Froth flotation apparatus

The froth flotation apparatus includes a gas bubble-particle contact unit including a mixing structure for breaking a gas into fine bubbles,such as a packed tower packing or mechanical agitator, and a separate phase separation unit. A conditioned aqueous pulp containing a mixture of hydrophobic and hydrophilic particles and a substantially inert gas, such as air, are introduced into and combined in one end of the contact unit and subsequently flow concurrently through the mixing structure, such that the gas is broken into fine bubbles which intimately contact and become attached to the hydro- phobic particles. The resulting gas bubble-particle mixture is introduced into the phase separation unit which is operated under substantially quiescent conditions. A concentrate fraction containing primarily hydrophobic particles and a tailing containing primarily hydrophilic particles are discharged from the upper and lower portions of the phase separation unit, respectively. In one embodiment, the phase separation unit comprises a vertical column including one or more slowly rotating paddles in the froth zone to produce a froth having a substantially uniform buoyancy. In another embodiment, the phase separation unit comprises an elongated, generally horizontal tank and includes a skimming assembly for moving froth toward the concentrate fraction outlet.