FLOTATION
ProProcess Engineering designed and delivered Anglo American Platinum ’ s new Modular Fines Flotation Pilot Plant
Flotation factors
Paul Moore looks again at the latest in flotation – from new cell designs and innovations for coarse and fines flotation plus general industry trends and some key projects
Innovation is at the heart of progress in mineral processing – and anything that permits greater optimisation at a pilot scale before scaling up is highly valuable for mines dealing with variable ore inputs . South Africa ’ s ProProcess Engineering , based in Germiston , Johannesburg , recently switched on the power to Anglo American Platinum ’ s new Modular Fines Flotation Pilot Plant and has commenced C1-C3 commissioning . In August 2020 ProProcess was awarded the Engineering , Procurement and Construction contract for the plant for Anglo American which it describes as a “ world class test facility for platinum concentrate flowsheet optimisation .”
Stefan Van Dyk , ProProcess Project Manager states : “ The aim of this project was to produce a modular , transportable , cost effective and built for purpose pilot plant . Pilot plants have much less stringent equipment requirements than production plants and this needs to be kept in consideration to avoid over-designing the plant , thus unnecessarily escalating the capital outlay . This required a lot of out of the box thinking and many new ideas and concepts were explored to ensure a built for purpose plant . Anglo American has very high safety , maintainability and operation requirements and standards for their production plants . As the pilot plant would be placed into a production environment it was crucial to determine which standards to adhere to and where concessions could be obtained .”
The plant had to be designed with maximum road transportability in mind , as the pilot plant is earmarked to be moved around various concentrator sites owned by Anglo . To this end the entire plant consisting of 40 + flotation cells ( including a high intensity flotation cell ), a mill , ~ 30 tanks ( some agitated ), ~ 50 pumps
( including centrifugal slurry , peristaltic , vertical spindle ), blowers , compressors , etc was fitted onto 16 road transportable ISO frame skids conforming to 40 ft marine container dimensions .
Tanja Marcus , the Process Lead said : “ For the process to operate effectively adequate buffer capacity between the individual unit operations needed to be catered for in the design . A slurry with a high density ( SG > 3 ) is fed into the plant . To avoid settling of this material in the tanks a very steep angle of 45-60 degrees on the tank cones had to be used . The tanks also had to fit the height of the skid , thus limiting the tank height to ~ 1.8 m . This lead to oddly shaped vessels that consist mainly of cone , with very little tan-to-tan height . Some of the reagents required on the plant are hazardous . To avoid additional equipment in the form of a scrubber and associated neutralisation reagents , the potential hazard was designed out to cause minimal risk .”
Kean Southern , Mechanical Lead said : “ ProProcess applied our specialised modular approach to the design of this plant for simplified site installation and ease of transport . This meant each skid frame was custom designed and built to 40 ft shipping container dimensions , eliminating any restrictions on road transport , or the need for special permits . All equipment is pre-mounted , piped up and tested at our workshop before shipment to site . Once testing is complete , all that is required is for flexible , interconnecting piping between the frames to be disconnected ( which is made easy with the use of flanges and claw couplings ). Given the numerous pipe sections run between frames , each connection of flexible hose needed to be tagged to ensure the correct hoses were
reconnected during assembly . Since the plant arrives on site already partially assembled , site installation is a breeze .”
Emile Strydom-Bouwer , Electrical Lead commented : “ All skids are prewired to Male Power Sockets on local junction boxes . The MCCs are similarly prewired to Male Power Sockets on the MCC wall . The interlinking cables have a Female Power Socket at either end thus no on site glanding and terminations will take place . A potential problem is that the cable can be energised and cause an electrical shock . We , as a design team , mitigated this risk by specifically manufacturing a late-make / earlybreak pin set and connected it to the safety circuit . Thus the cable can only be energised once fully inserted at both ends .”
New and improved WEMCO ® nextGEN™ ; first full RFC™ trial
FLSmidth ’ s WEMCO cells are used throughout the global mining industry but the company recently set out to improve the design further . Using a large flotation lab apparatus ( 25L ) that was designed to scale-up the industrial tanks , extensive research was developed in order to review the current WEMCO flotation cell technology . Although WEMCO cells already offer outstanding performance , they were developed some years ago and with advances in technologies and following important customer feedback from around the world during those years FLSmidth decided that is was time to review this technology again . This new apparatus , along with a new test methodology , was used to evaluate new rapid prototype concepts . The setup also monitored bubble size , power , Jg , and tip speed in parallel with CFD simulations . After extensive work at lab scale , showing huge improvements in the air intake , power reduction , and performance improvements through changes in the WEMCO design , as a natural step on research development of new designs , tests in a bigger scale and in a continuous setup were required as the next move to validate the results found in the lab . FLSmidth has 1.5 m 3 pilot units that are mounted over a skid with a feed flow meter , air flow meter , level sensor , and tailings control valve that is the perfect next stage . The next step was to select a site to be able to test the setup . KGHM ’ s Robinson mine in Nevada has a state of the art copper operation and has a long collaboration history with FLSmidth , making the site a natural choice for the research . At site rougher feed was collected in an agitation tank that fed two 1.5 m 3 pilot units in parallel ; one unit running with the WEMCO standard design
36 International Mining | OCTOBER 2021