Refrigerant circulating device for large low-temperature evaporation equipment and operation method

Abstract

The invention provides a refrigerant circulating device for large low-temperature evaporation equipment and an operation method, which can solve the problems that the whole machine is shut down and refrigerants among compressors are not uniformly distributed due to the fault of a single compressor, and realize the continuous and stable operation of the large low-temperature evaporation equipment. The system further comprises at least two independent refrigerant circulation units connected with the condenser, the independent refrigerant circulation units form independent refrigerant circulation loops respectively, each independent refrigerant circulation unit comprises a compressor, an exhaust port of the compressor is communicated with the air inlet end of the condenser, and an exhaust port of the compressor is communicated with the air outlet end of the condenser. The liquid outlet end of the condenser is connected with an inlet of the evaporator through a refrigerant on-off control valve and an electronic expansion valve, the refrigerant on-off control valve is used for controlling on-off of a pipeline, and an outlet of the evaporator is connected with an air return port of the compressor.

Description

Technical Field

[0001] This invention relates to the field of heat exchange technology for low-temperature evaporation equipment, specifically to a refrigerant circulation device and its operation method for large-scale low-temperature evaporation equipment. Background Technology

[0002] Low-temperature evaporation equipment is widely used in industries such as chemical, pharmaceutical and food. It achieves low-temperature concentration, drying or distillation of materials through evaporation and refrigeration. Large-scale low-temperature evaporation equipment has a large refrigeration capacity requirement, which is difficult to meet with a single compressor. Therefore, a solution of multiple compressors working together for refrigeration is generally adopted.

[0003] In existing equipment, a refrigeration system is often constructed by connecting multiple compressors in parallel. The refrigerant discharged from multiple compressors is mixed and enters the condenser after being connected in parallel through copper pipes to complete condensation. The liquid refrigerant is distributed to the evaporator through a common pipeline to complete evaporative refrigeration. After evaporative refrigeration is completed, the gaseous refrigerant is distributed back to each compressor for compression, thereby achieving cyclic refrigeration.

[0004] While parallel configurations can increase overall processing capacity, they present several problems in actual operation: In a parallel configuration with multiple compressors, each compressor shares the same refrigerant piping system. If any single compressor experiences abnormal oil return, lubrication failure, or other malfunctions, the entire low-temperature evaporator must typically be shut down to protect the equipment, leading to production interruptions and significant economic losses. Furthermore, in parallel piping refrigeration systems, the refrigeration pipes are not independent. Due to differences in flow resistance between branch pipes and variations in the operating conditions of each compressor, mutual interference occurs between compressors through shared piping. Even with larger condensers and more refrigerant, the refrigerant distribution within each compressor remains uneven, resulting in reduced cooling performance. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a refrigerant circulation device and operating method for large-scale low-temperature evaporation equipment, which can solve the problems of single compressor failure leading to complete machine shutdown and uneven refrigerant distribution among compressors, thereby achieving continuous and stable operation of large-scale low-temperature evaporation equipment.

[0006] This invention adopts the following technical solution: a refrigerant circulation device for a large-scale low-temperature evaporation equipment, comprising a condenser, characterized in that it further comprises an independent refrigerant circulation unit connected to the condenser, wherein at least two independent refrigerant circulation units are provided, each of the independent refrigerant circulation units constituting an independent refrigerant circulation loop, and each independent refrigerant circulation unit comprising components connected by pipelines: The compressor has its exhaust port connected to the inlet of the condenser. The liquid outlet of the condenser is connected to the inlet of the evaporator via a refrigerant on / off control valve and an electronic expansion valve. The refrigerant on / off control valve is used to control the on / off of the pipeline. The outlet of the evaporator is connected to the return port of the compressor.

[0007] Furthermore, each of the independent refrigerant circulation units also includes an oil separator, and the exhaust port of the compressor is connected to the intake end of the condenser via the oil separator; the oil separator can separate oil and gas in the exhaust of the compressor, and the lubricating oil separated by the oil separator is returned to the compressor via the oil return pipeline.

[0008] Furthermore, each of the independent refrigerant circulation units also includes a gas-liquid separator. The outlet of the evaporator is connected to the return port of the compressor via the gas-liquid separator, which is used to separate the refrigerant flowing out of the evaporator into gas and liquid.

[0009] Furthermore, each of the independent refrigerant circulation units also includes a dryer filter. The liquid outlet of the condenser is connected to the refrigerant on / off control valve via the dryer filter. The inlet of the dryer filter is connected to the refrigerant outlet of the condenser, and the outlet of the dryer filter is connected to the refrigerant on / off control valve. The dryer filter can adsorb moisture in the refrigerant and impurities in the filtration pipeline.

[0010] Furthermore, the condenser is connected to each of the independent refrigerant circulation units through independent air inlet pipes and liquid outlet pipes, and all independent refrigerant circulation units share the same condenser.

[0011] Furthermore, it also includes a control unit configured to control the compressors in the multiple independent refrigerant circulation units to start sequentially in an intermittent manner during the preheating phase of equipment startup, in order to prevent the superposition of starting currents generated when multiple compressors start simultaneously from causing equipment overload.

[0012] Furthermore, the control unit is configured to close the refrigerant on / off control valve of the corresponding faulty independent refrigerant circulation unit when a fault is detected in the compressor of any of the independent refrigerant circulation units, thereby stopping the operation of the corresponding faulty independent refrigerant circulation unit, while maintaining the continuous operation of the remaining normal independent refrigerant circulation units, in order to ensure the continuous operation of the entire low-temperature evaporation equipment.

[0013] Furthermore, the compressor, dryer filter, refrigerant on / off control valve, electronic expansion valve, oil separator, gas-liquid separator, and evaporator of the independent refrigerant circulation unit are arranged in layers along the vertical direction and connected by pipelines, and multiple independent refrigerant circulation units are arranged in parallel on one side of the condenser.

[0014] A large-scale low-temperature evaporation device includes the aforementioned refrigerant circulation device for large-scale low-temperature evaporation devices, wherein the combined cooling capacity of each independent refrigerant circulation unit can meet the total cooling demand of the low-temperature evaporation device. An operating method for the refrigerant circulation device for a large-scale low-temperature evaporation device, applied to the aforementioned refrigerant circulation device for a large-scale low-temperature evaporation device, is characterized by comprising: during a preheating stage, sequentially starting the compressors in each independent refrigerant circulation unit according to a set time interval; During operation, the operating status of each compressor and its corresponding independent refrigerant circulation unit is monitored in real time. When an abnormality is detected in a single compressor or its corresponding refrigerant circulation branch, the corresponding refrigerant circulation unit that is abnormal is shut down, while the remaining normal refrigerant circulation units continue to operate.

[0015] Compared with the prior art, the present invention sets up multiple independent refrigerant circulation units, each with an independent and closed refrigerant circuit. The pipelines of the independent refrigerant circulation units are isolated from each other and not connected. When the compressor of any independent refrigerant circulation unit fails, the corresponding independent refrigerant circulation unit can be shut down through the refrigerant on / off control valve, completely isolating it from other independent refrigerant circulation units. The remaining normal independent refrigerant circulation units are not affected in any way and can continue to maintain the refrigeration function. The large-scale low-temperature evaporation equipment can continue to operate, effectively avoiding the shutdown of the entire unit and ensuring production continuity. The refrigerant circulation device for large-scale low-temperature evaporation equipment of the present invention also solves the problem of uneven refrigerant distribution in the parallel structure of multiple compressors. In the present invention, each independent refrigerant circulation unit has an independent pipeline, and there is no mutual interference between the compressors. The refrigerant is evenly distributed, eliminating the phenomenon of uneven distribution of refrigerant due to differences in flow resistance in the parallel system. Each compressor can operate stably and efficiently near its design rated operating conditions, improving the overall refrigeration efficiency of the system and extending the service life of the compressor.

[0016] In addition, each independent refrigerant circulation unit is equipped with an evaporator and a gas-liquid separator. The heat exchange performance of the evaporator in each system is not affected by other units, ensuring stable refrigeration efficiency for each independent refrigerant circulation unit. Each independent refrigerant circulation unit is equipped with an oil separator and an independent oil return pipeline, which enables the self-circulation and return of lubricating oil from each compressor, effectively preventing the risk of compressor damage due to lack of oil. Attached Figure Description

[0017] Figure 1 This is a perspective view of the independent refrigerant circulation unit in the embodiment; Figure 2 This is a front view schematic diagram of the independent refrigerant circulation unit in the embodiment; Figure 3 This is a perspective view of the refrigerant circulation device for a large-scale low-temperature evaporation equipment in the embodiment. Figure 4This is a front view schematic diagram of the refrigerant circulation device used in a large-scale low-temperature evaporation equipment according to the present invention. Detailed Implementation

[0018] Example 1: like Figure 3 and Figure 4 As shown, this embodiment provides a refrigerant circulation device for a large-scale low-temperature evaporation equipment. In this embodiment, four independent refrigerant circulation units 100 are provided. The four independent refrigerant circulation units 100 are arranged around a condenser 200. The four independent refrigerant circulation units 100 are completely independent of each other in the refrigerant path, each forming a closed loop, and using the condenser 200 together for refrigerant condensation.

[0019] In this embodiment, the capacity of the condenser 200 is designed and selected according to the total cooling capacity of all independent refrigerant circulation units 100. The top is provided with heat dissipation medium inlet and outlet pipes, the side of the cylinder is provided with multiple refrigerant inlets, and the bottom of the condenser 200 is provided with a refrigerant outlet. After being distributed by pipelines, the refrigerant is supplied to the independent refrigerant circulation units 100 respectively. The condenser is connected to each independent refrigerant circulation unit 100 through mutually independent air inlet pipes 201 and liquid outlet pipes 202.

[0020] The structure and piping connection of the independent refrigerant circulation unit 100 are the same. A detailed explanation will be given below using one of the independent refrigerant circulation units as an example. (See [link]). Figure 1 , Figure 2 The independent refrigerant circulation unit 100 includes: The compressor 101 has an exhaust port 101A connected to the inlet of the condenser 200. The liquid outlet of the condenser 200 is connected to the inlet 104A of the evaporator 104 via a refrigerant on / off control valve 102 and an electronic expansion valve 103. The refrigerant on / off control valve 102 is used to control the on / off of the pipeline. The outlet 104B of the evaporator 104 is connected to the return port 101B of the compressor 101.

[0021] In this embodiment, the compressor 101 provides driving force for the refrigerant circulation. When the compressor 101 is working, it compresses the low-pressure refrigerant gas from the condenser 200 into high-pressure, high-temperature refrigerant gas and discharges it through the exhaust port. An oil separator 105 is also provided in the embodiment, which is located downstream of the exhaust port of the compressor 101. It uses the principle of reducing airflow speed and centrifugal separation to separate the lubricating oil mist carried in the high-pressure refrigerant gas discharged from the compressor. The separated lubricating oil flows back to the compressor 101 through the oil return pipeline, while the separated pure refrigerant gas continues to enter the condenser 200. The setting of the oil separator 105 can effectively prevent lubricating oil from entering the downstream heat exchange components, avoid oil film adhering to the pipe wall and affecting heat transfer efficiency, and at the same time ensure that the compressor is adequately lubricated, preventing abnormal oil return failures caused by insufficient oil. After the refrigerant gas enters the condenser 200, it releases heat to the outside under high pressure and condenses from gaseous state to high-pressure liquid refrigerant. The condensation heat is carried away by the medium such as cooling water or air. The independent oil separator configuration ensures that the oil return path of each compressor is completely independent and does not pass through the shared pipeline, eliminating the risk of multiple machines sharing the oil return path and further enhancing the independent operation reliability of each machine. The embodiment also includes a dryer filter 106, which is located between the outlet of the condenser 200 and the refrigerant on / off control valve 102. The dryer filter 106 is filled with molecular sieve desiccant and a filter screen. The desiccant is used to adsorb residual moisture in the pipeline; the filter screen is used to trap particulate impurities such as metal shavings and welding slag to prevent dirt from clogging and damaging the downstream electronic expansion valve 103. In this embodiment, the refrigerant on / off control valve 102 is connected in series between the dryer filter 106 and the electronic expansion valve 103 to realize the on / off control of the pipeline. The refrigerant on / off control valve 102 can be a solenoid valve, an electric ball valve, or a pneumatic ball valve. When the independent refrigerant circulation unit 100 fails, the corresponding refrigerant on / off control valve 102 is closed, isolating the independent refrigerant circulation unit 100 from the overall refrigeration system to prevent the fault from spreading to the condenser 200 side, while protecting the other normal independent refrigerant circulation units 100. When a compressor experiences an abnormal oil return or other protective shutdown, after closing the refrigerant on / off control valve 102 of the corresponding independent refrigerant circulation unit, there is no refrigerant connection path between the faulty circuit and the other circuits. The abnormal states such as pressure fluctuations and liquid supply interruptions caused by the fault are strictly limited to the circuit of the independent refrigerant circulation unit. The thermodynamic balance of the other circuits is not disturbed and can continue to operate normally. The whole machine maintains production continuity with derating power. In this embodiment, the electronic expansion valve 103 is located between the refrigerant on / off control valve 102 and the inlet of the evaporator 104. It can precisely adjust the valve opening according to parameters such as the superheat at the evaporator outlet, throttle and reduce the pressure of the high-pressure liquid refrigerant, so that the refrigerant pressure is reduced to the value corresponding to the evaporation pressure before entering the evaporator 104, thereby achieving isenthalpic expansion of the refrigerant.

[0022] In this embodiment, the evaporator 104 is a dry evaporator. The refrigerant flows in the tube side, and the process medium being cooled flows in the shell side. The low-pressure refrigerant absorbs the heat of the medium being cooled in the evaporator and completely evaporates from the liquid state to the low-pressure gaseous refrigerant. The heat absorption process of the refrigerant is the cooling process. In the dry evaporator, the refrigerant evaporates completely in the tubes. There is no situation where the refrigerant liquid surface wraps around the heat exchange tubes. The amount of refrigerant charged is less, and the refrigerant flow velocity in the tubes is higher, which is conducive to the lubricating oil flowing out with the refrigerant gas flow and returning smoothly.

[0023] The embodiment also includes a gas-liquid separator 107, which is arranged between the outlet of the evaporator 104 and the return port of the compressor 101. The refrigerant gas flowing out of the outlet of the evaporator 104 may still carry a small amount of incompletely evaporated liquid refrigerant droplets even after passing through the evaporator 104. The gas-liquid separator 107 separates the liquid refrigerant droplets from the gas flow and temporarily stores them at the bottom, allowing only pure gaseous refrigerant to enter the return port of the compressor, effectively preventing liquid refrigerant from entering the compressor.

[0024] In this embodiment, the refrigerant circulation process of a single independent refrigerant circulation unit 100 is as follows: The compressor 101 compresses the low-temperature, low-pressure refrigerant gas from the gas-liquid separator 107 into a high-temperature, high-pressure refrigerant gas, which is then discharged through the exhaust port. High-temperature and high-pressure refrigerant gas enters oil separator 105, where lubricating oil is separated and returned to compressor 101, and pure refrigerant gas enters condenser 200 inlet through pipeline; The high-temperature and high-pressure refrigerant gas releases heat to the cooling medium inside the condenser 200 and condenses into a high-pressure liquid refrigerant, which flows out from the outlet of the condenser 200. The high-pressure liquid refrigerant passes through the dryer filter 106 to remove moisture and impurities; The high-pressure liquid refrigerant flows through the refrigerant on / off control valve 102 and continues to flow to the electronic expansion valve 103 while the solenoid valve is open. Throttling and expansion process: The high-pressure liquid refrigerant is throttled and depressurized by the electronic expansion valve 103, becoming a low-pressure gas-liquid two-phase refrigerant, which then enters the inlet of the evaporator 104; The low-pressure gas-liquid two-phase refrigerant flows in the tube side of the evaporator 104, absorbs the heat from the shell side being cooled, and completely evaporates into a low-pressure gaseous refrigerant to achieve a cooling effect. The low-pressure refrigerant gas flowing out from the outlet of evaporator 104 passes through gas-liquid separator 107, where liquid refrigerant is separated, and the pure refrigerant gas enters the return port of compressor 101, completing a complete refrigerant circulation loop.

[0025] The above process circulates continuously in each independent refrigerant circulation unit 100. The refrigerant pipelines between each independent refrigerant circulation unit 100 are independent of each other, and the refrigerant does not flow across the system and does not interfere with each other.

[0026] In this invention, each independent refrigerant circulation unit forms its own independent loop, and the refrigerant circulates independently within each loop. There is no refrigerant competition between the loops, which eliminates the physical conditions that cause uneven refrigerant distribution. Each compressor always operates under independent and matched refrigerant supply conditions, resulting in high consistency of operating conditions and significantly improved uniformity of unit lifespan.

[0027] In this embodiment, the compressor 101, dryer filter 106, refrigerant on / off control valve 102, electronic expansion valve 103, oil separator 105, gas-liquid separator 107, and evaporator 104 of the independent refrigerant circulation unit are arranged vertically in layers and connected by pipelines. Multiple independent refrigerant circulation units are arranged in parallel on one side of the condenser 200, transforming horizontal space requirements into vertical space utilization. The footprint of a single independent refrigerant circulation unit is reduced compared to the traditional scattered layout, avoiding the problems of large overall span and large footprint caused by the dispersed arrangement of equipment. The oil separator outlet and dryer filter inlet of each refrigerant circulation unit are directly connected to the corresponding interface of the condenser at close range, avoiding long refrigerant main pipelines caused by the dispersed arrangement of the condenser and refrigerant circulation units, eliminating refrigerant pressure loss and temperature loss in the main pipeline, and ensuring consistent condensing conditions of each independent refrigerant circulation unit. In terms of physical space and pipeline design, the consistency of each independent refrigerant circulation unit is ensured, eliminating uneven refrigerant distribution from the layout level.

[0028] In this embodiment, a control unit is also included. The control unit is configured to control the compressors 101 in multiple independent refrigerant circulation units to start sequentially in an intermittent manner during the preheating phase of equipment startup, in order to prevent the superposition of starting currents generated when multiple compressors start simultaneously from causing equipment overload.

[0029] During the system preheating phase, the control unit starts the compressors 101 in the four independent refrigerant circulation units 100 in an interval sequence. Specifically, after the first compressor starts, there is a preset delay before the second compressor starts, for example, 30 to 120 seconds, which can be adjusted according to the specific configuration of the equipment, and so on, until all compressors have started.

[0030] The starting current of a compressor is usually 5 to 8 times the rated operating current. If multiple compressors start at the same time, the peak value of the starting current of each compressor is extremely large after superposition, which may exceed the rated current capacity of the power distribution system, causing the circuit breaker to trip or the motor to burn out, resulting in equipment overload faults. By starting at intervals, only one compressor is in the starting state at a time, which can effectively control the peak current and ensure the safety and reliability of the system startup process.

[0031] In this embodiment, the control unit is configured to close the refrigerant on / off control valve 102 of the corresponding faulty independent refrigerant circulation unit when the compressor 101 of any independent refrigerant circulation unit detects a fault, thereby stopping the operation of the corresponding faulty independent refrigerant circulation unit 100, while maintaining the continuous operation of the remaining normal independent refrigerant circulation units, thus ensuring the continuous operation of the entire low-temperature evaporation equipment.

[0032] During normal system operation, the control unit monitors the operating parameters of each independent refrigerant circulation unit 100 in real time, including suction and discharge pressure, discharge temperature, motor current, oil level, etc. These operating parameters can be obtained through built-in sensors or set sensors, including pressure sensors, temperature sensors, current transformers, and oil level sensors. When an abnormality is detected in the compressor 101 of a certain independent refrigerant circulation unit, such as abnormal oil return, compressor overload, refrigerant leakage, or compressor discharge temperature exceeding the limit: The control unit sends a closing command to the refrigerant on / off control valve 102 of the corresponding independent refrigerant circulation unit 100, and the refrigerant on / off control valve 102 closes, cutting off the refrigerant supply line of the corresponding independent refrigerant circulation unit. The control unit simultaneously stops the compressor 101 of the corresponding independent refrigerant circulation unit 100, thus completely shutting down the corresponding independent refrigerant circulation unit 100; The other three normal independent refrigerant circulation units 100 were unaffected and continued to operate normally. The large low-temperature evaporation equipment continued to operate at approximately 75% of its cooling capacity, awaiting maintenance personnel to inspect and repair the faulty independent refrigerant circulation unit.

[0033] During the above-mentioned fault response process, since each independent refrigerant circulation unit 100 is independently isolated from each other, after the refrigerant on / off control valve of the faulty independent refrigerant circulation unit 100 is closed, the refrigerant in its pipeline is sealed in the corresponding independent refrigerant circulation unit 100 and will not flow into other independent refrigerant circulation units 100, nor will it affect the normal condensation process of other independent refrigerant circulation units 100 on the condenser 200 side. This physically ensures fault isolation and eliminates the risk of the entire unit shutting down due to a single compressor failure.

[0034] Example 2: This embodiment has the same overall concept as Embodiment 1, except that there are three independent refrigerant circulation units 100 in this embodiment. Each independent refrigerant circulation unit 100 still includes an evaporator 104, a gas-liquid separator 107, a compressor 101, an oil separator 105, a dryer filter 106, a refrigerant on / off control valve 102, and an electronic expansion valve 103, and forms its own independent refrigerant circulation loop according to the same connection relationship as in Embodiment 1.

[0035] The refrigerant circulation process, start-up control method, and fault response method in this embodiment are the same as in Embodiment 1, and will not be repeated here.

[0036] The number of independent refrigerant circulation units 100 in this invention is not limited to... Figure 3 The four units shown can be modularly added or removed based on the evaporation load, processing capacity requirements, and installation space of the large-scale low-temperature evaporation equipment. When the equipment is configured with three independent refrigerant circulation units 1, the three compressors 101 can still be started intermittently during the preheating stage; if one of the compressors 101 malfunctions, the other two independent refrigerant circulation units 100 can continue to work, maintaining part of the equipment's heat exchange capacity.

[0037] As can be seen from Embodiment 1 and Embodiment 2, the technical focus of the present invention is not on the specific number of independent refrigerant circulation units 100, but on the fact that each compressor 101 corresponds to a complete and independent refrigerant circulation unit 100, and multiple independent refrigerant circulation units 100 are combined to form an overall structure adapted to large-scale low-temperature evaporation equipment. As long as the above-mentioned independent closed-loop combination concept is adopted, it should fall within the protection scope of the present invention.

[0038] Example 3: In an embodiment of the present invention, a large-scale low-temperature evaporation device is also provided, including the above-mentioned refrigerant circulation device for a large-scale low-temperature evaporation device, wherein the evaporation chamber of the low-temperature evaporation device is heat-exchange connected to the evaporator of each independent refrigerant circulation unit.

[0039] In actual operation, the evaporators of each independent refrigerant circulation unit work together to provide cooling to the evaporation chamber, meeting the total cooling demand of the large-scale low-temperature evaporation equipment. When the equipment is operating under partial load, some independent refrigerant circulation units can be selectively activated to achieve graded adjustment of cooling capacity and improve the energy efficiency ratio under partial load conditions.

[0040] Example 4: In an embodiment of the present invention, a method for operating a refrigerant circulation device for a large-scale low-temperature evaporation equipment is also provided, which is applied to the above-mentioned refrigerant circulation device for a large-scale low-temperature evaporation equipment, including: during the preheating stage, sequentially starting the compressors in each independent refrigerant circulation unit according to a set time interval; During operation, the operating status of each compressor and its corresponding independent refrigerant circulation unit is monitored in real time. When an abnormality is detected in a single compressor or its corresponding refrigerant circulation branch, the corresponding refrigerant circulation unit that is abnormal is shut down, while the remaining normal refrigerant circulation units continue to operate.

[0041] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0042] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A refrigerant circulation device for a large-scale low-temperature evaporation equipment, comprising a condenser, characterized in that, It also includes independent refrigerant circulation units connected to the condenser, with at least two such independent refrigerant circulation units, each forming an independent refrigerant circulation loop. Each independent refrigerant circulation unit includes components connected via piping: The system includes a compressor, an electronic expansion valve, and an evaporator. The compressor's exhaust port is connected to the condenser's inlet. The condenser's liquid outlet is connected to the evaporator's inlet via a refrigerant on / off control valve and the electronic expansion valve. The refrigerant on / off control valve is used to control the on / off of the pipeline. The evaporator's outlet is connected to the compressor's return port.

2. A refrigerant circulation device for a large-scale low-temperature evaporation equipment according to claim 1, characterized in that: The independent refrigerant circulation unit also includes an oil separator. The exhaust port of the compressor is connected to the intake end of the condenser via the oil separator. The oil separator can separate oil and gas in the exhaust of the compressor, and the lubricating oil separated by the oil separator is returned to the compressor via the oil return pipeline.

3. A refrigerant circulation device for a large-scale low-temperature evaporation equipment according to claim 2, characterized in that: The independent refrigerant circulation unit also includes a gas-liquid separator. The outlet of the evaporator is connected to the return port of the compressor via the gas-liquid separator, which is used to separate the refrigerant flowing out of the evaporator into gas and liquid.

4. A refrigerant circulation device for a large-scale low-temperature evaporation equipment according to claim 3, characterized in that: The independent refrigerant circulation unit also includes a dryer filter. The liquid outlet of the condenser is connected to the refrigerant on / off control valve via the dryer filter. The inlet of the dryer filter is connected to the refrigerant outlet of the condenser, and the outlet of the dryer filter is connected to the refrigerant on / off control valve. The dryer filter can adsorb moisture in the refrigerant and impurities in the filtration pipeline.

5. A refrigerant circulation device for a large-scale low-temperature evaporation equipment according to claim 1, characterized in that: The condenser is connected to each of the independent refrigerant circulation units through independent air inlet and liquid outlet pipes, and all independent refrigerant circulation units share the same condenser.

6. A refrigerant circulation device for a large-scale low-temperature evaporation equipment according to claim 1, characterized in that: It also includes a control unit configured to control the compressors in the multiple independent refrigerant circulation units to start sequentially in an intermittent manner during the preheating phase of equipment startup, in order to prevent the superposition of starting currents generated when multiple compressors start simultaneously from causing equipment overload.

7. A refrigerant circulation device for a large-scale low-temperature evaporation equipment according to claim 6, characterized in that: The control unit is configured to, when a compressor of any of the independent refrigerant circulation units detects a fault, control the refrigerant on / off control valve of the corresponding faulty independent refrigerant circulation unit to close, thereby stopping the operation of the corresponding faulty independent refrigerant circulation unit, while maintaining the continuous operation of the remaining normal independent refrigerant circulation units.

8. A refrigerant circulation device for a large-scale low-temperature evaporation equipment according to claim 4, characterized in that: The compressor, dryer filter, refrigerant on / off control valve, electronic expansion valve, oil separator, gas-liquid separator, and evaporator of the independent refrigerant circulation unit are arranged in layers along the vertical direction and connected by pipelines. Multiple independent refrigerant circulation units are arranged in parallel on one side of the condenser.

9. A large-scale low-temperature evaporation device, characterized in that: The device includes a refrigerant circulation device for large-scale low-temperature evaporation equipment as described in any one of claims 1 to 8, wherein the combined cooling capacity of each independent refrigerant circulation unit can meet the total cooling demand of the low-temperature evaporation equipment.

10. A method for operating a refrigerant circulation device for a large-scale low-temperature evaporation equipment, applied to the refrigerant circulation device for a large-scale low-temperature evaporation equipment as described in any one of claims 1 to 8, characterized in that, include: During the preheating phase, the compressors in each independent refrigerant circulation unit are started sequentially according to the set time intervals; During operation, the operating status of each compressor and its corresponding independent refrigerant circulation unit is monitored in real time. When an abnormality is detected in a single compressor or its corresponding refrigerant circulation branch, the corresponding refrigerant circulation unit that is abnormal is shut down, while the remaining normal refrigerant circulation units continue to operate.

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