Analysis of the Influence of Coal Petrography on the Proper Application of the Unipore and Bidisperse Models of Methane Diffusion

Tomasz Schlieter,Katarzyna Godyń,Marcin Karbownik,Jerzy Krawczyk,Jiří Ščučka

doi:10.3390/en14248495

Abstract

The analysis of phenomena related to gas transport in hard coal is important with regard to the energetic use of coal bed methane (CBM), the reduction of greenhouse gas emissions to the atmosphere (CO2) and the prevention of natural hazards such as methane hazards and gas and rock outbursts. This article presents issues concerning the feasibility and scope of applying the unipore and bidisperse diffusion models to obtain knowledge concerning the kinetics of methane sorption and its diffusion in the carbon structure, depending on its petrography. Laboratory tests were carried out on coal samples which varied in terms of petrography. Quantitative point analyses were carried out, based on which content of groups of macerals was determined. The degree of coalification of coal samples was also determined based on measurements of vitrinite reflectivity R0 and the volatile matter content Vdaf. Sorption kinetics were also investigated, and attempts were made to adjust the unipore and bidisperse models to the real sorption kinetic courses. This allowed the identification of appropriate coefficients controlling the course of sorption in mathematical models. An attempt was also made to assess the possibility of applying a given model to properly describe the phenomenon of methane sorption on hard coal.

Highlights

Global economic development and the growth of civilization itself lead to greater consumption of electricity, resulting in a constant increase in the demand for it [1]
As a result of international agreements concluded under the United Nations Framework Convention on Climate Change (UNFCCC), countries are required to reduce greenhouse gas (GHG) emissions, especially CO2, which has resulted in increased demand for “clean energy” sources
On the basis of the studies carried out, it has been stated that the mechanism of the occurrence of processes of sorption and diffusion of methane on hard coal is related to the petrography of coal, in particular to the maceral composition and the degree of coalification

Summary

Introduction

Global economic development and the growth of civilization itself lead to greater consumption of electricity, resulting in a constant increase in the demand for it [1]. There is a growing awareness of the fact that methane molecules have a much greater impact on the greenhouse effect than carbon dioxide. This justifies research into the processes determining its emission into the atmosphere [5,6]. Coalbed methane (CBM) is a gas of natural origin, which was formed as a result of processes of conversion of organic matter into coal [7]. It occurs in coal seams mainly as adsorbed gas and in smaller amounts, as free gas. The unit methane content in coal seams reaches several cubic meters per ton of coal (m3 CH4 /t), which in the scale of the entire Upper Silesian Coal Basin (GZW), results in trillions of cubic meters of gas [11,12]

Methods

Results

Conclusion