Mining Coal

Hazelwood Mine – Dredgers

The Hazelwood mine covers a very large area - over 800 hectares. The perimeter of the mine is over 14.5 kilometres. The mine is about the size and depth of Uluru (Ayers Rock), though it would be a better fit if you turned the great rock upside down.

The coal is covered by overburden which is made up of clay, gravel and top soil. This must be removed before the coal can be mined, although the top soil is reclaimed for rehabilitation work. The average depth of overburden is 18 metres and the average depth of the coal is around 100 metres although in many places the coal depth can vary.

The key to mining the coal is the bucket-wheel excavator or “dredger”, the huge digging machine which eats into the walls or batters of soft coal. The dredger digs and then deposits the coal on the first of many conveyors which transport the coal to the boilers.

The dredger is an enormous and powerful machine. But it is easy to overlook the fact that it is also a precision instrument. The dredgers’ operations are guided by lasers. In fact, this was one of the world’s first applications of laser technology in industry. Lasers provide reference for the path of the bucketwheel and ensure that digging is efficient and minimises waste.

IPR – GDF SUEZ has four dredgers and conveyors systems on different levels in the coal mine at Hazelwood. Three are generally scheduled to dig coal with two supplying coal to the power station and one removing overburden. The fourth dredger is spare in case of breakdown.

Hazelwood Mine – Conveyors

Each dredger supplies coal to a system of conveyor belts which carry the coal out of the mine. IPR – GDF SUEZ has over 50 kilometres of conveyors at Hazelwood, more than enough to stretch from Melbourne’s central business district to Dandenong, Victoria.

The conveyor system is capable of carrying in excess of 2,500 tonnes of coal per hour. On the journey to the boiler the coal is carried by conveyor to the slot bunker which provides reserve coal storage of up to 25,000 tonnes.

From there the coal is screened, crushed and carried up to smaller bunkers closer to the boilers. Each of these conveyor systems contains electronic weighers, electro-magnets and metal detectors to find foreign objects in the coal.

Finally the coal is pulverised into fine particles which can be blown into the boiler. This allows for rapid and very hot combustion.

 Digging at the coal face

Delivering the coal to the station