EG (ethylene glycol) recycling device in PET (polyethylene terephthalate) production

Abstract

The utility model discloses an EG (ethylene glycol) recycling device in PET (polyethylene terephthalate) production, which comprises a membrane tank, an aeration tank, a membrane frame and a hollow fiber membrane, the aeration tank and the membrane frame are both positioned inside the membrane tank, the hollow fiber membrane is mounted on the membrane frame, one end of the membrane tank is connected with a fan through a pipeline, and the other end of the membrane tank is connected with a water pump through a pipeline. The other end of the membrane tank is sequentially connected with a water production mechanism, a backwashing mechanism, a discharge mechanism, a precipitation mechanism and a discharge pipe through a plurality of pipelines, the discharge pipe is respectively communicated with the water production mechanism, the backwashing mechanism and the precipitation mechanism, a discharge valve is arranged on the discharge pipe, and the precipitation mechanism comprises a precipitation tank; the first emptying valve is connected with the sedimentation tank through a pipeline, the sedimentation tank is connected with a sedimentation liquid outlet pump through a pipeline, and the sedimentation liquid outlet pump is communicated with the discharge pipe through a pipeline. And the settling pond is arranged, so that the effect of settling a solution can be achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of polyester production equipment, in particular to an EG recycling device in PET production. Background Art

[0002] Ethylene glycol (EG) is an important chemical raw material and strategic material with a wide range of downstream uses. EG can react with terephthalic acid (PTA) to produce polyethylene terephthalate, also known as polyester (PET). About 95% of EG materials in my country are used in the PET production field, mainly used to make PET polyester, PET resin, film, beverage bottles, etc.

[0003] The reaction temperature of EG and PTA (above 260°C) is much higher than the boiling point of EG (197.3°C). A large amount of EG volatilizes during this production process, which takes away many PTA and small molecular products in the reaction. After cooling, a mixed solution of EG and solid is formed. The solid content in the solution ranges from 0.1wt% to 1wt%, resulting in a turbid state of the recycled EG solution. Direct polymerization and recycling may have a certain impact on the quality of PET polymer.

[0004] In view of the production defects of reuse caused by the mixing of PTA and small molecule products into EG as a raw material during the volatilization and condensation process, the existing EG solution is mostly reused after filtering, but the filter precision is not high, and the filter needs to be manually removed, cleaned and replaced frequently. Another method is to use a distillation tower to separate impurities by distillation. Although this method can purify EG, the process equipment of the distillation process is relatively complicated, which not only consumes a lot of heat, water vapor, etc., but also consumes a lot of energy. It also needs to build large-scale equipment such as distillation towers, which has high investment costs and low cost performance.

[0005] CN219259652U discloses a membrane filtration device, but this device has some problems. During operation, the solid content in the membrane pool will gradually increase, so it is necessary to regularly discharge the EG solution in the membrane pool, which leads to a waste of EG. In order to reduce the number of times the EG solution is emptied, it will only be emptied when the solid content in the membrane pool reaches a high concentration, which will cause solid particles to accumulate on the hollow fiber membrane, easily causing the hollow fiber membrane to be blocked. In order to solve the above problems, a solution is proposed below. Utility Model Content

[0006] The utility model aims to provide an EG recycling device in PET production, which has the advantages of filtering mixed solid particles and reducing EG discharge.

[0007] The above technical objectives of the utility model are achieved through the following technical solutions:

[0008] A device for recycling EG in PET production comprises a membrane pool, an aeration tank, a membrane frame and a hollow fiber membrane, wherein the aeration tank and the membrane frame are both located inside the membrane pool, the hollow fiber membrane is installed on the membrane frame, one end of the membrane pool is connected to a fan via a pipeline, the other end of the membrane pool is sequentially connected to a water production mechanism, a backwashing mechanism, a discharge mechanism, a sedimentation mechanism and a discharge pipe via a plurality of pipelines, the discharge pipe is respectively connected to the water production mechanism, the backwashing mechanism and the sedimentation mechanism and a discharge valve is arranged on the discharge pipe, the sedimentation mechanism comprises a sedimentation tank, the drain valve is connected to the sedimentation tank via a pipeline, the sedimentation tank is connected to a sedimentation liquid pump via a pipeline, and the sedimentation liquid pump is connected to the discharge pipe via a pipeline.

[0009] Preferably, the water production mechanism comprises a water production pump, the water production pump is connected to the membrane pool via a pipeline, a water production valve is provided on the pipeline, the water production pump is connected to a water production pipe, and the water production pipe is connected to a discharge pipe.

[0010] Preferably, the backwash mechanism includes a backwash pump, a backwash pipe is connected between the backwash pump and the water production pipe, a backwash valve is provided on the backwash pipe, the backwash pump is connected to a backwash bucket through a pipeline, the backwash bucket is connected to a water inlet pipe, the water inlet pipe is connected to the discharge pipe and a backwash bucket water inlet valve is provided on the water inlet pipe.

[0011] Preferably, the discharge mechanism comprises an emptying pump, one end of which is connected to the membrane pool via a pipeline, a drain valve is installed on the pipeline, and the other end of the emptying pump is connected to an emptying pipe, which is connected to the sedimentation tank.

[0012] Preferably, a sedimentation liquid outlet valve is provided on the pipeline between the sedimentation liquid outlet pump and the discharge pipe, and a drain pipe is connected to the bottom end of the sedimentation tank, and a sedimentation drain valve is provided on the drain pipe.

[0013] The beneficial effects of the utility model are as follows: the mixed solution in the membrane pool can be discharged into the sedimentation tank through the setting of the discharge mechanism, the setting of the sedimentation tank can play the role of precipitating the solution, and the setting of the sedimentation liquid outlet valve and the sedimentation liquid outlet pump can firstly discharge the purified solution into the discharge pipe, and then flow into the existing PET production area, and the solids precipitated at the bottom of the sedimentation tank can be discharged through the cooperation of the sedimentation emptying valve and the emptying pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of an embodiment.

[0015] Figure numerals: 1. membrane pool; 2. hollow fiber membrane; 3. fan; 4. aeration tank; 5. water production valve; 6. water production pump; 7. water production pipe; 8. discharge valve; 81. discharge pipe; 9. backwash tank inlet valve; 10. backwash tank; 101. water inlet pipe; 11. backwash pump; 12. backwash valve; 13. drain valve 1; 14. drain pump; 15. sedimentation tank; 16. sedimentation liquid pump; 17. sedimentation liquid valve; 18. sedimentation drain valve; 181. drain pipe. DETAILED DESCRIPTION

[0016] The following is only a preferred embodiment of the present invention, and the protection scope is not limited to this embodiment. All technical solutions under the concept of the present invention should belong to the protection scope of the present invention. The same parts are represented by the same figure marks. It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings, and the words "bottom" and "top", "inside" and "outside" refer to the directions toward or away from the geometric center of a specific component, respectively.

[0017] like Figure 1 As shown, an EG recycling device in PET production includes an existing membrane pool 1, an aeration tank 4, a membrane frame and a hollow fiber membrane 2. The aeration tank 4 and the membrane frame are both located inside the membrane pool 1, and the hollow fiber membrane 2 is installed on the membrane frame; one end of the membrane pool 1 is connected to a fan 3 through a pipeline, and the membrane pool 1 can be cooled by the setting of the fan 3, thereby improving the cooling effect. The membrane pool 1 is in an aerated state by the setting of the aeration tank 4, and the membrane frame and the hollow fiber membrane 2 are both in an aerated state, so as to produce water, backwash and clean.

[0018] The other end of the membrane pool 1 is connected to a water production mechanism, a backwash mechanism, a discharge mechanism, a sedimentation mechanism and a discharge pipe 81 in sequence through a number of pipes. The discharge pipe 81 is respectively connected to the water production mechanism, the backwash mechanism and the sedimentation mechanism and a discharge valve 8 is provided on the discharge pipe 81. The water production mechanism includes a water production pump 6. The water production pump 6 is connected to the membrane pool 1 through a pipe. A water production valve 5 is provided on the pipe. The water production pump 6 is connected to a water production pipe 7, and the water production pipe 7 is connected to the discharge pipe 81.

[0019] The backwash mechanism includes a backwash pump 11, a backwash pipe is connected between the backwash pump 11 and the water production pipe 7, a backwash valve 12 is arranged on the backwash pipe, the backwash pump 11 is connected to the backwash bucket 10 through a pipeline, the backwash bucket 10 is connected to the water inlet pipe 101, the water inlet pipe 101 is connected to the discharge pipe 81 and the water inlet valve 9 of the backwash bucket 10 is arranged on the water inlet pipe 101.

[0020] The discharge mechanism includes an emptying pump 14, one end of which is connected to the membrane pool 1 through a pipeline, and an emptying valve 13 is installed on the pipeline. The other end of the emptying pump 14 is connected to an emptying pipe 181, and the emptying pipe 181 is connected to the sedimentation tank 15.

[0021] The sedimentation mechanism includes a sedimentation tank 15, a drain valve 13 connected to the sedimentation tank 15 through a pipeline, the sedimentation tank 15 is connected to a sedimentation liquid pump 16 through a pipeline, the sedimentation liquid pump 16 is connected to a discharge pipe 81 through a pipeline, a sedimentation liquid valve 17 is arranged on the pipeline between the sedimentation liquid pump 16 and the discharge pipe 81, the bottom end of the sedimentation tank 15 is connected to a drain pipe 181, and a sedimentation drain valve 18 is arranged on the drain pipe 181. All the above valves can be controlled to switch by an existing PLC controller.

[0022] In the filtration mode, all pumps and valves are closed by default at the beginning. When the solid-liquid mixed EG solution enters the membrane pool 1, the hollow fiber membrane 2 can filter the EG solution. After the filtrate passes through the water production valve 5 and the water production pump 6, the liquid level of the backwash tank 10 is fed back through the existing liquid level meter. When the backwash tank 10 is at a low level, the backwash tank 10 inlet valve 9 can be opened through the existing PLC controller, and the filtrate enters the backwash tank 10 until the backwash tank 10 reaches a high level, and then the discharge valve 8 is opened. The filtrate can enter the existing PET reaction area through the discharge valve 8 and run for 8 minutes, and the water production pump 6 is closed for 2 minutes. This is 1 cycle.

[0023] After a fixed period of water production operation, the backwash mode can be entered. Through the existing PLC controller, the water production pump 6 and the water outlet valve can be closed in sequence, and then the backwash valve 12 and the backwash pump 11 can be opened respectively. After running for a period of time, the backwash pump 11 and the backwash valve 12 are closed again, and then the water outlet valve and the water production pump 6 are opened again, and the above-mentioned filtration mode can be entered again.

[0024] After running for a period of time, when the solid content of the solution in the membrane pool 1 increases and becomes milky white, the discharge mode can be entered. During discharge, the existing PLC controller can first close all pumps and valves, and then open the drain valve and the drain pump 14 in turn. The drain pump 14 can pump the solution in the membrane pool 1 into the sedimentation tank 15 and enter the sedimentation mode. Thereafter, the new solid-liquid mixed EG solution is introduced into the membrane pool 1. When the EG solution reaches the set starting liquid level, the above-mentioned filtration mode is entered again.

[0025] In the sedimentation mode, when the solution is discharged into the sedimentation tank 15 and left to settle for a few days, the sedimentation tank 15 can play a role in sedimentation and purification. The sedimentation liquid outlet valve 17 and the sedimentation liquid outlet pump 16 can be opened respectively through the PLC controller to discharge the purified clear liquid into the discharge pipe 81 until it flows into the PET production area.

[0026] When it is necessary to drain the solids in the sedimentation tank 15, the sedimentation liquid pump 16 and the sedimentation liquid valve 17 can be closed in sequence through the PLC controller, and then the sedimentation emptying valve 18 can be opened to discharge the remaining solids in the sedimentation tank 15 from the emptying pipe 181. After emptying, the sedimentation emptying valve 18 can be closed.

[0027] The specific embodiments described above further illustrate the technical problems, technical solutions and beneficial effects solved by the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for recycling EG in PET production, comprising a membrane tank (1), an aeration tank (4), a membrane frame and a hollow fiber membrane (2), characterized in that: The aeration tank (4) and the membrane frame are both located inside the membrane pool (1), the hollow fiber membrane (2) is installed on the membrane frame, one end of the membrane pool (1) is connected to a fan (3) via a pipeline, and the other end of the membrane pool (1) is connected to a water production mechanism, a backwashing mechanism, a discharge mechanism, a sedimentation mechanism and a discharge pipe (81) in sequence via a plurality of pipelines, the discharge pipe (81) is respectively connected to the water production mechanism, the backwashing mechanism and the sedimentation mechanism, and a discharge valve (8) is provided on the discharge pipe (81), the sedimentation mechanism comprises a sedimentation tank (15), the sedimentation tank (15) is connected to a sedimentation liquid pump (16) via a pipeline, and the sedimentation liquid pump (16) is connected to the discharge pipe (81) via a pipeline.

2. The EG recycling device in PET production according to claim 1, characterized in that: The water production mechanism comprises a water production pump (6), the water production pump (6) is connected to the membrane pool (1) via a pipeline, a water production valve (5) is provided on the pipeline, the water production pump (6) is connected to a water production pipe (7), and the water production pipe (7) is connected to a discharge pipe (81).

3. The EG recycling device in PET production according to claim 2, characterized in that: The backwash mechanism comprises a backwash pump (11), a backwash pipe is connected between the backwash pump (11) and the water production pipe (7), a backwash valve (12) is arranged on the backwash pipe, the backwash pump (11) is connected to the backwash bucket (10) through a pipeline, the backwash bucket (10) is connected to a water inlet pipe (101), the water inlet pipe (101) is connected to the discharge pipe (81), and a backwash bucket (10) water inlet valve (9) is arranged on the water inlet pipe (101).

4. The EG recycling device in PET production according to claim 1, characterized in that: The discharge mechanism comprises an emptying pump (14), one end of which is connected to the membrane tank (1) via a pipeline, an emptying valve (13) is installed on the pipeline, and the emptying valve (13) is connected to the sedimentation tank (15) via a pipeline, and the other end of the emptying pump (14) is connected to an emptying pipe (181), and the emptying pipe (181) is connected to the sedimentation tank (15).

5. The EG recycling device in PET production according to claim 1, characterized in that: A sedimentation liquid outlet valve (17) is provided on the pipeline between the sedimentation liquid outlet pump (16) and the discharge pipe (81), and a drain pipe (181) is connected to the bottom end of the sedimentation tank (15), and a sedimentation drain valve (18) is provided on the drain pipe (181).

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