SCCS Fall Seminar - Mahnaz Firouzi
"Gas permeability and Klinkenberg effects in carbon micro and mesopores"
Abstract: Molecular dynamics simulations were carried out to study gas permeability and the Klinkenberg effects of helium, methane, and carbon dioxide, in addition to their mixtures confined in carbon micro and mesopores. The structure was modeled using a slit pore as well as a three-dimensional pore network, generated atomistically using the Voronoi tessellation method, to represent the carbon-based porous structure of natural systems. Non-equilibrium molecular dynamics (NEMD) simulations were used with an external driving force imposed on the system. The results indicate that the velocity profile is uniform for pore sizes less than 2 nm (micropores). As pore sizes increase to 10 nm parabolic velocity profiles are observed due to reduced interaction of gas molecules with carbon atoms of the pore walls. Also, in micro- and mesopores unlike in macropores (where continuum flow occurs), the gas velocity at the walls is non-zero. The shape of the velocity profile is found to be independent of the applied pressure gradient in micropores. Simulation results are compared with experiments to understand both the merit and limitations of the simulation approach. These fundamental studies have potentially important implications on gas transport in carbon-based porous materials and geologic formations which lead to an understanding of the mechanism associated with gas transport in the confined spaces for carbon capture and sequestration applications.