short path distillation

Chemical Engineering Laboratory II BKF3751

EXPERIMENT 7: SHORT PATH DISTILLATION

OBJECTIVE

1. To introduce the short path distillation principles using continuous system.

2. To observe the effects of stirrer speed and temperature on the efficiency of separation, e.g

ethylene glycol-water.

INTRODUCTION

This Short Path Distillation is a thermal separation process for thermal sensitive products.

Short residence time and low evaporation temperature will cause a minimum thermal stress to the

distilled product. Typical applications are high molecular organic compounds particularly from the

field of chemistry, pharmaceutical and food industry. Distillation is one of the most important

thermal separation methods.

Short path distillation is a continuous separation process working under vacuum conditions.

Evaporation takes place from a heated wiped film. Caused by the pressure drop between the place

of evaporation and the vacuum system the operating pressure in typical wiped film evaporators with

external condenser is limited to some millibars.

The considerably lower pressure in the short path evaporator is obtained by the short

distance for the vapours on their way from the evaporator surface to the condenser. In addition,

the cross section area of flow is equal to the evaporator surface, so that there is only a minor

pressure drop between evaporator and condenser

EQUIPMENT/APPARATUS/MATERIAL

1. Short Path Distillation Unit

2. Ethylene glycol – water

mixture


EXPERIMENTAL PROCEDURES

1. Mix the ethylene glycol and water with a ratio of 7:3 at total of 1 litre in a beaker. Then stir

the mixture homogeneously.

2. Check that all valves are initially closed except the valves HV02, HV04, HV05, HV11 and

HV12. Ensure that the cold trap is filled with dry ice.

3. Remove valve HV-01 and fill the feeding funnel V-100 with the homogeneous mixture.

4. Switch ON the main power supply at the control panel.

5. ON computer or the software program.

6. Set the thermostat at 70°C, Chiller at 12°C and vacuum pump pressure at 100mbar.

Manually maintain the pressure throughout the experiment. [To adjust vacuum pump

pressure, manually adjust valve, V14. To adjust the desired flow rate, adjust the opening

valve HV03. To adjust the desired stirrer speed, adjust it from the software].

7. Open valve HV-13 to allow for some of the hot bath to circulate through the heating jacket

of the feeding funnel to pre-heat the feed in the funnel.

NOTE: Valve HV13 must be close before switching off the thermostat, B-400.

8. Once the chiller temperature and thermostat temperature have reach the set points, the

equipment is ready for experiment

9. For every set of experiment, run for 10 minutes. After 10 mins, records down the volume of

distillate from V-104 and volume of concentrate from V-105-107.

10. Repeat the experiment with different operating parameters as shown in the table in result and

discussion.

11. Follow the operating procedure to shut down the equipment. DO NOT let the wiper roller to

run without the flow of feed.


SAMPLING PROCEDURE

1. For every batch of experiment, to ensure the feed flowrates are the same, HV03 should not

be close at each sampling. To do this, switch off the vacuum pump, open HV07, HV08 and

HV09 to let the condensate and distillate to flow into V-104 to V-107 respectively.

2. After all the liquid are flows into each vessel. Close back HV07, HV08 and HV09. Continue

to run the next experiment by switching on the vacuum pump again.

3. The collected distillate and condensate can then be used for further testing.

4. The feed flowrate is calculated by dividing the total volume of sample collected to the total

time taken.

GENERAL SHUT-DOWN PROCEDURES

1. Switch off vacuum pump.

2. Close valve HV03 to stop feeding.

3. Switch off stirrer motor.

4. Turn off thermostat. Close HV13.

5. Open valve HV 01, HV 06 and HV 07.

6. After 15 minutes, switch off chiller and turn off the main power.

NOTE: DO NOT attempt to remove any vessel while the vacuum pump is running.

RESULT

1. Effect of stirrer speed

Vacuum pressure, PT-200 100mbarEvaporator Temperature, TT-100 70°C

Feed Flow rate ml/minContact time 10 min

EG-water ratio 7:3

Time Start Stirrer Speed(rpm) DistillateVolume (ml)

ConcentrateVolume (ml)

Separation Efficiency (%)


50

100

200

220

2. Effect of evaporator temperature

Feed flow rate ml/minStirrer speed, M-500 220rpm

Vacuum pressure 100mbar

Contact time 10min

EG-water ratio 7:3

Time Start Temp (°C) DistillateVolume (ml)

ConcentrateVolume (ml)

Separation Efficiency (%)

7072747680


ANALYSIS AND DISCUSSIONS:

1. Plot a graph of stirrer speed vs. separation efficiency and evaporator temperature

vs. separation efficiency.

2. Discuss the effects of the parameters on the thermal separation efficiency.

3. Briefly explain the importance and application of short path distillation system in

industry.

short path distillation

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