A study of the factors that affect the permeability of coal

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Virginia Tech


The problem of degasification of coal beds is important because it is desirable to reduce the inflammable gas in coal mines as well as to recover economically the gas for use as a fuel. Permeability of coal is defined as a measure of the ease with which a gas flows through coal under a given pressure gradient, and it is of practical importance in the problem of degasification, The factors that affect the permeability of coal are also important in order to develop a more effective way of degasification. This study is concerned with the factors that affect the permeability of coal.

Some of the major factors which affect the permeability of coal are the property of coal, properties of the natural coal gas, physical and chemical correlations between the coal and the gas, overburden pressure, and direction of the gas flow and other factors. In the case of these factors it is usually necessary to assess their effects in a qualitative way rather than in a quantitative one. For this reason, it would be impossible in the time allotted to this paper to present anything more than a brief discussion of their interrelationships.

By experiment conducted for this thesis, it has been determined that (1) the permeability of coal differs from place to place, (2) the permeability of coal may or may not differ from bench to bench in the bed of a given location, (3) the permeability of dry coal does not differ significantly from that of wet coal, and also (4) in general, no significant difference in permeability was found when the gas flowed parallel to the coal bedding and when it flowed perpendicular to the coal bedding.