Medium phase transition purging and recovery system and control method thereof

Abstract

The present application relates to refrigerant recovery technical field, specifically to a kind of medium phase change purging recovery system and control method thereof, comprising, pressure reducing valve, first check valve, end workpiece, evaporator group, liquid storage tank and drain valve;Wherein the inlet end of pressure reducing valve is gas source import, and the gas outlet end of drain valve is gas source export;Refrigeration system;Still include first temperature sensor, second temperature sensor;Heater;Wherein: the temperature detected by first temperature sensor is T1, and the temperature detected by second temperature sensor is T2, when T1-T2≤T, start heater and refrigeration system;Wherein T is the fixed temperature value of T1-T2 measured when most of refrigerant in refrigerant recovery pipeline is discharged.The medium phase change purging recovery system and control method thereof of the present application judge whether to access heater to heat dry gas by the temperature difference of gas entering end workpiece and discharging end workpiece, accurate control, reduce energy waste.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refrigerant recovery, in particular to a medium phase change purging recovery system and a control method thereof. BACKGROUND

[0002] Fluorinated liquid is widely used in semiconductor manufacturing, precision electronic cleaning and some special chemical fields due to its excellent chemical stability and insulation performance. In these processes, it is often necessary to recover the fluorinated liquid in the equipment or container to realize the recycling of materials, reduce production cost and meet environmental protection requirements. The existing fluorinated liquid recovery system usually adopts gas purging technology, that is, dry inert gas (such as nitrogen) is introduced into the system, and the gas flow is used to drive and carry the liquid fluorinated liquid to the recovery processing unit.

[0003] In order to determine whether the recovery is complete, the following methods are generally used in the prior art: first, the fixed purging time control method, which sets a fixed purging time according to experience. However, this method has obvious defects: the pollution degree of the system, the complexity of the pipeline structure (especially the existence of dead corners) and the change of the environmental temperature will significantly affect the actual purging time. If the set time is too short, the fluorinated liquid will remain in the dead corners, causing yield loss and potential product contamination risk. If the set time is too long, it will cause waste of electricity and purging gas, reducing production efficiency. The second method is liquid level monitoring, which installs a liquid level sensor in the main recovery chamber or storage tank. When the liquid level reaches the set value, it is determined that the recovery is complete. This method cannot sense the residual fluorinated liquid in the complex pipeline, valves, elbows and other "dead zones". These residual liquids have little effect on the liquid level monitoring result when they are not discharged, but these residual liquids in the dead zones are the key to affecting the recovery rate and cleanliness.

[0004] To deal with the residual in the dead zone, a heating module is introduced in the prior art, which reduces the viscosity of the fluorinated liquid by locally heating the dead zone or preheating the purging gas, so as to promote its vaporization and make it easier to be carried out by the gas. However, the early introduction of heating gas can easily cause excessive phase change loss of fluorinated liquid, resulting in waste of resources. Therefore, how to accurately determine the timing of introducing heating gas becomes an important problem. Therefore, a medium phase change purging recovery system and a control method thereof are provided. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to overcome the problem that the prior art cannot accurately and effectively determine when to connect the heating gas, and a medium phase change purging recovery system and a control method thereof are provided. The temperature difference between the gas entering the end workpiece and the gas discharged from the end workpiece is used to determine whether to connect the heater to heat the dry gas, so as to accurately control and reduce energy waste.

[0006] To solve the above technical problems, the application provides a medium phase change purging and recycling system and a control method thereof, which comprises a pressure reducing valve, a first check valve, an end workpiece, an evaporator group, a liquid storage tank and a drain valve, the pressure reducing valve and the first check valve are connected in series through a connecting pipeline to form a gas supply pipeline, the evaporator group, the liquid storage tank and the drain valve are connected in series through a connecting pipeline to form an exhaust pipeline, and the gas supply pipeline and the exhaust pipeline are connected to the end workpiece through a connecting pipeline and are communicated with the internal flow channel of the end workpiece to form a refrigerant recycling pipeline.

[0007] The inlet end of the pressure reducing valve is a gas source inlet, and the gas outlet end of the drain valve is a gas source outlet.

[0008] The application further provides a refrigeration system for generating low-temperature working medium and passing the low-temperature working medium into the evaporator group for heat exchange.

[0009] The application further provides a first temperature sensor and a second temperature sensor.

[0010] The first temperature sensor is installed on the gas supply pipeline and is used for detecting the temperature of the fluid entering the end workpiece, and the second temperature sensor is installed on the exhaust pipeline and is used for detecting the temperature of the fluid discharged from the end workpiece.

[0011] A heater is installed on the gas supply pipeline and is located at the front end of the first temperature sensor and is used for heating the fluid flowing therethrough.

[0012] The first temperature sensor detects a temperature T1, the second temperature sensor detects a temperature T2, and when T1-T2≤T, the heater and the refrigeration system are started.

[0013] T is a fixed temperature value of T1-T2 measured when most of the refrigerant in the refrigerant recycling pipeline is discharged.

[0014] In an embodiment of the application, a fluid resistance monitoring module is further provided for monitoring the real-time fluid resistance of the refrigerant recycling pipeline, and the amount of residual liquid in the dead zone of the refrigerant recycling pipeline is proportional to the real-time fluid resistance.

[0015] When the heater is started, the real-time fluid resistance monitored by the fluid resistance monitoring module is used to control the operating state of the heater and the refrigeration system.

[0016] The fluid resistance monitoring module comprises at least one pressure sensor.

[0017] In an embodiment of the application, a third temperature sensor is further installed on the connecting pipeline between the evaporator group and the liquid storage tank, is used for detecting the real-time temperature T3 of the fluid flowing therethrough, and is used for adjusting the operating state of the refrigeration system according to the real-time temperature T3.

[0018] In one embodiment of the present invention, when the fluid resistance monitoring module is a pressure sensor, the pressure sensor is installed at the inlet of the pressure reducing valve to detect the real-time pressure P at the inlet of the pressure reducing valve. The real-time pressure P can be used to calculate the actual real-time fluid resistance.

[0019] In one embodiment of the present invention, the reference pressure value at the inlet of the pressure reducing valve is set to Pr;

[0020] When P > Pr, extend the heater heating time or increase the heater operating frequency until P ≤ Pr and tends to stabilize;

[0021] When P ≤ Pr and tends to stabilize, turn off the heater and stop the refrigeration system.

[0022] In one embodiment of the present invention, the reference pressure value Pr is the reference value at the inlet of the pressure reducing valve measured when the refrigerant recovery pipeline is pure and free of residue and dry gas at the corresponding temperature is introduced.

[0023] In one embodiment of the present invention, when the fluid resistance monitoring module consists of two pressure sensors, the two pressure sensors are respectively installed at the inlet of the pressure reducing valve and the gaseous outlet of the steam trap.

[0024] The real-time pressure detected at the inlet of the pressure reducing valve is P1;

[0025] The real-time pressure detected at the gas outlet of the steam trap is P2;

[0026] The pressure difference between the real-time pressure at the inlet of the pressure reducing valve and the real-time pressure P2 at the gaseous outlet of the steam trap can be used to calculate the actual real-time fluid resistance.

[0027] In one embodiment of the present invention, the pressure difference between the pressure at the inlet of the pressure reducing valve and the pressure at the gaseous outlet of the steam trap is set as ΔP.

[0028] When P1-P2>ΔP, extend the heater heating time or increase the heater operating frequency until P1-P2≤ΔP and tends to stabilize;

[0029] When P1-P2≤ΔP and the system tends to stabilize, turn off the heater and stop the refrigeration system.

[0030] In one embodiment of the present invention, the reference pressure difference ΔP is a reference value measured when the refrigerant recovery pipeline is pure and free of residue and is purged with dry gas at the corresponding temperature.

[0031] It also includes a control method for a medium phase change purging and recovery system, which is applied to any one of the medium phase change purging and recovery systems of claims 1-9.

[0032] The technical solution of the present invention has the following advantages over the prior art:

[0033] The medium phase change purging and recycling system and the control method thereof can realize the control of the medium phase change purging and recycling system by introducing multiple control nodes and comparing the detected system parameters with the reference parameters of the system at the control nodes;

[0034] Specifically, one of the control nodes judges whether the refrigerant has been mostly discharged by the temperature difference of the gas entering the end workpiece and the gas discharged from the end workpiece, and performs the action of starting the heater and the refrigeration system, that is, when the heater is not started, the dry gas is directly introduced, if the temperature difference of the gas entering the end workpiece and the gas discharged from the end workpiece does not reach the judgment value of starting the heater, the introduction of the dry gas is continued, and if the judgment value of starting the heater is reached, the heater is started.

[0035] Further, after the heater and the refrigeration system are started, another control node judges the real-time fluid resistance in the system running process by the real-time pressure at the inlet of the pressure reducing valve or the difference between the real-time pressure at the inlet of the pressure reducing valve and the real-time pressure at the gaseous outlet of the drain valve, so as to judge whether the dead zone residual liquid in the refrigerant recovery pipeline is completely removed, and perform the action of adjusting the running state of the heater and the refrigeration system or closing the heater and the refrigeration system, that is, after the heated dry gas is introduced, it is judged whether the real-time pressure at the inlet of the pressure reducing valve or the difference between the real-time pressure at the inlet of the pressure reducing valve and the real-time pressure at the gaseous outlet of the drain valve reaches the reference value of the control node in the real-time state of the system running, and the action of adjusting the running state of the heater and the refrigeration system or closing the heater and the refrigeration system is performed according to the judgment result.

[0036] In summary, the present application can add control actions according to the real-time running state in the system running process, so as to accurately control and reduce energy waste. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments of the present application and in conjunction with the drawings, wherein,

[0038] Figure 1 is the schematic diagram of the present application;

[0039] Figure 2 is the system schematic diagram of one embodiment of the present application;

[0040] Figure 3 is the system schematic diagram of another embodiment of the present application;

[0041] Figure 4 is the control method flow chart when the fluid resistance monitoring module is a pressure sensor of the present application;

[0042] Figure 5is the control method flow chart of the fluid resistance monitoring module of the present application when two pressure sensors are used;

[0043] Figure 6 is the system diagram of the practical application scenario of the present application.

[0044] The description of the reference signs is as follows: 1, pressure reducing valve; 2, first check valve; 3, end workpiece; 4, evaporator group; 5, liquid storage tank; 6, drain valve; 7, refrigeration system; 8, first temperature sensor; 9, second temperature sensor; 10, heater; 11, fluid resistance monitoring module; 12, third temperature sensor; 13, second check valve; 14, circulating pump; 15, gas separation; 16, first electromagnetic valve; 17, third check valve; 18, liquid accumulator; 19, fourth check valve. DETAILED DESCRIPTION

[0045] The present application will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it, but the embodiments are not limiting to the present application.

[0046] Reference Figure 1 , 4 , 5, a medium phase change purging and recycling system of the present application comprises: a pressure reducing valve 1, a first check valve 2, an end workpiece 3, an evaporator group 4, a liquid storage tank 5 and a drain valve 6, the pressure reducing valve 1 and the first check valve 2 are connected in series through a connecting pipeline to form a gas supply pipeline, the evaporator group 4, the liquid storage tank 5 and the drain valve 6 are connected in series through a connecting pipeline to form an exhaust pipeline, the gas supply pipeline and the exhaust pipeline are connected to the end workpiece 3 through a connecting pipeline and are communicated with the internal flow passage of the end workpiece 3 to form a refrigerant recovery pipeline, wherein the inlet end of the pressure reducing valve 1 is a gas source inlet, and the gas outlet end of the drain valve 6 is a gas source outlet;

[0047] The gas source inlet is connected to a dry gas supply device, such as a nitrogen supply device, to send dry nitrogen gas into the refrigerant recovery pipeline, i.e. from the inlet end of the pressure reducing valve 1, the dry nitrogen gas after entering the refrigerant recovery pipeline passes through the first check valve 2, the end workpiece 3, the evaporator group 4, the liquid storage tank 5 and the drain valve 6 in sequence through the connecting pipeline, the dry nitrogen gas flow carries out the refrigerant remaining in the internal flow passage of the end workpiece 3 and the exhaust pipeline, wherein the mixed fluid after the dry nitrogen gas flow mixes with the refrigerant flows through the liquid storage tank 5, the liquid refrigerant flows into the liquid storage tank 5 for storage, and the gaseous nitrogen gas passes through the drain valve 6 and is recovered and utilized by the nitrogen supply device;

[0048] A refrigeration system 7 is used to generate low-temperature working medium and to pass the low-temperature working medium into the evaporator group 4 for heat exchange, the refrigeration system 7 is a primary refrigeration or cascade refrigeration, and each evaporator of the evaporator group 4 is connected to the refrigerant flow circulation loop of the refrigeration system 7 to heat exchange the mixed fluid flowing through the evaporator.

[0049] In the prior art, the recovery of refrigerant is usually carried out by a timing purge method. In this method, dry gas is directly introduced into the system, and the purge time is set by experience. In the case where the dry gas is not heated, more time is required to purge the refrigerant recovery pipeline, and it is not clear whether the internal refrigerant is completely recovered.

[0050] Based on the above refrigerant recovery method, the present application further comprises a first temperature sensor 8 and a second temperature sensor 9.

[0051] The first temperature sensor 8 is installed on the gas supply pipeline to detect the temperature of the fluid entering the end workpiece 3, and the second temperature sensor 9 is installed on the exhaust pipeline to detect the temperature of the fluid discharged from the end workpiece 3.

[0052] A heater 10 is installed on the gas supply pipeline and located in front of the first temperature sensor 8 to heat the fluid flowing therethrough.

[0053] In the case where the dry gas is heated by the heater 10, the refrigerant can be completely recovered, but when there is a large amount of refrigerant in the refrigerant recovery pipeline, the direct use of heated dry gas will cause the phase change of the refrigerant, and the loss of refrigerant is much higher than in the case where the dry gas is not heated.

[0054] Therefore, the present application sets the detection temperature of the first temperature sensor 8 as T1 and the detection temperature of the second temperature sensor 9 as T2. When T1-T2≤T, the heater 10 and the refrigeration system 7 are started.

[0055] T is a fixed temperature value of T1-T2 measured when most of the refrigerant in the refrigerant recovery pipeline is discharged.

[0056] In summary, the core of the present scheme is to introduce a control node, when the system runs to the node, the heater 10 intervenes in the operation, and at the same time, the refrigeration system 7 is started. The specific measurement is the system parameter when the system runs to the control node, which is the temperature difference T of the gas entering the terminal workpiece 3 and the gas discharged from the terminal workpiece 3. When the system parameter embodied by the system running to the control node, most of the refrigerant in the refrigerant recovery pipeline has been taken out by the dry gas, and the remaining is the residual liquid in the dead zone which is not easy to take out. That is, the temperature difference between the gas entering the terminal workpiece 3 and the gas discharged from the terminal workpiece 3 has reached the interval T1-T2≤T. At this time, the heater 10 is controlled to intervene in heating, and the refrigeration system 7 is started to cool the evaporator group 4 to cope with the subsequent heat exchange. The dry gas flowing through the heater 10 is heated, and after being heated, the dry gas contacts the residual liquid in the dead zone, causing the refrigerant to change phase and mix with the dry gas stream to be taken out of the dead zone. Subsequently, the mixed fluid flows through the evaporator group 4, and after heat exchange in the evaporator group 4, the condensed liquid is liquefied. The liquid refrigerant enters the liquid storage tank 5 for storage, and the gas is discharged through the drain valve 6 and recycled. The refrigerant recovery is completed.

[0057] For example, when it is experimentally measured that most of the refrigerant in the refrigerant recovery pipeline has been taken out by the unheated dry gas, the temperature difference between the gas entering the terminal workpiece 3 and the gas discharged from the terminal workpiece 3 is 2°C, that is, T=2°C. Then, in the process of refrigerant recovery, unheated dry nitrogen is first introduced. According to the first temperature sensor 8T1 and the second temperature sensor 9T2, it is judged whether the standard that the refrigerant has been largely discharged is reached, that is, when T1-T2>2°C, it is proved that part of the refrigerant can be taken out by continuously introducing dry gas stream. When T1-T2≤2°C, it is proved that most of the refrigerant has been taken out by the dry gas, and the remaining small part of the residual liquid in the dead zone cannot be blown out by the dry gas stream. At this time, the heater 10 and the refrigeration system 7 are started, so that the dry gas after heating exchanges heat with the residual liquid in the dead zone, causing the residual liquid in the dead zone to change phase and be taken out with the gas stream. Further, the gaseous refrigerant is condensed and liquefied after passing through the evaporator group 4 of the refrigeration system 7, and enters the liquid storage tank 5. The gas from the outlet of the liquid storage tank 5 enters the drain valve 6 and is discharged, completing the recovery of the refrigerant.

[0058] For example, when it is experimentally measured that most of the refrigerant in the refrigerant recovery pipeline has been taken out by the unheated dry gas, the temperature difference between the gas entering the terminal workpiece 3 and the gas discharged from the terminal workpiece 3 is 2°C, that is, T=2°C. Then, in the process of refrigerant recovery, unheated dry nitrogen is first introduced. According to the first temperature sensor 8T1 and the second temperature sensor 9T2, it is judged whether the standard that the refrigerant has been largely discharged is reached, that is, when T1-T2>2°C, it is proved that part of the refrigerant can be taken out by continuously introducing dry gas stream. When T1-T2≤2°C, it is proved that most of the refrigerant has been taken out by the dry gas, and the remaining small part of the residual liquid in the dead zone cannot be blown out by the dry gas stream. At this time, the heater 10 and the refrigeration system 7 are started, so that the dry gas after heating exchanges heat with the residual liquid in the dead zone, causing the residual liquid in the dead zone to change phase and be taken out with the gas stream. Further, the gaseous refrigerant is condensed and liquefied after passing through the evaporator group 4 of the refrigeration system 7, and enters the liquid storage tank 5. The gas from the outlet of the liquid storage tank 5 enters the drain valve 6 and is discharged, completing the recovery of the refrigerant. Figure 6As shown, in one of the embodiments, the evaporators of the evaporator group 4 are provided with two, and the refrigerant recovery pipeline is applied to the cooling circuit of one end workpiece 3. Specifically, the liquid outlet of the storage tank 5 is connected with a second one-way valve 13 through a connecting pipeline, the outlet end of the second one-way valve 13 is connected with a circulating pump 14 and a gas separator 15 respectively, the circulating pump 14 and the gas separator 15 are installed in series on the connecting pipeline between the two evaporators, and the liquid outlet end of the gas separator 15 is communicated with the inlet end of the circulating pump 14. The outlet end of the first one-way valve 2 is communicated with the inlet end of the gas separator 15 through a connecting pipeline, and the first electromagnetic valve 16 and the third one-way valve 17 are installed on the connecting pipeline. In addition, the liquid outlet of the drain valve 6 is connected with a liquid storage device 18, the outlet end of the liquid storage device 18 is provided with a fourth one-way valve 19, and the outlet end of the fourth one-way valve 19 is connected to the inlet end of the third one-way valve 17 through a connecting pipeline.

[0059] Referring to Figure 2 , 4 As shown, the fluid resistance monitoring module 11 is further included for monitoring the real-time fluid resistance of the refrigerant recovery pipeline. The amount of residual liquid in the dead zone of the refrigerant recovery pipeline is proportional to the real-time fluid resistance, that is, when the refrigerant is left in the dead zone, compared with the pipeline without residual refrigerant in the dead zone, the gas needs to overcome greater resistance to pass through;

[0060] When the heater 10 is started, the running state of the heater 10 and the refrigeration system 7 is controlled according to the real-time fluid resistance monitored by the fluid resistance monitoring module 11;

[0061] In the process of refrigerant recovery, the real-time fluid resistance of the refrigerant recovery pipeline is monitored by the fluid resistance monitoring module 11, so as to judge whether there is residual liquid in the dead zone in the refrigerant recovery pipeline, and the running state of the heater 10 and the refrigeration system 7 is controlled according to the judgment result;

[0062] Compared with the above-mentioned embodiments, another control node is added to adjust or stop the running of the system, that is, when the real-time fluid resistance does not reach the system parameter of the control node, the running state of the heater 10 and the refrigeration system 7 is adjusted to make the system parameter gradually close to the system parameter of the control node, and when the system running reaches the system parameter of the control node, the heater 10 and the refrigeration system 7 are controlled to stop running.

[0063] The fluid resistance monitoring module 11 is at least one pressure sensor, which is used to measure the pipeline pressure of the refrigerant recovery pipeline during the refrigerant recovery operation, and to judge the change of the real-time fluid resistance during the system running according to the pressure change;

[0064] The core of the scheme is to select a pressure sensor to measure the real-time pressure. Since the pressure change in the pipeline system is relatively sensitive, the pressure change is selected as the representation of the real-time fluid resistance change, so that the real-time fluid resistance in the refrigerant recovery process can be more sensitively judged to reach the control node, thereby controlling the heater 10 and the refrigeration system 7.

[0065] Referring to Figure 2 , 6 As shown, a third temperature sensor 12 is also installed on the connecting pipeline between the evaporator group 4 and the liquid storage tank 5, for detecting the real-time temperature T3 of the flowing fluid, and adjusting the operating state of the refrigeration system 7 according to the real-time temperature T3.

[0066] In the refrigerant recovery process, the real-time temperature T3 detected by the third temperature sensor 12 is the temperature of the refrigerant before entering the liquid storage tank 5, so as to monitor whether the refrigerant temperature is at the complete condensation temperature in real time, and adjust the operating state of the refrigeration system 7 according to the real-time temperature T3, to ensure that the gaseous refrigerant in the mixed fluid is completely condensed and liquefied.

[0067] In the prior art, a preset refrigeration temperature is usually set for the refrigeration system 7, so that the mixed fluid passing through the evaporator group 4 is condensed and liquefied, but the dead zone residual liquid is taken out, and the temperature of the mixed fluid also changes. Therefore, the set refrigeration temperature must be able to adapt to the change of the temperature of the mixed fluid, so as to avoid the situation that the gaseous refrigerant cannot be condensed and liquefied, which undoubtedly wastes a lot of energy.

[0068] Compared with the above-mentioned prior art, the core of the scheme is to add a dynamic control system. By measuring the real-time temperature T3 of the third temperature sensor 12, it is judged whether the gaseous refrigerant mixed in the mixed fluid passing through the evaporator can be completely condensed and liquefied, so as to control the refrigeration temperature of the refrigeration system 7.

[0069] For example, in the refrigerant recovery process, in order to ensure that the dead zone residual liquid can be completely gasified during the blowing process, the heater 10 is set to heat the dry gas to a residual liquid complete gasification temperature, that is, the temperature value detected at the outlet end of the end workpiece 3 is set to be at least 20℃ higher than the boiling point temperature value of the refrigerant. In order to ensure that the gaseous refrigerant after gasification can be completely condensed and liquefied, the real-time temperature T3 detected by the third temperature sensor 12 is set to be at least 10℃ lower than the boiling point temperature value of the refrigerant.

[0070] Referring to Figure 2 , 4As shown, the scheme is an embodiment of the fluid resistance monitoring module 11 of the application, when the fluid resistance monitoring module 11 is a pressure sensor, the pressure sensor is installed at the inlet of the pressure reducing valve 1, for detecting the real-time pressure P at the inlet of the pressure reducing valve 1, which can be used to calculate the actual real-time fluid resistance;

[0071] During the refrigerant recovery process, the heater 10 heats the dry gas flowing through it, and the heated dry gas enters the flow channel of the end workpiece 3 and contacts the dead zone residual liquid, so that the dead zone residual liquid is gasified and discharged with the airflow. Wherein, the real-time pressure P at the inlet of the pressure reducing valve 1 is detected, and the refrigerant residual liquid in the dead zone is gasified by the inlet of the heated dry gas, which makes the pressure in the refrigerant recovery pipeline rise, and the real-time pressure P at the inlet of the pressure reducing valve 1 changes; after the refrigerant is completely gasified and taken out, only dry gas flows in the refrigerant recovery pipeline, at this time the real-time pressure P at the inlet of the pressure reducing valve 1 falls and tends to be stable;

[0072] The advantage of the scheme is that the real-time pressure P at the inlet of the pressure reducing valve 1 is selected as the representation parameter of the real-time fluid resistance. Whether the fluid resistance increases in the main pipeline, the elbow, the valve or any unforeseen dead zone, as long as the resistance affects the overall flowability, it will be reflected in the inlet pressure. The scheme is simple to install and arrange, does not interfere with the main fluid, and does not need to make complex modifications to the existing equipment structure.

[0073] Reference Figure 4 As shown, the reference pressure value at the inlet of the pressure reducing valve 1 is set as Pr;

[0074] When P>Pr, that is, the real-time fluid resistance of the system has not reached the reference fluid resistance range of the control node, it proves that there is still residual liquid in the system, at this time the heating time of the heater 10 needs to be extended or the operating frequency of the heater 10 needs to be improved, and the size of the real-time pressure P and the reference pressure value Pr is re-judged according to the real-time temperature, until P≤Pr and tends to be stable;

[0075] When P≤Pr and tends to be stable, that is, the real-time fluid resistance of the system has reached the reference fluid resistance range of the control node, the heater 10 is turned off and the refrigeration system 7 is stopped running;

[0076] The reference pressure value Pr is the reference value measured at the inlet of the pressure reducing valve 1 when the refrigerant recovery pipeline is pure and free of residual liquid and the corresponding temperature dry gas is introduced. The reference pressure value Pr here is not a fixed value, but a value that changes with the running state of the system;

[0077] In the prior art, if a fixed reference pressure value Pr is used as the object for comparison with the real-time pressure P, it will be disturbed by the change of the system temperature. Since the drying gas is heated, the actual reference pressure value will drift, which will easily lead to errors in the execution of the judgment, thereby leading to incomplete recovery or overpurging;

[0078] The core of the present scheme is that: first, compared with the prior art which uses a fixed reference pressure value, the dynamic reference pressure value Pr can always maintain the most theoretical value at the current temperature when performing the judgment action, and the system compares the reference pressure value with the real-time pressure P based on the temperature state, which improves the accuracy of the judgment and effectively avoids the incomplete recovery or overpurging of the purge gas.

[0079] In summary, making the reference pressure value Pr at the inlet of the pressure reducing valve 1 a dynamic value that changes with the system operation, rather than a simple improvement, is a core intelligent feature in the closed-loop control strategy of the present application, which changes the system from a static and clumsy execution system to a dynamic and intelligent system with perception and self-adaptation capabilities.

[0080] For example, the refrigerant is Novec 7100, which has a boiling point of about 61℃. Before performing the refrigerant recovery process, the system is debugged so that the flow of the drying gas for purging is constant, with a set value of 20 SLM. A temperature-reference pressure value table is established. Specifically, by adjusting the heater 10, the system is stabilized at different temperature points (such as from 50℃ to 80℃). At each temperature point, nitrogen gas with a constant flow of 20 SLM is introduced. After the flow and pressure are stabilized, the corresponding inlet pressure value is recorded, i.e., the reference pressure value at that temperature is obtained. These temperature-reference pressure value data are made into a table and stored in the memory of the control unit.

[0081] In the execution of the refrigerant recovery process, the first temperature sensor 8T1 and the real-time pressure P at the inlet of the pressure reducing valve 1 are monitored in real time, according to the real-time measured temperature, the pre-stored reference table is inquired, and the reference pressure value Pr corresponding to the current temperature is determined in real time (for example, according to the table, when T1=80℃, Pr=76.5Kpa), at this time, the real-time pressure P at the inlet of the pressure reducing valve 1 is compared with the reference pressure value Pr, when the detected real-time pressure P is equal to 80Kpa, the heating and drying gas purging or the operation power of the heater 10 is continued to be executed, wherein if the operation power of the heater 10 is increased, the reference pressure value corresponding to the current temperature needs to be inquired again according to the temperature transformation, and compared with the current pressure, and further according to the comparison result, the control action of the heater 10 and the refrigeration system 7 is executed, if the real-time pressure P≤the reference pressure value Pr, the work of the heater 10 and the refrigeration system 7 is stopped.

[0082] Referring to Figure 3 , 5 It is shown that the present scheme is another embodiment of the fluid resistance monitoring module 11 of the present application, when the fluid resistance monitoring module 11 is two pressure sensors, the two pressure sensors are respectively installed at the inlet of the pressure reducing valve 1 and the gaseous outlet of the drain valve 6;

[0083] The real-time pressure detected at the inlet of the pressure reducing valve 1 is P1;

[0084] The real-time pressure detected at the gaseous outlet of the drain valve 6 is P2;

[0085] The pressure difference between the real-time pressure at the inlet of the pressure reducing valve 1 and the real-time pressure P2 at the gaseous outlet of the drain valve 6 can be used to calculate the actual real-time fluid resistance;

[0086] Referring to the previous embodiment, the difference is that the present scheme uses the pressure difference between the real-time pressure at the inlet of the pressure reducing valve 1 and the real-time pressure P2 at the gaseous outlet of the drain valve 6 as the representation parameter of the real-time fluid resistance in the system operation process, by detecting the pressure difference between the inlet and outlet of the refrigerant recovery pipeline, whether the system operation reaches the control node is determined by the pressure difference, that is, what control action is executed on the heater 10 and the refrigeration circuit;

[0087] Compared with selecting the real-time pressure P at the inlet of the pressure reducing valve 1 as the representation of the real-time fluid resistance in the system operation process, the present scheme selects the pressure difference between the inlet and outlet of the refrigerant recovery pipeline as the representation of the real-time fluid resistance, which can more stably and accurately judge the real-time fluid resistance of the system, so as to accurately judge whether the dead zone residual is completely removed, that is, when the dead zone residual exists, the pressure difference between the inlet and outlet of the refrigerant recovery pipeline can be directly reflected.

[0088] Referring to Figure 5As shown, the pressure difference between the pressure at the inlet of the pressure reducing valve 1 and the pressure at the gaseous outlet of the trap valve 6 is ΔP;

[0089] When P1-P2> ΔP, that is, the real-time fluid resistance of the system has not reached the reference fluid resistance range of the control node, it proves that there is still residual liquid in the system, and the heating time of the heater 10 is extended or the operating frequency of the heater 10 is increased until P1-P2≤ ΔP and tends to be stable.

[0090] When P1-P2≤ ΔP and tends to be stable, that is, the real-time fluid resistance of the system has reached the reference fluid resistance range of the control node, the heater 10 is turned off and the operation of the refrigeration system 7 is stopped.

[0091] The reference pressure difference ΔP is a reference value measured when the refrigerant recovery pipeline is clean and free of residues and the corresponding temperature dry gas is introduced. The reference pressure difference ΔP is also a dynamic value that changes with the operating state of the system. That is, when the temperature of the system changes, the viscosity of the gas increases. Even in the state that the refrigerant recovery pipeline is clean and free of residues, the pressure difference between the pressure at the inlet of the pressure reducing valve 1 and the pressure at the gaseous outlet of the trap valve 6 will change with the change of temperature, that is, ΔP will increase accordingly. Therefore, when selecting the reference pressure difference for comparison, the different reference pressure differences ΔP measured at the corresponding temperature also need to be used as the comparison items.

[0092] For example, the analysis principle is the same as the previous embodiment, but the present scheme needs to establish a temperature and reference pressure difference comparison table and store it in the controller, and compare the detected real-time pressure difference with the measured reference pressure difference. For example, when the system is clean and free of residues, the dry gas flow is 20 SLM, the heater 10 is heated to the first temperature sensor 8 detection temperature T1 = 80℃, ΔP = 12.8Kpa, and if the difference P1-P2 is greater than 12.8Kpa at this time, continue to introduce heated dry gas or increase the operating power of the heater 10. It needs to be noted that increasing the operating power of the heater 10 requires requerying the reference pressure value corresponding to the current temperature according to the temperature change. If the difference P1-P2 is less than or equal to 12.8Kpa at this time and tends to be stable, it proves that the internal dead zone residual liquid has been removed, and the heater 10 and the refrigeration system 7 can be turned off.

[0093] Referring to Figure 4 , As shown, the pressure difference between the pressure at the inlet of the pressure reducing valve 1 and the pressure at the gaseous outlet of the trap valve 6 is ΔP; 5 The control method of the medium phase change purging and recovery system is applied to the medium phase change purging and recovery system, and the specific implementation refers to the control method in the medium phase change purging and recovery system.

[0094] Obviously, the above embodiments are merely example for clearly illustrating, and are not limitation to the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments are not required to be enumerated, and the obvious changes or variations derived from the above are still within the protection scope of the present application.

Claims

1. A media phase-transition purge and recovery system, comprising: The application relates to a refrigerant recovery system, which comprises a pressure reducing valve, a first one-way valve, an end workpiece, an evaporator group, a liquid storage tank and a drain valve, the pressure reducing valve and the first one-way valve are connected in series through a connecting pipeline to form a gas supply pipeline, the evaporator group, the liquid storage tank and the drain valve are connected in series through a connecting pipeline to form an exhaust pipeline, the gas supply pipeline and the exhaust pipeline are connected to the end workpiece through a connecting pipeline and are communicated with an internal flow channel of the end workpiece to form a refrigerant recovery pipeline. The inlet end of the pressure reducing valve is a gas source inlet, and the gas outlet end of the drain valve is a gas source outlet. The refrigeration system is used for generating low-temperature working medium and passing the low-temperature working medium into the evaporator group for heat exchange. The refrigeration system further comprises a first temperature sensor and a second temperature sensor. The first temperature sensor is installed on the gas supply pipeline and is used for detecting the temperature of fluid entering the end workpiece, and the second temperature sensor is installed on the exhaust pipeline and is used for detecting the temperature of fluid discharged from the end workpiece. A heater is installed on the gas supply pipeline and is located in front of the first temperature sensor and is used for heating the fluid passing through. The first temperature sensor detects a temperature T1, the second temperature sensor detects a temperature T2, and when T1-T2<=T, the heater and the refrigeration system are started. T is a fixed temperature value of T1-T2 measured when most of the refrigerant in the refrigerant recovery pipeline is discharged. The refrigeration system further comprises a fluid resistance monitoring module which is used for monitoring the real-time fluid resistance of the refrigerant recovery pipeline, and the amount of residual liquid in the dead zone of the refrigerant recovery pipeline is proportional to the real-time fluid resistance.

2. A medium phase transition purging and recovery system according to claim 1, wherein: When the heater is started, the real-time fluid resistance monitored by the fluid resistance monitoring module is used to control the running state of the heater and the refrigeration system. The fluid resistance monitoring module is at least one pressure sensor. A third temperature sensor is further installed on the connecting pipeline between the evaporator group and the liquid storage tank, which is used for detecting the real-time temperature T3 of the fluid passing through and adjusting the running state of the refrigeration system according to the real-time temperature T3.

3. A medium phase transition purging and recovery system according to claim 2, wherein: When the fluid resistance monitoring module is one pressure sensor, the pressure sensor is installed at the inlet of the pressure reducing valve and is used for detecting the real-time pressure P at the inlet of the pressure reducing valve, and the real-time pressure P can be used to calculate the actual real-time fluid resistance.

4. A medium phase transition purging and recovery system according to claim 3, wherein: The reference pressure value at the inlet of the pressure reducing valve is set as Pr.

5. A medium phase transition purging and recovery system according to claim 4, wherein: When P>Pr, the heating time of the heater is prolonged or the running frequency of the heater is increased until P<=Pr and tends to be stable. When P<=Pr and tends to be stable, the heater is turned off and the refrigeration system stops running. The reference pressure value Pr is a reference value measured at the inlet of the pressure reducing valve when the refrigerant recovery pipeline is pure and free of residues and corresponding temperature dry gas is passed in.

6. A medium phase transition purging and recovery system as claimed in claim 5, wherein: When the fluid resistance monitoring module is two pressure sensors, the two pressure sensors are respectively installed at the inlet of the pressure reducing valve and the gaseous outlet of the drain valve.

7. The medium phase transition purging and recovery system of claim 3, wherein: The real-time pressure detected at the inlet of the pressure reducing valve is P1. The real-time pressure detected at the gaseous outlet of the drain valve is P2. ​ The pressure difference between the real-time pressure P1 at the inlet of the pressure-reducing valve and the real-time pressure P2 at the gaseous outlet of the drain valve can be used to calculate the actual real-time fluid resistance.

8. A medium phase transition purging and recovery system according to claim 7, wherein: The reference pressure difference between the pressure at the inlet of the pressure-reducing valve and the pressure at the gaseous outlet of the drain valve is ΔP; When P1-P2>ΔP, the heating time of the heater is extended or the operating frequency of the heater is raised until P1-P2≤ΔP and tends to be stable; When P1-P2≤ΔP and tends to be stable, the heater is turned off and the refrigeration system is stopped.

9. A medium phase transition purging and recovery system as defined in claim 8, wherein: The reference pressure difference ΔP is a reference value measured when the refrigerant recovery pipeline is clean and free of residues and is filled with dry gas at a corresponding temperature.

10. A method of controlling a media phase transition purge and recovery system, the method comprising: The medium phase change purging and recovery system is applied to any one of claims 1-9.

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