28-06-2012, 05:44 PM
Introduction of Coal
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Introduction
A fossil fuel created from the remains of dead plants and animals about 300 to 400 million years ago
Formed during the Carboniferous Period
Presence of sulphur and oxygen makes it a combustible substance
Presence of carbon determines the blackness and energy contained in it
High-rank coals are high in carbon and therefore heat value, but low in hydrogen and oxygen. Low-rank coals are low in carbon but high in hydrogen and oxygen content.
Quality is determined by
varying types of vegetation
depths of burial
temperatures and pressures at those depths
length of time the coal has been forming in the deposit
Coalification is the degree of change undergone by coal as it matures from peat to anthracite
Coalification determines the physical and chemical properties of coal[1][2][3]
Coal Mining
Coal reserves are discovered through exploration activities
The process usually involves creating a geological map of the area, then carrying out geochemical and geophysical surveys, followed by exploration drilling
Mining Methods : The choice of mining method is largely determined by the geology of the coal deposit
Surface Mining : Also known as opencast or opencut mining
Is only economic when the coal seam is near the surface
Recovers a higher proportion of the coal deposit than underground mining as all coal seams are exploited - 90% or more of the coal can be recovered
Large opencast mines can cover an area of many square kilometres and use very large pieces of equipment
Underground Mining :Two main methods are room-and-pillar and longwall mining
Room & Pillar Mining :Coal deposits are mined by cutting a network of 'rooms' into the coal seam and leaving behind 'pillars' of coal to support the roof of the mine. These pillars can be up to 40% of the total coal in the seam
Longwall Mining :It involves the full extraction of coal from a section of the seam, or 'face' using mechanical shearers[2]
Analysis of Production
In 2010, world hard coal production increased by 6.8%, compared to 1.8% in 2009
It continued to be driven by growth in production from the non-OECD countries with 8.4%
Brown coal production in the OECD countries continued to decline while non-OECD brown coal production rose to a record level
Indonesia is the leader and accounted for over 75% of global incremental growth