Expanding the Horizons of Mining Technology
After 12 years, Terex SHM is ready to build its American foundations with a strongly focused expansion program into the world coal mining equipment market.
The company was, from the start, prepared to take some time to get established in the market. Between 1994 and 1999 it shipped out five machines, all of them to customers in Appalachia.
The company now has over 50 machines in operation, and in 2003 made the breakthrough in mining technology that it had been waiting for: highwall miners at work overseas.
Although the three machines sold into Russia have proved to be the company’s sole foreign venture to date, it hopes that in the future, highwall mining will become as readily accepted in other countries as it has been in the US. In a commitment to expanding its market, the company will be aggressively targeting mining technology opportunities in countries such as China, Russia, South Africa, Australia and Indonesia, not to mention Canada, Columbia and Venezuela, which are closer to home.
Of course, it is only fair to say that mining conditions in the US, and in particular, in the rugged terrain of the eastern Appalachian coalfields, are ideally suited to the use of highwall mining techniques, which involve the remote-control production of coal from resources that would otherwise be economically unworkable. In this topographical and geological context, Terex SHM’s highwall miners present coal production and contract mining companies with a truly viable third option, in addition to conventional surface and underground mining systems. However, experience has already shown that the mining technology is by no means limited to this environment, with a relatively simple transition to its application in other coal resource situations, such as end-of-open cut highwalls or trench mining.
For this reason, Terex SHM believes that given the right combination of seam geology, location and permitting procedures, highwall mining has great potential in other parts of the world. Companies are beginning to consider highwall mining as part of their overall mine planning strategy, not just as an add-on to other conventional mining methods.
A Little Background
Now in its second generation, Terex SHM’s highwall miner is a self-contained, remotely operated mining system that is designed to recover coal from seams deep beyond the economic limits that govern conventional open-pit or open cut mining. The original mining technology concept, which shares a common heritage with smaller-diameter auger-mining systems, was developed to produce coal from behind the highwall created by contour mining in the eastern US coalfields, with the machine standing at the highwall foot, on benches formed typically by conventional shovel-and-truck operations. Depending on the height of the seam being recovered, each machine can produce an average of 32,000 – 110,000 tpm of coal. In terms of resource recovery, it can extract up to 70% of the in-situ coal, while operating on contour benches – or in trench-mining applications – as narrow as 13 m (42 ft).
Measuring 10 m wide and 16.6 m long, the Terex SHM launch vehicle is carried on four hydraulically powered crawler units that give 360° mobility and allow the mining technology product to be positioned precisely in front of each entry, even if the highwall is irregular. Interchangeable electric cutterhead modules mine coal seam heights ranging from 710 mm (28 in.) to 4.6 m (15 ft). The cutterhead advances by sumping (pushing forward) and shearing (raising or lowering the cutterhead boom), with the sumping force being supplied by two hydraulically powered cylinders mounted on the launch vehicle that generate 172,400 t of force.
The sumping force is transmitted to the cutterhead by means of 6.1 m (20 ft) long fully enclosed pushbeams. As the cutterhead pushes into the seam, the cut coal is carried by a pair of 460 mm (18 in.) diameter conveying augers that run inside the pushbeams, a major advantage of this system being that any rock that falls from the entry roof lands on top of the pushbeam and cannot contaminate the coal being transported inside it. Once the cut coal has arrived back at the launch vehicle, it is discharged either directly into waiting haulers or to a stockpile of subsequent loading out.
In addition to providing the drive transfer and transporting the cut coal, the enclosed purshbeams play one further vital role. All of the service connections from the base frame to the cutterhead – electrical power, control, water and hydraulic lines, as well as methane sensor links – are contained within an armored cable that is automatically unwound from a large diameter drum on the base frame as each pushbeam is added. Resting in a groove in the top of the pushbeam, the cables and hoses are completely protected from falling roof rock, and are rewound onto the drum once an entry has been mined out and the cutter head is being recovered.
The power available on the Terex SHM launch vehicle is sufficient to allow the machine to mine entries of 305 m (1000 ft) in depth. In addition, the fact that (although they are firmly secured to each other) the pushbeams have vertical flexibility at each joint means that the system can work in seams that pitch and roll, with the cutterhead following the floor and roof of the seam and the pushbeams following its path regardless of the floor conditions. Indeed, the machine’s low ground-bearing pressure means that seams with soft floors can be mined as effectively as those with a hard stone base. This is a major achievement in the world of mining technology.
A New Set Of Opportunities
Highwall mining needs to be viewed as being part of the whole mining process. Conventional surface mining and highwalling have to go hand-in-hand to optimize the whole system, with surface mining creating enough highwall on a regular basis for the highwall miner to be fully occupied. This means that blasting, spoil-handling, bench-building and coal extraction have to be scheduled carefully if a mine is to get the full benefit of low-cost coal production from the mining technology system.
Looking at individual countries, the company has identified major highwall resource opportunities in several parts of the world, and has established an international sales team based in the Netherlands. In Russia, for example, the three machines already operating there have proved the viability of the mining technology, even in the harsh Siberian winter conditions. In China, Terex SHM appointed Bright Dynasty International Ltd as its agent in January 2006. Although its mining method is completely new in China, it is believed that contour and trench mining will provide huge opportunities for local mine operators in Inner Mongolia and in Shaanxi province, with 15 sites already identified as places where the system would work well.
What is vitally important is that, wherever in the world it may be, the conditions are right for highwall mining to be successful. The mining technology requires specific geological conditions, ideally but not necessarily a strong immediate roof to the seam, and a seam that is relatively level without major stratigraphic disruptions. There is, of course, the question of permitting, and this can be time-consuming at first, especially where local regulatory authorities have no previous experience with the highwall mining concept. Once the first set of permitting has been achieved, and the miner approved for use in a country, subsequent applications there will be much simpler.
Mobility A Key Factor
While the current generation of Terex SHM highwall miners weigh in at approximately 225 t for the launch vehicle, plus the weight of the cutterhead and pushbeams, the unit’s modular design means that transport and assembly are straightforward. The launch vehicle itself can be transported on just 11 trailers, with a 200 t capacity mobile crane preferred for assembling the modules onsite. Building up the machine typically takes less than four days, with Terex SHM using clearly identified couplings for its electrical and hydraulic systems, enabling connections between the individual modules to be completed quickly and accurately.
In addition, the modular construction means that the launch vehicle can just as easily be dismantled for transport to another site, once reserve recovery at one place has been completed, while it can also move from location to location under its own power or on special piggy-back transporter units that the company has designed. Neither is line power essential, since Terex SHM can also provide a stand-alone, track-mounted generator set for use in the more remote parts of a mine site. This flexibility means that the system is not tied in to individually large reserve areas, but can effectively compile small blocks into a much larger workable resource.
From a mining technical viewpoint, Terex SHM has already researched the implications for operating its machines in other markets than the US, with the principal factor for consideration often being the requirement to run on a 50 Hz power supply rather than the US 60 Hz system. The most recent highwall miner that Terex SHM has built already has international standard software coding, with most of the electronic systems on board being compatible with 50 Hz operation. While changes would still need to motors and gearboxes, for example, any country-specific conversions will not present a time consuming challenge.
Into The Future
Higher demand for electricity, and hence for coal, is providing opportunities for increased production worldwide with innovative mining technology systems such as highwall mining. In addition, the current strong demand for steel has opened up new opportunities for metallurgical coal production, and while to date most of Terex SHM’s customers have focused on thermal coal to sell on the utility market, several have specifically purchased systems for mining high-grade met coal. Most importantly, operators are now finding that purchase funding is more readily available as the financial community has become more comfortable with highwall mining’s track record as a profitable method of coal extraction.
While the company will be focusing on increasing its international business, the situation in the US is looking very good as well, with some of Terex SHM’s existing customers coming back for second or third machines, and new one entering the business as well. Research that the company has had done has shown that there is a resource of approximately 18,000 miles of highwall potential in the US that pre-dates the 1977 Surface Mining Control Reclamation Act, as well as resources that are being opened up during current surface mining. Terex SHM predicts it could increase its output capacity by approximately 70% without major investment, and would have the financial resources needed to continue with developing the technology and expanding its product line.
There is no doubt that, with highwall mining now a field-proven mining technology for safely producing low-cost coal, there are major opportunities for mining companies round the world to join what up to now has been a predominantly American club.
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