Dawson Complex Queensland, Australia

The Dawson Complex, located 185km southwest of the Queensland port of Gladstone, incorporates several earlier coal-mining operations in the area, including the Moura mine. Coal has been mined at Moura since 1961, making this one of the longest-established operations in central Queensland. Originally operated by BHP Mitsui Coal Pty Ltd, the mine changed hands in mid-1999 when the US-based company, Peabody, bought a 55% holding from BHP. Since 2001, ownership has changed again, firstly to Rio Tinto's subsidiary, Coal and Allied, after which Mitsui invoked its pre-emptive rights to buy the whole operation before selling a 51% share to Anglo Coal in mid-2002.

Both surface and underground mining has taken place, as well as a highwall mining system developed jointly by BHP and the US equipment supplier, Mining Technologies. Moura also hosts Australia's first commercial coal-bed methane recovery operation.

Employing around 470 people, Moura currently has the capacity to produce 4.5Mt/y of soft coking coal and 2.5Mt/y of thermal coal. In late 2004, Anglo Coal and Mitsui announced that they would be combining an expanded Moura and the adjacent Dawson and Theodore deposits into the Dawson Complex mine, which will have a capacity of 7.1Mt/y of coking coal and 5.6Mt/y of power-station fuel. The Dawson project, which involves the expansion of the existing Dawson operations to include a Dawson North and Dawson South mine, is scheduled for commissioning in 2007 at a cost of some US$835m.

GEOLOGY AND RESERVES

Moura lies in the Baralaba Coal Measures on the south-eastern flank of the Bowen Basin. The mine produces coal from permian-age reserves contained in five major seams that average 3.5–4.0m in thickness, and dip at 5–12°.

As of the end of 2005, the Dawson Complex had measured and indicated resources of some 565Mt, of which some 490Mt were accessible only by underground mining.

MINING METHODS

Since 1994, all production at Moura has been from its surface operation. A major methane-related accident closed the No.2 underground mine in August of that year, and BHP then focused on evaluating alternative methods of recovering at least part of the substantial underground coal reserves.

After blasting, primary waste stripping in the opencasts is carried out by four draglines: a Marion 7901 equipped with a 30m³ bucket, a 47m³ Bucyrus-Erie (B-E), and two Marion 8200s equipped with 57m³ and 72m³ buckets

Primary coal loading equipment is a fleet of six Cat 992C wheel loaders, equipped with 20t-capacity buckets, that work with seven Cat 776, 135t-capacity bottom-dump haulers and one Cat 776C, 160t-capacity machine.

HIGHWALL MINING

Moura's highwall mining system was commissioned in mid-1997, BHP having estimated that by 2012 there would be 127Mt of highwall reserves at the mine. Since over 80% are held in seams that dip steeper than 6°, conventional highwall mining equipment cannot operate satisfactorily.

The initial system used involved a modified Mining Technologies Addcar highwall mining system, with the coal being cut by a remotely controlled Joy 12CM12B continuous miner. A total of 29 Addcars gave a maximum hole depth of 370m, with a cut profile of 3.6m wide by up to 3.7m high. The maximum miner output was 720t/h, equivalent to 1.6Mt/y of run-of-mine coal.

When Peabody acquired the mine, it introduced a different type of highwall mining system, using the Archveyor concept developed by its US coal-mining competitor, Arch Coal. Relying on a series of interconnected transport modules that can 'walk' into a heading, this is also equipped with a cutter-head derived from a conventional continuous miner. There are now two units in operation at Moura.

COAL PREPARATION AND TRANSPORT

Raw coal from the opencasts and from the highwall mining operation is transported 16km by an overland belt conveyor to the preparation plant area. Here, crushing in three, 2,000t/h-capacity rotary breakers is followed by transfer of the crushed coal to the prep plant itself, where a multi-circuit (dense medium, spirals and flotation) washing system is used to give coarse, medium and fine coal products.

Washed coal is railed to Gladstone, and is shipped out through both the Barney Point (owned by BHP Mitsui Coal) and R G Tanna coal terminals.

COAL QUALITY

Coking coal quality parameters for Moura KCOAL:

• Total moisture: 10.5%
• Volatile matter: 32.0%
• Ash: 8.3%
• Sulphur: 0.42%
• Crucible swelling number: 6

Quality parameters for Moura thermal coal:

• Total moisture: 10.5%
• Volatile matter: 30.5%
• Ash: 10.0%
• Sulphur: 0.50%
• Heating value: 30.35MJ/kg (13,050BTU/lb)