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Fractional distillation

By Thomas Huang December 5th, 2023 85 views
    4.1 The difference between the fractionation column and condenser
          4.2.1 Laboratory fractionating apparatus
          4.2.3 Industrial Fractional Distillation Equipment

I, What is Fractional Distillation?

Fractional distillation is a method of separating several liquid mixtures with different boiling points. It is a physical change because no new substances are generated.

II, The process of fractional distillation

The procedure of fractional distillation
How does the vapor condense at different temperatures?
2.1 After the mixture boils, the vapor enters the fractionating column and is partially condensed.
2.2 On its way down the condensate comes into contact with the vapor, which continues to rise, so they start exchanging the heat.
The high-boiling component of the vapor is condensed, while the low-boiling component in the vapor is still rising steam.
The low-boiling component in the condensate is vaporized, and the high-boiling component is still liquid down.
The result is the vapor has more low-boiling point components, and the condensate has more high-boiling point components.
2.3 During the procedure a dozen times of heat exchanges happen, which is equivalent to many consecutive ordinary distillations. As a result, the vapor of the low-boiling-point component keeps rising and is distilled out; the high-boiling-point component keeps flowing back into the distillation flask.

III, Fractional Distillation vs distillation

Same point  Both of them are processes of separating several components with different boiling points by heating a liquid mixture.
Differences Apparatus Fractionation device and distillation device are basically the same, except the fractionation device has a fractionation column, while the distillation device does not.
Precision When the boiling points of different components differ by about 25°C, they can only be separated by fractional distillation.
Pressure Fractional distillation is carried out at atmospheric pressure to obtain a low-boiling fraction and then carried out under reduced pressure conditions to obtain a high-boiling fraction. If a certain fraction also contains a variety of compounds, it can be further fractionated.
Efficiency To separate certain mixed liquid substances, it needs multiple times of distillations which is cumbersome, time-consuming, and wasteful. But it only requires a one-time fractional distillation operation, the separation can be done.

IV, Fractional distillation equipment

In the fractionation process, the fractional distillation column is the feature apparatus that distinguishes fractional distillation from distillation.

4.1 The difference between the fractionation column and condenser

Although both the fractionating column and condenser have the function of condensation, they have different roles.
4.1.1 Fractionating columns are mainly used for separating liquid mixtures, whereas condensers are mainly used for condensing evaporated liquids.
4.1.2 The fractionating column causes the evaporated product to rise gradually to the top, achieving a gradual separation of the mixture. Whereas, the condenser tube cools the gas that escapes the vapor to a liquid.
4.1.3 Fractionating columns focus on separation effort while condensing tubes focus on the condensation of the evaporated product.

4.2 Classification of Fractional Distillation Apparatus

4.2.1 Laboratory fractionating apparatus Glass instruments
Below is a typical set of glass fractional distillation instruments 
Glass instruments A,Lamp 
B,  Round-bottomed flask
C,  Fractionation column
D,  Condenser
E,  horn tube
F,  Thermometer Metal instruments
Under certain extreme conditions, where glass instruments are not adequate for fractionation, metal instruments are used.
Another situation requires that the fractionation be carried out directly after the reactants have been generated, and metal instruments are also used.
Metal instruments Specification:
Volume: 5L
Material: stainless steel
With Mechanical sealed Agitator
Heating: Electric heating
Heating Power: 750W
This is a type of reactor system called by WHGCM as a Fractional Distillation reactor.
Reactor, feed tank, fractionation column, condensers, reflux tube, collection tank, pressure regulating system, heating and cooling system, intelligent control system

4.2.2 Pilot Fractional Distillation Equipment

Pilot Metal instruments Specification:
Volume: 50L
Material: Hastelloy
With Magnetic sealed Agitator
Heating: Electric heating
Heating Power: 1.5 KW
This is also a type of reactor system called by WHGCM as a Fractional Distillation reactor.
Reactor, fractionation column, condenser, collection tank, buffer tank, pressure gauge

4.2.3 Industrial Fractional Distillation Equipment

The most common and typical industrial fractional distillation unit is the fractional distillation column used in the petroleum industry.
fractional distillation column used in oil industry
Another type of continuous reactor system is used in the chemical industry, which contains fractionation operations.
For example, the Unsaturated Polyester Resin Production Equipment is used as a key equipment for the production of Unsaturated Polyester Resin, Phenolic Resin, Epoxy Resin, ABS Resin, and Paint.
Fractional distillation reactor system

V, Applications of fractional distillation

6.1、Chemical experiments
6.2、Separation of fine chemical substances
6.3    Continuous fractionation
e.g. fractional distillation of coal tar; fractional distillation of petroleum; Polyester Resin Production
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