Difference Between Distillation and Extraction Process

In distillation as in the distilllation of binary mixture, the calculation of equilibrium stages uses mass and enthalpy balances and vapour-liquid equilibria. 

A mass balance can be written for each component for the column or for each stage. When separation by distillation is ineffective or very difficult, liquid extraction is one of the main alternatives to consider. 

The close-boiling mixture of substances that cannot withstand the temperature of distillation even under a vacuum may often be separated from impurities by extraction, which utilizes chemical differences instead of vapour pressure differences.

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Difference Between Distillation and Extraction

Distillation process

1. Distillation/fractionation is an operation in which the constituents of a liquid mixture are separated by using thermal energy.

2. Distillation utilizes differences in vapour pressure of different components at the same temperature to affect a separation.

3. In distillation, relative volatility is used as a measure of the degree of separation.

4. In distillation, a new phase is created by the addition of heat.

5. In distillation mixing and separation of phases is easy and rapid

6. Distillation/fractionation gives almost pure products.

7. It does not offer more flexibility in the choice of operating conditions.

8. It requires thermal energy.

9. It needs heating and cooling provisions.

10. It is a primary choice for the separation of the components of a liquid mixture.

11. Extractive distillation is the extraction of the vapour phase with solvent.

Extraction Process

1. Extraction is an operation in which the constituents of a liquid mixture are separated by using an insoluble liquid solvent.

2. Extraction utilizes differences in the solubility of components to effect a separation.

3. In extraction, selectivity is used as a measure of the degree of separation.

4. In extraction, a new insoluble liquid phase is created by the addition of solvent to the original mixture.

5. In extraction, phases are hard to mix and harder to separate.

6. The extraction itself does not give pure products and needs further processing.

7. It requires mechanical energy (for mixing and separation).

8. It does not need heating and cooling provisions.

9. It is a secondary choice for the separation of the components of a liquid mixture.

10. Liquid extraction is the extraction of the liquid phase with solvent. 

Take these Notes is, Orginal Sources: Unit Operations-II, KA Gavhane