Stefanovych L.I., Feldman E.P., Mazur O.Yu. Adsorbed metane displacement by water vapour into closed cavityof coal-rock seams

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Parent Category: Geo-Technical Mechanics, 2023

Category: Geo-Technical Mechanics, 2023, Issue 165

Geoteh. meh. 2023, 165, 139-150

https://doi.org/10.15407/geotm2023.165.139

 

ADSORBED METANE DISPLACEMENT BY WATER VAPOUR INTO CLOSED CAVITY OF COAL-ROCK SEAMS

¹Stefanovych L.I., ¹Feldman E.P., ²Mazur O.Yu.

¹Branch for Physics of Mining Processes of the M.S. Poliakov Institute of Geotechnical Mechanics of the NAS of Ukraine, ²Technical University of Liberec

UDC 622.02:536.244

Language: English

Abstract. In gas-saturated coal mass, closed cracks and pores, in addition to free methane, contain methane, which is associated with adsorption centers on their internal surfaces. It is known that as a result of ingress of moisture in the form of water vapor into these cavities, adsorbed methane tends to pass from the adsorption layer into the gaseous phase. The purpose of this work is to find out how significant the increase in the pressure of gaseous methane in the closed cavities of the coal matrix is due to its desorption from the inner surface of the pores and/or cracks as a result of the penetration of moisture into them in the form of water vapor. The problem is solved under the assumption that an increase in the partial pressure of water vapor inside cracks and pores occurs as a result of filtration phenomena, i.e. relatively slowly compared to the adsorption-desorption processes occurring on the inner surfaces of the voids of the coal substance.
When calculating the excess partial pressure of methane, which arose as a result of its displacement from the adsorption layer by water molecules, the Langmuir approximation was used for the degrees of coverage of the adsorption layer by methane and water molecules, i.e. single-layer adsorption approximation. It is shown that in the case of macroscopic cavities of the order of 10^-3 m and more, this phenomenon is insignificant. However, for gas-filled closed cavities with a size of the order of micrometers or less and with an initial pressure of gaseous methane of the order of 1 MPa, the relative excess pressure of gaseous methane as a result of its desorption from the inner surface of closed cracks and pores can be tens of percent.
The scientific novelty of the work lies in the fact that, as far as the authors know, calculations related to the appearance of excess pressure of methane in closed cracks and pores as a result of its displacement by water vapor from the inner surface of closed voids of the coal matrix have not been carried out before. An increase in the pressure of gaseous methane inside closed cavities can lead to an increase in their size, in particular, this applies to cracks that are located near macroscopic voids.
Keywords: gas-filled cracks and pores, excess gaseous methane, desorption, inner surface of cavities, water vapor.

 

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About the authors:

Stefanovych Leonid Illich, Doctor of Physical and Mathematical Sciences (D.Sc.), Senior Researcher in Department of Physics of Coal and Rocks, Deputy Director of the Research Department, Branch for Physics of Mining Processes of the M.S. Poliakov Institute of Geotechnical Mechanics of the NAS of Ukraine, Dnipro, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it. .

Feldman Eduard Petrovych, Doctor of Physical and Mathematical Sciences (D.Sc.), Chief Researcher, Department of Physics of Coal and Rocks, Branch for Physics of Mining Processes of the M.S. Poliakov Institute of Geotechnical Mechanics of the NAS of Ukraine, Dnipro, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it.

Mazur Olha Yuriivna, Doctor of Philosophy (Ph.D.), Technical University of Liberec, Liberec, Czech Republic, This email address is being protected from spambots. You need JavaScript enabled to view it.

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