Process measurements in flotation columns using electrical conductivity

Uribe-Salas, Alejandro; Uribe-Salas, Alejandro

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Process measurements in flotation columns using electrical conductivity

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Uribe-Salas, Alejandro

Abstract

English

Techniques based on electrical conductivity to estimate interface level, gas holdup and bias rate in flotation columns were developed. A conductivity probe and associated data acquisition system for locating the froth/collection zone interface in flotation columns were developed and tested. The level detection technique is based on the collection of a conductance profile around the interface and on the location of the position at which a sharp change in conductance occurs. Such a change in conductance across the interface is caused by the difference in the effective conductivity of the froth and collection zone, primarily due to their difference in gas holdup. A conductivity cell to measure the effective conductivity of water-air, water-mineral, and water-mineral-air systems was developed. The cell consisted of two grid-electrodes covering the entire cross-sectional area of the cylinder containing the two or three phase system. Such an arrangement allowed the free movement of the phases and provided conditions for uniform potential and current (electrical) fields. It was found that Maxwell's model (1892) predicted the holdups of the non-conductive material reasonably well from the conductivity measurements. Conditions encountered in industrial flotation columns allowed the use of conductivity to trace the flows of feed water and wash water across the interface, and therefore, to determine the bias rate. Alternative parameters to bias rate as measures of metallurgy such as fraction of feed water in the overflow water (called here feed water entrainment), feed water recovery, and conductance profiles, were explored.

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