Article
Studies on Impeller Type, Impeller Speed and Air Flow Rate in an Industrial Scale Flotation Cell
Dept. of Chemical Engineering, University of Cape Town, South Africa
Minerals Engineering (Impact Factor: 1.6). 04/1997; 10(4):367379. DOI: 10.1016/S08926875(97)000149 ABSTRACT
The metallurgical performance of a 2.8m3 portable industrial scale flotation cell was measured when treating zinc cleaner feed at Hellyer concentrator in Tasmania, Australia. The cell was fitted in turn with four different impellerstator systems and operated over a wide range of air flow rates and impeller speeds. Bubble size, gas holdup and superficial gas velocity were measured at each of 64 different operating conditions along with the metallurgical performance of the cell. When metallurgical performance was expressed in terms of a kinetic constant, it was found that neither bubble size nor gas holdup nor superficial gas velocity could be related to flotation rate individually; but when taken together, they determine the bubble surface area flux in the cell, which could be related to flotation rate extremely well. A linear relationship between flotation rate and bubble surface area flux was found for all four impellers investigated: the slope of the line was independent of the type of impeller used. The linear relationship was verified for different size fractions of the ore: the slope of the straight line was different for different size fractions, values being greater for the smaller size particles. The relationship was also independently confirmed at another zinc cleaner operation. This finding has potential practical application in flotation plant modelling, design and optimisation.

 ". PLS regression for hydrodynamic variables using the dataset from Gorain et al. (1997). 4 A. Vazirizadeh et al. / Minerals Engineering xxx (2015) xxx–xxx Please cite this article in press as: Vazirizadeh, A., et al. "
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ABSTRACT: The estimation of the flotation rate constant is generally considered difficult because of the number of variables – not always measurable – determining its value. Among them, the particle size distribution and hydrodynamic characteristics are considered key elements. Part 1 of this paper introduced the interfacial area of bubbles (Ib) as a hydrodynamic variable providing more information about the size distribution than the bubble surface area flux (Sb). Fundamental expressions were proposed to characterize Ib using the population mean and standard deviation. Experimental results indicated that for lognormal bubble size distributions, Ib correlates very well with the gas holdup and d32. Part 2 investigates the correlation between the flotation rate constant and particle size as well as given hydrodynamic variables using a Projection to Latent Structures (PLS) analysis. The tests were conducted under ‘ideal’ conditions (i.e. shallow froth, low mineral concentration and pure mineral particles). Results suggest that for the fine particle sizes, the bubble surface area flux (Sb) should be considered for the kinetic constant modeling. For coarser particle, the gas holdup (εg) is the determining parameter. In practice though, the particle size distribution often lies between these two extreme cases, and can either span a very large range or contains intermediate size particles. In such cases, the interfacial area of bubbles (Ib) better correlates with the flotation kinetics. 
 "For example, for shallow froths the relationship was linear [23]. These authors found [23] [24] that b S (1/s) was strongly related with k (1/min) and that the relationship was linear, as represented by following equation: "
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ABSTRACT: Understanding the attachment micro process is a fundamental step toward predicting the rate constant of flotation kinetics. In this research, the effect of bubbleparticle attachment efficiency on kS b relationship was investigated under Yoon, Stokes and Potential conditions. Maximum Stokes attachment efficiency obtained was 55.9% with particle size of 37 µm, S b of 34.2 1/s and flotation rate of 1.65 1/min. Stokes attachment efficiency was less than Yoon efficiency and it seems to be a suitable equation for predicting attachment efficiency. Furthermore, three different models were obtained for estimating attachment efficiency usingkS b relationship. 
 "These characteristics are referred to as the machine gas dispersion properties, which include the following: bubble size (Sauter mean diameter, D 32 ), gas holdup (e g ), superficial gas velocity (J g ) and bubble surface area flux (S b ) (Gomez and Finch, 2007). Over the last decade, S b has proven to be a key operating variable being directly related to the flotation kinetic (rate) constant and consequently to flotation performance (Gorain et al., 1997; Hernandez et al., 2003). It is defined as the amount of available surface area for collecting hydrophobic particles per unit of time and effective machine crosssectional area. "
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ABSTRACT: Bubble surface area flux has proven to be a key operational variable in flotation machines not only for diagnosis but also for optimization purposes. It is calculated as a combination of two gas dispersion properties, superficial gas velocity and bubble Sauter mean diameter. Since gas is not necessarily distributed evenly over the cross sectional area of a cell the sampling point where gas dispersion properties are measured must be carefully selected. This article illustrates that a radial parabolic gas velocity profile exists in mechanical cells, in some cases with significant variation in gas velocity as a function of radial distance from the center. An optimal sampling location for single point gas dispersion measurements in mechanical flotation machines is proposed.
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