Fractionating columns diameter

F Factor. The use of the F factor for fractionating column diameter quick estimation is shown in Reference 3. The developed equation for the F factor is ... 

Table 6.23 Summary of Equations for Sizing Absorbers, Strippers, or Fractionators - Column Diameter...

Any fractionating column of moderate efficiency is satisfactory, e.g., a Dufton column (20 cm. long containing a spiral 10 cm. in length, 2 cm. in diameter with 8 turns of the helix) or a Vigreux column (20-25 cm. long). 

The peripheral stiffening zone (tray ring) is generally 25 to 50 mm (1 to 2 in) wide and occupies 2 to 5 percent of the cross section, the fraction decreasing with increase in plate diameter. Peripheiy waste (Fig. 14-28) occurs primarily with bubble-cap trays and results from the inabihty to fit the cap layout to the circular form of the plate. Valves and perforations can be located close to the wall and little dead area results. Typical values of the fraction of the total cross-sectional area available for vapor dispersion and contact with the liquid for cross-flow plates with a chord weir equal to 75 percent of the column diameter are given in Table 14-6. 

Testing of plates and other devices is carried out by Fractionation Research, Inc. for industrial sponsors. Some of the test data for sieve plates have been published for the cyclohexane//i-heptane and isobu-tane//i-butane systems. Representative data are shown in Fig. 14-43. These are taken from Sakata and Yanagi Jn.stn. Chem. Engis. Symp. See. No. 56, 3.2/21 (1979)] and Yanagi and Sakata [Jnd. Eng. Chem. Proc. Des. Devel, 21, 712 (1982)]. The column diameter was 1.2 m, tray spacing was 600 mm, and weir height was 50 mm. 

FIG. 14-74 HETP values for Max-Pak structured packing,. 35 kPa (5 psia), two column diameters. Cyclohexane/n-heptane system, total reflux. For 0.4.3 m (1.4 ft) column perforated pipe distributor, 400 streams/m2, 3.05 m (10 ft) bed height. For 1.2 m (4.0 ft) column tubed drip pan distributor, 100 streams/m ,. 3.7 m (12 ft) bed height. Smaller column data. University of Texas/Austin Larger column data. Fractionation Research, Inc. To convert (ft/s)(lb/ft ) to (m/s)(kg/m ) , multiply by 1.2199. (Couiiesy Jaeger Troducts, Inc., Housion, Texas.)... 

Methods for quick sizing trayed fractionation and absorption column diameter have been reduced here to equations to facilitate programming for calculators or computers. Three methods are discussed and it is not a bad idea to compare results with all three. 

Other methods for estimating the cost of vessels and fractionators can be used, but weight is usually the best. The cost of fractionators can be correlated as a function of the volume of the vessel times the shell thickness, with an addition for the cost of trays based on their diameter (Reference 13). Fractionator costs can also be correlated based on the volume of the vessel with the operating pressure as a parameter. This requires a great deal of data and does not give as good a correlation as weight. Hall et al. (Reference 14) present curves of column diameter vs. cost. 

There are several approaches to column diameter design [65, 74] as well as the proprietary techniques of major industrial and engineering designers. Some of these use the proprietary Fractionation Research Institute methods which are only available on a membership basis and do not appear in the technical literature. 

To obtain the column diameter, an allowance must be made for downcomer area (say 10%), and the vapor velocity should be some fraction (say 80%) of the flooding velocity. 

It is desired to concentrate a mixture of ethyl alcohol and water from 40 mole per cent to 70 mole per cent alcohol. A continuous fractionating column, 1.2 m in diameter with 10 plates is available. It is known that the optimum superficial vapour velocity in the column at atmosphere pressure is 1 m/s, giving an overall plate efficiency of 50 per cent. 

The linear superficial flow velocity in the packing voids v is calculated from volumetric flow rate Lin, voidage fraction of the adsorbant bed e and column diameter d as... 

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