Determining the significance of flotation variables on froth rheology using a central composite rotatable design

• Froth viscosity is not constant in the froth phase and it depends on the shear rate.
• Froth phase shear rate is less than 4 s− 1, much lower than pulp phase shear rate.
• Froth apparent viscosity varies significantly with variation in flotation condition.

Froth performance in a flotation cell is expected to be affected by froth rheology due to change in the froth transportation rate. However, very little study has been performed to investigate how froth rheology responds to flotation variables. This paper presents an experimental program performed to study the effects of flotation variables (i.e. feed grade, feed particle size, froth height, superficial gas velocity and impeller speed) on the froth rheology. These conditions were varied using a central composite rotatable design (CCRD).Froth rheology was found to change significantly with a variation in flotation conditions and exhibited shear-thinning behaviour. Assuming the froth moving towards the flotation lip is an open channel flow, the shear rate in the froth was calculated to be less than 4 s− 1. Results of the CCRD experiments showed that the flotation variables have different effects on the froth rheology. The interactions between these flotation variables in determining froth rheology were also analysed. A shear rate specific empirical model was developed to relate froth rheology to the flotation variables and their interactions.

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