Direct measurement of entrainment in large flotation cells

Yianatos, J.; Contreras, F.; Díaz, Francisco Javier Llorca; Villanueva, A.

doi:10.1016/j.powtec.2008.05.013

Cited by 33 publications

(16 citation statements)

References 9 publications

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“…Livshits and Dudenkov (1965) suggested that their presence retarded film coalescence in the froth phase, improving stability, whereas Moudgil (1992) indicated that there is a tendency for coarse particles to rupture the thin films of bubbles, resulting in particles detaching and draining back into the froth phase. Yianatos et al (2009) demonstrated that coarse particle entrainment is insignificant using radioactive tracers in an industrial flotation cell, implying attachment is the dominant mechanism of recovery. Separately, Zheng et al (2006) indicated that coarse particles recovered at low air rates may be recovered through entrapment, their presence under specific operating conditions otherwise unexplained as they should settle out of the froth phase.…”

Section: Introductionmentioning

confidence: 99%

The effect of particle size distribution on froth stability in flotation

Norori-McCormac

Brito-Parada

Hadler

et al. 2017

Separation and Purification Technology

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Separation of particles of different surface properties using froth flotation is a widely-used industrial process, particularly in the minerals industry where it is used to concentrate minerals from ore. One of the key challenges in developing models to predict flotation performance is the interdependent nature of the process variables and operating parameters, which limits the application of optimising process control strategies at industrial scale. Froth stability, which can be quantified using air recovery (the fraction of air entering a flotation cell that overflows in the concentrate as unburst bubbles), has been shown to be linked to flotation separation performance, with stable froths yielding improved mineral recoveries. While it is widely acknowledged that there is an optimum particle size range for collection of particles in the pulp phase, the role of particle size on the measured air recovery and the resulting link to changes in flotation performance is less well understood. This is related to the difficulty in separating particle size and liberation effects.In this work, the effects of particle size distribution on air recovery are studied in a single species (silica) system using a continuous steady-state laboratory flotation cell. This allows an investigation into the effects of particle size distribution only on froth stability, using solids content and solids recovery as indicators of flotation performance. It is shown that, as the cell air rate is increased, the air recovery of the silica system passes through a peak, exhibiting the same froth behaviour as measured industrially. The air recovery profiles of systems with three different particle size distributions (d80 of 89.6, 103.5 and 157.1 m) are compared. The results show that, at lower air rates, the intermediate particle size distribution (103.5 m) yields the most stable froth, while at higher air rates, the finest particles (89.6 m) result in higher air recoveries. This is subsequently linked to changes in flotation performance. The results presented here highlight, for the first time, the link between particle size distribution in flotation feeds, air recovery and flotation performance. The results demonstrate that there is an optimal air rate for each particle size distribution, therefore changes in particle size distribution in the feed to flotation cells require a change in air rate in order to maximise mineral recovery.

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Section: Introductionmentioning

confidence: 99%

The effect of particle size distribution on froth stability in flotation

Norori-McCormac

Brito-Parada

Hadler

et al. 2017

Separation and Purification Technology

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“…This change appears to be consistent with the observation by Yianatos et al (2009) that gas holdup increases with decreasing bubble size in the region below the interface. As shown in Figure 6-3, the variation in liquid holdup caused by Dowfroth 250 was greater than that by MIBC.…”

Section: Liquid Velocity At the Interfacesupporting

confidence: 92%

“…Ideally, in a flotation cell, hydrophobic valuable mineral particles collide with air bubbles and form particle-bubble aggregates moving upwards against gravity to the froth from the pulp phase while hydrophilic gangue mineral particles report to the tailings (Yianatos et al, 2009).…”

Section: Problem Statementmentioning

confidence: 99%

“…Solids percentage in the upper regions of the pulp has a marked effect on the entrainment recovery (Johnson, 2005;Zheng et al, 2006b;Yianatos et al, 2009). In the literature, the recovery of gangue minerals by entrainment is often only related to the water recovery and the degree of entrainment (without a pulp classification effect) because all the mineral particles are perfectly dispersed and mixed in the pulp phase in the small sized cells in which the testing has been performed.…”

Section: Solids Percentage In the Pulpmentioning

confidence: 99%

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Entrainment of fine particles in froth flotation

Wang¹

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Entrainment has become a significant issue nowadays with fine grinding being used to liberate valuable minerals from low grade and complex ores to increase "true flotation". Entrainment results in large amounts of fine gangue materials reporting to flotation concentrates along with recovered valuable minerals and reduces the final product quality. In froth flotation, entrainment is the dominant recovery mechanism for fine gangue mineral particles, and it is influenced by a number of factors in both the pulp and froth phase, including particle properties (e.g. particle size and density) and flotation operational variables (e.g. gas flowrate, froth depth, impeller speed and reagent dosage).A number of models incorporating different factors have been developed to estimate entrainment recovery. Most of these models relate entrainment recovery to two parameters: the water recovery to concentrate, and the degree of entrainment, a classification factor to account for the degree of drainage of entrained particles with respect to the water in the pulp and froth phases of a flotation cell. However, there are still significant barriers to be overcome before they can be applied for routine estimation of entrainment in industrial applications. There is no consensus as to the variables which significantly affect the entrainment process and should therefore be included in the model as well as to the mechanisms involved.This thesis investigated the effect of flotation operational factors and particle properties on the entrainment parameters (i.e. degree of entrainment and water recovery) and the mechanisms underpinning the observed effects. The objective of the thesis was to develop a comprehensive understanding of the key operating conditions and particle attributes influencing the entrainment of gangue minerals in flotation, which should enable the development of a more sophisticated predictive entrainment model by more accurately predicting the degree of entrainment and water recovery.A two level factorial experimental program was adopted to investigate the effect of impeller speed, gas flowrate, froth height and specific gravity of gangue minerals on the degree of entrainment.Batch flotation experiments were performed in a 3.5 L conventional Agitair flotation cell using a feed which was a mixture of liberated chalcopyrite and one of two liberated gangue minerals, quartz and hematite. Results show that there was no direct correlation between the degree of entrainment and water recovery, indicating that the key drivers of water recovery were not the same as those that affected the degree of entrainment.ii The degree of entrainment was significantly influenced by particle size, particle density, frother and the interaction between gas flowrate and froth height. The mechanisms underpinning the effect of these significant influencing factors were investigated. Results suggest that the classification of gangue mineral particles mainly occurs at the pulp/froth interface region. Whether a particle moves upward into the frot...

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“…While true flotation is a chemically selective process based on hydrophobicity (Yianatos et al, 2009), entrainment is the recovery of hydrophilic gangue in the concentrate reducing the quality of the final products (Stewart, 2010). This study of entrainment is quite significant in this work as there are two major phases which are the active pyrite and passive pyrite with significantly different chemical and physical properties.…”

Section: Water Vs Solids Recoverymentioning

confidence: 99%

Differential oxidation of iron sulfides to modify the Au:S ratio in the flotation concentrate product at Lihir

John¹

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Sulfide associated refractory gold ores hold a majority of the gold within the pyrite, which has several forms. The high proportion of the gold atomically dispersed in the pyrite has been confirmed by various mineralogy techniques such as laser ablation analysis, optical microscopy, scanning electron microscopy and secondary ion mass spectrometry. Different types of pyrite exist within a refractory ore body and certain types possess a relative abundance of gold compared to other forms.The low gold pyrite influences the rate at which the concentrate can be processed by any particular route. If the different types of pyrite could be separated by flotation, then the gold grade of the final concentrate can be improved and the invisible gold could be recovered by downstream processing. This separation of low gold pyrite from the gold-rich pyrite would increase the gold:sulfur ratio (Au:S ratio) to the autoclave feed, thereby maximising the autoclave throughput and gold production per tonne.Different methods of extraction such as chemical oxidation, thermal oxidation and biological oxidation liberate gold from refractory ores. However, such oxidation methods have not been reported yet to be successful to allow separation of the low gold pyrite from the gold-rich pyrite and modify the Au:S ratio of a pyrite concentrate. This project is an attempt to develop a hydrometallurgical framework to modify the flotation response of gold-rich pyrite and low gold pyrite so that the Au:S ratio of the final flotation concentrate can be upgraded.ii

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Direct measurement of entrainment in large flotation cells

Cited by 33 publications

References 9 publications

The effect of particle size distribution on froth stability in flotation

The effect of particle size distribution on froth stability in flotation

Entrainment of fine particles in froth flotation

Differential oxidation of iron sulfides to modify the Au:S ratio in the flotation concentrate product at Lihir

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