Columns perforated plate towers

Countercurrent columns with additional kinetic energy input have found a broad range of industrial applications [42-48]. Examples of extraction towers with energy input are pulsed towers, pulsed packed columns and pulsed perforated-plate towers. A number of units with some form of mechanical agitation are also used (Karr column, Scheibel column, Oldshue-Rushton column, Ktihni column, RZE extractor, RDC and ARD extractor, Graesser contactor). 

Perforated-plate Towers. In the perforated-plate, or sieve-plate, column, the dispersed phase is repeatedly coalesced and redispersed by causing it to flow through a series of trays in which a large number of small holes have been punched or drilled. In the simplest type, the plates are similar to the side-to-side baffles described above, except that they are perforate. Hunter and Nash (42) describe a successful installation of this type for dephenolating gas liquor consisting of a 46-ft,-high shell, 5 ft. in diameter, in which the baffles each contain two hundred holes. 

A tower separates a weak ammonia solution. Design trays using perforated plates without downcomers for the following conditions as determined from the column performance calculations. 

This led to the development of reciprocating plate towers which consist of a stack of perforated plates and baffle plates. The column developed by Karr (Fig. 2.18) reaches high maximum loads and is suitable for systems with low interfacial tension [44]. Here the perforated plates move up and down driven by an outside motor. The... 

Plate Columns. The much preferred plate is the sieve tray. Columns have been built successfully in diameters larger than 4.5 m. Holes from 0.64 to 0.32 cm in diameter and 1.25 to 1.91 cm apart are commonly used. Tray spacings are much closer than in distillation—10 to 15 cm in most applications involving low-interfacial-tension liquids. Plates are usually built without outlet weirs on the downspouts. A variation of the simple sieve column is the Koch Kascade Tower , where perforated plates are set in vertical arrays of moderately complex designs. 

A continuous version of-this process is used in Germany (Rg. 15-27). Molten caprolactam, catalyst, and stabilizer are metered into the top of a tower heated to 25Q-260°C by a heat-exchange liquid and maintained at atmospheric pressure. The product slowly passes down through perforated plates in the column as polymerization occurs and is continubusly drawn off at the bottom and metered to spinning machines. This product contains 10 per cent monomer, and the final fiber must be extracted to remove the monomer. 

Brown (Ref. 3) reports eflSiciencies as high as 120 per cent for a commercial beer column using perforated plates. The same efficiency was reported for the rectification of an ethanol-water mixture in a special laboratory column. The same investigator reports efficiencies of about 20 per cent for naphtha-absorption towers. 

Figure 1335. Packed column and internals, (a) Example packed column with a variety of internals [Chen, Chem. Eng. 40, (5 Mar. 1984)]. (b) Packing support and redistributor assembly, (c) Trough-type liquid distributor, (d) Perforated pipe distributor, (e) Rosette redistributor for small towers. (0 Hold-down plate, particularly for low density packing.

Packed tower studies were made with a borosilicate glass column 4 inches in inside diameter packed with /4-inch ceramic Intalox saddles. The feed was metered through a rotameter from a constant-head tank, and distributed through the tower with a perforated aluminum plate. Aluminum tubing and polyethylene pipe were used to connect the ozone generator to the tower. A continuous sample was withdrawn from the tower bottom for analysis, and exit gas from the top of the tower was conducted to a wet-test meter for volume measurements. Ozone was absorbed in 5% potassium iodide solutions and titrated with thiosulfate to a starch end point. 

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