The “virtuous cycle” has been conceived as a tool to assist thinking around the opportunities to reject gangue or recover mineral at optimum crush/grind size. The aim of this model is to maximise throughput and minimise power consumption. Ideally particles are rejected or recovered at liberation size. This process allows for a smaller high-grade concentrate stream to be created which can then be treated intensively for recovery. Mineral or gangue can be rejected based on size (screening), density (gravity separation), surface chemistry (flotation) or magnetic properties.
To optimise the application of this cycle using continuous gravity in the separating step, Gekko developed the continuous gravity recovery (CGR) laboratory test work protocol. CGR protocols are an alternative to the standard batch gravity recovery (GRG) test work program offered by many independent laboratories.
GRG tests are typically used to determine batch centrifugal concentrator (BCC) recovery in a milling circuit; this produces low mass yield concentrates. BCC units are almost exclusively used in gold applications, whereas the CGR test and continuous concentrators such as the InLine Pressure Jig (IPJ) can be used for a variety of valuable minerals and at coarser size ranges and larger mass pulls.
Determining the recovery of minerals at their liberation size, grade recovery relationships, size recovery relationships, as well as recovery of gold and silver through intensive leach work, have formed part of Gekko’s critical areas of specialty.
Continuous Gravity Recovery
CGR test work provides an improved and more accurate understanding of an ore’s response to gravity separation devices by plotting the recovery against mass yield. Over the past decade Gekko’s Technical Team, led by Technical Director Sandy Gray and Process Engineering Manager (previously R&D Manager) Tim Hughes, have researched and developed protocols to replicate the continuous gravity recovery of heavies and lights at their liberation size in mineral processing circuits. This has been an important development in assessing the performance opportunity of Gekko’s flow sheet concepts and equipment choices in processing plants.
CGR test work programs that are designed to simulate single pass or recirculating load circuit designs.
CGR single pass test work flow sheet
The single pass test protocol was developed to simulate the performances of Gekko’s IPJ in crushing and grinding circuits. Test work of this type is conducted on size fractions from 600 μm to a top crush size of 12mm. The CGR test uses dense media separation (Gekko’s Viking Cone and/or cyclones) for size fractions above 1.2mm and tabling for size fractions at less than 1.2mm.
The heavies are collected at different mass yields and the recovery of valuable minerals is determined. From the resulting curve it is possible to determine the optimum mass yield; to recover or reject the heavies or lights.
CGR progressive grind for recirculating loads
Where the IPJ is to be installed in a crushing or grinding circulating load, the test is modified so that heavies are removed at the coarser size as it liberates. The lights from the test are then passed over the table again at finer crush or grind sizes to replicate the environment experienced in circulating loads.
Both these test work programs are becoming increasingly popular at Gekko’s metallurgical laboratory as clients focus on strategies to reject gangue or pre-concentrate their target mineral in order to reduce capital, energy consumption and operating costs.