World Energy Resources | 2016

WORLD ENERGY COUNCIL | COAL
1. TECHNOLOGIES
Comprehensive electrification is essential for sustainable economic development and coalfired
power is seen as a key input to global electricity generation. This accounts for around
40% of total generation 2 . This section briefly explains extraction techniques, transportation
and handling, and plant technologies associated with coal-fired power generation.
EXTRACTION TYPES AND MINING TECHNIQUES
Coal, a product of organic sedimentation, occurs in seam-shaped deposits and must be
extracted selectively from the surrounding strata. Flat deposits with no faults are of major
commercial importance, which account for 50% of the world’s deposits. These have few
seams that are often of an even thickness and a wide horizontal spread. Flat, hardly
disturbed deposits of little depth lend themselves to extraction in opencast operations.
These mainly concern lignites, but most hard coal deposits from the Gondwana period on
the Southern continents are also of this type.
Sloping to steeply inclined or fault-containing coal deposits have a large number of
irregularly shaped seams in layer sequences that are often thousands of metres thick. The
seams are encountered at varying depths, with the deposits frequently marked by
complicated faults and disturbed conditions, so that extraction is mostly in underground
operations. They are generally of high rank; high quality coking coal, non-bituminous coals
and anthracites can usually be found in this type of deposit.
Depending on seam depth and formation and on the overlying loose or solid rock, the coal
is extracted either in opencast or underground operations. In underground mining, access
is by shafts and/or drifts while, in surface operations, the layer above the coal is stripped to
permit extraction of the exposed coal. Depending on seam thickness, the composition of
the overlying strata and surface use (e.g. inter alia, density of settlement). Opencast mining
is an economic proposition down to depths of 500m.
Hard coal extracted in underground operations is mined either from the surface via drifts or
shafts, depending on the depth of the deposit. In drift mining, the deposit is developed
using slightly inclined drifts equipped with conveyor belts. By contrast, coal deposits at
greater depths require shafts, which are also used for proper extraction. The coal is mined
either in room-and-pillar or in long-walling operations, with the latter being predominant.
In room-and-pillar mining, continuous miners drive extraction roads into the coal to cross at
right angles. Pillars are left standing in-between to support the overlying strata. This method
is associated with high extraction losses, since a considerable quantity of coal remains
underground. Transportation to the conveyor belts is often by shuttle car. A variant of the
2
Office of Chief Economist (2015) Coal in India
8