Simulation of Ethanol Dehydration Using Cyclohexane as an Entrainer

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1 Simulation of Ethanol Dehydration Using Cyclohexane as an Entrainer 2013 년 9 월 23 일 ( 월 ) 공주대학교화학공학부조정호 Limit of Distillation by Azeotrope 1.0 Ethanol / Water System Distillation range is restricted by the azeotropic point. r Mole Fraction of Ethanol Vapo Liquid Mole Fraction of Ethanol Binary azeotropic mixtures, such as ethanol/water and IPA/water, can be separated into their pure components by distillation by the addition of a third component, so called the entrainer, which forms a ternary azeotrope with a lower boiling point than any binary azeotrope Azeotropic Distillation 2

2 Separation of Azeotropic Mixture Shift the Azeotropic Point by Changing Pressure. Supercritical Fluid Extraction Using Supercritical CO 2 Solvent Pervaporation Method: Proposed by SKEC Vacuum Distillation Azeotrope between ethanol and water disappears at 11.5kPa. Add the Third Component. Azeotropic Distillation: Entrainer (Benzene, CHX, NC5) Extractive Distillation: Solvent (Ethylene Glycol) Azeotropic Distillation 3 Azeotropic vs. Extractive Distillation (1) Azeotropic distillation By forming a ternary heterogeneous azeotrope lower than any other binary azeotropic temperatures, nearly pure ethanol can be obtained as a bottom product in an azeotropic distillation column. Ethanol is obtained as a bottom product from an azeotropic distillation column using an entrainer such as benzene or normal pentane. Extractive distillation By adding a solvent which is exclusively familiar with a wanted component in a feed mixture, a desired component can be obtained in an extractive distillation column overhead. Ethanol is obtained as a top product from an extractive distillation with ethylene glycol solvent. Azeotropic Distillation 4

3 Azeotropic vs. Extractive Distillation (1) RECYCLE UPPER PHASE LOWER PHASE SOLVENT PURE ETHANOL FEED FEED PURE ETHANOL Azeotropic Distillation Extractive Distillation Azeotropic Distillation 5 Principles of Azeotropic Distillation Ethanol 1.0 P.9 A II F.8.7 A : o C C : o C B : o C D : o C.6.5 B G V R I D W III.1 C Benzene Only mixtures in region II will give the desired products of pure ethanol as a bottom product. Water Aqueous ethanol can be separated into their pure components by distillation by the addition of a third component, so called the entrainer, which forms a ternary heterogeneous azeotrope with a lower than any other binary azeotropes. Azeotropic Distillation 6

4 How to Select an Entrainer Ethanol P B II I R A G F III V D A : o C B : o C C : o C D : o C W Ether C Water In this case, pure ethanol cannot be obtained since G is in region III. Azeotropic Distillation 7 Homogeneous Azeotrope (1): Ethanol-Water Temperature ( o C ) Mole Fraction of Ethanol Azeotropic Distillation 8

Homogeneous Azeotrope (2): Ethanol-Benzene 82 80 Temperature ( o C ) 78 76 74 72 70 68 66 0.0 0.2 0.4 0.6 0.8 1.

5 Homogeneous Azeotrope (2): Ethanol-Benzene Temperature ( o C ) Mole Fraction of Ethanol Azeotropic Distillation 9 Heterogeneous Azeotrope (3): Benzene-Water Azeotropic Distillation 10

6 Theory of Azeotropic Distillation (I) Ethanol / Benzene Benzene / Water Ethanol / Water Azeotropic Distillation 11 Theory of Azeotropic Distillation (II) Ethanol Water is concentrated on vapor side. Highly interaction Ethanol Benzene H 2 O Dew point temperature Benzene valley H 2 O Azeotropic Distillation 12

7 Theory of Extractive Distillation Ethanol Ethanol is concentrated on vapor side. Ethanol H2O EG Highly interaction EG H 2 O Azeotropic Distillation 13 Configuration of Azeotropic Distillation Recycle stream Decanter Feed Concentrated ethanol Upper phase Lower phase Concentrator Azeo Column Stripper Waste water Pure ethanol Waste water Azeotropic Distillation 14

8 Problem: Ethanol Dehydration Feedstock information Feed Composition 1) Ethanol : 10mole% 2) Water : 90mole% Feed Condition 1) Inlet Temperature : 25 o C 2) Inlet Pressure : 200 kpa Flow Rate 1) 100 Kg-mole/hr Entrainer: Cyclohexane Cooling Medium: Cooling water 1) In/Out Temperature : 32 o C/40 o C 2) Decanter Operating Temperature : 45 o C Azeotropic Distillation 15 Simulation Procedure Step 1: Selection of Proper Thermo Model & Construction of Binodal Curve Step 2: Finding Binary & Ternary Azeotropic Points Step 3: Construction of Binary & Ternary Residual Curves Step 4: Concentrator Simulation Step 5: Azeotropic Column Simulation Step 6: Azeo + Dryer(Stripper) Column Simulation Step 7: Simulation of Overall Azeotropic Distillation Unit Step 8: Optimization of Ethanol Dehydration Process Azeotropic Distillation 16

9 Step 1a: Selection of Proper Thermo. Model NRTL. This model has up to 8 adjustable binary parameters that can be fitted to data. ln i j G k G ji G ij ki ji x ijj x k j a ijj j bij T ij k x G j G c T kj ij ij 2 ij x exp T k ij ij l k x G l G lj kj x k lj Azeotropic Distillation 17 Step 1b: Construction of Binodal Curve CHX Binodal Curve Construction using NRTL ) Water 0.9 2) Ethanol 0.8 3) Cyclohexane 0.7 Temperature = 45 o 0.6 C 0.5 Binary Interaction Parameters Ethanol 0.1 Plait point Water Comp I Comp J A(I,J) A(J,I) (I,J) , , Azeotropic Distillation 18

10 Step 2a: Finding Azeotropes (Ethanol+Water) Step-2a.prz Ethanol= mole fraction Azeotropic Distillation 19 Step 2a: Finding Azeotropes (Ethanol+Water) STREAM ID AZEO L V NAME PHASE LIQUID LIQUID VAPOR THERMO ID NRTL01 NRTL01 NRTL01 FLUID MOLAR FRACTIONS 1 ETHANOL H2O CH TOTAL RATE, KG-MOL/HR TEMPERATURE, C PRESSURE, KG/CM ENTHALPY, M*KCAL/HR E E MOLECULAR WEIGHT MOLE FRAC VAPOR MOLE FRAC LIQUID Azeotropic Distillation 20

11 Step 2b: Finding Azeotropes (Ethanol+CHX) Step-2b.prz Ethanol= mole fraction Azeotropic Distillation 21 Step 2b: Finding Azeotropes (Ethanol+CHX) STREAM ID AZEO L V NAME PHASE LIQUID LIQUID VAPOR THERMO ID NRTL01 NRTL01 NRTL01 FLUID MOLAR FRACTIONS 1 ETHANOL H2O CH TOTAL RATE, KG-MOL/HR TEMPERATURE, C PRESSURE, KG/CM ENTHALPY, M*KCAL/HR E E MOLECULAR WEIGHT MOLE FRAC VAPOR MOLE FRAC LIQUID Azeotropic Distillation 22

12 Step 2c: Finding Azeotropes (Water+CHX) Step-2c.prz Cyclohexane= mole fraction Azeotropic Distillation 23 Step 2c: Finding Azeotropes (Water+CHX) STREAM ID AZEO L V NAME PHASE LIQUID LIQUID VAPOR THERMO ID ALCO01 ALCO01 ALCO01 FLUID MOLAR FRACTIONS 1 ETHANOL H2O CH TOTAL RATE, KG-MOL/HR TEMPERATURE, C PRESSURE, KG/CM ENTHALPY, M*KCAL/HR E E MOLECULAR WEIGHT MOLE FRAC VAPOR MOLE FRAC TOTAL LIQUID MOLE FRAC LIQUID N/A MOLE FRAC LIQUID N/A Azeotropic Distillation 24

13 Step 2d: Finding Azeotropes (Ethanol+Water+CHX) Step-2d.prz Ethanol=0.3239, Water= mole fraction Azeotropic Distillation 25 Step 2d: Finding Azeotropes (Ethanol+Water+CHX) STREAM ID AZEO L V NAME PHASE LIQUID LIQUID VAPOR THERMO ID ALCO01 ALCO01 ALCO01 FLUID MOLAR FRACTIONS 1 ETHANOL H2O CH TOTAL RATE, KG-MOL/HR TEMPERATURE, C PRESSURE, KG/CM ENTHALPY, M*KCAL/HR E E MOLECULAR WEIGHT MOLE FRAC VAPOR MOLE FRAC TOTAL LIQUID MOLE FRAC LIQUID N/A MOLE FRAC LIQUID N/A Azeotropic Distillation 26

14 Results for Step Ethanol 0.1 A: o C, B: o C C: o C, D: o C 0.9 A B D Entrainer Selection Criteria CHX C Water Azeotropic Distillation 27 Step 3: Construction of Residual Curves Ethanol 0.1 II A Entrainer Selection Criteria 2 Only mixtures in region II will give the desired products of pure ethanol as a bottom product B D CHX 0.8 I III C Water 0.2 Azeotropic Distillation 28

15 Step 3: Construction of Residual Curves Ethanol A II 0.5 B D C III Cyclohexane Azeotropic Distillation 29 I Water Step 3a: Feed having composition in region I Region 01.prz Feedstock Composition Mole % Water Ethanol CHX Total Flow Top Product Composition Mole % Water Ethanol CHX Total Flow Bottom Product Composition Mole % Water 1.00 Ethanol - CHX Total Flow Azeotropic Distillation 30

16 Step 3a: Stream Summary STREAM ID Composition Mole fraction NAME Water PHASE Ethanol LIQUID LIQUID LIQUID THERMO ID NRTL01 NRTL01 NRTL01 CHX FLUID MOLAR FRACTIONS 1 WATER E-02 2 ETHANOL CH TOTAL RATE, KG-MOL/HR TEMPERATURE, C PRESSURE, BAR ENTHALPY, M*KJ/HR MOLECULAR WEIGHT MOLE FRAC VAPOR MOLE FRAC TOTAL LIQUID MOLE FRAC LIQUID MOLE FRAC LIQUID E-03 Azeotropic Distillation 31 Step 3b: Feed having composition in region III Region 03.prz Feedstock Composition Mole % Water Ethanol CHX Total Flow Top Product Composition Mole % Water Ethanol CHX Total Flow Bottom Product Composition Mole % Water Ethanol 0.33 CHX 0.67 Total Flow Azeotropic Distillation 32

17 Step 3b: Stream Summary STREAM ID Composition Mole fraction NAME Water PHASE Ethanol LIQUID LIQUID LIQUID THERMO ID NRTL01 NRTL01 NRTL01 CHX FLUID MOLAR FRACTIONS 1 WATER ETHANOL E-03 3 CH E-03 TOTAL RATE, KG-MOL/HR TEMPERATURE, C PRESSURE, BAR ENTHALPY, M*KJ/HR MOLECULAR WEIGHT MOLE FRAC VAPOR MOLE FRAC TOTAL LIQUID MOLE FRAC LIQUID E-03 MOLE FRAC LIQUID Azeotropic Distillation 33 Step 3c: Feed having composition in region II Region 02.prz Feedstock Composition Mole % Water 5.00 Ethanol CHX Total Flow Top Product Composition Mole % Water Ethanol CHX Total Flow Bottom Product Composition Mole % Water 0.00 Ethanol CHX 1.00 Total Flow Azeotropic Distillation 34

18 Step 3c: Stream Summary STREAM ID Composition Mole fraction NAME Water PHASE Ethanol LIQUID LIQUID LIQUID THERMO ID NRTL01 NRTL01 NRTL01 CHX FLUID MOLAR FRACTIONS 1 WATER ETHANOL CH E-11 TOTAL RATE, KG-MOL/HR TEMPERATURE, C PRESSURE, BAR ENTHALPY, M*KJ/HR MOLECULAR WEIGHT MOLE FRAC VAPOR MOLE FRAC LIQUID Azeotropic Distillation 35 Step 4: Concentrator Simulation Basis: Feed = 100 Kg-mole/hr x F = 0.10 Feed Concentrated ethanol Ethanol Mole Balance F x F = D x D (Nearly Pure Water at Column Bottom) Concentrator Waste water F xf F x D x D x azeo F Azeotropic Distillation 36

19 Initial Estimates for Concentrator Azeotropic Distillation 37 Product Specifications & Variables Azeotropic Distillation 38

20 Stream Summary Around Concentrator STREAM ID NAME PHASE LIQUID LIQUID LIQUID THERMO ID NRTL01 NRTL01 NRTL01 FLUID MOLAR PERCENTS 1 ETHANOL WATER TOTAL RATE, KG-MOL/HR TEMPERATURE, C PRESSURE, KG/CM ENTHALPY, M*KCAL/HR MOLECULAR WEIGHT MOLE FRAC VAPOR MOLE FRAC LIQUID Azeotropic Distillation 39 Step 5a: Azeotropic Column Simulation V F 2 F Composition of Stream F Component Mole % Ethanol Water Flow Rate K-mol/hr R Azeo Column W P Azeotropic Distillation 40

21 Step 5b: Decanter Simulation V R W Assume OVHD Vapor Composition, V around ternary azeotrope Mole % CHX Ethanol Water Azeotropic Distillation 41 Step 5b: Decanter Simulation (Continued) TITLE PROJ=AZEOTROPE, PROB=FLASH,USER=J.H.CHO PRINT INPUT=ALL, RATE=M, FRACTION=M, PERCENT=M DIMENSION METRIC COMPONENT DATA LIBID 1,CH/2,ETHANOL/3,WATER THERMODYNAMIC DATA METHOD SYSTEM(VLLE)=NRTL, SET=NRTL01 STREAM DATA PROP STRM=V, TEMP=45, PRES=1.033, RATE(M)=100, & COMPOSITION(M)=1,53/2,31/3,16 UNIT OPERATIONS FLASH UID=COND, NAME=Condenser, KPRINT FEED V PRODUCT L=R, W=W ISO TEMPERATURE=45, PRESSURE=1.033 END V (Mole %) R (Mole %) W (Mole %) CHX Ethanol Water Flow Rate 100 % % % Azeotropic Distillation 42

22 Step 5c: Component Mass Balance Around Azeo Column Water balance around Azeotropic Column F Azeo _ feed F W V F 2 F V R W V Azeo Column V F -(1) 2 P Azeotropic Distillation 43 Step 5c: Component Mass Balance Around Azeo Column Ethanol balance around Azeotropic Column V F2 V V 0.808F F V -(2) 2 F 2 F R W Combining Eq. (1) & (2): V K-mol/hr, F K-mol/hr Azeo Column P 에탄올에대해서는 Aqueous phase 로나간모든에탄올이 Stripper 에서회수되어 F 2 로돌아온다고가정한다. Azeotropic Distillation 44

23 Step 5c: Component Mass Balance Around Azeo Column CHX flow from the decanter V K-mol/hr F 2 R F W Azeo Column P Azeotropic Distillation 45 Step 5: Azeotropic Distillation Column Simulation V F F 2 R W Bz Controller P Azeotropic Distillation 46

24 Step 7: Simulation of an Overall Azeotropic Unit Overall Process.prz Azeotropic Distillation 47 Future Works Minimization of overall reboiler heat duties by varying the top concentration of ethanol at concentrator top for threecolumns configuration Comparison of three-columns and two-columns configuration in ethanol dehydration using several entrainers Application of an environmentally-friendly entrainer, NC5 to obtain an absolute ethanol in azeotropic distillation Experimental works for ternary LLE rather than each binary VLE s & LLE Comparison of an extractive distillation process using solvent with an azeotropic distillation process using entrainer Azeotropic Distillation 48

25 The End. Azeotropic Distillation 49

물 - 에탄올공비증류공정의최적화 공주대학교화학공학부조정호

물 - 에탄올공비증류공정의최적화 공주대학교화학공학부조정호 1 1 2 3 4 5 6 7 8 목차 :(1) 공비혼합물을형성하는이성분계의분리공비혼합물의분류올바른열역학모델식의선정원료조건, 제품사양및유틸리티삼성분계액액상평형도상에서의공비증류공정의설계농축기 (Concentrator) 의전산모사기법경사분리기 (Decanter) 의전산모사기법공비증류탑 (Azeotropic