https://doi.org/10.15255/KUI.2006.032
Published: Kem. Ind. 57 (9) (2008) 425–433
Paper reference number: KUI-32/2006
Paper type: Professional paper
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Investigation of Adsorbed Gases Content in Coal Beds in Bosnia and Herzegovina

S. Mičević and J. Sadadinović

Abstract

Investigation of the gas fraction in coal beds in Bosnia & Herzegovina has been performed systematically since 1988. Gas in coal beds can be present in free or adsorbed form, and dissolved in water. Methods of investigation are based on the direct approach, according to which the gas fraction is determined in the undisturbed coal bed. The quantity of the adsorbed and free gas in the coal bed is directly proportional to the gas pressure. Dependence is hyperbolic. The quantity of the free gas in mining conditions is being determined by measurement of the desorption index (Δp2). The desorption index for the Srednjobosanski coal basin ranges to 1571 Pa, and the free gas pressure in this coal basin amounts up to 3.75 MPa. The desorption index for coal beds in “Kreka” and “Banoviće” coal basins has negative values, which means that the free gas fraction within the coal beds is negligible, while separation of adsorbed gases is diffuse. The free gas pressure in the mentioned coal basins is below 0.1 MPa. Adsorbed gases within the coal are connected by physical adsorption according to Langmuir’s isothermal adsorption curve. Langmuir’s quantities, for coal bed conditions, ranges as follows: am from 0.826 to 9.52 m3 t–1 pcs, and b from 6.65 • 10–3 to 0.247 MPa–1. Adsorbed gas within Miocene coal beds contains methane in amounts of 1.49 m3 t–1 čus CH4 and carbon(IV)oxide in amounts of 0.15 m3 t–1 čus CO2. Adsorbed gas within Pliocene coal beds, without methane, dominant is content of carbon(IV)oxide. The investigation of the gas content in coal beds of BiH conducted in this article reveal that the coal beds primarily contain methane, while others hydrocarbons such as ethane, ethene, propane, propene and butane are present sporadically in fraction below φ/10–6. Based on the investigation results conducted in this article, simple mathematical forms were obtained for quick calculation of the free gas quantity by measurement of the desorption index in mining, as well as calculation of the totally adsorbed gas in newly opened mining district and coal beds. This means that it is possible by a quick operative procedure to determine the immediate danger from gas outburst, and apply preventive measures in coal mining of still unexplored coal beds.

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Keywords

methane, adsorption, methane content, coal degasification