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

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A Case Study on Separation of IPA-Water Mixture by Extractive Distillation Using Aspen Plus 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 ©2016 ACCENTS 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 Sarita Kalla et al. (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 90 Temperature, C Temperature, 89 88 87 86 85 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 International Journal of Advanced Technology and Engineering Exploration, Vol 3(24) 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) 189 Sarita Kalla et al. 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 International Journal of Advanced Technology and Engineering Exploration, Vol 3(24) 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 Sarita Kalla et al.
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