DISTILLATION OF ETHANOL AND WATER MIXTURE

By:Zed Daliela Zulkafli

Tracy Elizabeth GrantAndrew Lossing

Advisors:PROF. BRIDGET ROGERS

PROF. JULIE SHARP

ChBE 229wFall 2009

December 10, 2009

Executive Summary

The binary distillation of ethanol and water is made possible due to the difference in volatilities of the components in the boiling liquid mixture. In this experiment, a continuous distillation unit consisting of a perforated-tray column filled with packing of IMTP #15 together with a partial reboiler and a total condenser. This column was used to find the specifications and optimum operating conditions needed to produce 100 barrels of strong, 80% mole of ethanol blend beverage from an 8% mole of ethanol mixture everyday.

In the experiment, all the feed, distillate, bottom, and reflux flow-meters were calibrated, taking into consideration that the flow meters provide accurate measurements only for water flows. The refractometer was calibrated to enable the determination of the concentration of ethanol in any given ethanol and water mixture from the refractive index. The relationship between the mole composition of ethanol, xEtOH in the mixture to the density of the mixture, ρ was found to be: ρ = 155.3*exp(-3.1752* xEtOH) + 843.4*exp(-0.05741*xEtOH). The relationship between the density of the mixture and the composition of ethanol is no longer linear once it reaches higher concentration.

Therefore, the equation: was used to

determine the initial ethanol composition of a diluted sample.

The experiment was done by varying the reflux ratio at 6.72 and 7.31, with having the feed come in the middle stage. Then we kept the reflux ratio at 6.72 and varied the feed stage which are the middle and the bottom stage. The actual number of stages of the column used in the lab is 5 stages. To find the number of theoretical stages required for the stage, the results from the distillation process was analyzed using the McCabe-Thiele method. By comparing these values, the efficiency of the column was found from the equation: Efficiency = (# Theoretical stages/# Actual stages). Once up-scaling calculation was done, we used the new theoretical number of stages to run a simulation in Aspen for the binary distillation process. Data from the experiment were used as process conditions to find the heat duty of both the reboiler and the condenser.

When the reflux ratio was set to be 6.72, the purity of ethanol was extremely high, which shows that the column has very high efficiency. However, because the value was out of the range provided in the ethanol/water equilibrium curve, it was impossible to determine the percent efficiency. This high purity gain might be due to the small amount of the distillate produced. This occurred because it was difficult to maintain the flow rate of the distillate at the specified value gained from Aspen.

The data from the experiment shows that the optimum specification for the process is to have the feed enter the column from the middle and a reflux ratio of 7.31. Even though a higher mole fraction of ethanol was obtained when the feed was at the bottom, the amount of distillate produced was lower compared to the one when it is fed in

the middle. Moreover, the mole fraction gained from the latter was sufficient with what is required. With this, the cost is saved, where we have a smaller amount of feed needed to produce the same amount of the beverage.

In conclusion, a higher reflux ratio results in a higher production rate, and the optimum stage feed is at the middle of the column. To obtain a concentration of 80% mole ethanol in the distillate, the number of stages was found to be 8 stages, based on the efficiency gained from the data (RR:7.31, feed stage: 3), which was 80%. The distillation column was calculated to be 12.8 meters, which is an appropriate measurement for a real time operating reactor.

Calibration curve for the 4 flow-meters and refractometer

Feed Calibration Curve

y = 0.0138x + 0.1248

R2 = 0.9985

0

0.5

1

1.5

2

2.5

0 20 40 60 80 100 120 140 160

Flowmeter Reading

Act

ual

Flo

w R

ate

(mL

/s)

Figure 1: Linear relationship between feed flow rate and the flow meter reading

Distillate Calibration Curve

y = 0.0052x + 0.0257

R2 = 0.9996

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 20 40 60 80 100 120 140

Flowmeter Reading

Act

ual

Flo

w R

ate

(mL

/s)

Figure 2: Linear relationship between distillate flow rate and the flow meter reading

Bottoms Calibration Curve

y = 0.0607x - 0.5528

R2 = 0.999

0

1

2

3

4

5

6

7

8

0 20 40 60 80 100 120 140

Flowmeter Reading

Act

ual

Flo

w R

ate

(mL

/s)

Figure 3: Linear relationship between bottom flow rate and the flow meter reading

Total Flow Calibration Curve

y = 0.0246x - 0.0054

R2 = 0.9994

0

0.5

1

1.5

2

2.5

3

3.5

4

0 20 40 60 80 100 120 140 160

Flowmeter Reading

Act

ual

Flo

w R

ate

(mL

/s)

Figure 4: Linear relationship between total flow rate and the flow meter reading

Refractometer Calibration Curve

y = 0.0012x + 1.3337

R2 = 0.9896

1.33

1.335

1.34

1.345

1.35

1.355

1.36

0 5 10 15 20 25mole percent of ethanol %

refr

acto

met

er r

ead

ing

(n

D)

Figure 5: Linear relationship between refractometer reading and ethanol mole percent

Density Calibration Curve

800

820840

860

880900

920

940

960980

1000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Ethanol Mole Fraction

De

ns

ity

(k

g/m

^3

)

Figure 6: Relationship between the density and the ethanol mole fraction in a binary mixture

Sensitive analysis on Reflux Ratio (RR)

Sensitive Analysis on RR

0.6

0.61

0.62

0.63

0.64

0.65

0.66

0.67

0.68

0 2 4 6 8 10 12 14 16

Reflux Ratio

Mo

le F

ract

ion

EtO

H i

n D

isti

llat

e

Figure 7: Relationship between mole fraction of ethanol in the distillate and the specified reflux ratio

Appendix

Feed Bottoms DistillateTotal Flow

Flowmeter Reading

Volume (mL)

Time (s)Actual Flow

(mL/s)

Volume (mL)

Time (s)Actual Flow

(mL/s)

Volume (mL)

Time (s)Actual Flow

(mL/s)

Volume (mL)

Time (s)Actual Flow

(mL/s)10 30 131.5 0.228 26 182.97 0.142 26 343.13 0.076 26 111.07 0.23440 30 43.94 0.683 50 27.5 1.818 26 110.45 0.235 70 74.25 0.94370 140 124.03 1.129 70 19.19 3.648 30 78.62 0.382 70 39.94 1.753

100 130 85.15 1.527 110 20.28 5.424 60 109.41 0.548 110 44.03 2.498130 90 47.09 1.911 150 20.16 7.440 50 72.13 0.693 110 34.66 3.174150 90 41.56 2.166 130 35.5 3.662

Table 1: Data for calibration curve of four flow-meters of streams entering and exiting column

Table 2: Data for calibration curve of refractormole percent

(EtOH)refractometer reading (nD)

T (oC)trial 1 trial 2 Average

5 1.3404 1.3402 1.3403 21.110 1.3477 1.3476 1.3477 21.115 1.3521 1.3514 1.3518 21.120 1.3582 1.358 1.3581 21.10 1.3327 1.3328 1.3328 21.1

Table 3: Data from Aspen for calibration curve of density of ethanol mixture

Table 4: Data from Aspen for sensitive analysis on Reflux Ratio (RR)RR Mole Fraction ETOH in Distillate0.5 0.606891541 0.63111669

1.5 0.643275812 0.65059548

2.5 0.655640873 0.65913983

3.5 0.66177694 0.66383625

4.5 0.665489265 0.66684557

5.5 0.667977736 0.66893856

6.5 0.669763627 0.67054299

7.5 0.671167158 0.67171735

8.5 0.67220689 0.67264508

ETOH mole flow [with 1 kmol/hr H2O] (kmol/hr)

DENSITY (kg/cum)

ETOH mole

fractionFIT

0 998.7672 0 998.70.25 915.78773 0.2 916.0672

0.5 881.55706 0.333333 881.30430.75 863.0296 0.428571 862.7295

1 851.47748 0.5 851.28011.25 843.61818 0.555556 843.53661.5 837.94343 0.6 837.95231.75 833.66438 0.636364 833.733

2 830.32907 0.666667 830.43082.25 827.66037 0.692308 827.77462.5 825.47918 0.714286 825.59062.75 823.66479 0.733333 823.7624

3 822.13297 0.75 822.2093.25 820.82322 0.764706 820.87253.5 819.69102 0.777778 819.713.75 818.70291 0.789474 818.6895

4 817.83327 0.8 817.78644.25 817.06217 0.809524 816.98134.5 816.37388 0.818182 816.2594.75 815.75583 0.826087 815.6074

5 815.19783 0.833333 815.0164

9.5 0.6730398510 0.67339729

10.5 0.6737224811 0.67401959

11.5 0.6742921412 0.67454304

12.5 0.6747747813 0.67498948

13.5 0.6751889614 0.67537479

14.5 0.6753675915 0.67555142

Data from distillation column until steady state was reached

Table 5.1: Distillate composition of ethanol when feed enters at stage 3 and RR is 4distillate samples EtOH mol % Xd refractometer reading (nD) Xud change

1 13.4167 0.1342 1.3498 0.7668 -2 13.5833 0.1358 1.35 0.7835 0.0173 13.2500 0.1325 1.3496 0.749 -0.0354 13.4167 0.1342 1.3498 0.7668 0.018

Table 5.2: Distillate composition of ethanol when feed enters at stage 3 and RR is 8distillate samples EtOH mol % Xd refractometer reading (nD) Xud change

1 13.9167 0.1392 1.3504 0.822 -2 13.8333 0.1383 1.3503 0.8127 -0.0093 14.3333 0.1433 1.3509 0.8715 0.0594 14.5833 0.1458 1.3512 0.9023 0.0315 14.4167 0.1442 1.351 0.8814 -0.0216 14.6667 0.1467 1.3513 0.913 0.032

Table 5.1: Distillate composition of ethanol when feed at stage 5 and RR is 8distillate samples EtOH mol % Xd refractometer reading (nD) Xud change

1 14.5833 0.1458 1.3512 0.9023 -2 14.4167 0.1442 1.351 0.8814 -0.0213 14.4167 0.1442 1.351 0.8814 0.0004 14.7500 0.1475 1.3514 0.9235 0.0425 14.7500 0.1475 1.3514 0.9235 0.000

Analysis

Design a process to concentrate a mash (8 mole% ethanol in water) to a very strong, but tasty, 80 mole% blend. Need to be able to produce 100 barrels a day.

    Design 1     Design 2     Design 3  Properties Feed Distillate Bottom Feed Distillate Bottom Feed Distillate Bottom

volumetric flow rate (L/day) 1.49E+05 1.19E+04 1.36E+05 1.36E+05 1.19E+04 1.22E+05 1.36E+05 1.19E+04 1.22E+05mass flow rate (g/day) 1.43E+08 9.75E+06 1.33E+08 1.30E+08 9.75E+06 1.20E+08 1.30E+08 9.75E+06 1.21E+08ethanol mass flow rate (g EtOH/day) 2.61E+07 8.88E+06 1.72E+07 2.37E+07 8.88E+06 1.48E+07 2.37E+07 8.88E+06 1.48E+07water mass flow rate (g H2O/day) 1.17E+08 8.68E+05 1.16E+08 1.06E+08 8.68E+05 1.06E+08 1.07E+08 8.68E+05 1.06E+08ethanol mass fraction (g EtOH/g soln) 0.1820 0.9110 0.1287 0.1820 0.9110 0.1230 0.1820 0.9110 0.1230water mass fraction (g H2O/g soln) 0.8180 0.0890 0.8713 0.8180 0.0890 0.8770 0.8180 0.0890 0.8770ethanol mole fraction (mol EtOH/mol soln) 0.0800 0.8000 0.0274 0.0800 0.8000 0.0217 0.0800 0.8000 0.0218water mole fraction (mol H2O/mol soln) 0.9200 0.2000 0.9726 0.9200 0.2000 0.9783 0.9200 0.2000 0.9782

From Aspen:

Column Performance

Performance Condenser ReboilerTemperature © 77.874 88.778

Heat Duty (kJ/day) -7.43E+07 8.60E+07Distillate rate

(kmol/day) 242.56182 -Reflux rate (kmol/day) 1630.0155 -

Reflux ratio 7.31 -Bottom rate (kmol/day) - 6455.64967Boilup rate (kmol/day) - 2071.01713

Boilup ratio - 0.32

Stream Properties

Temperature K 339.650 351.024 361.928Pressure atm 1.000 0.987 0.987Vapor Frac 0 0 0

Mole Flow kmol/hr 279.092 10.107 268.985Mass Flow kg/hr 5654.290 406.304 5247.986Mass Flow g/day 135702957 9751294 125951663

Volume Flow l/min 103.577 9.022 97.310Volume Flow l/day 149152 12991 140126

Enthalpy MMkcal/hr -18.783 -0.659 -18.009

Mole Flow kmol/hr ETHANOL 22.327 7.993 14.335

WATER 256.765 2.114 254.651Mole Frac

ETHANOL 0.08 0.791 0.053 WATER 0.92 0.209 0.947

Design specifications

Efficiency 80%Theoretical number of

stages 6Actual number of stages 8

Optimal Feed Stage middleColumn Diameter (m)  1.28

6) Calculation for diameter: use scale up value from experimental data

Diameter of column: 10.15 cmHeight of column: 110 cmScale up ratio (in volume): 2009.64 Ratio of Height to Diameter of column: 10.84

Use the equation of a cylinder:

V=Πr2h (I)

Where,

V = volume of columnr = radius of columnh = height of column

Volume of column: Π(5.075)2(110) = 8900.5 cm3 = 8.9 LVolumn of actual reactor column: 8.9(2009.64) = 17886.81 L

From equation of cylinder and diameter to height ratio, equation II was obtained:

(II)

Therefore the actual diameter is: = = = 128.1 cm = 1.28 m

References

1) http://lorien.ncl.ac.uk/ming/distil/distilpri.htm2) Seader, J.D, 2006, Separation Process Principles, 2nd edition, John Wiley & Sons,

Hoboken, pp 316-318.3) Koch-Glitsch, 2003, “Intalox Packed Tower Systems, IMTP High Performance

Packing,” Koch-Glitsch, LP, pp.

http://lorien.ncl.ac.uk/ming/distil/distilpri.htm