01/31/2013 | Author / Editor: Gunthart Mau * / Marcel Dröttboom
For an iron ore mine in Brazil owned by Vale, Thyssenkrupp Fördertechnik is manufacturing a mobile crushing and conveying system used for excavated material. Numerous drive functions must be realised on the mobile crusher. The entire project includes 54 drive packages that are used for various drive tasks on the system.
Wherever large amounts of earth and materials need to be excavated, mining technology from Thyssenkrupp Fördertechnik is likely to be involved. Thyssenkrupp Fördertechnik bucketwheel excavators, belt conveyors and spreaders can move enormous quantities of material – well beyond 200 000 m3 per day. “Crusher systems crush excavated material into pieces suitable for belt transportation directly at the excavation site. The material can then be transported economically and continuously with the help of belt conveyors. Thyssenkrupp Fördertechnik was deeply involved in Essen and Ennigerloh in the development of these crusher belt conveyor systems,” explains Johann-Dieter Wiekhorst, Senior Engineer Drive Systems in Mining. Today the company is one of the world’s leading manufacturers in this sector. A prototype of this fully mobile crusher has already been operating in China for several years.
Vale is a Brazilian mining company that claims to be the second largest in the world and the largest producer of iron ore. It has locations on all continents, including several in its home country. Parauapebas is located a good 1000 km north of the capital city of Brasilia in the state of Pará. Located close to this medium-sized city is the Carajás N4E mining complex. This is the site where Vale Mining is exploiting iron ore.
Yet before the valuable raw material can be drawn out, the earth must first be stripped, broken up by a crusher and then further transported. Power shovels remove a layer of earth roughly 15 m thick for each section (excavation level). Projected for a year, a single crusher can smash roughly 20 million tonnes of excavated material. Vale has previously used heavy-duty trucks in mining to remove these massive amounts of material. With their high power, these vehicles also consume large quantities of diesel. Even the oversized tires add to costs as they need to be replaced on a regular basis. So the operators decided to use giant mining equipment instead. Vale commissioned Thyssenkrupp Fördertechnik with the construction of two crusher belt conveyors. This new equipment will help lower operating costs and reduce CO2 emissions from operation.
“The entire system is centred around two fully mobile crushers (MCs) that crush the excavated material. This mix is then conveyed by two belt wagons to a belt conveyor, which transports the mix over a distance of several kilometres. Later, the excavated material is removed by a tripper car and dumped over a spreader,” explains Matthias Kasselmann, Senior Project Manager in Thyssenkrupp Fördertechnik’s Mining division. Then he adds: “We supply complete fully mobile crushers and all other core component units such as gear units and ball slewing rings. Our Brazilian subsidiary in Belo Horizonte, about 350 km north of Rio, provides the rest of the components and assembles everything together.”
The type designation of the fully mobile crusher is MC 3900. It sits on a crawler-mounted machine and weighs a total of roughly 1500 tonnes. The crusher is 17.5 m tall and almost as wide. With its boom it is about 50 m long. The system is designed for 24-hour operation throughout the whole year. The only time it is not working is between shifts, when the belts are moved and when the crusher is placed in a different position. The projected service life of the crusher system totals more than 50 000 operating hours. With an average operating time of around 4500 hours in a year, the equipment will last for more than ten years, and usually much longer.
A power shovel feeds the mobile crushers with 35 m3 of excavated material per minute. This is equivalent to 65 tonnes of material. In an hour, the crusher’s throughput is about 3900 tonnes of excavated material. An apron conveyor transports this material up to the mobile crusher. From here, the material falls into a crushing plant that consists of two rollers rotating in opposition. The rollers have spikes that break up the material. There is an uneven number of these spikes distributed over the entire circumference. This prevents the same opposing spikes from pairing up with every rotation, which would lead to increased wear at individual places. The crusher has a torque of 400 000 Nm. (For comparison: Depending on engine size, a sports car has about 350 Nm to 600 Nm.)
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