ch05 - CHAPTER 5 SOLUTIONS 5.1 From the Chemical Market...

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5-1 CHAPTER 5 SOLUTIONS 5.1 From the Chemical Market Reporter , Aug. 17, 1998 Price, $/lb MW, lb/lbmol Ethylene 0.215 28.05 Ethylene glycol 0.26 62.07 NaOH 1.70 40.08 Cl 2 0.128 70.91 Conventional reaction path: C 2 H 4 + 1/2 O 2 + H 2 O CH 2 (OH)CH 2 (OH) Assuming negligible cost for O 2 , H 2 O: G r o s s p r o f i t p e r l b E G = 1 x 0.26 - 28 05 62 07 0 215 . . . x = $0.163/lb EG Using NaOH, Cl 2 : C 2 H 4 + Cl 2 + 2NaOH CH 2 (OH)CH 2 (OH) + 2NaCl Assuming negligible value for the product NaCl: G r o s s p r o f i t = 0.163 - 70 91 62 07 0128 24008 62 07 170 . . . (.) . . xx = - $2.173/lb EG For this reaction path to be viable, cheap sources of NaOH and Cl 2 and/or a demand for NaCl, at a fairly high price, are necessary.
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5-2 5.2 a. The following vapor pressures were graphed using ASPEN PLUS. The graph can be reproduced using the file EXER5-2.bkp on the CD-ROM. As in Example 5.1, ETBE is much less volatile than the other species. Hence, the conclusions are identical. b. In one distribution of chemicals, as illustrated below, ethanol is fed to the reactive distillation column near the top, above the trays containing catalyst. The mixed-C 4 stream is fed below the reacting section. ETBE, the least volatile species, concentrates in the bottoms product, along with unreacted ethanol. During process synthesis, it is reasonable to provide a small excess of 1-butene and to assume that the ethanol is completely consumed. The lighter C 4 compounds concentrate in the distillate. Catalyst Section Unreacted C 4 ’s ETBE Ethanol Ethanol Mixed-C 4 stream PL vs Temperature Temperature F 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 PL psi 50 100 150 200 250 LIQUID 1-BUTENE LIQUID 1,3-BUTA LIQUID CIS-2-BU LIQUID ETBE
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5-3 5.3 ASPEN PLUS Flowsheet – simulation results can be reproduced using the file EXER5.3.bkp on the CD-ROM. Calculation Sequence SEQUENCE USED WAS: $OLVER01 H1 F1 SP1 C2 *R1 M2 (RETURN $OLVER01) Tabulated Results Purge/Recycle Ratio 0.1 40.67 165.0 18.32 0.033 0.060 0.08 41.61 189.5 16.48 0.036 0.067 0.06 42.63 226.8 14.47 0.041 0.076 0.04 43.75 294.4 12.27 0.049 0.090 0.02 45.05 476.8 9.73 0.062 0.113 Care should be exercised in interpreting these results as ASPEN PLUS reported convergence errors at each purge/recycle ratio. As expected, at the elevated pressure (as compared with Example 5.3), the conversion to product is higher, the recycle flow rate is reduced, as is the purge flow rate. Also, as expected, the mole fractions of Ar and CH 4 in the purge stream are increased. R1 S7 FEED S2A S2B H1 S4 F1 S5 PROD SP1 PURGE S6 C2 M2
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5-4 5.4 Alternative 1 The CHEMCAD simulator is used to make the material balance with following process topology (flowsheet, where negative numbers are streams out) based on Fig. 5.13. Equipment No. Equipment Model Equipment Name Stream Numbers 1 MIXE Mixer 1 2 14 20 -4 2 CONT H2 cont 4 -15 3 REAC reac1 15 -5 4 GIBS reac2 5 -6 5 FLAS flash 6 -7 -8 6 DIVI purge 7 -9 -10 8 CSEP sep1 8 -11 -12 9 CSEP sep2 12 -13 -17 10 CSEP sep3 17 -14 -18 11 COMP comp1 10 -20 Note the use of two reactor models in series. The first reactor, reac1 modeled by REAC, converts 70% of the toluene to benzene by the irreversible reaction: H 2 + C 7 H 8 CH 4 + C 6 H 6 The H 2 -to-toluene molar ratio in the feed to reac1 is specified as 4. This is established by
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ch05 - CHAPTER 5 SOLUTIONS 5.1 From the Chemical Market...

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