Surface mining technology takes over from dozers and loaders at Australian coal mine
THE New Acland Mine (NAC), located adjacent to the township of Acland, in Queensland, is part of the Australian-based New Hope Group. Since the opening of the mine, coal and interburden have been extracted by means of bulldozers fitted with ripper teeth, assisted by wheel loaders.
However, a sharp drop in coal prices compelled the NAC management to look for alternative, more efficient mining methods.
A solution was soon found: Wirtgen’s surface-mining technology offered the ideal method for the challenging geological conditions in the mine, which comprises up to 27 mostly thin coal seams interspersed by layers of interburden.
Compared with conventional methods, the selective surface mining technology simplifies the mining process, thereby reducing operating costs and supplying coal of higher quality to the neighboring processing plant.
Wirtgen surface mining has proven its worth as a tried-and-tested technology in numerous coal mining projects, so it came as no surprise that the six-month trial phase with defined target performance levels agreed upon between NAC and Wirtgen was a resounding success: the 4200 SM achieved the projected cutting performance of up to 3,000 tons/h.
To maximize exploitation of the coal deposit, the high-performance 4200 SM cuts and loads the material in a single pass, producing an even and easily trafficable surface in the process.
It was also established during the trial that, while offering the same performance, the surface miner replaces two bulldozers and one wheel loader. The resulting savings, mainly in labour and fuel, have led to a significant reduction in operating costs.
Additional marks in favour of the 4200 SM include measurement results showing significantly reduced machine vibration and noise levels. This, coupled with the ergonomically designed cabin, means impacts on the operator’s health are minimized, particularly in the long term.
A camera system designed exclusively for the NAC operation allows the machine operator to conveniently differentiate between coal and interburden, thereby significantly improving the coal quality. Moreover, the strict safety regulations and machine standards specified by the Australian coal industry were fully met by making relevant machine modifications prior to shipment.
Moreover, the cutting drum has been specially designed for operation in soft rock and is well suited to mining not only the brittle thermal coal (unconfined compressive strength = 20 MPa), but also the significantly harder interburden layers (50 MPa).
The 4200 SM mines the coal in a selective process at an exactly specified cutting depth, producing a clean cutting surface and guaranteeing a high degree of purity. As a result, fewer truck journeys are required to transport the material to a special coal-washing plant for further processing and to return the separated tailings to the mine.
Compared with the mining method used to date, the 4200 SM also produces a smaller percentage of –2mm fines and a higher percentage of the –38mm end-product fraction, which in turn helps improves the efficiency of the processing plant.
Praising the highly productive machine, Andrew McDonald, managing director at NAC, said: ‘I am impressed with the economical, modern and environmentally friendly Wirtgen surface miner. NAC save hard cash as soon as the miner is in operation.’