Page 373 - Chemical process engineering design and economics

352 Chapter 6

Table 6.3.3 Continued

7. Calculate the extractor cross-sectional area, A, and the diameter, D, from Equa-
tions 6.32.7, 6.32.8 and 6.32.11.

8. Find (HETS)! at D, from Equation 6.32.12.
9. Calculate (HETS) at D from Equation 6.32.9.

10. Calculate the extractor height, Z, using Equation 6.32.6.

Example 6.8: Sizing a Karr Reciprocating-Plate Extractor___________

To illustrate the procedure for sizing a Karr extractor, we will use a process design
described by Drew [69]. The design requires separating a solution of methylene
chloride and methanol. The first step in the process is to contract.
Data
Feed Compostion:
Methylene Choride 2185 Ib/h (991 kg/h), 0.9851 mass fraction
Methanol 33 Ib/h (15.0 kg/h), 0.01488 mass fraction
Total flow rate 2218 Ib/h (1010 kg/h)
Methanol Recovery 8 = 95 % by weight
Methanol Distribution Coefficient (water/methylene chloride) = 2.0, estimated by
Drew (6.69)
3
Density in lb/ft 3 (kg/m )
Methylene Chloride 82.41 (1320)
Methanol 48.7 (780)
Water 62.43 (999)
C = 0.5 (in Equation 6.32.4)

To size the extractor, follow the procedure given in Table 6.33 using the
equations listed in Table 6.32. Because the methylene chloride solution is heavier
than water, it is introduced at the top and the water at the bottom of the extractor.
Refer to Figure 6.16 for the meaning of the numerical subscripts.
From Equation 632.4,
x 2K = (1 - 0.95) 0.01488 = 7.440xlO" 4

From Equation 6.32.1,

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