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What is Distillation?

Oct. 28, 2020

The distillation tower supplier will talk about the information about distillation technology.

It is well known that distillation is the process of separating components or substances from a liquid mixture by using selective boiling and condensation. Distillation can result in substantially complete separation (almost pure components), or the partial separation effect can increase the concentration of selected components in the mixture.

In either case, the process takes advantage of the difference in volatility of the components of the mixture. In industrial chemistry, distillation is actually a unit operation of universal importance, but it is a physical separation process, not a chemical reaction.

1. Distillation definition

Heating the liquid to boiling, turning the liquid into vapor, and then cooling the vapor to condense into a liquid. The combined operation of these two processes is called distillation.

A. Simple distillation

Under certain pressure, the liquid mixture is heated in the distillation kettle. When it is heated to a certain temperature, the liquid begins to vaporize. The generated steam is immediately drawn out and continues to be heated. The steam is continuously formed and drawn out, and it is condensed and cooled into a liquid. The distillate with different composition ranges is introduced into different containers for storage. This operation is called a simple distillation.

Features: Low processing capacity and low separation effect.

Scope of application: only suitable for small rough separation or as preliminary processing.

B. Balanced distillation

If the mixed liquid is heated to boil, and the vapor phase and the liquid phase are kept in close contact for a long time, and the vapor and liquid phases reach an equilibrium state, the two phases are finally moved into the separator for separation, this operation is called equilibrium distillation.

Distillation Tower

2. Application of distillation

The main difference between laboratory scale distillation and industrial distillation is that laboratory scale distillation is usually carried out batchwise, while industrial distillation is usually carried out continuously. In batch distillation, the composition of the raw materials, the vapors of the distillation compound, and the distillate change during the distillation process.

In batch distillation, a batch of feed mixture is added (supply) to the distiller and then separated into component fractions. These component fractions are collected from the most volatile to less volatile, and the bottom (the remaining least volatile or The non-volatile fraction) is removed at the end. The distiller can then be recharged and the process repeated.

In continuous distillation, by carefully replenishing the feedstock and removing distillates from the vapor and liquid in the system, the feedstock, vapor, and distillate maintain a constant composition. 

This leads to more detailed control of the separation process.

3. The oldest simple distillation apparatus

The pot distillation pot is the oldest distillation equipment;

Mainly composed of three parts: preheater, distillation pot, and serpentine condenser;

The whole pot is generally made of copper. There are four reasons: one is that copper has good thermal conductivity, and the other is good acid resistance; the third is to act as a catalyst to promote the synthesis of aromatic substances; the fourth is to make butyric acid and hexanoic acid form insoluble copper salts Precipitation, reducing the acidity of the liquor after distillation.

When distilling mixed liquids with large differences in boiling points, the ones with the lower boiling points are steamed out first, the ones with higher boiling points are steamed out later, and the non-volatile ones are left in the distiller. In this way, the purpose of separation and purification can be achieved.

Obviously, distillation can separate volatile and non-volatile substances, as well as liquid mixtures with different boiling points. However, the boiling points of the components of the liquid mixture must differ greatly (at least 30°C) to obtain a better separation effect.

Sanli Fengxiang provide several kinds of distillation apparatus.

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