Episode 57 : Simulation for Design and Analysis
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This document outlines the steps to design a separation process for a mixture of methyl acetate, methanol, acetic acid, and water. The steps include: 1) Analyzing the mixture components and their properties 2) Creating a binary ratio matrix to identify feasible separation techniques 3) Selecting distillation as the first separation based on ease of separation 4) Generating a process flowsheet using distillation columns 5) Verifying the flowsheet design using process simulation software.
Episode 57 : Simulation for Design and Analysis
- 1. SAJJAD KHUDHUR ABBAS Ceo , Founder & Head of SHacademy Chemical Engineering , Al-Muthanna University, Iraq Oil & Gas Safety and Health Professional – OSHACADEMY Trainer of Trainers (TOT) - Canadian Center of Human Development Episode 57 : Simulation for Design and Analysis
- 2. Problem Description Methyl-acetate is produced by esterification of methanol and acetic acid which produces water as by-product. CH3OH + CH3COOH CH3COOCH3 + H2O The mixture to be separated is an outlet stream from a reactor (assumed conditions: P=1 atm, T=450 K) and the methyl-acetate product specification is 99 %. Problem statement: Given the identity and composition of the components in the mixture to be separated, together with the product specifications, identify a physically feasible flowsheet for separation of the mixture into the specified products. Determine the estimates of operating conditions and identify a MSA where required. Verify the generated process flowsheet with process simulation, together with the alternative separation techniques for its separation task.
- 3. Tasks to perform ? 1. Analyze mixture 2. Compute binary ratio matrix 3. Identify separation techniques 4. Screen alternatives 5. Compute separation factor 6. Select the first separation task 7. Generate process flowsheet 8. Analyze decisions 9. Verify flowsheet
- 4. Tasks to perform ? 1. Analyze mixture Nature of mixture State of components at a reference condition Number of binary pairs Analysis of azeotropes Liquid miscibility, solubility & solvents
- 5. Tasks to perform ? 1. Analyze mixture State of components at reference conditions (T = 298 K, P = 1 atm): All components are liquids at reference conditions, since their boiling points are: MeAc (330.1 K), MeOH (337.7 K), H2O (373.2 K), HOAc (391.0 K). Number of binary pairs: There are 6 binary pairs (MeAc/MeOH, MeAc/H2O, MeAc/HOAc, MeOH/H2O, MeOH/HOAc, and HOAc/H2O). Identification of azeotropes with pressure dependence: The following pairs form azeotropes at P = 1 atm, based on vle data (see table below). Table I: Azeotropes at P = 1 atm for methyl-acetate example Binary pair Azeotrope T (K) , x (mole %) MeAc/H2O 330.1 K , 92.8 % MeAc MeAc/MeOH 328.1 K , 67.4 % MeAc H2O/HOAc 371.8 K , 15.7 % HOAc
- 6. Tasks to perform ? 1. Analyze mixture Table II: Mutual solubilities for methyl-acetate example Table III: Solubility parameters in methyl-acetate example Binary pair Mutual solubilities (gr/cm3 ) Binary pair Mutual solubilities (gr/cm3 ) MeAc in MeOH 0.652 MeOH in MeAc 0.131 MeAc in HOAc 1.146 HOAc in MeAc 0.385 MeAc in H2O 0.162 H2O in MeAc 0.027 MeOH in HOAc 0.342 HOAc in MeOH 1.947 MeOH in H2O 0.988 H2O in MeOH 0.280 HOAc in H2O 0.917 H2O in HOAc 0.124 Component Solubility parameter (Mpa1/2 ) (ProPred) Solubility parameter (Mpa1/2 ) (databank) MeAc 19.35 19.35 MeOH 27.46 29.6 HOAc 29.73 19 H2O 47.8 47.8
- 7. Tasks to perform ? 1. Analyze mixture Table IV: Multi-phase flash calculation for MeAc/MeOH/CO2 system Table V: Multi-phase flash calculation for MeAc/H2O/CO2 system Feed stream (kmol/hr) (molefractions) T = 420 K , P = 75 atm Phase 1 (molefractions) Phase 2 ( molefractions ) MeAc 67.4 0.337 0.176 0.484 MeOH 32.6 0.163 0.098 0.222 CO2 100 0.500 0.726 0.294 Fraction of feed 0.476 0.524 Feed stream (kmol/hr) (molefractions) T = 420 K , P = 75 atm Phase 1 (molefractions) Phase 2 ( molefractions ) MeAc 92.8 0.464 0.232 0.639 H2O 7.2 0.036 0.024 0.045 CO2 100 0.500 0.744 0.316 Fraction of feed 0.430 0.570
- 8. Tasks to perform ? 2. Binary ratio matrix : rk = pk / pk ij i j where i and j are component indices and, pk i > pk j
- 9. Tasks to perform ? 2. Binary ratio matrix : rk = pk / pk ij i j where i and j are component indices and, pk i > pk j Table VIII: Computed binary ratio matrix for methyl-acetate example Ratio of properties for binary pairs Property MeOH/ HOAc MeOH/ MeAc MeOH/ H2O HOAc/ MeAc HOAc/ H2O MeAc/ H2O Molecular weight 1.87 2.31 1.78 1.23 3.33 4.11 Critical temperature 1.15 1.01 1.26 1.17 1.09 1.28 Boiling point 1.16 1.02 1.10 1.18 1.05 1.13 Dipolemoment 1.02 1.01 1.09 1.04 1.06 1.10 Radius of gyration 1.68 1.93 2.52 1.15 4.24 4.87 Melting point 1.65 1.00 1.56 1.66 1.06 1.56 Triple point temperature 1.65 1.00 1.56 1.66 1.06 1.56 Triple point pressure 11455.3 9.12 5487.96 1255.5 2.09 601.5 Molar volume 1.42 1.97 2.25 1.39 3.19 4.42 Solubility parameter 1.56 1.53 1.62 1.02 2.52 2.47 Van der Waals volume 1.53 1.96 1.76 1.28 2.69 3.44 Vapour pressure 8.11 1.70 5.32 13.78 1.52 9.04 Binary azeotrope at P = 1 atm No Yes No No Yes Yes
- 10. Tasks to perform ? 3. Identify separation techniques 4. Screen alternatives Compare values of binary ratio matrix against a similar matrix where the columns are separation techniques. If the binary ratio value is within the specified range for the same property in the separation matrix, the select the corresponding binary pair as the separation task and the separation technique as an alternative unit operation
- 11. 3. Identify separation techniques & 4. Screen alternatives Table IX: Identified feasible separation techniques for methyl-acetate example Task Separation technique MeOH/HOAc Distillation, liquid membranes, stripping, pervaporation, adsorption, absorption, crystallisation, cryogenic distillation, desublimation, gas separation membranes, sublimation, ultrafiltration MeOH/MeAc Liquid membranes, pervaporation, adsorption, distillation, extractive distillation, absorption, stripping, azeotropic distillation, supercritical extraction (with CO2), pressure swing distillation, pressure distillation, liquid liquid extraction, microfiltration, ultrafiltration MeOH/H2O Distillation, liquid membranes, pervaporation, adsorption, stripping, absorption, crystallisation, extractive distillation, cryogenic distillation, desublimation, gas separation membranes, sublimation, ultrafiltration HOAc/MeAc Distillation, crystallisation, liquid membranes, pervaporation, adsorption, stripping, cryogenic distillation, desublimation, gas separation membranes, sublimation HOAc/H2O Liquid membranes, pervaporation, adsorption, absorption, distillation, extractive distillation, stripping, azeotropic distillation, supercritical extraction, pressure swing distillation, liquid liquid extraction, microfiltration, ultrafiltration MeAc/H2O Distillation, liquid membranes, pervaporation, adsorption, absorption, crystallisation, stripping, liquid-liquid extraction, distillation+decanter, pressure swing distillation, pressure distillation/P=0.3 atm, cryogenic distillation, desublimation, gas separation membranes, microfiltration, sublimation, ultrafiltration
- 12. Tasks to perform ? 1. Analyze mixture 2. Compute binary ratio matrix 3. Identify separation techniques 4. Screen alternatives 5. Compute separation factor 6. Select the first separation task 7. Generate process flowsheet 8. Analyze decisions 9. Verify flowsheet split factors easiest separation first ? repeat steps 6, 7 & 8
- 13. Tasks to perform ? 1. Analyze mixture 2. Compute binary ratio matrix 3. Identify separation techniques 4. Screen alternatives 5. Compute separation factor 6. Select the first separation task 7. Generate process flowsheet 8. Analyze decisions 9. Verify flowsheet distillation find solvents determine design parameters
- 14. Tasks to perform ? 9. Verify flowsheet Description of a sample feasible flowsheet T1 Reactor FEED-T1 FEED Molecular Sieve TOP-T1 H20-Purge Mixer TOP_NO_H2O T2 T3 FEED-T2 TOP-T2 FEED-T3 Valve TOP-T3 RECYCLE-T3 BOT-T3 MeAc 99.9% BOT-T2 MeOH 98% T4 T5 BOT-T5 HOAc 99.9% BOT-T4 HOAc 99.9% BOT-T1 TOP-T4 TOP-T5 P=6atm P=1atm P=6atm P=1atm P=1atm
- 15. Tasks to perform ? 9. Verify flowsheet Verification (by simulation) of the flowsheet
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