Introduction to distillation, what is the principle of distillation?

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A distillation method that uses reflux to separate liquid mixtures with high purity, is the most widely used liquid mixture separation operation in industry, and is widely used in petroleum, chemical, light industry, food, metallurgy and other sectors. Distillation operations are classified according to different methods. According to the mode of operation, it can be divided into continuous distillation and batch distillation; According to the component fraction of the mixture, it can be divided into binary distillation and multivariate distillation; According to whether additives affecting the vapor-liquid balance are added to the mixture, it can be divided into ordinary distillation and special distillation (including extractive distillation, constant boiling distillation and salt distillation).

If the distillation process is accompanied by a chemical reaction, it is called reactive distillation.

Taking advantage of the different boiling points and volatilization capacity of each component in the mixture, through the reflux of the liquid phase and the gas phase, the gas and liquid phases are reversed to multi-stage contact, and under the constraint of thermal energy drive and phase equilibrium relationship, the volatile components (light components) are continuously transferred from the liquid phase to the gas phase, while the non-volatile components migrate from the gas phase to the liquid phase, so that the mixture is continuously separated.

Rectification is actually a combination of multiple simple distillations. In the distillation stage, the low boiling point components of the gas phase are continuously refined and continuously enriched in the gas phase during the rising process of the gas phase, and the low boiling point product is obtained at the top of the column. In the distillation stage, in the process of decreasing the liquid phase, the low boiling point components are continuously distilled, so that the high boiling point components are continuously concentrated in the liquid phase, and the high boiling point products are obtained at the bottom of the column.

Fundamental Difference Between Rectification and Distillation:

1.Rectification is a combination of multiple simple distillations.

2.The relative volatility between the components in the manual excitation system of the distillation to be separated is small, and the relative volatility of distillation needs to vary greatly.

3.The degree of distillation separation is higher, and distillation can only be separated simply. Rectification is usually done in the rectification column.

The gas-liquid phases are contacted by countercurrent to carry out interphase heat and mass transfer. The volatile components in the liquid phase enter the gas phase, and the non-volatile components in the gas phase transfer to the liquid phase.

Principles of Rectification:Distillation is a method of partial gasification and partial condensation that is used multiple times and at the same time to separate the mixture more completely to obtain close to pure components.

The different volatility of each component in the mixture is used, that is, the light components in the liquid phase are transferred to the gas phase by the different vapor pressures of each component at the same temperature, and the recombinant components in the gas phase are transferred to the liquid phase, so as to realize the separation of the distillation column principle.

Theoretically, high-purity volatile components can be obtained in the liquid phase by multiple partial gasification, and high-purity volatile components can be obtained by multiple partial condensation in the gas phase, but the product quantity is very small due to the production of a large number of intermediate components, and the equipment is huge.

The distillation process in industrial production is operated by organically combining part of the gasification process and part of the condensation process in the distillation column.

Flow of the distillation unit:

A typical distillation unit is a continuous distillation unit, including a distillation tower, condenser, and reboiler, as shown in Figure 1-8. There are two types of column equipment used for rectification, namely plate column and packed column, but plate column is often used. In the continuous distillation operation, the raw liquid is continuously fed into the distillation column, and the product (distillate, kettle residue) is continuously obtained from the top and bottom of the column at the same time, so it is a steady operation process.

Distillation (distillation method, preparation for excavation) imitation.

Distillation is a separation process that separates each component by using the different volatility of each component in the mixture, and the commonly used equipment is a plate distillation column.

and packed distillation columns. The principle and equipment flow of precision distillation are the same as those of ordinary distillation, but the relative volatility between the components in the system to be separated is small (<, so high-efficiency precision packing materials are used to realize the separation and purification of the components to be separated. There are often isomers in the raw materials for the production of mono fragrances, a natural refined and dry oil.

Coexisting conditions, such as citronellol and rose alcohol that are present in natural essential oils such as gerania oil, rose oil, rose grass oil, etc., are optical isomers. The boiling point difference of these isomers is relatively small, and it is difficult to achieve the effective separation of this single fragrance with the general distillation process, so precision distillation has a wide range of applications in the production of single fragrance fragrances. The high-efficiency packing materials used in precision distillation columns include Q

Bulk packing such as dixon filler and mcmahon filler, as well as structured packing represented by screen corrugated filler (sulyer filler). The specific surface of these packing materials is large, the wettability is good, the liquid holding capacity and fluid resistance are small, but the diameter of the bulk packing tower should not be too large, otherwise the mass transfer separation efficiency will drop sharply, which is the "amplification effect" of the packed tower. The amplification effect of structured packing is small, so the application of screen corrugated structured packing is becoming more and more extensive.

The distillation unit consists of three parts: a heating and gasification part, a condensation part, and a receiving part.

Note: When distilling under reduced pressure, use a K-wire distillation head, a drained tube with a branch tube, or use a multi-ended drained tube.

It is necessary to replace zeolite with a capillary tube to prevent boiling.

Heating in a hot bath is required, and a thick-walled, pressure-resistant glass instrument is required.

Principle. The difference in the volatility of each component in the liquid mixture is used to partially vaporize the liquid mixture and subsequently condense the vapor part, so as to achieve the separation of the components contained in it. It is a unit operation that belongs to mass transfer separation. It is widely used in oil refining, chemical industry, light industry and other fields.

The principle is based on the separation of a two-component mixture. The material liquid is heated to partially vaporize, the volatile components are enriched in the vapor, and the involatile components are also enriched in the remaining liquid, which realizes the separation of the two components to a certain extent.

Qiaoyou Kai <>

The greater the difference in the volatile capacity of the two components, the greater the degree of enrichment described above. In industrial distillation equipment, the partially vaporized liquid phase is in direct contact with the partially condensed gas phase for vapor-liquid interphase mass transfer, and the result is that the refractory components in the gas phase are partially transferred to the liquid phase, and the volatile components in the liquid phase are partially transferred to the gas phase, that is, the partial vaporization of the liquid phase and the partial condensation of the vapor phase are realized at the same time.