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What is the Difference Between Distillation and Rectification?

Aug. 15, 2023

Distillation VS Rectification

What is Distillation?

Distillation is a unit operation that can be used to separate homogeneous liquid mixtures. It utilises the different volatility of the components of the mixture to be separated. Volatility refers to the tendency of a substance to pass from the liquid phase into the gas phase. Examples of volatile liquids include acetone, alcohol and petrol. Distallation Plant Details

What is Rectification?

Rectification is an application of distillation. It is used for substances that are required in high purity and/or large quantities, for example to fractionate crude oil. If the distillate obtained during distillation is distilled again, a new distillate is obtained with an even higher concentration of volatile components. As the procedure is repeated, the concentration of volatile components in the distillate increases on each occasion.

In practice, this multi-stage distillation process is carried out in the form of countercurrent distillation (rectification) in a column. 

Key Differences between Distillation and Rectification

● Purpose

The primary purpose of distillation is to separate components based on their boiling points, whicle rectificatio aims to enhance the purity of a substance through repeated distillation cycles.

● Process Variation

While both distillation and rectification involve vaporization and condensation, rectification emphasizes repeated cycles of this process to achieve higher purity levels.

● Purity Levels

Distillation results in relatively lower purity compared to rectification. Rectification achieves higher purity levels through its multiple distillation steps.

Now we will explain distillation and reactification seperately in design technology and principle&process.

Distillation Design Technology

By using the difference in the volatility of the components in the liquid mixture, the liquid mixture is partially vaporized and the vapor is partially condensed, so as to achieve the separation of the components it contains. It is a unit operation that belongs to mass transfer separation. Widely used in oil refining, chemical, light industry and other fields.

What is the Difference Between Distillation and Rectification?cid=191

Distillation Technology

The principle is based on the separation of a two-component mixture. The material liquid is heated to make it partially vaporized, and the volatile components are concentrated in the vapor, and the non-volatile components are also concentrated in the remaining liquid, which achieves the separation of the two components to a certain extent. The greater the difference in volatility of the two components, the greater the degree of enrichment described above. In industrial distillation equipment, a partially vaporized liquid phase is brought into direct contact with a partially condensed gas phase for vapor-liquid interstitial mass transfer. As a result, the non-volatile components in the gas phase are partially transferred to the liquid phase, and The volatile components are partially transferred to the gas phase, that is, partial vaporization of the liquid phase and partial condensation of the vapor phase are achieved at the same time.

Distillation Principle and Operation Process

Simple distillation is a batch operation process. The feed liquid is added to a distillation kettle, and the liquid is heated and boiled under constant pressure to continuously vaporize the liquid. The steam generated one after the other is cold-leached and used as the top product, where the volatile components are relatively enriched. During the distillation process, the volatile matter concentration of the liquid in the kettle continuously decreased, and the volatile matter concentration in the steam also decreased accordingly.

What is the Difference Between Distillation and Rectification?cid=191

To achieve high-purity separation, rectification can be used. Distillation is the most commonly used distillation method. One part is returned to the top of the column, which is called reflux liquid, and the rest is continuously discharged as the top product (distillate). In the upper part of the tower (above the feeding position), the countercurrent contact and the material and energy transfer are performed between the rising steam and the reflux liquid. The bottom of the column is equipped with a reboiler (distillation kettle) to heat the liquid to produce steam. The steam rises along the tower, contacts the falling liquid countercurrently and conducts material energy transfer, and the bottom of the tower continuously discharges part of the liquid as the bottom product. The rising steam is partially condensed many times, and the temperature gradually decreases. The concentration of volatile component A gradually increases. The falling liquid is partially gasified many times. The temperature gradually increases, and the concentration of non-volatile component B gradually increases. The concentration gradually decreases, the temperature distribution in the tower gradually decreases from the bottom to the top, and the concentration of the A component gradually increases from the bottom to the top. In the rectification section, the lower part of the column has completed the concentration of the heavy components in the descending liquid, that is, the light component is proposed, so it is called the stripping section. 

In such a column, a two-component mixture can be continuously separated High purity light and heavy two components. It can be seen that the difference between rectification and distillation lies in 'reflux'. Reflux is a necessary condition for gas and liquid contact mass transfer.

Rectification Principle and Operation Process

Difference Between Distillation and Rectification

The liquid mixture to be separated (feed) is fed to the column and partially evaporates on its way to the bottom of the column where it is heated to boiling. The vapour produced moves upwards inside the column, exits it at the top and is condensed. Part of the condensate is carried away as top product. The remainder flows back into the column and moves downwards as liquid phase.

Due to column internals, such as bubble cap trays or random packings, the downward-moving liquid phase is subjected to an intensive exchange of heat and material with the upward-moving vapour phase. The less volatile components of the vapour phase condense and increase in concentration in the liquid phase. At the same time, the condensation heat released evaporates the more volatile components of the liquid phase. These processes in the column increase the vapour phase concentration of volatile components moving from the bottom to the top of the column. The liquid phase concentration of less volatile components increases in the opposite direction, from the top of the column to the bottom.

SL Tec is a professional Distillation Plants contractor and distillation formula & production technology provider at low cost, we can guide you with our formular and technology to help you improve your production efficiency. Welcome to contact us to get more details of distillation production process from us at any time, and we would like to offer any technical guidance to you.

Difference Between Distillation and Rectification

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