Method and apparatus for flotation in a fluidized bed
Separation of hydrophobic particles from a mixture of particles in a fluid is performed by providing a fluidized bed as a relatively non-turbulent contacting mechanism in a flotation cell incorporating a settling chamber located immediately above the fluidized bed. Hydrophobic particles attach to bubbles in the fluidized bed and rise to the interface with the settling chamber where non-hydrophobic particles flow over the lip of an internal launder and are removed as tailings at. The hydrophobic particles attached to bubbles float upwardly in the relatively placid settling chamber where unwanted gangue can fall back to interface. The bubbles form a froth layer at the upper surface of the settling chamber, and flow over the launder lip carrying the hydrophobic particles. An operation of the apparatus is kept stable by recirculating fluid from the settling chamber via pip and pump to mix with new feed entering at duct.
1. A method of separating selected particles from a mixture of particles in a fluid, said method including the steps of:
generating a fluidized bed by providing an upward flow of liquid in a generally tubular flotation cell containing particles, such that the drag force on the particles created by the upward flow is sufficient to support the weight of particles in the cell;
providing bubbles in said fluidized bed;
feeding the mixture of particles and fluid upwardly into the fluidized bed from a location beneath the fluidized bed;
allowing the selected particles to attach to bubbles within the fluidized bed and rise to the top of the fluidized bed;
allowing bubbles with selected particles attached to rise above the fluidized bed into a settling chamber while removing tailings from the top of the fluidized bed;
forming a froth layer of bubbles and attached selected particles at the top of the settling chamber;
controlling the depth of the froth layer; and
allowing selected particles with bubbles attached to flow from the froth layer over a lip of the flotation cell into a launder to form flotation product.
2. A method as claimed in claim 1 , wherein the fluidized bed is arranged and controlled such that the selected particles are hydrophobic and the bubbles with selected particles attached reach the top of the fluidized bed in a gentle non-turbulent manner.
3. A method as claimed in claim 1 , wherein the other particles include particles that rise into the settling chamber and fall back to the fluidized bed.
4. A method as claimed in claim 1 , wherein recycle fluid is removed from the settling chamber and pumped into the feed of mixed particles and fluid by a recycle pump providing additional fluid to fluidize the bed.
5. A method as claimed in claim 4 , wherein the bubbles are formed in an aerator downstream of the recycle pump.