Lab Report Distillation

DISTILLATION OF ETHANOL AND WATER MIXTURE By:

Zed Daliela Zulkafli Tracy Elizabeth Grant Andrew Lossing Advisors: PROF. BRIDGET ROGERS PROF. JULIE SHARP

ChBE 229w Fall 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. V H O (22 Xs + 18 ) ρ H O + * )] was used to Therefore, the equation: Xs = X diluted [1 + ( Vs 18 ρs determine the initial ethanol composition of a diluted sample. 2

2

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

Actual Flow Rate (mL/s)

2.5 2 1.5 y = 0.0138x + 0.1248 R2 = 0.9985

1 0.5 0 0

20

40

60

80

100

120

140

160

Flowmeter Reading

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

Distillate Calibration Curve

Actual Flow Rate (mL/s)

0.8 0.7 0.6 0.5 0.4 y = 0.0052x + 0.0257 R2 = 0.9996

0.3 0.2 0.1 0 0

20

40

60

80

100

120

Flowmeter Reading

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

140

Bottoms Calibration Curve

Actual Flow Rate (mL/s)

8 7 6 5 4

y = 0.0607x - 0.5528 R2 = 0.999

3 2 1 0 0

20

40

60

80

100

120

140

Flowmeter Reading

Figure 3: Linear relationship between bottom flow rate and the flow meter reading Total Flow Calibration Curve

Actual Flow Rate (mL/s)

4 3.5 3 2.5 y = 0.0246x - 0.0054 R2 = 0.9994

2 1.5 1 0.5 0 0

20

40

60

80

100

120

140

Flowmeter Reading

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

160

Refractometer Calibration Curve

refractometer reading (nD)

1.36 1.355 1.35

y = 0.0012x + 1.3337 R2 = 0.9896

1.345 1.34 1.335 1.33 0

5

10

15

20

mole percent of ethanol %

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

25

Density (kg/m^3)

Density Calibration Curve 1000 980 960 940 920 900 880 860 840 820 800 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Ethanol Mole Fraction

Figure 6: Relationship between the density and the ethanol mole fraction in a binary mixture Sensitive analysis on Reflux Ratio (RR)

Mole Fraction EtOH in Distillate

Sensitive Analysis on RR

0.68 0.67 0.66 0.65 0.64 0.63 0.62 0.61 0.6 0

2

4

6

8

10

12

14

Reflux Ratio

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

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

Volume (mL)

Time (s)

10 40 70 100 130 150

30 30 140 130 90 90

131.5 43.94 124.03 85.15 47.09 41.56

Bottoms Actual Flow (mL/s) 0.228 0.683 1.129 1.527 1.911 2.166

Volume (mL)

Time (s)

26 50 70 110 150

182.97 27.5 19.19 20.28 20.16

Total Flow

Distillate Actual Flow (mL/s) 0.142 1.818 3.648 5.424 7.440

Volume (mL)

Time (s)

26 26 30 60 50

343.13 110.45 78.62 109.41 72.13

Actual Flow (mL/s) 0.076 0.235 0.382 0.548 0.693

Table 2: Data for calibration curve of refractor mole percent (EtOH) 5 10 15 20 0

refractometer reading (nD) trial 1 trial 2 Average 1.3404 1.3402 1.3403 1.3477 1.3476 1.3477 1.3521 1.3514 1.3518 1.3582 1.358 1.3581 1.3327 1.3328 1.3328

T (oC) 21.1 21.1 21.1 21.1 21.1

Volume (mL)

Time (s)

26 70 70 110 110 130

111.07 74.25 39.94 44.03 34.66 35.5

Actual Flow (mL/s) 0.234 0.943 1.753 2.498 3.174 3.662

Table 3: Data from Aspen for calibration curve of density of ethanol mixture ETOH mole flow [with 1 kmol/hr H2O] (kmol/hr)

DENSITY (kg/cum)

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5

998.7672 915.78773 881.55706 863.0296 851.47748 843.61818 837.94343 833.66438 830.32907 827.66037 825.47918 823.66479 822.13297 820.82322 819.69102 818.70291 817.83327 817.06217 816.37388 815.75583 815.19783

ETOH mole fraction 0 0.2 0.333333 0.428571 0.5 0.555556 0.6 0.636364 0.666667 0.692308 0.714286 0.733333 0.75 0.764706 0.777778 0.789474 0.8 0.809524 0.818182 0.826087 0.833333

FIT 998.7 916.0672 881.3043 862.7295 851.2801 843.5366 837.9523 833.733 830.4308 827.7746 825.5906 823.7624 822.209 820.8725 819.71 818.6895 817.7864 816.9813 816.259 815.6074 815.0164

Table 4: Data from Aspen for sensitive analysis on Reflux Ratio (RR) RR 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9

Mole Fraction ETOH in Distillate 0.60689154 0.63111669 0.64327581 0.65059548 0.65564087 0.65913983 0.6617769 0.66383625 0.66548926 0.66684557 0.66797773 0.66893856 0.66976362 0.67054299 0.67116715 0.67171735 0.6722068 0.67264508

9.5 10 10.5 11 11.5 12 12.5 13 13.5 14 14.5 15

0.67303985 0.67339729 0.67372248 0.67401959 0.67429214 0.67454304 0.67477478 0.67498948 0.67518896 0.67537479 0.67536759 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 4 distillate samples 1 2 3 4

EtOH mol % 13.4167 13.5833 13.2500 13.4167

Xd 0.1342 0.1358 0.1325 0.1342

refractometer reading (nD) 1.3498 1.35 1.3496 1.3498

Xud 0.7668 0.7835 0.749 0.7668

change 0.017 -0.035 0.018

Table 5.2: Distillate composition of ethanol when feed enters at stage 3 and RR is 8 distillate samples 1 2 3 4 5 6

EtOH mol % 13.9167 13.8333 14.3333 14.5833 14.4167 14.6667

Xd 0.1392 0.1383 0.1433 0.1458 0.1442 0.1467

refractometer reading (nD) 1.3504 1.3503 1.3509 1.3512 1.351 1.3513

Xud 0.822 0.8127 0.8715 0.9023 0.8814 0.913

change -0.009 0.059 0.031 -0.021 0.032

Table 5.1: Distillate composition of ethanol when feed at stage 5 and RR is 8 distillate samples 1 2 3 4 5

EtOH mol % 14.5833 14.4167 14.4167 14.7500 14.7500

Xd 0.1458 0.1442 0.1442 0.1475 0.1475

refractometer reading (nD) 1.3512 1.351 1.351 1.3514 1.3514

Xud 0.9023 0.8814 0.8814 0.9235 0.9235

change -0.021 0.000 0.042 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. Properties volumetric flow rate (L/day) mass flow rate (g/day) ethanol mass flow rate (g EtOH/day) water mass flow rate (g H2O/day) ethanol mass fraction (g EtOH/g soln) water mass fraction (g H2O/g soln) ethanol mole fraction (mol EtOH/mol soln) water mole fraction (mol H2O/mol soln)

Feed 1.49E+05 1.43E+08

Design 1 Distillate 1.19E+04 9.75E+06

Bottom 1.36E+05 1.33E+08

Feed 1.36E+05 1.30E+08

Design 2 Distillate 1.19E+04 9.75E+06

Bottom 1.22E+05 1.20E+08

Feed 1.36E+05 1.30E+08

Design 3 Distillate 1.19E+04 9.75E+06

Bottom 1.22E+05 1.21E+08

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+07

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+08

0.1820

0.9110

0.1287

0.1820

0.9110

0.1230

0.1820

0.9110

0.1230

0.8180

0.0890

0.8713

0.8180

0.0890

0.8770

0.8180

0.0890

0.8770

0.0800

0.8000

0.0274

0.0800

0.8000

0.0217

0.0800

0.8000

0.0218

0.9200

0.2000

0.9726

0.9200

0.2000

0.9783

0.9200

0.2000

0.9782

From Aspen: Column Performance Performance Temperature © Heat Duty (kJ/day) Distillate rate (kmol/day) Reflux rate (kmol/day) Reflux ratio Bottom rate (kmol/day) Boilup rate (kmol/day) Boilup ratio

Condenser 77.874 -7.43E+07

Reboiler 88.778 8.60E+07

242.56182 1630.0155 7.31 -

6455.64967 2071.01713 0.32

Stream Properties Temperature K Pressure atm Vapor Frac Mole Flow kmol/hr Mass Flow kg/hr Mass Flow g/day Volume Flow l/min Volume Flow l/day Enthalpy MMkcal/hr Mole Flow kmol/hr ETHANOL WATER Mole Frac ETHANOL WATER

339.650 1.000 0 279.092 5654.290 135702957 103.577 149152

351.024 0.987 0 10.107 406.304 9751294 9.022 12991

361.928 0.987 0 268.985 5247.986 125951663 97.310 140126

-18.783

-0.659

-18.009

22.327 256.765

7.993 2.114

14.335 254.651

0.08 0.92

0.791 0.209

0.053 0.947

Design specifications Efficiency Theoretical number of stages Actual number of stages Optimal Feed Stage Column Diameter (m)

80% 6 8 middle 1.28

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

Diameter of column: 10.15 cm Height of column: 110 cm Scale 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 column r = radius of column h = height of column Volume of column: Π(5.075)2(110) = 8900.5 cm3 = 8.9 L Volumn of actual reactor column: 8.9(2009.64) = 17886.81 L From equation of cylinder and diameter to height ratio, equation II was obtained: V = π ⋅10 .837 D ⋅

Therefore the actual diameter is: =

3

D2 4

4V = 10 .837 π

3

(II) 4(17886810 ) = 128.1 cm = 1.28 m 10 .837 π

References 1) http://lorien.ncl.ac.uk/ming/distil/distilpri.htm 2) 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.