Reciprocating-Plate Columns

In this equation, represents the rate of energy dissipation per unit mass of fluid. In pulsed and reciprocating plate columns the dimensionless proportionahty constant K in equation 38 is on the order of 0.3. In stirred tanks, the proportionaUty constant has been reported as 0.024(1 + 2.5 h) in the holdup range 0 to 0.35 (67). The increase of drop si2e with holdup is attributed to the increasing tendency for coalescence between drops as the concentration of drops increases. A detailed survey of drop si2e correlations is given by the Hterature (65). 

The nonuniformity of drop dispersions can often be important in extraction. This nonuniformity can lead to axial variation of holdup in a column even though the flow rates and other conditions are held constant. For example, there is a tendency for the smallest drops to remain in a column longer than the larger ones, and thereby to accumulate and lead to a locali2ed increase in holdup. This phenomenon has been studied in reciprocating-plate columns (74). In the process of drop breakup, extremely small secondary drops are often formed (64). These drops, which may be only a few micrometers in diameter, can become entrained in the continuous phase when leaving the contactor. Entrainment can occur weU below the flooding point. 

Fig. 15. Mechanically agitated columns (a) Scheibel column (b) rotating-disk contactor (RDC) (c) asymmetric rotating-disk (ARD) contactor (d) Oldshue-Rushton multiple-mixer column (e) Kuhni column and (f) reciprocating-plate column.

Fractional extraction has been used in many processes for the purification and isolation of antibiotics from antibiotic complexes or isomers. A 2-propanol—chloroform mixture and an aqueous disodium phosphate buffet solution are the solvents (243). A reciprocating-plate column is employed for the extraction process (154). 

FIG. 15-49 Schematic arrangement of the 900-mm (36-in) reciprocating-plate column, (Coutiesy of Glitsch Process Systems Inc.)... 

TABLE 15-10 Summary of Minimum HETS Values and Volumetric Efficiencies for a Reciprocating-Plate Column ... 

Krieger-Dougherty equation, 21 717 KRIMZ reciprocating-plate column, 10 780 Krinovite, 6 4 7 It Kritchevsky amides, 2 453, 454 Kroll, Wilhelm J., 24 838 Kroll-Betterton debismuthizing process,... 

Plate design, in a reciprocating-plate column, 70 779 Plate diffusers, 26 163 Plate-fin heat exchangers, 73 263 Plate-frame heat exchangers, 73 263 Plate glass, elastic properties, 5 614t Plate heat exchangers, 70 157 73 263-265, 267... 

Reciprocating piston meters, 77 655 Reciprocating-plate columns (RPCs), 70 779-780... 

Reciprocating- plate columns High throughput Low HETS Great versatility and flexibility Simplicity in construction Handles liquids containing suspended solids Handles mixtures with emulsifying tendencies Pharmaceutical Petrochemical Metallurgical Chemical... 

Reciprocating-plate columns High throughput, low HETS, great versatility and flexibility, simplicity in construction, handles liquids containing suspended solids, handles mixtures with emulsifying tendencies Pharmaceutical, petrochemical, metallurgical, chemical... 

In 1935, Van Dijck proposed that the extraction efficiency of a perforated-plate column could be improved by either pulsing the liquid contents of the column or by reciprocating the plates. The latter idea was relatively little exploited until the late 1950s, when Karr reported data on a 3-in.-diameter, open-type, perforated reciprocating-plate column. The column was further developed by Karr and Lo by employing baffles. 

The open-type perforated reciprocating-plate column (Fig. 13f) developed by Karr and Lo consists of a stack of perforated plates and baffle plates which have a free area of about 58%. The central shaft which supports the plates is reciprocated by means of a reciprocating drive mechanism located at the top of the column. These columns have gained increasing industrial application in the pharmaceutical, petrochemical, and wastewater-treatment industries, and columns up to 60 in. in diameter are in service. 

FIGURE 10 Some types of reciprocating plate columns. (From Baird et a/.53 Reproduced by permission of John Wiley Sons Limited.)... 

The Karr reciprocating-plate column (Fig. 15-50) is a popular example. It uses dual-flow plates with 50 to 60 percent open area and has no downcomers [Karr, AlChE J., 5(4), pp. 446-452 (1959) Karr and Lo, Chem. Eng. Prog., 72(11), pp. 68-70 (1976) and Karr, AIChE J., 31(4), pp. 690-692 (1985)]. Because of the high open area, a Karr column may be operated with relatively high throughput compared to other types of agitated columns, up to about 1000 gaF(h ft ) [40 m /(h m )] depending upon the application. The plates are mounted... 

In reciprocating plate columns, the height equivalent to a theoretical stage (HETS) is a strong function of the reciprocating speed, Af, the product of the reciprocation amplitude and frequency. Karr columns actually exhibit optimal values for A/where the (HETS) is clearly minimized. These... 

Estimate the minimum HETS for a 2-in diameter reciprocating plate column. The hquid-liquid interfacial tension is 30 dyne/cm. The solvent phase density and viscosity are 0.82 g/cm and 1.3 cP, respectively. The aqueous phase density and viscosity are 1 g/cm and 1.129 cP, respectively. Water is the continuous phase, and its linear velocity down the column is (/ = 0.40 cm/s. The velocity of the dispersed solvent phase is f/ = 0.12 cm/s. 

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