The continuous concentrators are defined as those units that receive continuous feed and produce continuous tailing and concentrate streams. The use of continuous gravity concentrators in the gold industry has been limited in the last 20 years because the semi-continuous concentrators have been dominant in recovery of GRG from grinding circuits. However, continuous non-centrifuge concentrators such as the InLine Pressure Jig, shaking tables, conventional jigs, Reichert Cones, and spirals have been utilized.
In most instances, these units have been employed to recover GRG. Reichert Cones are used as pre-concentrators for semi-continuous units or for spirals, whereas duplex jigs have largely been replaced by semi-continuous units in North America, except for alluvial applications. Duplex jig capacity is difficult to assess, but Richardson reports capacities of up to 280m3/h (380 cu. yards/h) for a 5.49m (18 ft) diameter circular jig, compared to 37m3/h (49 cu. yards/h) for a 4-cell duplex jig, each cell 1.14m2 (3.5 sq. ft) in surface.
The newest of the non-centrifuge continuous units is the InLine Pressure Jig, which has been utilized in the recovery of GRG and gold carriers. This unit has the advantage of being able to accept a wide range of feed size while at the same time adding very low levels of dilution water to the grinding circuit. Also, a true saw tooth stroke is generated by a hydraulic drive system that enables control of all critical pulse parameters. The unit is
capable of recovering finer mineral than conventional jigs at high throughput rates per screen surface area.
The complex ores, as defined by the poor recovery in a conventional cyanide leach circuit, tend to have a larger component of the gold associated with the sulfide minerals or gold carriers. Higher yields are therefore needed.
The use of continuous gravity concentration in the grinding circuit for the purposes of sulfide and gold carrier recovery is increasing. Gravity removal of gold and gold carriers from the grinding circuit offers many benefits over flash flotation, such as reduced operating cost and much coarser recovery. The maximum recovery size limitation on the flash circuit can be as low as 150 μm. For many ores it can be critical to recover the GRG and gold carriers from the grinding circuit before it gets to this size range. As well, flotation chemicals create surface chemistry issues both with gold particles and activated carbon. As a result, gravity recovery is often preferred to flash flotation, or operated co-currently.