CO2 sorption properties of selected lithotypes of lignite from Polish deposits

Sorption studies, to determine the CO2 sorption capacity of coal, were carried out using eight ortho-lignite samples of different lithotypes, to investigate the possibility of CO2 storage in lignite deposits. Equations determining a number of parameters and indicators used to delineate the experimental data and to differentiate the samples examined include: Langmuir isotherms; the Dubinin-Radushkevich (DR) equation that describes the theory of volume filling of micropores; and the Brunauer, Emmett and Teller (BET) equation used to calculate the volume and surface area of a monolayer. The results obtained were compared with the petrographic composition and ultimate and proximate analysis of lignite. There is a large correlation between sorption and petrographic composition, a positive impact of the Gelification Index on the sorption process and a clear relationship between the sorption (Langmuir and DR) and ash content. The best CO2 sorption properties were found for xylo-detritic and detro-xylitic lignites. Based on the tests carried out, a preliminary assessment of the suitability of lignite for CO2 storage can be made.