The Jameson Cell consistently produces fine bubbles and intense mixing between air and slurry. This means fast, efficient flotation. While the principle of using air bubbles to recover particles is the basis of the technology, it is the way air bubbles are generated and how the bubbles and particles interact that make Jameson Cells unique.
In the Jameson Cell, particle-bubble contact takes place in the downcomer. The tank's role is froth-pulp separation and may incorporate froth washing to assist in obtaining product grade. With no agitators, blowers or compressors Jameson Cell installation is simple and operation is extremely energy efficient.
As the energy for flotation is delivered by a conventional pump power consumption is significantly lower than the equivalent mechanical or column flotation cell.
Optimal Jameson Cell performance is maintained by delivering a constant volumetric flowrate of pulp to each downcomer. While operating plants experience fluctuating process flows, the Jameson Cell is equipped with a tailings recycle system that automatically compensates for feed variations.
In addition to maintaining consistent and optimal downcomer operation, the tailings recycle improves metallurgical performance by giving particles multiple 'passes' through the downcomer contacting zone. The Jameson Cell's ability to provide better selectivity and to control entrainment means product grade is not affected.
A Jameson Cell consists of three main zones: the downcomer, the tank pulp zone, and the tank froth zone.
The Downcomer is the heart of the Jameson Cell where intense contact between air bubbles and particles occurs. Feed is pumped into the downcomer through the slurry lens orifice creating a high-pressure jet. The jet of liquid shears and entrains air from the atmosphere. Removal of air inside the downcomer creates a vacuum, causing a liquid column to be drawn up inside the downcomer.
The jet plunges into the liquid column where the kinetic energy of impact breaks the air into fine bubbles which collide with the particles. The very high interfacial surface area and intense mixing results in rapid particle attachment to the air bubbles, and high cell carrying capacities.
The Tank Pulp Zone is where mineral laden bubbles disengage from the pulp. The design velocities and operating density in this zone keep particles in suspension without the need for mechanical agitation. Due to the rapid kinetics and separate contact zone in the downcomer, the tank is not sized for residence time therefore tank volumes are much smaller than equivalent mechanical or column cells. Jameson Cells are contact dependent, not residence time dependent.
In the Tank Froth Zone the grade of the concentrate is controlled by froth drainage and froth washing. Cells are designed to ensure an efficient, quiescent zone that maximises froth recovery. Froth travel distance and concentrate lip loadings are integral to the tank design.
The downcomer is where bubble-particle collision, attachment and collection occur. The different hydrodynamic regions of the downcomer are the Free Jet, Induction Trumpet, Plunging Jet, Mixing Zone and Pipe Flow Zone.
- Free Jet: Slurry passing through the slurry lens orifice under pressure creates the Free Jet which shears the surrounding air and entrains it into the slurry.
- Induction Trumpet: The Free Jet impinges on the slurry in the downcomer. The impact creates a depression on the liquid surface and results in air being channelled into the area at the base of the Free Jet.
- Plunging Jet: High shear in the jet breaks the entrained air into a multitude of very fine bubbles (0.3 to 0.5 mm in diameter) which are carried downwards in the downcomer.
- Mixing Zone: The Plunging Jet transfers momentum to the surrounding mixture, creating recirculating eddies of aerated liquid for intense bubble-particle collision and attachment.
- Pipe Flow Zone: Beneath the Mixing Zone, a region of uniform multiphase flow exists. The downward liquid velocity counteracts the upward flow of mineral laden air bubbles. The air bubbles and particles pack together to form a downward moving expanded bubble-particle bed. The dense mixture of bubbles and pulp discharge at the base of the downcomer and enters the tank pulp zone where the mineral laden bubbles disengage from the pulp.