Analysis of coal structure in the aspect of gas content.
Tadeusz Niezgoda, Ewelina Małek, Danuta Miedzińska
Vol. 30, no. 1 (2013), s. 169-178, 
The problem of methane existence in coal beds has been known for many years. It was and still is a danger to coalminers. The aim of the research presented in the paper is to show and assess the porosity structure (especially micro and nanoporosity) in accordance to the dimensions of carbon dioxide particle. The characteristic surface morphology of the sample and the disclosure of carbon porous structure was obtain using the scanning electron microscope (SEM). The presented study of the coal microstructure is a part of the coal demethanation method with the use of liquid CO2, that was proposed by Military University of Technology. Based on the results of laboratory tests may be noted that the analyzed coal has a granular structure. It is also visible that that the structure is stratified, and there is a lot of cracks and free space between grains, which can accumulated methane in coal structure. The nanoporosity of the coal grains was observed during SEM study. The sizes and shapes of pores are miscellaneous. However the dimension of 62-300 nm allow to draw a conclusion, that the nanopores can contain a few particles of CH4 (4 A), which can be released by the CO2 particle (2.54 A). Finally, on the base of presented research it can be concluded that the method of coal demethanation with the use of CO2 can be economically and ecologically effective, and can increase the miners safety.