TFE feeding device of FEP polymerization system

Abstract

A TFE feeding device of an FEP polymerization system comprises a plurality of first monomer collecting tanks and a plurality of second monomer collecting tanks, the top of each monomer collecting tank is provided with a feeding port, a discharging port and a replacement port, the feeding ports of the monomer collecting tanks are connected in parallel and connected with a TFE source through a monomer condenser, the discharging ports of the monomer collecting tanks are connected in parallel, and the replacement port is connected with the TFE source through a replacement port. The top of each batching tank is provided with a negative pressure port, and the negative pressure ports are connected with the inlets of the corresponding batching tanks through a first circulating compression pump and a second circulating compression pump respectively; the balance distribution tank is connected with the replacement ports of the first monomer collecting tank and the second monomer collecting tank through a first pipeline and a second pipeline respectively, the balance distribution tank is further provided with a first negative pressure pipe and a second negative pressure pipe which are connected with the feeding ends of the second circulating compression pump and the first circulating compression pump, and the first negative pressure pipe and the second negative pressure pipe are both provided with valves. The device is simple in structure and low in transformation cost, the utilization rate of TFE can be effectively increased, and the requirement for efficient maintenance of the FEP polymerization system is met.

Description

Technical Field

[0001] The present invention relates to the chemical industry field, and particularly relates to a TFE feeding device for an FEP polymerization system. Background Art

[0002] Chemical enterprises are equipped with at least two sets of FEP polymerization systems. All of the at least two sets of polymerization systems adopt the emulsion dispersion polymerization process, using TFE (tetrafluoroethylene) and HFP (hexafluoropropylene) as raw materials, adding additives such as initiators and surfactants, and carrying out batch polymerization reactions to produce FEP (perfluoroethylene propylene).

[0003] The TFE raw material is flammable and explosive. After being discharged from the TFE device, it is first condensed to a liquid phase at about -30°C by a monomer condenser, and then sent to multiple monomer collection tanks. After weighing, it is intermittently discharged to the vaporization process. After vaporization, it is sent to a static mixer to be mixed with vaporized HFP and then sent to a batching tank as a raw material for use in a polymerization kettle. The shell sides of the monomer condenser and the monomer collection tanks are all filled with -32°C cold brine, and its function is to condense the monomer tetrafluoroethylene (TFE) and maintain it at a liquid phase of about -30°C.

[0004] When the polymerization system is shut down for maintenance or due to an emergency failure, and each monomer collection tank needs to be shut down and replaced, since TFE cannot be recycled and stored, it can only be vented. TFE is flammable and explosive, and direct replacement and venting pose a safety hazard and cause venting losses. In addition, during the annual system overhaul, in order to reduce venting losses, usually the cold brine on the shell side of the monomer collection tank is shut down in advance, and the temperature of the shell side of the monomer collection tank (-32°C) gradually rises through heat exchange with the ambient temperature, so that the liquid-phase TFE in the monomer collection tank is directly recycled to the static mixer. The overall heating time is long (the temperature reaches about 10°C after 48 hours), which affects the maintenance plan.

[0005] Therefore, how to design a TFE feeding device that can effectively improve the utilization rate of TFE and adapt to the maintenance of the TFE polymerization system is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of the present invention is to provide a TFE feeding device for an FEP polymerization system in view of the deficiencies of the prior art. The device has a simple structure and low transformation cost, can effectively improve the utilization rate of TFE, and meet the requirements of efficient maintenance of the FEP polymerization system.

[0007] The technical solution of the present invention is: a TFE feeding device for an FEP polymerization system, including a number of first monomer collecting tanks and a number of second monomer collecting tanks. At the top of each monomer collecting tank, there are a feed inlet, a discharge outlet, and a replacement port, and valves are provided at the feed inlet, the discharge outlet, and the replacement port. The feed inlets of a number of first monomer collecting tanks are connected in parallel and are connected to the TFE source through a first monomer condenser. The feed inlets of a number of second monomer collecting tanks are connected in parallel and are connected to the TFE source through a second monomer condenser. The discharge outlets of a number of first monomer collecting tanks are connected in parallel and supply materials to a number of first batching tanks through a first vaporizer and a first static mixer. The discharge outlets of a number of second monomer collecting tanks are connected in parallel and supply materials to a number of second batching tanks through a second vaporizer and a second static mixer. It is characterized in that: it further includes a balance distribution tank. At the top of each of the first batching tanks and the second batching tanks, there is a negative pressure port and a valve are provided, and they are respectively connected to the inlets of each of the first batching tanks through a first circulation compression pump and to the inlets of each of the second batching tanks through a second circulation compression pump. The balance distribution tank is connected to the replacement ports of each of the first monomer collecting tanks through a first pipeline and to the replacement ports of each of the second monomer collecting tanks through a second pipeline. A first negative pressure pipe is further provided on the balance distribution tank and is connected to the feed end of the second circulation compression pump, and a second negative pressure pipe is provided and is connected to the feed end of the first circulation compression pump. Valves are provided on both the first negative pressure pipe and the second negative pressure pipe.

[0008] Two valves are provided on the refrigerant inlet pipe of each of the first monomer collecting tanks and the second monomer collecting tanks, and two valves are provided on the refrigerant outlet pipe. A hot water inlet pipe is provided between the two valves of the refrigerant inlet pipe and is connected to a 30°C salt water source. A hot water outlet pipe is provided between the two valves of the refrigerant outlet pipe. Valves are provided on both the hot water inlet pipe and the hot water outlet pipe.

[0009] A nitrogen pipe is further provided on the balance distribution tank and is connected to a nitrogen source, and a valve is provided on this nitrogen pipe.

[0010] A drain valve is provided at the bottom of the balance distribution tank.

[0011] Adopting the above technical solution has the following beneficial effects:

[0012] 1. The TFE feeding device of the FEP polymerization system includes a number of first monomer collection tanks and a number of second monomer collection tanks. Both the first monomer collection tanks and the second monomer collection tanks are used to temporarily store the liquid-phase TFE raw materials and are respectively corresponding to the supporting FEP polymerization systems. At the top of each monomer collection tank, there are a feed inlet, a discharge outlet, and a replacement port, and valves are provided at the feed inlet, the discharge outlet, and the replacement port. That is to say, the opening and closing of the feed inlet, the discharge outlet, and the replacement port of each monomer collection tank can be controlled by valves. The feed inlets of a number of first monomer collection tanks are connected in parallel and are connected to the TFE source through the first monomer condenser. The feed inlets of a number of second monomer collection tanks are connected in parallel and are connected to the TFE source through the second monomer condenser. That is to say, after the TFE raw material is cooled and liquefied, it can be sent to the corresponding monomer collection tank respectively, and a specific quantity of the raw material is weighed and measured. The discharge outlets of a number of first monomer collection tanks are connected in parallel and supply materials to a number of first batching tanks through the first vaporizer and the first static mixer. The discharge outlets of a number of second monomer collection tanks are connected in parallel and supply materials to a number of second batching tanks through the second vaporizer and the second static mixer. That is to say, by opening the corresponding valves, a certain quantity of TFE is vaporized through the vaporizer and mixed with other raw materials (such as HFP), and then sent to the batching tank for batching as polymerization raw materials. It also includes a balance distribution tank. At the top of each of the first batching tanks and the second batching tanks, there is a negative pressure port with a valve, and they are respectively connected to the inlets of the first batching tanks through the first circulation compression pump and to the inlets of the second batching tanks through the second circulation compression pump. That is to say, the polymerization raw materials in the batching tank can be pressurized by the corresponding circulation compression pump. The balance distribution tank is connected to the replacement ports of each first monomer collection tank through the first pipeline and to the replacement ports of each second monomer collection tank through the second pipeline. A first negative pressure pipe is also provided on the balance distribution tank and is connected to the feed end of the second circulation compression pump, and a second negative pressure pipe is provided and is connected to the feed end of the first circulation compression pump. Valves are provided on both the first negative pressure pipe and the second negative pressure pipe. When it is necessary to stop and overhaul any set of FEP polymerization systems, the pipeline, the negative pressure pipe, and the corresponding circulation compression pump can be connected through the valve, so that the TFE monomer collection tank under repair is in a negative pressure state, and it is sent to the operating circulation compression pump through the pipeline and the negative pressure pipe as raw materials to be pressurized and transported to the operating batching tank for use as raw materials, avoiding the harm caused by FEP venting.

[0013] 2. Two valves are provided on the refrigerant inlet pipe of each of the first monomer collection tanks and the second monomer collection tanks, and two valves are provided on the refrigerant outlet pipe. A hot water inlet pipe is provided between the two valves of the refrigerant inlet pipe and is connected to the 30°C salt water source. A hot water outlet pipe is provided between the two valves of the refrigerant outlet pipe. Valves are provided on both the hot water inlet pipe and the hot water outlet pipe. The TFE monomer collection tank under repair can be switched to a heat medium, greatly improving the discharging speed of TFE in the TFE monomer collection tank under repair and ensuring the normal progress of the overhaul.

[0014] 3. A nitrogen pipe connected to a nitrogen source is also provided on the balance distribution tank. A valve is provided on the nitrogen pipe. Nitrogen is injected into each TFE monomer collection tank and batching tank through the balance distribution tank to meet the actual requirements. Moreover, the nitrogen pipes provided on the tops of each monomer collection tank can be cancelled, which can not only reduce costs but also improve the safety of the system.

[0015] The following is a further description in conjunction with the drawings and specific embodiments. Description of the Drawings

[0016] Figure 1 It is a connection schematic diagram of the present invention;

[0017] Figure 2 is Figure 1 the enlarged view at M in

[0018] In the drawings, 1 is the first monomer collection tank, 2 is the second monomer collection tank, 3 is the feed port, 4 is the discharge port, 5 is the replacement port, 6 is the first monomer condenser, 7 is the second monomer condenser, 8 is the first vaporizer, 9 is the first static mixer, 10 is the first batching tank, 11 is the second vaporizer, 12 is the second static mixer, 13 is the second batching tank, 14 is the balance distribution tank, 15 is the negative pressure port, 16 is the first circulation compression pump, 17 is the second circulation compression pump, 18 is the first pipeline, 19 is the second pipeline, 20 is the first negative pressure pipe, 21 is the second negative pressure pipe, 22 is the hot water inlet pipe, 23 is the hot water outlet pipe, 24 is the nitrogen pipe, and 25 is the drain valve. Specific Embodiments

[0019] See Figure 1 and Figure 2, which is a specific embodiment of a TFE feeding device for an FEP polymerization system. The TFE feeding device of the FEP polymerization system includes several first monomer collection tanks 1 and several second monomer collection tanks 2. Specifically, the number of the first monomer collection tanks is two, and the number of the second monomer collection tanks is three, belonging to two sets of FEP polymerization systems respectively. Obviously, the monomer collection tanks are provided with heat exchange interlayers. Two valves are provided on the refrigerant inlet pipes of the heat exchange interlayers of each first monomer collection tank 1 and second monomer collection tank 2, and two valves are provided on the refrigerant outlet pipes. A hot water inlet pipe 22 is provided between the two valves of the refrigerant inlet pipe, which is connected to a 30°C salt water source. A hot water outlet pipe 23 is provided between the two valves of the refrigerant outlet pipe. Valves are provided on both the hot water inlet pipe 22 and the hot water outlet pipe 23. Feed inlets 3, discharge outlets 4, and replacement ports 5 are provided at the tops of each monomer collection tank, and valves are provided on the feed inlets 3, discharge outlets 4, and replacement ports 5. The feed inlets of the two first monomer collection tanks 1 are connected in parallel and are connected to the TFE source through a first monomer condenser 6. The feed inlets of the three second monomer collection tanks 2 are connected in parallel and are connected to the TFE source through a second monomer condenser 7. The discharge outlets of the two first monomer collection tanks 1 are connected in parallel and supply materials to four first batching tanks 10 through a first vaporizer 8 and a first static mixer 9. The discharge outlets of the three second monomer collection tanks 2 are connected in parallel and supply materials to four second batching tanks 13 through a second vaporizer 11 and a second static mixer 12. It also includes a balance distribution tank 14. A drain valve 25 is provided at the bottom of the balance distribution tank, and a nitrogen pipe 24 is provided at the top and is connected to a nitrogen source. A valve is provided on the nitrogen pipe 24. Negative pressure ports 15 are provided at the tops of each of the first batching tanks 10 and second batching tanks 13 and valves are provided. They are respectively connected to the inlets of each first batching tank 10 through a first circulating compression pump 16 and to the inlets of each second batching tank 13 through a second circulating compression pump 17. The balance distribution tank 14 is connected to the replacement ports of each first monomer collection tank 1 through a first pipeline 18 and to the replacement ports of each second monomer collection tank 2 through a second pipeline 19. A first negative pressure pipe 20 is also provided on the balance distribution tank and is connected to the feed end of the second circulating compression pump 17, and a second negative pressure pipe 21 is provided and is connected to the feed end of the first circulating compression pump 16. Valves are provided on both the first negative pressure pipe 20 and the second negative pressure pipe 21.

[0020] The working principle of the present invention is as follows: The FEP polymerization process is a batch process. Under normal circumstances, TFE is condensed into a liquid state by the first monomer condenser and the second monomer condenser respectively, and then sent to the corresponding first monomer collection tank and the second monomer collection tank, and remains in a liquid state. After reaching a certain weight, the addition is stopped. The valves at the discharge ports of the specific first monomer collection tank and the second monomer collection tank are opened, and after vaporization by the corresponding first vaporizer and the second vaporizer, they are sent to the corresponding first static mixer and the second static mixer (specific weights of HFP are also added to the first static mixer and the second static mixer respectively). The mixed vapor-phase raw materials are sent to the corresponding first batching tank and the second batching tank, and additives are added, and then sent to the FEP polymerization kettle.

[0021] When shutdown maintenance is required, taking the shutdown maintenance of the left FEP polymerization system as an example: Close the valves of the left FEP polymerization system, and stop the feeding, discharging, and process medium. There is residual liquid-phase TFE in each first monomer collection tank. When it is necessary to quickly clean the TFE in a specific first monomer collection tank, open the valve at the replacement port at the top of the collection tank, the valve on the first negative pressure pipe, the valve on the hot water inlet pipe, and the valve on the hot water outlet pipe, so that the collection tank is quickly heated up, and the second circulation compression pump in operation draws a negative pressure, so that the TFE in the collection tank is vaporized and sent to the corresponding second batching tank for use as a raw material after pressurization.

[0022] Verified by the applicant, with the feeding device of the present invention, the shutdown maintenance preparation time is shortened from the traditional 48H to about 8H.

Claims

1. A TFE feeding device for an FEP polymerization system, comprising a plurality of first monomer collection tanks (1) and a plurality of second monomer collection tanks (2). Each monomer collection tank is provided with a feed inlet (3), a discharge outlet (4), and a displacement port (5) at the top, and valves are provided at the feed inlet (3), the discharge outlet (4), and the displacement port (5). The feed inlets of the plurality of first monomer collection tanks (1) are connected in parallel and are connected to a TFE source via a first monomer condenser (6). The feed inlets of the plurality of second monomer collection tanks (2) are connected in parallel and are connected to the TFE source via a second monomer condenser (7). The discharge outlets of the plurality of first monomer collection tanks (1) are connected in parallel and supply materials to a plurality of first batching tanks (10) via a first vaporizer (8) and a first static mixer (9). The discharge outlets of the plurality of second monomer collection tanks (2) are connected in parallel and supply materials to a plurality of second batching tanks (13) via a second vaporizer (11) and a second static mixer (12). It is characterized in that: It further includes a balance distribution tank (14). Negative pressure ports (15) are provided at the tops of the first batching tanks (10) and the second batching tanks (13), and valves are provided. They are respectively connected to the inlets of the first batching tanks (10) through the first circulating compression pumps (16) and to the inlets of the second batching tanks (13) through the second circulating compression pumps (17). The balance distribution tank (14) is connected to the replacement ports of the first monomer collection tanks (1) through the first pipeline (18) and to the replacement ports of the second monomer collection tanks (2) through the second pipeline (19). A first negative pressure pipe (20) is further provided on the balance distribution tank (14) and is connected to the feed end of the second circulating compression pump (17), and a second negative pressure pipe (21) is provided and is connected to the feed end of the first circulating compression pump (16). Valves are provided on both the first negative pressure pipe (20) and the second negative pressure pipe (21).

2. The TFE feeding device of the FEP polymerization system according to claim 1, characterized in that: Two valves are provided on the refrigerant inlet pipes of the first monomer collection tanks (1) and the second monomer collection tanks (2), and two valves are provided on the refrigerant outlet pipes. A hot water inlet pipe (22) is provided between the two valves of the refrigerant inlet pipe and is connected to a 30°C salt water source. A hot water outlet pipe (23) is provided between the two valves of the refrigerant outlet pipe. Valves are provided on both the hot water inlet pipe (22) and the hot water outlet pipe (23).

3. The TFE feeding device of the FEP polymerization system according to claim 1, characterized in that: A nitrogen pipe (24) is further provided on the balance distribution tank (14) and is connected to a nitrogen source, and a valve is provided on the nitrogen pipe (24).

4. The TFE feeding device of the FEP polymerization system according to claim 1, characterized in that: A drain valve (25) is provided at the bottom of the balance distribution tank (14).

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