Packed columns correlation

Determination of pressure drop through the column (for packed columns, correlations dependent of packing type, column-operating data, and physical properties of the constituents involved are available to estimate the pressure drop through the packing for plate columns, the pressure drop per plate is obtained and multiplied by the number of plates)... 

TABLE 7.1. Stmunary of Experimental Axial Dispmion Data for Gases in Packed Columns Correlated According to Eq. (7.9)... 

To use all of these equations, the heights of the transfer units or the mass transfer coefficients and must be known. Transfer data for packed columns are often measured and reported direcdy in terms of and and correlated in this form against and... 

Other correlations based partially on theoretical considerations but made to fit existing data also exist (71—75). A number of researchers have also attempted to separate from a by measuring the latter, sometimes in terms of the wetted area (76—78). Finally, a number of correlations for the mass transfer coefficient itself exist. These ate based on a mote fundamental theory of mass transfer in packed columns (79—82). Although certain predictions were verified by experimental evidence, these models often cannot serve as design basis because the equations contain the interfacial area as an independent variable. 

This type of equation has been found useful in correlating drop diameters in packed columns where the packing si2e exceeds the drop diameter (65). 

Flooding and Loading Since flooding or phase inversion normally represents the maximum capacity condition for a packed column, it is desirable to predict its value for new designs. The first generalized correlation of packed-column flood points was developed by Sherwood, Shipley, and Holloway [Ind. Eng. Chem., 30, 768 (1938)] on the basis of laboratory measurements primarily on the air-water system. 

A new generalised correlation for pressure drop in packed columns, similar to Figure 11.44, has been published by Leva (1992), (1995). The new correlations gives a better prediction for systems where the density of the irrigating fluid is appreciably greater than that of water. It can also be used to predict the pressure drop over dry packing. 

Correlation was found between domain size and attainable column efficiency. Column efficiency increases with the decrease in domain size, just like the efficiency of a particle-packed column is determined by particle size. Chromolith columns having ca. 2 pm through-pores and ca. 1pm skeletons show H= 10 (N= 10,000 for 10 cm column) at around optimum linear velocity of 1 mm/s, whereas a 15-cm column packed with 5 pm particles commonly shows 10,GOO-15,000 theoretical plates (7 = 10—15) (Ikegami et al., 2004). The pressure drop of a Chromolith column is typically half of the column packed with 5 pm particles. The performance of a Chromolith column was described to be similar to 7-15 pm particles in terms of pressure drop and to 3.5 1 pm particles in terms of column efficiency (Leinweber and Tallarek, 2003 Miyabe et al., 2003). Figure 7.4 shows the pressure drop and column efficiency of monolithic silica columns. A short column produces 500 (1cm column) to 2500 plates (5 cm) at high linear velocity of 10 mm/s. Small columns, especially capillary type, are sensitive to extra-column band... 

The pressure drop through packed columns, and the flooding conditions, can be estimated from the generalized correlation of Leva (1992), shown in Fig. 13-5. The pressure gradient in millimeters of water per meter of packed height is the parameter on the curves, and interpolation is usually necessary to determine the pressure drop (note that the pressure... 

For flow through ring packings which as described later are often used in industrial packed columns, Ergun(10) obtained a good semi-empirical correlation for pressure drop as follows ... 

Data on small packed columns were correlated by Fair (1972) in the form... 

In this work correlations between mobile phase solvent strength and chromatographic retention of a number of different solute families will be presented. The first solvent strength measurements on ternary mobile phases will also be presented. Finally, a retention mechanism for packed column SFC is proposed. 

A variety of physical parameters have been shown to correlate with chromatographic retention. Several physical properties, measured SFC capacity factors, as well as GLC derived retention indices for the PAHs studied are listed in Table II. The capacity factors, k, were calculated from an isoconfertic-isothermal SFC separation of a mixture of the PAHs on an octadecyl bonded packed column using CC>2 as the mobile phase (4500 psi, 100°C). 

Success of rate-based multistage separation modeling is ultimately tied to underlying equipment hydrodynamics performance correlations for tray or packed columns. For example, the thickness of the film... 

T.A. Berge and J. F. Deye, Correlation between column surface area and retention of polar solutes in packed-column supercritical fluid chromatography, J. Chromatogr., 594 291 (1992). 

Biermanns et al. reported the chiral resolution of /3-blockers, including propranolol, metoprolol, and atenolol using packed-column supercritical fluid chromatography [38]. A Chiracel OD column with a mobile phase of 30% methanol with 0.5% isopropylamine in carbon dioxide was used for the separation. A baseline separation of isomers was obtained in less than 5 min at a mobile-phase flow rate of 2 ml/min. While keeping the column outlet pressure constant, the flow rate was increased to 4 ml/min and it was noted that, although the retention was reduced, the resolution remained the same. Both R- and S-propranolol gave linear responses from 0.25-2500 ppm with a correlation coefficient of >0.9999. The detection limit was approximately 250 ppb for a S/N ratio of 3. The reproducibility for both R- and S-propranolol was less than 1.5%. It was also noted that 0.09% R-propranolol can be quantitated in the presence of 2500 ppm of S-Propranolol. 

For structured packings the correlation of Rocha et al. (1996) has been well validated for a number of packings tested in larger equipment. Even if experimental data are available, one must be cautious in applying data taken in small laboratory columns to designs of large commercial contactors. 

---