Oldershaw

Perfluorobutyric acid [375-22-4] M 214.0, m -17.5", b 120"/735mm, d 1.651, n 1.295, -0.17. Fractionally distd twice in an Oldershaw column with an automatic vapour-dividing head, the first distn in the presence of cone H2SO4 as a drying agent. 

Figure 9-87. X-Y diagram for adicibatic absorption of HCl at 1 atmosphere. Reproduced by permission of the American Institute of Chemical Engineers, Oldershaw, C. F., Simenson, L, Brown, T. and Rad-cliffe, F. Trans. Sect. Chemical Engineering Progress, V. 43, No. 7 (1947) p. 371 all rights reserved.

Oldershaw, C. F. (1941) Ind. Eng. Chem. (Anal, ed.) 13, 265. Perforated plate columns for analytical batch distillations. 

In addition, Basco and Yee observed electronically excited phosphorus atoms and Pj molecules in excited vibration states in the absorption spectra The latter were also found by Norrish and Oldershaw h. 

Oldershaw column. An all-glass perforated-plate column. The plates are sealed into a tube, each plate being equipped with a baffle to direct the flow of reflux liquid, and a raised outlet which maintains a definite liquid level on the plate and also serves as a drain on to the next lower plate [see Oldershaw Ind Eng Chem (Anal Ed) 11 265 1941]. 

Fractionally distd twice in an Oldershaw column with an automatic vapour-dividing head, the first distn in the presence of cone H2SO4 as a drying agent. 

As might be expected, the vapour phase may offer the controlling resistance to mass transfer in high pressure distillations. Values for tray efficiencies at elevated pressure are scarce [23, 24]. The prediction of tray efficiency may be approached in several ways. One way is to utilize field performance data taken for the same system in very similar equipment. Unfortunately such data are seldom available. When they are available, and can be judged as accurate and representative, they should be used as a basis for efficiency specification [25], Another way is to utilize laboratory-or pilot-plant efficiency data. For example a small laboratory-Oldershaw tray-column can be used with the same system. Of course, the results must be corrected for vapour-and liquid mixing effects to obtain overall tray efficiencies for large-scale design [26], Another approach is the use of empirical or fundamental mass-transfer models [27-30],... 

J.R. Fair, H.R. Null and W.L. Bolles, Scale-up of plate efficiency from laboratory Oldershaw data, Lnd. Engng. Chem. Process Des. Dev., 22 (1983) 53-58. 

The photolysis of S03 in the near ultraviolet has been studied by Norrish and Oldershaw (746). They proposed that the primary process is either... 

Gould, P.L., Howard, J.R., and Oldershaw, G.A. The effect of hydrate formation on the solubility of theophylline in binary aqueous cosolvent systelimfej. Pharm., 51, 195-202, 1989. 

Scale-up from a Pilot- or Bench-Scale Column This is a very common scale-up. No reduction in efficiency on scale-up is expected as long as several precautions are observed. These precautions, generally relevant to pilot- or bench-scale columns, are spelled out with specific reference to the Oldershaw column. 

Scale-up from Oldershaw Columns One laboratory-scale device that found wide application in efficiency investigations is the Oldershaw column [Fig. 14-44, Oldershaw, Ind. Eng. Chem. Anal. Ed. 13, 265 (1941)]. This column is available from a number of laboratory supply houses and can be constructed from glass for atmospheric operation or from metal for higher pressures. Typical column diameters are 25 to 100 mm (1 to 4 in), with tray spacing the same as the column diameter. 

Fair, Null, and Bolles [Ind. Eng. Chem. Process Des. Dev. 22, 53 (1983)] found that efficiency measurements in Oldershaw columns closely approach the point efficiencies [Eq. (14-133)] measured in... 

FIG. 14-44 An Oldershaw column. (From H. Z. Kister, Distillation Design, copyright 1992 by McGraw-Hill reprinted by permission.)... 

A mixing model can be used to convert the Oldershaw point efficiencies to overall column efficiencies. This enhances the commercial column efficiency estimates. A conservative approach suggested by Fair et al. is to apply the Oldershaw column efficiency as the estimate for the overall column efficiency of the commercial column, taking no credit for the greater plug-flow character upon scale-up. The author prefers this conservative approach, considering the poor reliability of mixing models. 

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