Adsorption Characteristics of Supercritical CO2on Coals

Research Project , Research Report 2003

Yoshito OSHIMA Environmental Science Study, The University of Tokyo
Sohei SHIMADA Institute of Environmental Study, Graduate School of Frontier Sciences, The University of Tokyo

Abstract

This paper presents the quantification of the adsorption capacity of coal samples using Carbon Dioxide at varying pressure and temperature conditions. The experimental method employed the Gibbs volumetric approach, carried out on both dry and moist coal sample. Experimental results indicated a slight decrease in the adsorbed amount within the vicinity of the critical point (i.e. 7-8 MPa) which was then followed by a monotonous increase on the adsorbed amount. Such a trend was apparent for isotherms at other temperature conditions, with the 35oC isotherm exhibiting the highest increase. Test results further showed that temperature increase and moisture content have negative effects on the sorption capacity especially at high pressure conditions. Comparison of pure CO2, N2 and CH4 isotherms also verified that CO2is much adsorbed on the coal’s surface relative to the other gases. Binary sorption measurement further indicated that increasing concentrations of either N2 or CH4 in a mixture causes the amount of adsorbed CO2to decrease, due to competition for adsorption sites

Keywords:

Supercritical CO2, Adsorption, Coal, Geologic Sequestration, Coalbed Methane