NEWS & REPORTS The Wirtgen 2500 SM surface miner The 2500 SM is a heavy-duty, high-performance miner equipped with a 2.5 m wide cutting drum for material mining. Depending on rock hardness, it achieves cutting performances of up to 1,400 tonnes per hour – as is the case in coal and oil shale mining. The design of the 2500 SM minimizes the time required for maintenance procedures: vital machine components, such as the cutting drum, offer easy access to allow the quick replacement of wear parts, such as cutting tools. Over 50 miners of type 2500 SM are in operation around the globe. Wirtgen GmbH has developed the 4200 SM for even higher performance levels: this surface miner is capable of loading heavy-duty trucks of up to 200 tonnes in a mere matter of minutes. Being the biggest Wirtgen surface miner, it is capable of mining up to 12 million tonnes per year in soft rock.
Comparative testing of the mining methods The use of Wirtgen surface miners in Estonia allowed a direct comparison to be drawn between surface mining and the conventional mining processes of drilling and blasting and semi-selective mining. The comparative test assessed quantitative parameters, such as the ROM, but also included qualitative aspects, such as the calorific value of the mining material.
Method 1: drilling and blasting In non-selective mining, the material is loosened by means of blasting and then loaded onto trucks by excavators. In the process, the oil shale mingles with the embedded limestone. Prior to processing, the material extracted by blasting needs to be crushed in crushing plants.
Method 2: semi-selective mining Semi-selective mining does not use drilling and blasting. Oil shale and limestone are extracted and loaded using rippers, bulldozers and excavators. This process also results in a significant degree of mixing between the two materials. Both oil shale and limestone are of a plate-like nature. As a result, crushers are required to achieve the specified particle size.
Method 3: surface Mining Surface miners are equipped with a rotating cutting drum enabling precise adjustment of the cutting depth to within a centimetre to cut the different layers of rock. The highly selective mining process enables separate extraction of the oil shale and limestone layers. The use of primary crushers is eliminated as surface miners cut, crush and load the material in a single working pass.
Selective mining of horizontal oil shale and limestone seams with the 2500 SM. Two of the Wirtgen miners are currently in operation in Estonia.
Issue 04 | 2011
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