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Characterisation of Through‐Flowing Pores in Activated Carbon Pellets by the Method of Time‐Lag
Author(s) -
Rutherford S. W.,
Nguyen C.,
Do D.D.
Publication year - 1995
Publication title -
developments in chemical engineering and mineral processing
Language(s) - English
Resource type - Journals
eISSN - 1932-2143
pISSN - 0969-1855
DOI - 10.1002/apj.5500030302
Subject(s) - pellets , knudsen diffusion , diffusion , pellet , mass transfer , helium , materials science , volume (thermodynamics) , particle (ecology) , knudsen number , chemical engineering , porosity , surface diffusion , activated carbon , thermodynamics , chemistry , composite material , chromatography , physics , oceanography , organic chemistry , adsorption , engineering , geology
Pellets of finely sized activated carbon particles prepared in our laboratory and tailored to have differing BET surface areas were constructed. The time‐lag technique was employed to investigate the mass transfer of non‐sorbing and weakly sorbing gases in these pellets. This involved subjecting the pellet to known upstream pressure, and the pressure rise in the downstream volume (which was initially outgassed) was monitored. The diffusion coefficient representing the mass transfer into the particle network was found to be a complex Junction of the system parameters for all gases including helium, indicating the possibility of surface diffusion with Helium or that pellet heterogeneity affects the diffusion process. However, the molecular weight dependence of the observed flux is close to that predicted by the Knudsen diffusion equation, allowing the pores to be sized.