RO pure water inlet constant temperature energy-saving control system and method based on air compressor waste heat

Abstract

The application provides a RO pure water inlet constant temperature energy-saving control system and method based on air compressor waste heat, and belongs to the technical field of waste heat recovery and reverse osmosis water treatment. The system comprises a waste heat recovery unit, a RO inlet heat utilization unit and a PLC control unit. The waste heat recovery unit recovers waste heat generated during operation of a variable frequency air compressor, and delivers the heat to a hot water temperature adjusting plate heat exchanger for RO inlet water tank heat exchange; the RO inlet heat utilization unit is used for sending inlet water in the RO inlet water tank into the hot water temperature adjusting plate heat exchanger, using the waste heat generated by the variable frequency air compressor for RO inlet heat exchange, and then delivering the heated RO inlet water to a RO reverse osmosis membrane system through a RO booster pump; and the PLC control unit is used for controlling the temperature of water sent to the RO reverse osmosis membrane system according to the water temperature of a water outlet of the RO inlet water tank; energy saving is realized by replacing electric heating with air compressor waste heat, and meanwhile, the PLC control unit can be used for precise temperature control to avoid damage to the RO membrane assembly.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery and reverse osmosis water treatment technology, specifically to a constant temperature energy-saving control system and method for RO pure water feed water based on air compressor waste heat. Background Technology

[0002] Industrial air compressors, widely used in various industries, generate a large amount of compression heat and lubricating oil heat during operation. The temperature of this waste heat is maintained at 85-110℃ year-round. Most existing solutions only use it for heating domestic hot water or heating, failing to match the optimal water temperature for RO pure water utilization. This results in low waste heat utilization rate, with a large amount of heat being directly released and wasted during the non-heating season. At the same time, existing RO pure water systems lack intelligent control of the inlet water temperature. They cannot automatically adjust the RO inlet water temperature to the preset inlet water temperature range according to different inlet water temperatures, which can lead to damage to the RO membrane module. Summary of the Invention

[0003] In view of this, the present invention provides a constant temperature energy-saving control system and method for RO pure water feed water based on the waste heat of air compressor, so as to solve the problem of energy waste caused by the waste heat generated during the operation of air compressor and to avoid damage to RO membrane modules.

[0004] An energy-saving RO pure water inlet temperature control system based on air compressor waste heat includes: a waste heat recovery unit, an RO inlet heat utilization unit, and a PLC control unit; the waste heat recovery unit includes a variable frequency air compressor, a hot water temperature regulating plate heat exchanger, and a PID control valve; the RO inlet heat utilization unit includes an RO inlet water tank, a chilled water temperature regulating plate heat exchanger, an RO booster pump, and an RO reverse osmosis membrane system; the waste heat recovery unit is connected to the RO inlet heat utilization unit, and the PLC control unit is electrically connected to both the waste heat recovery unit and the RO inlet heat utilization unit; in the waste heat recovery unit, the heat outlet of the variable frequency air compressor is connected to the heat inlet of the hot water temperature regulating plate heat exchanger through the PID control valve, the cold outlet of the hot water temperature regulating plate heat exchanger is connected to the cold inlet of the variable frequency air compressor, and the PID control valve is connected to the PLC control unit. The control unit is electrically connected; in the RO feed water heat utilization unit, the outlet of the RO feed water tank is connected to the inlet of the hot water temperature regulating plate heat exchanger, and the outlet of the hot water temperature regulating plate heat exchanger is connected to the inlet of the RO reverse osmosis membrane system; the waste heat recovery unit recovers the waste heat generated by the operation of the variable frequency air compressor and transfers the heat to the hot water temperature regulating plate heat exchanger to exchange heat with the feed water of the RO feed water tank; the RO feed water heat utilization unit is used to send the feed water in the RO feed water tank into the hot water temperature regulating plate heat exchanger, and use the waste heat generated by the variable frequency air compressor to exchange heat with the feed water, and then send the heated RO feed water into the RO reverse osmosis membrane system through the RO booster pump; the PLC control unit is used to control the temperature of the feed water sent into the RO reverse osmosis membrane system according to the water temperature at the outlet of the RO feed water tank.

[0005] Preferably, a first electric valve is installed on the pipeline connecting the hot water temperature regulating plate heat exchanger and the RO reverse osmosis membrane system. The first electric valve is electrically connected to the PLC control unit to control the flow of water from the hot water temperature regulating plate heat exchanger to the RO reverse osmosis membrane system pipeline.

[0006] Preferably, the RO feed water heat utilization unit further includes a chilled water temperature regulating plate heat exchanger and a chilled water branch; the inlet of the chilled water branch is connected to the cold water inlet of the chilled water temperature regulating plate heat exchanger, and the cold water outlet of the chilled water temperature regulating plate heat exchanger is connected to the pipeline connected to the inlet of the RO reverse osmosis membrane system; the outlet of the RO feed water tank is connected to the hot water inlet of the chilled water temperature regulating plate heat exchanger, and a third electric valve is installed on the pipeline connecting the RO feed water tank and the chilled water temperature regulating plate heat exchanger, and the third electric valve is electrically connected to the PLC control unit; the PLC control unit controls the third electric valve to introduce external chilled water for cooling in a timely manner when the RO feed water temperature exceeds the preset temperature range.

[0007] Preferably, the outlet of the RO feed water tank is directly connected to the inlet of the RO reverse osmosis membrane system, and a second electric valve is installed on the pipeline connecting the RO feed water tank and the RO reverse osmosis membrane system. The second electric valve is electrically connected to the PLC control unit. When the RO feed water temperature is within the preset temperature range, no heat exchange or cooling treatment is required, and the RO feed water is directly delivered to the RO reverse osmosis membrane system.

[0008] Preferably, the waste heat recovery unit further includes an air compressor waste heat recovery plate heat exchanger; the heat inlet of the air compressor waste heat recovery plate heat exchanger is connected to the heat outlet of the variable frequency air compressor, the heat outlet of the air compressor waste heat recovery plate heat exchanger is connected to the heat inlet of the hot water temperature regulating plate heat exchanger through the PID regulating valve, the cold inlet of the air compressor waste heat recovery plate heat exchanger is connected to the cold outlet of the hot water temperature regulating plate heat exchanger, and the cold outlet of the air compressor waste heat recovery plate heat exchanger is connected to the cold inlet of the variable frequency air compressor; the waste heat generated by the operation of the variable frequency air compressor is transported to the RO inlet water heat utilization unit, and at the same time, the heat after heat exchange and cooling flows back to the variable frequency air compressor, realizing a closed-loop circulation of waste heat.

[0009] Preferably, the waste heat recovery unit further includes an air compressor waste heat circulation pump and a hot water circulation pump; the inlet of the air compressor waste heat circulation pump is connected to the cold outlet of the air compressor waste heat recovery plate heat exchanger, the outlet of the air compressor waste heat circulation pump is connected to the variable frequency air compressor, the inlet of the hot water circulation pump is connected to the cold outlet of the hot water temperature regulating plate heat exchanger, and the outlet of the hot water circulation pump is connected to the cold inlet of the air compressor waste heat recovery plate heat exchanger; through the air compressor waste heat circulation pump and the hot water circulation pump, a heat circulation is formed between the variable frequency air compressor and the hot water temperature regulating plate heat exchanger, ensuring that waste heat is continuously delivered and efficiently utilized.

[0010] Preferably, the waste heat recovery unit further includes a domestic water branch; a fourth electric valve is installed on the domestic water branch, the domestic water branch is connected to the heat outlet of the air compressor waste heat recovery plate heat exchanger, and the fourth electric valve is electrically connected to the PLC control unit; by adjusting the PID regulating valve and the fourth electric valve, when the RO inlet water heat utilization unit no longer needs waste heat, the excess heat is transferred to the domestic water branch to heat the domestic water.

[0011] Preferably, the PLC control unit includes a data acquisition unit, a judgment unit, and a control unit. The data acquisition unit is electrically connected to the RO inlet water tank, the data acquisition unit is connected to the judgment unit, the judgment unit is connected to the control unit, and the control unit is electrically connected to the first electric valve, the second electric valve, the third electric valve, the fourth electric valve, and the PID regulating valve, respectively. By acquiring the RO inlet water temperature, making a judgment, and finally constructing a complete control path based on the joint control of each valve, a complete control path is formed.

[0012] On the other hand, this application also provides a method for constant temperature and energy-saving control of RO pure water inlet based on waste heat from an air compressor. The method employs the aforementioned energy-saving control system for constant temperature and energy-saving RO pure water inlet based on waste heat from an air compressor, specifically including the following steps:

[0013] S1: The acquisition unit is used to acquire the RO inlet water temperature of the RO inlet water tank to obtain the RO inlet water temperature;

[0014] S2: The judgment unit is used to compare the RO inlet water temperature collected by the acquisition unit with the built-in judgment formula;

[0015] S3: The control unit is used to control the opening and closing of the first electric valve, the second electric valve, the third electric valve, the fourth electric valve, and the PID regulating valve according to the judgment result of the judgment unit.

[0016] Preferably, in step S3, the control unit is used to control the opening and closing of the first electric valve, the second electric valve, the third electric valve, the fourth electric valve, and the PID regulating valve according to the result of the judgment unit's judgment, specifically as follows:

[0017] When the judgment unit determines that the RO inlet water temperature is <20℃: the control unit controls the first electric valve to open and the second electric valve, the third electric valve, and the fourth electric valve to close, thereby raising the temperature of the RO inlet water;

[0018] When the judgment unit determines that the RO inlet water temperature is between 20 and 25°C: the control unit controls the PID regulating valve and the first, second, third, and fourth electric valves to maintain constant temperature operation. When the judgment unit determines that the RO inlet water temperature is between 25 and 28°C: the control unit controls the PID regulating valve to be adjusted to a lower setting, the first electric valve to be opened, and the second, third, and fourth electric valves to be closed, reducing the transfer of residual heat. When the judgment unit determines that the RO inlet water temperature is between 28 and 30°C (inlet water temperature greater than 28°C and less than or equal to 30°C): the control unit controls the second electric valve to be opened, and the first, third, and fourth electric valves to be closed, reducing the transfer of residual heat. When the judgment unit determines that the RO inlet water temperature is greater than 30°C: the control unit controls the PID regulating valve to be closed, and the first, second, and fourth electric valves to be shut off immediately, while the third electric valve is opened; allowing the RO inlet water to enter the chilled water temperature regulating plate heat exchanger for cooling, thereby reaching the preset temperature range.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention discloses a constant-temperature energy-saving control system and method for RO pure water feed water based on waste heat from an air compressor. The system includes a waste heat recovery unit, an RO feed water heat utilization unit, and a PLC control unit. The waste heat recovery unit, through the cooperation of the variable frequency air compressor, the hot water temperature regulating plate heat exchanger, and the PID regulating valve, recovers the waste heat generated by the operation of the variable frequency air compressor and delivers it to the hot water temperature regulating plate heat exchanger. The RO feed water heat utilization unit sends the RO feed water from the RO feed water tank into the hot water temperature regulating plate heat exchanger for heat exchange and temperature increase, and then delivers it to the RO reverse osmosis membrane system via the RO booster pump. The PLC control unit controls the temperature of the RO feed water sent to the RO reverse osmosis membrane system according to the water temperature at the outlet of the RO feed water tank, thereby achieving constant-temperature energy-saving control based on the waste heat of the variable frequency air compressor.

[0021] Specifically, the waste heat recovery unit transfers the compression heat and heat dissipation waste heat generated by the variable frequency air compressor to the hot water temperature regulating plate heat exchanger, which then exchanges heat with the RO feed water heat utilization unit for the RO feed water. This replaces the traditional electric heating and steam heating methods, significantly improving the utilization rate of the waste heat from the variable frequency air compressor and reducing the system's operating energy consumption. The PCL control unit monitors and collects the water temperature at the outlet of the RO feed water tank in real time, controls the appropriate RO feed water temperature, and then delivers it to the RO reverse osmosis membrane system.

[0022] By recovering and effectively utilizing the waste heat generated during the operation of the variable frequency air compressor, replacing the traditional heating method, heat exchange of RO feed water can be achieved without additional external conditions, fundamentally reducing the system's dependence on external conditions, thereby reducing operating energy consumption and achieving energy saving. The RO feed water heat utilization unit is divided into three branches, and the PLC control unit judges the water temperature at the outlet of the RO feed water tank in real time and precisely controls the corresponding valves to ensure that the RO feed water temperature is controlled within the optimal temperature range. This avoids the RO membrane flux reduction and insufficient water production caused by increased water viscosity at low temperatures, and also prevents damage to the RO membrane components caused by high temperatures. Attached Figure Description

[0023] Figure 1 This is a flowchart of a constant temperature energy-saving control system and method for RO pure water inlet based on waste heat from an air compressor.

[0024] Figure 2 The connection relationship is shown in the RO pure water inlet constant temperature energy-saving control system and method based on air compressor waste heat.

[0025] Figure 3 This describes the connection relationship of each module within the PLC control unit of the RO pure water inlet constant temperature energy-saving control system and method based on air compressor waste heat.

[0026] In the diagram: Waste heat recovery unit 1, variable frequency air compressor 11, hot water temperature regulating plate heat exchanger 12, PID regulating valve 13, air compressor waste heat recovery plate heat exchanger 14, waste heat circulation pump 15, hot water circulation pump 16, domestic water branch 17, fourth electric valve 18, RO inlet water heat utilization unit 2, RO inlet water tank 21, chilled water temperature regulating plate heat exchanger 22, RO reverse osmosis membrane system 23, first electric valve 24, chilled water branch 25, third electric valve 26, second electric valve 27, RO booster pump 28, PLC control unit 3, acquisition unit 31, judgment unit 32, control unit 33. Detailed Implementation

[0027] To facilitate understanding of this application, a more comprehensive description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are also given. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of this application.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] An energy-saving RO pure water inlet temperature control system based on air compressor waste heat includes: a waste heat recovery unit 1, an RO inlet heat utilization unit 2, and a PLC control unit 3; the waste heat recovery unit 1 includes: a variable frequency air compressor 11, a hot water temperature regulating plate heat exchanger 12, and a PID control valve 13; the RO inlet heat utilization unit 2 includes an RO inlet water tank 21, a chilled water temperature regulating plate heat exchanger 22, an RO booster pump 28, and an RO reverse osmosis membrane system 23; the waste heat recovery unit 1 is connected to the RO inlet heat utilization unit 2, and the PLC control unit 3 is electrically connected to both the waste heat recovery unit 1 and the RO inlet heat utilization unit 2; in the waste heat recovery unit 1, the heat outlet of the variable frequency air compressor 11 is connected to the heat inlet of the hot water temperature regulating plate heat exchanger 12 through the PID control valve 13, the cold outlet of the hot water temperature regulating plate heat exchanger 12 is connected to the cold inlet of the variable frequency air compressor 11, and the PID control valve 13 is connected to the PLC control unit 3. The LC control unit 3 is electrically connected; in the RO feed water heat utilization unit 2, the outlet of the RO feed water tank 21 is connected to the inlet of the hot water temperature regulating plate heat exchanger 12, and the outlet of the hot water temperature regulating plate heat exchanger 12 is connected to the inlet of the RO reverse osmosis membrane system 23; the waste heat recovery unit 1 recovers the waste heat generated by the operation of the variable frequency air compressor 11 and transfers the heat to the hot water temperature regulating plate heat exchanger 12 to supply the feed water to the RO feed water tank 21. Heat exchange; the RO feed water heat utilization unit 2 is used to send the feed water in the RO feed water tank 21 into the hot water temperature regulating plate heat exchanger 12, and use the waste heat generated by the variable frequency air compressor 11 to exchange heat with the feed water, and then send the heated RO feed water into the RO reverse osmosis membrane system 23 through the RO booster pump 28; the PLC control unit 3 is used to control the temperature of the RO feed water sent into the RO reverse osmosis membrane system 23 according to the water temperature at the outlet of the RO feed water tank 21.

[0030] Specifically, the waste heat recovery unit 1 transfers the compression heat and heat dissipation waste heat generated by the operation of the variable frequency air compressor 11 to the hot water temperature regulating plate heat exchanger 12, which then exchanges heat with the RO feed water heat utilization unit 2 for the RO feed water. This replaces the traditional electric heating and steam heating methods, significantly improving the utilization rate of the waste heat of the variable frequency air compressor 11 and reducing the system's operating energy consumption. The PLC control unit 3 monitors and collects the water temperature at the outlet of the RO feed water tank 21 in real time, and controls and adjusts the corresponding valves to control the RO feed water temperature within the preset temperature range in the PLC control unit 3. Then, the RO feed water within the preset temperature range is delivered to the RO reverse osmosis membrane system 23 through the RO booster pump 28.

[0031] The RO feed water is heated and cooled in the RO feed water heat utilization unit 2 or directly fed into the RO reverse osmosis membrane system 23. In conjunction with the PLC control unit 3, the feed water temperature is monitored in real time to stabilize the RO feed water temperature within the range of 20~25℃. The system can raise the temperature in winter and prevent overheating in summer. By controlling the opening of the PID regulating valve 13 and the opening status of each electric valve, the RO feed water temperature is kept constant to prevent problems such as RO membrane damage caused by excessively high or low water temperature.

[0032] Furthermore, a first electric valve 24 is installed on the pipeline connecting the hot water temperature regulating plate heat exchanger 12 and the RO reverse osmosis membrane system 23. The first electric valve 24 is electrically connected to the PLC control unit 3 to control the flow of water from the hot water temperature regulating plate heat exchanger 12 to the RO reverse osmosis membrane system 23. By installing the first electric valve 24 and electrically connecting it to the PLC control unit 3, the PLC control unit 3 can adjust the first electric valve 24 to ensure that the RO inlet water heating process is controllable.

[0033] Furthermore, the RO feed water heat utilization unit 2 also includes a chilled water temperature regulating plate heat exchanger 22 and a chilled water branch 25; the inlet of the chilled water branch 25 is connected to the cold water inlet of the chilled water temperature regulating plate heat exchanger 22, and the cold water outlet of the chilled water temperature regulating plate heat exchanger 22 is connected to the pipeline connected to the inlet of the RO reverse osmosis membrane system 23; the outlet of the RO feed water tank 21 is connected to the hot water inlet of the chilled water temperature regulating plate heat exchanger 22, and a third electric valve 26 is installed on the pipeline connecting the RO feed water tank 21 and the chilled water temperature regulating plate heat exchanger 22, and the third electric valve 26 is electrically connected to the PLC control unit 3; the PLC control unit 3 controls the third electric valve 36 to introduce external chilled water in time to cool down the RO feed water when the RO feed water temperature exceeds the preset temperature range; the chilled water branch 25 is introduced to cool down the high-temperature RO feed water to avoid damage to the RO membrane caused by high temperature.

[0034] Furthermore, the outlet of the RO inlet water tank 21 is directly connected to the inlet of the RO reverse osmosis membrane system 23. A second electric valve 27 is installed on the pipeline connecting the RO inlet water tank 21 and the RO reverse osmosis membrane system 23. The second electric valve 27 is electrically connected to the PLC control unit 3. When the RO inlet water temperature is within the preset temperature range, no heat exchange or cooling treatment is required, and the RO inlet water is directly delivered to the RO reverse osmosis membrane system 23.

[0035] Furthermore, the waste heat recovery unit 1 also includes an air compressor waste heat recovery plate heat exchanger 14; the heat inlet of the air compressor waste heat recovery plate heat exchanger 14 is connected to the heat outlet of the variable frequency air compressor 11, the heat outlet of the air compressor waste heat recovery plate heat exchanger 14 is connected to the heat inlet of the hot water temperature regulating plate heat exchanger 12 through the PID regulating valve 13, the cold inlet of the air compressor waste heat recovery plate heat exchanger 14 is connected to the cold outlet of the hot water temperature regulating plate heat exchanger 12, and the cold outlet of the air compressor waste heat recovery plate heat exchanger 14 is connected to the cold inlet of the variable frequency air compressor 11; the waste heat generated by the operation of the variable frequency air compressor 11 is transported to the RO inlet water heat utilization unit 2, and at the same time, the heat after heat exchange and cooling flows back to the variable frequency air compressor 11, realizing a closed-loop circulation of waste heat.

[0036] Furthermore, the waste heat recovery unit 1 also includes an air compressor waste heat circulation pump 15 and a hot water circulation pump 16; the inlet of the air compressor waste heat circulation pump 15 is connected to the cold outlet of the air compressor waste heat recovery plate heat exchanger 14, the outlet of the air compressor waste heat circulation pump 15 is connected to the variable frequency air compressor 11, the inlet of the hot water circulation pump 16 is connected to the cold outlet of the hot water temperature regulating plate heat exchanger 12, and the outlet of the hot water circulation pump 16 is connected to the cold inlet of the air compressor waste heat recovery plate heat exchanger 14; through the air compressor waste heat circulation pump 15 and the hot water circulation pump 16, a heat circulation is formed between the variable frequency air compressor 11 and the hot water temperature regulating plate heat exchanger 12, ensuring that waste heat is continuously transported and efficiently utilized.

[0037] Furthermore, the waste heat recovery unit 1 also includes a domestic water branch line 17; a fourth electric valve 18 is installed on the domestic water branch line 17, and the domestic water branch line 17 is connected to the heat outlet of the air compressor waste heat recovery plate heat exchanger 14. The fourth electric valve 18 is electrically connected to the PLC control unit 3. By adjusting the PID regulating valve 13 and the fourth electric valve 18, when the RO inlet water heat utilization unit 2 no longer needs waste heat, the excess heat is transferred to the domestic water branch line 17 to heat the domestic water; the excess heat is transferred to the domestic water, realizing the cascade comprehensive utilization of the variable frequency air compressor 11.

[0038] Furthermore, the PLC control unit 3 includes a data acquisition unit 31, a judgment unit 32, and a control unit 33. The data acquisition unit 31 is electrically connected to the RO inlet water tank 21. The data acquisition unit 31 is connected to the judgment unit 32, and the judgment unit 32 is connected to the control unit 33. The control unit 33 is electrically connected to the first electric valve 24, the second electric valve 27, the third electric valve 26, the fourth electric valve 18, and the PID regulating valve 13, respectively. By acquiring the RO inlet water temperature, making a judgment, and finally constructing a complete control path based on the joint control of each valve, a closed-loop logic chain is constructed from temperature acquisition to internal judgment and then to valve control execution, making the system logic clear.

[0039] On the other hand, the present invention also provides a method for constant temperature and energy-saving control of RO pure water inlet based on waste heat of air compressor. The method employs the above-mentioned RO pure water inlet constant temperature and energy-saving control system based on waste heat of air compressor, and specifically includes the following steps:

[0040] S1: The acquisition unit 31 is used to acquire the RO inlet water temperature of the RO inlet water tank 21 to obtain the RO inlet water temperature;

[0041] S2: The judgment unit 32 is used to compare the RO inlet water temperature collected by the acquisition unit 31 with the built-in judgment formula;

[0042] S3: The control unit 33 is used to control the opening and closing of the first electric valve 24, the second electric valve 27, the third electric valve 26, the fourth electric valve 18, and the PID regulating valve 13 according to the judgment result of the judgment unit 32.

[0043] Further, in S3, the control unit 33 is used to control the opening and closing of the first electric valve 24, the second electric valve 27, the third electric valve 26, the fourth electric valve 18, and the PID regulating valve 13 according to the judgment result of the judgment unit 32, specifically as follows:

[0044] When the judgment unit 32 determines that the RO inlet water temperature is <20℃: the control unit 33 controls the first electric valve 24 to open and the second electric valve 27, the third electric valve 26, and the fourth electric valve 18 to close, thereby raising the temperature of the RO inlet water; when the judgment unit 32 determines that the RO inlet water temperature is between 20℃ and 25℃: the control unit 33 controls the maintenance of the valve position states of the PID regulating valve 13, the first electric valve 24, the second electric valve 27, the third electric valve 26, and the fourth electric valve 18 to remain unchanged, maintaining constant temperature operation; when the judgment unit 32 determines that the RO inlet water temperature is between 25℃ and 28℃: the control unit 33 controls the reduction of the PID regulating valve 13, the opening of the first electric valve 24, and the closing of the second electric valve 27, the third electric valve 26, and the fourth electric valve 18, reducing the transfer of residual heat; When the judgment unit 32 determines that the RO inlet water temperature is between 28 and 30°C (inlet water temperature greater than 28°C and less than or equal to 30°C): the control unit 33 controls the second electric valve 27 to open and the first electric valve 24, the third electric valve 26, and the fourth electric valve 18 to close, reducing waste heat transfer; when the judgment unit 32 determines that the RO inlet water temperature is greater than 30°C: the control unit 33 controls the PID regulating valve 13 to close and urgently cuts off the first electric valve 24, the second electric valve 27, and the fourth electric valve 18, while simultaneously opening the third electric valve 26; allowing the RO inlet water to enter the chilled water temperature regulating plate heat exchanger 22 for cooling, thereby reaching the preset temperature range; by controlling each valve through the PLC control unit 3, the system can operate stably and efficiently in any season or under different RO inlet water temperatures, thereby achieving the best effect.

[0045] For ease of understanding, the present invention will be further illustrated by the following embodiments:

[0046] Example 1

[0047] A temperature sensor is installed at the outlet of the RO inlet tank 21. The temperature sensor is electrically connected to the PLC control unit 3. The PLC control unit collects the signal generated by the temperature sensor in real time, makes judgments, and executes actions. During the operation of the variable frequency air compressor 11 in winter, the PLC control unit 3 detects and collects data through the temperature sensor. When the detected water temperature at the outlet of the RO inlet tank 21 is lower than 20°C, the judgment unit 32 determines that the current RO inlet water temperature is in a low-temperature state. The judgment unit 32 transmits the judgment result to the control unit 33 according to the judgment logic built into the PLC control unit 3. The control unit 33 then controls the first electric valve 24 to open and the second electric valve 27, the third electric valve 26, and the fourth electric valve 18 to close. At this time, all the water entering the RO inlet tank 21 enters the hot water temperature regulating plate heat exchanger 12 for heat exchange. When the inlet water temperature reaches the preset temperature range of 20~25℃, it is delivered to the RO reverse osmosis membrane system 23 through the RO booster pump 28. When the RO inlet water temperature is too low, the PLC control unit heats the RO inlet water temperature by adjusting the opening status of each valve until the inlet water temperature is in the optimal temperature range, ensuring that the RO membrane permeate flux will not decrease due to the low inlet water temperature.

[0048] Example 2

[0049] During the operation of the variable frequency air compressor 11 in summer when the acquisition unit 31 of the PLC control unit 3 detects that the water temperature at the outlet of the RO inlet water tank 21 is higher than 30℃, the judgment unit 32 determines that the current RO inlet water temperature is in an overheating state; the judgment unit 32 transmits the judgment result to the control unit 33 according to the judgment logic built into the PLC control unit 3; the control unit 33 controls the PID regulating valve 13 to close, and urgently cuts off the first electric valve 24, the second electric valve 27 and the fourth electric valve 18, while opening the... The third electric valve 26 is described; chilled water introduced from the external chilled water branch 25 enters the chilled water temperature regulating plate heat exchanger 22, so that the RO feed water enters the chilled water temperature regulating plate heat exchanger 22 for cooling; after cooling, it is then delivered to the RO reverse osmosis membrane system 23 through the RO booster pump 28; when the RO feed water temperature is too high, the PLC control unit cools the RO feed water temperature by adjusting the opening status of each valve until the feed water temperature is within the optimal temperature range, so as to avoid the RO membrane aging and damage caused by high temperature RO feed water and ensure the service life of the RO membrane under high temperature conditions.

[0050] Example 3

[0051] During the operation of the variable frequency air compressor 11 in spring and autumn, when the acquisition unit 31 of the PLC control unit 3 detects that the water temperature at the outlet of the RO inlet water tank 21 is in the optimal range of 20℃~25℃, the judgment unit 32 judges that the current RO inlet water temperature is in the optimal state; the judgment unit 32 transmits the judgment result to the control unit 33 according to the judgment logic built into the PLC control unit 3; the control unit 33 controls and maintains the valve position state of the PID regulating valve 13, the first electric valve 24, the second electric valve 27, the third electric valve 26 and the fourth electric valve 18 unchanged, maintaining constant temperature operation, and the RO inlet water directly enters the RO reverse osmosis membrane system 23 through the RO booster pump 28;

[0052] When the acquisition unit 31 of the PLC control unit 3 detects that the water temperature at the outlet of the RO inlet water tank 21 is between 25℃ and 28℃, the judgment unit 32 determines that the current RO inlet water temperature is too high. The judgment unit 32 transmits the judgment result to the control unit 33 according to the judgment logic built into the PLC control unit 3. The control unit 33 controls the PID regulating valve 13 to be reduced, the first electric valve 24 to be opened, and the second electric valve 27, the third electric valve 26, and the fourth electric valve 18 to be closed, thereby reducing the transfer of residual heat. Then, the water enters the RO reverse osmosis membrane system 23 through the RO booster pump 28. The RO inlet water temperature is already in or close to the optimal temperature range. The PLC control unit controls the opening of each valve to minimize heat exchange and stably deliver the inlet water to the RO reverse osmosis membrane system, thereby optimizing the system's energy consumption.

[0053] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A constant temperature and energy-saving control system for RO pure water inlet based on waste heat from an air compressor, characterized in that, include: The system comprises a waste heat recovery unit, an RO feed water heat utilization unit, and a PLC control unit. The waste heat recovery unit includes a variable frequency air compressor, a hot water temperature regulating plate heat exchanger, and a PID control valve. The RO feed water heat utilization unit includes an RO feed water tank, a chilled water temperature regulating plate heat exchanger, an RO booster pump, and an RO reverse osmosis membrane system. The waste heat recovery unit is connected to the RO feed water heat utilization unit, and the PLC control unit is electrically connected to both the waste heat recovery unit and the RO feed water heat utilization unit. In the waste heat recovery unit, the heat outlet of the variable frequency air compressor is connected to the heat inlet of the hot water temperature regulating plate heat exchanger via the PID control valve, the cold outlet of the hot water temperature regulating plate heat exchanger is connected to the cold inlet of the variable frequency air compressor, and the PID control valve is electrically connected to the PLC control unit. The RO... In the feed water heat utilization unit, the outlet of the RO feed water tank is connected to the inlet of the hot water temperature regulating plate heat exchanger, and the outlet of the hot water temperature regulating plate heat exchanger is connected to the inlet of the RO reverse osmosis membrane system. The waste heat recovery unit recovers the waste heat generated by the operation of the variable frequency air compressor and transfers the heat to the hot water temperature regulating plate heat exchanger for heat exchange of the feed water in the RO feed water tank. The RO feed water heat utilization unit is used to send the feed water in the RO feed water tank into the hot water temperature regulating plate heat exchanger, and use the waste heat generated by the variable frequency air compressor to exchange heat with the feed water. Then, the heated RO feed water is sent into the RO reverse osmosis membrane system through the RO booster pump. The PLC control unit is used to control the temperature of the feed water sent into the RO reverse osmosis membrane system according to the water temperature at the outlet of the RO feed water tank.

2. The RO pure water inlet constant temperature energy-saving control system based on air compressor waste heat according to claim 1, characterized in that, A first electric valve is installed on the pipeline connecting the hot water temperature regulating plate heat exchanger and the RO reverse osmosis membrane system. The first electric valve is electrically connected to the PLC control unit to control the flow of water from the hot water temperature regulating plate heat exchanger to the RO reverse osmosis membrane system pipeline.

3. The RO pure water inlet constant temperature energy-saving control system based on air compressor waste heat according to claim 1 or 2, characterized in that, The RO feed water heat utilization unit also includes a chilled water temperature regulating plate heat exchanger and a chilled water branch. The inlet of the chilled water branch is connected to the cold water inlet of the chilled water temperature regulating plate heat exchanger, and the cold water outlet of the chilled water temperature regulating plate heat exchanger is connected to the pipeline connected to the inlet of the RO reverse osmosis membrane system. The outlet of the RO feed water tank is connected to the hot water inlet of the chilled water temperature regulating plate heat exchanger. A third electric valve is installed on the pipeline connecting the RO feed water tank and the chilled water temperature regulating plate heat exchanger. The third electric valve is electrically connected to the PLC control unit. The PLC control unit controls the third electric valve to introduce external chilled water for cooling when the RO feed water temperature exceeds the preset temperature range.

4. The RO pure water inlet constant temperature energy-saving control system based on air compressor waste heat according to claim 1, characterized in that, The outlet of the RO feed water tank is also directly connected to the inlet of the RO reverse osmosis membrane system. A second electric valve is installed on the pipeline connecting the RO feed water tank and the RO reverse osmosis membrane system. The second electric valve is electrically connected to the PLC control unit. When the RO feed water temperature is within the preset temperature range, no heat exchange or cooling treatment is required, and the RO feed water is directly delivered to the RO reverse osmosis membrane system.

5. The RO pure water inlet constant temperature energy-saving control system based on air compressor waste heat according to claim 1, characterized in that, The waste heat recovery unit also includes an air compressor waste heat recovery plate heat exchanger; the inlet of the air compressor waste heat recovery plate heat exchanger is connected to the outlet of the variable frequency air compressor, the outlet of the air compressor waste heat recovery plate heat exchanger is connected to the inlet of the hot water temperature regulating plate heat exchanger through the PID regulating valve, the cold inlet of the air compressor waste heat recovery plate heat exchanger is connected to the cold outlet of the hot water temperature regulating plate heat exchanger, and the cold outlet of the air compressor waste heat recovery plate heat exchanger is connected to the cold inlet of the variable frequency air compressor; the waste heat generated by the operation of the variable frequency air compressor is transported to the RO inlet water heat utilization unit, and at the same time, the heat after heat exchange and cooling flows back to the variable frequency air compressor, realizing a closed-loop circulation of waste heat.

6. The RO pure water inlet constant temperature energy-saving control system based on air compressor waste heat according to claim 5, characterized in that, The waste heat recovery unit also includes an air compressor waste heat circulation pump and a hot water circulation pump. The inlet of the air compressor waste heat circulation pump is connected to the cold outlet of the air compressor waste heat recovery plate heat exchanger, and the outlet of the air compressor waste heat circulation pump is connected to the variable frequency air compressor. The inlet of the hot water circulation pump is connected to the cold outlet of the hot water temperature regulating plate heat exchanger, and the outlet of the hot water circulation pump is connected to the cold inlet of the air compressor waste heat recovery plate heat exchanger. Through the air compressor waste heat circulation pump and the hot water circulation pump, a heat circulation is formed between the variable frequency air compressor and the hot water temperature regulating plate heat exchanger, ensuring that waste heat is continuously delivered and efficiently utilized.

7. The RO pure water inlet constant temperature energy-saving control system based on air compressor waste heat according to claim 6, characterized in that, The waste heat recovery unit also includes a domestic water branch; a fourth electric valve is installed on the domestic water branch, and the domestic water branch is connected to the heat outlet of the air compressor waste heat recovery plate heat exchanger. The fourth electric valve is electrically connected to the PLC control unit. By adjusting the PID regulating valve and the fourth electric valve, when the RO inlet water heat utilization unit no longer needs waste heat, the excess heat is transferred to the domestic water branch to heat the domestic water.

8. The RO pure water inlet constant temperature energy-saving control system based on air compressor waste heat according to claim 7, characterized in that, The PLC control unit includes a data acquisition unit, a judgment unit, and a control unit. The data acquisition unit is electrically connected to the RO inlet water tank, the data acquisition unit is connected to the judgment unit, the judgment unit is connected to the control unit, and the control unit is electrically connected to the first electric valve, the second electric valve, the third electric valve, the fourth electric valve, and the PID regulating valve, respectively. By acquiring the RO inlet water temperature, making a judgment, and finally constructing a complete control path based on the joint control of each valve, a complete control path is formed.

9. A method for energy-saving control of RO pure water inlet temperature based on waste heat from air compressor, characterized in that, The RO pure water inlet constant temperature energy-saving control system based on air compressor waste heat as described in claim 8 specifically includes the following steps: S1: The acquisition unit is used to acquire the RO inlet water temperature of the RO inlet water tank to obtain the RO inlet water temperature; S2: The judgment unit is used to compare the RO inlet water temperature collected by the acquisition unit with the built-in judgment formula; S3: The control unit is used to control the opening and closing of the first electric valve, the second electric valve, the third electric valve, the fourth electric valve, and the PID regulating valve according to the judgment result of the judgment unit.

10. The method for constant temperature and energy-saving control of RO pure water inlet based on waste heat from air compressor as described in claim 9, characterized in that, In step S3, the control unit is used to control the opening and closing of the first electric valve, the second electric valve, the third electric valve, the fourth electric valve, and the PID regulating valve according to the judgment result of the judgment unit, specifically as follows: When the judgment unit determines that the RO inlet water temperature is <20℃: the control unit controls the first electric valve to open and the second electric valve, the third electric valve, and the fourth electric valve to close, thereby raising the temperature of the RO inlet water; When the judgment unit determines that the RO inlet water temperature is between 20 and 25°C: the control unit controls the PID regulating valve and the first, second, third, and fourth electric valves to maintain constant temperature operation. When the judgment unit determines that the RO inlet water temperature is between 25 and 28°C: the control unit controls the PID regulating valve to be adjusted to a lower setting, the first electric valve to be opened, and the second, third, and fourth electric valves to be closed, reducing the transfer of residual heat. When the judgment unit determines that the RO inlet water temperature is between 28 and 30°C (inlet water temperature greater than 28°C and less than or equal to 30°C): the control unit controls the second electric valve to be opened, and the first, third, and fourth electric valves to be closed, reducing the transfer of residual heat. When the judgment unit determines that the RO inlet water temperature is greater than 30°C: the control unit controls the PID regulating valve to be closed, and the first, second, and fourth electric valves to be shut off urgently, while the third electric valve is opened. The RO feed water is introduced into the chilled water temperature regulating plate heat exchanger for cooling, thereby reaching the preset temperature range.

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