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In mineral processing, material transport is commonly monitored between unit operations; flow rate, solids concentration, and particle size distribution of suspension flow in pipes are measured online using standard equipment. In many situations this information could be complemented by measurements inside the process equipment. In this work a wet Low-Intensity Magnetic Separator, where no means for internal flow measurements exist today, is used to evaluate a proof of concept for an ultrasound-based measurement method. The method is utilized for direct measurements of internal suspension flows in a bench scale unit of the counter-current type. Two ultrasound transducers (2.25 MHz) form an Acoustic Backscatter System capable of monitoring flow characteristics in several positions inside the separator.

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The internal material transport and selection processes of the wet low-intensity magnetic separators (LIMS) are poorly understood; this calls for improved measurement techniques. In this work an ultrasonic velocity profiling (UVP) technique for measuring how material flow speed varies with penetration depth is presented. A measurement depth of just a couple of centimetres would greatly improve our understanding of the separation process in a LIMS.When applied to flows of mineral suspensions with high volumetric solids concentration, similar to those in the separators, UVP is unique in combining:Non-intrusive measurements.Operates using just one sensor element (transducer).Relatively good spatial resolution. Penetrates opaque suspensions.Fast sampling rate.Here, flows are studied in a rectangular duct (50x75 mm). Using magnetite suspensions, measurement through the whole depth of 50 mm is made with good accuracy. Velocity profiles are presented for solids concentrations of 5 and 9% solids by volume. Even at 9 vol% solids it is possible to reach a penetration depth of more than 25 mm.

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