An energy-saving compressed air supply system

Abstract

This utility model discloses an energy-saving compressed air supply system, including a centrifugal compressor unit with a first flow rate adjustment range; a variable frequency screw compressor unit with a second flow rate adjustment range; a compression heat regeneration adsorption drying system, the inlet of which is connected to the outlet of the centrifugal compressor unit; a freeze drying system, the inlet of which is connected to the outlet of the variable frequency screw compressor unit; a main air supply pipe, the outlets of the compression heat regeneration adsorption drying system and the freeze drying system are both connected to the main air supply pipe; and a monitoring and control system, including a pressure sensor, a flow meter, and a controller. Its advantages include the ability to achieve wide-range continuous air supply adjustment, full utilization of compression waste heat, significant reduction in system energy consumption, and provision of high-quality compressed air with stable pressure.

Description

Technical Field

[0001] This utility model relates to an air supply system, and more particularly to an energy-saving compressed air supply system. Background Technology

[0002] Compressed air, as a crucial power source in industrial production, is widely used in machinery manufacturing, electronics and semiconductors, food and pharmaceuticals, chemicals and textiles, and other fields. Compressed air supply stations provide a stable and reliable power supply to downstream air-consuming equipment by centrally producing and delivering high-quality compressed air. With the expansion of industrial production scale and the increase in automation, enterprises have increasingly higher requirements for compressed air quality and are placing more stringent demands on the energy efficiency indicators of the air supply system. Constructing efficient, energy-saving, and stable compressed air supply stations is of great significance for reducing production costs and improving product quality.

[0003] Existing industrial compressed air supply stations mainly employ two technical approaches: one is a supply system using multiple screw compressors operating in parallel, with pressure sensors controlling the loading, unloading, and start / stop of each unit to regulate the air supply; the other is a large-scale centralized supply system using centrifugal compressors, leveraging the high flow rate of a single centrifugal compressor to meet the entire plant's air supply needs with one or two large centrifugal compressors. For post-treatment, adsorption dryers (including heatless regeneration, micro-heat regeneration, or compression heat regeneration types) or refrigerated dryers are typically used to dry and purify the compressed air. The cooling system uses an open cooling tower in conjunction with a circulating water pump to provide cooling water for the air compressors and drying equipment.

[0004] However, both of the above technical approaches have significant drawbacks. While screw compressor gas supply stations offer a wide adjustment range per unit, frequent loading and unloading of multiple units during periods of significant gas load fluctuation can result in no-load power consumption reaching 30%-50% of full-load power consumption, leading to severe energy waste. Furthermore, multiple small screw compressors operating in parallel require a large floor space, have complex piping, and incur high investment and maintenance costs. Centrifugal compressor gas supply stations, while offering high flow rates per unit and a small footprint, have a narrow effective adjustment range (typically only 70%-100%). When gas consumption falls below their lower adjustment limit, they can only vent or shut down, failing to achieve continuous and stable gas supply. Additionally, centrifugal compressors have stringent requirements for intake conditions, are prone to surge, and exhibit poor operational stability. Utility Model Content

[0005] The purpose of this invention is to provide an energy-saving compressed air supply system that can achieve wide-range continuous air supply adjustment, make full use of compression waste heat, significantly reduce system energy consumption, and provide high-quality compressed air with stable pressure.

[0006] To achieve the above objectives, this utility model provides the following technical solution: an energy-saving compressed air supply system, comprising:

[0007] The centrifugal compressor unit has a first flow rate adjustment range, which has a minimum stable operating flow rate Q1 and a rated flow rate Q2.

[0008] The variable frequency screw compressor unit has a second flow rate adjustment range, the lower limit of which is less than the minimum stable operating flow rate Q1;

[0009] The inlet of the compression heat regeneration adsorption drying system is connected to the outlet of the centrifugal compressor unit;

[0010] The freeze-drying system has its inlet connected to the outlet of the variable frequency screw compressor unit;

[0011] The gas supply main pipe is connected to the outlet of the compression heat regeneration adsorption drying system and the outlet of the freeze drying system.

[0012] The monitoring and control system includes:

[0013] A pressure sensor is installed on the main air supply pipe to detect the compressed air pressure in the main air supply pipe;

[0014] A flow meter, installed on the main air supply pipe, is used to detect the flow rate of compressed air delivered to downstream users;

[0015] The controller is electrically connected to the pressure sensor, the flow meter, the centrifugal compressor unit, and the variable frequency screw compressor unit, and controls the operation of the centrifugal compressor unit and the variable frequency screw compressor unit based on the detected pressure and flow signals.

[0016] Preferably, the controller is configured to execute the following control modes:

[0017] When the compressed air flow rate Q detected by the flow meter satisfies Q1≤Q≤Q2, the controller controls the centrifugal compressor unit to run and the variable frequency screw compressor unit to stop.

[0018] When Q < Q1, the controller stops the centrifugal compressor unit and runs the variable frequency screw compressor unit. When the pressure value detected by the pressure sensor is lower than the set pressure value, the controller increases the operating frequency of the variable frequency screw compressor unit; when the detected pressure value is higher than the set pressure value, the controller decreases the operating frequency of the variable frequency screw compressor unit.

[0019] When Q > Q2, the controller controls the centrifugal compressor unit to operate at the rated flow rate and simultaneously starts the variable frequency screw compressor unit. When the pressure value detected by the pressure sensor is lower than the set pressure value, the controller increases the operating frequency of the variable frequency screw compressor unit; when the detected pressure value is higher than the set pressure value, the controller decreases the operating frequency of the variable frequency screw compressor unit.

[0020] Preferably, the centrifugal compressor unit includes a multi-stage centrifugal compressor and a self-cleaning air intake filter. The inlet of the self-cleaning air intake filter is connected to the atmosphere, and the outlet is connected to the inlet of the multi-stage centrifugal compressor. The self-cleaning air intake filter also has a backflush port, which is connected to the main air supply pipe through a backflush valve.

[0021] Preferably, the compression heat regeneration adsorption drying system includes a compression heat regeneration adsorption dryer, a precision dust filter, and a first short-circuit valve. The inlet of the compression heat regeneration adsorption dryer is connected to the outlet of the centrifugal compressor unit, and the outlet of the compression heat regeneration adsorption dryer is connected to both the first short-circuit valve and the inlet of the precision dust filter. The outlets of both the first short-circuit valve and the precision dust filter are connected to the main gas supply pipe.

[0022] Preferably, the variable frequency screw compressor unit is a permanent magnet variable frequency two-stage screw compressor unit.

[0023] Preferably, the freeze-drying system includes a wet tank and two sets of freeze-drying units connected in parallel. Each set of freeze-drying units includes a pre-filter, a variable frequency freeze dryer, a post-filter, and corresponding bypass valves. The inlet of the wet tank is connected to the outlet of the variable frequency screw compressor unit. The outlet of the wet tank is connected to the inlet of each of the two sets of pre-filters. The outlet of each pre-filter is connected to the inlet of the corresponding variable frequency freeze dryer. The outlet of each variable frequency freeze dryer is connected to the inlet of the corresponding post-filter. Each inlet and outlet of each pre-filter and post-filter is equipped with a control valve. Each pre-filter and post-filter is equipped with a bypass valve for bypassing compressed air during maintenance. The outlet of each post-filter is connected to the main air supply pipe.

[0024] Preferably, the system further includes a cooling water system, which includes a cooling tower and a variable frequency water pump. The outlet of the variable frequency water pump is connected to the cooling water inlet of the centrifugal compressor unit, the variable frequency screw compressor unit, and the variable frequency freeze dryer. The inlet of the variable frequency water pump is connected to the outlet of the cooling tower. The cooling water return outlet of the centrifugal compressor unit, the variable frequency screw compressor unit, and the variable frequency freeze dryer is connected to the inlet of the cooling tower.

[0025] Compared with existing technologies, the advantages of this utility model are as follows: This gas supply system achieves high-efficiency and energy-saving operation across the entire flow range by combining the different characteristics of centrifugal compressor units and variable frequency screw compressor units. This system fully utilizes the high efficiency advantage of centrifugal compressors under medium-to-high load conditions, and the flexible adjustment capability of variable frequency screw compressors under low-load and variable-load conditions. When the gas demand is within the stable operating range of the centrifugal compressor (Q1 to Q2), the system prioritizes the use of the centrifugal compressor unit with higher energy efficiency, while the variable frequency screw compressor unit is in a stopped state, avoiding unnecessary energy consumption. When the gas demand is lower than the minimum stable operating flow rate Q1 of the centrifugal compressor, the system intelligently switches to the variable frequency screw compressor unit, precisely matching the actual gas demand through variable frequency speed control, avoiding the surge risk and sharp efficiency drop of the centrifugal compressor under low load. When the gas demand exceeds the rated flow rate Q2 of the centrifugal compressor, the system adopts a combined operation mode of the two compressor units. The centrifugal compressor operates at its most efficient rated operating condition, while the variable frequency screw compressor unit supplements it, precisely making up the supply-demand difference through variable frequency adjustment. In addition, the system is equipped with corresponding drying systems for the different characteristics of the two compressor units: the centrifugal compressor unit is equipped with a compression heat regeneration adsorption drying system to make full use of compression heat to achieve zero gas consumption regeneration; the variable frequency screw compressor unit is equipped with a freeze drying system to adapt to its variable flow operation characteristics.

[0026] The entire system collects pressure and flow signals from the main gas supply pipe in real time through a monitoring and control system, enabling intelligent switching and load distribution of the compressor units. This ensures that the system operates at the optimal energy efficiency ratio under various operating conditions. Compared with traditional single-type compressor systems, it can achieve better energy-saving effects while significantly improving the reliability and stability of the gas supply system. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 This is a three-dimensional structural diagram of the present invention;

[0029] Figure 2 This is a functional block diagram of the monitoring and control system in this utility model;

[0030] In the diagram, 1. Centrifugal compressor unit; 2. Variable frequency screw compressor unit; 3. Compression heat regeneration adsorption drying system; 4. Freeze drying system; 5. Main air supply pipe; 6. Pressure sensor; 7. Flow meter; 8. Controller; 9. Multistage centrifugal compressor; 10. Self-cleaning air inlet filter; 11. Backflush valve; 12. Compression heat regeneration adsorption dryer; 13. Precision dust filter; 14. First short-circuit valve; 15. Wet tank; 16. Pre-filter; 17. Variable frequency freeze dryer; 18. Post-filter; 19. Bypass valve; 20. Control valve; 21. Cooling water system; 22. Cooling tower; 23. Variable frequency water pump. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] Example 1: As Figures 1-2 As shown, an energy-saving compressed air supply system includes:

[0033] Centrifugal compressor unit 1 has a first flow rate adjustment range, which has a minimum stable operating flow rate Q1 and a rated flow rate Q2;

[0034] The variable frequency screw compressor unit 2 has a second flow rate adjustment range, the lower limit of which is less than the minimum stable operating flow rate Q1;

[0035] The inlet of the compression heat regeneration adsorption drying system 3 is connected to the outlet of the centrifugal compressor unit 1;

[0036] The freeze-drying system 4 has its inlet connected to the outlet of the variable frequency screw compressor unit 2;

[0037] The outlets of the compressed heat regeneration adsorption drying system 3 and the freeze drying system 4 are all connected to the main gas supply pipe 5.

[0038] The monitoring and control system includes:

[0039] Pressure sensor 6 is installed on the main air supply pipe 5 and is used to detect the compressed air pressure in the main air supply pipe 5;

[0040] Flow meter 7 is installed on the main air supply pipe 5 and is used to detect the flow rate of compressed air delivered to downstream users;

[0041] The controller 8 is electrically connected to the pressure sensor 6, the flow meter 7, the centrifugal compressor unit 1, and the variable frequency screw compressor unit 2, and controls the operation of the centrifugal compressor unit 1 and the variable frequency screw compressor unit 2 based on the detected pressure and flow signals.

[0042] Example 2: Figures 1-2 As shown, unlike Embodiment 1, controller 8 is configured to execute the following control modes:

[0043] When the compressed air flow rate Q detected by the flow meter 7 satisfies Q1≤Q≤Q2, the controller 8 controls the centrifugal compressor unit 1 to run and the variable frequency screw compressor unit 2 to stop.

[0044] When Q < Q1, controller 8 controls the centrifugal compressor unit 1 to stop and the variable frequency screw compressor unit 2 to run. When the pressure value detected by pressure sensor 6 is lower than the set pressure value, controller 8 increases the operating frequency of variable frequency screw compressor unit 2; when the detected pressure value is higher than the set pressure value, controller 8 decreases the operating frequency of variable frequency screw compressor unit 2.

[0045] When Q > Q2, the controller 8 controls the centrifugal compressor unit 1 to operate at the rated flow rate, and simultaneously starts the variable frequency screw compressor unit 2. When the pressure value detected by the pressure sensor 6 is lower than the set pressure value, the controller 8 increases the operating frequency of the variable frequency screw compressor unit 2; when the detected pressure value is higher than the set pressure value, the controller 8 decreases the operating frequency of the variable frequency screw compressor unit 2.

[0046] This system achieves optimal energy efficiency across the entire operating range through intelligent flow zone management. The system divides the operating conditions into three zones based on the actual gas flow rate Q, with each zone employing the most suitable compressor combination mode. In the medium flow range (Q1≤Q≤Q2), the system prioritizes the operation of centrifugal compressor unit 1 alone. This is because centrifugal compressors have extremely high isentropic efficiency within their stable operating range, typically exceeding 85%. Meanwhile, variable frequency screw compressor unit 2 remains off, avoiding unnecessary standby power consumption. In the low flow range (Q<Q1), the system automatically switches to the operation mode of variable frequency screw compressor unit 2. This addresses the inherent defect of centrifugal compressors: when the flow rate falls below the minimum stable operating flow rate Q1, centrifugal compressors experience surge, leading to a sharp drop in efficiency and potential equipment damage. At this time, the variable frequency screw compressor uses variable frequency speed control technology and performs PID closed-loop control based on real-time feedback from the gas supply main 5 pressure. When the pressure is below the set value, the operating frequency is increased to increase the gas supply; conversely, the frequency is decreased to reduce the gas supply, achieving precise matching of supply and demand. In the high flow range (Q>Q2), the system adopts the base load and peak shaving operation modes. The centrifugal compressor, as the base load unit, operates at full load under the most efficient rated conditions, while the variable frequency screw compressor unit 2, as the peak shaving unit, supplements the gas supply gap. The total gas supply is precisely controlled through variable frequency regulation to ensure stable gas supply pressure.

[0047] In this embodiment, the centrifugal compressor unit 1 includes a multi-stage centrifugal compressor 9 and a self-cleaning air intake filter 10. The inlet of the self-cleaning air intake filter 10 is connected to the atmosphere, and the outlet is connected to the inlet of the multi-stage centrifugal compressor 9. The self-cleaning air intake filter 10 also has a backflush port, which is connected to the main air supply pipe 5 through a backflush valve 11.

[0048] This self-cleaning air intake filter system 10 employs innovative compressed air backflushing self-cleaning technology, enabling online automatic maintenance of the filter and fundamentally solving the problem of frequent shutdowns for filter element replacement required by traditional air intake filters. The system utilizes high-pressure compressed air from the main air supply pipe 5 as the backflushing air source. Through the timed opening of the backflushing valve 11, compressed air from the main air supply pipe 5 is introduced into the filter's backflushing port, performing a pulse-like reverse purging from the inside to the outside of the filter element. This inside-out backflushing airflow effectively removes dust particles adhering to the outer surface of the filter element, causing them to fall off and be discharged through the dust outlet, thereby restoring the filter element's filtration performance. The entire backflushing process can be performed while the centrifugal compressor is running normally, without requiring shutdown, truly achieving uninterrupted maintenance.

[0049] In this embodiment, the compression heat regeneration adsorption drying system 3 includes a compression heat regeneration adsorption dryer 12, a precision dust filter 13, and a first short-circuit valve 14. The inlet of the compression heat regeneration adsorption dryer 12 is connected to the outlet of the centrifugal compressor unit 1, and the outlet of the compression heat regeneration adsorption dryer 12 is connected to the inlet of the first short-circuit valve 14 and the precision dust filter 13, respectively. The outlets of the first short-circuit valve 14 and the precision dust filter 13 are both connected to the main air supply pipe 5.

[0050] This system makes full use of the high-temperature compressed air at the outlet of the centrifugal compressor to directly regenerate the adsorbent. Because the compression heat generated by the centrifugal compressor during the compression process can make the outlet gas temperature reach more than 120°C, it fully meets the regeneration temperature requirements of silica gel or molecular sieve adsorbents. This eliminates the need for auxiliary equipment such as electric heaters and regeneration fans in traditional drying systems, realizes the full recovery and utilization of waste heat, and significantly reduces the regeneration gas consumption and power consumption.

[0051] The first short-circuit valve 14 enables online maintenance of the precision dust filter 13. When the precision dust filter 13 needs filter element replacement or cleaning, the valve entering the filter can be closed and the short-circuit valve opened, allowing compressed air to directly enter the main air supply pipe 5 from the dryer outlet. This ensures that the system can still supply air normally during maintenance, avoiding production interruptions caused by maintenance shutdowns and improving system availability and maintenance flexibility. The system adopts a two-stage precision processing technology. The compression thermal regeneration adsorption dryer 12 is mainly responsible for water removal and coarse filtration, while the precision dust filter 13 performs precision dust removal and removes desiccant dust. The filtration accuracy can reach below 1μm, ensuring that the air supply quality meets the high standard requirements of a pressure dew point not exceeding -40℃ and extremely low dust content.

[0052] Example 3: Figures 1-2 As shown, unlike Embodiment 2, the variable frequency screw compressor unit 2 is a permanent magnet variable frequency two-stage screw compressor unit. The permanent magnet variable frequency two-stage screw compressor unit has advantages such as high starting torque, wide speed range, fast dynamic response, and stable operation. It can quickly respond to load changes and provide flexible and reliable flow regulation capabilities for the entire gas supply system.

[0053] In this embodiment, the freeze-drying system 4 includes a wet tank 15 and two sets of freeze-drying units connected in parallel. Each freeze-drying unit includes a pre-filter 16, a variable frequency freeze dryer 17, a post-filter 18, and a corresponding bypass valve 19. The inlet of the wet tank 15 is connected to the outlet of the variable frequency screw compressor unit 2. The outlet of the wet tank 15 is connected to the inlet of the two sets of pre-filters 16. The outlet of each pre-filter 16 is connected to the inlet of the corresponding variable frequency freeze dryer 17. The outlet of each variable frequency freeze dryer 17 is connected to the inlet of the corresponding post-filter 18. Each inlet and outlet of each pre-filter 16 and post-filter 18 is equipped with a control valve 20. Each pre-filter 16 and post-filter 18 is equipped with a bypass valve 19 for bypassing compressed air during maintenance. The outlet of each post-filter 18 is connected to the main air supply pipe 5.

[0054] The wet tank 15 serves as a buffer and pretreatment unit in the system, undertaking crucial process functions. The high-temperature, high-humidity compressed air discharged from the screw compressor first enters the wet tank 15 for temporary storage and preliminary cooling. By increasing the gas residence time and heat exchange area, the temperature naturally decreases and water vapor undergoes initial condensation and separation, creating favorable process conditions for subsequent freeze-drying. The wet tank 15 also buffers flow pulsations and stabilizes the flow rate, effectively mitigating the impact of intermittent discharge from the screw compressor on downstream equipment and improving the overall system's operational stability.

[0055] The configuration of two parallel freeze-drying units reflects the system's redundancy design. Under normal operating conditions, the two units can be selected to operate individually or in parallel according to actual load requirements, achieving flexible adjustment of processing capacity. When the screw compressor is operating at low load, a single freeze-drying unit can meet the processing needs, while the other unit can be in standby mode, avoiding inefficient operation of the equipment; when the load is high, both units operate simultaneously to ensure sufficient processing capacity. This parallel design also provides system redundancy protection; when one unit requires maintenance or fails, the other unit can continue to operate normally, ensuring the continuity and reliability of gas supply.

[0056] The variable frequency freeze dryer 17 adopts DC inverter technology, which can automatically adjust the operating frequency and power output of the refrigeration compressor according to the intake air flow and humidity load. Traditional fixed frequency freeze dryers have the problem of excess refrigeration capacity under partial load conditions, resulting in frequent start-stop cycles and energy waste. Variable frequency technology achieves precise matching between refrigeration capacity and actual heat load by precisely controlling the speed of the refrigeration compressor, avoiding the phenomenon of over-engineering and under-balancing, and significantly improving the operating efficiency of the equipment under varying conditions. At the same time, variable frequency regulation can also maintain the stability of evaporation temperature, ensure the consistency of pressure dew point, and improve the stability of drying quality.

[0057] The pre-filter 16 and post-filter 18 constitute a complete three-stage filtration process. The pre-filter 16 primarily performs oil removal and coarse filtration, removing lubricating oil mist and larger particulate impurities from the screw compressor, while further removing water and cooling the air to create clean intake conditions for the refrigerated dryer. The variable frequency refrigerated dryer 17 is responsible for precision water removal, condensing and separating water vapor through refrigeration to achieve deep drying. The post-filter 18 performs final precision filtration, mainly removing tiny water droplets and residual impurities that may be generated during the refrigeration process, ensuring that the final air supply meets high-quality standards. Through this staged treatment, the system can process the compressed air from the screw compressor outlet to a high-quality level with a pressure dew point of 2-8℃, dust content less than 0.1 microns, and oil content less than 0.1 ppm.

[0058] Each pre-filter 16 and post-filter 18 is equipped with an independent bypass valve 19. When a filter needs to have its filter element replaced or be maintained, the inlet and outlet control valves 20 of that filter can be closed, while the corresponding bypass valve 19 is opened, allowing compressed air to bypass the equipment to be maintained and continue to flow, thus achieving maintenance without interrupting production. This design not only improves the availability of the system, but also provides greater flexibility for operation and management. Maintenance time can be reasonably arranged according to the production plan, reducing maintenance costs and production losses.

[0059] In this embodiment, a cooling water system 21 is also included. The cooling water system 21 includes a cooling tower 22 and a variable frequency water pump 23. The outlet of the variable frequency water pump 23 is connected to the cooling water inlet of the centrifugal compressor unit 1, the variable frequency screw compressor unit 2 and the variable frequency freeze dryer 17. The inlet of the variable frequency water pump 23 is connected to the outlet of the cooling tower 22. The cooling water return outlet of the centrifugal compressor unit 1, the variable frequency screw compressor unit 2 and the variable frequency freeze dryer 17 is connected to the inlet of the cooling tower 22.

[0060] The cooling water system 21 adopts a centralized closed-loop cooling design, providing unified cooling services for the core equipment of the entire compressed air supply station. The system uses a variable frequency water pump 23 to deliver low-temperature cooling water, cooled by the cooling tower 22, to each piece of equipment. After exchanging heat with the high-temperature medium inside the equipment, the cooling water carries the heat back to the cooling tower 22 for further cooling, forming a complete thermodynamic cycle. This centralized cooling method has significant advantages over decentralized cooling, enabling unified allocation and optimized utilization of cooling resources, improving overall cooling efficiency, and reducing equipment investment and operating costs.

[0061] The variable frequency water pump 23 can automatically adjust its speed and flow rate according to actual cooling needs. When the equipment load is low, the pump speed is reduced to decrease the circulating water volume, and when the load increases, the speed is increased to increase the flow rate. This achieves dynamic matching between cooling capacity and actual heat load. The energy-saving effect is even more obvious, especially when the equipment is operating under partial load for a long time.

[0062] Cooling tower 22 is responsible for the final heat dissipation function of the system. Cooling tower 22 is usually equipped with a variable frequency fan, which can automatically adjust the fan speed according to the cooling water return temperature, so as to minimize the fan power consumption while ensuring the cooling effect. When the return water temperature is low, the fan runs at low speed or intermittently to reduce power consumption; when the return water temperature rises, the fan automatically increases the speed to enhance the heat dissipation capacity and ensure that the supply water temperature meets the equipment cooling requirements.

[0063] The above are merely embodiments of this application and do not limit the scope of this patent application. Any equivalent structural or procedural changes made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this application.

Claims

1. An energy-saving compressed air supply system, characterized in that, include: The centrifugal compressor unit has a first flow rate adjustment range, which has a minimum stable operating flow rate Q1 and a rated flow rate Q2. The variable frequency screw compressor unit has a second flow rate adjustment range, the lower limit of which is less than the minimum stable operating flow rate Q1; The inlet of the compression heat regeneration adsorption drying system is connected to the outlet of the centrifugal compressor unit; The freeze-drying system has its inlet connected to the outlet of the variable frequency screw compressor unit; The gas supply main pipe is connected to the outlet of the compression heat regeneration adsorption drying system and the outlet of the freeze drying system. The monitoring and control system includes: A pressure sensor is installed on the main air supply pipe to detect the compressed air pressure in the main air supply pipe; A flow meter, installed on the main air supply pipe, is used to detect the flow rate of compressed air delivered to downstream users; The controller is electrically connected to the pressure sensor, the flow meter, the centrifugal compressor unit, and the variable frequency screw compressor unit, and controls the operation of the centrifugal compressor unit and the variable frequency screw compressor unit based on the detected pressure and flow signals.

2. The energy-saving compressed air supply system according to claim 1, characterized in that: The controller is configured to execute the following control modes: When the compressed air flow rate Q detected by the flow meter satisfies Q1≤Q≤Q2, the controller controls the centrifugal compressor unit to run and the variable frequency screw compressor unit to stop. When Q < Q1, the controller stops the centrifugal compressor unit and runs the variable frequency screw compressor unit. When the pressure value detected by the pressure sensor is lower than the set pressure value, the controller increases the operating frequency of the variable frequency screw compressor unit; when the detected pressure value is higher than the set pressure value, the controller decreases the operating frequency of the variable frequency screw compressor unit. When Q > Q2, the controller controls the centrifugal compressor unit to operate at the rated flow rate and simultaneously starts the variable frequency screw compressor unit. When the pressure value detected by the pressure sensor is lower than the set pressure value, the controller increases the operating frequency of the variable frequency screw compressor unit; when the detected pressure value is higher than the set pressure value, the controller decreases the operating frequency of the variable frequency screw compressor unit.

3. The energy-saving compressed air supply system according to claim 1, characterized in that: The centrifugal compressor unit includes a multi-stage centrifugal compressor and a self-cleaning air intake filter. The inlet of the self-cleaning air intake filter is connected to the atmosphere, and the outlet is connected to the inlet of the multi-stage centrifugal compressor. The self-cleaning air intake filter also has a backflush port, which is connected to the main air supply pipe through a backflush valve.

4. The energy-saving compressed air supply system according to claim 1, characterized in that: The compression heat regeneration adsorption drying system includes a compression heat regeneration adsorption dryer, a precision dust filter, and a first short-circuit valve. The inlet of the compression heat regeneration adsorption dryer is connected to the outlet of the centrifugal compressor unit. The outlet of the compression heat regeneration adsorption dryer is connected to both the first short-circuit valve and the inlet of the precision dust filter. The outlets of both the first short-circuit valve and the precision dust filter are connected to the main gas supply pipe.

5. The energy-saving compressed air supply system according to claim 1, characterized in that: The variable frequency screw compressor unit is a permanent magnet variable frequency two-stage screw compressor unit.

6. The energy-saving compressed air supply system according to claim 5, characterized in that: The freeze-drying system includes a wet tank and two sets of freeze-drying units connected in parallel. Each set of freeze-drying units includes a pre-filter, a variable frequency freeze dryer, a post-filter, and corresponding bypass valves. The inlet of the wet tank is connected to the outlet of the variable frequency screw compressor unit. The outlet of the wet tank is connected to the inlet of each of the two sets of pre-filters. The outlet of each pre-filter is connected to the inlet of the corresponding variable frequency freeze dryer. The outlet of each variable frequency freeze dryer is connected to the inlet of the corresponding post-filter. Each pre-filter and post-filter has a control valve at both its inlet and outlet. Each pre-filter and post-filter has a bypass valve for bypassing compressed air during maintenance. The outlet of each post-filter is connected to the main air supply pipe.

7. The energy-saving compressed air supply system according to claim 6, characterized in that: It also includes a cooling water system, which includes a cooling tower and a variable frequency water pump. The outlet of the variable frequency water pump is connected to the cooling water inlet of the centrifugal compressor unit, the variable frequency screw compressor unit, and the variable frequency freeze dryer. The inlet of the variable frequency water pump is connected to the outlet of the cooling tower. The cooling water return outlet of the centrifugal compressor unit, the variable frequency screw compressor unit, and the variable frequency freeze dryer is connected to the inlet of the cooling tower.

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