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HEAP LEACH MAY 2017 • E&MJ; 43 www.e-mj.com Southern Copper Corp. recently commis- sioned the world's largest Mobile Stack- ing Conveyor (MSC) system, which can stack ore at 12,500 metric tons per hour (mt/h), at its Cananea copper mine in northern Mexico. Supplied by FLSmidth, the MSC is an automated system that uses GPS and a self-alignment system to stack ore accurately, which should opti- mize leaching efficiency. During the past 20 years, FLSmidth has installed four large MSCs at the Cananea mine and they claim to have built 80% of the systems stacking ore at mines today. Cananea's MSC relies on an overland conveyor designed by Takraf that delivers P 80 4-in. ore to the MSC, which places the ore in a forward-stack- ing manner. The object is to build a con- sistent pile to a depth of 80 m across a valley. The system was commissioned a month ago. "This was a significant leap for Cana- nea in terms of automated technology," said Willem Fourie, product line manager in FLSmidth. "The automation improves machine performance as it stacks ore, producing the desired heap profile. The MSC can move backwards or forward in a linear fashion or rotate about any point. Ultimately, this will lead to better leach- ing efficiency from the heap." Cananea's MSC is nearly 300 m long. "With the integrated GPS, the machine knows exactly where it is located on a real-time basis," said Mark Mulligan, FLSmidth's process line manager for hy- dromet technologies. "From a mechanical perspective, the machine auto-self-aligns as it progresses forward on a real-time ba- sis. Because the machine is self-aligning, the heap is formed more accurately." An 80-m heap is a large heap by any standard. "To stack ore that high, the rock has to be quite competent to be placed in a single stack," Fourie said. "Since the machine supports itself over its length, it is naturally good at handling that type of situation. It can also accommodate for movement in the terrain." The stacking system runs 24/7 and, with automation, no operator intervention is required. So, availability is extremely high and ultimately the system stacks more tons per month. FLSmidth has minimized mainten- ance requirements, Fourie explained. "The mine's crews are quite familiar with the machines and they can attend to its needs quickly," he said. "The ma- chine also monitors itself, which makes fault-finding easier." The system is comprised of 40-m bridge systems, which were built off-site. They are supported by the hydraulic-driv- en crawler pads. "The sections arrive on site and we click them together and string them with a belt," Fourie said. Cananea's system uses a 6-ft belt. Ramp-up for this systems was very quick. "We were at full production within weeks," Fourie said. "We have supplied most of the world's mobile stacking con- veyors so I guess we're getting good at it." For FLSmidth, Mulligan explained, "Being able to improve productivity for the miners is very important especially as far as availability and being able to stack ore accurately and consistently, which enables better leach efficiencies and ul- timately better return on the investment." FLSmidth is also working on two copper heap leach projects in Myanmar, which will come online this year: "FLS- midth is supplying self-driven, 6,500- mt/h mobile grasshopper conveyors at one mine feeding an existing MSC, as well as a complete radial stacking system for another mine inclusive of grasshoppers, ramp conveyors, stacker feed bridge and the radial stacker at 1,200 mt/h through- put," Fourie said. The company is designing a number of large mobile stackers. "We are in the early stage of designing an MSC with dou- ble the output of the Cananea machine," Fourie said. These machines work well for heap leach applications, Fourie ex- plained, and they are also well-suited to stack overburden and dry tailings. Mobile Stacker for Heap Leach Applications The world's largest MSC places ore on a 80-m heap using side stacking at the Cananea mine in northern Mexico. The top photo shows forward placement. (Photos: FLSmidth)