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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