Korean Chem. Eng. Res., Vol. 44, No. 2, April, 2006, pp. 129-135 Sulfolane m i om i i o o 750-711 mte p 1 (2005 10o 22p r, 2006 1o 30p }ˆ) A Study on the Simulation of Toluene Recovery Process using Sulfolane as a Solvent Jungho Cho Department of Chemical Engineering, Dong Yang University, 1, Kyochon-dong, Poongi-eup, Youngu, Kyungboo 750-711, Korea (Received 22 October 2005; accepted 30 January 2006) l l n f sulfolanep n 2 p v ˆp pn l Š lp o s p Š lp v rl r qlp m. Sulfolane n pn v rp o ll ep NRTL ~ ep n mp n r p Aspen Plus 12.1p n m. sr p llv Š lp 99.8 wtímp, o l pp 99.65Í ˆ p pl. h Abstract In this study, computer modeling and simulation wors were performed to obtain nearly pure toluene product from toluene containing non-aromatic compounds using sulfolane as a solvent through an extractive distillation process. NRTL liquid activity coefficient model was adopted for phase equilibrium calculations and Aspen Plus release 12.1, a commercial process simulator, was used to simulate the extractive distillation process. In this study, it was concluded that the toluene product with a purity of 99.8 percent by weight and a recovery of 99.65 percent was obtained through an extractive distillation process. Key words: Extractive Distillation, Solvent, NRTL Liquid Activity Coefficient Model, Simulation, Modeling 1. Š lp l n v v rp s n r p, p, r r Ž r m nr n ˆp o m ol l mˆ n o p o n[1] p pl rp p Table 1 l ˆ l. Š l p s p rp lž r p s p Ž p p lž p mˆ p rp d ˆ l p nl l ov. v ˆp n p v l l p v ˆp n l l Œq np p n. Š l ˆrp p n p sulfolane p normal formyl morpholinep n v [2, 3] To whom correspondence should be addressed. E-mail: hcho@phenix.dyu.ac.r p n sulfolane n pn r[4]p pn rp s Š l p p. l l n f sulfolanep n v rp Table 1. The basic properties of toluene Property Value Normal boiling point (K) 351.470 Molecular weight 92.142 Standard liquid density (Kg/m 3 ) 870.980 Critical temperature (K) 591.720 Critical pressure (Pa) 4,108.700 Critical volume (m 3 /-mole) 0.316 Critical compressibility factor 0.26391 Acentric factor 0.2635 Heat of formation (J/-mole) 50,032 Free energy of formation (J/-mole) 122,240 129
130 s r s Š l p rl r qlp m. l l n v r p rp 2 p v ˆp r Fig. 1l ˆ m. ~ w v ˆp T-101p v ˆp f l p o p s s Š l p s ˆrp p n p sulfolanep n Š l p ˆrp p. ~ w v ˆp v ˆp p o o p n n l l v ˆ l p p, ˆ rl q pp ˆ l v m p p r l v l v el p column l p lv l v ˆp m. n n v rp o Fig. 2l rp ˆ l. Fig. 2l ˆ p rp d l p v s s pl s ˆrp p rp p n p p l s p l t l Š l p v ˆ ll s p raffinate f v ˆ ll., extract f v ˆ l llv n m n l ˆrp p Š l p w v ˆp n ˆ(T-102)p ˆr r l n ˆp t vrp tp. l l n m Š l p p lv, Š l p ˆ r p llv n p sulfolanep ˆr l llr l v ˆp. n ˆ Fig. 2. Principles of extractive distillation process using sulfolane as a solvent. p p l nr l l v edš(v-101)p n po ~w l l rn rl džp m l o w n p sulfolanep ll p p o n ˆ p nrm pr m p ov o p. v rp Š l o n f sulfolanep r tp Fig. 3[5] p n p sulfolane s p r s p ˆ pp e p m p q p ll ep p qn p lp p p. v rp r o sq l v Fig. 1. A schematic diagram of an extractive distillation process for toluene recovery from non aromatic components using sulfolane as a solvent. o44 o2 2006 4
Sulfolane n pn Š l rp l l 131 Fig. 3. Ternary liquid-liquid equilibria data and its prediction with NRTL model for sulfolane/benzene/normal heptane componentu v l l o pp l o n p o v ˆ n ˆp nrs p r m. 2. m n f sulfoanep n l Š l o v r p p o p o ll e p Renon Prausnitz r NRTL(non random two liquid mixture) ~ e[6]p n m. tp i l ~ ep pp (1)e p. τ i G i x ln γ i = ----------------------- + G i x x τ x G G ------------------ i τ i ------------------------- G x G x op (1)el τ i m G i e p mp o rp p qn f pp (2)e, (3)e p ˆ p. b i τ i = a i + ----- T G i = α i τ i exp ( ) op (2)el m T r m p, p p l l m ps v l, a i, a i, b i, b i a i p p qn v. Table 2l p s s n pp p p e p q p NRTL (1) (2) (3) Table 2. NRTL binary interaction parameters for each binary set Component I ˆ l. Aspen Plus r l q l p v p p qn l p p qn p n mp p l p el ll rp p p o UNIFAC[7] Optionp n m. 3. i }}r o Š l v rp p o l np r p Aspen Technology p Aspen Plus release 12.1p n m. r ˆp v ˆ p o vp Aspen Plus l q l p SUM-RATES v[8]p n m. pp Fig. 4 SUM-RATES vp pn v ˆ p p o ppp p erp ˆ p. Fig. 4l ˆ ppp v l v v, l v v, e s p l r s p pp (4)e (8)e pl ˆ l. M i, = exp X i, Component J ( )L i + exp ( Y i, )V i exp X i 1, D ( Y i +1, )( V i + 1 V i + 1 ) exp f i i = 1, NT, = 1, A(I, J) A(J, I) Toluene Benzene 2.1911 2.8852 Toluene MCH Toluene Octane Toluene Ethyl benzene Benzene MCH Benzene Octane 7.2344 2.8325 Benzene Ethyl benzene 1.4701 1.1017 MCH Ethyl benzene 1.6942 1.8888 Octane Ethyl benzene 1.5859 2.3937 Toluene Sulfolane 1.3984 0.3310 Benzene Sulfolane MCH Sulfolane 15.9860 56.1830 Octane Sulfolane 134.5789 43.2772 Ethyl benzene Sulfolane DMCH Sulfolane 0.9709 2.1132 ( )( L i D 1 L i ) 1, L B(I, J)/K B(J, I)/K 863.7308 1,123.9501 4.0625 43.2404 265.2227 142.116313 369.4598 549.2948 377.8787 197.2841 3,004.3057 1,247.0682 642.1115 515.4272 370.6175 539.4158 650.2850 1,050.9279 71.4079 223.1410 498.8326-50.4476 2,379.0299 1,524.4739 1,00 2,792.4300 649.1000 353.1500 1,192.1132 1,401.0628 V f i 1, Alpha 0.1215 0.5810 0.2000 (4) Korean Chem. Eng. Res., Vol. 44, No. 2, April, 2006
132 s r Table 3. Feed stream information Component Flow rate (Kg/hr) Weight Percent Toluene 660.5811 98.32 Benzene 11.411 10.21 Methyl cylcohexane 12.217 10.33 Dimethyl cyclohexane 14.470 10.67 Octane 11.747 10.26 Ethyl benzene 11.075 10.16 Temperature ( o C) 35.00 Pressure (bar) 12.50 Flow rate (Kg/hr) 671.901 Fig. 4. Schematic of a simple stage for the sum-rates algorithm. E i ) ) ) ) L V D L D V = L i H i + V i H i ( L i 1 L i 1 )H i ( V i + 1 V i + 1 )H i + 1 i = 1, NT Q i F L FL i H i Q i, = Y i, X i, ) ) F i + 1 l l F i ppp i p tp o p, L i ppp i p m o p, V i ppp i p m o p, Q i ppp i p tp e l p, T i ppp i p m, X i, p l ql p, Y i, p l ql p, p, NT p ˆ. V FV H i + 1 ln K i, i = 1, NT, = 1, ( ), S i = 1 exp X ( i, i = 1 NT ),, = 1 S i = 1 exp Y i,, i = 1, NT = 1 (5) (6) (7) (8) o p s m, o s p p Table 3l ˆ m. Aspen Plus r pn v rp Fig. 5l ˆ l. 3-1. }}r m Sulfolanep n pn l s Š l p ˆrp v ˆp Fig. 6l erp ˆ l. Fig. 6l ˆ p p p m q l 35 p r m. po q l p n pn s v ˆp er 75 [9]p l v ˆp pp 45Í r p. v ˆp p l Gerald[10] r v ˆp pp v ˆp ˆ ˆrp m s l o p r p f p Fig. 7l erp ˆ l. Fig. 7l ˆ p o p r 0.34 cp p r l v ˆ p p el p l v ˆp pp 45Í p rn l p 35 p r m. o o l n p tp o p 3.61:1 r m. p tlv v ˆp p s l Š l pp seˆ rp n o p r p. v ˆl q nr s p Table 4l r m. Table 4l ˆ p v ˆ p o o 21 l tp mp, n 7 p t p m. 40.51p o p 500 Kg/hr Fig. 5. Process flow sheet for the extractive distillation process of Aspen Plus 12.1. o44 o2 2006 4
Sulfolane n pn Š l rp l l 133 Table 4. Input data, specified parameters and output data for the simulation of extractive distillation column Input/output data and specified parameters Value Input data Feed flow rate (Kg/hr) 671.90 Solvent flow rate (Kg/hr) 2,418.50 Feed toluene composition (weight ) 98.32 Specified design and operating parameters Theoretical number of stage 35 Operating pressure at column top (bar) 1.20 Feedstoc feed tray location 21 Solvent feed tray location 7 Reflux ratio 40.51 Reflux rate (Kg/hr) 500.00 Output data Condenser duty (Kcal/hr) 57,279.50 Reboiler duty (Kcal/hr) 124,459.73 Toluene recovery ( ) 99.65 Toluene weight percent at raffinate 18.90 Fig. 6. A schematic diagram of the extractive distillation column. tp l n m Š l pp p lv. n ˆp r rp v ˆp lp v Fig. 8l n ˆ p erp ˆ l. Fig. 8l ˆ p p p m q l 10 p r m. po q l p n pn s v ˆp e r 40 p l v ˆp pp 25Í r p. n ˆl q nr s p Table 5l r m. Table 5l ˆ p n ˆp o o t p r 5 l tp m. 0.5p o p 329.75 Kg/hr lp ˆ r l Š lp 99.81 wtí p p lp pl. Fig. 7. Overall tray efficiencies as a function of average feedstoc liquid viscosity (Viscosity is average of feed as liquid at top and bottom temperatures of the column). lp Š lp 99.65Í llp raffinatel Š lp p 18.90Í llr. 3-2. m v ˆ l n l n Š lp llv. p extract p l l n l lv l n ˆp Fig. 8. A schematic diagram of the solvent recovery column. Korean Chem. Eng. Res., Vol. 44, No. 2, April, 2006
134 s r Table 5. Input data, specified parameters and output data for the simulation of solvent recovery column Input/output data and specified parameters Value Input data Feed flow rate (Kg/hr) 3,078.00 Feed toluene composition (weight ) 21.38 Specified design and operating parameters Theoretical number of stages 10 Operating pressure at column top (bar) 0.42 Feedstoc feed tray location 5 Reflux ratio 0.5 Reflux rate (Kg/hr) 329.75 Output data Condenser duty (Kcal/hr) 106,441.79 Reboiler duty (Kcal/hr) 166,432.84 Toluene weight percent at top product > 99.81 4. y o Table 3 p m,, o s p Š lp 99.8 wtí p p r p p r m., v ˆl p p p p Fig. 9l ˆ l. Fig. 9l ˆ p Š lp l l p pr p p l v p o tp p 21 p l mp v ˆ ˆrl 0.01 wtí p p pl. p n p sulfolanep p f n m p rp s p v ˆ pp p., Fig. 10p light ey componentp methyl cylcohexane heavy ey componentp Š l pp Separating factor tray numberp e p. Fig. 10l ˆ p v ˆ r l ~ separating facot p v l e v p lp l rp p Fig. 10. Plot of separating factor between toluene (heavy ey component) and methyl cyclohexane (light ey component) as a function of tray number. Fig. 11. Composition profile along the solvent recovery distillation column. Fig. 9. Composition profile along the extractive distillation column. o44 o2 2006 4 p. p p l ey component p s p l rp p p. p p l p q pp p p np o tp p 21 p tep separating factor p fluctuation p pl v pp o tp p o r r lrpp p. n ˆl p p p p Fig. 11l ˆ l. Fig. 11l ˆ p Š lp ˆ r l p 100Íp mp l ˆrl p ˆ v. p p n ˆl n m Š l pp q p lrp Š lp p pp
Sulfolane n pn Š l rp l l 135 Table 6. Material balance for the extractive distillation process 1 2 3 4 5 6 7 Crude feed Raffinate Rich solvent Feed to T-102 Toluene product T-102 bottom product Lean solvent recycled to T-101 Flow, Kg/hr 671.800 12.300 3,078.000 3,078.000 659.500 2,418.500 2,418.500 Toluene 660.581 2.321 658.261 658.261 658.260 0.001 0.001 Benzene 1.411 1.263 0.147 0.147 0.147 MCH 2.217 2.217 < 0.001 < 0.001 < 0.001 DMCH 4.470 4.763 0.007 0.007 0.007 Octane 1.747 1.736 0.010 0.010 0.010 Ethyl benzene 1.705 00 1.075 1.075 1.075 < 0.001 < 0.001 Solfolane 0.00 < 0.001 2,418.500 2,418.500 < 0.001 2,418.499 2,418.499 Temp. ( o C) 35.00 50.00 148.400 157.000 45.000 264.900 105.000 ˆ p. p o tp l p v pp pl., r~ rl v v Table 6 l r m. 5. l l l ~ r s ln nr p t n p 99.8 wtí p p Š lp n p sulfoalep n l v rp o r qlp m. l l e r qlp l v ˆp tp n p t o 3.61 p Š lp p p 99.56Í p p lp plp Š lp 99.81 wtí p p lp pl. T F i L i V i Q i T i : absolute temperature [K] : total feed flow rate to tray i [Kmole/hr] : total liquid flow rate from tray i [Kmole/hr] : total vapor flow rate from tray i [Kmole/hr] : heat added to tray I [MM Kcal/hr] : temperature of tray I [K] : number of components NT : number of trays N : number of experimental data points γ i : activity coefficient of component i x, x : liquid mole fraction of component and a i, a i, b i, a i, α i : binary interaction parameter in van der Waals mixing rule F p : total molar flow rate feeding to the V p : total vapor molar flow rate coming out of the L p : total liquid molar flow rate coming out of the S v,p : total vapor side draw flow rate coming of the S l,p : total liquid side draw flow rate coming of the x p, y p, z F,p : mole fraction contained in L p, V p and F p, respectively K,p f,p l,p v,p s,p h F,p h p H p q c,1 h 0 ' : K-value of component at the : molar flow rate of component feeding to the : liquid molar flow rate of component coming out of the : vapor molar flow rate of component coming out of the : side stream molar flow rate of component coming out of the : total molar enthalpy feeding to the : total liquid molar enthalpy coming out of the : total vapor molar enthalpy coming out of the : overhead condenser heat duty : saturated liquid molar enthalpy of overhead product y 1. http://www.hyundaicorp.co.r/global/prd_main.asp?soffice_id=14 2. http://www.gtchouston.com/articles/operationalí20experienceí 20withÍ20gt-btx.pdf 3. http://www.etis.net/balpyo/wor19/23.pdf 4. http://www.uop.com/obects/55 20Sulfolane.pdf 5. Sungin, L. and Hwayong, K., Liquid-liquid Equilibria for the Ternary Systems Sulfolane+Octane+Toluene, and Sulfolane+Octane +p-xylene at Elevated Temperatures, J. Chem. Eng. Data, 43, 358-361(1998). 6. Renon, H. and Prausnitz, J. M., Local Composition in Thermodynamic Excess Functions for Liquid Mixtures, AIChE J., 14, 135-144 (1968). 7. Larsen, B. L., Rasmussen, P. and Fredenslund. Aa., A Modified UNIFAC Group Contribution Model for Prediction of Phase Equilibria and Heats of Mixing, Ind. Eng. Chem. Res., 26, 2274-2286(1987). 8. Russel, R. A., A Flexible and Reliable Method Solves Singtower and Crude-distillation-column Problems, Chem. Eng., 90, 53-59 (1983). 9. http://www.gtchouston.com/articles/aromatics 20Design 20-20The 20Future 20is 20Now.pdf 10. Gerald, L.GK., Refinery Process Modeling: A Practical Guide to Steady State Modeling of Petroleum Processes, 1st ed., Kaes Enterprises, Inc.(2000). Korean Chem. Eng. Res., Vol. 44, No. 2, April, 2006