Karr columns

One of the chief characteristics of the Karr column is its high-volumetric efficiency when compared to other extractors. Volumetric-efficiency is defined as ... 

Karr, Holmes, and Cusack have given comparisons of the Karr column volumetric efficiency with other types of extractors. In Table 15-10 are data showing the values of HETS and volumetric efficiency over a range of column diameters from 1-36 in (0.025-0.9 m) Fig. 15-51... 

As with the other extractors, the final design of a Karr column depends on the scale-up from a pilot test. The following procedure is recommended. 

The Karr column is particularly well suited for systems which tend to emulsify since its uniform shear characteristics tend to minimize emulsion formation. It is also particularly well suited for corrosive systems (since the plates can be constructed of non-metals) or for systems containing significant solids (due to its large open area and hole size on the plates). Slurries containing up to 30 percent solids have been successfully processed in Karr columns. 

Fig. 9.5 Sieve tray columns with pulsing of the whole hquid content (left side) or of the whole plate package (right side, Karr column). The trays are meant to equalize the phase flows across the column cross section and to disperse the droplets as uniformly as possible.

Figure 14.13. Towers with reciprocating trays or with pulsing action, (a) Assembly of a 36 in. Karr reciprocating tray column (Chem. Pro. Co.), (b) Sieve trays used in reciprocating trays columns (left) large opening trays for the Karr column (middle) countermotion trays with cutouts (right) countermotion trays with downpipes for heavy phase, (c) Rotary valve pulsator, consisting of a variable speed pump and a rotary valve that alternately links the column with pairs of suction and discharge vessels, (d) Sieve tray tower with a pneumatic pulser [Proc. Int. Solv. Extr. Conf. 2, 1571 (1974)]. (e) A pulser with a cam-operated bellows.

Figure 6.22 Effect of reciprocating-plate frequency on NETS for the Karr column. (Source Ref. 64). 

To complete sizing the Karr column requires sizing the electric motor. The size of the electric motor to disperse one of the phases is small. Walas [51] states that a 1.5 hp (1.12 kW) motor is sufficient to agitate a Karr extractor 30 in (0.762... 

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... 

As with other agitated extractors, the fin design of a commercial-scale Karr column is based on pilot test data. The column vendor should be consulted for specific information. The following general procedure is recommended ... 

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). 

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

Mechanically Pulsed Column. The Karr column (Fig. 23) consists of perforated plates ganged on a common shaft which is oscillated by an external drive. The perforated area and hole size are much larger than in typical sieve plate operation. At high amplitude x frequency product in larger columns, the tendency for excessive backmixing can be curtailed by installation of some fixed baffles. 

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... 

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