Paraxylene crystallization method

Abstract

The invention relates to a paraxylene crystallization method which solves the problems of high energy consumption, severe precooler scaling and difficult crystal washing in the prior art. The technical scheme of the paraxylene crystallization method comprises the following steps: feeding a mixed xylene raw material into a raw material intermediate tank; thickening crystal slurry in a crystal slurry tank through a thickener, thus obtaining a pre-separation mother solution and concentrated crystal slurry; feeding the pre-separation mother solution into a crystallizer, and crystallizing; separating the concentrated crystal slurry through a solid-liquid separator, thus obtaining a filtration mother solution and paraxylene crystals; feeding the filtration mother solution into the crystallizer, and crystallizing; heating to melt the paraxylene crystals in a melting tank; discharging the crystal slurry in the crystallizer in two parts, wherein crystal slurry I is returned into the crystallizer after being subjected to heat exchange through a sleeve pipe type crystallizer, and crystal slurry II is concentrated by the thickener to obtain a pre-separation mother solution and concentrated crystal slurry; and separating the concentrated crystal slurry through the solid-liquid separator to obtain paraxylene crystals and a crystallized filtration mother solution, and returning the paraxylene crystals into the crystal slurry tank. Thus, the problems are well solved; and the paraxylene crystallization method can be used for production of paraxylene.

Description

technical field [0001] The invention relates to a paraxylene crystallization method. Background technique [0002] Paraxylene is an important raw material for the polyester industry, mainly used to produce purified terephthalic acid (PTA) or purified dimethyl terephthalate (DMT), and then produce polyester (PET) from PTA and DMT, and separate Mixed xylene is the main production method of p-xylene. Mixed xylenes are mainly composed of p-xylene, m-xylene, o-xylene and ethylbenzene. The difference between the boiling points of each component is small, but the difference in melting point is large. The crystallization method can be used to separate p-xylene. [0003] Patent US5498822 discloses a crystallization method for separating p-xylene. In this method, the raw material of mixed xylene is pre-cooled by a precooler, and then a high-purity p-xylene product is obtained by separating through a single-stage crystallization process. In the actual crystallization production proce...

AI Technical Summary

Problems solved by technology

[0004] The technical problem to be solved by the present invention is the problems of high energy consumption, serious fouling of the precooler and difficult crystal washing in the existing crystallization method for producing p-xylene, and a new crystallization method for p-xylene is provided

Images