Measuring gas dispersion parameters: Selection of sampling points

•Parabolic air profiles by measuring local radial gas velocity in flotation cells.•Sample point representing average superficial gas velocity in flotation cells.•Relationship of parabolic air profiles and frother concentration in flotation cells.

Bubble surface area flux has proven to be a key operational variable in flotation machines not only for diagnosis but also for optimization purposes. It is calculated as a combination of two gas dispersion properties, superficial gas velocity and bubble Sauter mean diameter. Since gas is not necessarily distributed evenly over the cross sectional area of a cell the sampling point where gas dispersion properties are measured must be carefully selected. This article illustrates that a radial parabolic gas velocity profile exists in mechanical cells, in some cases with significant variation in gas velocity as a function of radial distance from the center. An optimal sampling location for single point gas dispersion measurements in mechanical flotation machines is proposed.