Using Process Simulators in Chemical Engineering
Lectures: Case Study, Ethyl Lactate Production
Tania Vitery Daniel Jaimes
Camilo Monroy
2013 AIChE Annual Meeting
Ethyl Lactate Overview Ethyl lactate (green solvent) is an organic ester, biodegradable. Some properties: High solvency, High boiling point, Low vapor pressure and Low surface tension. Figure 1. Molecular structure of ethyl lactate. [9]
Ethyl Lactate Overview Raw materials -Aqueous lactic acid solution (88 wt %) -Ethanol 96 wt% -Amberlyst 15 cation-exchange resin as a catalyst.
Lactic acid Weight fraction L1 0.58 L2 0.22 L3 0.06
H2O 0.14
Table 1. Acid lactic composition. [9]
Ethyl lactate Overview The monomer (L1) esterification, oligomer (L2, L3) formation and esterification, are completely described by the following set of reactions:
L1+ EtOH ⇌ L1E+H2O L2+ EtOH ⇌ L2E+H2O L3+ EtOH ⇌ L3E+H2O
L2+ H2O ⇌ 2L1 L3+ H2O ⇌ L1+ L2
Reactors
Figure 2. Reactors configuration, Aspen Plus
Adiabtic R infinite Countercurrent Isothermic
Ethanol 0,396 0,396 0,389 0,380
Water 0,386 0,392 0,382 0,389
Lactic acid 0,058 0,046 0,074 0,067
Ethyl lactate 0,143 0,143 0,150 0,159
Dilactic acid 0,014 0,020 3,78E-03 2,45E-03
Tablle 2. Molar composition of the reaction mixture in the reactors outgoing. Aspen Plus
Figure 3. Sensitivity analysis in the parallel reactor.
Sensitivity analysis
Figure 4. Results of the sensitivity analysis in parallel reactor, HYSYS
DISTILLATION TRAIN ASPEN
Figure 5. Process configuration, ASPEN
DISTILLATION TRAIN HYSYS
Figure 6. Process configuration, HYSYS
Reactive Column results ETANOL REC ACID BOTTOM DIST
Mass Fractions ETHANOL 0.94 0.00 0.00 0.69
WATER 0.06 0.14 0.00 0.28 L1 0.00 0.58 0.21 0.01 L3 0.00 0.06 0.00 0.00 L1E 0.00 0.00 0.77 0.01 L2 0.00 0.22 0.01 0.00 L2E 0.00 0.00 0.01 0.00
Temperature K 362.31 351.15 461.35 394.86 Pressure atm 2 2 2 2
Table 3. Reactive Column results.
Reactive Column results
Stage
Tem
pera
ture
C
1.0 3.0 5.0 7.0 9.0 11.0 13.0 15.0 17.0 19.0 21.0 23.0 25.0
120.
014
0.0
160.
018
0.0
200
Stage
Y (
mas
s fra
c)
1.0 6.0 11.0 16.0 21.0 26.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
ET HANOLWAT ERL1EL1L3L2L2E
Reboiler/Bottom stage
Temperature (⁰C) 188.2
Heat duty (kJ/h) 5954509.93
Bottoms rate 3580.12
Boilup rate 14908.83
Boilup ratio 4.16
Table 4. Reactive Column results, reboiler. ASPEN.
Figure 7. Reactive Column results, ASPEN A) Temperature profile, B) Composition profile.
Ethyl lactate Recovery column results BOTTOM L1E OLIG LIQUID LIQUID LIQUID
Mass Flow kg/hr ETHANOL 2.35 2.35 0.00
WATER 0.72 0.72 0.00 L1 736.04 32.74 703.30 L3 1.75 0.00 1.75 L1E 2752.17 2731.01 21.16 L2 40.87 1.69 39.18 L2E 46.22 1.36 44.86
BOTTOM L1E OLIG Mass Frac
ETHANOL 6.57E-04 8.49E-04 6.41E-14 WATER 2.00E-04 2.59E-04 3.06E-14
L1 0.21 0.01 0.87 L3 4.88E-04 1.86E-35 2.15E-03 L1E 0.77 0.99 0.03 L2 0.01 0.00 0.05 L2E 0.01 0.00 0.06
Pressure Vaccum Vaccum Vaccum
Table 5. Recovery Column results.
Ethyl lactate Recovery column results p p
Stage
Tem
pera
ture
C
1.0 3.0 5.0 7.0 9.0 11.0 13.0 15.0 17.0 19.0 21.0 23.0 25.0
180.
020
0.0
220.
024
0
p p
Stage
Y (
mas
s fra
c)
1.0 6.0 11.0 16.0 21.0 26.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
ET HANOLWAT ERL1L3L1EL2L2E
Figure 8. Recovery Column results, ASPEN A) Temperature profile, B) Composition profile.
Ethanol Recovery column results ETOH-H2O ETOH WATER
MIXED LIQUID LIQUID Mass Flow kg/hr
ETHANOL 2456.36 2105.70 350.66 WATER 1005.83 131.38 874.45
L1 28.55 0.00 28.55 L3 0.00 0.00 0.00 L1E 28.25 0.00 28.25 L2 15.72 0.00 15.72 L2E 0.01 0.00 0.01
ETOH-H2O ETOH WATER Mass Frac
ETHANOL 0.69 0.94 0.27 WATER 0.28 0.06 0.67
L1 0.01 0.00 0.02 L3 0.00 0.00 0.00 L1E 0.01 0.00 0.02 L2 0.00 0.00 0.01 L2E 0.00 0.00 0.00
Temperature K 373.15 369.74 377.79 Pressure Vaccum Vaccum Vaccum
Table 6. Ethanol Recovery column results.
Ethanol Recovery column results
Stage
Tem
pera
ture
C
1.0 3.0 5.0 7.0 9.0 11.0 13.0 15.0 17.0 19.0 21.0
98.0
100.
010
2.0
104.
010
6
p p
Stage
Y (
mas
s fra
c)
1.0 3.0 5.0 7.0 9.0 11.0 13.0 15.0 17.0 19.0 21.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
ET HANOLWAT ER
Reboiler/Bottom stage
Temperature (⁰C) 104.64
Heat Duty (kJ/h) 20013471
Bottoms rate (kg/h) 1297.64
Boilup rate (kg/h) 15681.42
Boilup ratio 12.08
Condenser/Top stage
Temperature (⁰C) 96.59
Distillate rate (kg/h) 2237.08
Reflux rate (kg/h) 22370.78
Reflux ratio 10.00
Table 7. Ethanol Recovery column results, A) Condenser, B) Reboiler
Figure 9. Ethanol Recovery column results, ASPEN A) Temperature profile, B) Composition profile
PARAMETER ESTIMATION Property Name Estimated
value Data base
value %Error
TEMPERATURE (°C) 398,6 314,9 27
PRESSURE (atm) 47,89 38,1 26
VOLUME (m3/kgmol) 0,2993 0,354 15
ACENTRICITY 0,2508 0,793 68
DIPOLE MOMENT (DEBYE) 0 2,4 100
RADIUS OF GYRATION (ANGSTROM) 3,82 3,62 6
COSTALD (SRK) Acentricity 0,25 0,79 68
COSTALD VOLUME (m3/kgmol) 0,35 0,39 10
VISCOSITY COEFF A 0,24 -0,67 64
VISCOSITY COEFF B 0,14 -1,61 91
CAVETT HEAT OF VAP COEFF A 0,27 0,23 17
CAVETT HEAT OF VAP COEFF B 0 - -
HEAT OF FORM (25°C) (kcal/kgmol) -5,16E+04 -1,52E+05 66
HEAT OF COMB (25°C) (kcal/kgmol) - -5,93E+05 -
RACKETT PARAMETER ZRA 0,29 0,27 7
Table 8. Results of the ethyl lactate properties estimation .
THERMODYNAMIC PACKAGE VALIDATION
Figure 10. Thermodynamic data vapor-liquid equilibrium. UNIQUAC model regression of experimental data.
i Ethanol j Ethyl Lactate
Aij -9,45 Aji 17,16 Bij 1494,79 Bji -994,56 Cij 0,82 Cji -2,39
T inferior -273 °C T superior 726,85 °C
Tabla 9. Outcome parameters.
Reactive column sizing Section starting stage 1
Section ending stage 23
Column diameter (m) 1.23
Maximum fractional capacity 0.59
Maximum capacity factor (m/s) 0.049
Section pressure drop (atm) 0.0017
Average pressure drop / Height (mm-water/m) 3.55
Maximum stage liquid holdup (l) 12.93
Max liquid superficial velocity (m/s) 0.0053
Surface area (sqcm/cc) 3.45
Void fraction 0.99
Table 10. Results of reactive column sizing. ASPEN
Reactive column sizing
Figure 11. Profiles packed height (m) in reactive column vs. A) Liquid Holdup (L), B) Pressure Drop (atm) and C) Pressure drop / height (mbar / m). Aspen.
HEAT EXCHANGER SIZING
Figure 12. Initial data used in “Aspen Exchanger Design & Rating”
Tipo Costo $USD Área m^2 Caída de presión
Tubos Coraza
AHL 21838 15,4 0,13 0,30
AEL 19343 14 0,19 0,33
AFL 23228 15,7 0,14 0,28
AGL 20561 14,6 0,16 0,33
AJL 20270 14,6 0,11 0,33
Table 11. Exchanger sizing results.
Figure 12. Cross section and sectional side view of the heat exchanger obtained.
The shell fluid is split in two streams, each one with two steps in the heat exchanger.
ENERGY INTEGRATION Design 10
Total area (m2) 5,113
Equipment's number 14
Equipment cost $706
Heating Cost ($/h) $0.018
Cooling Cost ($/h) $0.054
Total Cost ($/h) $0.72
Table 11. Energy integration results.
Figure 13. Network energy exchange.
Conclusions The development of this type of case
studies, allow us to know about the computing and technology tools present in Chemical Engineering simulators, like Aspen and Hysys.
For the use of this tools, it is necessary to have knowledge of every operation involved in the process.
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