How is longwall mining done?
The basic idea of longwall mining was developed in England in the late 17th century. Miners undercut the coal along the width of the coal face, removing coal as it fell, and used wooden props to control the fall of the roof behind the face. This was known as the Shropshire method of mining.
What does longwall mining involve?
Longwall mining of coal is a high production and high productivity method, employing sophisticated electrical, mechanical, and hydraulic systems, as well as computer-based monitoring and control systems. Most modern (coal) longwall faces are semi-automated.
How long is a longwall miner?
Longwall mining machines are about 800 feet (240 meters) in width and 5 to 10 feet (1.5 to 3 meters) tall. Longwall miners extract “panels” – rectangular blocks of coal as wide as the mining machinery and as long as 12,000 feet (3,650 meters).
Why longwall mining is not used in India?
Among the difficulties faced by India’s longwall producers are strata control problems, inadequate underground clearance equipment, prohibitive cost of capital, poor development drivage rates, and lack of planning.
How much does a longwall cost?
Today, longwall has evolved into the most modern, efficient, and safe mining technique going. It is also the most expensive. A single system designed to clear out a 600 -by-6,000-foot seam that is 5 feet thick costs from $6 million to $8 million, generally limiting its use to the larger coal companies.
What is the best conditions suitable for longwall method?
This technique is ideally suited to deep, very gassy coal seams with low to medium permeability (1–10 md). Its effectiveness may be reduced if the coal seam is deeper than 4000 ft where the coal seam permeability is generally less than one microdarcy.
What equipment is used in longwall mining?
Joy complete longwall systems represent the ultimate solution for high-production longwall mining. Joy incorporates best-in-breed shearers, roof supports, face conveyors, stageloaders, crushers, and mobile belt tail pieces to deliver a complete longwall system that is in a class of its own.
Why Longwall mining is not applicable in every Indian coal seam?
The majority of longwall panels installed in the India could not achieve the desired targets due to lack of knowledge of geo-mining conditions, non-available of spared parts, dynamic loading on the powered support and under rated shield support selection.
Where is longwall mining used?
Most longwall mining occurs in the coal basins of New South Wales and Queensland. Mining depths are often between 200 and 600 metres below ground surface in New South Wales, and usually at a shallower depth in Queensland.
How much does a coal mining machine cost?
A single longwall machine of this size costs $70 million, but at current coal prices, it pays for itself in about two months. Foundation plans to install a second one in the Emerald mine. All this production technology helps keep coal cheap.
How does longwall mining compare to room and pillar mining?
Room-and-pillar mining generally is not economical at such depths because the very large pillars are required to support the roof, which significantly reduces the amount of coal that can be recovered. Longwall mining is well suited to deep coalbeds because there is no need to support the roof.
What is the best condition suitable for longwall method?