Engineering & Mining Journal

FEB 2018

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HYDROCYCLONES FEBRUARY 2018 • E&MJ; 29 www.e-mj.com added benefit of reducing wear rates in the inlet head, the company stated. In addition, various liner materials have been tested to provide a more even wear rate throughout the entire assembly, reducing the likelihood that components are removed prematurely due to convenience alone. Metso pointed out that maintenance time is further reduced via simplification of the design. The number of individual components has been reduced by the single-component conical section, which eliminates the need for multiple conical section liners and housing pieces, reduc- ing maintenance time and cost. Seven different hydrocyclone sizes are available, ranging from 100 mm to 800 mm (4-32 in.) in diameter. Each size has a range of vortex finder and apex inserts to fine-tune the classification performance. High-grade polyurethane and ceramic wear component options offer a balance between wear performance and cost, depending on the project specifics, Metso said. The validation process for the MHC hy- drocyclone included field and pilot testing of various hydrocyclone sizes and applica- tions. Extensive testing was performed at the pilot scale and at a copper concentrator in the southwestern USA. A 650-mm-di- ameter unit was installed in the grinding circuit for wear-component prototyping and continued process data collection. Metso noted, to date, that field tri- al has been in operation for more than 12,000 hours, with the data generated from the trial being applied to the compa- ny's empirical hydrocyclone model used for sizing and simulation purposes. Over a Century of Experience According to the U.K.-based company, Salter Cyclones, hydrocyclones were first patented in 1891, but it was not until 1939 that a Dutch company first used them to clean coal and dewater sand. Now they are an integral part of the technology available for solid/liquid separation. Company Director Lynn Emanuel told E&MJ; that Salter has more than 100 years of collective experience, and specializes in the removal of fine solids, typically be- low 50 microns (µm), with specifically de- veloped hydrocyclones sized from 10 mm to 10 in. Applications range across a wide spectrum of ores, including separating sand and mica from kaolin slurry, and the production of high-grade filler and coating clays for the paper industry. The hydrocyclones can be packaged in radials, "mushroom" assemblies or canisters, all designed to be practical, operator-friendly and economic systems. They provide continuous efficient service desliming ahead of flotation, classifying, degritting or dewatering, Emanuel said. Recently, a British company wanted to replace aging scalper centrifuges in one of its American plants. Because of the limit- ed footprint available, Salter's 1-in. hydro- cyclones were packaged as a radial of six, 10-way canisters. Bottom-fed, these are arranged around the central overflow collec- tion vessel and are circled by one underflow collection launder, giving the client a very efficient, compact and space-saving solu- tion, she explained. "This was so success- ful that they ordered 1-in. hydrocyclones in a radial of five, 21-way canisters to thick- en the effluent from treating hectorite and bentonite for their U.K. site," she added. In a different type of application in the Philippines, an eight-way 10-in. hydrocy- clone radial and an 18-way 2-in. hydro- cyclone assembly are operating in a pilot plant to deslime and upgrade chromite and hematite. "On both these projects, initial test work was carried out in our laboratory," Emanuel pointed out. "Hydrocyclones are being used more and more frequently in different parts of the process," she went on. "Mines are chasing ever-smaller valuable solids and retreating tailings. More efficient desliming is required to increase down - stream equipment performance and re- duce chemical consumption, making our smaller and more powerful hydrocyclones ideal for these applications." Listening for Roping To get FLSmidth's view on hydrocyclone technology, wear liners and other perti- nent aspects, E&MJ; spoke to the compa- ny's cyclone product manager, Barry But- tler. "While there have been few dramatic changes in the technology over the past 10-15 years, from our perspective the major step-change came with the launch of our gMAX range of cyclones in around 2000," he said. "Since then, more at- tention has been paid to liner materials; they're thicker than they used to be, and there is a wider range of materials avail- able to suit individual applications. "In fact, cyclone liner materials are of- ten 'mixed and matched,' with BPC rubber in the top, lower-wearing sections of a cy- clone, followed by two to three grades of ceramic liners as you go lower down the cyclone to the apex (spigot)," he said. "The intent is to get the maximum life from the cyclone and then rebuild the entire cyclone at one time. It's a big advantage to use a mix of liner materials." By way of illustration, Buttler referred to experience gained at an Indonesian cop- The eight-way 10-in. radial hydrocyclone assembly supplied by Salter Cyclones for upgrading and desliming chromite and hematite in the Philippines. A cut-away view through an FLSmidth Krebs cyclone, showing the different liner materials used from inlet to apex. The aim is to provide even wear throughout, then replace all the liners in one hit, the company says.

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