Weir Minerals Africa is poised to go into full production with its fully locally fabricated Cavex^® ceramic dense medium (DM) cyclone, developed to offer coal companies around the world an alternative to currently available systems. The Cavex DM cyclone features a unique laminar spiral inlet geometry that delivers sharper separation, maximum capacity and longer wear life than conventional involute or tangential feed inlet DM cyclone designs. The range currently extends to 1,450 mm in size, with sizes up to 1,000 mm available locally. The 1,150 mm, 1,300 mm and 1,450 mm are in the final stages of development and will be available locally within the near future.

JD Singleton, Cyclones and Engineered Systems Product Manager at Weir Minerals Africa, says the design of the laminar spiral inlet geometry provides a natural flow path into the cyclone body, allowing the feed stream to blend smoothly with the rotating slurry inside the chamber. The result is greatly reduced turbulence through the entire cyclone, which boosts separation efficiency significantly.

“A few years ago we took the decision to pursue the Cavex DM cyclone as a premium brand for coal applications, based on our very successful classification cyclone legacy, and took steps to set up local fabrication facilities to ensure competitive pricing and reduced manufacturing times,” Singleton says. “Steel design is being managed in-house and we have teamed up with a local ceramic tile supplier to manufacture heavy duty >92% alumina wear resistant tiles, which are bonded onto prepared substrate using troweled-on two-part epoxy adhesive for enduring strength.

“We expect to be able to offer the best wear capability in the market, based on our innovative feed chamber design, and this has given us the confidence to offer local coal industry operations that are currently using cyclones, a no-cost and obligation-free three month field trial at their sites.

“Coal is a huge growth area worldwide at the moment and this market is relatively untapped from a dense medium cyclone perspective for Weir Minerals. We regard this as a great new prospective market,” he says.

DM cyclones are commonly used for separating coal from rock. Fine (minus 45 micron) magnetite is added to water to form a medium. Medium density is adjusted to a value between the density of coal and rock. High density rock moves through the medium to the cyclone wall and out of the apex, while light coal particles enter the overflow stream.

The Cavex cyclone was initially developed in response to industry concerns relating to cyclone wear and reduced efficiencies in grinding circuits. Typical feed designs are 75º and 180º involutes. Existing designs were prone to wear near the inlet, as a result of turbulence and coarse particle scouring.

“Our experts addressed this problem using years of slurry pump modeling design experience and the result was the Cavex cyclone, with a three dimensional curvature along the inlet path,” Singleton says. “This curvature smoothes the path of the fluid and reduces turbulence upon entry into the cyclone. The benefit is an improvement in the net inlet energy loss, which increases the fluid tangential velocity and centrifugal force.

“The launch of our new Cavex ceramic DM cyclone is the result of our consistent focus on finding solutions that maximise efficiency and minimise costs, supported by our wealth of experience and knowledge, locally and around the globe,” he concludes.