Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr
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O P E R AT I N G S T R AT E G I E S The four LHD models in the Green Line are supported by a portable, trailer-mounted generator that is towed behind the LHD as it trams from one location to another in the mine, providing motive power to the Scooptram for as long as it's needed. The deeper the mine, the more savings can be realized. This is mainly due to ventilation costs, which increase exponentially with depth. In fact, only slight increases in depth result in much greater energy consumption. For example, Svedlund calculated that if a mine 1,000 m deep decides to increase its depth by only 100 m to 1,100 m, it will require a 10% increase in ventilation but a 33% increase in energy. On top of this, the mine may also need to add a cooling system or some form of air conditioning into the equation to deal with increased temperatures, which will further increase energy costs. A typical case in point is a mine in the Sudbury area of Canada. The mine decided to go in search of new ore below its 1,000-m main level and is now trucking ore from 1,700 m using Atlas Copco electric trucks. As a result, the mine has avoided the huge expense of installing a new shaft and has saved energy costs of extending its ventilation system to cope with diesel powered vehicles. The trucks carry a 50-mt payload and are able to tram fully loaded at speeds of up to 18 km/h up a 16% gradient, compared to 8 or 9 km/h for a conventional diesel truck. The trucks receive power from a series of overhead trolley lines extending 8 km, serving several levels of the mine, and disengage from the line for loading, dumping and entering the service bay. When it comes to the loaders, the LHDs in the new Green Line family are based on the successful Scooptram platform but with one essential difference; instead of diesel engines, they are powered entirely by highly efficient electric motors. Consequently, these loaders, which range in capacity from 3.5 to 14 mt, consume less energy, generate less heat and create less noise than their diesel counterparts. The result is lower running costs, less environmental impact and a better working environment. At the same time, the Electric Scooptram EST2D, EST3.5, EST1030 and EST14 all share a large number of components with their diesel equivalents, which ensures the availability of spare parts and support. Atlas Copco estimates that these 100% emission-free vehicles reduce energy consumption by about 70% compared with comparable diesel powered loaders and can also be run on renewable energy such as wind or hydro power. Maintenance is also greatly reduced, which gives further savings. Portable Generator Transporting the loaders to wherever they need to be in the mine is no problem thanks to a unique trailer-mounted generator system. The Gentrail GT325, which is specially designed for the harsh underground environment, hooks up behind the loader and provides all the power the loader needs in order to tram to different load/dump sites or the service workshop. It provides this www.e-mj.com JULY 2013 • E&MJ; 73