Initial Rate of Gas Emission from Coal as One of the Indices of Outburst Hazards in Coal Seams

摘要

Comminution of coal also has another feature that promotes sudden outbursts of coal and gas. Before the gas is emitted from the coal and becomes capable of performing work, it must expend a part of its potential energy on migration inside the coal fragment to an outlet on the surface. It follows that the initial intensity of gas emission from the coal fragments and the force generated by the expanding gas depend on the degree of comminution of the coal and on the resulting total surface of coal giving off gas; secondly, this itself affects the amount of energy that may be utilized for the sudden outburst. In addition to this, the intensity of the initial gas emission is determined by the pressure drop of the gas (inside and outside the coal fragments), the natural gas content of the coal, the gas permeability of its substance, the viscosity of the gas, and the temperature of the process. It follows that determination of the force that may be generated by the gas in the initial moment of a sudden outburst of coal and gas is a complex problem that still awaits solution, but it is evident that the force is determined by the complex aggregate of factors indicated, the parameters of which are mutually interdependent. As it is not at present theoretically possible quantitatively to include all the inter-relationships, it is necessary in practice to use empirically established inter-relationships. In order to simplify matters and to be able to obtain quickly the results of a determination of the gas-output capability of coal, an express method has been developed for detecting coals with an outburst-prone structure, and also for determining the characteristics of coals, separated from the massif as a result of dynamic phenomena. The latter is for the diagnosis of sudden outbursts, which is important for the investigation of mine disasters. (ERA citation 10:009527)