A self-cleaning filtration device for self-polymers in hexafluoropropylene cracking gas

Abstract

This utility model discloses a self-cleaning filtration device for self-polymers in hexafluoropropylene cracking gas, relating to the field of hexafluoropropylene production technology. It includes a pre-filtration component, a buffer tank connected to the outlet of the pre-filtration component, an alumina filter connected to the outlet of the buffer tank, an aluminum fluoride filter connected to the outlet of the alumina filter, and a self-cleaning component housed within the pre-filtration component. It can intercept self-polymers online, preventing PTFE self-polymers from entering the alumina filter and causing blockage, and achieves self-cleaning, ensuring production continuity and thus improving the production efficiency of hexafluoropropylene (HFP).

Description

Technical Field

[0001] This utility model relates to the field of hexafluoropropylene production technology, specifically to a self-cleaning filtration device for self-polymers in hexafluoropropylene cracking gas. Background Technology

[0002] Hexafluoropropylene (HFP) is a key monomer in the preparation of fluorinated polymer materials, typically generated by the cracking of a mixture of tetrafluoroethylene (TFE) and octafluorocyclobutane (C-318) at high temperatures of 600℃-900℃. During the cracking reaction, in addition to the target product hexafluoropropylene, hydrogen fluoride (HF), polytetrafluoroethylene (PTFE) self-polymers, and octafluoroisobutylene (PFIB) are also produced. Hydrogen fluoride (HF) is highly corrosive and can corrode pipes and equipment, requiring filtration using an alumina filter.

[0003] In the existing process, the pyrolysis gas from the pyrolysis furnace passes through a dust collector to remove carbonized particles and a cooler to cool before directly entering the alumina filter. At this point, the pyrolysis gas contains some polytetrafluoroethylene (PTFE) self-polymers. These PTFE self-polymers clog the alumina filter, reducing the absorption and filtration efficiency of the alumina particles for hydrogen fluoride (HF) in the pyrolysis gas. This also hinders the smooth passage of the pyrolysis gas, thereby reducing the production efficiency of hexafluoropropylene (HFP). When the alumina filter becomes severely clogged, a shutdown for cleaning is required, causing production interruption. Utility Model Content

[0004] The purpose of this invention is to provide a self-cleaning filtration device for self-polymers in hexafluoropropylene cracking gas. This device can intercept self-polymers online, preventing polytetrafluoroethylene (PTFE) self-polymers from entering the alumina filter and causing blockage. It can also achieve self-cleaning, ensuring the continuity of production and thus improving the production efficiency of hexafluoropropylene (HFP).

[0005] The above-mentioned optimized structure of this utility model is achieved through the following technical solution: a self-cleaning filtration device for self-polymers in hexafluoropropylene cracking gas, including a pre-filtration component; A buffer tank, which is connected to the air outlet of the pre-filter assembly; An alumina filter is provided, which is connected to the air outlet of the buffer tank. An aluminum fluoride filter, wherein the aluminum fluoride filter is connected to the outlet of the alumina filter; A self-cleaning component is disposed within the pre-filter component.

[0006] In some embodiments, the pre-filtration assembly includes a first pre-filter, the outlet of which is connected to the buffer tank. The second pre-filter has its outlet connected to the buffer tank. A first control valve is connected to the air inlet of the first pre-filter; The second control valve is connected to the air inlet of the second pre-filter; A third control valve is located between the first pre-filter and the buffer tank; A fourth control valve is located between the second pre-filter and the buffer tank.

[0007] In some embodiments, the self-cleaning component includes a fifth control valve, one end of which is connected to the air inlet of both the first control valve and the first pre-filter. The sixth control valve has one end connected to the air inlet of both the second control valve and the second pre-filter, and the other end connected to the fifth control valve. The self-polymer removal device is connected to both the fifth control valve and the sixth control valve; The seventh control valve has one end connected to the air inlet of both the first control valve and the first pre-filter, and the other end connected to the air outlet of the self-polymer removal component. The eighth control valve has one end connected to the air inlet of the second control valve and the second pre-filter, and the other end connected to the air outlet of the seventh control valve and the self-polymer removal component.

[0008] In some embodiments, the self-polymer removal element is a cyclone separator.

[0009] In some embodiments, the self-cleaning assembly further includes a compressor, the air inlet of which is connected to the air outlet of the self-polymer removal component, and the air outlet is connected to both the seventh control valve and the eighth control valve.

[0010] In some embodiments, the first control valve, the second control valve, the third control valve, the fourth control valve, the fifth control valve, the sixth control valve, the seventh control valve, and the eighth control valve are all shut-off valves.

[0011] In summary, this utility model has the following beneficial effects: This invention, by adding a pre-filter component, can intercept PTFE self-polymers in the pyrolysis gas, preventing them from entering the alumina filter, thereby improving the alumina filter's absorption efficiency for HF and extending the alumina's service life. By adding a self-cleaning component, the device's own pyrolysis gas can be used for backflushing, enabling the pre-filter component to be cleaned during normal production. This avoids shutdowns due to cleaning self-polymers, ensuring continuous production. The compressor ensures that the pressure of the backflushing pyrolysis gas matches that of the main pipeline pyrolysis gas, preventing backflow of pyrolysis gas and unstable system pressure that could affect the stable operation of the device. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of this utility model.

[0013] In the diagram: 1. First pre-filter; 2. Buffer tank; 3. Alumina filter; 4. Aluminum fluoride filter; 5. Second pre-filter; 6. First control valve; 7. Second control valve; 8. Third control valve; 9. Fourth control valve; 10. Fifth control valve; 11. Sixth control valve; 12. Self-polymer removal device; 13. Seventh control valve; 14. Eighth control valve; 15. Compressor. Detailed Implementation

[0014] The technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0015] refer to Figure 1A self-cleaning filtration device for PTFE self-polymers in hexafluoropropylene cracking gas includes a pre-filtration component, a buffer tank 2, an alumina filter 3, an aluminum fluoride filter 4, and a self-cleaning component. The inlet of the pre-filtration component is connected to the main cracking gas pipeline. The pre-filtration component can intercept PTFE self-polymers in the cracking gas, preventing them from entering the alumina filter 3 with the cracking gas and causing blockage, thus requiring production shutdown for maintenance. The buffer tank 2 can be made of 316L stainless steel and is connected to the outlet of the pre-filtration component to stabilize the airflow of the cracking gas. The pressure is controlled by the alumina filter 3, which is connected to the outlet of the buffer tank 2. It can absorb hydrogen fluoride (HF) in the cracked gas, protecting pipelines and equipment. The aluminum fluoride filter 4 is connected to the outlet of the alumina filter 3. It can absorb the aluminum fluoride dust generated when the alumina absorbs HF in the alumina filter. The outlet can be connected to the subsequent HFP distillation system. The buffer tank 2, alumina filter 3, and aluminum fluoride filter 4 are all existing technologies and will not be described in detail here. The self-cleaning component is located in the pre-filter component and can be activated when needed to achieve self-cleaning of the pre-filter component.

[0016] In some embodiments, the pre-filtration assembly includes a first pre-filter 1, a second pre-filter 5, a first control valve 6, a second control valve 7, a third control valve 8, and a fourth control valve 9. The first pre-filter 1 may be a 316L stainless steel pressure vessel with a polytetrafluoroethylene pleated filter membrane inside. Its outlet can be connected to the inlet pipe of the buffer tank 2 via a flange. The structural parameters of the second pre-filter 5 are completely consistent with those of the first pre-filter 1, and they are arranged in parallel. Its outlet can also be connected to the inlet pipe of the buffer tank 2 via a flange. One end of the first control valve 6 can be connected to the main pipeline of the cracked gas via a flange, and the other end can be connected to the inlet of the first pre-filter 1 via a flange. One end of the second control valve 7 is connected to the main pipeline of the cracked gas, and the other end can be connected to the inlet of the second pre-filter 5 via a flange. The third control valve 8 is connected in series on the pipeline between the outlet of the first pre-filter 1 and the buffer tank 2. The fourth control valve 9 is connected in series on the pipeline between the outlet of the second pre-filter 5 and the buffer tank 2, and is symmetrically distributed with the third control valve 8.

[0017] The first control valve 6 and the third control valve 8 are open, and the second control valve 7 and the fourth control valve 9 are closed. The pyrolysis gas flows to the buffer tank 2 after passing through the first pre-filter 1. The first control valve 6 and the third control valve 8 are closed, and the second control valve 7 and the fourth control valve 9 are open. The pyrolysis gas flows to the buffer tank 2 after passing through the second pre-filter 5, forming a dual pre-filtration path. This path can be selected according to the actual situation to ensure the continuous production of hexafluoropropylene.

[0018] In some embodiments, the self-cleaning assembly includes a fifth control valve 10, a sixth control valve 11, a self-polymer removal component 12, a seventh control valve 13, and an eighth control valve 14. One end of the fifth control valve 10 is connected to the pipeline between the first control valve 6 and the first pre-filter 1 via a tee fitting, and the other end is connected to the air inlet of the self-polymer removal component 12 via a flange. One end of the sixth control valve 11 is connected to the pipeline between the second control valve 7 and the second pre-filter 5 via a tee fitting, and the other end is connected to the outlet pipeline of the fifth control valve 10. After the flow, they are connected to the main air inlet pipe of the self-polymer removal component 12. The air inlet of the self-polymer removal component 12 is connected to the manifold of the fifth control valve 10 and the sixth control valve 11. One end of the seventh control valve 13 is connected to the air inlet pipe of the first pre-filter 1 through a three-way fitting, and the other end is connected to the air outlet pipe of the self-polymer removal component 12. One end of the eighth control valve 14 is connected to the air inlet pipe of the second pre-filter 5 through a three-way fitting, and the other end is connected to the outlet pipe of the seventh control valve 13 and then connected to the main air outlet pipe of the self-polymer removal component 12.

[0019] In some embodiments, the self-polymer removal component 12 may be a cyclone separator, and a pneumatic discharge valve may be provided at the bottom to automatically discharge material once per hour, so as to remove the PTFE self-polymers intercepted during the production process.

[0020] In some embodiments, the self-cleaning assembly further includes a compressor 15, which may be a diaphragm compressor (discharge pressure 1.2 MPa, flow rate adjustable range 30-100 cubic meters per hour). Its inlet can be connected to the outlet pipe of the self-polymer removal component 12 via a flange, and the outlet is connected to the manifold of the seventh control valve 13 and the eighth control valve 14 via branch pipes, respectively. A pressure transmitter is provided on the pipeline. The compressor 15 can ensure that the pressure of the backflushing pyrolysis gas matches the pressure of the pyrolysis gas in the main pipeline, avoiding backflushing of pyrolysis gas and unstable system pressure, which would affect the stable operation of the device.

[0021] In some embodiments, the first control valve 6, the second control valve 7, the third control valve 8, the fourth control valve 9, the fifth control valve 10, the sixth control valve 11, the seventh control valve 13, and the eighth control valve 14 are all shut-off valves. The pneumatic shut-off valves have a response time of ≤1 second and a sealing rating of ANSI Class VI. The opening and closing of the first control valve 6, the second control valve 7, the third control valve 8, the fourth control valve 9, the fifth control valve 10, the sixth control valve 11, the seventh control valve 13, and the eighth control valve 14 can be controlled by a control system to achieve automatic switching control.

[0022] In some embodiments, a control system is also included. The control system is electrically connected to the first control valve 6, the second control valve 7, the third control valve 8, the fourth control valve 9, the fifth control valve 10, the sixth control valve 11, the seventh control valve 13, and the eighth control valve 14. Pressure drop sensors may be provided on the first pre-filter 1 and the second pre-filter 5. The pressure drop sensors can monitor the pressure difference between the inlet and outlet of the first pre-filter 1 and the second pre-filter 5 in real time and can be electrically connected to the control system. By sensing the pressure difference value fed back by the pressure drop sensors on the first pre-filter 1 and the second pre-filter 5, the control system determines its status and controls the opening and closing of each control valve according to actual needs to achieve automated control.

[0023] The specific working principle is as follows: Open the first control valve 6 and the third control valve 8, and close the second control valve 7, the fourth control valve 9, and all valves of the self-cleaning assembly. The pyrolysis gas containing HFP enters the first pre-filter 1 through the first control valve 6, intercepting PTFE self-polymers in the pyrolysis gas. The filtered gas then enters the buffer tank 2 through the third control valve 8 for flow stabilization, and then sequentially enters the alumina filter 3 and the aluminum fluoride filter 4, where hydrogen fluoride is deeply removed. When the pressure drop of the first pre-filter 1 rises to 0.1 MPa, the self-cleaning procedure is triggered.

[0024] The control system automatically opens the second control valve 7 and the fourth control valve 9. After the flow rate stabilizes for about 30 seconds, it closes the first control valve 6 and the third control valve 8. The pyrolysis gas is switched to the second pre-filter 5 for filtration, so that production can continue.

[0025] The third control valve 8, the fifth control valve 10, the eighth control valve 14, the self-polymer removal device 12, and the compressor 15 are opened. The pyrolysis gas purified by the second pre-filter 5 flows partly into the buffer tank 2 to produce hexafluoropropylene, and partly through the third control valve 8 to backflush from the rear end of the first pre-filter 1. The backflush airflow carries PTFE self-polymers through the fifth control valve 10 into the self-polymer removal device 12. More than 95% of the self-polymers are separated under centrifugal force and deposited at the bottom of the self-polymer removal device 12, and are periodically discharged through the discharge valve. A small amount of unseparated fine self-polymers enter the compressor 15 with the airflow, and after being pressurized, they flow through the eighth control valve 14 into the air inlet pipe of the second pre-filter 5, where they are intercepted again by the second pre-filter. After cleaning, the third control valve 8, the fifth control valve 10, the eighth control valve 14, the self-polymer removal device 12, and the compressor 15 are closed. The first pre-filter 1 is in standby mode and will be switched to be used when the second pre-filter 5 needs cleaning.

[0026] When the second pre-filter 5 needs cleaning, the first control valve 6 and the third control valve 8 are opened, and the second control valve 7 and the fourth control valve 9 are closed. The pyrolysis gas is switched to the first pre-filter 1 for filtration, enabling continuous production. Then, the fourth control valve 9, the sixth control valve 11, the seventh control valve 13, the self-polymer removal component 12, and the compressor 15 are opened to clean the second pre-filter 5.

[0027] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A self-cleaning filtration apparatus for homo-polymer in hexafluoropropene cracking gas, characterized by: Includes pre-filtering components; Buffer tank (2), the buffer tank (2) is connected to the air outlet of the pre-filter assembly; An alumina filter (3) is connected to the outlet of the buffer tank (2); An aluminum fluoride filter (4) is connected to the outlet of the alumina filter (3); A self-cleaning component is disposed within the pre-filter component.

2. A self-cleaning filter apparatus for self-polymer in hexafluoropropene cracking gas according to claim 1, characterized in that: The pre-filtration assembly includes a first pre-filter (1), the outlet of which is connected to the buffer tank (2); The second pre-filter (5) has its outlet connected to the buffer tank (2); The first control valve (6) is connected to the air inlet of the first pre-filter (1); The second control valve (7) is connected to the air inlet of the second pre-filter (5); The third control valve (8) is located between the first pre-filter (1) and the buffer tank (2); The fourth control valve (9) is located between the second pre-filter (5) and the buffer tank (2).

3. The self-cleaning filtration device for self-polymers in hexafluoropropylene cracking gas according to claim 2, characterized in that: The self-cleaning component includes a fifth control valve (10), one end of which is connected to the air inlet of the first control valve (6) and the first pre-filter (1); The sixth control valve (11) is connected at one end to the air inlet of the second control valve (7) and the second pre-filter (5), and at the other end to the fifth control valve (10). Self-polymer removal component (12), which is connected to both the fifth control valve (10) and the sixth control valve (11); The seventh control valve (13) is connected at one end to the air inlet of the first control valve (6) and the first pre-filter (1), and at the other end to the air outlet of the self-polymer removal component (12). The eighth control valve (14) is connected at one end to the air inlet of the second control valve (7) and the second pre-filter (5), and at the other end to the air outlet of the seventh control valve (13) and the self-polymer removal component (12).

4. A self-cleaning filter apparatus for self-polymer in hexafluoropropene cracking gas according to claim 3, characterized in that: The self-polymer removal component (12) is a cyclone separator.

5. A self-cleaning filter apparatus for self-polymer in hexafluoropropene cracking gas according to claim 3, characterized in that: The self-cleaning component also includes a compressor (15), the air inlet of which is connected to the air outlet of the self-polymer removal component (12), and the air outlet is connected to both the seventh control valve (13) and the eighth control valve (14).

6. The self-cleaning filtration device for self-polymers in hexafluoropropylene cracking gas according to claim 3, characterized in that: The first control valve (6), the second control valve (7), the third control valve (8), the fourth control valve (9), the fifth control valve (10), the sixth control valve (11), the seventh control valve (13), and the eighth control valve (14) are all shut-off valves.

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