Contrasts in methane sorption properties between New Zealand and Australian coals

High pressure microbalance investigations have produced results for both New Zealand and Australian coals which show fundamental differences in their methane sorption properties. New Zealand high volatile bituminous C rank coals have a methane adsorption capacity of 38 cc/g( dan which decreases to a minimum of 23 cclg( dan at medium volatile bituminous rank and increases to 31 cc/g( dan at low volatile bituminous rank. Vitrinite-rich coal samples from Australia display a similar trend, but, the methane adsorption capacity is approximately 8 cc/g higher than for New Zealand coals at low volatile bituminous rank increasing to 20 cc/g higher at high volatile bituminous A rank. From these differences it is implied that New Zealand coals contain a lower proportion of microporosity than Australian coals, most likely due to the presence of volatile components blocking the micropore structure making them unable to sorb as much methane.