Axial dispersion in single pellet-string columns with non-porous packing

摘要

Using the chromatographic technique (carrier-gas: nitrogen; tracer-gases: H-2, He, Ar, C2H6) the axial dispersion in single pellet-string columns (SPSC) packed with non-porous spherical and cylindrical particles was studied. Dispersion due to extra column effects was eliminated via convolution of column responses for two column lengths. For spherical pellets the pellet/column diameter ratios (d(p)/d(c)) were in the ranee 0.57-0.79; for cylindrical pellets d(p)/d(c) = 0.52-0.69 with pellet height/diameter ratios H/D = 0.78-1.5. With different tracer-gases and the same packing and column sizes analogous dependencies of Bodenstein numbers, Bo (Peclet number, Pe, with pellet size, d(p), as characteristic dimension), versus the product of Reynolds and Schmidt numbers, ReSc, were obtained. For spherical column packing the Bo-ReSc curves depend also on the d(p)/d(c) ratio; for cylindrical pellets the sphericity (which depends on HID ratio) plays an additional role. Empirical interpolation equations for both shapes of pellets were set up.The obtained information on axial dispersion significantly increases the confidence of pore-diffusion characteristic when the chromatographic method with SPSC packed with porous pellets is applied. (C) 2004 Elsevier Ltd. All rights reserved.