Evaluation of the applicability of ultrasonic velocity profiling in conditions related to wet low intensity magnetic separation

• Method proposed for internal measurements in wet low-intensity magnetic separators.
• Experimental measurements under controlled conditions using ultrasonic velocity profiling.
• Measurements in magnetite suspensions up to 9% solids by volume (36% by weight).
• Flow profiles validated against computational fluid dynamics simulation.
• Possible to measure mineral suspension flow in narrow channels.

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 velocity varies with penetration depth is presented. A measurement depth of just a couple of centimetres would greatly improve the 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 (50 × 75 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 (20% and 36% by weight). Even at 9 vol% solids it is possible to reach a penetration depth of more than 25 mm.

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