Time and Length Scales of Eddy Dispersion in Chromatographic Beds
- 27 July 2009
- journal article
- research article
- Published by American Chemical Society (ACS) in Analytical Chemistry
- Vol. 81 (16), 7057-7066
- https://doi.org/10.1021/ac901187d
Abstract
Time and length scales as well as the magnitude of individual contributions to eddy dispersion in chromatographic beds are resolved. We address this issue by a high-resolution numerical analysis of flow and mass transport in computer-generated bulk (unconfined) packings of monosized, nonporous, incompressible, spherical particles and complementary confined cylindrical packings with a cylinder-to-particle diameter ratio of dc/dp = 20. The transient behavior of longitudinal and transverse dispersion is analyzed and correlated with the spatial scales of heterogeneity in the bulk and confined packings. Simulations were carried out until complete transcolumn equilibration in the confined packings was achieved to facilitate a quantitative study of the geometrical wall effect. Longitudinal plate height data calculated over a wide range of reduced velocities (0.1 ≤ ν ≤ 500) were fitted to the comprehensive Giddings equation. The determined transition velocities for individual contributions to eddy dispersion were found to be widely disparate. As a consequence, the total effect of eddy dispersion on the plate height curves can be approximated in the practical range of chromatographic operational velocities (5 ≤ ν ≤ 20) by a composite expression in which only the short-range interchannel contribution retains its coupling characteristics, while transchannel and transcolumn contributions appear as simple mass transfer velocity-proportional terms.Keywords
This publication has 56 references indexed in Scilit:
- Diameter-dependent dispersion in packed cylindersAIChE Journal, 2007
- Analysis of particle porosity distribution in fixed beds using the discrete element methodPowder Technology, 2006
- General HETP Equation for the Study of Mass-Transfer Mechanisms in RPLCAnalytical Chemistry, 2006
- Measurement of the parameters of the mass transfer kinetics in high performance liquid chromatographyJournal of Separation Science, 2003
- Numerical simulation and measurement of liquid hold-up in biporous media containing discrete stagnant zonesPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2002
- Structure of packed beds probed by Magnetic Resonance ImagingPowder Technology, 2001
- Stagnant Mobile Phase Mass Transfer in Chromatographic Media: Intraparticle Diffusion and Exchange KineticsThe Journal of Physical Chemistry B, 1999
- Spatial correlations and dispersion for fluid transport through packed glass beads studied by pulsed field-gradient NMRPhysical Review E, 1998
- Study of Dispersion in Packed Chromatographic Columns by Pulsed Field Gradient Nuclear Magnetic ResonanceJournal of the American Chemical Society, 1998
- Scale-up effects due to near-wall channelling in isothermal adsorption columns: on the limitations in the use of plug flow modelsChemical Engineering and Processing - Process Intensification, 1991