Estimation and modeling of coal pore accessibility using small angle neutron scattering

Rui Zhang, Shimin Liu, Jitendra Bahadur, Derek Elsworth, Yuri Melnichenko, Lilin He, Yi Wang

Research output: Contribution to journalArticlepeer-review

74 Scopus citations

Abstract

Gas diffusion in coal is controlled by nano-structure of the pores. The interconnectivity of pores not only determines the dynamics of gas transport in the coal matrix but also influences the mechanical strength. In this study, small angle neutron scattering (SANS) was employed to quantify pore accessibility for two coal samples, one of sub-bituminous rank and the other of anthracite rank. A theoretical pore accessibility model was proposed based on scattering intensities under both vacuum and zero average contrast (ZAC) conditions. The results show that scattering intensity decreases with increasing gas pressure using deuterated methane (CD4) at low Q values for both coals. Pores smaller than 40 nm in radius are less accessible for anthracite than sub-bituminous coal. On the contrary, when the pore radius is larger than 40 nm, the pore accessibility of anthracite becomes larger than that of sub-bituminous coal. Only 20% of pores are accessible to CD4 for anthracite and 37% for sub-bituminous coal, where the pore radius is 16 nm. For these two coals, pore accessibility and pore radius follows a power-law relationship.

Original languageEnglish
Pages (from-to)323-332
Number of pages10
JournalFuel
Volume161
DOIs
StatePublished - Dec 1 2015

Funding

This work is a partial result of support by NSF CBET – Fluid Dynamic Program ( CBET – 1438398 ) and by an Open Research Project through the State Key Laboratory of Coal Resources and Safe Mining from China University of Mining and Technology in Beijing ( SKLCRSM13KFA01 ). The research at the Oak Ridge National Laboratory High Flux Isotope Reactor was sponsored by the Laboratory Directed Research and Development Program and the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy . This research was supported in part by the ORNL Postdoctoral Research Associates Program , administered jointly by the ORNL and the Oak Ridge Institute for Science and Education .

Keywords

  • Accessibility modeling
  • Coal pore characterization
  • Pore accessibility
  • SANS

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