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Separator Design 347

The HETS will then be higher then at the minimum point. To estimate the design
HETS, select an HETS that is 20% higher than the minimum value. Also, given in
Table 6.3 1 is the maximum volumetric efficiency, defined by Equation 6.31.

Vc+V D
T!V = ———— (6.31)
HETS

Karr and Lo [63] have developed simple scaling rules for the Karr extractor.
To scale HETS from one column size to another, requires that the plate spac-
ing, amplitude, and total volumetric flow rate per unit area be kept the same for
each extractor. They found for a high interfacial-tension system such as the o-
xylene, acetic-acid, water system, that

(HETS) 2 ( D 2y 38
————— = 1 —— I (6.32)

For a low interfacial-tension system such as MIBK, acetic acid, water, the expo-
nent is 0.36, only slightly different.
To scale the reciprocating frequency, they also developed the following rela-
tion.

0) 2 f D , V- 16
— = 1 —— I (6.33)
co, I D 2 )

Equations 6.31 to 6.33 have been successfully used to scale many Karr extractors
from pilot plant experiments to commercial scale extractors up to 1 .53 m (5.02 ft)
in diameter [61].

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