抄録
It has been clarified that coal seams have a significant ability of CO2 adsorption more than CH4 as approximately double based on some experiments reported. By utilizing this property, coal bed methane gas can be replaced with CO2 injected and produced as a clean energy.
The demonstration project has already has been proceeded in North America, Europe and Japan. In Japan, coal seams, where mining is difficult economically, reserves about 18 billion ton, and it has been estimated that CO2 sequestration into the coal seams has a potential of about 6 trillion m3 (Koide and Yamazaki6)).
In this study, measurements of CO2 adsorption and gas permeabilities of coal specimens have been carried out in order to clarify sensitivities of coal specimen's size on CO2 adsorption capacity and permeability. Furthermore, adsorption behaviors against saturated CO2 water have been measured to simulate CO2 adsorption in a coal seam with high water saturation.
Based on measurement results, it was found that the region of about 10∼15mm in depth from a surface where gas supplied abundantly may work for CO2 adsorption, because the adsorption capacity of the core specimens show about 1 / 2 to 1 / 3 of ones of crushed samples 4mm in size. On the other hand, the adsorption capacity of 4mm crushed coal in the saturated soda water was around 80% of a coal specimen in dry CO2 gas.
