Orientador: Carlos Gomes da Nave Mendes / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-04T11:01:23Z (GMT). No. of bitstreams: 1 Magalhaes_AlexFabianoRibeirode_M.pdf: 2242026 bytes, checksum: b4ae2e107eb7317d892ade5a7815f862 (MD5) Previous issue date: 2005 / Resumo:Com a intenção de preencher a lacuna decorrente de poucos estudos sobre o tratamento de efluentes da lavagem de veículos, na presente pesquisa, propõe-se um sistema de tratamento composto de biofiltros aerados submersos seguidos por flotação por ar dissolvido na remoção dos principais contaminantes contidos nos mesmos. Para isso, foi concebida, instalada e operada uma instalação protótipo em escala real, visando possibilitar a reutilização do efluente tratado. O sistema foi montado em uma transportadora e destinado ao tratamento dos efluentes de lavagens de caminhões tipo baú através de lavador tipo ¿rollover¿. Apesar de terem sido previstos três meses para a operação do sistema, vários problemas de origem operacional do próprio lavador de veículos impediram a realização dos testes de longa duração. Mesmo assim, o período de testes foi útil para estabelecer-se quais alterações físicas deveriam ser incorporadas à instalação proposta para a solução de diversos problemas específicos relativos à concepção original do sistema, subsidiando dados para a otimização de futuros sistemas a serem implantados em escala real. Concluiu-se que, após as modificações introduzidas, tais como a alteração de dispositivos de entrada e saída dos reatores, substituição de acessórios de controle de pressão e vazão, entre outros, a alternativa proposta para tratamento e reúso deste tipo de efluente é plenamente viável / Abstract: With the intention to contribute for aim of filling out the emptiness provoked by few studies on the treatment of carwash affluent, in this research, it intends to create a treatment system composed of aerated submerged biological filter (BAS) following for the dissolved air flotation (FAD) on the removal of the main pollutants present in this effluent type. For that, it was become designed, installed and operated an installation prototype in real scale, seeking the water recycling. The system was installed at cargo transport interprise and destined to the treatment of the carwash effluent type "rollover". In spite of it have been preview three months for the operation time of the system, several operational problems of the washer accomplish of the long time tests. Even so, the time of tests was useful to establish which physical alterations should be incorporate in the installation proposed for the solution of problems to the original conception of the system, subsidizing data for the otimization of the future systems to be implanted in real scale. This research was finish, after the modifications, such as the alteration of inlet and outlet devices of the reactors, pressure and flow control, among other, the proposal alternative for treatment and reuse of rollover type carwash effluent type is fully viable / Mestrado / Saneamento e Ambiente / Mestre em Engenharia Civil

Norrvatten är en av Sveriges största dricksvattenproducenter. Med ett ökande behov av en större produktionskapacitet och nya regleringar, planerar dem att förbättra sin reningsprocess. En aspekt som kräver omfattande undersökning är val av reningsmetod för att nå den nya gränsen från Livsmedelsverket för fyra PFAS kemikalier. PFAS är en grupp kemikalier som är mänskligt producerade sedan 1950-talet, vilka är persistenta och farliga för människors hälsa. Deras stabilitet i miljön leder till att de ackumulerar i naturen och hamnar i mat och dricksvatten. För att uppnå de nya regleringarna måste Norrvatten minska sin PFAS4 koncentration från cirka 5.7 ng/L till 4 ng/L. PFAS-separationen är planerad att genomföras via antingen aktivt kol eller en kombination där flotation även implementeras. Aktivt kol har en bevisad möjlighet att separera och destruera PFAS4, men nyligen har indikationer på en potential hos flotation uppenbarats. Dock är forskningen kring dess effektivitet begränsad vilket medför ett behov av att utvärdera dess användbarhet. Denna rapport syftar till att förse Norrvatten med ett underlag på effektiviteten och gynnsamheten med flotation inför beslutet att implementera flotation. Av den anledningen undersöktes separationseffektiviteten som uppnås i en befintlig flotationsbassäng i Norrvattens vattenverk. Genom att mäta PFAS4 koncentrationen i inflödet, utflödet och slammet kunde en borttagningseffektivitet på 19-38% bestämmas för olika belastningar. Slamkoncentrationen mättes till ungefär 200-700 ng/L. Felkällor kunde identifieras i mätningarna eftersom massbalansen inte stämde överens trots att mätosäkerheten från analysen adderades. Dessutom gjordes en omanalys av två prover som skilde sig från det förväntade resultatet, vilket gav avsevärda skillnader i resultatet. Trots att några felkällor kunde identifieras kunde inte en fullständig förklaring till avvikelserna fastställas. Trots detta kunde slutsatser dras att den uppmätta separationseffektiviteten och slamkoncentrationen kunde förse ett korrekt intervall. Dessutom indikerade resultaten att flotation inte kan appliceras enskilt för att nå koncentrationsmålet utan bör kombineras med kompletterande kolfilter f ̈or att nå gränsvärdet. Flotation ger upphov till en mer koncentrerad ström av PFAS som kräver behandling för att eliminera kemikalierna från miljöns kretslopp. Flera potentiella behandlingsmetoder identifierades för hur slammet kan hanteras. Jämförelsen inkluderade aktivt kolfilter, jonbytare, membran, oxidationsprocesser, sonolys, förbränning, deponi, jordrening, flotation, skumfraktionering, behandling på reningsverk och återanvändning för jordförbättring. Metoderna jämfördes utifrån bevisad robusthet, kostnad och applicerbarhet. Ett möjligt slamhanteringsalternativ visade sig vara ett sekundärt steg med flotation, förbränning av det uppkoncentrerade slammet och behandling av permeatet med jonbytare. Med den föreslagna slamhanteringen kunde implementering av flotation utvärderas baserat på maximal PFAS destruktion, ekonomi, koldioxidutsläpp och energiförbrukning. Det visade sig att energiförbrukningen är större för processen som inkluderar flotation men koldioxidutsläppen är mindre. Dock är det möjligt att avgränsningarna för koldioxid kan ha gynnat flotationsprocessen eftersom utsläpp från reaktivering av kolfilter inkluderades men inte utsläpp från förbränning eller energiproduktion. PFAS destruktionen blev ungefär 1-2% större för processen med exklusivt kolfilter eftersom flotationsprocessen innehåller ytterligare en ström som släpper ut PFAS efter behandling med jonbytare. Det mest ekonomiska alternativet visade sig bero på koncentrationsgränsen där implementering av flotation var dyrare för en PFAS4 koncentration på 4 ng/L i dricksvattnet, men billigare vid en gräns på 3 ng/L. Slutligen upptäcktes det att volymen av sekundärt slam som beräknades att skickas till förbränning har en stor påverkan på driftkostnaderna. Därför bör optimeringar genomföras för att minimera den sekundära slamvolymen om flotation implementeras. / Norrvatten is one of the largest drinking water producers in Sweden. With the need to increase their production capacity and new regulations, they are planning to improve their treatment process. One aspect that requires extensive investigation, is the treatment approach to reach the new limit from the Swedish Food Agency of four PFAS chemicals. PFAS is a group of chemicals that have been humanely produced since the 1950s, which are persistent and hazardous to human health. Their environmental stability causes them to accumulate in nature and ends up in foods and drinking water. To fulfill the new regulations, Norrvatten has to decrease the PFAS4 concentration in their drinking water from approximately 5.7 ng/L to 4 ng/L. The removal is planned to be achieved through either activated carbon filters or a combination where dissolved air flotation is included. Activated carbon has a proven separation and destruction possibility for PFAS4 but recently, DAF has appeared to be a promising alternative. However, there is limited research on its efficiency, which establishes a need for investigations on the potential of DAF for PFAS removal. To navigate Norrvatten through the decision between exclusively applying GAC filters or implementing a combination with DAF, this thesis intends to provide a basis of its efficiency and favorability. Therefore, this thesis investigated the removal efficiency that was obtained in one existing DAF basin in Norrvattens waterworks. By measuring the PFAS4 concentration in the inlet, outlet, and sludge flow, a removal efficiency of 19-38% was acquired for different flow levels. In addition, the sludge concentration was measured to approximately 200-700 ng/L in the water phase. Presence of sources of errors could be identified in the measurements as the mass balance did not add up despite the addition of the measurement uncertainty in the analysis. Also, two samples were analyzed twice as the results differed from the expected results, which provided significant variations. Although some sources of error were identified, a full explanation for the differing results could not be disclosed. However, through some consistency, it was possible to conclude that the removal efficiency and sludge concentration could provide an accurate interval to illustrate the reality. In addition, the results indicate that DAF cannot be applied alone to reach the concentration goal, but has to be combined with additional GAC filters to reach the target. DAF provides a separation of PFAS into a sludge stream that requires treatment to remove the chemicals from the environmental cycle. To investigate how the sludge could be managed, several treatment methods were identified. The comparison included GAC, AIX, membranes, oxidation processes, sonolysis, incineration, landfill, soil cleaning, DAF, foam fractionation, treatment at a wastewater facility, and reuse for soil improvement. The methods were compared based on proven robustness, cost, and applicability. It was concluded that a viable alternative was to transfer the sludge to a second stage of DAF, incinerate the concentrated sludge, and treat the permeate with AIX. From the sludge management proposal, the implementation of DAF was analyzed based on maximum PFAS destruction, economics, carbon emissions, and energy requirements. It was found that the energy requirement was larger for the process including DAF but the carbon emissions are smaller. However, the delimitations on the carbon emissions may have been in favor of the DAF process as the GAC reactivation emissions are included but emissions due to incineration or energy production are excluded. The PFAS destruction was approximately 1-2% larger for the process that excluded DAF as an additional stream containing PFAS would be released into the environment after AIX, which is not present when only GAC is implemented. The economic out-come depended on the concentration limit, where implementation of DAF was more expensive for a treatment target of 4 ng/L in the drinking water and more economical for 3 ng/L. Lastly, it was found that the volume of the concentrated sludge that would be sent for incineration had a large impact on the operational cost. Therefore, if DAF is implemented optimizations are of relevance to minimize the volume of that stream.

M. Tech. (Department of Metallurgical Engineering, Faculty of Engineering Technology), Vaal University of Technology. / Lonmin mining company located in the Bushveld Complex of South Africa is one of the main platinum group elements (PGEs) producers in the world. Its core operations are made up of 11 shafts and inclines. There are resources of 181 million troy ounces of 3PGE + Au, and there are reserves of 32 million ounces of 3PGE + Au. One of the ore type produced at Lonmin is UG2 ore which is dominated by the high presence of chromite. The UG2 ore is also associated with PGE assemblages divided into sulphides and non-sulphides, and it is beneficiated through the froth flotation technique. Froth flotation is a physico-chemical process that is used for separation of desired valuable minerals from the gangue minerals by utilising the difference in surface properties. The process has been achieving lower recoveries with P4 (shaft name) UG2 ore compared to Eastern Platinum Limited (EPL) UG2 ore when using similar reagents suite, this leads to loss of valuable minerals to the tailings, both ores were from Lonmin. The first step was to conduct the mineralogical analysis conducted using Scanning electron microscopy- energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and optical microscopy to study the mineral composition of the two ores, and to identify any differences between them (two ores) considering that EPL UG2 ore is a blend of P1, P2, P3 (shaft names) and P4 UG2 ores while P4 UG2 ore is not blended with any other ores. The mineralogical results showed the presence of chromite, plagioclase, enstatite and sulphide minerals. The PGEs could not be detectable by any of the techniques used due to their small size and rarity. However, X-ray diffraction detected differences in concentrations of minor gangue constituents such as talc, muscovite, chlorite and actinolite and these results suggest that reagent consuming gangue mineralogy may have contributed to the differences in PGE recoveries by flotation. Batch flotation tests were also conducted. The existing reagent suite consisted of CuSO4 as an activator, Sodium n-propyl xanthate (SPNX) as a collector, carboxymethyl cellulose CMC as a depressant, and Senfroth 200 as a frother, and this was a single collector system. Therefore it was imperative to conduct flotation n investigation on alternative collector blends in order to improve the recovery of P4 UG2 ore. SNPX was used as the primary collector and it was blended with the following co-collectors: alkyl dithiocarbamates (DTC), two formulations of S-alkyl-N-butyl thionocarbamates (ABTC C1 & ABTC C2), and two formulations O-isopropyl-N-ethyl thionocarbamate (IPETC 30 & IPETC 31), one co-collector at a time. The first test incorporated the SNPX at dosage of 150 g/t without a blend and this dosage was selected based on the current optimum practice used at Lonmin and to use as a benchmark for the project. Trying to maintain the same dosage of 150 g/t of collectors, SNPX + co-collector were blended at two different dosages of 100 g/t + 50 g/t, and was also due to the fact that the co-collectors were highly concentrated and small dosages were expected to perform very well with SNPX. Lastly, the SNPX + co-collector at dosages 100 g/t + 125 g/t, here the dosage of co-collector was very high compared to 50 g/t and this was to check the effect of high dosages of highly concentrated collectors on the performance of the ore. The flotation results showed that the use of 50 g/t of co-collectors yielded optimum PGEs + Au recoveries and grades, while the dosage of 125 g/t decreased recoveries and grades. The high dosage quantities of collectors do not necessarily mean they will yield improved recoveries and grades. Different chain structures can be used to alter the behaviour of a collector, and these may increase or decrease their capabilities to cause higher recoveries. By using a collector with a longer hydrocarbon chain the flotation limit may be extended without loss of selectivity, consequently bringing about greater water repulsion, instead of increasing the concentration of a shorter chain collector. At 100 g/t of SNPX and 50 g/t of co-collector i.e. SNPX + IPETC 30 yielded improved 3PGE + Au recovery of 85.7 % at 3PGE + Au grades of 60.14 g/t, compared to the unblended SNPX (150 g/t) which yielded 3PGE + Au recovery of 81.1 % but insignificantly higher grade of 60.53 g/t. On the other hand, SNPX + IPETC C1 blend yielded low 3PGE + Au recoveries compared to SNPX + IPETC 30 and SNPX + IPETC 31 blends, but it achieved the highest grade of 76.1 g/t. Evidently, this proves that the relationship between recovery and grade is a trade-off. The results have also shown the synergic effects, especially for SNPX blended with IPETC 30, and SNPX blended with IPETC 31 at dosage of 100 g/t (SNPX) and 50 g/t (IPETCs). It can be concluded that the different interaction obtainable from the thionocarbamate (ROCSNHR), effectively complement that from the xanthate ion (ROCS2–) to achieve more collector interaction at surface sites otherwise interactable for xanthate only. Therefore the collector blends rendered the mineral of interest hydrophobic and as a result the minerals were recovered to the concentrate. On the other hand, too much of collectors may not be beneficial. At the dosage of 100 g/t of SNPX and 125 g/t of collectors, SNPX + DTC attained lower recoveries compared to SNPX, SNPX + IPETC 30, SNPX + IPETC 31, however the grade was higher than achieved SNPX + IPETC 30, SNPX + IPETC 31 and SNPX + ABTC C1. Nevertheless, comparing these results to the dosage of 50 g/t of the co-collectors, the 125 g/t did not perform well at all. The dosage of 125 g/t of co-collectors lead to loss of collecting power and selectivity, especially for SNPX + IPETC 30, SNPX + IPETC 31, and SNPX + ABTC C1 blends. It is therefore wise to conduct an optimisation test to determine the correct dosing rate. In addition, the chromite entrainment was below the smelter limit and is very beneficial since chromite is detrimental to the furnace. Therefore, it is concluded that the blends of SNPX with IPETC 30 and IPETC 31 at a dosage 50 g/t have shown satisfying recoveries and the FeCr2O4 recovery is less than 1 % meaning there will not be any smelter penalties for FeCr2O4 content. Therefore, these are the recommended collector blends. It is recommended that further mineralogical study of the ores be conducted so that it may provide deeper insight into the causes of low recoveries under SNPX only. The system of blended collectors and its optimisation would be beneficial and can be practiced. The Chemisorption studies between the minerals and co-collectors used will provide more specific insight and details into the actual interaction synergy that gave the improved recoveries.

Chalcopyrite ore forms the significant fraction of copper deposits in the earth crust. However, it is also the most difficult to treat using conventional ferric leaching methods. Smelting and electro-refining are currently the methods used in treating chalcopyrite concentrate obtained from froth flotation. Due to the ever increasing environmental requirements on smelters by the Environmental Protection Agency, new smelters are scarce in the United States. The scarcity of smelters has led to the urgent need to find a novel leaching method for the abundant chalcopyrite deposits in the USA and the rest of the world. This chapter(one) of the dissertation, therefore, investigated the leaching of chalcopyrite ore at pH 2 using a newly discovered oxidant (peroxodisulfate). Our results show that chalcopyrite leaching using peroxodisulfate follows a surface reaction shrinking core model. The activation energy of chalcopyrite leaching using peroxodisulfate ion was calculated as 41.1 kJ mol⁻¹. We also report that the leaching of chalcopyrite ore is affected by particle size and that stirring hurts leaching of chalcopyrite. Additionally, we found that peroxodisulfate can produce from sulfuric ions electrochemically. Hydrogen peroxide, permanganate, peroxodisulfate and ferric ions are all strong oxidants that have been researched in production pregnant leach solution (PLS) from chalcopyrite ore leaching. Because, solvent extraction is the next step in the recovery of copper from pregnant leach solutions (PLS). The questions, therefore, arises as to the fate of the organic extractant used in solvent extraction coming in contact with strong oxidant residual in the PLS. In chapter two of the dissertation, we studied the effect of strong oxidant residual in PLS on the degradation of organic extractants during solvent extraction of copper. Exposed organic extractants were analyzed using interfacial tension(IFT), Fourier Transform Infrared (FTIR) spectroscopy and CG LS. The results obtained from IFT and FTIR analysis, show no effect on the organic extractants exposed to sunlight and PLS containing the residual strong oxidant. Finally in chapter 3, the dissertation exams alternative water source for the flotation of chalcopyrite. Mineral flotation is a water-intensive process in mining. In order to sustain mining operations such flotation, which rely heavily on water, chapter 3 of the dissertation looks at using alternative water sources (in this case reclaimed wastewater) in the flotation of chalcopyrite ores; this effort is to limit the mining industries dependence on fresh ground water particularly in the Southwest of United States where water is a scarce commodity. The research studied the effect of reclaimed waste water on chalcopyrite flotation via contact angle and surface energy measurements. Furthermore, atomic force microscopy (AFM) and flotation tests were used to supplement the findings from contact angle and surface studies. We conclude here that the contact angle of a pure chalcopyrite surface was determined to be 75.6 degrees. We also found that pure chalcopyrite mineral surface is slightly polar with surface energies γCuFeS2^(LW) = 41.4 mJ/m² (apolar), γCuFeS2^(AB) = 2.9 mJ/m² (polar). The high value of the surface energy indicates pure chalcopyrite surface is slightly hydrophobic.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The objective of this study is the assessment of the usefulness of an industrial machine vision system for laboratory studies of especially flotation froths and other foams. With this in mind it was attempted to meet three objectives. The first objective is the adjudication of the machine vision system's ability through image analysis to differentiate between characteristics of two-phase and three-phase systems. Secondly, through the use of image analysis the effect of varying surfactant concentration, as well as the addition of quartz particles on the foam/froth stability was quantified and thirdly it was attempted to define the nature of foam decay as stochastic or deterministic. While not as important in the industrial setting, the last objective is quite important when a laboratory system is concerned, even more so owing to the difficulty of quantifying the collapse or decay of foams and froths. Two experimental set-ups were used to attain above-mentioned objectives. A Leeds flotation cell was used for the flotation of the quartz with cetyltrimethylammonium bromide (CTAB) and octadecylamine (ODA) and as well as for the characterisation of the CTAB and ODA foam. A glass column was used to investigate the CTAB foam column decay. In both set-ups the foam/froth structures were monitored with an ELMO charged coupled device (CCD). The CCD was connected to a personal computer equipped with frame grabber, which captured and digitised the images. The following conclusions can be drawn from the experimental results: The machine vision system can differentiate accurately between surfactant groups of different concentration and thus groups with unique characteristics. 11 The stability of foam is highly correlated with all other foam variables extracted from the image analysis system. In particular, the movement of the foam/froth in the flotation cell has a substantial influence on the stability values obtained for the foam/froth. III As far as the experimental system was concerned, small quartz particles (- 75 urn) stabilised the froth, while coarser particles (75-106 urn, 106-150 urn and 150+ urn) destabilised the froth. IV Likewise, the decay of CTAB foam in a column was non-linear and deterministic. When observed manually, the decay of long life foams follow the same trend as short-life foams and short-life emulsions in that a specific decay constant can be calculated for a specific surfactant system. V The machine vision system is a viable alternative for current stability measurements. Firstly, no data processing need to be done to calculate a indirect stability parameter as it computes a direct stability parameter and secondly it also computes the bubble size distribution of the sample. The following recommendations are made: The experimental design of the system needs to be altered to minimise the effect the experimental environment has on results. The possibility of a different camera set-up must be investigated. The focus of the camera on the foam surface needs to be accurate as the computation of the stability value depends on the quality of the image obtained. Il The four factors that affect the stability of a flotation froth, namely solid concentration, particle size, particle type and particle hydrophobicity should be investigated in the same study. There exists many conflicting studies on this subject as many studies for different particles with a variety of sizes, hydrophobicity and concentration are performed. One study should be conducted where all four these factors are investigated under the same experimental conditions. III The method with which the image analysis system deal with fine froth need to be addressed. In laboratory systems a typical system investigated will show a dense foam with small bubble distributions as in the case of CTAB. The extent to which the grouping of fine froth as one bubble influence the instability values obtained needs to be investigated . / AFRIKAANSE OPSOMMING: Die doelwit van hierdie studie is die evaluering van die toepassing van 'n industriële masjienvisiesisteem in 'n laboratorium studie van hoofsaaklik flottasie skuim. Die doel van hierdie toepassing is drie-ledig. Die eerste doelwit is om die onderskeidingsvermoë van die masjienvisiesisteem tussen groepe met verskillende eienskappe te evalueer deur intydse beeld verwerking. Tweedens is die invloed van oppervlakmiddelkonsentrasie veranderinge asook die byvoeging van kwarts partikels op die stabiliteit van die skuim ondersoek. Derdens is die aard van die skuim verval ondersoek om vas te stelof die proses deterministies of stochasties is. Alhoewel laasgenoemde doelwit nie so belangrik is in die industriële toepassing nie, is dit van uiterse belang in die laboratorium studies, veral as gevolg van die probleme wat ondervind word in die kwantifisering van skuimverval. Twee eksperimentele opstellings is gebruik om bogenoemde doelwitte te bereik. 'n Leeds flottasiesel is gebruik vir die flottasie van kwarts met CTAB en ODA asook vir die karakterisering van CTAB en ODA skuimeienskappe. 'n Glaskolom is gebruik vir die ondersoek van die aard van skuimverval. In beide opstellings is die beelde gemonitor deur 'n ELMO CCD. Die CCD is verbind met 'n rekenaar wat toegerus is met 'n raam-vanger wat die beelde vang en digitiseer. Die volgende gevolgtrekkings kan uit die eksperimentele resultate gemaak word: Die masjienvisiesisteem differensieer akkuraat tussen oppervlakmiddel groepe van verskillende konsentrasies en dus ook tussen groepe met unieke eienskappe. 11 Die skuim stabiliteit korreleer met die ander skuim eienskappe naamlik gemiddelde area, gemiddelde omtrek, aantal borrels, fynheid van die beeld (SNE), beweging van die skuim en kleur van die skuim. Veral die beweging van die skuim in die flottasiesel het 'n beduidende invloed op die skuimstabiliteit. 111 In die genoemde eksperimentele sisteem IS gevind dat klein kwartspartikels (-75 urn) skuim stabiliseer terwyl groter partikels (75-106 urn, 106-150 urn en 150+ urn) skuim destabiliseer. IV Die verval van CTAB skuim in 'n kolom is nie-lineêr en deterministies. In die geval waar die verval van die CTAB met die hand gemeet is, is gevind dat die verval van 'n lang-lewe skuim dieselfde tendens as kort-lewe skuim en kort-lewe emulsies volg. 'n Spesifieke verval konstante kan bereken word vir 'n spesifieke oppervlakmiddel sisteem. v Die masjienvisiesisteem IS 'n werkbare alternatief in die meting van skuimstabiliteit. Anders as in bestaande stabiliteitsmetings waar 'n indirekte stabiliteitsparameter bereken moet word, bereken die sisteem 'n direkte stabiliteitsparameter asook die borrelverspreiding van die skuim monster. Die volgende aanbevelings kan gemaak word: Die eksperimentele ontwerp van die sisteem moet aangepas word om sodoende die invloed van eksperimentele kondisies op die resultate te verminder. Die moontlikheid van 'n alternatiewe kamera opstelling moet ook ondersoek word, aangesien die verkrygde stabiliteitswaardes afhanklik is van die kwaliteit van die skuimbeelde. 11 Daar is talle teenstrydige studies ten opsigte van die vier faktore wat die stabiliteit van flotasie skuim beinvloed naamlik erts tipe, partikel grootte, partikel hidrofobisiteit en vastestof konsentrasie. Hierdie faktore moet gelyktydig in 'n studie ondersoek word onder dieselfde eksperimentele kondisies. 111 Die masjienvisiesisteem groepeer fyn skuim gedeeltes saam as een borrel. Hierdie wyse van fyn skuim hantering moet aangespreek word aangesien 'n tipiese oppervlakmiddel sisteem in die laboratorium, soos in die geval van CTAB, digte skuim met 'n fyn borrelverspreiding toon. Die mate waarin die onvermoë van die sisteem om fyn borrels te herken die stabiliteitswaardes beïnvloed, moet ondersoek word.

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.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Flotation was introduced early in the zo" century as a separation process for extracting valuable minerals from grinded ore. Today flotation is a dominant mineral concentration method and is used for almost all sulphide minerals and also for nonsulphide metallic minerals, industrial minerals, and coal. Automation and control has become a basic requirement in flotation plants. Effective control of pulp levels plays a very important role in stabilising the flotation process and therefore requires careful attention. This thesis presents a de-coupled level controller that has been developed for the control of levels in cascaded flow processes, including multi-tank cascaded flotation processes. The controller was developed on a two tank cascaded pilot plant using water as a flow medium. A simulation model was constructed for the cascaded flow process. The simulation model made it possible to develop and evaluate a decoupled level controller in a simulation environment. Finally independent loop PIO control and integrated PIO control loops with feed-forward de-coupling were compared through simulation, as control strategies for the pilot plant. / AFRIKAANSE OPSOMMING: Flotasie is vroeg in die 20ste eeu bekend gestel as 'n skeidingsproses om waardevolle minerale te onttrek uit fyngemaalde erts. Vandag is flotasie die dominante proses om minerale te konsentrasie en word gebruik vir byna aile sulfied minerale sowel as nie-sulfied metaal minerale, industriele minerale and steenkool. Outomatisasie en beheer het 'n basiese vereiste geword in flotasie aanlegte. Die effektiewe beheer van pulpvlakke speel 'n baie belangrike rol in die stabilisering van die flotasie proses en verdien om hierdie rede deeglike aandag. Hierdie tesis stel 'n ontkoppelde vlakbeheerstelsel voor wat ontwikkel is vir die beheer van vlakke in kaskade vloei prosesse byvoorbeeld multi-tenk flotasie prosesse. Die beheerstelsel is ontwikkel op 'n twee-tenk kaskade toetsaanleg met water as vloeimedium. 'n Volledige simulasiemodel is ontwikkel wat dit moontlik gemaak het om die vlakbeheerstelsel te ontwerp, toets en verfyn in 'n simulasie omgewing. Verder is die verskil tussen onafhanklike enkellus PID beheerders en ontkoppelde PID beheerlusse ondersoek en word in die tesis geillustreer.

Focusing on reducing the air consumption of an air flotation rail system, a flowrate-amplified flotation element was recently developed. This new flotation element ulitises the rotational flow to intake extra air via an intake hole, and thus, effectively improves the flotation height. Compared to a conventional flotation element, the flowrate-amplified flotation element can reduce air consumption by approximately 50% for the same load and flotation height. To gain an understanding of the flow phenomenon in the flowrate-amplified flotation element, experiments and CFD simulations are conducted in this study. Based on the results, we found that the flowrate-amplified flotation element could take a part of the kinetic energy of the rotating air to suck in extra air. The intake hole greatly affects the pressure field and velocity field of the flotation element. Additionally, the effects of the variant gap height and supplied flow rate were also discussed. The results indicate that the pressure distribution decreases as the gap height increases and increases as the supplied flow rate increases.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: A Computational Fluid Dynamics (CFD) model was developed for the prediction of flotation rate constants in a stirred flotation tank and validated against experimental data. The model incorporated local, time-varying values of the turbulent flow field into an existing kinetic flotation model based on the Generalised Sutherland Equation to predict the overall flotation rate constant. Simulations were performed for the flotation of various minerals at different operational conditions and the predictions were compared with experimental data. It was found that the CFD-based model yielded improvements in the prediction of flotation rate constant for a range of hydrophobicities, agitation speeds and gas flow rates compared with existing methodologies, which use volume-averaged empirical expressions for flow variables. Moreover, comparing to the available CFD alternatives for the flotation modelling this approach eliminates the need for solving an extra partial differential equation resulting in a more computationally economic model. The model was developed in three stages. In the first, a single-phase model was used to establish the requirements for successful modelling of the velocity components and turbulent properties of water inside flotation tanks. Also, a novel use of the Grid Convergence Index for this application was carried out, which allowed determination of the maximum achievable reduction in numerical uncertainties through systematic grid refinement and adaptation. All subsequent simulations were performed at the optimal discretization level determined in this manner. It was found that the Moving Reference Frames (MRF) method was adequate for representation of the impeller movement when the rotational zone was located close to the impeller, using a time step advance of between 10◦ and 15◦ of impeller rotation. Comparison of the different turbulence models for the single-phase modelling revealed that the standard k-e and Large Eddy Simulation turbulence models both performed equally well and that the computational requirement was lower for the standard k-e model, making it the method of choice. Validation of the methodology was done by comparison with experimental data for two different stirred tanks including an unbaffled mixer and a fully baffled standard Rushton turbine tank. The validation against experimental data showed that the model was capable of predicting the flow pattern, turbulent properties and the generation of trailing vortices. The second stage of modelling used an Eulerian-Eulerian formulation for gasliquid modelling of gas-sparged fully baffled vessels (2.25 l, 10 l and 50 l) using a Rushton turbine. It was determined that the minimum model uncertainty resulting from simulation of the sparger was achieved using a disk sparger with a diameter equal to 40% of the impeller diameter. The only significant interfacial force was found to be the drag force, and this was included in the multiphase methodology. A parametric study on the available formulations for the drag coefficient was performed which showed that the effect of turbulence on the air bubbles can accurately be represented using the proposed model of Lane (Lane, 2006). Validation of the methodology was conducted by comparison of the available experimental gas holdup measurements with the numerical predictions for three different scales of Rushton turbine tanks. The results verified that the application of the designed sparger in conjunction with Lane drag coefficient can yield accurate predictions of the gas-liquid flow inside the flotation tank with the error percentage less than 6%, 13%, and 23% for laboratory, pilot and industrial scale Rushton turbine tanks, respectively. The last stage of this study broadened the Eulerian-Eulerian framework to predict the flotation rate constant. The spatially and temporally varying flow variables were incorporated into an established fundamental flotation model due to Pyke (Pyke, 2004) based on the Generalized Sutherland equation for the flotation rate constant. The computation of the efficiency of the flotation sub-processes also incorporated the turbulent fluctuating flow characteristics. Values of the flotation rate constants were computed and volume-weight averaged for validation against available experimental data. The numerical predictions of the flotation rate constants for quartz particles for a range of particle diameters showed improvements in the predictions when compared with values determined from existing methodologies which use spatially uniform values for the important hydrodynamic variables as obtained from empirical correlations. Further validations of the developed CFD-kinetic model were carried out for the prediction of the flotation rate constants of quartz and galena floating under different hydrophobicities, agitation speeds and gas flow rates. The good agreement between the numerical predictions and experimental data (less than 12% error) confirmed that the new model can be used for the flotation modelling, design and optimization. Considering the limited number of CFD studies for flotation modelling, the main contribution of this work is that it provides a validated and optimised numerical methodology that predicts the flotation macro response (i.e., flotation rate constant) by integrating the significance of the hydrodynamic flow features into the flotation micro-processes. This approach also provides a more economical model when it is compared to the available CFD models for the flotation process. Such an approach opens the possibility of extracting maximum advantage from the computed parameters of the flow field in developing more effective flotation devices. / AFRIKAANSE OPSOMMING: 'n Wye verskeidenheid van industriële toepassings gebruik meganies geroerde tenks vir doeleindes soos die meng van verskillende vloeistowwe, verspreiding van 'n afsonderlike fase in 'n deurlopende vloeistoffase en die skeiding van verskillende komponente in ‘n tenk. Die hoofdoel van die tesis is om ‘n numeriese model te ontwikkel vir ʼn flotteringstenk. Die kompleksiteit van die vloei (drie-dimensioneel, veelvuldige fases en volledig turbulent) maak die voorspelling van die werksverrigting van die flottasieproses moeilik. Konvensioneel word empiriese korrelasies gebruik vir modellering, ontwerp en die optimalisering van die flotteringstenks. In die huidige studie word ‘Computational Fluid Dynamics’ (CFD) egter gebruik vir die modellerings doel, aangesien dit ‘n alternatief bied vir empiriese vergelykings deurdat dit volledig inligting verskaf aangaande die gedrag van vloei in die tenk. Die model is ontwikkel in drie agtereenvolgende stadiums. Dit begin met ‘n strategie vir enkelfase modellering in die tenk, vorder dan na ‘n gas-vloeistof CFD model en brei dan die tweede stap uit om ‘n CFD model te skep vir die skeidingsproses deur flottering. ‘n Enkelfase model, gebaseer op die kontinuïteits- en momentumvergelykings, dien as basis vir die flottasie model. Die ‘Multiple Reference Frames’ (MRF) metode word gebruik om die rotasie van die stuwer na te boots, terwyl die dimensies van die rotasie-sone gekies is om die gepaardgaande onsekerhede, insluitend die model- en numeriese foute veroorsaak deur die dimensies van die roterende sones, te verminder. Die turbulensie model studie het getoon dat die standaard k-e turbulensie model redelike akkuraatheid kon lewer in die numeriese voorspellings en die resultate verskil in gemiddeld net minder as 15% van die eksperimentele lesings, terwyl die rekenaartyd min genoeg was om die simulasies op 'n persoonlike rekenaar uit te voer. Verder het die ‘Grid Convergence Index’ (GCI) metode die inherente onsekerhede in die numeriese voorspellings gerapporteer en gewys dat die onderskatting van die turbulensie wat algemeen plaasvind reggestel kan word deur van ‘Large Eddie’ (LES) of ‘Direct Numerical Simulations’ (DNS) gebruik te maak. Die metode wat ontwikkel is, is op twee tipes geroerde tenks getoets, naamlik 'n onafgeskorte menger en 'n standaard Rushton turbine tenk. Die numeriese resultate is teen eksperimentele data gevalideer en het gewys dat die model in staat is om die vloeipatrone, turbulensie einskappe en die vorming van agterblywende vortekse te voorspel. Die CFD resultate het getoon dat die vloeipatroon twee simmetriese rotasies siklusse bo en onder die roterende sone vorm, terwyl die vlak van die ooreenkoms tussen die numeriese voorspellings van die turbulente eienskappe en die eksperimentele lesings met minder as 25% verskil. As die tweede stap van hierdie navorsing is 'n Eulerian-Eulerian struktuur ontwikkel vir die gas-vloeistof modellering binne 'n standaard Rushton turbine flotteringstenk. Soos vir die enkelfase modellering is die Reynolds spanningstensor opgelos deur die standaard k-e turbulensie model, terwyl die lugborrels ingevoer/versamel is in/van die tenk deurmiddel van bron/sink terme. Verskeie ‘sparger’ rangskikkings is in die tenk geïmplementeer om die onsekerheid in die model weens die metode van luginspuiting te verminder. Verder is verskillende korrelasies vir die sleursyfer vergelyk vir laminêre en turbulente vloei in die tenk. Daar is gevind dat die skyf ‘sparger’, met 'n deursnee gelykstaande aan 40% van die stuwer deursnee, in samewerking met die voorgestelde model van Lane (Lane, 2006) vir die bepaalde sleursyfer die naaste ooreenkoms met die eksperimentele metings lewer (met 'n gemiddelde verskil van minder as 25%). 'n Vergelykende studie is ook uitgevoer om die gevolge van die gas vloeitempo en roerspoed vir drie verskillende geroerde tenks met volumes van 2.5 l, 10 l en 50 l te ondersoek. Die resultate van hierdie afdeling bevestig dat die CFD metode in staat was om die gas-vloeistof vloei in die flotteringstenk korrek te voorspel. Die veelvuldigefase model wat ontwikkel is, is uitgebrei vir flottasie modellering. Dit behels die integrasie van die CFD resultate met die fundamentele flottasie model van Pyke (Pyke, 2004) vir die flotteringstempo konstant. Die CFD model is toegerus met Pyke se model deur aanvullende gebruiker gedefinieerde funksies. Die CFD-kinetiese model is geëvalueer vir die flottering van kwartsdeeltjies en die resultate het die geloofwaardigheid van die model bevestig, aangesien die gemiddelde verskil tussen die numeriese voorspellings vir die flotteringstempo konstante en die eksperimentele data minder as 5% was. Die resultate is ook vergelyk met die analitiese berekeninge van Newell en daar is bevind dat die model vergelykbare voorspellings van die flotteringtempo konstantes lewer, met die ‘root mean square deviations’ (RMSD) gelyk of minder as die RMSD waardes vir die analitiese berekeninge. Verdere ondersoeke van die CFD-kinetiese model bestaan uit 'n parametriese studie wat die gevolge van die roertempo, gas vloeitempo en die oppervlak hidrofobisiteit op die flottering van kwarts- en galenietdeeltjies bestudeer. Die aanvaarbare ooreenkoms tussen die numeriese voorspellings en eksperimentele data (oor die algemeen minder as 12% fout) bewys dat die nuwe model gebruik kan word vir flotterings modellering en optimalisering.

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