The hydrodynamics of fast flotation

The recovery of hydrophobic particles from low grade, dilute, solids streams frequently requires a significant number of large flotation cells to account for a low flotation rate constant. However, this approach is often considered uneconomical due to the substantial capital investment and energy consumption. Hence, valuable particles are subsequently discharged to tailings. Key parameters governing the kinetics of flotation include the bubble diameter and the shear rate, while the extraction rate is limited by the bubble surface flux, S_b = 6j_g/D_b. However, for a given bubble diameter, D_b, the imposed gas flux, j_g, is constrained in conventional flotation by the need to operate with a distinct froth and bubbly-pulp zone to ensure effective separation. An excessive j_g will result in flooding and ineffective separation as the overflow begins to resemble the underflow. The bubble surface flux, S_b, is limited to 30 to 60 s^-1 in conventional flotation [1]. This study is concerned with enhancing the kinetics of flotation by accommodating extreme feed and gas fluxes. Extreme bubble surface fluxes, up to 600 s^-1, were produced. This was achieved by incorporating an arrangement of parallel inclined channels below the main vertical chamber. This novel arrangement enhanced the bubble-liquid segregation, preventing the entrainment of bubbles to the underflow.