A leak monitoring system for vinylidene fluoride condensation

Abstract

This utility model discloses a leak monitoring system for vinylidene fluoride condensation, belonging to the field of leak monitoring technology for direct cooling equipment. It includes a shell-and-tube condenser and a controller. The tube-side inlet of the condenser is connected to a separation tower, the tube-side outlet is connected to a recovery tank via a gas supply pipe, and the tube-side drain port is connected to a storage tank via a liquid supply pipe. The shell-side inlet and outlet are connected to a refrigerant input pipe and a refrigerant output pipe, respectively. The shell-and-tube condenser is equipped with a pressure sensor and a temperature sensor. The refrigerant input pipe, refrigerant output pipe, tube-side inlet, and liquid supply pipe are each equipped with a first, second, third, and fourth electrically controlled valves, respectively, electrically connected to the controller. A branch pipe connects the shell-and-tube condenser to the recovery tank, and the branch pipe is equipped with a fifth electrically controlled valve, electrically connected to the controller. This utility model significantly reduces the safety risks caused by refrigerant leakage by combining real-time monitoring with rapid venting and pressure reduction.

Description

Technical Field

[0001] This utility model belongs to the field of leakage monitoring technology for direct cooling equipment, and specifically relates to a leakage monitoring system for vinylidene fluoride condensation. Background Technology

[0002] In the industrial production process of vinylidene fluoride (VDF), VDF gas is first generated through a cracking reaction, and then condensed into liquid using a direct cooling process for subsequent collection, purification, and storage. Because VDF gas has an extremely low boiling point (approximately -82°C), its condensation process relies on a low-temperature refrigerant for efficient heat exchange within a shell-and-tube condenser. R507 refrigerant is commonly used in the industry as the low-temperature refrigerant for this process to ensure condensation efficiency and system stability.

[0003] The existing direct cooling system has a fixed medium flow path: after VDF gas is discharged from the separation tower, it enters the tube side of the shell-and-tube condenser and exchanges heat with the R507 refrigerant flowing in the shell side. The gaseous VDF condenses into a liquid state upon cooling and is introduced into the storage tank through the tube side drain port and the liquid delivery pipe. The VDF gas that is not completely condensed enters the recovery tank through the tube side outlet and the gas delivery pipe for further processing. Meanwhile, the R507 refrigerant in the shell side absorbs the heat of the VDF gas in the tube side and vaporizes, then returns to the external refrigeration unit for cooling and liquefaction, forming a cycle for reuse.

[0004] However, in actual operation, if the heat exchange tubes of the shell-and-tube condenser rupture due to prolonged low-temperature conditions, or if the sealing structure between the tube side and shell side fails, the R507 refrigerant in the shell side will leak to the tube side. On the one hand, the mixing of R507 refrigerant and VDF medium will directly contaminate the product, causing economic losses; on the other hand, after the R507 leaks, it will instantly vaporize in the tube side, absorbing a large amount of surrounding heat, causing a sharp drop in the internal temperature of the shell-and-tube condenser. At the same time, the gas produced by vaporization will rapidly push up the pressure in the tube side, which can easily lead to overpressure damage to the equipment, or even cause a safety accident.

[0005] For the reasons mentioned above, we propose a leak monitoring system for vinylidene fluoride condensation. Utility Model Content

[0006] The purpose of this invention is to provide a leak monitoring system for vinylidene fluoride condensation, aiming to solve the problem in the prior art that lacks a leak control mechanism that can promptly identify and automatically respond to leaks in the early stages.

[0007] To achieve the above objectives, the technical solution adopted by this utility model is as follows.

[0008] A leak monitoring system for vinylidene fluoride condensation includes a tube-and-shell condenser. The tube-side inlet of the condenser is connected to a separation tower, the tube-side outlet is connected to a recovery tank via a gas supply pipe, and the tube-side drain outlet is connected to a storage tank via a liquid supply pipe. The shell-side inlet and outlet are connected to a condensate input pipe and a condensate output pipe, respectively. The system also includes a controller. The tube-and-shell condenser contains a pressure sensor and a temperature sensor. The condensate input pipe, condensate output pipe, tube-side inlet, and liquid supply pipe are each equipped with a first, second, third, and fourth electrically controlled valves, respectively. A branch pipe is also provided between the tube-and-shell condenser and the recovery tank. The branch pipe is equipped with a fifth electrically controlled valve for controlling the on / off state of the branch pipe. The controller is electrically connected to the pressure sensor, temperature sensor, first, second, third, fourth, and fifth electrically controlled valves, respectively.

[0009] Furthermore, at least two temporary storage tanks are connected in series between the drain outlet and the storage tank via a delivery pipe. A fourth electrically controlled valve is provided between the temporary storage tank and the tube condenser, between adjacent temporary storage tanks, and between the temporary storage tank and the storage tank.

[0010] Furthermore, the temporary storage tank is provided with a sampling port, and the sampling port is provided with a valve body.

[0011] Furthermore, if the temperature monitored by the temperature sensor is below -27°C or the pressure monitored by the pressure sensor exceeds 0.55 MPa, the controller controls the first, second, third, and fourth solenoid valves to close and the fifth solenoid valve to open.

[0012] Compared with the shortcomings and deficiencies of existing technologies, this utility model has the following beneficial effects: This invention provides a leak monitoring system for ethylene fluoride condensation. By installing temperature and pressure sensors inside the tube condenser, the system can monitor the temperature and pressure changes of the medium in the tubes in real time. When R507 refrigerant leaks and causes the temperature to drop below -27°C or the pressure to exceed 0.55 MPa, the system can immediately capture the abnormal signal and transmit it to the controller, achieving early and accurate identification of the leak. Simultaneously, the gas supply pipe and the parallel branch pipe form a dual exhaust passage. When a leak occurs, the controller can simultaneously open the fifth electrically controlled valve on the branch pipe, working with the gas supply pipe to quickly discharge the high-pressure gas generated by the vaporization of R507 in the tubes, accelerating the reduction of internal pressure in the tube condenser, preventing overpressure damage to the equipment, and effectively reducing the risk of safety accidents caused by leaks.

[0013] At least two temporary storage tanks are connected in series on the delivery pipeline between the tube-and-shell condenser and the storage tank. This extends the flow path of liquid vinylidene fluoride (VDE). Furthermore, by installing fourth electrically controlled valves between the temporary storage tanks and the tube-and-shell condenser, between adjacent temporary storage tanks, and between the temporary storage tanks and the storage tank, the delivery pipeline is divided into multiple independent pathways. In the event of a leak, the controller can simultaneously shut off each of the fourth electrically controlled valves, creating independent isolation spaces for each temporary storage tank. Workers can then use the sampling ports of each temporary storage tank to detect whether the medium inside is contaminated with R507, eliminating the need for a comprehensive inspection of the entire delivery pipeline and storage tank. This allows for rapid and accurate identification of the contamination area, preventing uncontaminated media from being mishandled and minimizing raw material waste and production losses. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the medium flow path in a leak monitoring system for vinylidene fluoride condensation according to this utility model.

[0015] Figure 2 This is a schematic diagram of the sensor control relationship in this utility model.

[0016] In the diagram: 1. Separation tower; 2. Shell and tube condenser; 3. Liquid storage tank; 4. Recovery tank; 5. Refrigerant inlet pipe; 6. Refrigerant outlet pipe; 7. Gas delivery pipe; 8. Liquid delivery pipe; 9. Temperature sensor; 10. Pressure sensor; 11. First solenoid valve; 12. Second solenoid valve; 13. Third solenoid valve; 14. Fourth solenoid valve; 15. Branch pipe; 16. Fifth solenoid valve; 17. Temporary storage tank; 18. Controller. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0018] Example 1 Reference Figure 1 and Figure 2 This embodiment provides a leak monitoring system for vinylidene fluoride condensation, including a separation tower 1, a tube-and-shell condenser 2, a storage tank 3, a recovery tank 4, and a controller 18. The tube-side inlet of the tube-and-shell condenser 2 is connected to the separation tower 1 via a pipeline to receive vinylidene fluoride gas output from the separation tower 1. The tube-side outlet of the tube-and-shell condenser 2 is connected to the recovery tank 4 via a gas delivery pipe 7 to introduce uncondensed vinylidene fluoride gas into the recovery tank 4. The tube-side drain port of the tube-and-shell condenser 2 is connected to the storage tank 3 via a liquid delivery pipe 8 to transport condensed liquid vinylidene fluoride to the storage tank 3 for storage. The shell-side inlet and shell-side outlet of the tube-and-shell condenser 2 are connected to an external refrigeration unit via a refrigerant input pipe 5 and a refrigerant output pipe 6, respectively, to form a refrigerant circulation path.

[0019] The condenser uses R507 refrigerant, and its working process is as follows: R507 refrigerant enters the shell side of the shell-side condenser 2 through the shell-side inlet, where it exchanges heat with the vinylidene fluoride gas in the tube side. After absorbing the heat from the vinylidene fluoride gas, it vaporizes. The vaporized R507 refrigerant is then discharged through the shell-side outlet and returned to the external refrigeration unit for cooling and liquefaction, completing the cycle. The vinylidene fluoride gas generated in the separation tower 1 enters the tube side of the shell-side condenser 2 through the tube-side inlet, where it fully exchanges heat with the R507 refrigerant in the shell side, condensing from a gaseous state to a liquid state. The liquid vinylidene fluoride is then introduced into the storage tank 3 through the tube-side drain port and the liquid delivery pipe 8. The uncondensed vinylidene fluoride gas enters the recovery tank 4 through the tube-side outlet and the gas delivery pipe 7.

[0020] To achieve leak monitoring and automatic control, a temperature sensor 9 and a pressure sensor 10 are installed on the top of the shell-and-tube condenser 2. Temperature sensor 9 is used to monitor the temperature of the medium within the tubes of the shell-and-tube condenser 2 in real time. Temperature sensor 9 can be a PTFE-sheathed, epoxy-encapsulated NTC thermistor temperature sensor (Model 44100 Series), with an operating temperature range of -40 to 100°C. Pressure sensor 10 is used to monitor the pressure of the medium within the tubes of the shell-and-tube condenser 2 in real time. Pressure sensor 10 can be an industrial-grade submersible pressure sensor, AST4530 series, which offers excellent corrosion resistance and a pressure measurement accuracy of ±0.25%FSO.

[0021] Meanwhile, a first electrically controlled valve 11 is installed on the condenser input pipe 5 at the shell-side inlet of the shell-side condenser 2 to control the flow of condenser into the shell side; a second electrically controlled valve 12 is installed on the condenser output pipe 6 at the shell-side outlet to control the flow of condenser out of the shell side; a third electrically controlled valve 13 is installed on the pipe at the tube-side inlet of the shell-side condenser 2 to control the flow of vinylidene fluoride gas into the tube side; and a fourth electrically controlled valve 14 is installed on the liquid delivery pipe 8 connecting the tube-side drain port and the storage tank 3 to control the flow of liquid vinylidene fluoride into the storage tank 3. The controller 18 is electrically connected to the temperature sensor 9, pressure sensor 10, first electrically controlled valve 11, second electrically controlled valve 12, third electrically controlled valve 13, and fourth electrically controlled valve 14, respectively. It can receive monitoring data from the temperature sensor 9 and pressure sensor 10 and control the on / off state of each electrically controlled valve according to preset logic.

[0022] Under normal system conditions, the pressure range monitored by pressure sensor 10 is 0.45MPa ≤ pressure ≤ 0.5MPa, and the temperature range monitored by temperature sensor 9 is -25℃ ≤ temperature ≤ -20℃. When the shell-and-tube condenser 2 leaks, the R507 refrigerant will instantly vaporize after entering the tube side, absorbing a large amount of heat, causing the temperature inside the tube side to drop sharply. At the same time, the gas produced by vaporization causes the pressure inside the tube side to rise rapidly. At this time, the pressure monitored by pressure sensor 10 will exceed 0.55MPa, or the temperature monitored by temperature sensor 9 will drop below -27℃, triggering the leak warning mechanism.

[0023] Controller 18 can be an industrial-grade PLC controller (programmable logic controller), such as the Siemens S7-1200 series PLC. This type of controller has multi-channel analog and digital input / output interfaces, and can stably receive analog temperature signals of -27℃ to -20℃ from temperature sensor 9 (such as a PT100 platinum resistance sensor) and analog pressure signals of 0.45MPa to 0.55MPa from pressure sensor 10 (such as a diffused silicon pressure sensor). It can also accurately control the on / off state of the first to fifth electrically controlled valves (solenoid valves or electric shut-off valves) through the digital output interface, with a response delay of ≤100ms, meeting the rapid control requirements for emergency leakage handling.

[0024] Meanwhile, the controller 18 supports industrial communication protocols such as Modbus, Profinet, or EtherNet / IP, and can be directly connected to the factory's existing production electrical control system, such as a DCS distributed control system. Real-time monitoring data is uploaded to the central monitoring platform of the production electrical control system via the communication interface, enabling remote visual monitoring of the system's operating status. It can also receive control commands from the production electrical control system, such as adjusting pressure / temperature warning thresholds, to achieve coordinated control with the entire factory's production process.

[0025] A branch pipe 15 is connected in parallel to the gas supply pipe 7. One end of the branch pipe 15 is connected to the tube outlet side of the tube condenser 2, and the other end is connected to the recovery tank 4. A fifth solenoid valve 16 is provided on the branch pipe 15. The fifth solenoid valve 16 is electrically connected to the controller 18. The controller 18 controls the opening and closing of the branch pipe 15. When the condenser leaks, the branch pipe is connected, which helps to quickly discharge the gas in the tube condenser, thereby quickly reducing the internal gas pressure of the tube condenser.

[0026] The electrically controlled valve in this utility model can be an electronic fluoropolymer-lined single-seat regulating valve (KZDLPF series), which is suitable for the corrosion resistance and sealing requirements of vinylidene fluoride production. It can be stably linked with the system controller 18 to meet the functional requirements of emergency control.

[0027] The above settings can achieve the following: 1. Normal operation phase The first solenoid valve 11, the second solenoid valve 12, the third solenoid valve 13, and the fourth solenoid valve 14 are all open. R507 refrigerant enters the shell side of the tube condenser 2 through the condenser inlet pipe 5 and the first solenoid valve 11, where it exchanges heat with the tube side and vaporizes. Then it returns to the refrigeration unit through the second solenoid valve 12 and the condenser outlet pipe 6, forming a condenser cycle.

[0028] The vinylidene fluoride gas in the separation tower 1 enters the tube side of the shell-and-tube condenser 2 through the tube side inlet and the third solenoid valve 13, where it exchanges heat with the R507 refrigerant in the shell side and condenses. The liquid vinylidene fluoride enters the storage tank 3 through the liquid delivery pipe 8 and the fourth solenoid valve 14. The uncondensed vinylidene fluoride gas enters the recovery tank 4 through the gas delivery pipe 7.

[0029] During this process, temperature sensor 9 and pressure sensor 10 collect temperature and pressure data in the pipe in real time and transmit them to controller 18. Controller 18 monitors the data in real time. If the data is maintained within the normal range, i.e. 0.45MPa≤pressure≤0.5MPa and -25℃≤temperature≤-20℃, the system maintains normal operation.

[0030] 2. Leakage Emergency Response Phase When the shell-and-tube condenser 2 leaks, such as when the heat exchange tube ruptures, the R507 refrigerant in the shell side seeps into the tube side, instantly vaporizes and absorbs heat, causing a sudden drop in temperature and a sudden rise in pressure in the tube side.

[0031] When temperature sensor 9 detects that the pipe-side temperature is below -27℃, or when pressure sensor 10 detects that the pipe-side pressure exceeds 0.55MPa, it immediately transmits the abnormal data to controller 18.

[0032] Upon receiving abnormal data, the controller 18 controls the first electrically controlled valve 11 to close, cutting off the input path of the shell-side condenser and preventing more R507 refrigerant from entering the system; it controls the second electrically controlled valve 12 to close, cutting off the output path of the shell-side condenser and preventing leaked refrigerant from spreading with the circulation; it controls the third electrically controlled valve 13 to close, cutting off the path of vinylidene fluoride gas entering the tube side and preventing the contamination range from expanding; it controls the fourth electrically controlled valve 14 to close, cutting off the path of liquid vinylidene fluoride entering the liquid storage tank 3 and preventing R507-contaminated vinylidene fluoride from flowing into the liquid storage tank 3; simultaneously, it controls the fifth electrically controlled valve 16 to open, allowing the high-pressure gas accumulated in the tube side to be quickly discharged into the recovery tank 4 through the dual passage of the main gas pipeline 7 and the branch pipe 15. Compared with a single gas pipeline, the dual passage can significantly improve the gas discharge rate, accelerate the reduction of internal gas pressure in the shell and tube condenser 2, and effectively mitigate the safety risks caused by a sudden pressure rise.

[0033] Example 2 Example 2 is a further improvement on Example 1.

[0034] This embodiment discloses a leak monitoring system for vinylidene fluoride condensation, wherein at least two temporary storage tanks 17 are connected in series on the liquid delivery pipe 8 between the tube condenser 2 and the storage tank 3. The inlet of the temporary storage tank 17 is located at the top of the tank body, and the outlet is located at the lower part of the side wall of the tank body, communicating with the downstream liquid delivery pipe 8; the volume of each temporary storage tank 17 is approximately 15m³. 3 .

[0035] A fourth electrically controlled valve 14 is installed on the liquid delivery pipe 8 between the temporary storage tank 17 and the tube condenser 2, the liquid delivery pipe 8 between adjacent temporary storage tanks 17, and the liquid delivery pipe 8 between the temporary storage tank 17 and the storage tank 3. All fourth electrically controlled valves 14 are electrically connected to the controller 18.

[0036] Each temporary storage tank 17 is equipped with a sampling port on its side wall, and a valve body is fitted at the sampling port. The valve body can be either a manual ball valve or an electrically controlled valve. In the event of a leak, a sample can be quickly taken through the sampling port for testing, making it easy to quickly determine whether the medium in the temporary storage tank has been contaminated by R507 refrigerant.

[0037] The above settings can achieve the following: 1. Normal operation phase The liquid vinylidene fluoride generated by condensation in the tube side of the shell-and-tube condenser flows sequentially into the series-connected temporary storage tanks 17 and 15m via the delivery pipe 8. 3 The single tank volume can buffer the liquid vinylidene fluoride; after flowing through all the temporary storage tanks 17, the liquid vinylidene fluoride finally flows into the storage tank 3 to complete the storage. 2. Leakage Emergency Response Phase When the tube condenser 2 leaks, the controller 18 triggers the emergency logic and simultaneously closes all the fourth solenoid valves 14 between the tube condenser 2 and the liquid storage tank 3, cuts off the connection between the tube condenser 2 and the temporary storage tank 17, the adjacent temporary storage tank 17, and the temporary storage tank 17 and the liquid storage tank 3, to prevent liquid vinylidene fluoride contaminated by R507 from flowing into the liquid storage tank 317 and to protect the uncontaminated medium in the liquid storage tank 3. During the emergency response phase of a leak, personnel can conduct precise testing on each of the series-connected temporary storage tanks 17: sampling valves on the side walls of storage tank 17 are opened to collect media samples. Analysis of the sample composition directly determines whether the liquid vinylidene fluoride in the corresponding storage tank 17 has been contaminated by R507 refrigerant, thus accurately defining the spread of the contaminated medium and the number of affected storage tanks 17. Only the confirmed contaminated storage tanks 17 are cleaned, effectively reducing the waste of uncontaminated vinylidene fluoride and minimizing economic losses and process interruptions caused by leaks.

[0038] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A leak monitoring system for vinylidene fluoride condensation, comprising a tube-and-shell condenser (2), wherein the tube-side inlet of the tube-side condenser (2) is connected to a separation tower (1), the tube-side outlet is connected to a recovery tank (4) via a gas delivery pipe (7), the tube-side drain outlet is connected to a storage tank (3) via a liquid delivery pipe (8), and the shell-side inlet and outlet are respectively connected to a condensate input pipe (5) and a condensate output pipe (6), characterized in that, It also includes a controller (18), and the tube condenser (2) is equipped with a pressure sensor (10) and a temperature sensor (9). The refrigerant input pipe (5), the refrigerant output pipe (6), the tube inlet and the liquid delivery pipe (8) are respectively equipped with a first solenoid valve (11), a second solenoid valve (12), a third solenoid valve (13) and a fourth solenoid valve (14). A branch pipe (15) is also provided between the tube condenser (2) and the recovery tank (4). The branch pipe (15) is equipped with a fifth solenoid valve (16) for controlling the opening and closing of the branch pipe (15). The controller (18) is electrically connected to the pressure sensor (10), the temperature sensor (9), the first solenoid valve (11), the second solenoid valve (12), the third solenoid valve (13), the fourth solenoid valve (14) and the fifth solenoid valve (16).

2. The leakage monitoring system as described in claim 1, characterized in that, At least two temporary storage tanks (17) are connected in series between the drain outlet and the storage tank (3) via a delivery pipe (8). A fourth electric control valve (14) is provided between the temporary storage tank (17) and the tube condenser (2), between adjacent temporary storage tanks (17), and between the temporary storage tank (17) and the storage tank (3).

3. The leakage monitoring system as described in claim 2, characterized in that, The temporary storage tank (17) is provided with a sampling port, and the sampling port is provided with a valve body.

4. The leakage monitoring system as described in claim 1, characterized in that, When the temperature monitored by the temperature sensor (9) is below -27°C or the pressure monitored by the pressure sensor (10) exceeds 0.55 MPa, the controller (18) controls the first solenoid valve (11), the second solenoid valve (12), the third solenoid valve (13) and the fourth solenoid valve (14) to close, and opens the fifth solenoid valve (16).

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