Page 22 - Advanced Mine Ventilation

Underground Coal Mine Atmosphere 5

Table 1.2 Global Coal Production

a
Country Annual Production (Metric) t (2013)
China 3561
United States 904
India 613
Indonesia 489
Australia 459
Russia 347
South Africa 256
Germany 191
Poland 143
Kazakhstan 120

a
1 metric ton ¼ 1.1 short tons.
Adapted from World Coal Statistics.

However, most of the coal deposits are deeper than 300 feet and thus are mined by
underground mining methods. Mine shafts or inclines are dug to access the coal seam.
A series of tunnels are driven to create a large block of coal, called a longwall panel,
that is mined by machines. Coal is transported out of the mine by conveyor belts and
hoists (Fig. 1.1).

1.2 Underground Mine Atmosphere

The underground mine atmosphere has many pollutants. They are mostly solids (respi-
rable dust) and gases (such as methane, carbon dioxide, etc.). Liquid pollutants, such
as mists, are not an issue in the mining industry.
The provision of an adequate air environment to promote health, safety, and com-
fort of mine workers has always been and will continue to be a prime requisite for suc-
cessful coal mining operations. Although the definition of an adequate environment
varies from country to county, it generally means the provision of sufficient circulating
air, often at specified velocities, to maintain at least 19.5% oxygen in the working
areas; concentrations of solids (respirable dust) and gaseous pollutants, such as
methane, carbon dioxide, etc., below specified limits; and heat and humidity below
specified limits. Because most coal mines are shallow (less than 3000 ft deep), temper-
ature and humidity control is not warranted. It is a concern only in deep metal mines
(up to 15,000 ft) for copper, silver, and gold.
Table 1.3 shows the maximum allowable concentrations of these atmospheric pol-
lutants in US underground coal mines [4].