In many engineering fields, modeling, calculations, simulations, and computer-assisted optimization are important tools to accelerate equipment design and process development. In process chromatography, calculations are also used to support the set up of separation systems. Many contributions dealing with the calculation of the effects of the thermodynamics and mass transfer kinetics involved in the chromatographic process can be found in the literature [1]. For such considerations, the use of one single space dimension is sufficient when modeling the process.Unfortunately, the production capacity in preparative chromatography can only be increased by increasing the column diameter. Accordingly, large D/L-ratios (diameter divided by length) must be used in preparative applications, raising important column design considerations.Even though the study is carried out for preparative applications, the experiments were performed with a rather narrow column. However, this column has a large D/L-ratio, around one, and its performance exhibits a high sensitivity to the distributor and collector design. Therefore, it is suitable for the investigations carried out in this paper, despite its small capacity.The influence of design considerations, like these, cannot be studied by computer simulation using a one-dimensional model [2]. The design of a chromatographic column determines the flow field of the mobile phase, which must be calculated using hydrodynamic equations. This flow field carries the sample though the column. In order to set up such a model, the commercial CFD code FLUENT is used.This article presents a way of predicting and investigating design issues in chromatography using simulation. For this purpose, a visualization technique is applied to obtain the sample distribution within a column. The comparison of band profiles from the simulation with experimental data is a novelty in the chromatography literature.
Experimental
ColumnExperimental data are needed to validate the model. Experiments were made with a 17 mm I.D. borosilicate glass column from Omnifit (High Performance range, max. pressure 500 psi). This 50 mm long column has a bed length of 16±18 mm, depending to the amount of packing material used. Two different distributor and collector systems were compared. All columns were packed with a C18 Silica-Gel (YMC, Japan) with a particle size distribution of 15±30 lm. Methanol (HPLC grade from Fisher) was used to pack the column. The end pieces (distributor and collector) were supplied with the column. Fig. 1 shows a photo and a schematic drawing of the construction of the glass column.A small lip forms part of the frit holder, so the diameter at point A in Fig. 1 is about 1 mm smaller than at point B. Therefore only flexible frits can be inserted into the frit holder. The manufacturer supplies Teflon frits for the column, 10 and 25 lm grade frits were used. The 5 lm frit is unsuitable because it is bypassed by the mobile phase. Since a 25 lm frit was used with particles having a 15±30 lm size distributio...
