Minerals and fines processing specialist Gravitas is nearing completion of a fine coal beneficiation project for which it has supplied two Optima Classifier water-only density separator units to produce clean coal that would otherwise have been deposited into a slimes dam.

“Historically, the fine-grained material in commodities such as coal, iron-ore and manganese were not considered for beneficiation. With the depletion of reserves and increasing product demand, the industry is starting to look at fines beneficiation as an option to enhance profits. Beneficiating this material also dilutes operating costs for our clients,” says Gravitas founder and CEO Tebogo Kale.

The separator’s design was acknowledged by Mining Equipment Manufacturers of South Africa in April when the company won the innovation by an emerging or small enterprise award at the 2022 Innovation Awards.

“We developed the Optima Classifier as we believed there was a gap in the market for a simplified, versatile, accessible technology that would contribute positively to the environment while boosting investor and/or customer returns,” notes Kale, highlighting that the technology can be applied to more than ten different commodities, including anthracite, coking coal, chromite, iron-ore, manganese and ferrometals.

A hindered settling separator, the Optima Classifier uses upward current water to create a column of stratified slurry in a tank. The heavier particles, which concentrate at the bottom of the tank, are discharged through the reject discharge valve, while the smaller and lighter particles overflow the weir and are collected in the overflow launder with the overflow water.

Heavy, smaller particles are recovered back into the settling chamber by reducing the upward flow velocity, creating crowding in the upper settling chamber, which then forms autogenous dense medium.

The unit can be controlled using a plant programmable logic controller system or a remote Optima Concentrator control system.

Compared with other solutions on the market, the Optima Classifier offers a high return on investment, owing to its capability to produce premium quality material at a higher recovery rate, he adds.

In addition, the Optima Classifier addresses environmental compliance concerns as it has a low carbon footprint of between 25 t/h/m² and 30 t/h/m², with its higher recoveries also meaning less material is diverted to tailings ponds, reducing environmental liability.

After a four-year development stage, involving proof of concept using different minerals, repeatability tests and performance testing, the first trial units were installed in 2019 and are still operating successfully. However, development is ongoing as Gravitas continues to discover more applications, says Kale.

“Demand for the Optima Classifier is driven by new mining projects and our clients’ willingness to continuously improve their existing operations as it can be used as a separation module add-on to an existing coal or mineral preparation plant, to increase overall plant recovery and quality.”

Manufactured through fabrication and automation in Benoni, Gauteng, the Optima Classifier comprises 97% local content, with the only offshore inputs being automation components that are not produced locally.

“Should we find local manufacturers for these items, the Optima Classifier will be a 100% South African product,” states Kale.

While Gravitas has not exported units yet, it expects to start exporting its custom designed and built to order Optima Classifier soon.