A Revolution in the Screening Process
There are predominantly two counter current methods employed in industry to absorb leached gold from a pulp stream onto activated carbon. These methods are Carbon-in-Leach (CIL) and Carbon-in-Pulp (CIP). Mineral Processing Separating (MPS) and Mineral Processing Separating Pumping (MPS(P)) Interstage Screen technology are today considered the benchmark in interstage screening.
A counter current method involves pulp flowing down a series of tanks with a reduced flow pumping carbon up the series of tanks to maximize gold on carbon loadings and minimize gold losses to tails.
The interstage screens prevents carbon going down the circuit.
MPS and MPS(P) Interstage Screens are semi-submerged top exit type screens. The wedge wire screen is submerged under the pulp operating level allowing pulp to flow through the wedge wire screen apertures while carbon is retained. The pulp flows upwards through the inside of the screen and exits via a launder interface above the wedge wire screen and volute interface.
The MPS Interstage Screens are typically utilised in circuits having the tanks arranged in a cascade configuration differential i.e. cascade arrangement. This height differential overcomes the pressure drop around the wedge wire screen which in turn induces pulp flow through the plant.
The MPS Interstage Screen operates with a higher pulp level in the tank relative to the pulp at the screen’s exit launder.
The MPS(P) Interstage Screens are installed in circuits having the tanks and operating pulp levels at the same horizontal elevation. The pressure drop around the wedge wire screen is overcome via an up-pumping impeller which is incorporated into the MPS(P) Interstage Screen.
The pumping action of the impeller induces sufficient head and pulp velocity to transport the pulp to the next adsorption tank in the circuit. The MPS(P) Interstage Screen operates with the pulp in the tank at a lower level relative to the pulp level at the screen’s exit launder.
The advantage of using MPS(P) type Interstage Screens on circuits having the same horizontal elevation tank arrangement is that civil construction requirements are notably reduced when compared to a conventional cascade circuit.
For both the MPS and MPS(P) Interstage Screens the drive and screen form an integrated unit that can easily be removed for cleaning and routine maintenance procedures.