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Separation Process Principles- 2n - Seader &amp; Henley - Solutions Manual

# The pressure drop is not critical because of the much

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Unformatted text preview: s velocity at 70% of flooding from above = 13 ft/s for Montz Gas viscosity = 0.012 cP and gas density = 0.0370 lb/ft3. From Eq. (6-114), for NOR PAC, N ReV = uV DP ρV (20)(0.012)(0.0370) KW = (0.957) = 19, 900 (1 − ε ) µV (1 − 0.947 ) (0.012)(0.000672) For Montz, (13)(0.00459)(0.0370) N ReV = (0.990) = 3,870 (1 − 0.930 ) (0.012)(0.000672) From Eq. (6-113), for NOR PAC, Ψo = Cp 64 1.8 64 1.8 + 0.08 = 0.350 + = 0.287 N ReV N ReV 19,900 19,9000.08 For Montz, Ψo = 0.295 64 18 . + = 0.279 3,870 3,8700.08 Exercise 7.52 (continued) Analysis: (e) Stripping section (continued) From Eq. (2), for NOR PAC, 2 ∆Po a uV ρV 1 86.8(0.3048) 202 (0.0370) 1 = Ψo 3 = 0.287 = 2.15 lbf/ft3 or 0.0149 psi/ft 3 lT ε 2 g c KW 0.947 2(32.2) 0.957 For Montz, ∆Po 300(0.3048) 8.4 2 (0.0370) 1 = 0.279 = 311 lbf/ft3 or 0.0216 psi/ft . 3 lT 0.930 2(32.2) 0.990 From Eq. (1), for NOR PAC, with hL = 0.0269 m3/m3 and liquid Froude number = 4.28x10-4 ∆P 0.947 − 0.0269 = 0.0149 lT 0.947 3/ 2 exp 1/ 2 13300 ( 4.28 ×10−4 ) = 0.0150 psi/ft 3003/ 2 From Eq. (1), for Montz, with hL = 0.0341 m3/m3 and liquid Froude number = 6.39x10-4 ∆P 0.930 − 0.0341 = 0.0216 lT 0.930 1.5 exp 1/ 2 13300 6.39 × 10−4 ) = 0.0218 psi/ft 3/ 2 ( 300 Summary of Results: Column diameter, ft: Rectifying section Stripping section Packed height, ft Rectifying section Stripping section Total Pressure drop, psi NOR PAC Montz 4.3 3.4 5.3 4.2 6.3 20.2 26.5 0.38 2.9 2.1 5.0 0.093 From these results, the column diameter for NOR PAC would be 4.5 ft without swaging. The column diameter for Montz would be 5.5 ft without swaging. The column height for NOR PAC, allowing 4 ft for disengagement, 2 ft for feed entry, and 10 ft for sump at the bottom would be 42.5 ft or say 43 ft. Similarly, the column height for Montz would be 21 ft. Exercise 7.52 (continued) Analysis: Summary (continued) The above may be compared with the existing plate column of Exercise 7.41: Column diameter, ft Column height, ft Pressure drop, psi Plate column 6.0 36 0.8 NOR PAC 4.5 43 0.38 Montz 5.5 21 0.093 The packed columns are smaller in diameter, the NOR PAC column significantly smaller. The Montz structure packing column is shorter in height and has much less pressure drop. The NOR PAC rings random packing column is taller and has significantly more pressure drop than the column with Montz packing. The pressure drop is not critical. Because of the much higher cost for Montz packing and the much smaller diameter for the NOR PAC column, it is probable that economics would favor the NOR PAC column. Exercise 7.53 Subject: Distillation of a mixture of benzene and toluene in a packed column. Given: Conditions in Example 7.1, but using 50-mm Hiflow rings at 70% of flooding. Assumptions: Constant molar overflow. Partial reboiler is an equilibrium stage. Find: (a) Liquid holdup. (b) Column diameter. (c) HOG. (d) Packed height. (e) Pressure drop. Advantages of packed column over trayed column. Analysis: At the top of the column, L = RD =1.59(275) = 43...
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