Studies on Swelling of Coal in case of CO_2 Sequestration into Coal Seam

Abstract

Swelling behaviour of coal with CO_2 has been investigated. The expansion of coal matrix was observed with a digital microscope equiped high pressure cell. Pulse ^1H-NMR spectroscopy was used with the aim to evaluate the change in macromolecular structure of coal. The expansion ratio of coal increases with increase in CO_2 pressure. The signal of coal sample is deconvoluted into two components, that is, relatively slowly decaying component, L1 and rapidly decaying component, G. In a similar manner as the expantion ratio, the fractional intensity and the T_2 value for L1 component increases in proportional to the CO2 pressure. The results indicate that the expantion of coal matrix might be caused by swelling of coal molecules with CO_2.