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The sparger type as well as the frother dosage have a fundamental role on the bubble size control with influences on the kinetic flotation and metallurgical performance (recovery and grade). This work shows online evaluation studies of the the bubble size distribution generated by a porous tube sparger and a micro-venturi coupled in an automatized mini pilot flotation column. The effects of the frother (DF250 - propylene glycol methyl ether) dosage and the air flow rate on the bubble size and holdup were evaluated. The mean bubble diameter was strongly influenced by the frother dosage for both spargers; nevertheless, the micro-venturi was more efficient than the porous tube, because it was able to disperse the air more finely and with smaller dosages of frother. The smaller mean diameters obtained, according to the applied experimental conditions, were of 1.25 mm (154.8 mg/L of DF250) for the porous tube and 0.45 mm (44.2 mg/L of DF250) for the micro-venturi. [ABSTRACT FROM AUTHOR]