03 Short Path Distillation.docx

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Experiment 3 BKF3731 Unit Operation Laboratory

1

1.0 ABSTRACT

This experiment is to study the effects of stirrer speed and temperature on the efficiency

of ethylene glycol-water separation in a short path distillation. The objectives of this

experiment are to study on the effects of the parameters on the thermal separationefficiency using short path distillation. For this experiment, it is divided to 2 parts. Firstly

is test about the factor of stirrer speed and secondly is test about effect of temperature.

For part 1, ethylene glycol and water with a ratio of 5:5 at total of 1 litre is mixed and

stirred. Thermostat is set on 70 °C, chiller at 12°C, and vacuum pump at 250mbar. Then,

the stirrer and feed pump is on and set to 50rpm. After 5 minute, the volume of distilled

from V-104 and volume of concentrated V-105-107 is recorded. The experiments is

repeated by using 100rpm, 200 rpm and 220rpm. For the second part, the experiment is

test about the effect of temperature. The stirrer speed is maintained at 220rpm, the contact

time is 5 minutes and the vacuum pressure is 100mbar while ethylene glycol and water

with a ratio of 7:3 at total of 1 litre is mixed and stirred. Then the evaporator is set on

70 °C. . After 5 minute, the volume of distilled from V-104 and volume of concentrated

V-105-107 is recorded. The experiments is repeated by changing temperature to 72°C,

74°C, 76°C and 80°C. Then we can calculate the separation efficiency. From the result,

graph of Separation Efficiency (%) against Stirrer Speed (rpm) and Separation Efficiency

(%) against Temperature (°C) is plotted. From the graph, we can conclude that the higher

the stirrer speed and temperature, the higher the separation efficiency. When the stirrer

speed increased from 50 rpm to 220 rpm, the separation increased from 99.63% to

99.76%. While when the temperature increased from 70°C to 80°C, the separation

efficiency increased from 99.76% to 99.79%. Therefore, effects of stirrer speed and

temperature will affect the efficiency of ethylene glycol-water separation in a short path

distillation.




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2.0 METHODOLOGY FLOWCHART

Ethylene glycol and water are mixed

with a ratio of 5:5 at total of 1 litre in

a beaker.

The mixture is then stirred

homogeneously

Ensure that all the valves are initially

closed

The cold trap is filled with ice

Ethylene glycol and water mixture is preheated to 50°C

Switch ON the main power supply ofthe control panel

Set thermostat at 70°C and vacuum

pump pressure at 250mbar

To adjust the desired stirrer speed,

adjust knob button at stirrer

On the feed pump and set it to 10rpm

and on stirrer to desired speed

Run every set of experiment for 5

minutes and record the distillatevolume, concentrate volume,

composition of Ethylene glycol in

each distillate and concentrate in table

Repeat the experiment with different

operating parameters as shown inresult and discussion

Shut down the equipment by

following the operating procedure




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3.0 RESULTS

3.1 Effect of stirrer speed

Vacuum pressure, PT-200 250mbarEvaporator Temperature, TT-100 70°C

Fed Flow Rate 19.656 ml/min

Contact time 5 min

EG-water ratio 5:5

3.2 Effect of evaporator temperature

Vacuum pressure, PT-200 250mbarStirrer speed, M-500 220 rpm

Fed Flow Rate 19.656 ml/min

Contact time 5 min

EG-water ratio 5:5

Time

Start

Stirrer

Speed

(rpm)

Distillate Concentrate Separation

Efficiency

(%)

Volume

(ml)

Composition

(%)

Volume

(ml)

Composition

(%)

1405 50 6.5 3.0 90 57.6 99.63

1410 100 8 2.4 95 58.6 99.66

1415 200 11 1.6 92 59.8 99.68

1420 220 11 1.2 90 60.0 99.76

Time

Start

Temp.

(°C)

Distillate Concentrate Separation

Efficiency

(%)

Volume

(ml)

Composition

(%)

Volume

(ml)

Composition

(%)

1425 70 11 1.2 90 60.0 99.76

1430 72 11 1.2 92 62.0 99.77

1435 74 11 1.2 93 63.6 99.78

1440 76 11 1.2 94 65.0 99.78




5

99.60

99.62

99.64

99.66

99.68

99.70

99.72

99.74

99.76

99.78

0 50 100 150 200 250

S e p a r a t i o n E f f i c i e n c y ( %

)

Stirrr Speed (rpm)

Figure 4.1: Separation Efficiency (%) against Stirrer Speed (rpm)

Figure 4.1 show the relationship between the stirrer speeds with the separation

efficiency under a constant temperature which is 70 °C. When the stirrer speed is

increased from 50 rpm to 100 rpm, the separation efficiency increased from 99.63% to

99.66%. The stirrer speed was then increased to 200 rpm and the separation efficiency

also increased to 99.68. Last but not least the stirrer speed was then set to 220 rpm and

the separation efficiency also increase to 99.76%. Hence we can say that the separation

efficiencies increase when the stirrer speeds are increased and the separation efficiencies

increased because of the composition of ethylene glycol in the concentrate increase while

the composition of ethylene glycol of distillate decrease as the stirrer speed increase.

Short path distillation will also affected by the change of pressure. Short path

distillation is a distillation technique that usually carried out at reduced pressure. (

Michael Albers, Alzenau-Hörstein) Hence if the pressure is increased, the performance of

the short path distillation unit will be lower as the mixture need a higher temperature to

be separated. The higher the pressure, the higher the temperature needed for a liquid to

achieve boiling point.




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99.75

99.76

99.76

99.77

99.77

99.78

99.78

99.79

99.79

99.80

99.80

68 70 72 74 76 78 80 82

S e p a r a t i o n E f f i c i e n c y ( % )

Temperature (°C)

Figure 4.2: Separation Efficiency (%) against Temperature (°C)

Figure 4.2 show the relationship between the temperatures with the separation

efficiency with the stirrer speed set as constant at 220 rpm. When the temperature

increased from 70°C to 80°C, the separation efficiency increased from 99.76% to

99.79%. At temperature 74°C and 76°C, we can see that the separation efficiency remainthe same although the composition of ethylene glycol in the concentrate increase and the

composition of ethylene glycol of distillate decrease. The increase in temperature only

cause a slight increase in separation efficiency. From here we can say that the higher the

temperature the higher the separation efficiency and the increase in the separation

efficiency affected by temperature is more drastic compare to the increase in the

separation efficiency that cause by stirrer speed.

The higher the temperature, the higher the separation efficiency. This is because

in higher temperature, the kinetic energy of particles is higher. This will produce more

collision per unit time between the reactant particles. (H.B Moller, S.G. Sommer, B.K.

Ahring) Therefore the efficiency collision frequency will increase hence increase the

separation efficiency in short path distillation.




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5.0 CONCLUSION AND RECOMMENDATION

As a conclusion, temperature and stirrer speed is the parameter that affects the

efficiency on the thermal separation. This was proven from Figure 4.1. When the stirrerspeed was increased from 50 rpm to 220 rpm, the separation increased from 99.63% to

99.76%. Besides, from Figure 4.2, when the temperature increased from 70°C to 80°C,

the separation efficiency increased from 99.76% to 99.79%. Therefore, effects of stirrer

speed and temperature will affect the efficiency of ethylene glycol-water separation in a

short path distillation. The faster the stirrer speed, the higher the separation efficiency,

and the higher the temperature, the higher the separation efficiency.

As recommendation, we must ensure the accuracy of stirrer speed and reduce the

lagging time for the stirrer to be at their exact speed. Besides, the RI meter which we use

to determine the composition of Ethylene glycol must be cleaned with soft tissue every

time after use to prevent inaccurate reading. The valve of chiller must opened to balance

the pressure in the chamber to prevent the distillate and concentrate undergo backflow.

The Ethylene glycol mixture must be also handled with care as it is quite corrosive to

human body.

6.0 REFERENCE

1) Christie John Geankoplis, Transport Processes and Separation Process Principles,

4th

Edition

2) H.B Moller, S.G. Sommer, B.K. Ahring , Separation efficiency and partice size

distribution in relation to manure type and storage conditions

3) Ali Eliassi and Hamid Modarress, Densities of Poly(ethylene glycol)+Water

mixtures in the298.15-328.15 K Teperature Range

4) Michael Albers, Alzenau-Hörstein, 2012, Application of Short-Path Distillation

for Processing Edible Oils and Fats, Retreived from

http://www.dgfett.de/meetings/archiv/leipzig/abstract_ albers.pdf at 17th April

2012

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