrate are studied by systematically carrying out series of semi-batch kinetic experiments. pH is shown to influence both recovery and grade of the product. The effects of pH are interpreted in terms of particle/particle interactions leading to flocculation which is demonstrated to be an essential prerequisite for flotation of small particles approaching colloidal size range with the typically 1-2mm bubbles produced in the cell. Regions in a flotation cell where hydrodynamic conditions permit flocculation are identified by an analysis of pulp flow based on a distributed shear rate model. The effects of initial solid concentration on recovery and grade are interpreted in terms of floc/bubble collision frequency. Influence of floc breakup and solid drainage on pulp phase and recovery kinetics, and product grade is discussed. Pulp phase kinetics are analysed on the basis of rate-distributed species model. The selective nature of froth drainage is demonstrated by a series of kinetic experiments using different froth heights. Air flowrate can influence both pulp phase kinetics and froth drainage. These effects are studied independently by conducting two sets of experiments - one with a negligible depth of froth and the other with a deep froth. An analysis of flow and rupture forces in the froth leads to identification of two distinct zones where different floc breakup and drainage mechanisms exist. On this basis a three-phase model, consisting of a mixed pulp phase and two mixed froth phases, is developed and used to predict froth effects on flotation kinetics and selectivity.
2
Kaya, Muammer. "Froth washing in mechanical flotation cells." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74232.
Анотація:
This basic research project was aimed at assessing the potential of wash water for mechanical flotation machines. Test work at laboratory scale first examined the nature of entrainment; froth structures with and without wash water; and the location, geometry, and flowrate of wash water addition. The relationship between slurry, total water recovery and gangue recovery was characterized. Confirmatory work at pilot plant was completed.The effect of wash water on metallurgical performance was tested with various streams from the Falconbridge Strathcona mill at laboratory and pilot and full plant scale, and with the secondary cleaner stage at the Eastmaque Kirkland Lake mill.
Results show that mechanical entrainment is the major means of gangue transport up to the slurry-froth interface. Transport into the froth is mostly hydraulic, although entrapment becomes dominant at low water recoveries. Free gangue recovery was closely related to slurry water recovery at all three scales. Wash water at an optimum superficial rate of 0.03 to 0.07 cm/s reduced entrainment by anywhere from 30 to 70%, typical values being around 50%.
Wash water can be further assisted by mechanical and ultrasonic vibration of the froth, difficult to achieve at plant scale, or with warm wash water, which becomes attractive if a waste heat source is available. A further rejection of 10 to 20% then becomes possible.
Distributor geometry was aimed at washing the entire froth surface at laboratory and pilot scale. It was observed that the recovery of hydrophobic minerals generally increased because the froth was stabilized. At plant scale, two perforated pipes close to the concentrate weir yielded the most reject. Froth stabilization was lost, and recoveries decreased.
3
Kelley, Kyle. "Model-based Computer Simulation of Froth Flotation." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76850.
Анотація:
Froth flotation is a separation process by which particles are selectively attached to air bubbles. It is one of the most dynamically complex industrial processes in use today. This complexity has steered research towards understanding the fundamental principles of the process. Relatively few researchers have successfully attempted to create a flotation simulator based on first principles. This thesis presents the development and testing of a simulator called SimuFloat, which is based on the flotation model developed at Virginia Tech. Flotation of chalcopyrite, coal, and phosphate are simulated. These simulations show the effects of changing the input parameters of the flotation circuit. The accuracy of SimuFloat is validated by comparing the predictions with the experimentally obtained flotation results.Master of Science
4
Henwood, Daryl. "The effect of conditioning on froth flotation." Master's thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/21416.
Анотація:
Bibliography: pages 154-159.The method and extent to which mineral slurries are conditioned have been shown to greatly affect flotation grades and recovery. Most of this work is very mineral specific and centres around one or two operating variables. One of the major obstacles to understanding the effects of such pretreatment more fully, and to developing a global understanding of conditioning, is the system specific nature of the procedures applied to each mineral, and the apparently conflicting results across a range of mineral types. This thesis sets out to define conditioning both broadly enough to encompass almost all aspects of conditioning, as well as specifically enough to be useful in the study of single mineral-collector systems. Having done this, a measure of the efficiency or effectiveness of conditioning is devised and used to evaluate the relative effects of variables of conditioning, as well as to gain some insight into the mechanisms affecting the results. The work is completed by relating these observations to expected results in industrial applications and their implications on plant procedures. Most forms of conditioning for flotation were found to fit into two basic categories, which if they both take place in the same process, follow one another sequentially. In this thesis, these were termed "primary" and "secondary" conditioning, and were defined as follows: Primary Conditioning relates to the physical preparation of the surface of the particles, including comminution, oxidation, acid leaching and bacterial pretreatment. Secondary Conditioning is the process whereby prepared particles are rendered hydrophobic or hydrophilic through mixing, control of the environment and contacting with reagents.
5
Zhang, Jian-Gou. "Factors affecting the kinetics of froth flotation." Thesis, University of Leeds, 1989. http://etheses.whiterose.ac.uk/3305/.
Анотація:
In this research work, three types of flotation models (discrete, mean rate and the gamma function models) are modified based on the relationship between mass recovery and recovery. The modified models can be used to calculate both the recovery and grade of concentrate. Experimental work was carried out by using three different samples, which are chalcopyrite, coal and complex sulphide. In the chalcopyrite and coal flotation, air flow rate (AFR) was varied and different size fractions were considered in coal flotation. In complex sulphide flotation, the impeller speed (IPS) and air flow rate were varied, different size fractions were also considered individually. From the experimental results, the effect of air flow rate, impeller speed and particle size on the recovery and grade of concentrate are obtained, it is shown that an increase in air flow rate does not significantly increase recovery but reduce the grade of concentrate. High impeller speed can increase the recovery of fine and medium size, but it has very little effect on the coarse size. The effect of particle is that the medium size has the highest recovery in Fe minerals but the fine has the highest recovery in Zn and Cu minerals. The air flow rate, impeller speed and particle size affect on the kinetics of flotation is discussed from the model results. Where the modified models are used, the results show that an increase in air flow rate will increase the flotation rate of all size fraction, but an increase in impeller speed can only increase the flotation rate of the fine and medium size. The medium size has the highest flotation rate in most of the case.
6
Riaz, Muhammad. "An electrochemical investigation of synergism in froth flotation." Thesis, Brunel University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257547.
7
Shumba, Tanaka Casandra. "Relationship between flotation operational factors and froth behaviour." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/9127.
Анотація:
Includes bibliographical references.This study utilised laboratory-scale column flotation experiments to investigate froth stability, with respect to, water recovery and top-of-froth bubble burst rate. Tests were conducted at different froth heights, superficial air rates and depressant dosages in a 2 m high Plexiglass column, using a PGM bearing UG2 ore from the Bushveld Igneous Complex. Four concentrate and tailings samples were simultaneously collected and solids and water recoveries were determined. Assays of the concentrates were conducted to establish the amount of platinum, palladium and chromite that was recovered under each operating condition. Video footage of the top of the froth was recorded and was used to measure the top-of-froth bubble burst rate. The stability of the froth was analysed qualitatively by comparing the relationship between water recovery and the bubble burst rate at the different operating conditions. A key finding from this study was that the concentration of particles had a large effect on the stability of the froth. The maximum concentration of particles was obtained when the tests were conducted in the absence of depressant. Under these conditions it was established that the froth produced was so stable that increasing the air rate only showed minor changes in the stability of the froth phase. This stability has been attributed to the presence of hydrophobic gangue, which stabilised the froth phase by embedding between adjacent bubbles and preventing bubble coalescence. Conversely, when a high depressant dosage was used the froth became unstable such that no trends could be established when either air rate or froth height were altered. The instability of the froth has been attributed to the depression of the majority of the froth stabilising gangue, which resulted in increased bubble coalescence.
8
Kaushik, Sarthak. "Surface properties of crandallite in relation to froth flotation." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42550.
Анотація:
The surface properties of crandallite relevant to the anionic flotation of salt-type minerals were investigated through electrokinetic, turbidity, and wettability techniques. All the tests were performed on fine crandallite particles as a function of pH and reagent concentration. The selected reagents included starch and oleic acid.
From the zeta potential measurements, the iso-electric point of crandallite was found to be at pH 5.5 and the mineral surface can be expected to be negatively charged under typical flotation conditions (pH 9-11). The value of the iso-electric point correlated well with the stability of crandallite particles towards aggregation. Suspensions of fine crandallite showed minimum turbidity at pH 5.5 suggesting that the aggregation of the mineral was most pronounced at the iso-electric point. Calcium ions behaved as potential determining ions by increasing the iso-electric point to pH 6.5. In addition, calcium ions also acted as specifically adsorbing ions at higher pH.
In the presence of starch, crandallite particles were strongly flocculated producing supernatants with the clarity of tap water. At the same time, the effect of starch on the zeta potential of crandallite was rather weak, consistent with the non-ionic character of the polysaccharide. The stability of crandallite towards aggregation was not strongly affected by oleic acid suggesting that the surfactant did not interact with the mineral. Wettability measurements on crandallite particles showed that oleic acid did not render the mineral particles hydrophobic at pH 10.5 (under normal flotation conditions) or at pH 7, which was in strong contrast to the wettability response of apatite. Under these conditions, crandallite surface was negatively charged and the adsorption of the anionic surfactant seemed to involve physical electrostatic forces as opposed to chemical interactions known to occur between apatite and oleic acid.
Overall, the experimental results strongly suggest that crandallite remains hydrophilic during apatite flotation at pH 10.5 and the main mechanism of contamination of apatite concentrates by crandallite is through mechanical entrainment in the froth rather than by true flotation. In this respect, the role of starch as a flocculant should be beneficial in reducing the amount of fine crandallite reporting to the apatite concentrate.
9
Noble, Christopher Aaron. "Laboratory-Scale Analysis of Energy-Efficient Froth Flotation Rotor Design." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/76881.
Анотація:
Froth Flotation is an industrial separation process commonly used in the primary enrichment of run-of-mine mineral material. Over the past 100 years, much of the process's development has come from empirical evolution, rather than fundamental understanding. While many of the governing sub-processes are still poorly understood, the primary influential factors lie within the chemical, equipment, and operational variables unique to each flotation system. This investigation focuses on the phenomenological investigation of the equipment variables, particularly the rotor design, at the laboratory scale.
During this study, several small-scale flotation systems were developed, including various rotor and stator designs, tank sizes, and flow conditions. Experimental techniques were also developed to identify operational performance in four criteria: power consumption, gas dispersion, operational robustness, and flotation kinetics. Evaluation of the various rotors was conducted in two campaigns: (1) an exploratory campaign which featured 14 rotors in limited operational conditions (2) a detailed campaign which featured three rotors in an exhaustive set of conditions.
The results show that different rotors exhibited varying degrees of performance when judged by the aforementioned performance criteria. In general, excessive fluid pumping leads to an increase range of stable operation at the expense of greater power consumption. However, this increased power consumption does not necessarily correspond to increased flotation performance, as the data generally confirms the linearly proportional relationship of flotation rate and bubble surface area flux. Consequently, enhanced flotation kinetics can be achieved by rotors which disperse high rates of gas while retaining a small bubble size.Master of Science
10
Ramberg, J. (Juhani). "Effect of the reagents and minerals on froth electrical conductivity in pilot scale froth flotation process." Master's thesis, University of Oulu, 2016. http://urn.fi/URN:NBN:fi:oulu-201601131001.
Анотація:
This thesis studies how the changes to the flotation process caused by adjusting pH and the dosage of the flotation reagents affect the electrical conductivity of the froth flotation froth in different parts of the froth. The measurements in the experimental part were done in Oulu Mining School’s continuous minipilot beneficiation plant at the University of Oulu in March and May of 2015. The conductivity of the froth was measured with Outotec’s ERT (Electrical Resistance Tomography) based test probe. The probe was placed inside the 4-litre flotation cell that acted as a rougher in copper refining circuit. Froth’s bubble size, colour, stability and speed were measured with Outotec’s FrothSenseTM -camera. Elemental composition of the process streams was measured with a method based on x-ray fluorescence. The effect of three chemical reagents used in froth flotation, and also the effect of pH, was studied: dosage of Dowfroth (Test 1), xanthate (Test 2), zinc sulphate (Test 3) and pH (Test 4). Each test consists of three step tests, where the value of variable in question was changed while other values were kept at their base levels. Each test was performed twice. Assumption was that the adjusting of mentioned variables affects the other process variables, such as bubble size, froth thickness, elemental compositions etc., which in turn affects the electrical conductivity of the froth. Froth was divided vertically into layers so that the possible differences in different parts of the froth could be observed. Theoretical part of this thesis presents an overview of beneficiation process chain, starting from grinding and ending in dewatering processes. The chemical reagents used in flotation and some basic methods for measuring different parameters are also introduced. The results from the experimental part showed that the changing dosage of chemical regents and pH causes changes in process which also affected the electrical conductivity of the froth. Especially bubble size and froth thickness had clearly an effect on the conductivity. Furthermore, the conductivity values and changes to them were different in different layers of the froth, when the froth was thick. In a thin froth, the differences in the conductivity values and changes in them between the froth layers were much smallerTässä diplomityössä tutkittiin miten pH:n ja vaahdotusrikastuksessa käytettävien kemikaalien annostuksien säätämisen prosessiin aiheuttamat muutokset vaikuttavat vaahtopatjan eri osien sähkönjohtavuuteen vaahdotusrikastus prosessissa. Kokeellisessa osiossa mittaukset tehtiin Oulu Mining School:in jatkuvatoimisella minipilot -rikastamolla Oulun Yliopistolla maalis- ja toukokuussa 2015. Vaahdon sähkönjohtavuutta mitattiin Outotecin ERT:n (Electrical Resistance Tomography) perustuvalla testisauvalla. Sauva oli asennettu tilavuudeltaan nelilitraiseen vaahdotuskennoon, joka toimi kuparin rikastuspiirissä esivaahdotuskennona. Vaahdon kuplakokoa, väriä, stabiilisuutta ja nopeutta mitattiin Outotecin FrothSenseTM -kameralla. Prosessivirtojen kemialliset koostumukset mitattiin röntgenfluoresenssiin perustuvalla menetelmällä. Työssä selvitettiin kolmen eri vaahdotuksessa käytettävän kemikaalin ja pH:n vaikutusta vaahtopatjan sähkönjohtavuuteen: Dowfrothin (Testi 1), ksantaatin (Testi 2) ja sinkkisulfaatin (Testi 3) annostuksien sekä pH:n (Testi 4) vaikutus. Jokainen testi koostui kolmesta askelkokeesta, jossa mainitun muuttujan arvoa muutettiin muiden muuttujien arvojen pysyessä vakioina. Jokainen testi toistettiin kahdesti. Ennakko-oletus oli, että muutokset pH:hon ja reagenssien annostuksiin aiheuttavat muutoksia prosessinparametreihin kuten kuplakokoon, vaahdon paksuuteen, kemiallisiin koostumuksiin jne., jotka puolestaan vaikuttavat vaahdon sähkönjohtavuuteen. Vaahto jaettiin korkeussuunnassa kerroksiin, jotta mahdollisia eroja sähkönjohtavuuksien arvoissa ja niiden muutoksissa eri vaahdon osien välillä pystyttiin tarkastelemaan. Työn teoriaosuudessa esitellään mineraalien rikastuksen prosessiketju, alkaen jauhatuksesta ja päättyen vedenpoistoprosesseihin. Työssä käydään läpi myös vaahdotusrikastuksessa käytettäviä kemikaaleja sekä eri parametrien mittauksessa käytettäviä mittausmenetelmiä. Kokeellisesta osiosta saadut tulokset osoittavat, että pH:lla sekä vaahdotuksessa käytettävien kemikaalien annostuksien muutoksilla on vaikutusta vaahtopatjan sähkönjohtavuuteen. Erityisesti kuplakoolla ja vaahdon paksuudella oli selkeästi vaikutusta vaahdon sähkönjohtavuuteen. Lisäksi huomattiin, että paksussa vaahdossa sähkönjohtavuuden arvot ja niiden muutokset olivat erilaisia vaahdon eri kerroksissa. Ohuessa vaahdossa erot sähkönjohtavuuksien arvoissa ja muutoksissa vaahtokerrosten välillä olivat huomattavasti pienempiä
11
Vera, Marco A. "A touch of froth : how bubble-particle aggregates take the strain; an investigation into aspects of froth zone recovery in mineral flotation /." St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16112.pdf.
12
Maree, Westhein Bethren. "Froth flotation of an Nkomati mineral ore using mixtures of thiol collectors." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2512.
Анотація:
Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.Nickel, a valuable base metal, is the predominant product from the Nkomati mine in South Africa. High-grade nickel mineral ores (2%) from the Massive Sulphide Body have been depleted leaving those of low grade (0.3%). The beneficiation of this ore presents a challenge to the minerals processing industry. In response, batch froth flotation tests were used to explore the effects of mixtures of potassium amyl xanthate (PAX) and IPETC (Isopropyl ethyl thionocarbamate) on the grades and recoveries of nickel. In the mixtures, the xanthate accounted for 95.5, 90, 85 and 80 mole% respectively. Generally an increase in the nickel grade and recovery was observed with the mixtures relative to PAX. IPETC gave a significant increase in the cumulative water recovery with a significant decrease in cumulative nickel grade relative to PAX. PAX gave the highest cumulative nickel grade for the singular collector tests (1.9%), while obtaining the lowest cumulative recovery (77%). Out of the collector mixtures, mixtures 85% PAX: 15% IPETC and 90% PAX: 10% IPETC produced the joint highest cumulative grades (1.8%). These mixtures both gave recoveries of 82%. Collector mixture 95.5% PAX: 4.5% IPETC gave the second highest grade (1.7%) and the highest nickel recovery (85%). Although there were differences in the cumulative nickel grades and recoveries there were statistically no significant improvements observed with the use of the mixtures of PAX and IPETC in comparison to the industry mixture (95.5% SIBX: 4.5% IPETC). Tests were performed using the three best performing collector mixtures at molar dosages of 1.3, 0.65 and 0.325mmol/t. The highest cumulative nickel grades were obtained at the lowest collector dosages (at a molar dosage of 0.325mmol/t of 95.5% SIBX: 4.5% IPETC) with collector mixture 95.5% PAX: 4.5% IPETC being the most selective with a nickel grade of 2%. It was also observed that an increase in collector dosage, generally increased the cumulative nickel recovery with collector mixture 95.5% PAX: 4.5% IPETC at a molar dosage of 1.3mmol/t gave the highest cumulative recovery out of the tested mixtures (85%). The study also indicated that an increase in selectivity (i.e. cumulative grade) was at the expense of cumulative recovery. With a decrease in dosage, there was no significant improvement in the cumulative nickel grade and recovery for the tested mixtures compared to the industry mixture. There was however a significant decrease in the water recoveries achieved with PAX and collector mixtures 95.5% PAX: 4.5% IPETC at a molar dosage of 1.3mmolg/t of as well as mixture 90% PAX: 10% IPETC at a molar dosage of 0.65mmol/t.
13
Knapp, Jennifer Mary Smith. "A study of floatation froth behavior." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/41996.
Анотація:
In order to develop a better understanding of the role of the froth phase in coal flotation, froth stability measurements have been conducted using a continuous flotation cell. The results indicate that the mass flow rate of coal or mineral matter reporting to the product is linearly related to the flow rate of water reporting to the product. This relationship has been used to distinguish the relative contributions of hydrophobic attachment or hydraulic entrainment to the total product recovery. Simple mathematical expressions have also been developed to characterize the cleanability of various coals.
A mathematical model based on first principles has been developed to provide additional insight into the complex relationship between the various operating parameters of a flotation cell and the froth behavior. The predicted results compare favorably to actual flotation test data for most conditions. In addition, a simple method was developed to study the fundamental interactions of various frothing agents with coal particles. The results of these studies indicate that the adsorption behavior of frothers in the presence of coal depends on both the physical properties of the frothing agent and the coal.
Master of Science
14
Wright, Benedict Anson. "The Development of a vision-based flotation froth analysis system." Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/9899.
Анотація:
Bibliography : leaves157-163.This dissertation describes the development of a machine vision system for the on-line analysis of flotation froth images. The size and shape of bubbles that constitute the flotation froth convey considerable information on the performance of the flotation process. A method whereby this size and shape information can be automatically extracted from froth images is highly desirable. In this research, a system was developed which acquires froth image using a video camera, and then rapidly identifies the bubbles in the froth by segmenting the image using a morphological operation known as the Fast Watershed Transform. Bubble size and shape information is extracted from the segmented images and can be correlated with metallurgical and other data from concentrator plants in order to elucidate relationships between froth appearance and plant performance. The machine vision system developed was tested on a platinum concentrator plant, and is able to identify and characterise variations in flotation froth appearance, which occur in response to changes in process inputs. The ability of the system to detect changes in bubble size distribution has been found to be particularly useful in detecting process input variations.
15
Zhang, Jian. "Prediction and Influence of Mineral Liberation on Froth Flotation Performance." Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/68364.
Анотація:
Liberation of valuable mineral is essential for its effective separation from gangue. Prediction of liberation requires quantification of texture of the rock and structure of the progeny particles in terms of probability functions. In this work, predictive liberation models have been developed by measuring these functions from SEM images using Labview™ software. A transformation matrix model that explicitly incorporates mineral liberation has also been developed to quantify the influence of mineral liberation on flotation performance.
16
McKeon, Timothy Josiah. "An In-Plant Evaluation of Froth Washing on Conventional Flotation Cells for Coal." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/35708.
Анотація:
Column flotation cells have become increasingly popular in the coal industry due to their ability to improve flotation selectivity. The improvement can be largely attributed to the use of froth washing, which minimizes the nonselective entrainment of ultrafine minerals matter into the froth product. Unfortunately, the practice of adding wash water in conventional flotation machines has been largely unsuccessful in industrial trials. In order to better understand the causes of these failures, a detailed in-plant test program was undertaken to evaluate the use of froth washing at an operating coal preparation plant. The tests included detailed circuit audits (solid and liquid mass balances), salt tracer studies, and release analyses. The data collected from these tests have been used to develop criteria that describe when and how froth washing may be successfully applied in industrial flotation circuits.
A second series of tests was developed to look at other alternatives to froth washing and their effectiveness. This involved two-staged flotation circuitry. A two-staged approach was developed because the existing flotation cells did not have enough residence time to support froth washing. The process owner wanted to evaluate possible alternatives to column cell flotation. The testing included release analysis testing as well as a detailed series of tests with percent solids control to the secondary flotation unit.Master of Science
17
Ramagwede, Mudzimba Hubert. "The sulphidization of mineral surfaces as applied to the froth flotation process." Thesis, Rhodes University, 1988. http://hdl.handle.net/10962/d1004590.
Анотація:
This work constitutes a fundamental study of the interaction between soluble sulphide,copper (II) oxide and cerussite particles in the presence of Ca²⁺ ,Mg²⁺ starch , gum arabic and Triton X- IOO . A detailed investigation of the effect of pH of the system on the rate of sulphide uptake was made . In addition , the structural form of the surface precipitat.es were determined with the aid of scanning electron microscopy . On the basis of these results , it was concluded that adsorption of sulphide on cerussite in the presence or absence of Ca²⁺ starch, gum arabic and Triton X-IOO could either lead to the formation of a non-uniform or a uniform sulphide layer depending on the experimental conditions . However , the interaction of copper (II) · oxide wi th soluble sulphide in the presence or absence of the above mentioned species always led to the formation or a non-uniform sulphide layer . Preliminary experiments of the interaction between xanthate and sulphidized surface showed that oxide surface covered with metal sulphide layer reacts with less xanthate than the free oxide surface.
18
Stallard, Michael L. "Precombustion desulfurization of coal by photochemical methods and pyrite depression in froth flotation." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-07132007-143147/.
19
May, Frank [Verfasser]. "Froth flotation improvement by plasma pretreatment of sulfide minerals / Frank May." Greifswald : Universitätsbibliothek Greifswald, 2014. http://d-nb.info/1053953003/34.
20
O'Connell, Barrie Christopher. "Selective wetting and separation of PET and PVC by froth flotation." Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269663.
21
Morrison, Angus James. "Tank design modifications for the improved performance of froth flotation equipment." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/61631.
Анотація:
Froth flotation is a physico-chemical technique used to separate the constituents of a mixed mineral slurry by their relative surface hydrophobicity. In order to do so economically, it is necessary to treat large volumes of material in ever-larger and more efficient tanks. The efficiency and efficacy of such tanks can be enhanced through mechanical modifications designed to improve froth handling, increase the likelihood of bubble-particle interactions in the pulp, and increase the residence time of suspended solids in the tank. However, design modifications suggested by computational modelling or bench-scale experiments often do not realise performance improvements at pilot and plant-scale because of imperfect scale-up from bench-scale, and differences in the type and intensity of the sub-processes affecting performance at different scales. The first outcome of this thesis is an intermediate, laboratory-scale froth flotation circuit that more closely resembles continuously-operated pilot-scale equipment, but which is better instrumented and controlled. This work describes not only the laboratory-scale system, but also detailed regression models of its behaviour and performance based on extensive monitoring and instrumentation. The resultant performance models provide a baseline against which to test design modifications, and the resultant behaviour models inform the design of such modifications. The second outcome of this thesis, a performance-enhancing design modification, was prompted by the discovery that minimising the variability of the pulp-froth interface leads to an increase in both indicative grade and recovery. The resultant tank modification was a horizontal mesh inserted into the pulp below the pulp-froth interface, designed to isolate it from the turbulent region around the impeller. The mesh pore size and thickness, and the position at which it was installed in the tank, were taken as design variables to be optimised by the genetic algorithm method. The result is a grade-recovery curve corresponding to an optimal mesh pore size of 123.4 +/- 3.1 mm. From this curve it was found that increasing the mesh thickness from 33 mm to 47 mm yields a maximum improvement in the recovery of 18.9% without compromising the grade, and increasing the depth of the mesh from 200 mm to 250 mm below the pulp-froth interface yields a maximum improvement in the grade of 3.2% without compromising the recovery. This grade-recovery curve, and the insights gained during the process of design and refinement, provides the rationale for a proposed program of mesh tests at pilot-scale.
22
Sadr-Kazemi, Naheed. "Estimation of coal flotation performance and froth properties using image processing." Thesis, University of Manchester, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.682189.
Анотація:
Reagent concentration is an important factor in froth flotation. It is also known that the froth structure plays an important role in the flotation separation achieved. The effect of surfactant concentration, conditioning time, pH and adsorption of a single reagent on froth structure and flotation performance was studied in a HaIIimond tube (micro scale) and Denver cell (macro scale). The surfactant concentration was found to be important factors in determining froth structure and stability. The appearance of the upper bubble surface of flotation froths is used qualitatively as a basis for control in industrial flotation cells. A quantitative image-processing algorithm was developed for froth surface bubble size distribution measurement that is largely insensitive to factors such as froth type, lighting conditions and bubble size. This was used to estimate the flux of bubble surface area overflowing the weir. A quantitative kinetic model based on the flux of loaded bubble surface overflowing the concentrate weir in a free-flowing froth is described. The froth is divided into two distinct phases; the bubble shells, which contain hydrophobic solids selectively, attached, and the inter-bubble lamellae, which contain non-selectively entrained solids. Quantitative relationships between the froth structure and flotation performance were determined. It was found that the froth flux relationships did not scale-up directly from micro to macro scale. A sampling technique was developed for measuring the bubble shell solids loading, which allowed the lamella thickness and solids concentration to be estimated. Based on adsorption studies and froth structure, using various reagent addition strategies was investigated to enhance the flotation performance by altering the froth structure. It was found that the flotation performance could be improved by continuous reagent addition during flotation.
23
Uusi-Hallila, S. (Senni). "Utilizing froth phase behaviour and machine vision to indicate flotation performance." Master's thesis, University of Oulu, 2014. http://urn.fi/URN:NBN:fi:oulu-201404161276.
Анотація:
Flotation is one of the most well-known mineral separation methods. In flotation process hydrophobicity of the solids is manipulated in order to separate the valuable minerals from the gangue. It is highly complex process because many simultaneous sub-processes and interactions occur within the system. It is essential to have a good understanding and representation of the flotation phenomena in order to design control strategies.
Modern physical froth stability measures have an intrusive nature and therefore they are not practical to provide a continuous online froth stability measurement. Unlike these measures, machine vision is able to measure the key aspects of the froth owing to its non-intrusive nature. Several physical, statistical and dynamical features of froth surface are possible to measure with the machine vision techniques.
The objective of this work was to understand the froth phase behavior better which indicates the flotation performance. Literature review of flotation and measurements used in flotation were performed. Image analysis methods were listed and, regarding to the importance of the froth stability, dynamical features of the froth image analysis were investigated more closely. A primary batch flotation test-work was carried out in University of Oulu. The main batch flotation experiments were executed in University of Cape Town with the wide range of operating conditions. Video captures were analyzed with statistical methods and dependencies between FrothSense™ data and concentration data were discovered. Furthermore, PLS model was formed from FrothSense™ data and process measurements in order to predict water recovery, copper grade and copper recovery.
Online measurements obtained from FrothSense™ with wide range of operating conditions can be used for soft sensors. Soft sensors can estimate the stability of the froth with the robust predictions.
24
Sheni, Nanji Ruth. "Considering the effect of pulp chemistry during flotation on froth stability." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22940.
Анотація:
On an industrial scale the need for improved flotation performance is of high importance in the current economic climate. Studies have shown that the pulp phase chemistry has a strong effect on the froth phase and therefore it is necessary to investigate how the manipulation of pulp chemistry factors can improve flotation performance. Research into the manipulation of this chemistry is well underway and factors including the pulp potential (Eh), pH, dissolved oxygen (DO) and ionic strength (IS) govern the pulp chemistry. This study aims to investigate how the manipulation of these factors affects the froth stability, bubble size and entrainment of the froth phase through Platinum Group Metal (PGM) flotation. In this study the Eh, pH, DO and IS were successfully manipulated to investigate their effects on froth stability and water recovery in 2-phase, as well as their effect on water and solids recovery, entrainment and the grades and recoveries of valuable minerals (copper, nickel, platinum and palladium) in 3-phase in the absence and presence of depressant at high dosages; 500 g/t Carboxymethyl Cellulose (CMC). Stability column tests were used to determine froth stability as a function of the dynamic stability factor (Barbian et al., 2005) and batch flotation tests were used to obtain the total water and solids recovered, the grades and recoveries of the valuable minerals as well as to determine entrainment. Further tests were performed to investigate the effect of changing the pH on the Eh in a 3-phase system in which all the other pulp factors were kept constant. The effect of changing the pulp factors on the froth bubble size was investigated by capturing side view images of the froth obtained in a batch flotation cell as each pulp factor was changed. This study has shown that careful control of the pulp chemistry, namely increasing IS, increasing pH, decreasing DO and decreasing Eh, resulted in improved froth stability. The Eh was found to be inversely proportional to the pH. This study has further shown that increased water recoveries and reduced bubble size in the froth were observed at 5 IS as compared to 1 IS due to the froth stabilising nature of the pulp at 5 IS. Operating at high Eh (500-730 mV) was observed to be detrimental to valuable mineral grades and recoveries and promotes entrainment. This kind of knowledge contribution may be key in improving flotation performance and increasing the grades and recoveries of valuable minerals obtained in South Africa's PGM mining industry.
25
Fickling, Ronald Sidney. "An investigation into the froth flotation of four South African coals." Master's thesis, University of Cape Town, 1985. http://hdl.handle.net/11427/22398.
Анотація:
Bibliography: pages 130-136.Froth flotation is used extensively throughout the world to beneficiate fine (-0,5 mm) coal. However when the same technology is applied to the majority of South African coals it has proved relatively unsuccessful. As the beginning of an ongoing research program, this thesis examines the effects of basic flotation parameters on the beneficiation by flotation, of four South African coals, to identify research areas where a more in-depth investigation is needed. An important conclusion is that South African coals are floatable, and flotation selectivity can be obtained, provided process parameters are controlled within a narrow range. A more in-depth study of the liberation characteristics of the coal and gangue and of the individual macerals is needed because only this will limit the final result. Finally, more research is needed to identify chemicals which exhibit a high degree of specific adsorption on the individual coal components, so that ultimately maceral selectivity can be achieved.
26
Hatfield, Douglas. "The implications of froth structure and surface appearance for flotation performance." Doctoral thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/5321.
Анотація:
Includes bibliographical references (p. 166-170).In this work, the flotation step of mineral extraction has been investigated to determine the mechanisms through which input variables impact on flotation separation efficiency and, in particular, the froth zone in flotation. The novel contribution of the work is in terms of demonstrating the importance of solids in governing the froth stability and hence the froth structure. Further, it has been propsed that the two most important factors that determine the impact of the solids on the froth are the degree of particle coverage on the bubble surface and the particle hydrophobicity. The mechanism through which the solids affect the froth stability has been demonstrated through experimental observations of flotation metullurgical performance, measurement of the froth surface appearance using machine vision and froth modelling. The insight obtained through understanding of the influence of solids on the froth zone will yield improved design and operation of industrial flotation circuits.
27
Hassan, Ghanim. "Minimizing bacterial biofilm in water using froth flotation and shock chlorination." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/9723/.
Анотація:
Microorganisms in potable water systems are either present in the planktonic “floating stage”, or attached to surfaces, usually as biofilm. Many hygienic and economic problems are attributed to this phenomenon. Through the last seven or so decades many trials were made to overcome biofilm problems. Unfortunately, biofilm prevention stills a premature field of science. Therefore, serious solutions with new horizons are needed. The objective of this study is to provide a water distribution system which is free of microorganisms, both in the planktonic and biofilm stages, and biocides. The two components are interactive; biofilm formation is stimulated by the presence of low (residual) levels of biocides whereas removing the bacteria results in less or no biocide being needed. The first part of the research investigates the use of chemical free froth flotation to remove microorganisms. Bacteria are hydrophobic and thus should be able to be separated by froths. A method for producing froth without using chemicals has been developed to avoid water quality deterioration and this froth is shown to hold bacteria without the need for biocide treatment or frothing chemicals. Experiments were undertaken to explore how far this process can purify a water stream. The froths formed were found to hold up to 2×108 cfu ml-1 of bacteria without chemical collectors, and made a cfu/ml drop of 55% between the inlet and outlet streams. The second area of research investigated shock chlorination and dechlorination to kill the microorganisms but almost immediately remove the biocide. Among all the dechlorination techniques, aeration was found to be the most suitable method. Investigations were undertaken to determine how fast and how practically acceptable the method of dechlorination by aeration is. Dechlorination design demand was found to be (9×10-4 lair/(lwater . ppm )). Around these two main areas of research supporting researches were undertaken. Studies found that dead bacteria were able to be removed by froth flotation as well as, or even better than live bacteria. Chlorination was faster than dechlorination under the same conditions by a factor of 25%. At low bacterial content, chlorine demand is directly proportional to cfu/ml. Zero bacterial content can be obtained through shock chlorination. The newly developed iPhone and iPad colony counting applications were investigated as a rapid way of measuring bacterial count. These were found to be reliable and accurate and, with additional manual manipulation proved very suitable to use for counting bacteria.
28
Kloppers, Lourens Marthinus. "Froth flotation of a Merensky platinum bearing ore with various THIOL collectors and their mixtures." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2481.
Анотація:
Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.The Bushveld igneous complex in northern South Africa has the largest deposit of platinum group elements (PGE) in the world. In trace amounts, these are closely associated with base metal sulphides (BMS). Froth flotation is used to beneficiate these PGE ores. The process constitutes a bulk sulphide recovery. Improvement of recovery of the BMS is required to maximise the recovery of PGEs. The performance of the froth flotation process is largely dependent on the chemical additives used and these chemicals have been extensively studied. Mixtures of collectors are widely used in the flotation of sulphide and platinum group mineral (PGM) ores. A range of performance benefits for the use of mixtures over pure collectors have been observed on many systems. These include improved valuable metal grades and recoveries, lower reagent dosage requirements, improved rates of flotation and enhanced recovery of coarse particles. Improvements observed with mixtures of chemical reagent have been attributed to synergism; defined as the interaction of two or more agents to produce a combined effect greater than the sum of their individual effects. Synergism is highly desired in froth flotation. For this study, mixtures of thiol collectors were used in batch froth flotation tests in an attempt to identify synergism between the different collectors on flotation performance of a typical platinum ore from the Merensky reef. Flotation performance was evaluated in terms of grades and recoveries of copper and nickel, and the rate of metal flotation. Single thiol collectors of xanthate (SIBX), a dithiocarbamate (DTC) and a dithiophosphate (DTP) were evaluated to determine the effect of functional group on flotation performance. SIBX was then used in mixtures with both DTC and DTP at various molar ratios to establish whether synergism occurs between these collectors on this particular platinum ore. Molar ratios of 90:10, 80:20, 70:30 60:40 and 50:50 were considered with SIBX being the major component. Further tests were conducted with the addition of a carboxymethyl cellulose depressant to the collector mixtures.
29
Miskovic, Sanja. "An Investigation of the Gas Dispersion Properties of Mechanical Flotation Cells: an In-Situ Approach." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/30223.
Анотація:
Bubble size is considered to be one of the most important parameters affecting the performance of froth flotation cells. However, monitoring, controlling and predicting bubble size is a very challenging task. This dissertation presents results obtained from a comprehensive pilot- and industrial-scale experimental investigation of gas dispersion performance of two commercially available flotation cells. To facilitate this investigation, a continuous pilot-scale flotation system was developed and tested. The results of the hydrodynamic and metallurgical testing conducted on the pilot-scale flotation circuit are presented. In addition, an assessment of the impact of two commercially available rotor/stator mechanism designs on bubble generation was performed under non-coalescing conditions. Based on obtained results, the mechanisms of gas dispersion throughout the flotation cell and gas cavity formation behind the impeller blades have been presented and discussed.
A new in-situ optical bubble sampling method was also developed as part of this investigation. The new system allowed an accurate estimation of local bubble sizes and determination of overall gas dispersion patterns within the cell. The new method was compared to the existing ex-situ bubble sampling method commonly used in industry. Two image analysis techniques were also evaluated, i.e., a template matching BubbleSEdit technique and the edge detection Northern Eclipse technique. Significant variations in bubble size as a function of the sampling method, sampling location, operating condition, machine type and image analysis method were observed. Generally, bubbles observed with the in-situ sampling method appeared to be larger than bubbles recorded with the ex-situ method. Furthermore, the mean bubble size determined by the Northern Eclipse bubble sizing method was smaller than the BubbleSEdit value. The experimental tests also revealed that sampling location had a strong effect on measured local mean bubble size and bubble size distribution in both vertical and horizontal directions. In addition, aeration rate was found to have a profound impact on the gas dispersion pattern in the cell and on local bubble size. Agitation rate also had a significant effect on bubble size, although the degree of impact strongly depended on the agitation level, chemical conditions in the cell and the machine type.Ph. D.
30
Goodall, Craig Michael. "The effects of flotation variables on the bubble size, mixing characteristics and froth behaviour in column flotation cells." Thesis, University of Cape Town, 1993. http://hdl.handle.net/11427/23802.
31
Hunter, C. J. "An electrochemical investigation of the froth flotation of iron bearing sulphide minerals." Thesis, Brunel University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.351913.
32
Saracoglu, Mehmet. "FROTH FLOTATION PERFORMANCE ENHANCEMENT BY FEED CAVITATION AND MAGNETIC PLASTIC PARTICLE ADDITION." UKnowledge, 2013. http://uknowledge.uky.edu/mng_etds/9.
Анотація:
Froth flotation is the most commonly used process to recover and upgrade the portion of the coal preparation plant feed that has a particle size smaller than 150 microns. Problems that occur when employing froth flotation in the coal industry include i) coal surfaces that are weakly-to-moderately hydrophobic, and ii) flotation systems that are overloaded and limited by insufficient retention time.
Research was performed to evaluate techniques that could be implemented to improve flotation performance under the aforementioned scenarios. Pre-aeration of flotation feed using a cavitation system was extensively evaluated in laboratory and full-scale test programs. The benefits of adding hydrophobic, magnetic plastic particles were also investigated to improve froth stability and increase bubble surface area.
Laboratory tests revealed that pre-aeration through a cavitation tube improved coal recovery by as much as 20 absolute percentage points in both conventional cells and flotation columns when treating difficult-to-float coals. Carrying capacity increased by 32% which was projected to provide a 4 t/h increase in flotation recovery for a typical 4-m diameter flotation column. Product size analyses suggest that the improved particle recovery was more pronounced for the finest coal fractions as a result of particle agglomeration, resulting from the use of the nucleated air bubbles on the coal surfaces as a bridging medium. In-plant testing of a commercial-scale cavitation system found that feed pre-aeration could reduce collector dosage by 50% when no additional air is added and by 67% when a small amount of air is added to the feed to the cavitation system. At a constant collector dosage, recovery increased by 10 absolute percentage points with cavitation without additional air and 17 absolute points when additional air is provided.
The addition of hydrophobic plastic particles to the flotation feed at a 10% concentration by weight was found to substantially improve froth stability thereby elevating the recovery and enhancing carrying-capacity. Test results showed that the primary flotation improvements were directly linked to the coarsest particle size fractions in the plastic material which supports the froth stability hypothesis. Combustible recovery was increased up to 10 percentage points while producing the desired concentrate quality.
33
Marais, Corne. "Estimation of concentrate grade in platinum flotation based on froth image analysis." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5346.
Анотація:
Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2010.Thesis presented in partial fulfilment of the requirements for the degree MASTER OF SCIENCE IN ENGINEERING (EXTRACTIVE METALLURGICAL ENGINEERING) in the Department of Process Engineering at the University of Stellenbosch
ENGLISH ABSTRACT: Flotation is an important processing step in the mineral processing industry wherein valuable minerals are extracted. Flotation is a difficult process to control due to its complexity, meaning that the reversal of series of changes will not necessarily bring the process back to its original state. Expert knowledge is incorporated in flotation control through operator experience and intervention, which is subject to many challenges, creating the need for improvement in control. The performance of a flotation cell is often determined by evaluating froth appearance. The application of image analysis to capture, evaluate and monitor froth appearance poses multiple benefits such as consistent and reliable froth appearance evaluation. The objective for this study was to conduct a laboratory study for the collection of froth images with the purpose of evaluating the feasibility of using image information to predict platinum froth grade. Laboratory test work was performed according to a fractional factorial experimental design. Six variables were considered: air flowrate, pulp level and collector, activator, frother and depressant dosages. The laboratory study results were quantified by assay analysis. Analysis of variance only revealed the significant effect of pulp height and collector addition on flotation performance. Data pre-processing revealed information regarding feature correlations and variance contributions. Data analysis from captured images achieved reliable froth grade predictions using random forest classification and artificial neural network (ANN) regression techniques. Random forest classification accuracies of 86.8% and 75.5% were achieved for the following respective datasets: image data of each individual experiment (average of all experiments) and all image data. The applied ANN models achieved R2 values 0.943 and 0.828 for the same 2 datasets. An industrial case study was done wherein a series of step changes in air flowrate was made on a specific flotation cell. The limited industrial case study results supported laboratory study results. Multiple linear regression performed very well, reaching Rª values up to 0.964. Neural networks achieved slightly better with R2 values of up to 0.997. Based on the findings, the following main conclusions were drawn from this study: - Reliable predictions using classification and regression models on image data were proved possible in concept by the laboratory study, and supported by results from an industrial case study on a narrow system. The following main recommendations were made for further investigation: - Research over a larger range of operating conditions is needed to find a more comprehensive solution. - Investigations should be conducted to determine hardware requirements and specifications in terms of minimum resolution, lighting requirements, sampling frequency and data storage. Software requirements, specifications and maintenance challenges should also be investigated for implementation purposes once a more comprehensive solution has been found. - Strategies in terms of camera placement and model building will need to follow, giving special attention to a strategy to handle ore composition change.
AFRIKAANSE OPSOMMING: Flotasie is ‘n belangrike proses in die mineraal proseseringsbedryf vermoeid met die ontginning van waardevolle minerale. Die proses is moelik om te beheer vanweë sy kompleksiteit, wat verwys na die onvermoë om die proses terug te bring na sy oorspronklike toestand deur ‘n reeks veranderinge om te keer. In die algemeen word spesialis kennis deel van prosesbeheer deur die toepassing van operateurs se ervaring en ingryping, wat opsigself verskeie uitdagings bied wat die behoefte aan verbeterde beheertoestelle en strategieë daarstel. Die werkverrigting van flotasieselle word gereeld beoordeel op grond van die voorkoms van die skuim. Die gebruik van beeldverwerking om dié inligting vas te vang vir monitering en evaluering doeleindes hou verskeie voordele in, bv. konsikwente en betroubare evaluasie van die skuimvoorkoms. Die doelwitte vir hierdie studie was om ‘n laboratorium studie te loods vir die opname van skuimbeelde, met die doel om die bruikbaarheid van beeldinligting vir die voorspelling van die flotasieprodukkwaliteit, te ondersoek. Die laboratorium gevallestudie is uitgevoer aan die hand van ‘n fraksionele faktoriale eksperimentele ontwerp. Ses veranderlikes was ondersoek naamlik, lugvloeitempo, pulphoogte en versamelaar aktiveerder en depressant toevoeging. Die studie se resultate is gekwantifiseer deur die analise van die skuim inhoud. ‘n Analise van variansie het slegs die invloed van pulphoogte en versamelaartoevoeging op die flotasievertoning uitgelig. Data voorverwerking het inligting uitgelig rondom die veranderlikes se verhouding met mekaar. Data analise metodes, naamlik lukrake klassifiseringswoude en neurale netwerk regressie, is toegepas op die versamelde beelddata en het belowende resultate gelewer. Lukrake klassifiseringswoude het klasse gedentifiseer met akkuraathede van 86.8% en 75.5% vir die volgende onderskeie datastelle: individuele eksperimente se beeld data (gemiddeld oor alle eksperimentele lopies), alle beelddata as een stel. Die neurale netwerke het Rª waardes van 0.943 rn 0.828 gelewer vir dieselfde 2 datastelle. Die beperkte nywerheidsgevallestudie het verandering in lugvloeitempo toegelaat vir ‘n enkele flotasie sel. Die resultate het die bevindinge van die laboratorium gevallestudie gesteun. Veelvoudige lineere regressie het Rª waardes van tot en met 0.964 gelewer. Neurale netwerke het daarop verbeter met waardes tot en met 0.997. Die volgende hoof gevolgtrekkinge was duidelik vanuit die resultate: - Betroubare voorspellings was moontlik met die toepassing van klassifikasie en regressie modelle op die laboratorium studie data. Die resultate is ondersteun deur soortgelyke resultate van die beperkte nywerheidsgevallestudie. Die volgende hoof aanbevelings was gemaak vir verdere navorsing: - Navorsing oor ‘n wyer reeks proseskondisies is nodig om ‘n meer omvattende oplossing te vind. - ‘n Ondersoek moet geloods word om die hardeware vereistes en spesifikasies in terme van die minimum beeld resolusie, beligting vereistes, monsterneming tempo en die berging van data te bepaal. Sagteware vereistes, spesifikasies en instandhouding uitdagings moet ook ondersoek word vir implementasie doeleindes sodra ‘n meer omvattende oplossing gevind is. - Strategieë in verband met die plasing van kamers en die ontwikkeling van modelle is nodig, waarin spesiale aandag gegee moet word om die probleem van veranderende ertssamestelling op te los.
34
Fuenzalida, González Octavio Francisco. "Model predictive control of froth flotation processes aided by a dynamic simulator." Tesis, Universidad de Chile, 2018. http://repositorio.uchile.cl/handle/2250/150812.
Анотація:
Magíster en Ciencias de la Ingeniería, Mención Metalurgia ExtractivaA model and simulation based methodology is used to implement a multi-layer model predictive control (MPC) strategy for a rougher row of mechanical flotation cells. Pilot-scale tests are done to calibrate and validate both the process simulation models and the predictive simulation models. The hierarchical control strategy considers three layers: orchestrator, advanced control and basic control; is deployed, in a commercial control system and, tested in a pilot row. The orchestrator is divided in two: the row supervisor and the row optimizer. The row supervisor monitors and manages all the other components of the control structure. The optimizer is a MPC-based controller which optimal criterion is separation efficiency (SE) and; according to recent developments, that happens with a balanced mass-pull profile along the row. The advanced control layer includes individual cell MPC in coordination with a symbolic MPC for all pulp levels along the row. The basic control layer consists of single loop proportional and integral (PI) controllers and their corresponding valves and instruments. After simulation, the control layers are successively downloaded in an industrial controller, starting from the basic control layer and ending with orchestrator s algorithms. Then, the control structure provides good disturbance rejection against feed variabilities. Regarding the orchestrator, it supports smooth and logical transitions between control modes as well as good abnormal situation management. This work shows promising results of the power of integrated process control design and model based methodologies; allowing earlier and better selection and validation of: flotation machine technology, cutting edge instrumentation and, advanced control structure and strategies. Given pre-defined economic assumptions, estimated results are obtained for the simulated industrial scenario: almost 40 percent reduction of capital expenditure (Capex), with almost the same operational expenditure (Opex). From the total Capex reduction, almost 80% is due to integrated process and control design (IPCD), being the other 20% a consequence of advanced process control and optimization structure and strategies. MPC-based control algorithms show their potential to have a main role in mineral processing processes feasibility and optimality.
35
Kharva, Mohamed. "Monitoring of froth systems using principal component analysis." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52945.
Анотація:
Thesis (MScEng)--Stellenbosch University, 2002.ENGLISH ABSTRACT: Flotation is notorious for its susceptibility to process upsets and consequently its poor performance, making successful flotation control systems an elusive goal. The control of industrial flotation plants is often based en the visual appearance of the froth phase, and depends to a large extent on the experience and ability of a human operator. Machine vision systems provide a novel solution to several of the problems encountered in conventional flotation systems for monitoring and control. The rapid development in computer VISIon, computational resources and artificial intelligence and the integration of these technologies are creating new possibilities in the design and implementation of commercial machine vision systems for the monitoring and control of flotation plants. Current machine vision systems are available but not without their shortcomings. These systems cannot deal with fine froths where the bubbles are very small due to the segmentation techniques employed by them. These segmentation techniques are cumbersome and computationally expensive making them slow in real time operation. The approach followed in this work uses neural networks to solve the problems mentioned above. Neural networks are able to extract information from images of the froth phase without regard to the type and structure of the froth. The parallel processing capability of neural networks, ease of implementation and the advantages of supervised or unsupervised training of neural networks make them potentially suited for real-time industrial machine vision systems. In principle, neural network models can be implemented in an adaptive manner, so that changes in the characteristics of processes are taken into account. This work documents the development of linear and non-linear principal component models, which can be used in a real-time machine vision system for the monitoring, and control of froth flotation systems. Features from froth images of flotation processes were extracted via linear and non-linear principal component analysis. Conventional linear principal component analysis and three layer autoassociative neural networks were used in the extraction of linear principal components from froth images. Non-linear principal components were extracted from froth images by a three and five layer autoassociative neural network, as well as localised principal component analysis based on k-means clustering. Three principal components were extracted for each image. The correlation coefficient was used as a measure of the amount of variance captured by each principal component. The principal components were used to classify the froth images. A probabilistic neural network and a feedforward neural network classifier were developed for the classification of the froth images. Multivariate statistical process control models were developed using the linear and non-linear principal component models. Hotellings T2 statistic and the squared prediction error based on linear and non-linear principal component models were used in the development of multivariate control charts. It was found that the first three features extracted with autoassociative neural networks were able to capture more variance in froth images than conventional linear principal components, the features extracted by the five layer autoassociative neural networks were able to classify froth images more accurately than features extracted by conventional linear principal component analysis and three layer autoassociative neural networks. As applied, localised principal component analysis proved to be ineffective, owing to difficulties with the clustering of the high dimensional image data. Finally the use of multivariate statistical process control models to detect deviations from normal plant operations are discussed and it is shown that Hotellings T2 and squared prediction error control charts are able to clearly identify non-conforming plant behaviour.
AFRIKAANSE OPSOMMING: Flottasie is berug daarvoor dat dit vatbaar vir prosesversteurings is en daarom dikwels nie na wense presteer nie. Suksesvolle flottasiebeheerstelsels bly steeds 'n ontwykende doelwit. Die beheer van nywerheidsflottasie-aanlegte word dikwels gebaseer op die visuele voorkoms van die skuimfase en hang tot 'n groot mate af van die ervaring en vaardighede van die menslike operateur. Masjienvisiestelsels voorsien 'n vindingryke oplossing tot verskeie van die probleme wat voorkom by konvensionele flottasiestelsels ten opsigte van monitering en beheer. Die vinnige ontwikkeling van rekenaarbeheerde visie, rekenaarverwante hulpbronne en kunsmatige intelligensie, asook die integrasie van hierdie tegnologieë, skep nuwe moontlikhede in die ontwerp en inwerkingstelling van kommersiële masjienvisiestelsels om flottasie-aanlegte te monitor en te beheer. Huidige masjienvisiestelsels is wel beskikbaar, maar is nie sonder tekortkominge nie. Hierdie stelsels kan nie fyn skuim hanteer nie, waar die borreltjies baie klein is as gevolg van die segmentasietegnieke wat hulle aanwend. Hierdie segmentasietegnieke is omslagtig en rekenaargesproke duur, wat veroorsaak dat dit stadig in reële tyd-aanwendings is. Die benadering wat in hierdie werk gevolg is, wend neurale netwerke aan om die bovermelde probleme op te los. Neurale netwerke is instaat om inligting te onttrek uit beelde van die skuimfase sonder om ag te slaan op die tipe en struktuur van die skuim. Die parallelle prosesseringsvermoëns van neurale netwerke, die gemak van implementering en die voordele van die opleiding van neurale netwerke met of sonder toesig maak hulle potensieel nuttig as reële tydverwante industriële masjienvisiestelsels. In beginsel kan neurale netwerke op 'n aanpassende wyse geïmplementeer word, sodat veranderinge in die kenmerke van die prosesse deurlopend in aanmerking geneem word. Kenmerke van die beelde van die skuim tydens die flottasieproses is verkry by wyse van lineêre en nie-lineêre hootkomponentsanalise. Konvensionele lineêre hoofkomponentsanalise en drie-laag outo-assosiatiewe neurale netwerke is gebruik in die onttrekking van lineêre hoofkomponente uit die beelde van die skuim. Nie-lineêre hoofkomponente is uit die beelde van die skuim onttrek by wyse van 'n drie- en vyf-laag outo-assosiatiewe neurale netwerk, asook deur 'n gelokaliseerde hoofkomponentsanalise wat op k-gemiddelde trosanalise gebaseer is. Drie hoofkomponente is vir elke beeld onttrek. Die korrelasiekoëffisiënt is gebruik as 'n maatstaf van die afwyking wat deur elke hoofkomponent aangetoon is. Die hoofkomponente is gebruik om die beelde van die skuim te klassifiseer. 'n Probalistiese neurale netwerk en 'n voorwaarts voerende neurale netwerk is vir die klassifisering van die beelde van die skuim ontwerp. Multiveranderlike statistiese prosesbeheermodelle is ontwerp met die gebruik van die lineêre en nie-lineêre hoofkomponentmodelle. Hotelling se T2 statistiek en die gekwadreerde voorspellingsfout, gebaseer op lineêre en nie-lineêre hoofkomponentmodelle, is gebruik in die ontwikkeling van multiveranderlike kontrolekaarte. Dit is gevind dat die eerste drie eienskappe wat met behulp van die outo-assosiatiewe neurale netwerke onttrek is, instaat was om meer variansie by beelde van skuim vas te vang as konvensionele lineêre hoofkomponente. Die eienskappe wat deur die vyf-laag outo-assosiatiewe neurale netwerke onttrek is, was instaat om beelde van skuim akkurater te klassifiseer as daardie eienskappe wat by wyse van konvensionele lineêre hoofkomponentanalalise en drie-laag outo-assosiatiewe neurale netwerke onttrek is. Soos toegepas, het dit geblyk dat gelokaliseerde hoofkomponentsanalise nie effektief is nie, as gevolg van die probleme rondom die trosanalise van die hoë-dimensionele beelddata. Laastens word die aanwending van multiveranderlike statistiese prosesbeheermodelle, om afwykings in normale aanlegoperasies op te spoor, bespreek. Dit word aangetoon dat Hotelling se T2 statistiek en gekwadreerdevoorspellingsfoutbeheerkaarte instaat is om afwykende aanlegwerksverrigting duidelik aan te dui.
36
Sayed, Ahmed Ahmed S. "CAVITATION NANOBUBBLE ENHANCED FLOTATION PROCESS FOR MORE EFFICIENT COAL RECOVERY." UKnowledge, 2013. http://uknowledge.uky.edu/mng_etds/8.
Анотація:
Froth flotation is a widely used, cost effective particle separation process. However, its high performance is limited to a narrow particle size range, e.g., between 50 µm and 600 µm for coal and between 10 µm and 100 µm for minerals. Outside this range, the efficiency of froth flotation decreases significantly, especially for difficult-to-float particles of weak hydrophobicity (e.g., oxidized coal).
Nanobubbles integrated into a specially designed column flotation expanded the particle size range for efficient froth flotation as a result of increased probabilities of particle- bubble collision and attachment and reduced probability of detachment.
The major advantages of nanobubble enhanced flotation include lower collector and frother dosages since nanobubbles that are mostly smaller than 1 µm can be formed selectively on hydrophobic coal particles from dissolved air in coal slurry. Nanobubbles act as a secondary collector on particle surfaces, thereby resulting in considerably lower operating costs.
A systematic parametric investigation of the proposed technology was performed to understand the effects of process variables on separation performance with a typical coal sample using a specially designed flotation column and three 10-liters conventional flotation cells. Results indicate that the combustible recovery of a -150 µm coal increased by 5-50% in the presence of nanobubbles, depending on process operating conditions. Nanobubbles also significantly improved process separation efficiency and increased the flotation rate constant by more than 40%.
Theoretical evaluation of the innovative flotation technology was employed using specially designed apparatus to study the nanobubbles stability and the roles of nanobubbles on particle-bubble interactions, froth stability, and surface area flux. In addition, a detailed technical performance and economic evaluation was performed.
37
Ur, Rehman Bilal. "Modelling a Mineral Froth Flotation Process : Case Study: Minerals process at Boliden AB." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-51600.
Анотація:
We present an approach to model the dynamic of a copper flotation process. The conventional approach of system identification is applied to model the dynamics. In this research, experiments are performed to collect process data of determined input and output variables. It is followed by data pre-processing to handle outliers and to remove high frequency disturbances. Simulation and validation responses of linear estimated models, which captured the dynamic of the process, are presented. The long term goal is to use estimated models to design a models-based control system.
38
Mozaffari, Ezatollah. "A study of coarse particle recovery by froth flotation in the Jameson cell." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263391.
39
Forbes, Gordon. "Texture and bubble size measurements for modelling concentrate grade in flotation froth systems." Doctoral thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/9247.
Анотація:
Includes bibliographical references (p. 237-244).Numerous, machine vision systems for froth flotation have been developed over the last ten years; however, there are many aspects of the systems, that still require further development before they become one of the standard instruments present on industrial flotation operations. This thesis aims to address these problems by developing improved measurement techniques and showing how these measurements can be used to model the concentrate grad e of the flotation cell being monitored in a manner which is, directly usable by plant personnel. This thesis, presents an improvement to the watershed algorithm for the measurement of bubble sixe distribution in flotation froths. Unlike the standard watershed algorithm, it is able to measure accurate bubble size distributions when both large and tiny bubbles are present in a flotation froth image. Flotation froths with “dynamic bubble size distribution s” are introduced and methods of reducing the high dimensional bubble size distribution data associated with them are discussed. A method of using characteristic histograms of frequently occurring bubble size distributions is introduced and shown to be an appropriate method to use. A number of standard texture measures are best suited to the classification of flotation froth images. Results show that the Fourier ring and texture spectrum based features, perform well whilst having a relatively small computational cost for classifying new images. Video footage from selected industrial operations has been used for the development of improved algorithms for the measurement of froth surface descriptors. Analyses of the relationship, between froth velocity, bubble size, froth class and concentrate grade are made. The results show that it possible to use a unified approach to model the concentrate grade, irrespective of the site on which the measurements are made. Results from three industrial case studies show that bubble size and texture measures can be used to identify froth classes. Furthermore the combination of froth classes and froth velocity information is shown to consistently account for the most variation in the data when the concentrate grade is modelled using a linear combination of these two measurements.
40
Quinn, Jarrett. "Exploring the effects of salts on gas dispersion and froth properties in flotation systems." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99532.
Анотація:
Several mineral flotation plants utilize process water with high soluble salt content. The processing of soluble minerals, the use of recycle streams, sea or well water give rise to this situation. It is unclear as to the overall effect on flotation response though there does seem to be evidence of bubble size reduction, increased froth stability and reduced reagent dosage. The present work aims to quantify the effects of salts commonly present in process water on gas dispersion (bubble size and gas holdup) and froth properties (solid and liquid overflow rates) and to compare to a typical frother, MIBC (methyl isobutyl carbinol). Three sets of experiments were run: 2-phase, 3-phase using talc and 3-phase using ore. All tests were run in a laboratory column. The salts examined in the 2-phase tests were NaCl, CaCl₂, Na₂SO₄, Na₂S₂O₃ and Al₂(SO₄)₃. Tests were conducted to determine the effects of salt type and concentration on gas holdup, bubble size distribution and foaming. The salts containing multivalent ions had a greater impact than did the monovalent ions, in keeping with the literature. A relationship between gas holdup and ionic strength was established. The effects of NaCl and MIBC on frothing and on solid and liquid overflow rates in 3-phase tests using 1%w/w talc were investigated. The results showed increased frothing and overflow rates upon the addition of NaCl, comparable to adding MIBC. Three-phase tests using ore (Falconbridge's Brunswick Mine) explored the effect of NaCl concentration. The results show reduction in bubble size and increased gas holdup in salt solutions comparable to those in the 2-phase tests. For each case, the concentration of MIBC giving equivalent gas holdup and frothing as the salt systems was determined. Proposed mechanisms for coalescence inhibition and froth stability in salt solutions are briefly reviewed in light of the current findings.
41
Siame, Edward. "Recovery of lithium from china clay waste using a combination of froth flotation, magnetic separation, roasting and leaching." Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3096.
Анотація:
This study was aimed at recovering lithium from china clay waste using a combination of froth flotation, magnetic separation, roasting and leaching. The china clay waste produced by Goonvean Ltd contains about 0.84% Li2O and 0.36% Rb2O, present in some of the mica minerals. Among the mica minerals, zinnwaldite is the major source of lithium with smaller amounts being contributed by muscovite. The results of the flotation tests showed that the dodecylamine collector dosage had a greater effect on the recovery and grade of mica minerals to concentrate than pH over the range tested. It was found that a mica concentrate containing 1.45% Li2O, 0.55% Rb2O and 4.47% Fe2O3 could be produced at a recovery of 98.6%, 85.2% and 92.8% respectively. Mineralogical analysis of the flotation products showed that the concentrate consisted mainly of muscovite, zinnwaldite and kaolinite with minor amounts of K-feldspar and quartz. The tailing consisted of mainly quartz, K-feldspar and kaolinite with minor amounts of apatite, topaz, zinnwaldite and muscovite. Further upgrading of the concentrate was found to be possible using a wet high intensity magnetic separator producing a magnetic fraction containing 2.07% Li2O, 0.74% Rb2O and 7.42% Fe2O3 with a recovery of 73%, 67% and 77% respectively. A mineralogical analysis of the separation products showed that the magnetic fraction consisted of predominantly zinnwaldite with muscovite as the main contaminant. The non-magnetic fraction consisted of muscovite and kaolinite as the main minerals while zinnwaldite, K-feldspar and quartz were subordinate. Electron-microprobe analysis on individual mica grains have shown that zinnwaldite and muscovite contain on average a calculated Li2O content of 3.88% and 0.13% respectively. Lithium extraction from the concentrate is only possible after the lithium has been converted into a water-soluble compound. Thus, in order to convert the lithium in concentrate into a water-soluble compound, the gypsum and limestone lithium extraction methods together with the new method of using sodium sulphate were investigated. The process involved roasting a predetermined amount of lithium-mica concentrate with either gypsum, limestone or sodium sulphate at various temperatures and subsequently leaching the pulverised materials in water at 85oC. A lithium extraction efficiency of about 84% was obtained using gypsum at 1050oC while rubidium extraction was very low at 14%. It was found possible to extract about 97% Li and 16% Rb if the concentrate was roasted with sodium sulphate at 850oC. Processing the concentrate with limestone resulted in very low lithium extraction. Iron co-extraction was low in all cases. The XRD analysis of the gypsum and sodium sulphate roast-products showed that the water soluble lithium species were KLiSO4 and Li2KNa(SO4)2 respectively. Preliminary tests on the leach solution obtained by using sodium sulphate as an additive have shown that a Li2O3 product with a purity of > 90% could be produced by precipitation with sodium carbonate although more work is required to reach the industrial target of > 99%. The lithium carbonate obtained with Li2CO3 content of about 90% is still suitable for use in the glass and ceramic industries, and as feedstock for the production of high-purity lithium compounds. An economic evaluation of the proposed lithium carbonate production plant has indicated an annual rate of return on the investment before tax of 7.2%.
42
Kaya, Muammer. "The effect of air flow rate and froth thickness on batch and continuous flotation kinetics /." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63358.
43
Mathe, Z. T. "Modelling the influence of the froth phase on recovery in batch and continuous flotation cells." Doctoral thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/10851.
Анотація:
To determine model parameters, a large data set was required. This is due to the semi-empirical nature of the proposed froth model. In this regard, the use of data obtained from continuously operated cells was therefore not suitable for deriving model parameters. It was thought that this could only be achieved by using data obtained from a batch flotation cell. A batch flotation cell has a distinct advantage of being suitable for generating, rapidly, large amount of data. However, the non-steady behaviour of froths found in this type of cell require a robust methodology for extracting the necessary parameters. In return this methodology was developed in this thesis. The main hypothesis of this methodology is that batch flotation performance, in terms of recovery, can be adequately approximated by treating a batch test as if it consists of a series of tests carried out in continuously operated flotation cells. Each flotation time interval is regarded as a single stage. Treating batch data in this manner allows for the derivation of desired kinetic parameters to describe flotation performance.
44
Moimane, Tiisetso Makheane. "Investigation of the effect of the reagent suite in froth flotation of a Merensky ore." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/20088.
Анотація:
The mining industry is faced with a challenge to develop efficient and economically feasible processing routes owing to the depletion of high-grade ores, and the ever increasing demand for precious metals for a wide range of applications. The valuable minerals, PGMs (Platinum Group Minerals) and BMS (Base Metal Sulphides) in the ores are extracted through the aid of chemical reagents (activators, collectors, depressants, frothers, modifiers) which are added to the flotation circuits to facilitate the separation between these minerals and the undesired gangue minerals present in the ore. The process is made complex by many surface reactions taking place, the existence of secondary and interactive effects among the flotation reagents, as well as the surface liberation of the minerals. Owing to the stringent regulations around water usage, concentrator plants are left with no option but to recycle water within their operations. This practice leads to accumulation of pollutants, such as organics, flotation reagents residues, dissolved ions, etc., which will likely have an influence on the chemical environment of the process, and subsequently will bear an impact on the overall metallurgical performance of the concentrator. This makes the process even more intricate, making it difficult to account for the behaviour of the chemical reagents, as well as making it virtually impossible to precisely assess their individual contribution to the overall flotation performance. Hence it is of crucial importance to adopt a holistic approach when investigating the effects of the chemical parameters in a flotation process. This is a flotation chemistry study that adopted a two-level-four-factor (24) factorial experimental design to evaluate the simultaneous effects of the chemical parameters, with particular reference to collector, depressant, frother, and ionic strength of the synthetic plant water, as well as determining the possible interactive effects between the chosen parameters. This investigation was made possible by conducting batch flotation tests on a PGM-bearing ore from the Merensky reef of the Bushveld Igneous Complex. Sodium isobutyl xanthate (SIBX), a polysaccharide, namely guar gum, and a polyglycol ether, namely Dowfroth 250 were used as the collector, depressant and frother, respectively. These are the typical chemical reagents the dosages of which tailored in the PGM industry for the processing of the ores. The metallurgical performance indicators used were solids, water, copper and nickel recoveries as well as copper and nickel grades.
45
Do, Hyunsun. "Development of a turbulent flotation model from first principles." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/28285.
Анотація:
Flotation is a process of separating particulate materials of different surface properties in a hydrodynamic environment, and is used extensively for separating different minerals from each other in the mining industry. In this process, air bubbles are introduced at the bottom of a particulate suspension (pulp), so that bubbles coated with hydrophobic particles rise to the top and form a froth phase while hydrophobic particles stay in suspension. The selectivity of the flotation process is determined by the hydrophobicity of the particulate materials involved, while the kinetics of the process is controlled by the hydrodynamic conditions and the disjoining pressures in the thin aqueous films between air bubbles and particles.
In the present work, a mathematical model for the flotation process has been developed by considering both the hydrodynamic and surface chemical parameters. The model can describe the events occurring in both the pulp and froth phases of a mechanically-agitated flotation cell. The pulp-phase model is based on predicting the kinetics of bubble-particle attachment using the DLVO extended to include contributions from hydrophobic force and the theory of turbulent collision. The froth-phase model is based on predicting the rate of bubble-particle detachment by considering bubble coarsening and water recovery. The predictions from the overall flotation model are in general agreement with the results obtained in single-bubble flotation experiments and the flotation test results reported in literature. Since the model has been developed largely from first principles, it has predictive and diagnostic capabilities.Ph. D.
46
Crawshaw, Simon A. M. "An investigation into the effects of the froth phase on the recovery of coal by flotation." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278728.
47
Fundikwa, Bridget. "Environmental Performance Assessment of Froth Flotation for Coal Recovery and Sulfur Removal from Ultrafine Coal Waste." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/21191.
Анотація:
The South African coal mining industry generates large volumes of coal ultrafine waste (< 150 microns) each year, with a significant amount being dumped in tailing slurry dams. These slurry dams have been associated with prolonged pollution and loss of valuable resources. In the two stage flotation process developed at the University of Cape Town, froth flotation is used to both recover coal (stage 1) and remove pyritic sulfur (stage 2) from ultrafine coal waste, resulting in three outputs streams: a saleable coal product, a small volume sulfide-rich stream, and a reduced volume sulfide lean tailings stream. Pre-disposal removal of sulfide sulfur and coal recovery by means of froth flotation is aimed at effectively removing the acid rock drainage (ARD) risk associated with sulfide bearing waste s and at recovering valuable resources respectively. Previous studies have demonstrated the technical feasibility of this process for a number of coal waste types on a laboratory-scale, with results indicating that it is possible to recover large quantities of useable coal whilst generating a tailings waste stream with a reduced sulfur content and negligible ARD risk. An order of magnitude financial model for a fictitious plant has also been developed, and applied to demonstrate the economic viability for s elected case studies. To date, however, studies on the environmental viability of the process have only focused on the ARD mitigating potential of the two-stage flotation process and little attention has been given to the systemic environmental implication s of the process such as the energy and reagent usage. The research study therefore aims to evaluate the environmental burdens and benefits of the two-stage flotation process, particularly from a South African context, and to compare the environmental performance to the conventional disposal of untreated coal ultrafines. Furthermore, this project aims to establish which stages along the process contribute the most to the environmental burdens of the process and how the variations of the input parameters affect the overall environmental performance of the proposed process. To this end, a life cycle inventory of inputs and outputs was compiled on the basis of the empirical results derived from a previous laboratory-scale case study conducted on a sample of an acid generating ultrafine coal waste from the Waterberg region. Experimental results from the case study, which entailed two-stage flotation (using Naflote 9858 as a coal collector and xanthate (SIBX) as a sulfide collector in stages 1 and 2), and detailed characterisation of the feed and desulfurised tailings, was supplemented with literature information and data from mass and energy balance calculations for a fictitious plant. An environmental impact analysis was subsequently conducted using a combination of Life Cycle Impact Assessment and risk-based impact assessment techniques and criteria. The impact categories selected included climate change, terrestrial acidification, fossil fuel depletion, natural land transformation, aquatic water pollution risk, drinking water quality risk, aqueous acidification, salinity and consumptive water footprint. Aquatic water pollution risk, drinking water quality risk and aqueous acidification impact indicators were calculated by summing up risk potential factors for the constituents of the final disposed waste streams. The rest of the impact categories were calculated by multiplying the inventory result with a characterisation factor developed from impact assessment models The case study results indicated that the simple mentation of the two-stage flotation process results in a notable decrease in eco-toxicity, salinity, consumptive water footprint, metal toxicity, aqueous acidification, fossil fuel depletion and natural land transformation impacts. However, the results al so indicated an increase in atmospheric related impacts (climate change and terrestrial acidification impacts), which has been attributed to the additional energy consumption associated with the two-stage flotation process and the production processes associated with the flotation reagents. Analyses of the process contributions to the individual impact categories for the two-stage flotation process revealed the climate change and terrestrial acidification impact categories to be dominated by the electricity production process and the flotation reagents production process. The sensitivity analyses revealed a higher dependence of the fossil fuel depletion impact category on the percentage coal yield than the electricity consumption of the foreground process. Furthermore the sensitivity analyses indicated a strong dependence of the climate change and terrestrial acidification impacts on the electricity consumption and the SIBX dosage in the foreground process. In the South African context, implementation the two-stage flotation process would result in a significant recovery of coal (approximately 1.2 million tonnes for every 4 million tonnes dry coal ultrafines lost per annum) and a sulfide-rich product which can be utilised for electricity production and sulfuric acid production respectively, hence promoting resource efficiency. Although higher than in the case of conventional land disposal, the energy used in the two-stage flotation process is infinitesimal compared to the energy recovered in the process through the generation of additional coal, and results in only a 0.025 % increase in the annual greenhouse gas emissions. The implementation of the two-stage flotation would also result in reduced water losses in comparison to conventional land disposal, which is beneficial in the South African context as South Africa is a water scarce region. Lastly whilst the implementation of the two-stage flotation process would result in the reduction of water related impacts associated with acidification, salinization and metal pollution, it might pose a further threat to aquatic life if the xanthate salt reagents are emitted to local water sources. The limitations of the study were mainly associated with the quality of the input and output data, the impact categories and the system boundary and scenario development. The multiple sources of information and the variations in literature of the energy input estimates were noted as a source of uncertainty. The lack of characterisation factors for some of the substances in the system as well as the exclusion of the possibility of utilization of the sulfide-lean stream were also part of the limitations associated with the study. Recommendations for future work include improving the environmental assessment by incorporating various case studies and by incorporating downstream processing as well as optimizing the two-stage flotation process by using less energy and by using less toxic flotation reagents.
48
Bhutani, Gaurav. "Numerical modelling of polydispersed flows using an adaptive-mesh finite element method with application to froth flotation." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/39046.
Анотація:
An efficient numerical framework for the macroscale simulation of three-phase polydispersed flows is presented in this thesis. The primary focus of this research is on modelling the polydispersity in multiphase flows ensuring the tractability of the solution framework. Fluidity, an open-source adaptive-mesh finite element code, has been used for solving the coupled equations efficiently. Froth flotation is one of the most widely used mineral processing operations. The multiphase, turbulent and polydispersed nature of flow in the pulp phase in froth flotation makes it all the more challenging to model this process. Considering that two of the three phases in froth flotation are polydispersed, modelling this polydispersity is particularly important for an accurate prediction of the overall process. The direct quadrature method of moments (DQMOM) is implemented in the Fluidity code to solve the population balance equation (PBE) for modelling the polydispersity of the gas bubbles. The PBE is coupled to the Eulerian--Eulerian flow equations for the liquid and gas phases. Polydispersed solids are modelled using separate transport equations for the free and attached mineral particles for each size class. The PBE has been solved using DQMOM in a finite element framework for the first time in this work. The behaviour of various finite element and control volume discretisation schemes in the solution of the PBE is analysed. Rigorous verification and benchmarking is presented along with model validation on turbulent gravity-driven flow in a bubble column. This research also establishes the importance of modelling the polydispersity of solids in flotation columns, which is undertaken for the first time, for an accurate prediction of the flotation rate. The application of fully-unstructured anisotropic mesh adaptivity to the polydispersed framework is also analysed for the first time. Significant improvement in the solution efficiency is reported through its use.
49
Mbamba, Christian Kazadi. "Using froth flotation to mitigate acid rock drainage risks while recovering valuable coal from ultrafine colliery wastes." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10975.
Анотація:
This dissertation presents the results of an investigation to develop a two-stage flotation process to produce: (i) a low-volume sulfide-rich concentrate that can be treated chemically or biologically or disposed of in a contained manner; (ii) a high-volume (low sulfur) benign tailings, with low ARD potential compared to conventional tailings; and (iii) a coal concentrate that has added value on account of its low sulfur and ash content. Success requires integration of flotation, aqueous chemistry and mineral bioleaching expertise. The approach adopted in this exploratory study entails coal flotation in the first stage, which takes advantage of its natural hydrophobicity.
50
Morar, Sameer Harish. "The use of machine vision to describe and evaluate froth phase behaviour and performance in mineral flotation systems." Doctoral thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/11712.
Анотація:
Includes synopsis.Includes bibliographical references (leaves 179-190).
Within froth flotation, it is widely acknowledged that froth stability affects flotation performance. As a result, it is expected that through the effective management of froth stability, it would be possible to both control and optimise a flotation cell and bank. However, for this to be possible, the relationships between the operating conditions, froth stability behaviour and flotation performance attributes need to be well understood. In addition, froth stability would need to be measured using a robust method suitable for on-line operation. Within the literature, no robust methods are available to measure either the concentration of solids on the froth surface, or froth stability in a manner suitable for on-line operation. Thus, two novel non-intrusive machine vision measurements have been developed in this work to quantify these attributes.