Method |
Requirement |
Method of Interpretation |
Accuracy |
Country |
Method of Measurement |
Applicability |
Reference |
| Direct |
Cores |
Requires knowledge of gas emission laws |
Depending upon time lost, core quality and applicability
of gas emission laws.
±50%- ±20%
|
UK, USA, Australia |
Volumetric gas emission atmospheric pressure followed
by crushing |
Good from surface boreholes and doubtful from underground
boreholes, fractured cores etc. Degree of fracturing influences results |
Graham, (1937), Bertard, et al, (1970).
Belin, (1971)
|
| Direct |
Sampling of fractions |
Empirical |
? |
Poland |
Volumetric gas emission |
Existing mines |
Ettinger (1958) |
Indirect
(statistical)
|
Lumps of coal |
Statistical analysis of gas content of lumps |
± 20%, statistically measured values from
face samples are consistently higher |
UK |
Sample (30 – 40 mm size), collection at the
face and estimation of gas contents. |
For seams under mining, face sampling, applicability
to highly variable and high rank coals not proved |
|
Indirect
(adsorption isotherms)
|
Pressure measurement and sampling |
Direct readings for adsorption isotherms |
Depending upon pressure measurements and sampling
(~10-20%) |
Poland Russia, Australia, Germany |
Volumetric techniques and gravimetric techniques |
For seams under mining and seams lying above or below |
Lama and Bartosiewicz, (1982)
Aziz and Ming Li (1999)
|
| Indirect |
Proximate analysis of coal |
Empirical |
~30-100% |
Russia, USA
Poland
|
Chemical analysis |
New and existing mines |
Ettinger, (1958),
Kim (1977)
|
| Indirect |
Exhaust ventilation sampling |
Subtraction techniques |
± 20% |
Australia |
CH4 or CO2 gas analysis (%) |
Existing mines |
Lama, (1980)
Tarnowski (1972) |
| Indirect |
Sampling of exhaust mine air |
Empirical |
± 50% |
Germany,
USA
|
Volumetric gas emission |
Existing mines- general make of gas |
Noak, (1976) |
