Repeat part (a) of Exercise 14.10 for a two-stage stripping cascade and a two-stage enriching cascade, as shown in Figure 14.14. However, select just one set of reasonable cuts for the two stages of each case so as to produce 40 lbmol/h of final retentate.

Data From Exercise 14.10

A mixture of 60 mol% propylene and 40 mol% propane at a flow rate of 100 lbmol/h and at 25°C and 300 psia is to be separated with a polyvinyltrimethylsilane polymer (see Table 14.10 for permeabilities). The membrane skin is 0.1 mm thick, and spiral-wound modules are used with a pressure of 15 psia on the permeate side. Calculate the material balance and membrane area in m² as a function of the cut (fraction of feed permeated) for: 

(a) Perfect-mixing flow pattern and 

(b) Crossflow pattern.

Transcribed Image Text:

Feed A Memb 1 Memb 2 (d) Memb 3 Retentate Permeate Figure 14.14 Countercurrent recycle cascades of membrane separators. (a) Multiple-stage unit. (b) Two-stage stripping cascade. (c) Two-stage enrich- ing cascade. (d) Two-stage enriching cascade with addi- tional premembrane stage.