National mineral research organisation Mintek will be providing new services to the gold mining and exploration sector.

The organisation announced on March 7 that it would be providing oxygen demand and Knelson extended gravity recoverable gold (EGRG) testing services.

To facilitate these new services, Mintek has acquired an MD3 Knelson concentrator, which is a type of gravity concentration apparatus used for the recovery of fine particles of free gold without the need for gold cyanidation for recovery.

“We have received a number of requests for Knelson gravity work, as well as oxygen demand work, highlighting the need for these services,” said Mintek hydrometallurgy senior engineer Bongiwe Nkabane during a presentation at Mintek's headquarters in Johannesburg, which Mining Weekly attended.

She said Mintek was at the development stage of conducting testing and validation of the Knelson EGRG.

She explained that the objective of the testing was to quantify the amount of EGRG that can be recovered from the ore.

Nkabane said the setup for the Knelson EGRG circuit consisted of a rod mill, a screen and the Knelson concentrator. The test was being carried out in three concentration stages, where each stage was preceded by grinding to a specific grind size. The grind size was progressively reduced as the stages progressed.

The concentrate of each stage was then analysed for gold and particle size distribution. The final tailings were also analysed for gold.

“The benefits compared to the gravity amenability testing equipment that we have is that the progressive grinding minimises the over-grinding of particles and smearing of coarse precious metals. Moreover, the liberation characteristics of the EGRG can be obtained from the test,” she explained.

She said the data acquired from the testing could be used to model, upscale and predict the performance of gravity circuits.

Nkabane requested gold mining and exploration companies to contribute further to the test work by contributing more samples for testing.

OXYGEN DEMAND TESTING

Mintek has also acquired oxygen demand testing equipment with the aim of quantifying ore oxygen requirements.

Nkabane said the sizing of oxygen plants for gold cyanidation plants remained problematic owing to the poor quantification of ore oxygen requirements.

To address this problem, Mintek entered into a service agreement with gas services and equipment provider Air Liquide to house oxygen demand laboratory equipment to be able to provide oxygen demand testing services to the industry.

“The main information acquired from this test is the oxygen uptake rate and the oxygen uptake efficiency. In addition to this, you can get the gold extraction efficiency, the gold dissolution rate, as well as the lime consumption,” Nkabane explained.

Currently, Mintek is busy with training personnel in collaboration with Air Liquide to use the equipment and interpret its results accurately. The commissioning and testing of the equipment still needs to be carried out.

Nkabane extended a plea to the gold mining and exploration industry to provide samples and plant data to help expedite the test work, which she said would begin within the next three months.

“To make this service available we need cooperation between the mining houses and Mintek during testing and validation,” she said.

Mintek expects both the Knelson EGRG and oxygen demand testing services will be commercially available to the industry within six months.