footprints, which can be both expensive and impractical in many situations. At the same time, it extracts more water from the tailings for reuse. Van Ryssen identified the need to construct tailings dams by utilising cycloned slimes/ tailings disposal techniques on minerals other than just phosphate. Over the intervening years it has been responsible for much development work in perfecting the cycloning techniques for various types of ore. In fact, since CP& C was established it has carried out the majority of contracts in the design, supply and commissioning of cyclone systems for cycloned dams in Africa. A cyclone works on the principle that in a centrifuge the heavier particles suspended in a slurry will gravitate to the outside of the flow while the lighter material- the water- remains on the centreline through the vortex finder of the cyclone. As a result, tailings pumped through a cyclone will be separated and the solid particles can be " discharged" directly to where they are needed as the building material for a tailings dam wall, while more of the slurry bearing water is discharged in the basin of the dam with water being recovered in the process. In reality, it's not always that simple. Some materials don't lend themselves to dam wall construction. They lack the fundamental stability necessary to build a safe structure without the need for uneconomically wide wall zones. In the past, haphazard design has been a costly exercise for the industry. As such, CP& C recommends that on- site cyclone test work be conducted on the tailings before a custom- built cycloned system is designed. Often initial trials are carried out on the company's in- house cyclone test rig before on- site tests are conducted. CP& C utilises a mobile test rig to determine the geotechnical properties of the different cyclone streams, creating data which can then be used for dam capacity calculations, the required drain design for that specific tailings product and the design of the cyclone system suitable for the material. Providing the cyclones is only a small part of the turnkey service CP& C provides. First there needs to be a thorough assessment of the proposal, evaluating the feasibility of building what the client wants. Once the system has been designed to ensure the best cyclone underflow, material is utilised for a safe and stable wall zone and the individual units produced. CP& C sources the entire package of pipe work, valves and instrumentation before completing installation and commissioning of the final system and handing over to the of experience in dam and tailings management across a wide range of minerals such as phosphate/ copper, gold, platinum, magnetite, chrome, manganese, gypsum, fluorspar and kimberlite. Cycloning is a process that eliminates the need for large 48 www. bus- ex. com July 09 " Not only is tailing management an expensive part of the process, it's also one that needs to be handled with considerable responsibility"
metre valley by utilising the laterite available in the slimes stream. On- site tests proved the concept was feasible and the mine now has a cycloned wall over 15 metres high with a vertical freeboard of seven metres or more- well within international standards. Tailings management might be the dirty, uninteresting side of mining, but it is a vital component in the overall profitability of a plant and a key component when it comes to safety and environmental issues. Having established itself as the leading consultant and supplier in southern Africa, CP& C is steadily being invited to lend its expertise in other mining parts of the world. CP& C has established a sister company which operates the dams on behalf of the client under management contracts. The company, Cyclone Engineering Projects ( Pty) Ltd is managed by a dynamic team from the offices of CP& C in South Africa. - Editorial research by Robbie Hodgson Cyclone Projects & Consulting July 09 www. bus- ex. com 49 client with operating manuals and maintenance schedules. Cyclone Projects & Consulting has created any number of industry innovations. For example, at a diamond mine in Botswana, slurry from the kimberlite diamond bearing rock ( high in slimes) was being deposited within expensive earth- constructed impoundments and very little water was being recovered. CP& C, in the first such plant in the world, showed that by leaving the grit in the slimes stream at the scrubbing plant, cyclones could be used to produce a stable wall and more than double the amount of water being reclaimed. Again, at a gold mine in the Republic of Mali, West Africa, CP& C demonstrated that cyclone walls were possible with tailings made up of 10 per cent laterite and 90 per cent saprolite- a material considered unsuitable for cyclone construction. CP& C was set the challenge of devising a system capable of building a safe and stable slimes dam main wall through an 1800