A cryogenic refrigeration unit control system

Abstract

The application discloses a low-temperature refrigerating unit control system, and relates to the technical field of refrigeration, which comprises a compressor, an oil separator, an oil cooler, an oil pump, a condenser, an economizer, an evaporator, a detection device and a control device. The oil pump is arranged between the liquid outlet of the oil cooler and the oil inlet of the compressor. The evaporator is communicated with the liquid outlet of the economizer, the gas outlet of the evaporator is communicated with the gas inlet of the compressor, the water inlet of the evaporator is connected with a chilled water supply device, and the water outlet of the evaporator is connected with a process equipment. The control device is used for regulating the water outlet temperature of the evaporator according to the process temperature of the process equipment, and is matched with the driving of the compressor, the oil pump, the circulating water supply device and the chilled water supply device to run, so that the actual water outlet temperature of the evaporator reaches the water outlet temperature of the evaporator. The system can realize the close combination of the refrigerating unit operation and the process operation, make the equipment operation index meet the requirements of the equipment itself and the process operation, and realize digital automatic control.

Description

Technical Field

[0001] This invention relates to the field of refrigeration technology, and more specifically, to a control system for a cryogenic refrigeration unit. Background Technology

[0002] In the petrochemical industry, with the continuous growth of national strength, the reserve and use of non-renewable energy resources have become dominant, especially oil resources. In recent years, my country has transformed from oil refining to petrochemicals, carrying out refined deep processing. With the diversification of processes and products, more and more production facilities need to use cryogenic refrigeration units to meet the process temperature requirements of specific materials. When the unit load is relatively high, operators cannot accurately operate the refrigeration unit load position, and the unit load fluctuates greatly, which may lead to the unit triggering interlock shutdown, resulting in a high risk of equipment operation.

[0003] In summary, how to achieve a close integration between the operation of the refrigeration unit and the process operation, so that the equipment operation indicators meet the requirements of the equipment itself and the process operation, and realize digital automatic control, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a control system for a cryogenic refrigeration unit that can closely integrate the operation of the refrigeration unit with the process operation, ensuring that the equipment operating indicators meet the requirements of both the equipment itself and the process operation, and realizing digital automatic control.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A cryogenic refrigeration unit control system, comprising:

[0007] A compressor containing refrigeration oil, the compressor being used to compress gaseous refrigerant;

[0008] An oil separator is connected to the air outlet of the compressor, and the liquid outlet of the oil separator is connected to the oil inlet of the compressor.

[0009] An oil cooler, which is connected to the liquid outlet of the oil separator;

[0010] An oil pump is located between the outlet of the oil cooler and the inlet of the compressor;

[0011] A condenser, which is connected to the outlet of the oil separator and the outlet of the oil cooler respectively, and the condenser is connected to;

[0012] An economizer, which is connected to the liquid outlet of the condenser;

[0013] An evaporator is connected to the liquid outlet of the economizer, the gas outlet of the evaporator is connected to the gas inlet of the compressor, the water inlet of the evaporator is connected to the chilled water supply device, and the water outlet of the evaporator is connected to the process equipment.

[0014] A detection device for detecting the process temperature of the process equipment and the inlet and outlet water temperatures of the evaporator;

[0015] The control device is connected to the compressor, the oil pump, the circulating water supply device, and the chilled water supply device. The control device is used to adjust the outlet water temperature of the evaporator according to the process temperature of the process equipment, and to drive the compressor, the oil pump, the circulating water supply device, and the chilled water supply device to operate so that the actual outlet water temperature of the evaporator reaches the outlet water temperature of the evaporator.

[0016] In one embodiment, a first pipeline is provided between the outlet of the evaporator and the process equipment. The first pipeline is provided with a second flow sensor for detecting the flow rate of chilled water, a third regulating valve for adjusting the flow rate of chilled water, and a second temperature sensor for detecting the outlet temperature of the evaporator.

[0017] A second pipeline is provided between the chilled water supply device and the water inlet of the evaporator. The second pipeline is provided with a fourth regulating valve for adjusting the chilled water flow rate and a first temperature sensor for detecting the water inlet temperature of the evaporator.

[0018] The evaporator is equipped with a fourth pressure sensor for detecting the suction pressure of the evaporator and a first level gauge for detecting the liquid level of the evaporator; the second flow sensor, the third regulating valve, the first temperature sensor, the second temperature sensor, the fourth regulating valve, the fourth pressure sensor, and the first level gauge are all connected to the control device.

[0019] In one embodiment, the outlet of the evaporator is connected to the inlet of the compressor via a third pipeline, and a fifth shut-off valve is provided on the third pipeline;

[0020] The liquid outlet of the evaporator is connected to the oil inlet of the compressor through a fourth pipeline. The fourth pipeline is equipped with a fifth regulating valve for adjusting the flow rate of the refrigeration oil. The fifth regulating valve is connected to the control device.

[0021] In one embodiment, the oil separator is provided with a second pressure sensor for detecting the pressure of the oil separator and a second level gauge for detecting the liquid level of the oil separator;

[0022] A fifth pipeline is provided between the liquid outlet of the oil separator and the oil cooler. A seventh shut-off valve is provided on the fifth pipeline. The liquid outlet of the oil separator and the oil inlet of the compressor are connected through a sixth pipeline. A sixth regulating valve for adjusting the flow rate of the refrigeration oil is provided on the sixth pipeline.

[0023] The oil pump is equipped with a first pressure sensor for detecting the oil pressure of the oil pump. A sixth pipeline is provided between the oil pump and the oil inlet of the compressor. A sixth shut-off valve is provided on the sixth pipeline. The second pressure sensor, the second level gauge, the sixth regulating valve, and the first pressure sensor are all connected to the control device.

[0024] In one embodiment, a seventh pipeline is provided between the outlet of the oil separator and the inlet of the condenser, and a first shut-off valve is provided on the seventh pipeline;

[0025] An eighth pipe is provided between the air outlet of the oil cooler and the air inlet of the condenser, and a ninth pipe is provided between the air outlet of the condenser and the air inlet of the oil cooler.

[0026] In one embodiment, a tenth pipeline is provided between the outlet of the condenser and the circulating water supply device. The tenth pipeline is provided with a first flow sensor for detecting the circulating water flow rate of the circulating water supply device, a first regulating valve for adjusting the circulating water flow rate, and a fifth temperature sensor for detecting the outlet water temperature of the condenser.

[0027] An eleventh pipeline is provided between the water inlet of the condenser and the circulating water supply device. The eleventh pipeline is provided with a second regulating valve for adjusting the flow rate of the circulating water and a fourth temperature sensor for detecting the water inlet temperature of the condenser.

[0028] The condenser is equipped with a third pressure sensor for detecting the exhaust pressure of the condenser. The first flow sensor, the first regulating valve, the fifth temperature sensor, the second regulating valve, the fourth temperature sensor, and the third pressure sensor are all connected to the control device.

[0029] In one embodiment, a twelfth pipeline is provided between the outlet of the economizer and the inlet of the compressor, and a thirteenth and fourteenth pipelines are connected in parallel between the liquid outlet of the economizer and the evaporator, with a second shut-off valve provided on the thirteenth pipeline;

[0030] The fourteenth pipeline is equipped with a seventh regulating valve for adjusting the refrigerant flow rate. A third shut-off valve is provided between the economizer and the seventh regulating valve. A fourth shut-off valve is provided between the seventh regulating valve and the evaporator. The seventh regulating valve is connected to the control device.

[0031] In one embodiment, the compressor includes a screw compressor.

[0032] In one embodiment, the control mode of the control device includes a manual adjustment mode, a semi-automatic mode, and a remote fully automatic mode. The manual adjustment mode includes adjusting the outlet water temperature of the evaporator according to the process temperature of the process equipment, manually operating the compressor to load and unload, and manually inputting the load value of the compressor to drive the compressor, the oil pump, the circulating water supply device, and the chilled water supply device to operate, so that the actual outlet water temperature of the evaporator reaches the outlet water temperature of the evaporator.

[0033] The semi-automatic mode includes adjusting the outlet water temperature of the evaporator according to the process temperature of the process equipment, manually operating the temperature adjustment button to increase or decrease the outlet water temperature of the evaporator, and the compressor automatically loading or unloading at preset intervals to cooperate in driving the operation of the compressor, the oil pump, the circulating water supply device and the chilled water supply device, so that the actual outlet water temperature of the evaporator reaches the outlet water temperature of the evaporator.

[0034] The remote fully automatic mode includes adjusting the outlet water temperature of the evaporator according to the process temperature of the process equipment, and controlling the compressor to automatically load or unload at preset intervals according to the outlet water temperature of the evaporator, so as to drive the operation of the compressor, the oil pump, the circulating water supply device and the chilled water supply device.

[0035] When using the cryogenic refrigeration unit control system provided by this invention, firstly, the compressor compresses the gaseous refrigerant. The lubricating oil in the refrigeration oil helps increase the pressure and temperature of the refrigerant. Then, the gaseous refrigerant and refrigeration oil enter the oil separator. The gaseous refrigerant passes through the oil separator and enters the downstream path (i.e., through the pipeline into the next component), while the liquid refrigeration oil enters the liquid storage tank of the oil separator, achieving separation. Simultaneously, the liquid refrigerant enters the tube side of the oil cooler, and the refrigeration oil enters the shell side. Through temperature and pressure changes, the liquid refrigerant is converted into a gaseous refrigerant. The refrigerant absorbs heat from the refrigeration oil in the tube side and evaporates into a gaseous refrigerant, thus reducing the temperature of the refrigeration oil. The refrigeration oil is then pressurized by the oil pump and enters the compressor for lubrication.

[0036] Subsequently, the high-temperature, high-pressure gaseous refrigerant (from the oil separator and oil cooler) enters the shell side of the condenser. After heat exchange with the circulating water, it liquefies and releases heat as it cools down through the heat exchange. At this time, the circulating water in the tube side of the condenser absorbs some heat, causing its temperature to rise. The gaseous refrigerant condenses into a liquid refrigerant, which accumulates at the bottom of the condenser and enters the downstream path. Then, the liquid refrigerant enters the economizer for further deep cooling. Finally, the low-temperature, low-pressure liquid refrigerant enters the shell side of the evaporator. The liquid refrigerant exchanges heat with the chilled water, cooling down through the chilled water, and undergoes a vaporization endothermic physical reaction. At this time, the chilled water in the tube side of the evaporator loses heat, its temperature decreases, and low-temperature chilled water is output for use by the process equipment. The gaseous refrigerant enters the compressor, forming a cycle.

[0037] This system is a closed-loop system that outputs chilled water after continuous operation. The system mainly realizes the process of heat release and heat absorption, and relies on two media, chilled water and circulating water, to maintain the system's heat balance and realize the chilled water production process. The main function of this system is to control the operating pressure of the evaporator and condenser to not exceed the specified range. Based on the physical and chemical properties of the refrigerant, the corresponding temperature can be calculated from the pressure, thereby reviewing the system's heat exchange efficiency and improving the system's operating efficiency.

[0038] During operation, this system regulates the evaporator's outlet water temperature based on the process temperature of the equipment, and coordinates with the compressor, oil pump, circulating water supply device, and chilled water supply device to ensure the evaporator's actual outlet water temperature reaches the required temperature. In other words, the control device utilizes a digital model, guided by the target result of the evaporator's outlet water temperature (the required chilled water temperature), to control the coordinated operation of each device, ensuring the output chilled water temperature meets the process production requirements and achieving coordinated operation between the refrigeration unit (including the compressor, condenser, and evaporator) and the process equipment. Furthermore, based on the stable operation of this system, the digital control system enhances the inherent safety of the system equipment, eliminates the risk of equipment downtime due to human error, improves operator efficiency and skill levels, outputs standard operating procedures, and meets the needs of the process equipment.

[0039] In summary, the cryogenic refrigeration unit control system provided by this invention can achieve close integration of refrigeration unit operation and process operation, so that the equipment operation indicators meet the requirements of the equipment itself and the process operation, and realize digital automatic control. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the control system for the cryogenic refrigeration unit provided by the present invention.

[0042] Figure label:

[0043] 1-Compressor; 2-Oil separator; 3-Oil cooler; 4-Oil pump; 5-Condenser; 6-Econverter; 7-Evaporator; 8-Process equipment;

[0044] K1 - First regulating valve; K2 - Second regulating valve; K3 - Third regulating valve; K4 - Fourth regulating valve; K5 - Fifth regulating valve; K6 - Sixth regulating valve; K7 - Seventh regulating valve;

[0045] F1 - First shut-off valve; F2 - Second shut-off valve; F3 - Third shut-off valve; F4 - Fourth shut-off valve; F5 - Fifth shut-off valve; F6 - Sixth shut-off valve; F7 - Seventh shut-off valve. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] The core of this invention is to provide a control system for a cryogenic refrigeration unit, which can closely integrate the operation of the refrigeration unit with the process operation, so that the equipment operation indicators meet the requirements of the equipment itself and the process operation, and realize digital automatic control.

[0048] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the control system for the cryogenic refrigeration unit provided by the present invention.

[0049] This specific embodiment provides a control system for a cryogenic refrigeration unit, including:

[0050] Compressor 1, which contains refrigeration oil, is used to compress gaseous refrigerant;

[0051] Oil separator 2 is connected to the gas outlet of compressor 1, and the liquid outlet of oil separator 2 is connected to the oil inlet of compressor 1. Oil separator 2 is used to separate gaseous refrigerant and refrigeration oil.

[0052] Oil cooler 3 is connected to the liquid outlet of oil separator 2. Oil cooler 3 is used to evaporate the liquid refrigerant into the gaseous refrigerant and reduce the temperature of refrigeration oil.

[0053] Oil pump 4 is located between the liquid outlet of oil cooler 3 and the oil inlet of compressor 1;

[0054] The condenser 5 is connected to the outlet of the oil separator 2 and the outlet of the oil cooler 3 respectively. The condenser 5 is also connected to the circulating water supply device. The condenser 5 is used to condense the gaseous refrigerant into the liquid refrigerant.

[0055] Economizer 6 is connected to the liquid outlet of condenser 5, and the air outlet of economizer 6 is connected to the air inlet of compressor 1.

[0056] Evaporator 7 is connected to the liquid outlet of economizer 6. Evaporator 7 is used to evaporate liquid refrigerant. The gas outlet of evaporator 7 is connected to the gas inlet of compressor 1. The water inlet of evaporator 7 is connected to chilled water supply device. The water outlet of evaporator 7 is connected to process equipment 8 to output low-temperature chilled water to process equipment 8. For example, chilled water releases heat in evaporator 7 and refrigerant absorbs heat, causing the temperature of chilled water to drop from 20°C to 13°C. At this time, chilled water is output to meet the operation of process equipment 8. The gaseous refrigerant enters the compressor 1 inlet of the refrigeration unit. After being compressed and pressurized, the gaseous refrigerant recurs and circulates.

[0057] The detection device is used to detect the process temperature of the process equipment 8 and the inlet and outlet water temperatures of the evaporator 7.

[0058] The control unit connects to compressor 1, oil pump 4, circulating water supply device, and chilled water supply device. The control unit regulates the outlet water temperature T2 of evaporator 7 based on the process temperature T5 of process equipment 8, and coordinates with the operation of compressor 1, oil pump 4, circulating water supply device, and chilled water supply device to ensure that the actual outlet water temperature of evaporator 7 reaches the outlet water temperature T2. In other words, the control unit belongs to a central control model, requiring the establishment of a relationship table between process temperature T5 and evaporator 7 outlet water temperature T2, ensuring the two temperatures are close, thereby enabling the refrigeration unit to directly control the process temperature T5 and meet the production requirements of process equipment 8.

[0059] It should be noted that the structural diagram of this system is as follows: Figure 1As shown, the main flow process of the refrigerant is compressor 1 → oil separator 2 → shell side of condenser 5 → tube side of economizer 6 → shell side of evaporator 7 → compressor 1; the main flow process of the refrigeration oil is oil separator 2 → shell side of oil cooler 3 → oil pump 4 → compressor 1 → oil separator 2; the main flow process of the chilled water is chilled water supply device → tube side of evaporator 7 → process equipment 8; the main flow process of the circulating water is circulating water supply device → tube side of condenser 5 → circulating water supply device.

[0060] In one embodiment, a first pipeline is provided between the outlet of the evaporator 7 and the process equipment 8. The first pipeline is equipped with a second flow sensor for detecting the chilled water flow rate L2, a third regulating valve K3 for adjusting the chilled water flow rate, and a second temperature sensor for detecting the outlet water temperature T2 of the evaporator 7. A second pipeline is provided between the chilled water supply device and the inlet of the evaporator 7. The second pipeline is equipped with a fourth regulating valve K4 for adjusting the chilled water flow rate and a first temperature sensor for detecting the inlet water temperature T1 of the evaporator 7. The evaporator 7 is equipped with a fourth pressure sensor for detecting the suction pressure P4 of the evaporator 7 and a first level gauge for detecting the liquid level H1 of the evaporator 7. The second flow sensor, the third regulating valve K3, the first temperature sensor, the second temperature sensor, the fourth regulating valve K4, the fourth pressure sensor, and the first level gauge are all connected to the control device.

[0061] Therefore, the control device can obtain the inlet water temperature T1 and outlet water temperature T2 of the evaporator 7 (that is, the temperature of the low-temperature chilled water delivered to the process equipment 8) in real time based on the temperature detection signals of the first and second temperature sensors, obtain the chilled water flow rate based on the flow detection signal of the second flow sensor, and determine whether the evaporator 7 is operating normally based on the pressure detection signal of the fourth pressure sensor and the liquid level detection signal of the first liquid level gauge. Then, it adjusts the opening of the third regulating valve K3 and the fourth regulating valve K4 according to the chilled water temperature required by the process equipment 8, so that the detected outlet water temperature T2 of the evaporator 7 is equivalent to the required chilled water temperature.

[0062] In one embodiment, the outlet of the evaporator 7 is connected to the inlet of the compressor 1 via a third pipeline, which is equipped with a fifth shut-off valve F5; the liquid outlet of the evaporator 7 is connected to the oil inlet of the compressor 1 via a fourth pipeline, which is equipped with a fifth regulating valve K5 for adjusting the flow rate of the refrigerant oil. The fifth regulating valve K5 is connected to a control device. By controlling the opening degree of the fifth regulating valve K5, the control device can change the flow rate of the refrigerant oil in the fourth pipeline, thereby regulating and controlling the refrigeration process.

[0063] In one embodiment, the oil separator 2 is equipped with a second pressure sensor for detecting the pressure P2 of the oil separator 2 and a second level gauge for detecting the liquid level H2 of the oil separator 2; a fifth pipeline is provided between the liquid outlet of the oil separator 2 and the oil cooler 3, and a seventh shut-off valve F7 is provided on the fifth pipeline; the liquid outlet of the oil separator 2 and the oil inlet of the compressor 1 are connected through a sixth pipeline, and a sixth regulating valve K6 is provided on the sixth pipeline for regulating the flow rate of the refrigeration oil; the oil pump 4 is equipped with a first pressure sensor for detecting the oil pressure P1 of the oil pump 4, and a sixth pipeline is provided between the oil pump 4 and the oil inlet of the compressor 1, and a sixth shut-off valve F6 is provided on the sixth pipeline; the second pressure sensor, the second level gauge, the sixth regulating valve K6, and the first pressure sensor are all connected to the control device.

[0064] Therefore, the control device can determine in real time whether the oil separator 2 is operating normally based on the pressure detection signal from the second pressure sensor and the liquid level detection signal from the second liquid level gauge, and determine whether the oil pump 4 has reached the pumping pressure based on the oil pressure detection signal from the first pressure sensor, thus determining whether the oil pump 4 is operating normally. Furthermore, the control device can adjust the opening of the sixth regulating valve K6 to regulate the amount of oil entering the oil cooler 3.

[0065] In one embodiment, a seventh pipeline is provided between the outlet of the oil separator 2 and the inlet of the condenser 5, and a first shut-off valve F1 is provided on the seventh pipeline. Therefore, the gaseous refrigerant separated by the oil separator 2 can enter the condenser 5 through the first shut-off valve F1. An eighth pipeline is provided between the outlet of the oil cooler 3 and the inlet of the condenser 5. Therefore, the gaseous refrigerant flowing out of the outlet of the oil cooler 3 can also enter the condenser 5 through the eighth pipeline. A ninth pipeline is provided between the outlet of the condenser 5 and the inlet of the oil cooler 3. That is, the liquid refrigerant condensed by the condenser 5 can flow into the oil cooler 3 through the ninth pipeline to exchange heat with the refrigeration oil. The liquid refrigerant absorbs the heat of the refrigeration oil to reduce the temperature of the refrigeration oil. The liquid refrigerant can also evaporate into gaseous refrigerant and flow back into the condenser 5 through the eighth pipeline.

[0066] In one embodiment, a tenth pipeline is provided between the outlet of the condenser 5 and the circulating water supply device. The tenth pipeline is provided with a first flow sensor for detecting the circulating water flow rate L1 of the circulating water supply device, a first regulating valve K1 for regulating the circulating water flow rate L1, and a fifth temperature sensor for detecting the outlet water temperature T5 of the condenser 5.

[0067] An eleventh pipeline is provided between the water inlet of the condenser 5 and the circulating water supply device. The eleventh pipeline is equipped with a second regulating valve K2 for regulating the circulating water flow L1 and a fourth temperature sensor for detecting the water inlet temperature T4 of the condenser 5.

[0068] The condenser 5 is equipped with a third pressure sensor for detecting the exhaust pressure P3 of the condenser 5. The first flow sensor, the first regulating valve K1, the fifth temperature sensor, the second regulating valve K2, the fourth temperature sensor, and the third pressure sensor are all connected to the control device.

[0069] Therefore, the control device can obtain the outlet water temperature T5 of the condenser 5 in real time based on the temperature detection signal of the fifth temperature sensor, obtain the inlet water temperature T4 of the condenser 5 in real time based on the temperature detection signal of the fourth temperature sensor, obtain the circulating water flow rate L1 of the circulating water supply device based on the flow detection signal of the first flow sensor, determine whether the exhaust pressure P3 of the condenser 5 is normal based on the pressure detection signal of the third pressure sensor, and adjust the opening of the first regulating valve K1 and the second regulating valve K2 according to the required circulating temperature and flow rate of the condenser 5 so that the circulating water meets the condensation requirements of the condenser 5, thereby making the outlet water temperature T2 of the evaporator 7 comparable to the required chilled water temperature.

[0070] In one embodiment, a twelfth pipe is provided between the outlet of the economizer 6 and the inlet of the compressor 1; a thirteenth pipe and a fourteenth pipe are connected in parallel between the liquid outlet of the economizer 6 and the evaporator 7; a second shut-off valve F2 is provided on the thirteenth pipe; a seventh regulating valve K7 for adjusting the refrigerant flow is provided on the fourteenth pipe; a third shut-off valve F3 is provided between the economizer 6 and the seventh regulating valve K7; a fourth shut-off valve F4 is provided between the seventh regulating valve K7 and the evaporator 7; and the seventh regulating valve K7 is connected to a control device. Therefore, the control device can regulate the flow rate of refrigerant flowing from the economizer 6 and into the evaporator 7 by controlling the opening degree of the seventh regulating valve K7.

[0071] In one embodiment, the compressor 1 includes a screw compressor 1. The screw compressor 1 has a simple structure, few vulnerable parts, can operate under large pressure differences or pressure ratios with low discharge temperature, is not sensitive to the presence of a large amount of lubricating oil in the refrigerant (often referred to as wet stroke), has good gas delivery volume regulation, and is widely used in refrigeration equipment such as refrigeration, cold storage, air conditioning, and chemical processes.

[0072] In one embodiment, the control device includes a manual adjustment mode, a semi-automatic mode, and a remote fully automatic mode. The control device is equivalent to a control unit module for the operation of the chiller unit. Through a PLC control system, it inputs a control calculation model to control the chiller unit's load from 0-100%, i.e., controls the chiller unit's cooling capacity. The manual adjustment mode includes adjusting the evaporator 7's outlet water temperature T2 according to the process temperature T5 of the process equipment 8, manually operating the compressor 1 for loading and unloading, and manually inputting the compressor 1's load value to coordinate the operation of the compressor 1, oil pump 4, circulating water supply device, and chilled water supply device, so that the actual outlet water temperature of the evaporator 7 reaches the evaporator 7's outlet water temperature T2.

[0073] It should be noted that the manual debugging mode is equivalent to the first mode of this system. It is a manual operation requiring on-site personnel to operate the chiller unit's control device (e.g., the PLC display screen) to manually select start-up and manually control the loading and unloading of the chiller unit's load (i.e., the load of compressor 1). Based on the operating temperature of process equipment 8, a specific load value is output. For example, if the process requires the chilled water outlet temperature of the chiller unit to be controlled at 8℃, increasing the load to 65% will result in significant load fluctuations due to the inability to accurately control the unit's adjustment. This operation necessitates manual on-site operation of the PLC display screen.

[0074] For example, the first step is to click "Start Oil Pump 4" on the PLC display screen, and after 10 seconds; the second step is to click "Start Compressor 1", and compressor 1 will start running; the third step is to click "Load", and adjust the load position from 1% to 100% according to the refrigeration unit load. After this adjustment, the circulating water flow rate needs to be adjusted synchronously according to the exhaust pressure value to control the exhaust pressure within the specified operating range, ensuring that the refrigeration unit operates normally and that the actual outlet water temperature of evaporator 7 is equivalent to the required outlet water temperature T2 of evaporator 7.

[0075] The semi-automatic mode includes adjusting the outlet water temperature T2 of the evaporator 7 according to the process temperature T5 of the process equipment 8, manually operating the temperature adjustment button to increase or decrease the outlet water temperature T2 of the evaporator 7, and the compressor 1 automatically loading or unloading at preset intervals to cooperate with the operation of the compressor 1, oil pump 4, circulating water supply device and chilled water supply device, so that the actual outlet water temperature of the evaporator 7 reaches the outlet water temperature T2 of the evaporator 7.

[0076] It should be noted that the semi-automatic mode can be referred to as the second mode of this system. This second mode combines manual and digital automatic operation. When the chiller unit is operating in this mode, if the unit's operating load needs to be adjusted, only the outlet water temperature T2 of evaporator 7 needs to be adjusted. There is no need to manually start and stop the load, thus avoiding excessive load changes in the chiller unit. This mode has a pre-set logic (that is, the parameters of each component are correlated, and the correlation has been programmed into the control device, making parameter changes interactive), so adjusting the outlet water temperature T2 of evaporator 7 is sufficient.

[0077] The PLC operation display screen has two buttons for increasing and decreasing the temperature. Each time the "+" button is pressed, the outlet water temperature T2 of evaporator 7 increases by 0.1℃, and each time the "-" button is pressed, the outlet water temperature T2 of evaporator 7 decreases by 0.1℃. The unit automatically loads and unloads, with a default loading time of 0.5 seconds and a load adjustment interval of 1 minute. At this time, the load is controlled at about 3 load positions. After operating the unit, the load fluctuation is small. After adjustment, the circulating water flow needs to be adjusted according to the exhaust pressure value to control the exhaust pressure within the specified operating range to ensure the normal operation of the refrigeration unit.

[0078] The remote fully automatic mode includes adjusting the outlet water temperature T2 of the evaporator 7 according to the process temperature T5 of the process equipment 8, and controlling the compressor 1 to automatically load or unload at preset intervals according to the outlet water temperature T2 of the evaporator 7, so as to cooperate with the operation of the compressor 1, oil pump 4, circulating water supply device and chilled water supply device.

[0079] It should be noted that the remote fully automatic mode can be referred to as the third mode of this system. This third mode involves remote digital automatic operation. During the operation of the chiller unit, the chilled water outlet temperature is correlated with the process temperature control value. For example, when the process temperature T5 is controlled at 15-17℃, the chiller unit's evaporator 7 outlet water temperature T2 (chilled water outlet temperature) in this mode is 7.5-8℃ to meet the process parameters. In this mode, the chiller unit's evaporator 7 outlet water temperature T2 (chilled water outlet temperature) directly controls the process parameters. Based on fluctuations in the process temperature, the chiller unit automatically adjusts the outlet water temperature by 0.1℃ each time, with an adjustment interval of 60 seconds, to prevent large load fluctuations.

[0080] At this point, the discharge pressure will increase as the refrigeration unit load increases and decrease as the refrigeration unit load decreases. By adjusting the opening of the first regulating valve K1 and the second regulating valve K2, the circulating water flow rate L1 is adjusted, thereby controlling the discharge pressure P3 within the specified range. Furthermore, the suction pressure P4 will decrease as the system load increases and increase as the system load decreases; that is, the suction pressure P4 is directly proportional to the system load. Therefore, by adjusting the opening of the third regulating valve K3 and the fourth regulating valve K4, the chilled water flow rate L2 is adjusted, thereby controlling the suction pressure P4 within the specified range.

[0081] In this operating mode, the operator can set upper and lower limits for the outlet water temperature of evaporator 7, such as an upper limit of 20℃ and a lower limit of 5℃. When the actual chilled water outlet temperature of the chiller unit exceeds the set value, it can automatically stop and start to meet the process parameters. This application improves and optimizes the control mode of the control device, using a digital model to output three operating modes based on the result (the outlet water temperature T2 of evaporator 7, i.e., the chilled water temperature output to process equipment 8) to meet the process production requirements.

[0082] The following is a schematic diagram of the digital model relationship for specific automatic adjustment, see Table 1 for details.

[0083] Table 1

[0084]

[0085] Note: + and - represent the direct and inverse proportional relationships between the x and y axes. For example, if CV1 increases, T2 decreases accordingly to maintain the system's equilibrium.

[0086] It should be further explained that the outlet water temperature T2 of the evaporator 7 is adjusted according to the process temperature T5 of the process equipment 8. There is a correlation between the process temperature T5 and the outlet water temperature T2. For example, the relationship between the process temperature T5 of the process equipment 8 and the outlet water temperature T2 of the evaporator 7 can be referred to Table 2 below. Under normal operating conditions of the process temperature, the set outlet water temperature T2 can be adjusted according to the process temperature T5 to achieve automatic adjustment.

[0087] Table 2

[0088]

[0089] It should also be noted that the operation of the refrigeration unit mainly relies on the heat exchange of the condenser 5 and the evaporator 7. Based on the physicochemical properties of refrigerant R22, the following temperature and pressure comparison table is output, which can help diagnose the operating status and heat exchange effect of the refrigeration unit (that is, the current operating status of the refrigeration unit can be determined according to Table 3, and the three modes can be adjusted according to the operating status), see Table 3 below for details.

[0090] Table 3

[0091]

[0092] This application logically edits the relationships between the parameters of each component. To ensure stable process operation without significant adjustments, the chilled water outlet temperature is primarily controlled by the process temperature. When the process temperature changes, the outlet temperature T2 of evaporator 7 is adjusted synchronously to keep the process temperature within the specified range. When the outlet temperature T2 of evaporator 7 (i.e., the temperature of the chilled water supplied to process equipment 8) is adjusted, the equipment will logically make fine adjustments to prevent abnormal fluctuations caused by large adjustments. Furthermore, a specific adjustment time is set for each operation to achieve digital control of the chiller unit's operation. This system also has three control modes. Using the second mode reduces the frequency of manual operation of the unit, while the third mode enables the chiller unit and process operation to be connected in series, achieving fully automated control, improving equipment safety, eliminating the risk of downtime due to human error, and empowering the digital operation of the chiller unit.

[0093] It should be noted that the first regulating valve K1, the second regulating valve K2, the third regulating valve K3, the fourth regulating valve K4, the fifth regulating valve K5, the sixth regulating valve K6, and the seventh regulating valve K7, the first shut-off valve F1, the second shut-off valve F2, the third shut-off valve F3, the fourth shut-off valve F4, the fifth shut-off valve F5, the sixth shut-off valve F6, and the seventh shut-off valve F7, the first pipeline, the second pipeline, the third pipeline, the fourth pipeline, the fifth pipeline, the sixth pipeline, the seventh pipeline, the eighth pipeline, the ninth pipeline, the tenth pipeline, and the eleventh pipeline, the first temperature sensor, the second temperature sensor, the third temperature sensor, the fourth temperature sensor, and the fifth temperature sensor, the first flow sensor, and the second flow sensor, the first level gauge, and the second level gauge, the first pressure sensor, the second pressure sensor, the third pressure sensor, and the fourth pressure sensor mentioned in this invention are only distinguished by their different positions and do not have any order of precedence.

[0094] In addition, it should be noted that the orientation or positional relationship of the "entering" and other indications in this invention is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the purpose of simplifying the description and making it easier to understand, and does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0095] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Any combination of all embodiments provided by this invention is within the scope of protection of this invention and will not be elaborated upon here.

[0096] The cryogenic refrigeration unit control system provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A control system for a cryogenic refrigeration unit, characterized in that, include: A compressor (1) containing refrigeration oil is used to compress gaseous refrigerant; An oil separator (2) is connected to the air outlet of the compressor (1), and the liquid outlet of the oil separator (2) is connected to the oil inlet of the compressor (1). An oil cooler (3) is connected to the outlet of the oil separator (2); An oil pump (4) is located between the outlet of the oil cooler (3) and the inlet of the compressor (1); The condenser (5) is connected to the outlet of the oil separator (2) and the outlet of the oil cooler (3), respectively. The condenser (5) is also connected to the circulating water supply device. Economizer (6), which is connected to the liquid outlet of the condenser (5); Evaporator (7) is connected to the liquid outlet of the economizer (6), the gas outlet of the evaporator (7) is connected to the gas inlet of the compressor (1), the water inlet of the evaporator (7) is connected to the chilled water supply device, and the water outlet of the evaporator (7) is connected to the process equipment (8). A detection device for detecting the process temperature of the process equipment (8) and the inlet and outlet water temperatures of the evaporator (7); The control device is connected to the compressor (1), the oil pump (4), the circulating water supply device and the chilled water supply device. The control device is used to adjust the outlet water temperature T2 of the evaporator (7) according to the process temperature T5 of the process equipment (8), and to drive the compressor (1), the oil pump (4), the circulating water supply device and the chilled water supply device to operate so that the actual outlet water temperature of the evaporator (7) reaches the outlet water temperature T2 of the evaporator (7). The outlet of the evaporator (7) is connected to the inlet of the compressor (1) via a third pipeline, and a fifth shut-off valve (F5) is provided on the third pipeline; the outlet of the evaporator (7) is connected to the inlet of the compressor (1) via a fourth pipeline, and a fifth regulating valve (K5) for adjusting the flow rate of the refrigeration oil is provided on the fourth pipeline, and the fifth regulating valve (K5) is connected to the control device; the oil separator (2) is provided with a second pressure sensor for detecting the pressure P2 of the oil separator (2) and a liquid level H2 for detecting the liquid level H2 of the oil separator (2). The second level gauge; a fifth pipeline is provided between the outlet of the oil separator (2) and the oil cooler (3), and a seventh shut-off valve (F7) is provided on the fifth pipeline; the outlet of the oil separator (2) and the oil inlet of the compressor (1) are connected through a sixth pipeline, and a sixth regulating valve (K6) for regulating the flow rate of the refrigeration oil is provided on the sixth pipeline; a first pressure sensor for detecting the oil pressure P1 of the oil pump (4) is provided on the oil pump (4); a fifteenth pipeline is provided between the oil pump (4) and the oil inlet of the compressor (1), and a first pressure sensor is provided on the fifteenth pipeline. The sixth shut-off valve (F6), the second pressure sensor, the second level gauge, the sixth regulating valve (K6), and the first pressure sensor are all connected to the control device; a seventh pipeline is provided between the outlet of the oil separator (2) and the inlet of the condenser (5), and a first shut-off valve (F1) is provided on the seventh pipeline; an eighth pipeline is provided between the outlet of the oil cooler (3) and the inlet of the condenser (5), and a ninth pipeline is provided between the outlet of the condenser (5) and the inlet of the oil cooler (3); the outlet of the economizer (6) and the... A twelfth pipeline is provided between the air inlet of the compressor (1), a thirteenth pipeline and a fourteenth pipeline are provided in parallel between the liquid outlet of the economizer (6) and the evaporator (7), a second shut-off valve (F2) is provided on the thirteenth pipeline; a seventh regulating valve (K7) for regulating the refrigerant flow is provided on the fourteenth pipeline, a third shut-off valve (F3) is provided between the economizer (6) and the seventh regulating valve (K7), a fourth shut-off valve (F4) is provided between the seventh regulating valve (K7) and the evaporator (7), and the seventh regulating valve (K7) is connected to the control device.

2. The cryogenic refrigeration unit control system according to claim 1, characterized in that, A first pipeline is provided between the outlet of the evaporator (7) and the process equipment (8). The first pipeline is provided with a second flow sensor for detecting the chilled water flow rate L2, a third regulating valve (K3) for regulating the chilled water flow rate, and a second temperature sensor for detecting the outlet water temperature T2 of the evaporator (7). A second pipeline is provided between the chilled water supply device and the inlet of the evaporator (7). The second pipeline is provided with a fourth regulating valve (K4) for regulating the chilled water flow and a first temperature sensor for detecting the inlet water temperature T1 of the evaporator (7). The evaporator (7) is provided with a fourth pressure sensor for detecting the suction pressure P4 of the evaporator (7) and a first level gauge for detecting the liquid level H1 of the evaporator (7); the second flow sensor L2, the third regulating valve (K3), the first temperature sensor, the second temperature sensor, the fourth regulating valve (K4), the fourth pressure sensor and the first level gauge are all connected to the control device.

3. The cryogenic refrigeration unit control system according to claim 1 or 2, characterized in that, A tenth pipeline is provided between the outlet of the condenser (5) and the circulating water supply device. The tenth pipeline is provided with a first flow sensor for detecting the circulating water flow rate L1 of the circulating water supply device, a first regulating valve (K1) for adjusting the circulating water flow rate L1, and a fifth temperature sensor for detecting the outlet water temperature T5 of the condenser (5). An eleventh pipeline is provided between the water inlet of the condenser (5) and the circulating water supply device. The eleventh pipeline is provided with a second regulating valve (K2) for regulating the circulating water flow rate L1 and a fourth temperature sensor for detecting the water inlet temperature T4 of the condenser (5). The condenser (5) is provided with a third pressure sensor for detecting the exhaust pressure P3 of the condenser (5). The first flow sensor, the first regulating valve (K1), the fifth temperature sensor, the second regulating valve (K2), the fourth temperature sensor and the third pressure sensor are all connected to the control device.

4. The cryogenic refrigeration unit control system according to claim 1 or 2, characterized in that, The compressor (1) includes a screw compressor (1).

5. The cryogenic refrigeration unit control system according to claim 1 or 2, characterized in that, The control mode of the control device includes manual debugging mode, semi-automatic mode and remote fully automatic mode. The manual debugging mode includes adjusting the outlet water temperature T2 of the evaporator (7) according to the process temperature T5 of the process equipment (8), manually operating the compressor (1) to load and unload, and manually inputting the load value of the compressor (1) to drive the compressor (1), the oil pump (4), the circulating water supply device and the chilled water supply device to operate, so that the actual outlet water temperature of the evaporator (7) reaches the outlet water temperature T2 of the evaporator (7). The semi-automatic mode includes adjusting the outlet water temperature T2 of the evaporator (7) according to the process temperature T5 of the process equipment (8), manually operating the temperature adjustment button to increase or decrease the outlet water temperature T2 of the evaporator (7), and the compressor (1) automatically loading or unloading at preset times to cooperate with the operation of the compressor (1), the oil pump (4), the circulating water supply device and the chilled water supply device, so that the actual outlet water temperature of the evaporator (7) reaches the outlet water temperature T2 of the evaporator (7); The remote fully automatic mode includes adjusting the outlet water temperature T2 of the evaporator (7) according to the process temperature T5 of the process equipment (8), and controlling the compressor (1) to automatically load or unload at preset intervals according to the outlet water temperature T2 of the evaporator (7) to cooperate in driving the operation of the compressor (1), the oil pump (4), the circulating water supply device and the chilled water supply device.

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