Minieiev S.P., Prusova A.A., Yanzhula O.S., Sachko R.M., Minieiev O.S. Calculation of the changing cofficient of the folmerov diffusion of methane desorped from coal in the face area of the coal layer at great depths

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Parent Category: Geo-Technical Mechanics, 2021

Category: Geo-Technical Mechanics, 2021, Issue 156

Geoteh. meh. 2021, 156, 36-45

https://doi.org/10.15407/geotm2021.156.036

 

CALCULATION OF THE CHANGING COFFICIENT OF THE FOLMEROV DIFFUSION OF METHANE DESORPED FROM COAL IN THE FACE AREA OF THE COAL LAYER AT GREAT DEPTHS

¹Minieiev S.P., ¹Prusova A.A., ²Yanzhula O.S., ²Sachko R.M., ³Minieiev O.S.

¹Institute of Geotechnical Mechanics named by N. Poljakov of NAS of Ukraine, ²Private Joint-Stock Company «Donetskstal», ³National Technical University "Dnipro Polytechnic"

UDC 622.411.322: 533.15     

Language: Ukrainian

Abstract. An algorithm for calculating the Volmer diffusion coefficient of methane adsorbed in coal in the bottomhole zone of the formation to the maximum reference pressure is developed with taking into account the change in the Folmer porosity and the size of the space of this zone. The algorithm is based on the using of the exponential law of compression, which describes the structural changes in the reference pressure of the coal seam. This allowed us to determine the diameter of the Folmer pores in the study area depending on its stress state. Based on these data and the calculation of the exponential nature of the change in porosity, the regularity of the Folmer diffusion in the bottomhole region at its fixed length and initial porosity of coal is established. By using a method of step-by-step approximating the solution of this problem for different parameters, the research results are generalized to the existing ranges of change in the Folmer porosity of coal and the size of the bottomhole region of reference pressure in mining conditions at great depths. The functional approximation dependence is established, which allows to perform calculations of the Volmer diffusion coefficient of methane desorbed from the coal layer, with simultaneous change of two parameters - initial porosity of coal and distance between the bottom to the maximum reference pressure zone. Calculations showed that when reference pressure approached its maximum at a distance of up to 10 m from the face the coefficient of Folmer diffusion of methane in coal decreased slightly. In this case, there is a strong dependence of the Volmer diffusion coefficient on the diameter of the Folmer pores in the virgin coal layer. For example, when this diameter increases twofold - from 8 А to 16 А at the distance of 20 m from the face to a maximum reference pressure, the coefficient of Folmer diffusion increases by 1.5 times. That is, Folmer's diffusion is the most intensive in the disturbed zones of the coal layer. This can be the area of maximum reference pressure, if there is a zone of disintegration, or in that part of the face zone, which is characterized by the developed system of fractures.
Keywords: adsorbed methane, coal layer, face zone, Folmer pores, Folmer diffusion coefficient.

 
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About the authors:

Minieiev Serhii Pavlovych, Doctor of Technical Sciences (D.Sc.), Professor, Head of Department of Pressure Dynamics Control in Rocks, Institute of Geotechnical Mechanics named by N. Poljakov of National Academy of Sciences of Ukraine (IGTM NAS of Ukraine), Dnipro, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it.

Prusova Alla Andriivna,Candidate of Technical Sciences (Ph.D), Senior Researcher in Laboratory of Structural Research of Rocks, Institute of Geotechnical Mechanics named by N. Poljakov of National Academy of Sciences of Ukraine (IGTM NAS of Ukraine), Dnipro, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it.

Yanzhula Oleksii Serhiiovych, Candidate of Technical Sciences (Ph.D), Director of Perspective Development and Investments, PJSC “Donetskstal”, Pokrovsk, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it.

Sachko Roman Mykolaiovych, Master of Sciences, Chief Engineer of Pokrovske Mine Management, PJSC “Donetskstal”, Pokrovsk, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it.

Minieiev Oleksandr Serhiiovych, Candidate of Technical Sciences (Ph.D), Associate Professor of National Technical University "Dnipro Polytechnic", Dnipro, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it.

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