Page 62 - Advanced Mine Ventilation
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Estimation of Ventilation Air Quantity 45
Figure 4.1 A typical modern coal mine layout.
year. Economy of size drives the cost of production further down, but the capital cost
goes up. A very large coal mine may cost $500 million to open up today and produce
12 to 15 million tons of coal per year.
4.2 Methane Emissions
It is safe to assume that all coal seams are gassy because coal and methane in coal are
syngenetic in origin; that is, they are derived from the same plant material. The gas
content of coal seams varies depending on the rank of coal and the depth of coal
seam. Globally, coal seams can be divided into three categories depending on the depth
3
and their gas contents in ft /ton as shown in Table 4.1.
Table 4.1 Gassiness of Coal Seams [1]
3
Category Depth (ft) Gas Content (ft /ton)
Mildly gassy 500 or less 100 or less
Moderately gassy 500e1500 100e300
Highly gassy 1500e3000 300e700
