CN-117398940-B - Recovery device and recovery method of BDO in PBAT production

Abstract

The invention discloses a recovery device and a recovery method of BDO in PBAT production, wherein the recovery device comprises a process tower and a BDO vacuum system, a pipeline at the bottom of the process tower is divided into two paths after passing through a shielding pump, one path is connected with an intermediate BDO storage tank, the other path is connected with a BDO evaporator and a liquid seal tank through a heat exchanger to form a hot fluid path, a refrigerant inlet of the heat exchanger is connected with a BDO collecting tank, and a refrigerant outlet is connected with the process tower to form a cold fluid path, so that the production energy consumption is reduced and the stability of the vacuum system is improved. According to the recovery method, through heat exchange between the hot fluid of the process tower and the cold fluid of the BDO collecting tank, the hot fluid flows into the BDO evaporator and the liquid seal tank of the vacuum system to supplement working fluid, the cold fluid enters the process tower to supplement tower bottom liquid of the process tower, the content of oligomers in BDO in the liquid seal tank and the consumption of fresh BDO are reduced, and the BDO balance problem is solved. Meanwhile, the water content of the middle BDO storage tank is reduced, the esterification rate of the esterification system is improved, and the full recycling of high-quality BDO is realized.

Inventors

• WU HUAZHI
• GAO JIA
• HUANG JUAN
• SHI LUFEI
• SUN HAO
• ZHANG ZHIPENG

Assignees

• 中国石油化工股份有限公司
• 中国石化仪征化纤有限责任公司

Dates

Publication Date

20260508

Application Date

20221128

Priority Date

20220713

Claims (6)

1. 1. A BDO recovery method in PBAT production is carried out by adopting a BDO recovery device in PBAT production, and is characterized in that the device comprises a process tower (1) and a BDO vacuum system, wherein a pipeline at the bottom of the process tower (1) is divided into two paths after passing through a shielding pump, one path is connected with an intermediate BDO storage tank (3), and the other path is connected with a BDO evaporator (6) and a liquid seal tank of the BDO vacuum system through a heat exchanger (5) to form a hot fluid path; The recovery method comprises the following steps that the refined hot fluid in the process tower (1) is used as a heating medium of a heat exchanger, the cold fluid in the BDO collecting tank (4) is used as a cooling medium of the heat exchanger (5), after heat exchange in the heat exchanger (5), the hot fluid flows into the BDO evaporator (6) and a liquid seal tank of a vacuum system to supplement working fluid, and the cold fluid enters the process tower (1) to supplement tower bottom liquid of the process tower (1).
2. 2. A method for recovering BDO in PBAT production according to claim 1, wherein a filtration process is added before said hot fluid enters the heat exchanger (5).
3. 3. The method for recovering BDO from PBAT production of claim 1, wherein said cold fluid is a liquid mixture of BDO and water after displacement by an esterification, polycondensation system liquid ring pump.
4. 4. A method for recovering BDO in PBAT production according to claim 1, wherein said liquid seal tank is divided into a polycondensation spray system BDO liquid seal tank (7) and a polycondensation spray system BDO liquid seal tank (8).
5. 5. A method for recovering BDO in PBAT production according to claim 1, wherein a filter is provided at the inlet of said heat exchanger (5).
6. 6. The method for recovering BDO from PBAT production of claim 1, wherein said pipeline is provided with a hand valve, a regulating valve and a flow meter.

Description

Recovery device and recovery method of BDO in PBAT production Technical Field The invention relates to polyester production equipment and a process, in particular to a recovery device and a recovery method of BDO in PBAT production. Background The PBAT has good biodegradability, is mainly used for film products such as packaging, mulching films, shopping bags, garbage bags, continuous rolling bags, express bags, takeaway and the like, and reduces the environmental pollution problem caused by the use of the traditional film. In the production process, BDO (1, 4-butanediol) is extracted from the tower bottom of the process tower and is collected into a BDO intermediate storage tank for slurry preparation. BDO temperature extracted from the tower bottom of the process tower is higher and is normally 170-200 ℃ and the boiling point of THF is 66 ℃, and in order to reduce THF volatilization, BDO middle storage tank temperature is usually regulated and controlled by circulating water, so that a certain amount of heat is wasted. During the production of PBAT, the gas quantity generated by the polycondensation kettle is large, and the oligomer entrained by gas phase easily enters into BDO circulating working solution of a liquid seal tank of a vacuum system, thereby influencing the performance of the vacuum system. Chinese patent CN2015200506850 discloses a BDO vacuum system for in PBT production, including the scraper blade condenser that communicates vacuum pump and polycondensation reaction unit respectively, the upper position is equipped with BDO spray set in the scraper blade condenser, and the liquid BDO export of scraper blade condenser bottom communicates buffer tank, BDO circulating pump, heat exchanger and BDO spray set in proper order through BDO circulating line, and the heat exchanger communicates cooling circulation water pipeline, and the inlet end that is close to circulating water pump on the cooling circulation water pipeline communicates main circulating water inlet tube, lies in main circulating water inlet tube upper position intercommunication main circulating water outlet pipe on the cooling circulation water pipeline. The temperature of the cooling circulating water flowing through the heat exchanger is regulated by introducing main circulating water with lower temperature, so that the purpose of accurately controlling the liquid BDO temperature in the BDO circulating pipeline to be 45+/-0.5 ℃ is achieved, and the system is stable in operation. In addition, to improve the quality of the sprayed BDO of the vacuum system, the replacement of BDO in the vacuum system liquid seal tank needs to be performed by BDO with higher quality (such as fresh BDO and refined BDO). If the BDO is replaced by fresh BDO, a certain difficulty exists in the whole BDO recycling, and if a BDO recycling unit for BDO recycling and refining is arranged, the production energy consumption is increased. Disclosure of Invention The invention aims to provide a BDO recycling device which reduces production energy consumption and improves the stability of a vacuum system. The invention also provides a method for recycling BDO. According to the technical scheme, the BDO recovery device in the PBAT production comprises a process tower and a BDO vacuum system, wherein a pipeline at the bottom of the process tower is divided into two paths after passing through a shielding pump, one path is connected with an intermediate BDO storage tank, the other path is connected with a BDO evaporator and a liquid seal tank of the BDO vacuum system through a heat exchanger to form a hot fluid path, a heat medium outlet of the heat exchanger is connected with the BDO evaporator and the liquid seal tank, a refrigerant inlet of the heat exchanger is connected with a BDO collecting tank of the BDO vacuum system, and a refrigerant outlet of the heat exchanger is connected with the process tower to form a cold fluid path. Preferably, the liquid seal tank is divided into a BDO liquid seal tank of a polycondensation spray system and a BDO liquid seal tank of a polycondensation spray system. Preferably, a filter is arranged at the inlet of the heat exchanger. Preferably, a hand valve, a regulating valve and a flowmeter are arranged on the pipeline. The working principle is that after being pressurized by the shielding pump at the bottom of the process tower, the hot fluid sequentially flows through the filter and the heat exchanger to be respectively connected with the BDO evaporator, the BDO liquid seal groove of the polycondensation spray system and the BDO liquid seal groove of the polycondensation spray system, so that the use amount of recycled BDO is effectively reduced, the coking phenomenon of the nozzle of the injection pump is reduced, the vacuum stability of the polycondensation system is improved, the fresh BDO replacement amount of the BDO evaporator, the BDO liquid seal groove of the polycondensation spray system and the BDO liquid seal g