Microporosity in Alberta Plains coals

The nature of porosity in 11 Alberta Plains coals is scanned using different characterization techniques, namely, gas adsorption, helium and mercury displacement, and mercury porosimetry. Surface areas calculated from carbon dioxide adsorption at 25°C (varying between 75 and 506 m²/g) are consistently higher than those calculated from nitrogen at −196°C (varying between 1 and 9 m²/g). The samples from Paskapoo deposits have slightly higher surface areas as compared to samples from Horseshoe Canyon deposits. The carbon content in the tested coals (73.4 to 76.8%) is too narrow of range to determine the influence of this parameter on surface area and porosity.Total pore volumes are measured in the range 1.2 to 3000 nm and then divided into macropores (30 to 3000 nm), transitional pores (1.2 to 30 nm) and micropores (less than 1.2 nm). Almost all the surface area in coals is located in the micropores. Coals vary widely in their total pore volumes and porosities range between 9.5 and 22.3%. Percent pore volume contained in micropores varies between 29.5 and 75.9, in transitional pores between 1.1 and 20.5 and in macropores between 18.5 and 50.0.