Sorption and Micro-Scale Strength Properties of Coals Susceptible to Outburst Caused by Changes in Degree of Coalification

Abstract

Coals from the south-western part of the Upper Silesian Coal Basin have a strong outburst susceptibility. The objective of this study was to identify the influence of coalification degree on methane sorption and micro scale strength properties of 24 coals from Jastrzębie Zdrój. Coal samples showed a reflectance Ro between 0.98 and 1.25%. Sorption measurements were carried out by gravimetric method. Sorption capacities were determined at mean deposit temperature of 35 °C. Using the unipore model and solution of Fick’s second law, the effective diffusion coefficients of methane in the studied coals were obtained. The Vickers method was used to study the microhardness and the modulus of elasticity. It has been shown that the increase in the coalification degree reduces the sorption capacity of coal and also reduces the rate of methane emission. Coals the most susceptible to outbursts, were the most brittle. With the increase in Ro, the methane seam pressure p increased as well as desorbable methane content DMC, both due to the reduction in the sorption capacity of coal. The increased dp index is a warning sign indicating an increased total methane content of coal seam, an increased seam pressure or an alternation of coal structure.

Influence of Depth on CO2/CH4 Sorption Ratio in Deep Coal Seams

“…Research by the author and other researchers showed a reduction in the sorption capacity of carbon in relation to CH 4 [17]. Both in the case of sorption capacity and the effective diffusion coefficient, the dominant factor influencing the nature of the variability of the mentioned parameters with depth was the degree of coalification [17][18][19]. In the depth range from approximately 680 m to 860 m, the impact of temperature sorption properties was small compared to the coalification degree of the coal substance.…”

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

“…Based on the analysis of the literature, it can be stated that the petrography of coal has a significant influence on the course of sorption processes in its structure. The literature describes the dependence of the maceral composition and the degree of coalification on the course of diffusion and sorption processes [19,21,22,31,48,[56][57][58]. The diffusivity of hard coal is related to both pore size distribution and porosity in terms of macroscopic equation.…”

Application of Petrographic and Stereological Analyses to Describe the Pore Space of Rocks as a Standard for the Characterization of Pores in Slags and Ashes Generated after the Combustion of Municipal Waste

“…In the oil and gas industry, this data is required, among other things, for assessing the rocks' capacity to accumulate crude oil or natural gas [2,3]. The porosity of rocks is a crucial parameter in geological and geophysical studies [4], aiding in determining the structural composition and properties of rocks [5] and describing the adsorption parameters of rocks [6][7][8][9]. Porosity analyses are instrumental in hydrogeological issues, such as the ability of groundwater to move in underground water reservoirs, water resource management, and source water protection [10,11].…”

“…Basic petrographic analyses of rocks are usually conducted using polarizing microscopes [8,25,34,35]. To expand the methodology, X-ray analyses, SEM, EDS, etc., are also employed.…”