exp 1 packed column distillation (1)

Mass Transfer I CLB 20804

Experiment 1

PACKED COLUMN DISTILLATION PROCESS

1.0 OBJECTIVES

To operate vapor – liquid separation process using a Packed Column Distillation

Unit.

To analyze the effect of reflux ratio on separation of ethanol-water system.

To determine the number of stages by using McCabe Thiele method

2.0 OVERVIEW

Distillation is one of the important unit operations in many chemical industries and has

been used from the inception of chemical and process industry. Distillation is used for the

separation of components in a liquid mixture of volatile constituents. The Distillation Column is

usually a vertical column where the liquid and vapor phases of the mixture are made to mix and

approach equilibrium.

The two types of distillations utilized in industry are batch and continuous. Batch

distillation is desirable when small quantities of high valued chemicals need to be separated. In a

batch system, the column can handle different mixtures by simply changing its operating

conditions. In this lab, the packing in the column is rachig rig glass. The distillation column also

contains a condenser, which cools and condenses the vapor leaving the top of the column. A

reboiler is connected to the bottom of the distillation apparatus and it provides the reboil heat that

is necessary for distillation.

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Figure 2 shows the schematic diagram of the apparatus in this experiment.

Figure 2: Packed distillation column

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3.0 EXPERIMENTAL PROCEDURES

3.1 Chemicals and Ancillary Equipments Required:

PART A: Calibration curve of ethanol-water mixtures

Chemicals required: Ethanol industrial grade. Deionized-Water.

Ancillary equipments required: Test Tube( 20 test tube per group) Beakers (50 ml). Dropper Glass rod Refractometer

PART A: Calibration curve of Ethanol-Water mixtures

1. Obtain 21 test tubes; label the test tubes with A1 until A21. Total volume in each test

tube is 20 ml.

2. Prepare the mixture of ethanol and deionized water to each test tube according to

volume indicate by Table 1.

3. Note that, Stir the mixture of solution (A1 until A21) with glass rod.

4. Obtain the refractive index reading for solution in each tube using refractometer.

5. Record the refractive index reading for each tube tests using Table 1.

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Table 1: The volume of chemical needed in each test tube

Test tube Volume of Ethanol(ml)

Volume of Deionized-Water(ml)

Refractive Index(RI)

A1 0 20

A2 1 19

A3 2 18

A4 3 17

A5 4 16

A6 5 15

A7 6 14

A8 7 13

A9 8 12

A10 9 11

A11 10 10

A12 11 9

A13 12 8

A14 13 7

A15 14 6

A16 15 5

A17 16 4

A18 17 3

A19 18 2

A20 19 1

A21 20 0

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PART B: Operate vapor -liquid separation process using a Packed Column Distillation Unit under reflux ratio.

Chemicals required: Ethanol industrial grade. Deionized-Water.

Ancillary equipments required: Dropper Beakers (50 ml) Tissue Refractometer

3.2 General start-up procedures.

1. Prepare 30 litres mixture of ethanol-deionized water by adding 10 % of ethanol

from total volume of the mixture.

2. Ensure valves V3, V4 and V5 are closed.

3. Ensure valves V2, V8 and V10 are open.

4. Ensure that the Bottom Product sampling valve V5 and Top Product sampling valve

V4 are closed.

5. Slowly turn on the Cooling Water (CW) supply to the Condenser. Make sure water is

indeed flowing through it by makesure water flows to the drain from the Cooling

Water outlets. Do not start the experiment until the Cooling Water flow is visible in

the outlets to the drain.

6. Set water flowrate of Cooling Water (CW) to 6 L/min by adjusting water flow

control FCV2.

7. Open valve V6, fill the reboiler vessel(B1) with the 30 L Ethanol-Water mixtures.

8. Close the valve V6 and open valve V2 after finish fill reboiler vessel with the 30 L

Ethanol-Water mixtures.

9. Check that the liquid level in Reboiler vessel is satisfactory (Refer to instructor /

technician).Otherwise top up with the Ethanol – Water mixture through the Charge

Port (Refer to instructor / technician).

10 Turn on the main power control switch.

11 Turn on the power switch of the heater.

12 Switch on electrical supply (green ‘heater on ‘button).

13 Set heater controller HC4 to maximum setting (about 230V@ 30A).

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14 Allow a period of 15 minutes for the equipment to maintain thermal equilibrium with

surroundings.

15 The unit is now ready to be used for an experiment.

Experiment: Operation under reflux ratio condition

1. When mixture is start to boil, close valves V2.

2. When distillate liquid is seen to flow through R1.1C, adjust both valve for Reflux

Ratio RCV1 so that both readings on R1 and R2 provide a reflux ratio of 1.0 for the

operation.

3. Ensure that the Reflux Ratio is maintained at 1.0.

4. Collect samples for bottom product from valve V5 and the overhead product from

valve V4 for every 5 minutes.

5. Observe the temperature of the reboiler T14.If the temperature is already 90OC,

reduce the current of the reboiler to between 20A.

6. Concentration of the samples drawn is measure using the refractive index method

7. Record all data obtained in appendix A.

8. Repeat the experiment (steps 2 to 6),for reflux ratio of 1.5 and 2.0

3.3 General shut – down procedures.

1. Adjust heater controller HC.4 to minimum setting.

2. Switch off electrical supply (red ‘heater off’ button).

3. Turn off the power switch of the reboiler.

4. Turn off the Main power control switch.

5. Do not drain the hot liquid from the Reboiler. If necessary, the liquid within the

system could be drained only when the liquid is already cooled.

6. Allow the cooling water to run for some time.

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4.0 ANALYSIS AND DISCUSSION

Discuss all your results. The questions below only serve as a guideline. Your discussion

should not only limit to these questions.

1. Make a calibration graph based on your data obtained from Experiment A by

plotting Refractive index (RI) on the y-axis against mole fraction of ethanol on the x-

axis.

2. Determine the mole fraction of ethanol for the top and bottom product for each reflux

by refer to calibration graph.

3. Calculate the complete overall and component mass balance of the process.

4. Determine the number of stages that occur in the processes for each reflux by

construct the graph McCabe Thiele Method. Equilibrium data for ethanol-water

system is given in Appendix A.

5. Discuss the results obtained and effect of reflux ratio for ethanol-water mixture

separation

6. Discuss any possible errors in the experiment and state any recommendation to

improve the process.

5.0 REFERENCES

1. Treybal, R.E., Mass Transfer Operations, 3rd ed., Mc-Graw-Hill, 1981

2. McCabe & Smith, Unit Operations of Chemical Engineering, 5th ed, Mc-Graw-Hill,

1993

3. Geankoplis,C. J. Z., Mass Transport Phenomena, 4th Ed., Rine Hart Winston, New

York.

4. Coulson & Richardson, Chemical Engineering. Vol. 2 Pergamon Press, Oxford.

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APPENDIX A

Table of Results

Reflux ratio = 1.0

Rotameter reading R1 (L/hr) = __________________


Temperature T4 (oC) = __________________

Temperature T2 (oC) = __________________

Time, t (min)

TOP PRODUCT BOTTOM PRODUCTRefractive index

(RI) Mole fraction Refractive index

(RI) Mole fraction

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Reflux ratio = 1.5



Temperature T4 (oC) = __________________

Temperature T2 (oC) = __________________

Time, t (min)



(RI) Mole fraction

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Reflux ratio = 2.0



Temperature T4 (oC) = __________________

Temperature T2 (oC) = __________________

Time, t (min)



(RI) Mole fraction

051015202530

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APPENDIX B

Equilibrium Data for Ethanol-Water Mixtures

Mole fraction of ethanol in liquid, x Mole fraction of ethanol in vapor, y

0.00 0.00

0.05 0.38

0.10 0.53

0.40 0.75

0.60 0.79

0.80 0.86

0.94 0.94

0.90 0.91

0.94 0.94

0.96 0.96

0.98 0.99

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STEP BY STEP TO CONSTRUCT GRAPH MCCABE THIELE METHOD

1. Draw the equilibrium curve based on data given in Appendix B, by plotting mole fraction

of ethanol in vapor on the y-axis against mole fraction of ethanol in liquid on the x-axis.

2. Draw the 45-degree line( y =x)

3. Indicate distillate (xD), bottom (xB) and feed (xF) composition on the graph based on

data obtained from experiment.(refer to appendix A).

4. Draw the feed line (q line). For saturated liquid, this is a vertical line running from the

feed composition (xF) through the equilibrium curve.

5. For a specified reflux ratio, r, draw the 'rectifying' line (ROL). This rectifying line begins

at the point xD on the 45-degree line and has intercept on y-axis.

ROL equation:

6. Draw the 'stripping' line (SOL) by connecting the intersection of the feed line and the

rectifying line and the point xB on the 45-degree line.

7. Beginning at the point xD on the rectifying line, draw a horizontal line to the equilibrium

curve and then a vertical line to the operating (rectifying or stripping) line.

8. Repeat step 7 forming a staircase until you reach or pass the point xB on the 45-degree

line.

9. Each point where the staircase intersects the equilibrium curve denotes one stage in the

column.

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Sample Graph of McCabe Thiele Method

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exp 1 packed column distillation (1)

Documents

deionized water

batch distillation

separation of ethanol

distillation apparatus

water system

test tubes

packed distillation

vertical column