Section 4.2 Distillation

Tray columns, 316 s/s column with 316 s/s sieve trays on 0.3 m spacing. FOB units with trays shop-installed complete with some no2zles but no access holes or tooling up fee. FOB cost 234000 at the product of (column height, m) (diameter, m) = 14 with n = 0.78 for the range 5-14 m and n = 0.93 for the range 14-100. L-rM = 1.78. L/M = 0.28-0.38. Factor, tray spacing, 0.3 m, X 1.00 0.6 m, X 1.5. 

Trays stack 316 s/s as above but excluding tooling up fee. Installed cost = 420000 at the product of (stack height, m) ( diameter, m) = 87 with n = 0.76 for the range 2.5-200 

Packed columns, 316 s/s column with 316 s/s Pall rings including support trays, hold-down plates, distributor and redistributor trays including column with some nozzles but no access holes. FOB cost 1 425 000 at the product of (column 

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However, in general, solvent recovery is an important step in the overall solvent extraction process. Solvent recovery from the raffinate (i.e., water phase) may be accomplished by stripping, distillation, or adsorption. The extract, or solute-laden solvent stream, may also be processed to recover solvent via removal of the solute. The solute removal and solvent recovery step may include reverse solvent extraction, distillation, or some other process. For example, an extraction with caustic extracts phenol from light oil, which was used as the solvent in dephenolizing coke plant wastewaters (4). The caustic changes the affinity of the solute (phenol) for the solvent (light oil) in comparison to water as will be explained in the equilibrium conditions section. Distillation is more common if there are no azeotropes. 

We begin the development of graphical design procedures by deriving generalized material balance equations for countercurrent cascades. These are first applied to simple, single-section distillation, extraction, absorption, and... 

Let s examine two constituent parts of section distillation trajectory at the example of sharp preferable split of three-component ideal mixture (Fig. 5.6a) the part located in the boundary element (the side of concentration triangle), and the part located inside concentration simplex (triangle). There is a trajectory tear-off point from the boundary element x between these two parts. 

The distillation column has an enriching or rectifying section, a feed section, and a stripping section. A distillation system, however, also includes a large assortment of equipment and systems that support the process feed section, preheat section, distillation column, overhead section, bottom section, and product storage. The quality system provides the mathematical foundation that standardizes plant operations. A unit checklist is designed to collect a wide variety of operational information. 

The product recovery section distills the reactor products into various fractions. The main fractionator is often designed to recover a heavy gasoline cut, mid-distillate cut(s), and reject fuel... 

If the treatment of distillation in a given section of the book needs certain building blocks, it is most likely that those concepts/methods/buildlng blocks have been introduced in an earlier chapter or section of the book. Furthermore, in whichever section distillation appears, it is studied as part of a specific pattern followed by many other separation processes based on phase equilibrium. Such patterns have been emphasized often throughout particular chapters. 

The field of application for liquid chromatography in the petroleum world is vast separation of diesel fuel by chemical families, separation of distillation residues (see Tables 3.4 and 3.5), separation of polynuclear aromatics, and separation of certain basic nitrogen derivatives. Some examples are given later in this section. 

Experiment 6. Fractional Distillation of a Mixture of Benzene and Toluene. Fractionally distil about 40 ml. of a mixture of equal volumes of benzene and toluene, using the type of fractionating column shown in Fig. ii(b), in which about 18-20 cm. of the column are actually filled with glass sections, but in which the cotton-wool lagging is not used. Distil very slowlyy so that the total distillation occupies about hours. Shield the apparatus very carefully from draughts. Collect the fractions having the b.ps (a) 80-85°, ( ) 85-107°, (c) 107-111°. A sharp separation should be obtained, e.g.y these fractions should have volumes of about 19, 2, and 17 ml. respectively. 

Heating with soda-dime. See Section 3, p. 327, Condense the aniline which distils over in a test-tube, dilute with water and add bleaching powder (or NaClO) solution. Note the iolet coloration. 

Rubber stoppers are frequently employed in the laboratory in vacuum distiUation assemblies (compare Section 11,19) for distillations under atmospheric pressure bark corks are generally used. Many organic liquids and vapours dissolve new rubber stoppers slightly and cause them to swell. In practice, it is found that rubber stoppers which have been previously used on one or two occasions are not appreciably attacked by most organic solvents, owing presumably... 

The theory of the process is discussed in Sections 1,1-1,3. The apparatus of Fig. 11,12,1 may be used when moderate quantities of the substance are available. A is a 50 ml. distilling flask attached by a cork to a Liebig condenser B, upon the end of which an adapter C is fitted D is a receiver for collecting the distillate. The thermometer E is fitted into the neck of the distilling flask by means of a well-bored cork the bulb of the thermometer should be in the centre of the neck of the flask and slightly below (ca. 5 mm.) the level of the side tube. The flask may be heated on a wire gauze with asbestos centre or preferably in an air bath (Fig. 77, 5, 3). 

The liquid should be poured into the distilling flask, preferably through a funnel the stem of which extends below the side arm, and a few fragments of unglazed porous porcelain ( porous pot, see Section 1,2)... 

An account of the elementary theory of fractional distillation is given in Section 1,4. Fractionating columns suitable for both elementary and advanced work will be described in the following pages. 

In order to carry out a distillation, the apparatus is completely assembled, the water pump turned on to its maximum capacity, and the screw clip on the capillary tube in the Claisen flask adjusted so that a gentle stream of air bubbles through the liquid (see Section 11,19 for details of the preparation of the capillary tube). The barometric pressure is read, and if the resulting vacuum deter mined from the reading on the mano meter is satisfactory (as estimated from the temperature of the tap water), the flask may be heated in an air (Fig. II,... 

The so-called hydro-vac pump, shown in Fig. 11, 22, 2 (the upper half of the mercury reservoir and the column above it are insulated by a layer of asbestos), is an inexpensive, all-glass, mercury diffusion pump, which can be used in series either with an oil pmnp or with a water Alter pmnp (compare Fig. 11,21, 1) capable of producing a vacuum of at least 2 mm. It is accordingly of particular value in the organic laboratory for vacuum distillations, fractionations, sublimations and pyrolyses as well as for molecular distillations (see Section 11,26). The hydro-vac... 

An elementary account of the subject has been given in the previous Section. For the fractional distillation under diminished pressure of liquids diflfering only slightly in boiling point, a firactionating column (see Sections 11,15 and 11,17) must be used. Provision must, of course, be made for the insertion of a capillary tube into the fiask containing the mixture. This can be done by any of the following methods —... 

The use of a ternary mixture in the drying of a liquid (ethyl alcohol) has been described in Section 1,5 the following is an example of its application to the drying of a solid. Laevulose (fructose) is dissolved in warm absolute ethyl alcohol, benzene is added, and the mixture is fractionated. A ternary mixture, alcohol-benzene-water, b.p. 64°, distils first, and then the binary mixture, benzene-alcohol, b.p. 68-3°. The residual, dry alcoholic solution is partially distilled and the concentrated solution is allowed to crystallise the anhydrous sugar separates. 

The student should be familiar with the theory of steam distillation, given in Section 1,6, before carrying out the operation in the laboratory. 

Sometimes an air bubble enters the tube E and prevents the regular flow of liquid from B the air bubble is easily removed by shaking the rubber tube. The flask A is heated (e.g., by a ring burner) so that distillation proceeds at a rapid rate the process is a continuous one. If the liquid to be steam distilled is lighter than water, the receiver must be modified so that the aqueous liquors are drawn off from the bottom (see Continvmia Extraction of Liquids, Section H, 44). 

The theory of, and the apparatus for, distillation with superheated steam are described in Section 1,7. 

Attention is directed to the fact that ether is highly inflammable and also extremely volatile (b.p. 35°), and great care should be taken that there is no naked flame in the vicinity of the liquid (see Section 11,14). Under no circumstances should ether be distilled over a bare flame, but always from a steam bath or an electrically-heated water bath (Fig.//, 5,1), and with a highly efficient double surface condenser. In the author s laboratory a special lead-covered bench is set aside for distillations with ether and other inflammable solvents. The author s ether still consists of an electrically-heated water bath (Fig. 11, 5, 1), fitted with the usual concentric copper rings two 10-inch double surface condensers (Davies type) are suitably supported on stands with heavy iron bases, and a bent adaptor is fitted to the second condenser furthermost from the water bath. The flask containing the ethereal solution is supported on the water bath, a short fractionating column or a simple bent still head is fitted into the neck of the flask, and the stUl head is connected to the condensers by a cork the recovered ether is collected in a vessel of appropriate size. 

Most solvents, which are immiscible with water, may be dried by simple distillation until the distillate is clear (compare Section 11,39) the residue is anhydrous. It is usually necessary to remove about 10 per cent, by dis tillation before the residue is completely anhydrous. 

The student should first study the elementary theory of fractional distillation given in Sections 1,4-1,5. The experimental technique for simple fractional distillation is described in Section 11,15. 

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