Pulsed plate columns

The pulsed-plate column is typically fitted with hori2ontal perforated plates or sieve plates which occupy the entire cross section of the column. The total free area of the plate is about 20—25%. The columns ate generally operated at frequencies of 1.5 to 4 H2 with ampHtudes 0.63 to 2.5 cm. The energy dissipated by the pulsations increases both the turbulence and the interfacial areas and greatly improves the mass-transfer efficiency compared to that of an unpulsed column. Pulsed-plate columns in diameters of up to 1.0 m or mote ate widely used in the nuclear industry (139,140). 

Equipment type Pulsed plate column Pulsed plate column... 

Gravity Pulsation Group C Pulsed packed column Pulsating plate column Group D Pulsed sieve plate column Controlled cycling column... 

Logsdail, D. H. and Thornton, J. D. Trans. Inst. Chem. Eng. 35 (1957) 331. Liquid-liquid extraction. Part XIV. The effect of column diameter upon the performance and throughput of pulsed plate columns. 

Fig. 14.11 Acid recovery by pulsed plate column operation at Sdderfors Steel Works, Sweden. 

Pulse-packed columns Pulse sieve-plate columns... 

For some applications, instead of pulsed sieve-plate columns, vibrating-plate extractors have been recommended (Rod, 1976). Rod has pointed out some advantages of this type of contactor for the oximation of cyclohexanene. 

The development of in situ electrolytic methods by Allied Chemical resulted in a novel unit, the electropulse column, in which mass transfer and electrolytic reduction are carried out simultaneously (25). The basic feature of the electropulse column, (Fig. 3), is the dual function of the horizontal perforated plates, acting as cathodes as well as pulse plates, and the introduction of vertical anode screens contained in porous ceramic sleeves. This design was found particularly suitable for Pu-U partitioning, since it permits operation with an aqueous-continuous phase, which is needed to maintain adequate electrical conductivity, while the organic to aqueous flow ratio is kept quite large to obtain a high plutonium concentration in the exiting aqueous stream. 

Cold pilot-plant tests are presently in progress using 2-inch diameter pulsed plate columns in continuous countercurrent flow. Synthetic Zr-Al high-level waste loaded with 0.2 g/L Ce(III) is being used as feed and 20 volume % DHDECMP in 2 1 decalin-DIPB as extractant. Cerium is being used as an americium simulant. To date, three complete cycles have been run including a solvent recycle wash with Na2C03. No major problems have been encountered. 

Mechanical reciprocation Karr Column Pulsed Packed Column Pulsed Perforated Plate Column... 

Pulsed plate or packed product of the density difference with the interfacial tension (Mg/m, mN/m) between 1 and 4 and number of theoretical stages needed >2. sensitive to contamination. Difficult to pulse large columns. 

Logsdail and Thornton6 correlated the performance of a pulsed plate column wilh seveml solvents to obtain the following general correlation Tor the overall HTU based on the coutinuous phase ... 

Pulsed columns Perforated plate packed Low HE IT No internal moving parts, but mechanicatly complex Many stages possible Karr column often less expensiw... 

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). 

Pulsed Columns. The efficiency of sieve-plate or packed columns is increased by the appHcation of sinusoidal pulsation to the contents of the column. The weU-distributed turbulence promotes dispersion and mass transfer while tending to reduce axial dispersion in comparison with the unpulsed column. This leads to a substantial reduction in HETS or HTU values. 

Eig. 14. Regions of operation of a pulsed, perforated-plate column (141). 

L. Burkhart, A. Survey of Simulated Methods for Modeling Pulsed Sieve-Plate Extraction Columns, UCRL-15101, Ames Laboratory, Iowa State University, Ames, Iowa, 1979. 

FIG. IS-S Pulsed columns a) Perforated-plate column with pump pulse generator, (h) Packed column with air pulser. 

A small perforated-plate column of conventional design was pulsed by Goldberger and Benenati [Jnd. Eng. Chem., 51, 641 (1959)] with marked improvement in mass-transfer rates. 

All ion gun optical columns are provided with deflection plates for scanning the ion beam over areas adjustable from a few square micrometers to many square millimeters. They have been adapted for pulsing by the introduction of additional deflection plates which rapidly sweep the beam across an aperture. By applying an ion beam bunching technique, ion pulses less than 1 ns wide can be produced. 

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