Bolles-Fair correlation

Figure 13.43. Liquid phase parameters for the Bolles/Fair correlation for random packing efficiency.

The smallest size packings in the Bolles-Fair correlation are nominally 13 mm. If the usually required minimum ratio of column diameter to packing diameter of 8 is to be retained (to avoid bypassing at the wall), scaleup studies require a minimum column diameter of about 100 mm. Research in progress may lead to the use of a special, small laboratory packing (e.g., Pro-Pak , from Scientific Development Co.) for columns as small as 25 mm. HETP values of two sizes of Pro-Pak, for cyclohexane/n-heptane at 1.0 atm, are shown in Figure 12.66, from reference 84. 

It should be noted that the smallest size packings in the Bolles-Fair correlation are nonanally 12 min (0,5 in.) in diameter. If the general rale of 8 1 column packing diameter is to be maintained, (hen a minimum column size of 100 mm (4 in.) is indicated. This is a crucial point in tha design of pilot facilities and the development of scaleup parameters. It is not yet possible to go to the tiny packings for laboratory tests (using, say, column diameters of 25-50 mm) and still obtain reliable scaleup data. 

Another point regarding the Bolles-Fair correlation the height correction term to be used is (hat for a single bed having its own liquid distribution (or redistribution). 

We will use the correlation of Bolles and Fair (1982), for which HTUs are defined in the same way as here. The Bolles-Fair correlation is based on the previous correlation of Cornell et al., (1960a, b) and a data bank of 545 observations and includes distillation, absorption, and stripping. This model and variations on it remain in common use fWang et al.. 2Q05V... 

Bolles (71) extended Fair s sieve tray weep point correlation (31 Fig. 6.18) to investigate weeping in valve trays. Some results are depicted in Fig. 6.19. The axes of Fig. 6.19 are identical to those of Fig. 6.16. Each dashed line is the locus of weep points predicted from Bolles extended Fair correlation. The heavy lines are the "operating lines, i.e.. 

Bravo and Fair (122) statistically analyzed the reliability of their model. They concluded that multiplying an HETP calculated from their model by a safety factor of 1.6 will give 95 percent confidence that the column is not too short This factor is slightly lower than the Bolles and Fair (55,96) and the Onds et al. (123) correlations. MacDougall (58) repeated the statistical analysis after he rearranged the data bank, and showed that a safety factor of 1.3 is more appropriate, making the Bravo and Fair correlation much better than the others. 

E] Use Bolles Fair (Ref. 43) database to determine new effective area ae to use with Onda et al. (Ref. 109) correlation. Same definitions as 5-24-C. P = total pressure, atm MG = gas, molecular weight m = local slope of equilibrium curve Em/Gm = slope operating line Z = height of packing in feet. 

G. Absorption, stripping, distillation, counter-current, Hi, and Hq, random packings, Cornell et al. correlation, and Bolles and Fair correlation... 

NMR Coupling Constant of MOiSnCI. The y(" Sn—CH3) coupling constant of (CH3)3SnCl, reported by Bolles and Drago (177), represents such a property. Coupling constants in 10 solvents including pyridine (6,7,8,13,18,23,24,26,29,50) show a fair correlation with j8 ... 

FIG. 5-29 Hi correlation for various packings (Table 5-28-G). To convert meters to feet, multiply by 3.281 to convert pounds per hour-square foot to kilograms per second-square meter, multiply by 0.001.356 and to convert millimeters to inches, multiply by 0.0.394. [Bolles and Fair, Inst. Chem. Eng. Symp. Ser., no.. 56, 3,3/35 (1.96.9).]... 

Bolles and Fair (1982) have extended the correlations given in the earlier paper to include metal Pall rings. 

HTU data have been correlated by Cornell et aL (1960) and updated by Bolles and Fair [Inst. Chem. Eng. Symp. Ser. 56(2), 3.3/35 (1979)]. Pall rings, Raschig rings, and saddles are covered in the original article, but only the pall ring results are quoted here. Separate relations for the liquid and vapor phases are represented by Eqs. (13.239) and (13.240) and Figure 13.44. 

In the absence of experimental data, mass transfer coefficients (and hence heights of transfer units) can be estimated by generalized models. A popular and easy to use correlation for random packings is that of Bolles and Fair (1982). The earlier correlations of Onda et al. (1968) and Bolles and Fair are also useful for random packings. 

Weep prediction, The weep point of valve trays can be calculated from the Bolles extension (71) of Fair s weep point correlation (31). The same correlation (Fig. 6.18) is used, except that the sieve fractional hole area is substituted by the ratio of valve slot area to tray active area. An alternative weep point correlation for valve trays was presented by Klein (73). Hsieh and McNulty (63) extended their sieve tray weep rate correlation (Sec. 6.2.12) to valve trays. The extension is complex, and discussed elsewhere (63). 

Belles and Fair (55) compared flood-point predictions from the Eckert correlation to published experimental data for random packings. Their massive data bank consisted mainly of data for first-generation packings, but also included some data for second-generation packings. For the data compared, Bolles and Fair showed that Eckert s correlation gave reasonable flood-point prediction. Statistically, they showed that if a safety factor of 1.3 was applied to the correlation flood-point predictions, the designer will have 95 percent confidence that the column will not flood. 

MacDougall (58) compared flood-point data to predictions from the Eckert correlation for first- and second-generation packings. His study came up with an identical conclusion and an identical safety factor to those derived by Bolles and Fair. 

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