A study of laboratory testing and calculation methods for coal sorption isotherms

• Published in: Journal of coal science & engineering, China Vol. 19; no. 2; pp. 193 - 202
• Main Authors: Zhang, Lei, Ren, Ting-Xiang, Aziz, Naj
• Format: Journal Article
• Language: English
• Published: Heidelberg China Coal Society 01.06.2013
• Subjects: Earth and Environmental Science; Earth Sciences; Geochemistry; Geology; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Mechanical Engineering; 吸附等温线; 地质构造; 实验室; 测试设备; 煤层气; 瓦斯抽放; 计算; 资源评估; coalbed methane; calculation method; coal mine gas; apparatus; gravimetric method; sorption isotherm; volumetric method
• ISSN: 1006-9097; 1866-6566
• DOI: 10.1007/s12404-013-0214-4

Measurement of the volume of gas adsorbed per unit mass of coal with increasing pressure at a constant temperature produces an isotherm that describes the gas storage capacity of this type of coal. The accurate testing and interpretation of coal sorption isotherm plays an important role in the areas of coal mine methane drainage, coalbed methane （CBM） reservoir resource assessment, enhanced coalbed methane （ECBM） recovery, as well as the carbon dioxide （CO2） sequestration in deep coal seams or similar geological formations. Different coal sorption isotherm testing apparatus and associated calculation methods are critically reviewed and presented in this paper. These include both volumetric and gravimetric based methods, as well as experimental sorption tests with confining stress and direction sorption methods. The volumetric techniques utilise experimental apparatus with sample cell and injection pump and that with both sample cell and reference cell. Whilst the gravimetric approachesinclude methods with sample cell and suspension magnetic balance and that with both sample cell and reference cell. Different testing methods are compared and discussed in this study. A unique in-house-built coal sorption isotherm testing apparatus at the University of Wollongong was presented together with the calculation method, procedures and experimental results. The isotherm results can be calculated by both Soave-Redlich-Kwong （SRK） equation and calibration cure methods which can be used directly to convert the volume of adsorbed gas in different test conditions to standard condition （NTP）.