Billen J, Gzil P, Vervoort N, Baron G V, Desmet G
Department of Chemical Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium.
J Chromatogr A. 2005 May 6;1073(1-2):53-61. doi: 10.1016/j.chroma.2004.10.042.
We report on a series of plate height and flow resistance data obtained via computational fluid dynamics simulations in a simplified two-dimensional (2D) mimic of real packed bed and monolithic columns. By varying the external porosity (0.4 < epsilon < 0.8) and the degree of packing randomness, a good qualitative insight in the relationship between the packing porosity and heterogeneity and the general chromatographic performance parameters is obtained, unbiased by any differences in phase retention factor k', mobile phase diffusivity or viscosity or intra-skeleton porosity. The results provide a quantitative support for the use of domain size reduced plate heights as a means to compare the performance of chromatographic beds with a different porosity, as it was found that packings with a similar degree of packing heterogeneity yield very similar domain size reduced h(min)-values, nearly completely independent of the porosity. The study also clearly shows that the presence of preferential flow paths (inevitably accompanied by the presence of more clustered regions) leads to a decrease of the flow resistance, but also leads to a strong increase of the band broadening if supports with the same porosity epsilon and the same radial width are compared. For the presently considered 2D system, the flow resistance reduction is too small to overcome the corresponding strong increase in band broadening, such that the presence of preferential flow paths always leads to an overall increase of the separation impedance.
我们报告了通过计算流体动力学模拟在真实填充床和整体柱的简化二维（2D）模型中获得的一系列板高和流动阻力数据。通过改变外部孔隙率（0.4 < ε < 0.8）和填充随机性程度，在不受相保留因子k'、流动相扩散率或粘度或骨架内孔隙率差异影响的情况下，对填充孔隙率与非均质性和一般色谱性能参数之间的关系有了很好的定性认识。结果为使用域尺寸减小的板高作为比较不同孔隙率色谱柱性能的一种方法提供了定量支持，因为发现具有相似填充非均质性程度的填料产生非常相似的域尺寸减小的h(min)值，几乎完全与孔隙率无关。该研究还清楚地表明，优先流动路径的存在（不可避免地伴随着更多聚集区域的存在）会导致流动阻力降低，但如果比较具有相同孔隙率ε和相同径向宽度的载体，也会导致谱带展宽大幅增加。对于目前考虑的二维系统，流动阻力的降低太小，无法克服相应的谱带展宽的强烈增加，因此优先流动路径的存在总是导致分离阻抗的整体增加。
