Abstract

Gas dispersion properties have proven to be key variables of the flotation process. Among them, bubble surface area flux (BSAF or Sb) has been reported to linearly correlate with the flotation rate constant; therefore, it is a potential manipulated variable to achieve a desired metallurgical performance. BSAF can be represented as a combination of two other gas dispersion properties: superficial gas velocity and Sauter bubble mean diameter; thus, controlling Sb implies controlling bubble size and superficial gas velocity. This work focuses on the control of the Sauter mean bubble diameter. To improve BSAF controllability, a so-called frit-and-sleeve sparger device was installed to regulate bubble size independently from superficial gas velocity. For control purposes, Sauter bubble mean diameter was indirectly calculated from the bubble size distribution, estimated by using a Gaussian mixture model. An IMC controller based on a Wiener model was implemented in a laboratory flotation column. Tracking performance and rejection of gas velocity and unmeasured frother concentration variations were then evaluated.