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

The flotation process has been used and extensively researched over the past 100 years; however some aspects still remain a great mystery. While most research in the past has focussed on the pulp phase of the process, recently there has been a significant trend towards investigating the froth phase. This study focuses on the froth phase and investigates the processes that occur within this zone in a well defined and controllable system under particular operating conditions, namely changes in frother type and concentration, as well as particle type and concentration.

A simplified froth model is proposed, which describes the froth transportation characteristics in three different regions of a flotation froth. In the stagnant region, new froth arrives at the same rate as froth collapses and returns to the pulp, so there is no net exchange between this region and other regions. In the second region, the froth rises vertically from the pulp-froth interface until it reaches the concentrate launder weir level. Then, the froth moves horizontally towards the launders in the surface froth region. Based on the mass balance of air passing through the froth phase, a mathematical model of froth transportation is developed for a cylindrical flotation cell. The model describes froth transportation time from the point of entry at the pulp-froth interface to the concentrate launder as a function of the geometrical dimensions of the flotation cell, the concentrate launder and froth crowder designs, as well as cell operating conditions and froth properties. The model was validated in two industrial scale flotation cells, viz. an Outokumpu 3 m3 tank cell at the Western Metals Hellyer concentrator and an Outokumpu 50 m3 tank cell at the Anglo Platinum Bafokeng-Rasimone concentrator, under various cell operating conditions and concentrate launder/froth crowder configurations. The results show that the model in general fits the experimental data well. Model fitting can be improved by taking into account the actual air dispersion profile in the flotation cell. Although the current form of froth transportation model does not explicitly relate the surface froth velocity to the pulp level setting, it was found during the plant test work that froth height can affect froth transportation and that the effect is associated with ore type and froth viscosity. A preliminary investigation into froth rheology was carried out separately in the Oukokumput 3 m3 tank cell at the Xstrata Mt Isa copper concentrator. The results are included in this thesis for future reference. In addition to not accounting for the froth height effect (pulp level setting), the current froth transportation also has some limitations when used for prediction purposes. There are three parameters in the model related to the froth properties – the air hold-up in the froth (f), the froth height above the concentrate launder (hf) and the froth instability factor (). These parameters depend on the ore and the cell operating conditions as well as the cell design, and cannot be modelled at present. Nevertheless, they can be measured directly in an existing flotation cell, which allows the model to be used for process control. Experimental measurement procedures and measured results from the industrial flotation cells are given in this thesis. The effect of the cell operating conditions is discussed. Finally, this thesis proposes a number of potential model applications, including the modelling of froth recovery of attached particles, the modelling of water recovery and entrainment, criteria for concentrate launder and froth crowder design, and a model for flotation process control based on froth images.

The purpose of this study is to investigate the impact of solvent addition to bitumen froth on the wettability of froth solids. The wettability of solids determines the transportation/partitioning of the solids between phases, which in turn affects the solids and water rejection in a Clark hot water extraction process (CHWE). The impact of solvents treatment on the wettability of froth solids was studied using both a model system and a real bitumen froth system. The vulnerabilities of four kinds of model minerals to hydrocarbon contamination/wettability alteration in different solvents were compared and discussed by considering solvent composition and mineral types. The wettability of solids extracted from the industrial froth using different solvents was also compared. The XRD analysis on these solids confirmed the partitioning behavior of solids observed in model solids system. The results from this study indicate that the composition of paraffinic/aromatic solvent in an industrial froth treatment process could be tailor-optimized to achieve a better solids/water rejection. / Materials Engineering

No description available.

M.Sc. (Eng.), Faculty of Engineering and the Built Environment, University of the Witwatersrand, 2012 / The aim of this research project was to test the response of ultra fine coal sourced at Klipspruit Colliery to froth flotation and the response of the froth flotation products to dewatering using two different types of filter presses, namely the Tecnicas Hidraulicas (TH) and the Ishigakhi presses. During test work, some difficulty was experienced with coarse material feeding the froth flotation pilot plant. This led to pilot plant modifications. Further process complexities necessitated laboratory scale flotation test work on the Klipspruit coal to be carried out. The results for both the laboratory scale and pilot plant test work for froth flotation indicated that froth flotation as applied to the Klipspruit fines was not economically feasible because neither the required quality of the product (calorific value of 27.80 MJ/kg) nor the product yield of 50% could be achieved when subjected to a primary and secondary stage of froth flotation. The coarse material, which fed the pilot plant and the Ishigakhi filter press, gave low moisture values (12.3%) not typical of ultra fine coal moisture values. However when fed with very fine particle size distributions, prior test work with the Ishigakhi showed that moisture values below 20% could be achieved. The moisture values obtained for very fine particles using the TH filter press on product thickener underflow material sourced at Goedehoop colliery reached values below 20%. Thus both of the two dewatering options, i.e. the Ishigakhi filter press equipment or TH filter press equipment for the ultra fine coal dewatering, can be utilized. Since the filter rate is the determining factor specifying filter press size, it was determined that a larger TH filter area is required in 1 comparison with the Ishigakhi press. Based upon the pilot and laboratory scale test work undertaken and the assessment of the results, it appears that both dewatering options could be successfully employed on a technical basis for the dewatering of coal flotation products, tailings and the arising raw ultra fine fraction. Froth flotation for Klipspruit ultra fine coal was deemed unfeasible for both pilot plant and laboratory scale tests conducted. For this reason a capital expenditure for the construction of a froth flotation plant at the Western Coal Complex Phola plant was not considered feasible since Klipspruit coal forms part of the feed that will feed the Phola plant. In conclusion, following dewatering using either the TH filter press or the Ishigakhi filter press, it was established that both froth flotation concentrate and unbeneficiated ultra fines gave acceptable total moisture results (below 20%). These dewatered raw ultra fines may therefore be blended into inland product as thermal coal to be utilised by Eskom for power generation. Based upon this premise, it is estimated that profits of 76.5 million Rand could be generated by blending Klipspruit ultra fine coal into thermal coal production at the new Phola plant.

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.

Este estudo foi feito a partir de uma amostra de carvão extraído na mina da Vale- Moçambique, localizada no distrito de Moatize, Província de Tete. O trabalho visa analisar o sistema de reagentes na flotação de finos de carvão mineral pertencente à camada UCB. Dentre os métodos de beneficiamento de carvão, a flotação se destaca como um dos mais importantes para a concentração deste material, em particular no tratamento de partículas finas. A alimentação total da planta de processamento da Vale- Moçambique é de 8000 tph de carvão, onde 10% dessa alimentação corresponde a fração fina que alimenta o circuito de flotação. O material utilizado nesse estudo apresentou uma granulometria 96% menor do que 0,25 mm. Os reagentes utilizados nos ensaios de flotação foram betacol e óleo diesel como agentes hidrofobizantes e MIBC como espumante. O intervalo de concentrações de betacol na primeira fase de ensaios foi de 200 g/t a 500 g/t, e na segunda fase foi de 200 g/t a 500g/t de óleo diesel e manteve-se constante o MIBC em 300 g/t. Os resultados mostraram que é possível, a partir de uma alimentação com o teor de cinzas em torno de 22,84%, obter produtos com teores abaixo de 10% de cinzas, com uma recuperação mássica em torno de 50%. A recuperação de matéria carbonosa também foi avaliada e apresentou resultados positivos. Complementando esse estudo, foi avaliado o efeito da recuperação de H2O e foi observado que para as concentrações de betacol as recuperações variaram de 6 a 9%, e para óleo diesel mais MIBC foram de 4 a7%. / This study was done from a sample of coal mined at the Vale-Mozambique mine, located in Moatize district, Tete Province. The aim of this work is to analyze the reagent system in the flotation of coal fines belonging to the UCB layer. Among coal processing methods, flotation stands out as one of the most important for the concentration of this material, in particular in the treatment of fine particles. The total feed of the Vale-Mozambique processing plant is 8000 tph of coal, where 10% of this feed corresponds to the fine fraction that feeds the flotation circuit. The material used in this study had a particle size of 96% smaller than 0.25 mm. The reagents used in the flotation tests were betacol and diesel oil as hydrophobizing agents and MIBC as frother. The range of betacol concentrations in the first test phase was 200 g / t at 500 g / t, and in the second phase 200 g / t at 500 g / t of diesel oil and MIBC were kept constant at 300 g / t. The results showed that it is possible, from a feed with the ash content around 22.84%, to obtain products with levels below of 10% ash, with a mass recovery around 50%. The recovery of carbonaceous matter was also evaluated and presented positive results. Complementing this study, the effect of H2O recovery was evaluated and it was observed that for the concentrations of betacol the recoveries ranged from 6 to 9%, and for diesel oil plus MIBC were 4 to 7%.

No description available.

Este estudo foi feito a partir de uma amostra de carvão extraído na mina da Vale- Moçambique, localizada no distrito de Moatize, Província de Tete. O trabalho visa analisar o sistema de reagentes na flotação de finos de carvão mineral pertencente à camada UCB. Dentre os métodos de beneficiamento de carvão, a flotação se destaca como um dos mais importantes para a concentração deste material, em particular no tratamento de partículas finas. A alimentação total da planta de processamento da Vale- Moçambique é de 8000 tph de carvão, onde 10% dessa alimentação corresponde a fração fina que alimenta o circuito de flotação. O material utilizado nesse estudo apresentou uma granulometria 96% menor do que 0,25 mm. Os reagentes utilizados nos ensaios de flotação foram betacol e óleo diesel como agentes hidrofobizantes e MIBC como espumante. O intervalo de concentrações de betacol na primeira fase de ensaios foi de 200 g/t a 500 g/t, e na segunda fase foi de 200 g/t a 500g/t de óleo diesel e manteve-se constante o MIBC em 300 g/t. Os resultados mostraram que é possível, a partir de uma alimentação com o teor de cinzas em torno de 22,84%, obter produtos com teores abaixo de 10% de cinzas, com uma recuperação mássica em torno de 50%. A recuperação de matéria carbonosa também foi avaliada e apresentou resultados positivos. Complementando esse estudo, foi avaliado o efeito da recuperação de H2O e foi observado que para as concentrações de betacol as recuperações variaram de 6 a 9%, e para óleo diesel mais MIBC foram de 4 a7%. / This study was done from a sample of coal mined at the Vale-Mozambique mine, located in Moatize district, Tete Province. The aim of this work is to analyze the reagent system in the flotation of coal fines belonging to the UCB layer. Among coal processing methods, flotation stands out as one of the most important for the concentration of this material, in particular in the treatment of fine particles. The total feed of the Vale-Mozambique processing plant is 8000 tph of coal, where 10% of this feed corresponds to the fine fraction that feeds the flotation circuit. The material used in this study had a particle size of 96% smaller than 0.25 mm. The reagents used in the flotation tests were betacol and diesel oil as hydrophobizing agents and MIBC as frother. The range of betacol concentrations in the first test phase was 200 g / t at 500 g / t, and in the second phase 200 g / t at 500 g / t of diesel oil and MIBC were kept constant at 300 g / t. The results showed that it is possible, from a feed with the ash content around 22.84%, to obtain products with levels below of 10% ash, with a mass recovery around 50%. The recovery of carbonaceous matter was also evaluated and presented positive results. Complementing this study, the effect of H2O recovery was evaluated and it was observed that for the concentrations of betacol the recoveries ranged from 6 to 9%, and for diesel oil plus MIBC were 4 to 7%.