Rotary classifier

A novel way of separating granular material during mineral processing could help solve one of the industry’s most frustrating and costly problems – blinding.

Blinding occurs when the giant screens used by the world’s mining industries to separate minerals for processing become blocked.

A new type of sorting machine, christened the Rotary Classifier, has been developed by a team of scientists at CSIRO Manufacturing and Infrastructure Technology.

The Rotary Classifier separates granular material by tumbling material in a tilted vessel at various speeds, causing avalanches in the surface. This moves particles of a smaller size or higher density towards the centre and particles of larger size or lower density radially outward, allowing different materials to be extracted at selected locations.

The Rotary Classifier is currently being investigated by mineral processor RCR Tomlinson which plans to have a pilot tumbler in operation by early 2007, before scaling up a full system.

General manager of RCR Tomlinson’s Bunbury operation, Mr John Noordhoek says blinding is a huge problem. “Once a screen becomes blocked, it reduces screening efficiency and increases processing time,” he says.

He says the Rotary Classifier development could overcome this problem and improve production efficiencies. “Building a commercial scale pilot plant will allow us to prove the technology works. Early testing looks positive, so the potential out there for a screen-replacement product is huge.”

Co-inventor of the Rotary Classifier, Dr. Guy Metcalfe, says the unit’s dry separation ability is an unexpected benefit. “Dry processing is becoming more and more important. It was not the reason we started looking at the fundamentals of granular materials, but it has become a huge selling point for the technology,” he says.

He says the technology will be of immediate importance to the iron ore industry, where more minerals are obtained in an environment where limited or no water is available.

“Some processors are already talking about having to pump in sea water, desalinating it and then using it for separation processes, a costly process. However, if we can prove that dry separation works, industry could be clamouring to use it,” Dr. Metcalfe says.

“However, other possible applications are in the grains industry and the construction industry, which both separate a lot of granular material. It could also benefit the chemical industry, because 60 per cent of the inputs they use are granular.”