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Invasive filling of sealed headings and goafs in coal mines with methane - experimental and model re |
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Invasive filling of sealed headings and goafs in coal mines with methane - experimental and model research Author: S. Nawrat
The control and regulation of gaseous states in sealed headings and goafs is a very important problem in coal mines, especially in view of the dangers associated with endogenic fires and explosions of methane or fire gases. The compositions and concentrations of gases in sealed headings and goafs can be influenced by means of the following factors: natural factors -- the inflow of methane and carbon dioxide from the rock mass, internal factors -- the inflow and outflow of goaf gases and the inflow of the products of oxidation and coal burning in goafs, external factors -- the inflow of air caused by ventilation and methane drainage, external invasive factors -- the supply of inert gases or the mixtures of air and methane and the mixtures of goaf gases by means of installations. Because of its considerable effectiveness in limiting the hazards associated with fires and explosions of fire gases, the methane filling method has been used on numerous occasions in the coal mines belonging to the Jastrzębię Coal Mining Holding in the period 1978-1998. In order to acquire a full knowledge on the course of filling sealed headings and goafs with methane, experimental research was conducted in normal conditions in sealed areas of longwalls in the "Pniówek" and "Zofiówka" coal mines, which are characterized as containing the greatest absolute methane-bearing capacities in Poland. In the process of methane filIing, in sealed headings and goafs appeared non-explosive mixtures because of the excess of methane, which is extremely important for work safety. During the experiment the oxygen content was falling proportionately to the increase in methane concentration, which had a favourable influence on reducing the hazard of an endogenic fire in goafs. For designing a methane filling process for sealed headings and goafs. and especially for the evaluation of changes in gas concentrations and safety, a mathematical model has been developed. Such a mathematical model, supported by computer calculations, makes it possible to carry out simulations of the influence of particular parameters on the effectiveness of the process. Computer simulations generate additional information on changes taking place in the composition of gases in a given area that are not obtained by means of experimental research. It was shown experimentally that the application of the method of fiIIing sealed goafs and headings with methane enabled: to regulate within a specific range the composition and concentration of goaf gases, especially the concentration of methane and oxygen, to change under control the composition and concentration of gases - the air-methane mixture with a view to reducing its explosiveness, to lower the concentration of oxygen, and by this, to reduce considerably the possibility or speed of the development of the process of self-heating of coal er an endogenic fire. This paper is a contribution to the development of the scientific principles of the invasive filling of sealed headings and goafs with gases with a view to regulating the composition and concentration of goaf gases with respect to fire and explosion hazards, which consequently should improve work safety in coal mines.
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2011