CN-117800429-B - Polycarbonate factory solvent recovery system and application thereof

Abstract

The application relates to the field of wastewater recovery processes, in particular to a polycarbonate factory solvent recovery system and application thereof. The polycarbonate factory solvent recovery system at least comprises a flash tower, a stripping tower, a decanter, a steam nozzle and a storage tank, wherein the system structure is fixedly connected through a steam pipeline. The application provides a polycarbonate factory solvent recovery system, which can improve the integral separation capacity of the system, reduce the content of methylene dichloride in wastewater, reduce the content of other organic impurities in wastewater and improve the separation efficiency of the integral system and the consumption of less steam and energy by designing a flash tower.

Inventors

• REN ZHIGANG
• WANG WEILIN
• LU JINSHENG
• YANG WEIHAO
• ZHAO YUN

Assignees

• 深圳市元创化工科技有限公司

Dates

Publication Date

20260508

Application Date

20231130

Claims (3)

1. 1. A polycarbonate factory solvent recovery system is characterized by at least comprising a flash tower, a stripping tower, a decanter, a steam nozzle and a storage tank, wherein the system structure is fixedly connected through a steam pipeline; The flash tower sequentially comprises a bottom tower body, a middle tower body and an extension section tower body from bottom to top, wherein the extension section tower body comprises a feed inlet and a steam outlet; the decanter is fixedly connected with a feed inlet pipeline in the flash tower and is used for conveying materials to be treated; the top of the stripping tower comprises a reflux steam outlet which is fixedly connected with a reflux steam inlet pipeline of the flash tower to provide reflux steam for the flash tower; 6-12 flash tower plates are arranged in the middle tower body of the flash tower at equal-height intervals, and the flash tower plates are any one of antifouling tower plates; 3-6 baffle plates are arranged at equal-height intervals in the tower body of the extension section of the flash evaporation tower; The diameter ratio of the extension section tower body to the middle tower body in the flash tower is 1.2-1.4:1; the length of the extension section tower body in the flash tower is 8-12 times of the diameter of the middle tower body; The stripping tower further comprises a low-pressure flash evaporation inlet which is fixedly connected with a steam nozzle pipeline, and the steam nozzle is used for conveying steam with the total quantity of 10-15 bar for the stripping tower; And the steam outlet of the flash distillation tower and the discharge outlet at the bottom of the stripping tower are fixedly connected with a storage tank pipeline.
2. 2. The polycarbonate factory solvent recovery system of claim 1, wherein 0-10.5 bar of steam is introduced into a steam inlet of the flash tower.
3. 3. The method for recycling the solvent of the polycarbonate factory according to any one of claims 1-2, which is characterized by comprising the step of recycling the solvent of the polycarbonate factory by a phosgene method.

Description

Polycarbonate factory solvent recovery system and application thereof Technical Field The invention relates to the field of wastewater recovery processes, in particular to a polycarbonate factory solvent recovery system and application thereof. Background Polycarbonates (PC) are a high molecular polymer containing carbonate groups in the molecular chain, and can be classified into various types depending on the ester groups. Polycarbonate is used as one of amorphous engineering plastics, and has the characteristics of good heat resistance, good transparency and the like, so that the polycarbonate is widely applied to the fields of automobiles, electric appliances and medical care products. Among the existing preparation methods, the phosgene method for preparing the polymeric carbonate is a common preparation technology. At the same time, however, because of the process conditions of the phosgene process, more brine and organic-containing wastewater is produced, and factories and businesses are often accompanied by wastewater/solvent recovery systems for separating and recovering methylene chloride from the centrifuge-separated brine and various wastewater sources. The solvent recovered feed stream typically contains 13 to 15wt% NaCl and about 1wt% Na 2CO3. After stripping the methylene chloride, the wastewater stream is further purified for recycle to the chlor-alkali plant or to a public sewage treatment plant. The purpose of the solvent recovery system was to reduce the concentration of methylene chloride to below 200ppb wt (0.2 ppm wt) specification. Chinese patent CN217887031U provides a polycarbonate methylene chloride recovery system, the system structure of which mainly includes a devolatilization tower, a wash tank, an air cooler, a circulating water cooler and a liquid-liquid separator, and claims that it can ensure heat exchange efficiency, improve the efficiency of cooling gaseous methylene chloride into liquid, and finally improve the recovery rate of methylene chloride, but it also significantly enhances the utilization rate of energy and recovery efficiency. Accordingly, in order to further solve the above problems, the present application provides a polycarbonate factory solvent recovery system. Disclosure of Invention In order to solve the problems, the first aspect of the invention provides a solvent recovery system of a polycarbonate factory, which at least comprises a flash tower, a stripping tower, a decanter, a steam nozzle and a storage tank, wherein the system structure is fixedly connected through a steam pipeline. As a preferable scheme, the flash distillation tower comprises an intermediate tower body, an extension tower body and a bottom tower body, wherein the extension tower body comprises a feed inlet and a steam outlet, and the bottom tower body comprises a steam inlet, a reflux steam inlet and a bottom discharge outlet. As a preferable scheme, the diameter ratio of the extension section tower body to the middle tower body in the flash tower is 1.2-1.4:1. As a preferable scheme, the diameter ratio of the extension section tower body to the middle tower body in the flash tower is 1.25:1. As a preferable scheme, the length of the extension section tower body in the flash tower is 8-12 times of the diameter of the middle tower body. As a preferable scheme, the length of the extension section tower body in the flash tower is 10 times of the diameter of the middle tower body. As a preferred solution, the decanter is fixedly connected to a feed inlet pipe in the flash column, which carries the desired process material for the flash column. As a preferable scheme, 6-12 flash tower plates are arranged in the middle tower body of the flash tower at equal-height intervals, and the flash tower plates are any one of antifouling tower plates. As a preferable scheme, 11 flash tower plates are arranged at equal-height intervals in the middle tower body of the flash tower. According to the application, the flash tower is provided by design, so that the integral separation capacity of the system is improved, the content of dichloromethane in the wastewater is reduced, the content of other organic impurities in the wastewater is also reduced, and the separation efficiency of the integral system and the consumption of steam and energy are improved. The flash tower has enough trays to effectively reduce the use of the stripping tower, even eliminate the need of the stripping tower, and effectively reduce the use of steam. However, in order to satisfy the above technical effects, it is necessary to know the henry constant of dichloromethane and brine and the maximum solubility of dichloromethane in brine. The inventors have experimentally tested the relationship between henry constant and temperature and brine concentration and as shown in fig. 3, and the regression of the data resulted in the following functional formula h=78.2-9.25×t+33.5×c+0.182×t2, where H is henry constant, T is temperature