Mineral flotation is the most widely used separation process applied for the concentration of metals sulphide particles from finely ground ores. However, flotation is a process that often has many problems which can affect its efficiency, mainly due to: • Variability of the feed stream characteristics • Inability to measure important process variables, such as the mineral floatability • A lack of understanding of the effect of circuit configuration and the mineral behaviour through the circuit The aim of this thesis is to investigate these issues using a steady state model applied to industrial data. The plants examined in this thesis were the Pillara Concentrator in Western Australia and the Charcas Concentrator in Mexico. In both cases the zinc circuit was surveyed to provide data for evaluation of simulation methods. The main characteristic of these ores is that the minerals are well liberated, and thus, the properties of flotation models can be evaluated without the confounding effects of composite particles. In terms of model building, there are a number of papers in the literature that offer models of various aspects of the flotation process such as chemistry, hydrodynamics, process kinetics, characterisation of the mineral flotation properties, and phase effects. The current JKMRC model methodology was developed in order to put together some of these aspects for the cases where the chemical environment remains constant. With aid of relatively simple well liberated ores this thesis investigates the combined use of plant data and batch cell flotation results from the various plant streams, as a means of determining additional properties of the process streams in the plant. It is shown that additional useful information is available for the batch tests. It is both an advantage and a problem that different types of data are obtained from the batch cells and the continuous plant cells. The ability of the models to predict is limited by the staged addition of reagent that change, as might be expected, the flotation properties of the ore. It is found for constant reagents and froth recovery that the models are capable of predicting the performance of parts of the industrial flotation plant. A recommendation for further work on the effects of froth recovery and reagents is made.

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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.

A bibliometria é um instrumento quantitativo que através de medidas matemáticas e estatísticas permite mapear e gerar informações que auxiliam na tomada de decisões de uma determinada área científica. Verificou-se o evidente crescimento da produção científica na área de flotação de caulinita e da significativa importância desse assunto em meios acadêmicos, realizou-se a necessidade de um estudo de natureza bibliométrica. Este estudo é uma maneira de observar a quantidade do que está sendo produzido, quais são os principais trabalhos desenvolvidos e quais foram os resultados atingidos. O presente trabalho apresenta uma discussão de natureza bibliométrica sobre artigos publicados no mundo, relacionados sobre o assunto flotação de caulinita, em periódicos internacionais no período de 1992 e 2015. Através deste trabalho foi possível reconhecer e identificar quais são as tendências temáticas e metodológicas que estão sendo usadas, além dos principais coletores utilizados na flotação de caulinita. Os resultados mostram que é significativa a quantidade de artigos produzidos por autores chineses, especialmente a partir do ano de 2013, visto ser a China a maior produtora de alumínio no mundo, e a caulinita, é o rejeito no processo de flotação reversa do diásporo. Foram encontrados muitos estudos com propostas e estruturas semelhantes, utilizando métodos que são importantes para compreender os fenômenos físico-químicos na flotação, como: métodos de caracterização mineralógica, potencial zeta, métodos de adsorção e outros. Os artigos analisados tinham uma média de 7 páginas por artigo e todos foram pesquisados no SciVerse ScienceDirect, pertencente à editora Elsevier. Dos 39 artigos analisados, 31 possuem avaliação interdisciplinar da Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) e são classificados no estrato A1, que são artigos de mais alta qualidade. Os resultados mostraram a dificuldade de trabalhar com o tema de flotação de caulinita individualmente e confirmou que existe uma colaboração científica entre autores. No estudo por palavras-chave, (ao todo 180) verificou-se a presença de termos como \"aluminossilicatos\", \"minérios oxidados\" e \"diásporo\" junto com o termo \"caulinita\", além de outras palavras-chave como \"flotação\" e \"adsorção\". Os minerais envolvidos na flotação junto com caulinita também foram avaliados, mineral diásporo aparece frequentemente relacionando com o mineral de interesse dessa dissertação. Na avaliação por citações pelo Scopus, os artigos foram classificados conforme sua importância no meio acadêmico. Além disso, através da análise bibliométrica verificouse que os reagentes utilizados nos testes de flotação de caulinita são de grande maioria derivados de nitrogenados catiônicos. Os valores de pH mais utilizado de flotação ocorreram em meio ácido, embora, muitos coletores apresentem também bons resultados em meio neutro e/ou alcalino. Observou-se também que ainda há muito para ser pesquisado, visto que a maior parte dos artigos amostrados realizam pesquisa em escala laboratorial e não descrevem a realidade das usinas de beneficiamento de caulinita no mundo. / Bibliometrics is a quantitative instrument that, through mathematical and statistical measures, allows to map and generate information that assists in the decision-making of a certain scientific area. In the area of kaolinite flotation, a clear growth of scientific production and a significant importance of this subject in academic areas were noted, thus warranting the need for a bibliometric study. This study is a way to observe the amount being produced, which are the main projects under development and which results have been obtained. The current work presents a bibliometric discussion on articles published worldwide concerning kaolinite flotation in international journals from 1992 to 2015. This work allowed to recognize and identify which are the thematic and methodological trends that are being used, in addition to the main collectors used in kaolinite flotation. The results show that a significant amount of articles is produced by Chinese authors, especially from 2013, as China is the largest aluminum producer in the world, and kaolinite is the reject in the reverse flotation process of diaspore. Many studies using methods that are important to understand physicochemical phenomena in flotation, with similar proposals and structures, were found, such as: mineralogical characterization methods, zeta potential, adsorption methods and others. Assessed articles had, on average, 7 pages each and all were searched in Elsevier\'s SciVerse ScienceDirect. Thirty-one out of the 39 analyzed articles have interdisciplinary evaluation of the Coordination for the Improvement of Higher Education Personnel (CAPES) and are rated at stratum A1, which corresponds to higher quality articles. The results showed the difficulty of working with kaolinite flotation individually and confirmed that there is scientific collaboration among authors. The study by keyword (180 in total) found terms as \"aluminosilicate\", \"oxidized ores\" and \"diaspore\" together with \"kaolinite\", in addition to other keywords, such as \"flotation\" and \"adsorption\". Minerals involved in flotation together with kaolinite were also evaluated, and diaspore mineral frequently appears related to the mineral of interest of this dissertation. Articles were rated according to their importance in the academic world using the assessment of citations by Scopus. In addition, bibliometric analysis showed that reagents used in kaolinite flotation tests are mostly derived from cationic nitrogenated compounds. Most used pH values in flotation are acidic, although many collectors also have good results in neutral and/or alkaline media. It was also noted that there is still much to be researched, since most articles sampled researched in laboratory scale and do not describe the reality of processing plants of kaolinite in the world.

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.

Field assessments were performed to establish the performance capabilities of a new flotation technology for fine coal upgrading, known as StackCell flotation. Flotation release analysis was performed on all samples to determine the amount of hydrophilic material present in the streams around the flotation cell. Data from this work supported recommendations from the equipment manufacturer that the wash water distribution system should be changed to a drip pan and that the design of the slurry-air distributor from the mixing chamber should be altered. The experimental data showed that as froth depth, rotor speed, and wash water rate changed, the performance of the cell followed expected trends with respect to product quality, but diverged from expected trends with respect to carbon recovery and yield. Other work performed includes the development of a new carbon partitioning test, which uses a blender to provide a high shear environment and uses oil to partition the slurry into a carbon rich oil phase and an ash rich pulp phase. This test is capable of producing results comparable to those of a traditional release analysis. Lastly, a spreadsheet program was developed that can aid users in designing drip pans. This program is capable of producing custom designs or unit cell designs. A study of the effect that plate thickness has on flow rate was performed in order to develop a model for flow through an orifice plate. The results of this work showed that plate thickness has little to no effect on the flow rate. / Master of Science

A study based on a statistically designed set of experiments (Box-Behnken design) has been conducted to determine the optimum conditions for advanced physical fine coal cleaning using microbubble column flotation. The dependent variables in these experiments were mass yield and product quality (ash, sulfur and btu), while the independent variables were feed solids content, collector dosage, frother dosage, feed rate, aeration rate, and wash water rate. The most important operating parameters in order of significant were found to be aeration rate, feed rate, frother dosage and wash water rate. The test data were found to fall along a single grade-recovery curve and just below the ideal separation curve predicted by release analysis, provided that a sufficient bias flow was maintained. The test results also demonstrated that various combinations of operating conditions can be utilized to achieve the same level of metallurgical performance. In order to develop an improved understanding of the behavior of column flotation cells, a simulation package was developed by incorporating guidelines developed from the parametric test data. Simulations were carried out by examining the effects of key parameters on the performance of a column flotation cell. The parameters that were found to have the most significant influence included column length/diameter ratio, aeration rate, feed rate, feed solids content, and pulp bubble size. It was also found that limitations arising from the carrying capacity of the froth phase can greatly impact the performance of large-scale flotation columns. It is believed that this simulator will be useful for the design, control, optimization and scale-up of column flotation. / Master of Science

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

Coal in the finer particle size ranges (below 1 mm) has always suffered from poor cleaning efficiencies. This problem has been exacerbated in recent years with the increased amount of high ash fines due to continuous mining machines and the mining of dirtier coal seams. In the present work, it is proposed to improve overall plant efficiencies by processing coarser coal in column flotation than is now commonly treated by that method. Column flotation for coarse coal is supported by actual lab and plant test data that result in a full-scale column plant installation. The fundamentals of coarse particle detachment from bubbles are reviewed and a new simplified model is developed which better handles cubical and rectangular coal particles. Much of the lower efficiency of fine coal cleaning is due to poor size separation of the fine-sized raw coal which results in misplaced high ash fines reporting to the coarser size streams. By sending coarser material to column flotation, the finest size separation that takes place in a plant can be as coarse as 0.5 mm or greater. The proper use of wash water in a flotation column then becomes the best mechanism for desliming of the high ash clays. This work quantifies the benefits of removing the high ash fines from the plant product and increasing overall plant yield by increasing the amount of near-gravity coarse material. The resulting yield gain is greater than that obtained from only the increased fine coal recovery. Methods of column operation for improved coarse coal recovery are also evaluated. / Ph. D.

A first principle flotation model has been derived from the basic mechanisms involved in the bubble-particle and bubble-bubble interactions occurring in flotation. It is a kinetic model based on the premise that the energy barrier (E1) for bubble-particle interaction can be reduced by increasing the kinetic energy (Ek) for bubble-particle interaction and by increasing the hydrophobic force in wetting films. The former is controlled by energy dissipation rate (𝜀), while the latter is controlled by collector additions. The model consists of a series of analytical equations to describe bubble generation, bubble-particle collision, attachment and detachment, froth recovery, and bubble coalescence in froth phase. Unlike other flotation models that do not consider role of hydrophobic force in flotation, the first principle model developed at Virginia Tech can predict flotation recoveries and grades from the chemistry parameters such as 𝜁-potentials, surface tension (𝛾), and contact angles (𝜃) that may represent the most critical parameters to control to achieve high degrees of separation efficiencies. The objectives of the present work are to i) validate the flotation model using the experimental data published in the literature, ii) incorporate a froth model that can predict bubble coarsening due to coalescence in the absence of particles, iii) develop a computer simulator for a froth model that can predict bubble coarsening in the presence of particles, and iv) study the effects of incorporating a regrinding mill and using a stronger collector in a large copper flotation circuit. The model validation has been made using the size-by-class flotation rate constants (kij) obtained from laboratory and pilot-scale flotation tests. Model predictions are in good agreement with the experimental data. It has been found that the flotation rate constants obtained for composite particles can be normalized by those for fully liberated particles (kmax), which opens the door for minimizing the number of flotation products that need to be analyzed using a costly and time-consuming liberation analyzer. A bubble coarsening froth model has been incorporated into the flotation model to predict flotation more accurately. The model has a limitation, however, in that it cannot predict bubble-coarsening in the presence of particles. Therefore, a new computer simulator has been developed to predict the effects of particle size and particle hydrophobicity on bubble coarsening in froth phase. In addition, the first principle flotation model has been used to simulate flotation circuits that are similar to the Escondida copper flotation plant to study the effects of incorporating a re-grinding mill and using a more powerful collector to improve copper recovery. The flotation model developed from first principles is useful for predicting and diagnosing the performance of flotation plants under different circuit arrangements and chemical conditions. / Master of Science