Pore Size Distribution and Accessible Pore Size Distribution in Bituminous Coals

Published

October 1, 2012

Author(s)

Richard Sakurovs, Lilin He, Yuri B. Melnichenko, Andrzej P. Radlinski, Tomasz Blach, Hartmut Lemmel, David F. Mildner

Abstract

Contrast-matching ultra-small-angle neutron scattering (USANS) and small-angle neutron scattering (SANS) techniques have been used to determine the fraction of the pores that are inaccessible to deuterated methane, CD₄, in 23 coals over the range of pores sizes between 10 and 5000 nm at ambient temperature. The coals range in rank from subbituminous to bituminous: three from the eastern US, two from Poland, one from New Zealand and the rest from the Sydney and Bowen basins, Australia. In some coals most of the small (10nm) mesopores are inaccessible to CD₄ on the time scale of the measurement (30min-16hours). This suggests that in these coals a considerable fraction of inherent methane may be trapped for extended periods of time, thus reducing the effectiveness of methane release from (or sorption by) these coals. For the Australian coals the extent of in accessibility at the 10-50nm size scales increases linearly with increasing vitrinite content; mesopores in inertinites appear completely accessible to CD₄, whereas the mesopores in the vitrinite are about 70-80% inaccessible. The relationship is not rank dependent. In contrast, inertinites of the US or Polish coals behave differently: the appear to be as inaccessible to CD6d4^ as their vitrinites ¿ 80% inaccessible. With increasing pore size, pore accessibility generally increases. This difference in inertinite behavior may explain why empirical relationships between fluidity and coking properties developed using Carboniferous coals do not apply to Australian coals.

Citation

International Journal of Coal Geology

Volume

100

Pub Type

Journals

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Keywords

contrast matching, deuterated methane, inaccessible pores in coals, methane extraction from coals, pressure cell measurements, scattering length density, small-angle neutron scattering, ultra-small-angle neutron scattering

Citation

Sakurovs, R. , He, L. , Melnichenko, Y. , Radlinski, A. , Blach, T. , Lemmel, H. and Mildner, D. (2012), Pore Size Distribution and Accessible Pore Size Distribution in Bituminous Coals, International Journal of Coal Geology, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=911166 (Accessed July 26, 2024)