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Zhang W.,Chinalco China Copper Corporation Ltd | Zhang W.,McGill University | Nesset J.E.,McGill University | Finch J.A.,McGill University
Journal of Central South University | Year: 2014

This work aims to provide a relationship of how the key operational variables of frother type and impeller speed affect the size of bubble (D 32). The study was performed using pilot-scale equipment (0.8 m 3) that is up to two orders of magnitude larger than equipment used for studies performed to date by others, and incorporated the key process variables of frother type and impeller speed. The results show that each frother family exhibits a unique CCC95-HLB relationship dependent on n (number of C-atoms in alkyl group) and m (number of propylene oxide group). Empirical models were developed to predict CCC95 from HLB associated with other two parameters α and β. The impeller speed-bubble size tests show that D 32 is unaffected by increased impeller tip speed across the range of 4.6 to 9.2 m/s (representing the industrial operating range), although D 32 starts to increase below 4.6 m/s. The finding is valid for both coalescing and non-coalescing conditions. The results suggest that the bubble size and bubble size distribution (BSD) being created do not change with increasing impeller speed in the quiescent zone of the flotation. © 2014 Central South University Press and Springer-Verlag Berlin Heidelberg.


Zhang W.,Chinalco China Copper Corporation Ltd | Zhang W.,McGill University | Nesset J.E.,McGill University | Finch J.A.,McGill University
Journal of Central South University | Year: 2014

Effect of frothers in preventing bubble coalescence during flotation of minerals has long been investigated. To evaluate the performance of a frother, an apparatus to measure the bubble size is a basic necessity. McGill Bubble Size Analyzer (MBSA) or bubble viewer that has been developed and completed by McGill University's Mineral Processing Group during the last decade is a unique instrument to serve this purpose. Two parameters which are thought to influence the bubble size measurements by McGill bubble viewer include water quality and frother concentration in the chamber. Results show that there is no difference in Sauter mean (D 32) when tap or de-ionized water was used instead of process water. However, the frother concentration, in this research DowFroth 250 (DF250), inside the chamber exhibited a pronounced effect on bubble size. Frother concentration below a certain point can not prevent coalescence inside the chamber and therefore caution must be taken in plant applications. It was also noted that the frother concentration which has been so far practiced in plant measurements (CCC75-CCC95) is high enough to prevent coalescence with the bubble viewer. © 2014 Central South University Press and Springer-Verlag Berlin Heidelberg.


Zhang W.,Chinalco China Copper Corporation Ltd | Zhang W.,McGill University | Nesset J.E.,McGill University | Finch J.A.,McGill University
Journal of Central South University | Year: 2014

The specific results of the work investigating the effect of gas density and water temperature on bubble size were present. These were surrogate variables designed to investigate the effect of viscosity (varying water temperature) and altitude (varying gas density). The results show that there is a measurable but relatively small effect of gas density on bubble size. The D 32 is revealed to increase proportionally as (ρ 0/ρ g)0.132. The projected impact on flotation kinetics at 4500 m versus sea level is small, of the order of 0.5% recovery loss for a bank of eight flotation cells. The effect of water temperature (4-40 C) on bubble size is more significant than gas density. The relationship correlates with water viscosity values quite closely. A finding that D 32 increases proportionally as (μ/μ20) 0.776 highlights the importance of accounting for viscosity effects if, for example, large process temperature fluctuations or deviation from design/test conditions are expected. © 2014 Central South University Press and Springer-Verlag Berlin Heidelberg.


Zhang W.,Chinalco China Copper Corporation Ltd | Zhang W.,McGill University | Finch J.A.,McGill University
Journal of Central South University | Year: 2014

Froth flotation is a widely used process of particle separation exploiting differences in surface properties. It is important to point out that overall flotation performance (grade and recovery) is a consequence of the quality and quantity of the solid particles collected from the pulp phase, transported into the froth phase, and surviving as bubble-particle aggregates into the overflow. This work will focus on studying these phenomena and will incorporate the effects of particle hydrophobicities in the 3-phase system. Solids are classed as either hydrophilic non-sulphide gangue (e.g. silica, talc), hydrophilic sulphide (e.g. pyrite), or hydrophobic sulphide (e.g. sphalerite). Talc is a surface-active species of gangue that has been shown to behave differently from silica (frother adsorbs on the surface of talc particles). Both are common components of ores and will be studied in detail. The focus of this work is to investigate the role of solids on pulp hydrodynamics, froth bubble coalescence intensity, water overflow rate with solids present, and in particular, the interactions between solids, frother and gas on the gas dispersion parameters. The results show that in the pulp zone there is no effect of solids on bubble size and gas holdup; in the froth zone, although hydrophilic particles solely do not effect on the water overflow rate, hydrophobic particles produce higher intensity of rates on water overflow and bubble coalescence, and many be attributed to the water reattachment. © 2014 Central South University Press and Springer-Verlag Berlin Heidelberg.


Zhang W.,Chinalco China Copper Corporation Ltd | Zhang W.,McGill University
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2014

In operating flotation plants, the viscosity of the pulp can vary significantly. Consequently, the resulting impact on bubble size is of interest as many plants experience seasonal changes in water temperature, or particle size changes as ore hardness, mineralogy and throughput fluctuate. However, given its importance in flotation, there existed no mathematical relationship linking bubble size created in flotation machines to the key process variable of fluid viscosity. In this study, a program of investigation to develop such a model was utilizing a pilot-scale mechanical flotation machine, to investigate the effect of water viscosity due to temperature on bubble size distribution. The bubble sizes were determined using a specific bubble viewer and imaging technology. The temperature itself was varied as a method for introducing significant viscosity change. The viscosity-temperature effect introduced a correspondingly significant change in the water viscosity (1619 to 641 μPa·s). It is suggested that a considerably stronger relationship may exist, yielding D32 versus (μ/μ20)0.776, and hence viscosity becomes an important design consideration for plants operating where pulp temperature fluctuations, very small particles or high solid fractions are present. © 2014 The Nonferrous Metals Society of China.

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