Modern Mining June 2016

PRODUCT News

VXPmills to be used in “severe process conditions” Because they operate at a power intensity that is higher than low speed mills and overlaps that of high speed mills, one of the major traits of VXPmills is their flex- ibility, allowing them to be engineered and manufactured for a host of grinding applications.

in extreme acidic conditions on a copper processing operation in the Middle East. “The outcome of this project was yet another derivative of these mills. In this instance, we adapted the VXPmill’s design to work in severe process conditions,” says Terence Osborn, Sales & Marketing Manager for sub-Saharan Africa at FLSmidth. He says the VXPmill is a vertically ori- ented stirred media mill that is open to the atmosphere and designed with a modular impeller that has removable discs and spacers. Slurry enters at the bottom, travels upward through the mill chamber, and overflows through a media retention screen at the top. The rotating polyure- thane discs activate inert ceramic grinding media inside the milling chamber. This flui- dises the media bed, attrition grinding the particles in the slurry. Osborn says the system is designed to allow changes to the distribution of the media and energy within the mill by altering the number and spacing between the impeller discs when the mill is commissioned. Assembly of the two mills will start in August this year, followed by testing at FLSmidth’s facility in Johannesburg. The mills will then be containerised and shipped to site and commissioned by FLSmidth before the end of the year where after they will play their role in helping the copper producer improve the

recovery of very fine copper particles. Because the mills will be exposed to pulp, they had to be engineered specifi- cally for extremely acidic environments, with a PH of 2,5. This meant the compo- nents of the VXPmills had to be made from a variety of materials that would not only withstand arduous operating conditions but also ensure that the plants could be built within budget. Osborn says this was a complex under- taking providing various challenges for the company’s local engineers. The South African team also made extensive use of the expertise of FLSmidth’s design engi- neers in India. Osborn describes the end result as an ingenious solution. “We did not go for one specific material selection, such as stainless steel, but rather opted for a combination of many different materials based on the principal operational requirements of each component as well as the suitability to withstand the acidic environment. We do not believe that there are many engineers who would have been able to achieve this outcome, over the time period and within budget,” he says. The end result saw only a 7 % increase on the initial costing of the mills, with the solution comprising a combination of mild steels, austenitic and duplex stainless steels, fibre reinforced plastics, as well as polyurethane and polyurea coatings. FLSmidth, tel (+27 10) 210-4820

This important characteristic has been demonstrated again, with FLSmidth’s South African operation in Roodepoort involved in the engineering design and manufacturing that will see VXPmills used

This VXP2500 in Zimbabwe was the first of the updated VXP2500 mill series.

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58  MODERN MINING  June 2016