A new fine-coal processing solution for ‘clean’ coal production developed by Gravitas Minerals will be the subject of two major papers presented at the Southern African Coal Processing Society (SACPS) Biennial Conference at the Graceland Casino and Country Club in Secunda, Mpumalanga from 12 to 14 October 2021. This year’s theme is ‘Coal Processing and our Role in the Drive for Cleaner Coal’.

Franco van de Venter, who oversees Gravitas Minerals’ technological development facility in Benoni, will present a paper in conjunction with Multotec Process Equipment about how the Optima Classifier™ can be used together with traditional spirals in a fine coal processing circuit.

“We evaluated two approaches, where run of mine fine coal was fed to the Optima Classifier™ and where the Optima discard was fed to a low-cut spiral,” explains Van de Venter in his paper. The Optima Classifier™ can also be added to an existing fine coal circuit or mineral preparation plant as a separate module to boost overall recovery and quality.

Director Tebogo Kale (M.Inst.D), who has been developing the solution for the past four to five years, will present the business case for the technology, which opens up an immediate export market for RB1, RB2, RB3 and duff coal grades.

High-quality coal fines also offer a significant opportunity for briquetting, which in the past did not seem not economically viable. “If there is enough demand, fine coal could be briquetted to produce coal peas using organic binders. I believe this could bring about a serious case of remining the coal slimes dams purely to produce this product, which will reduce rehabilitation costs and lengthen the life of slimes dams,” predicts Kale.

This patent-pending, water-only density separator is at the heart of the solution developed by Gravitas Minerals, known as the Optima Process. The engineered system consists of a feed preparation, beneficiation/separation and dewatering modules to ensure a high-quality product with the correct moisture content. Typical products consist of ash below 16% and a calorific value of at least 27Mj/kg. Moisture plays a major role in the fine coal market and the water recovered from the product is immediately reused for processing.

Grain sizes of up to 5mm can be processed, while unit sizes of up to 150t/h can be built. The discharge devices are electrically controlled, which presents the opportunity for an easy-to-operate total ‘green’ solution. The fact that the process solution does not draw much power allows renewable energy to be easily and effectively added as the main power source for sustainability.

“This is a 100% South African designed and manufactured process technology,” stresses Kale. “Our technology allows our clients to maximise their outputs into the lucrative export coal market, which demands a top-quality product,” he concludes.