A novel approach to measure froth rheology in flotation

Abstract

The current study involves a novel approach to measure froth rheology in-situ using vane. The results showed that the horizontal flow of froth towards the flotation launder interferes with the rheology measurement. A tube encircling the vane was used to minimize the effects of the horizontal flow. In order to convert the rheology raw data to rheograms, shear stress is only a function of the vane geometry and the torque values. However, it was shown that calculation of the shear rate from the vane speed depends on whether froth is fully or partially sheared.The froth characterised in this study exhibited a pseudo-plastic nature with a minor yield stress using Casson model. Therefore, froth viscosity which potentially affects froth transportation is not constant throughout the whole froth phase and it depends on the local shear rate. The suitability of the vane system to measure rheology of fluids with low shear stress was examined using a Newtonian silicone oil. It was found that the vane head should not be run in speeds above a certain range which needs to be determined. Measurements above such a speed range may not be accurate.