Column profile membrane systems

In seeking the most efficient process possible, a designer will wish to explore a wide range of feasible designs. To make this possible, an efficient method for the synthesis and assessment of any hybrid separation process has been developed. Since both processes have been analyzed using similar mathematical backgrounds, it is possible to use residue curve maps and column profile maps for both distillation and membranes to design hybrid systems of the two. 

B.3.2 Generating Profiles for Hybrid Column For demonstration purposes, it will initially be assumed that operation will occur at 4 = 0.8. In order to display the profiles obtainable for this design, and npvalues were arbitrarily chosen. Furthermore, for the design to be feasible, it is required that the profiles of each section, including the membrane, intersect in the same order and direction as that of liquid flow in the system. Figure 9.14 shows the column and membrane profiles for operation at tai =40 with ni =5. 

The curves shown in Figures 3 and 4 are simulated composition profiles based on experimental data. The calculated trends fit the experimental compositions quite well, and in each case the experimental methane peak is well described. This demonstrates that the basic model for the membrane column can be applied to multicomponent systems as well as to binary mixtures. 

Two situations involviag tmasport of a species lo a liquid in laminar flow can he mudeled by the system in Fig, 2.3-16. One might represent absorption (tom a gas stream into liquid Rowing over pieces of packing in a column, The other geometry could represent dissolution of a solid into a flowing liquid film or the transport from a membrane surface into a solution in laminar flow over the membrane. Both these simple systems illustrate die efleet of velocity profiles or shear rales on mass transfer to a fluid. 

Both methods use a low-capacity cation exchanger as a stationary phase and a dilute mineral acid such as hydrochloric or nitric acid as a mobile phase. Although stationary phases and eluents have changed over the years, the principal difference between the methods is the same up to the present day. For his hypothetical experiments. Small kept constant the volume of the stationary phase, the ion-exchange capacity of the separator colunm, the selectivity coefficients for sodium and potassium relative to the hydronium ion, and the injection volume. With these values and the known acid concentration in the mobile phase, it is possible to calculate the elution volumes of sodium and potassium. To further simplify the calculation of the elution profiles, the chromatographic peaks are assumed to be symmetrical, so that they can be described by a Gaussian curve. One can further assume that the membrane-based suppressor system exhibits a very small dead volume and, therefore, subtracts negligibly from the efficiency of the separator column, which is estimated to be 3000 theoretical plates. 

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