Ultrasonic flow measurement methods applicable to wet low intensity magnetic separation

Abstract: In this project the internal material transport processes of wet low-intensity magnetic separation (LIMS) is studied. The aim is to use results from experiments combined with published results to create a base for further research and development. During the initial work, presented here, the focus has been to develop an experimental platform and verify that ultrasound is a viable tool for flow measurement in suspensions with solids concentrations realistic for wet magnetic separation processes. The experiments have been carried out in a purpose built flow cell equipped with ultrasonic transducers and supported by a pump, mixer and necessary data accusation electronics. In the first conference paper, ultrasonic velocity profiling is used to estimate flow velocity profiles, and initial results are presented. When applied to flows of mineral suspensions of high solids concentration, similar to those in wet LIMS, the method is unique in combining:' Non-intrusive measurements.' Operation by a single transducer element.' Relatively good spatial resolution.' Operation in opaque suspensions.' Fast sampling rate.In a second conference paper the signal processing behind the measurement method is investigated more thoroughly and focus is on robust profile estimation. The connection between solids concentration, ultrasonic transducer centre frequency and penetration depth is also investigated. In a publication the measurements are put in relation to the application of interest. It is shown that the methods are generally applicable and can be used in situations where variations in suspension flow velocity through narrow geometries are of interest.The novelty shown is that it is possible to measure flow velocity profiles through suspensions carrying at least 10 vol% solids. For solids concentrations of 5 vol% or less it is possible to get a velocity profile through at least 50 mm of suspension. Results from measurements in suspensions of such high solids concentration combined with such long penetration depth have not been published before. The measurement method has gained attention from industry since it is generally applicable to narrow channel flows reachable from only one access point.