Page 296 - Advanced Mine Ventilation

Postmining Degasification of Coal Mines 273

Figure 16.5 Methane drainage with cross-measure boreholes.

boreholes in roof and floor can be drilled at varying inclinations depending on the de-
gree of gassiness. Drill sites are typically 80 ft apart. These holes are then manifolded
to a larger pipeline system, and gas is withdrawn using a vacuum pump. Vacuum pres-
sures applied vary from 4 to 120 in. of water gage. The amount of methane captured by
the drainage system expressed as a percentage of total methane emission in the section
varies from 50 to 90%. Some typical data from British mines are given by Kimmins [6]
and shown in Table 16.3.

Table 16.3 Methane Capture Ratios for Cross-Measure Borehole Method

Methane Capture Ratio (%)
Specific Methane
3 a
Mine Emission (ft /ton) Section Mine
Ashley Green 3200 60 38
Haig 3000 59 20
Parkside 2800 61 42.6
Point of Ayr 5700 68 47.7
Sutton Manor 3300 70 40.0

a
This is the total methane emission from a mine divided by the tonnage mined every day. These are highly gassy mines.