The Study of Structure Design for Dividing Wall Distillation Column

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1 Korean Chem. Eng. Res., Vol. 45, No. 1, February, 2007, pp r m o Š i m Çm k m d p e ( o 18p r, o 14p }ˆ) The Study of Structure Design for Dividing Wall Distillation Column Seung Hyun Lee and Moon Yong Lee School of Chem. Eng. & Tech, Yeungnam University, 214-1, Dae-dong, Kyungsan, Kyungpook , Korea (Received 18 November 2006; accepted 14 December 2006) k v ˆp s o shortcut p sp Fenske-Underwood ep 3 p v ˆ ll q rn p rk m. rk p l v ˆp o,, t r p o rp r p p p m. rk l p l s p lv v ˆ sp l 2 v r p pp o HYSYS n l k o s l l r e p m. rk v ˆp s l 2 v r 16Íl 65Í v l v rk ppp p m. v ˆl p r t r vp s l ps t r s p n o p p m, r l v ml p o p ESI l p l r p k pl. h Abstract This paper proposed a shortcut method for the structure design of dividing wall column based on the Fenske-Underwood equation by applying it on three conventional simple column configuration. It is shown that the proposed shortcut method can design the column structure including the feed tray, dividing wall section, and side-stream tray in a simple and efficient way in the initial design stage. Simulation study using HYSYS to compare the energy saving performance between the conventional sequential two column system and the dividing wall column designed by the proposed method shows that the proposed dividing wall column system saves from 16Í to 65Í more over the conventional one. It is also illustrated that the degree of energy saving improvement by the divided wall column mainly depends on the composition of intermediate component while the optimal energy consumption pattern to internal flow distribution on the dividing wall section is characterized by the ESI factor of the feed mixture. Key words: Dividing Wall Column, Internal Flow, Structure Design, Energy Saving, Thermally Coupled Distillation 1. v l ql 3 o rp l 2 v ˆ s n p. p rp r p s p d rl p, ~ w v ˆ l t r vp q rp pl. p v ˆl p ll r pp l tn npp l l v n rm. p rrp o l n v sl p l v l mp [1-4] l sl p l pp eˆ q rp m Fig. 1 p Petlyuk v ˆ s p [5-9]. Petlyuk v ˆp To whom correspondence should be addressed. mynlee@yu.ac.kr m m t lrp s l p f r r v r vp 1 rp m l p, m p ˆr ˆr p t p p op l t l r r, t r, r vp. p s Petlyuk v ˆ p v p v o l l v pp. v rp nrp np v k ˆ p k p l rrp sq. p Petlyuk v ˆp v r rp o l v ˆ(DWC: dividing wall column)p rk l [10-12]. v ˆp Petlyuk v ˆ ll r rl o srp rl ˆ l p p f Petlyuk v ˆp m t l eˆ ˆp. p s Petlyuk v ˆp m m 39

2 40 pd Ëp n Fig. 2. A schematic diagram of a dividing wall column. Fig. 1. A schematic diagram of Petlyuk column. t p k p l n p p nr p l n p qld tp f nrp np, 2 p v ˆp l Œq n r p qrp v. p qrl er l ql v ˆ p kv p l pv erp. pl tn po tp Petlyuk v ˆ v ˆp r v p sr l sr p p l nr s l ol p lv p o l r m s rp n r p. q v ˆp s rll l p l p lv pv kv v ˆl p o m r t r vp o p sl rp o rr p n r l p p. rp p o v ˆp rnl p l v p r m v ˆp err l p n p m m t p o Ž tn pq p l l tn. l l v ˆp s o l shortcut p p o d r p p rk p s l v ˆp p l m. 2. r o v ˆp s Fig. 2m p ˆ p. v rp p rp l 2 v r l v r n po sr p p. v ˆl o45 o k m l r v r r vp p k ~ s p v p p q (remixing) lr l o ll r pp skv. p v ˆl m p p p k l rp p m m t mp k~ s l v p p r l p p p l pv l l Fenske-Underwood ep pn l p p p re m. Fig. 2l p v ˆp s 4 p p. o p op m, t p, t p t p p p. m op 3 p r r r vp tp m p ˆr p r r v t r v, ˆr p t r v r vp. p p l p e l r r v t r vp e l t r v r vp s l p. p v ˆp sl p v ˆ lp rp Fig. 3 p ˆ p. p ll 1st columnp v ˆp m l 2nd column 3rd columnl p ˆr ˆr pp p v ˆl p t p Rectifying Stripping l. p v ˆl o p o m p o, t r v p o Fig. 3 p s l vp p p k p. v ˆl Fig. 2m p l p k p sq p Fig. 3l 1st columnp rl p 3 plk. shortcut l p s l m op k

v ˆp s l 41 Fig. 4. Process flow diagram for shortcut application in HYSYS. Fig. 3. A simple column configuration equivalent to DWC. p 1st columnp p p m op p 1st columnp q. Fig. 3p 1st columnp sl m op k l p 1st columnp rp p rk p rn p.

e p o p alkane l t n-pentane, n-hexane, n-heptanep n mp o p s p p 1atm, 45 kmol/h o p m. 3 v ˆ kl nr m p r p 99 molí, 94 molí, 99 molí r l m. s o HYSYSp shortcut e p Fig. 4p m.

4l p v ˆ lp p r A-C v ˆ(1st column)l ˆrl sq light key component(n- Pentane)m ˆrl sq heavy key component(n-heptane)p pp 0.01 r m. p r r Am r C l p mr q sp l v pp l p p el.

3 v ˆp s l 41 Fig. 4. Process flow diagram for shortcut application in HYSYS. Fig. 3. A simple column configuration equivalent to DWC. p 1st columnp p p m op p 1st columnp q. Fig. 3p 1st columnp sl m op k l p 1st columnp rp p rk p rn p. Fig. 3p v ˆ l s Fig. 2p v ˆ l l p rn v kp ˆp r~rp l v l p p p o Œp,, o p sr rl o p p. p o ˆp v ˆp s tn p Fenske-Underwood ep pn l p. l l s o l k Fenske-Underwood ep pn HYSYS p shortcut p n m. e p o p alkane l t n-pentane, n-hexane, n-heptanep n mp o p s p p 1atm, 45 kmol/h o p m. 3 v ˆ kl nr m p r p 99 molí, 94 molí, 99 molí r l m. s o HYSYSp shortcut e p Fig. 4p m. n-pentane(40 molí), n-hexane(20 molí), n-heptane (40 molí) nl e m Table 1l ˆ l. Fig. 4l p v ˆ lp p r A-C v ˆ(1st column)l ˆrl sq light key component(n- Pentane)m ˆrl sq heavy key component(n-heptane)p pp 0.01 r m. p r r Am r C l p mr q sp l v pp l p p el. A-B v ˆ(2nd column) B-C v ˆ(3rd column)p light heavy key component s p l r m. Table 1. Main structure of equivalent simple column configuration 1st column 2nd column 3rd column No. of tray Feed stage *The actual reflux ratio is set as double as the minimum reflux ratio. Table 1p ˆp v ˆp m p m t p 1st columnp 7, 2nd column 3rd columnp p 31 p r. p o p p t 4 p op t l p o 2nd columnp p 6 p p o 2nd columnp m 3rd columnp o p p 25 p. t r vp p o 2nd columnp p 15 l. v pn l HYSYS v ˆp Fig. 5l ˆ l. HYSYS m t ˆ l s r v k l ll r l p Petlyuk v ˆ pn l e p m. Fig. 5. Process flow diagram of DWC in HYSYS. Korean Chem. Eng. Res., Vol. 45, No. 1, February, 2007

4 42 pd Ëp n p v ˆl p lr p l r m Fig. 2p k t m op k p Fig. 5p Pre-Liq_Flow, Pre-Vap_Flow m. 3. y v ˆl k, v m m t op r~ edšp l v l q m p k ˆp np p rv tn p. l l m l op k p r r o l case-study e mp Fig. 6. Fig. 6l m p n l v t r p k p sq l r~ l v n p m p ep k p. m m op p 24 kmol/h, k p 51 kmol/h p l v p kj/h q k ˆ ol q 6 k l v p kj/h l r~ l v n 6 l p n. p l rp l v mlp ˆ po p p p. m l p k p v m l p p rm l tlv p o t p p eˆ m. p m l p p v v vl p l v rrp t p v o pp p q o ož Ž v rm. p v qrp pl l p v, l s v v l n s p l t p v eˆ n v p l rrp ˆ. Table 2l l 2 v ˆp n mp n l vk r s l p v ˆp l v p p m. e o l l 2 v ˆp p kl re v ˆp shortcut p Fenske-Underwood ep pn l mp r p o p s r p s ˆp nr k p p r m. Table 2l m p v ˆp l 2 v r l 34Í r p l v r p p k p. p l 2 v ˆl p rp ˆ q p r m m p v p ˆ p v o l r ˆl nr p l p. rk shortcut p v ˆl p s Fig. 7l ˆ l. Fig. 7(a) r r v r vp t r vp q lp q p lr p p p p. o45 o k Fig. 6. The energy consumption by internal flow distribution. Table 2. Structure and energy consumption of conventional sequential column process and DWC Pri-column Sec-column DWC No. of tray Feed stage 7 7 Reflux ratio Reboiler Duty(kJ/h) 1.463e e e006 Fig. 7(b)l t r vp s side-stream l p p p p. p rk shortcut p v ˆp s l r p lt. v ˆp p o p r

5 v ˆp s l 43 Table 3. Feed condition of ternary mixture for case study M 1 ESI = 1.04 M 2 ESI = 1.86 A: n-pentane B: n-hexane C: n-heptane A: n-butane B: i-pentane C: n-pentane A: i-pentane M 3 B: n-pentane ESI = 0.47 C: n-hexane *ESI (ease of separability index) F1 F2 F3 A : 0.4 B : 0.2 C : 0.4 A : 0.33 B : 0.33 C : 0.33 A : 0.2 B : 0.6 C : 0.2 Fig. 7. (a) Composition profile in prefractionator (b) Composition profile in Mainfractionator. pp p r v ˆp l n on. v ˆp o p Žk o l k alkane lp p p o s np p tp Table 3 p 9 v nl l l 2 v ˆ v ˆp p m. l o l p s p 1 atm, 45 kmol/h p r m p 99 molí, 94 molí, 99 molí r m. l 2 v ˆ v ˆp s rk shortcut p p s l m. Table 3 l ESI v α AB /α BC rp A-B B-C p np p p. m l, ESI < 1 p A-B p B-C l np. Table 4l p p p v ˆp n nl l pr p l v p p pp p r o p l 16Í, 65Í r p p p k p. tp r, t r, r r vp s s l v ˆp p p t r v Bp s p ƒv v ˆ rnl s l v r v p k p. p p v ˆl p l v p p t t r vp q p lr p f llv e. o p ESIl m p, ESI v p 1 l n l v r ƒvp p p. p p m l op r r v r vp tp k l t r vp tp r r v r vp α AB m α BC l 1 l ok v ˆp sl r s p p. nk, p t r vp o p ESI p 1l n v ˆ rn e p l v r p pp lp ppp k p., v ˆ p np rl, m m t l k m 1l n q p rp p F2-M1 case pl p. p n rp k m p v p nl F2-M1 case q rr p l v. p rp lk nl 1l ok rk s p p. k l p Table 4. Comparison of energy consumption in conventional sequential column process and DWC F1 F2 F3 2-TOP(10 6 kj/h) DWC(10 6 kj/h) Energy Saving( ) Liquid Split(Pre/Main) Vapor Split(Pre/Main) M M M M M M M M M Korean Chem. Eng. Res., Vol. 45, No. 1, February, 2007

44 pd Ëp n Fig. 8. Energy consumption pattern to internal flow distribution (X-axis: Pre-Liq_Flow, Y-axis: Pre-Vap_Flow, Z-axis: Reboiler Duty). l l r ol sr p. p n F1-M1 F2-M1 case rr p.

6 44 pd Ëp n Fig. 8. Energy consumption pattern to internal flow distribution (X-axis: Pre-Liq_Flow, Y-axis: Pre-Vap_Flow, Z-axis: Reboiler Duty). l l r ol sr p. p n F1-M1 F2-M1 case rr p. nl m p k l n l v Fig. 8l m. l p ESI p v o l o n l v p pp k p. ESI p 1l n o p n(v M1) r k l p l v r p qp, ESI < 1(v M3)p n n l v p p. p M2p n v ˆp l p m l l ov o v np qr p v, M3p n m l r e p rn p rrp v ppp p. 4. v ˆp l p s rp o l v ˆp sl r 3 p p v ˆ l sl l Fenske-Underwood p rn shortcut p rk m. rk p v ˆp ˆ s p s p r p p pl. o o45 o k s np p tp o l l v ˆp s l 2 v rl 65Í r p l v r lp ppp p m. v ˆp rnl t r vp s p ESI p 1l n ƒvp k pl. r l v p p s ESI l r p r p k pl. p r l v p 2006 l vqo rl p l vo ld. y 1U Salvador, H. and Arturo J., Controllability Analysis of Thermally Coupled Distillation Systems, Ind. Eng. Chem. Res., 38(10), (1999). 2. Agrawal, R., A Method to Draw Fully Thermally Coupled Distillation Column Configurations for Multicomponent Distillation, Ins. Chem. Eng. Trans IChemE., 78(3), (2000).

7 v ˆp s l Juan, L. B., Maria, N. B., Salvador, H., Vicente, R. and Jimenez, Energy-Efficient Designs of Thermally Coupled Distillation Sequences for Four-Component Mixtures, Ind. Eng. Chem. Res., 42(21), (2003). 4. Ben-Guang, R., Andrzej, K. and Ilkka, T., Synthesis of Heat- Integrated Thermally Coupled Distillation Systems for Multicomponent Separations, Ind. Eng. Chem. Res., 42(19), (2003). 5. Ivar, J. H. and Sigurd, S., Minimum Energy Consumption in Multicomponent Distilltation.2. Three-Product Petlyuk Arrangements, Ind. Eng. Chem. Res., 42(3), (2003). 6. Ivar, J. H. and Sigurd, S., Optimal operation of Petlyuk Distillation: Steady-state Behavior, J. Process Control., 9(5), (1999). 7. Jimenez, A., Ramirez, N., Castro, A. and Hernandez, S., Design and Energy Performance of Alternative Schemes to the Petlyuk Distillation System, Ins. Chem. Eng. Trans IChemE., 81(5), (2003). 8. Erik, A. W. and Sigurd, S., Operation of Integrated Three-Product (Petlyuk) Distillation, Ind. Eng. Chem. Res., 34(6), (1995). 9. Ivar, J. H. and Sigurd, S., Shortcut Analysis of Optimal Operation of Petlyuk Distillation, Ind. Eng. Chem. Res., 43(14), (2004). 10. Frigyes, L., David, E., Hiroshi, Y. and Colin, H., Kellogg Divided Wall Column Technology for Ternary Separation, The 5th International Symp. Tech.- Korea and Japan Seoul, Korea, (1999). 11. Abdul Mutalib, M. I. and Smith, R., Operation and Control of Dividing Wall Distillation Column, Part1: Degrees of Freedom and Dynamic Simulation, Trans IChemE., 76(3), (1998). 12. Michael, A. S., Douglas, G. S., James, M. H., Steven, P. R., Mohammed, S. S. and Dennis, E. O., Reduce Costs with Dividing-Wall Columns, CEP., 98(5), 64-71(2002). Korean Chem. Eng. Res., Vol. 45, No. 1, February, 2007

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