8.18. Extraction in a three-stage unit. The three-stage extractor shown in Figure 8.28 is used to extract the amine from a feed consisting of 40 wt% benzene (B) and 60 wt% trimethylamine (T). The solvent (water) flow to stage 3 is 5,185 kg/h and the feed flow rate is 10,000 kg/h. Solvent also is fed to stages 1 and 2. On a solvent-free basis, V is to contain 76 wt% T, and L3 is to contain 3 wt% T. Determine the required solvent flow rates S and S2 using a triangular diagram. Solubility data are in Exercise 8.14. V V V3 Stage 1 Stage 2 Stage 3 Solvent L3 Feed 4 S $2 Figure 8.28 Data for Exercise 8.18. TRIMETHYLAMINE-WATER-BENZENE COMPOSITIONS ON THE PHASE BOUNDARY Extract, wt% Raffinate, wt% TMA HO Benzene TMA HO Benzene 5.0 94.6 0.4 5.0 0.0 95.0 10.0 89.4 0.6 10.0 0.0 90.0 15.0 84.0 1.0 15.0 1.0 84.0 20.0 78.0 2.0 20.0 2.0 78.0 25.0 72.0 3.0 25.0 4.0 71.0 30.0 66.4 3.6 30.0 7.0 63.0 35.0 58.0 7.0 35.0 15.0 50.0 40.0 47.0 13.0 40.0 34.0 26.0 The tie-line data are: Extract, wt% TMA Raffinate, wt% TMA 39.5 31.0 21.5 14.5 13.0 9.0 8.3 6.8 4.0 3.5