Studies on impeller type, impeller speed and air flow rate in an industrial scale flotation cell. Part 4: Effect of bubble surface area flux on flotation performance

Julius Kruttschnitt Mineral Research Centre, Isles Rd, Indooroopilly, Qld 4068, Australia; Dept. of Chemical Engineering, University of Cape Town, South Africa
Minerals Engineering (Impact Factor: 1.21). 01/1997; DOI: 10.1016/S0892-6875(97)00014-9

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 impeller-stator 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.

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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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    ABSTRACT: Adaptive neuro fuzzy inference system (ANFIS) procedure and regression methods were used to predict the Sauter mean bubble (bubble diameter) and surface area flux of the bubble in a flotation process. The operational conditions of flotation, impeller peripheral speed, superficial gas velocity, and weight percent solids were used as inputs of methods. By using the mentioned operational conditions, the non linear regression results showed that Sauter mean, and surface area flux of the bubble are predictable variables, where the coefficients of determination (R2) are 0.57 and 0.74, respectively. To increase the accuracy of prediction an ANFIS model with cluster radius of 0.4 was applied. ANFIS model was capable of estimating both Sauter mean, and surface area flux of the bubble, where in a testing stage, satisfactory correlations, R2 = 0.78, and 0.86, were achieved for Sauter mean, and surface area flux of bubble, respectively. Results show that the proposed ANFIS model can accurately estimate outputs and be used in order to predict the parameters without having to conduct the new experiments in a laboratory.
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