Lactide continuous melt crystallization purification system and method

Abstract

The invention discloses a lactide continuous melt crystallization purification system and method. The system comprises a mixed feeding system, a crude lactide crystallization section, a crystal sweating purification section and a mother liquor crystallization recovery section. The mixed feeding system is connected with the crude lactide crystallization section through a pumping pipeline. A crystal mush outlet is formed in the bottom of the crude lactide crystallization section and is connected with the crystal sweating purification section, and the top of the crude lactide crystallization section is provided with a mother liquor outlet connected with the mother liquor crystallization recovery section. A product outlet and a backflow liquid inlet are formed in the bottom of the crystal sweating purification section, and a mother liquor outlet is formed in the top of the crystal sweating purification section and is connected with the crude lactide crystallization section. A crystal slurry outlet is formed in the bottom of the mother liquor crystallization recovery section and connected with a solid-liquid separation system, and a solid phase outlet is connected with a mixed feeding system. A circulating branch is arranged at a liquid phase outlet and returns to the mother liquor crystallization recovery section. By adopting the system and the method disclosed by the invention, efficient separation and purification of the crude lactide can be realized, and the system has the advantages of high product purity, low system energy consumption, high yield, continuous and stable operation and the like.

Description

technical field [0001] The invention belongs to the technical field of chemical separation, and in particular relates to a lactide continuous melting crystallization purification system and method. Background technique [0002] With the advancement of science and technology, especially the advancement of chemical synthesis technology, many new chemical materials have been brought, which have provided many conveniences for human production and life. But at the same time, the synthesis and use of many traditional materials consume a large amount of non-renewable resources and bring a huge burden to the environment. In the 21st century, with the concept of sustainable development and harmonious coexistence between man and nature, renewable and degradable environmentally friendly chemical materials are increasingly favored by the market, and polylactic acid (PLA) is just such a Green chemical material. [0003] Polylactic acid is a new type of biodegradable material, which use...

AI Technical Summary

Problems solved by technology

There are problems such as low production efficiency, high energy consumption in the production process, high labor intensity, large fluctuations in product quality between batches, and unstable product quality.

In addition, because the batch process can only provide one equilibrium stage in theory, the separation efficiency is poor

It is usually required that the feed crude lactide has a higher purity. For example, the feed concentration corresponding to the batch crystallization section of the above two prior art patent documents is greater than 92%. For low-concentration crude lactide, it is necessary to rely on rectification or Evaporation means for preliminary purification, the system is more complicated, and the scope of application of the corresponding technical solutions is limited

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