A Case Study on Separation of IPA-Water Mixture by Extractive Distillation Using Aspen Plus

Home , Extractive distillation

International Journal of Advanced Technology and Engineering Exploration, Vol 3(24) ISSN (Print): 2394-5443 ISSN (Online): 2394-7454 Research Article http://dx.doi.org/10.19101/IJATEE.2016.324004 A case study on separation of IPA-water mixture by extractive distillation using aspen plus

Sarita Kalla, Sushant Upadhyaya*, Kailash Singh, Rajeev Kumar Dohare and Madhu Agarwal Department of Chemical Engineering, Malaviya National Institute of Technology, Jaipur, India

Abstract Extractive distillation is one of the popular methods being leveraged to separate isopropyl alcohol (IPA) from water present in waste stream in semi-conductor industries. In this context, the paper aims to carry out simulation study for separation of isopropyl alcohol-water azeotrope mixture using ethylene glycol as entrainer. In particular, temperature, pressure and concentration profile has been studied. Aspen plus® (version 8.8) has been used as simulation tool and optimum number of stages for the simulation turns out to be 42. The results show that top of the column contains IPA of 99.974 mol % purity and bottom product contains water-ethylene glycol mixture. Moreover, sensitivity analysis for different parameters and analysis of residue curve for ternary system have been also performed.

Keywords IPA-water, Extractive distillation, Simulation, Entrainer.

1. Introduction 2. Process simulation Isopropyl alcohol is generally used as the cleaning 2.1 Thermodynamic model agent and solvent in chemical industries. Because of Thermodynamic model is used to describe phase its cleaning property it is also known as rubbing equilibria properties of the system. For the design of alcohol. IPA is soluble in water and it forms chemical separation operations the phase equilibrium azeotrope with water at temperature 80.3-80.4 0C. properties like temperature, pressure and IPA and water forms a homogeneous minimum compositions are required. In phase equilibria boiling azeotrope, at 68.1-67.5 mole% (87.4-87.7 calculations the activity coefficients are used to mass %) under atmospheric conditions [1]. This close calculate the component non-ideal liquid behaviour boiling point azeotrope does not separate by [3]. In this simulation study Non-Random Two conventional distillation but may be competently Liquid (NRTL) model is used [4]. In this context, separated by extractive distillation. Figure 1 shows the xy plot and Txy plot for Isopropyl Alcohol-Water mixture. Extractive distillation is an important separation method for azeotrope mixture. In extractive 2.2 Residue curve analysis distillation, an entrainer (separating agent) is used to Residue Curve Analysis is useful in studying the revamp the relative volatility of component to be ternary system. Residue cure enumerate the change separated [2]. of column composition with time in the column. Figure 2 shows the residue curve for IPA-Water- In IPA-Water mixture, ethylene glycol used as Ethylene glycol, ternary system [5]. entrainer is combines with water and separated as bottom product and pure IPA is collected from the 2.3 Configuration top of the column. Due to high boiling point of the The simulation of IPA-Water mixture is carried out solvent the ethylene glycol-water mixture may be using RADFRAC distillation model from the Aspen easily separated in second distillation column. The Plus simulator. Simulation operating conditions are separated ethylene glycol can be reuse as entrainer in specified in Table 1. Figure 3 shows the flow sheet first distillation column. for simulation of extractive column. Input Stream F1 and FE1 shows the feed stream of IPA-Water mixture and entrainer, respectively and output stream D1 and B1 shows the pure IPA and ethylene glycol-water *Author for correspondence mixture, respectively [6] [7]. 187

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(a)

T-xy diagram for ISOPR-01/WATER 101

100 x 1.0 atm 99 y 1.0 atm 98 97 96

95 94 93 92 91

Temperature, C Temperature, 89 88 87 86

84 83 82 81 80 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 Liquid/vapor mole fraction, ISOPR-01 (b) Figure 1: (a) Vapour-liquid equilibrium plot for isopropyl alcohol-water (b) txy plot for isopropyl alcohol-water

Residue curve for ISOPR-01/WATER/ETHYL-01

0.05 Curve 1.0 (PRES = 1.01325 bar) 0.90 Curve 2.0 (PRES = 1.01325 bar) CurveMolefrac 3.0 WATER (PRES = 1.01325 bar) 0.15 Curve 4.0 (PRES = 1.01325 bar) 0.80 Curve 5.0 (PRES = 1.01325 bar) 0.25 Curve 6.0 (PRES = 1.01325 bar) 0.70 Curve 7.0 (PRES = 1.01325 bar) 0.35 Curve 8.0 (PRES = 1.01325 bar) 0.60 Molefrac ETHYL-01 0.45 0.50 0.55 0.40 0.65 0.30 0.75 0.20 0.85 0.10 0.95

0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 Molefrac ISOPR-01 Figure 2 Residue curve for ternary system 188

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Figure 3 Flow sheet for extractive distillation

Table 1 Simulation operating conditions 3.1 Temperature profile Operating variable Extractive column From steady state temperature profile shown in Feed Flow Rate (kmol/hr) 100 Figure 4, there is no significantly change in the Entrainer flow Rate 100 temperature of the column from moving down the (kmol/hr) 0 condenser segment until it goes up to reaction Feed Temperature ( C) 25 temperature i.e. 385 0C. From there sharply decrease Feed Pressure (atm) 1.3 0 Entrainer Temperature (0C) 72 in temperature up to 370 C and finally increase in Entrainer Pressure (atm) 1.1 the temperature in the direction of the reboiler Distillate Rate(kmol/hr) 50 section. Molar Reflux Ratio 1 Number of theoretical 42 3.2 Composition profile Stages Liquid mole fraction and Vapour mole fraction composition profile of IPA, Water and ethylene The binary mixture of IPA-Water has the following glycol is shown in the Figure 5 and Figure 6. mole fraction composition- IPA-0.5 (mole/mole), Water- 0.5 (mole/mole). Pure ethylene glycol adds as 3.3 Pressure profile entrainer or separating agent. From Pressure profile shown in the Figure 7, the pressure is increase with the number of stages in the 3. Results distillation column.

Block C1: Temperature Profile 415 410 Temperature K 405 400 395 390 385 380

Temperature K Temperature 375 370 365 360 355 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Stage

Figure 4 Temperature profile for steady state simulation (Stage wise)

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Block C1: Composition Profiles 1.0 Liquid mole fraction IPA 0.9 Liquid mole fraction WATER 0.8 Liquid mole fraction ETHYL-01 0.7

0.6

0.5

0.4 Mole fraction Mole 0.3

0.2

0.1

0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Stage

Figure 5 Liquid fraction composition profile for steady state simulation (Stage wise)

Block C1: Composition Profiles 1.0 Vapor mole fraction IPA 0.9 Vapor mole fraction WATER 0.8 Vapor mole fraction ETHYL-01 0.7

0.6

0.5

0.4 Mole fraction Mole 0.3

0.2

0.1

0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Stage

Figure 6 Vapour fraction composition profile for steady state simulation (Stage wise) 190

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Block C1: Pressure Profile 130000 Pressure N/sqm 125000

120000

115000

PressureN/sqm 110000

105000

100000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Stage

Figure 7 Pressure profile for steady state simulation (Stage wise)

4. Sensitivity analysis 4.1 Effect of molar reflux ratio on distillate (IPA Sensitivity analysis is a method of determining mole fraction) strength of relation between a given input and output As shown in Figure 8, the distillate mole fraction is [8]. In aspen plus process simulator, inputs are increases with reflux ratio and it becomes maximum allowed to vary and their effects on a set of results at reflux ratio value of 1. After this the distillate mole can be calculated. Sensitivity analysis has a handful fraction becomes constant. of benefits, like, studying the effect on process outputs in changing input variables, graphically 4.2 Effect of feed flow rate (IPA-Water) on shows the effects of input variables, validate that a distillate solution to a design specification is possible or not As shown in Figure 9, as the feed flow rate increases, etc. [9] [10]. the distillate mole fraction increases and it becomes constant at 0.028 kmol/sec.

Sensitivity Results Curve 1.000 0.995 D1 0.990 0.985 0.980 0.975 0.970

0.965 D1 D1 0.960 0.955 0.950 0.945 0.940 0.935 0.930 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 VARY 1 C1 COL-SPEC MOLE-RR

Figure 8 Result of effect of reflux ratio on IPA mole fraction by sensitivity analysis 191

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Sensitivity Results Curve 1.00 D1 0.95

0.90

0.85

0.80

0.75 D1 D1 0.70

0.65

0.60

0.55

0.50 0.012 0.014 0.016 0.018 0.020 0.022 0.024 0.026 0.028 0.030 0.032 0.034 0.036 0.038 0.040 0.042 VARY 1 F1 MIXED TOTAL MOLEFLOW KMOL/SEC

Figure 9 Result of effect of feed flow rate on IPA mole fraction by sensitivity analysis

Sensitivity Results Curve 0.994725 D1 0.994700

0.994675

0.994650 D1 D1

0.994625

0.994600

0.994575 298 300 302 304 306 308 310 312 314 316 318 320 322 324 VARY 1 F1 MIXED TEMPERATURE K

Figure 10 Result of effect of feed temperature on IPA mole fraction by sensitivity analysis

4.3 Effect of feed temperature on distillate Acknowledgment As shown in Figure 10, as the feed temperature None. increases, the distillate mole fraction is decreases due to exothermic nature of the reaction. Conflicts of interest The authors have no conflicts of interest to declare. 5. Conclusion This work laid the foundation of operating conditions References [1] Van Baelen G, Vreysen S, Gerbaud V, Rodriguez- for an extractive distillation process for ethylene Donis I, Geens J, Janssens B. Isopropyl alcohol glycol as entrainer. At the given operating conditions, recovery by heteroazeotropic batch distillation. 2010. the simulation results exhibits 99.974 mol % purity of 979-86. IPA at the top of the column. The results of the [2] Lei Z, Chen B, Ding Z. Special distillation processes. sensitivity analysis, therefore, reveal the effect of Elsevier; 2005. molar reflux ratio, feed temperature and feed flow [3] Gebreyohannes S, Neely BJ, Gasem KA. One- rate on the IPA purity. Isopropyl alcohol obtained in parameter modified nonrandom two-liquid (NRTL) this way could be used as solvent in different activity coefficient model. Fluid Phase Equilibria. applications and as cleaning agent. 2014; 379:196-205. [4] ASPENTECH AG. Running a process model. ASPEN

Technology, Burlington. 2010. 192

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[5] Luyben WL. Distillation design and control using Aspen simulation. John Wiley & Sons; 2013. Dr. Kailash Singh received his Ph.D. [6] Luyben WL, Chien IL. Design and control of from Curtin University of Technology, distillation systems for separating azeotropes. John Australia, M.Tech. from IIT Kanpur Wiley & Sons; 2011. B.E. from University of Roorkee. He is [7] Brüggemann S, Marquardt W, Technische Hochschule currently Associate Professor and Head Aachen (Germany). Lehrstuhl fuer Prozesstechnik; in the Department of Chemical Shortcut design of extractive distillation columns. Engineering, MNIT. His research areas [8] Saltelli A, Chan K, Scott EM, editors. Sensitivity are Modelling and Simulation, analysis. New York: Wiley; 2000. Advanced Process Control. He has published numerous [9] Schefflan R. Introduction to Aspen plus, in teach papers of International and National repute in his research yourself the basics of Aspen Plus™, John Wiley & field. Sons; 2011 NJ, USA. [10] Giwa A. Sensitivity analysis of ETBE production Dr. Madhu Agarwal obtained her Ph.D. process using Aspen PLUS. Sensitivity analysis of from MNIT, Jaipur, M.Tech and B.Tech ETBE production process using aspen PLUS. 2013; from Calcutta University. She is currently 3(1):293-303. Assistant Professor at Department of Chemical Engineering, MNIT. Her research areas are Modelling and Sarita Kalla obtained her B.E. from to Simulation, Bioprocess Engineering, University of Rajasthan, Jaipur and Biofuels, Biotechnology, Fluid Particle Mechanics, M.Tech. from Aligarh Muslim Adsorption, Wastewater Treatment. She is actively working University, Aligarh. She is presently in the area of bio fuels and water treatment. Published more pursuing Ph.D from Chemical than twenty papers in Journals and forty papers in Engineering Department, MNIT on Air conferences. She is working on two sponsored research Gap Membrane Distillation. projects on Fluoride removal and fluoride detection. Guiding B.Tech. & M.Tech. Students for their final year Email:[email protected] projects and Dissertation work and her four Ph.D. Students are working on alternative energy and water treatment. Dr. Sushant Upadhyaya obtained his Ph.D. (Chemical Engineering) from Rajeev Kumar Dohare received his MNIT, M.Tech. and B.Tech. in Ph.D from MNIT, Jaipur, B.E from NIT, Chemical Engineering from UPTU, Surat in 2002 and M.Tech from Aligarh Lucknow. He is presently Assistant Muslim University, Aligarh, India in 2006 Professor in Department of Chemical with first class. Now he is working as Engineering at MNIT. His research Assistant Professor in the Department of areas are Transport Phenomena, Chemical Engineering at Malaviya Modelling and Simulation, Wastewater Treatment, National Institute of Technology Jaipur. Computational method for linear/non-linear problems, His Research areas are process modelling, simulation and Polymer Process Modelling, Mass Transfer, Membrane control, solid waste management, fluid mechanics, and Separation Piping Engineering, Numerical Modelling, processes optimization. He has published several papers of Computational Fluid Dynamics (CFD). He has published International and National repute in his research field. several papers of International and National repute in his research field.

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