Magnetic and sensor sorting solutions company Steinert has set up a new modular testing plant at Navachab gold mine, near Karibib, in Namibia. The company commissioned the plant last month, following the plant’s arrival on-site in September.

Steinert Southern Africa area manager John Knouwds explains that Navachab gold mine, which is owned by private equity firm QKR-Namibia, indicated its interest in doing testwork in 2019.

The mine commissioned a 200 t/h Steinert X-ray transmission sensor bulk sorting plant in March 2016, which has been in production, with “very satisfactory results”, Knouwds says.

“Since then, Steinert’s technology has taken a leap forward by offering multiple sensors on a single platform. This allows for higher classification abilities, higher processing capacities, higher recoveries and improved grades,” he explains.

The new on-site testing plant is a Steinert KSS XT CLI 100 combination unit, capable of handling a throughput of between 5 t/h and 100 t/h. This unit includes an X-ray transmission sensor, a colour sensor, a laser sensor and an induction sensor.

The unit was developed as a response to increasingly complex requirements in material separation, Knouwds says.

Inside the KSS unit, two optical sensors provide colour and three-dimensional (3D) shape information, while the inductive sensor detects metals. Differences in density are detected using X-ray transmission.

The combination of multi-sensory data collected for each object allows for a wide variety of tasks to be covered by one KSS sorting machine.

“The combination of sensors means that the KSS can be used as a standalone solution, but which is integrated into a processing concept, thereby significantly expanding the sorting depth even for smaller mass flows,” Knouwds says.

Moreover, the X-ray transmission and 3D shape information allow for an additional evaluation of object characteristics, making the system less sensitive to large differences in sortable material.

The modular structure of Steinert’s KSS unit also allows for various sensor configurations to be employed, depending on client requirements.

Further, the combination of 3D detection and induction sensors, compared with a purely inductive sensor, for example, allows for the active sorting of nonmetals from metal concentrates. This kind of “negative” sorting suppresses specific, unwanted objects in the material flow.

“Having the correct combination of sensors opens up further possibilities to clean up generated products beyond the extent originally required or to add sorting stages previously assessed as not feasible,” Knouwds says.

Specially developed Steinert software also allows for the design of new detection-algorithms, which can be implemented as needed to cope with new challenges.

Knouwds explains that the extended combination of up to four sensor technologies makes for a highly flexible sorting system, which allows for different sorting tasks using only one machine.

The KSS unit is often deployed in material recovery facilities dealing with multiple fractions in smaller quantities, where the installation of a dedicated sorting line for one fraction is not economically viable.

Therefore, a multi-sensory sorting system is installed instead as a standalone solution, which is then operated in batch-feed with different materials and processing objectives.

Constructional modifications are added when the KSS is deployed in the mining industry to account for wear-intensive environments.

Mobility and Access

The semi-mobile variant of the KSS, with a 1 m working width, is suitable for mineral processing applications. This special version is installed in a 40 ft container, with a further 40 ft container housing the operating room and controller.

The semi-mobile variant can include a diesel generator set, as well as compressors, conveyor belts and feed hoppers, providing a comprehensive overall concept to meet the requirements and ambient conditions while allowing for processing in remote areas without essential infrastructure.

Knouwds adds that setting up the testing plant at Navachab will also enable Steinert to mitigate Covid-19 logistical and travel restrictions to the company’s new test and development centre in Pulheim, Germany, which opened in September.

He tells Mining Weekly that the Navachab plant will enable Steinert to continue testing for various mines and processing projects throughout Southern Africa.

The new centre in Germany includes additional sorting lines for mining and waste recycling, which were installed to enable Steinert to “respond with ever more accuracy to the sorting aims of extraction, purity and profitability for each sorting task”, the company said in a statement released in March, ahead of the opening.

The Navachab plant will be capable of conducting feasibility or sighter tests, which is an analysis of the sensors’ ability to classify mineralised and nonmineralised ore, as well as an analysis of the efficiency of theoretical separation.

The new plant will provide tangible data of improved and sustainable production expectations for investors, as well as improve economic insights to better determine the risks and opportunities associated with investments, Knouwds concludes.