Energy aspects of CO2 sorption in the context of sequestration in coal deposits

Abstract

This paper summarises the results of experimental testing of carbon dioxide sorption on five coal samples. Sorption tests were done at the temperature 288, 298, 313 and 323 K, in the pressure range 0–5 MPa. The analysis of sorption isotherms and the effects of temperature on sorption capacity reveal that in the case of samples NR1, Pn, Tu, Be the temperature increase from 298 to 323 K led to 1.3-fold decrease of the sorption value. In the case of coal Th the decrease of sorption capacity was 3-fold. It appears that the analysis of maceral content plays a major role. In the case of coals, porosity is associated with the petrographic composition. The values of the isosteric heat of sorption and the work of expansion and desorption were derived for the investigated sorption systems. Test data reveal that for hard coals the isosteric heat is inversely proportional to the “reserve” of volumetric work—a major parameter triggering the sudden release of gas from the coalbed, thus enabling us to assess the potential risk involved in rapid unsealing of the coalbed.