Best of Germany 2014 - Mining Equipment and Mining Technology

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2016 • VDMA MINING SUPPLEMENT VDMA 29 Wirtgen's 4200 SM surface miner (above), cuts and crushes the rock with a special cutting drum and loads it into haul trucks in a single pass via conveyor system. Wirtgen is the only manufacturer that can offer a performance range up to 3,000 mt/h with direct loading by conveyor belt. In recent years, Wirtgen has conducted several large-scale field tests on particle size distribution and material degradation. Coal and sedimentary ore from eight different pits were analyzed to obtain their particle size distribution. Almost 8,000 metric tons (mt) of material were screened to compare the material produced by Wirtgen surface miners and conventional mining methods. In one coal mine, Wirtgen surface miners are operating alongside dozers that employ the conventional rip-and-stack method. In view of the current coal prices, the mine was optimizing every step of the op- eration. This included optimizing the process for target size material, enabling most of the material to be processed in the cheaper coarse circuit of the processing plant. They also were keen on reducing crush- ing costs. The test proved the suitability of the surface miner for this kind of operation once more: The machine delivered coal with a lower fines level and more target size material than the conventional dozer rip-and- stack method. In fact, out of the 1,500 mt/h of coal delivered from the dozer to the processing plant, 225 mt/h are fines (less than 2 mm). The surface miner generated 185 mt/h of fines for an equal amount of coal. This means that 22% less coal has to be washed in the fines circuit and can be washed in the cheaper coarse circuit. Looking at the material measuring less than 1 mm, the plant processes 33% less fine material when working with coal produced by the surface miner. The surface miner delivers more than 70% target size coal (2–40 mm), while the dozer ranges at less than 58%. Additional savings are generated in the crushing stage: only 17% of the material coming from the surface miner has to be crushed, as opposed to more than 26% when processing ripped coal. This will also result in more fines that have to be processed. Another trial location was a sedimentary ore deposit that is mined us- ing surface miners and the conventional drill-and-blast method. There, the surface miner was able to continually feed material where the less than 1-mm size fraction was as low as 15% to the processing plant. The normal plant feed (includes material of drill-and-blast and surface miner operation) contained 25% and more fines (less than 1 mm). Re-handling contributes significantly to material degradation. Simu- lating the re-handle, Wirtgen conducted a study to establish the amount of material degradation that does occur. For simulation purposes, 80 mt of material were loaded by a wheel loader and run through a screening plant several times. With every throughput, the amount of fine material increased signifi- cantly. During five test cycles in coal, the amount of material less than 4 mm increased from 19% to 26%, representing an increase of 34%. A similar result was found with sedimentary ore: the fine fraction increased by 24% during five test cycles. None of the steps in this re-handling simulation (loading, transport to the screen deck, sizing on the screen deck itself) involves the high mate- rial stress levels that would be induced, for example, by a dozer moving on stockpiled material. Nevertheless, significant material degradation was measured during the simulation. One can assume that the material degradation that takes place during stockpiling results in an even higher increase of the fine fractions. Keeping in mind that even this kind of "soft" re-handling causes sig- nificant material degradation and that a lot of re-handling steps occur all throughout the coal production chain, it is important to minimize the number of re-handling steps. What is more, every re-handling step itself results in additional costs. This is where Wirtgen surface miners offer a two-fold advantage: Material mined with a surface miner has not been blasted, but cut out of the ground by the rotating cutting drum, thus the level of fines is already low. But as the material is loaded straight onto a truck, re-handling is kept to a minimum and thus the level of fines stays as low as possible. Looking at the complete mining operation, using a surface miner simplifies mining operation and reduces the number of process steps, resulting in immediate cost savings. Operating a Wirtgen surface miner will reduce the quantity of active equipment required to load a ton of coal by streamlining the mining process. Furthermore, it will simplify the interdependence of process steps in mining operation, reducing costly time losses between the individual process steps. ABEL GmbH, 21514 Buechen, Germany, mail@abel.de ABEL Pumps L.P., Sewickley, PA 15143-2339, USA, mail@abelpumps.com He likes it we pump it For difficult pumping of tailings, slurry or paste, meet the ABEL heavy duty HM series piston-diaphragm pump. Designed for the most challenging tasks in mines throughout the world. Learn more about our mining competence at www.abelpumps.com

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