Gas holdup and bubble flow transition characteristics in column flotation process determined by capacitive signals measurement

A non-invasive and non-intrusive monitoring techniques are developed based on the signal capacitance method to observe column flotation performance. In general, gas holdup and bubble flow characteristics are the essential parameters that affect flotation performance. This study investigates and verifies the effects of frother dosage and solid percent on the gas holdup and bubble flow transition characteristic by analyzing the capacitance signals. Experiments were conducted in two- and three-phase systems with a variation of frother addition and solid concentration in the range of 1–5 cm/s of superficial gas velocities. The results showed that the capacitance signals method could characterize the bubble flow and its transition in column flotation, which consists of discrete bubbly, cap-discrete bubbly, and slug flow. The bubble flow transition in the three-phase system occurred at slightly lower superficial gas velocity and gas holdup than in the two-phase system, as measured by the deviation of gas holdup analysis. Higher frother addition and the higher solid concentration will decrease the gas holdup of bubble flow transition. In this study, the flow transition occurred between the superficial gas velocity of 2.5–3.3 cm/s for 2 phase and 2.5–3 cm/s for 3 phase systems.