Lithium bromide refrigerating unit heat source temperature control system and temperature control method

Abstract

The application discloses a lithium bromide refrigerating unit heat source temperature and pressure liquid collaborative temperature control system and method, aiming at solving the problem that only single temperature parameter is regulated in the existing closed heat source circulation system, which easily causes pressure imbalance, abnormal liquid level, and further leads to heat exchange efficiency reduction and pipeline component wear acceleration. The system is connected with a flue gas heat exchanger, a hot water pump and a plurality of lithium bromide refrigerating units through pipelines in sequence, and further comprises a water supplement device, an external discharge device and a monitoring device. The temperature control method realizes the collaborative control of temperature, pressure and liquid level by presetting pressure thresholds P1 and P2 and a liquid level safety interval, collecting system operation parameters in real time, and regulating and controlling corresponding logic based on parameter matching, so that the lithium bromide unit heat source import temperature can be stabilized, the system pressure and liquid level can be maintained in the safety interval, the service life of the equipment can be prolonged, and the operation energy consumption can be reduced.

Description

Technical Field

[0001] This invention relates to the field of lithium bromide refrigeration unit technology, specifically to a heat source temperature control system and method for a lithium bromide refrigeration unit. Background Technology

[0002] Lithium bromide absorption chillers are refrigeration devices driven by thermal energy, widely used in process cooling systems in industries such as metallurgy and chemicals. In metallurgical systems, the driving heat source for lithium bromide chillers is typically high-temperature hot water (demineralized water source) after heat exchange in a flue gas heat exchanger. After the hot water enters the lithium bromide chiller and completes secondary heat exchange, its temperature decreases. This cooled hot water is then sent back to the flue gas heat exchanger for further heat exchange and temperature increase, thus creating a closed-loop circulation system.

[0003] Chinese utility model patent CN216244970U discloses a thermal stabilization system for a lithium bromide refrigeration unit. It includes a hot water tank connected to the lithium bromide refrigeration unit via pipelines, with a first pressure transmitter, a second pressure transmitter, a first regulating valve, and a hot water pump sequentially installed on the pipeline between them. A vinyl chloride converter is located on the side of the lithium bromide refrigeration unit, and the two are connected via a first outlet pipeline. A first temperature transmitter is installed between the lithium bromide refrigeration unit and the vinyl chloride converter, and a second temperature transmitter is installed between the vinyl chloride converter and the second regulating valve. This stabilization system, through pressure and temperature interlocking, automatically adjusts the hot water supply and outlet bypass opening when the cooling capacity of the lithium bromide refrigeration unit fluctuates, ensuring a constant outlet hot water temperature for the lithium bromide refrigeration unit. A water replenishment valve is also installed at the top of the hot water tank for replenishing water to the system. However, this patented technology still has the following shortcomings: Firstly, it can only adjust the water supply flow rate and bypass opening, and cannot solve the problem of excessively high heat source water temperature. This system controls the hot water supply and outlet bypass opening through regulating valves, which is essentially a passive diversion and throttling method. When the heat source water temperature is too high (for example, the hot water temperature after heat exchange reaches 120℃, far exceeding the 90-100℃ required for normal operation of a lithium bromide unit), simply adjusting the flow rate and bypass opening cannot fundamentally reduce the heat source water temperature; the high-temperature hot water remains in the circulation system. Lithium bromide solution is prone to crystallization at excessively high temperatures, causing the chiller unit to malfunction.

[0004] Secondly, the system only focuses on maintaining a constant temperature, failing to address the issues of water loss and gas accumulation in the closed-loop system. Although the system has a water supply valve at the top of the hot water tank, it does not provide a systematic solution for the problems of water evaporation loss, increased high-temperature steam leading to increased system pressure, and gas accumulation after long-term operation of the closed-loop system. When the water volume in the closed-loop pipeline decreases, it is continuously heated by the heat exchanger, increasing the amount of high-temperature gas inside the pipes. This frequently causes flow interruption and water hammer phenomena, resulting in severe pipe vibration, fatigue cracking of the pipe walls, and significantly shortening the service life of the pipeline.

[0005] Furthermore, the lack of consideration for the recycling of high-temperature water resources leads to water waste. In this stabilization system, the hot water is cooled by a lithium bromide unit and then transported to the vinyl chloride converter, where it is heated back to its original temperature and returned to the hot water tank for circulation. However, this circulation system lacks a path for the discharge and recycling of high-temperature water. When the system requires water replacement or pressure regulation, the high-temperature water cannot be effectively recycled, resulting in water waste. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a lithium bromide chiller heat source temperature control system. By actively lowering the temperature of the driving heat source water entering the lithium bromide chiller, the system avoids lithium bromide solution crystallization, maintains stable pressure in the closed-loop pipeline, and enables the recycling and reuse of high-temperature demineralized water. This invention also provides a temperature control method that coordinates the three dimensions of temperature control, pressure control, and liquid level protection through an intelligent decision-making algorithm, achieving overall dynamic stability of the system.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The lithium bromide chiller heat source temperature control system includes a flue gas heat exchanger, a hot water pump, and several lithium bromide chillers connected in sequence by pipes, as well as a water supply device, an exhaust device, a monitoring device, and an intelligent control device. The water replenishment device includes a demineralized water station, a water supply pipeline leading out from the demineralized water station, a water supply pipeline connected to a water storage tank, a water storage tank having a water replenishment branch pipe connected to each lithium bromide refrigeration unit, a variable frequency water replenishment pump on each water replenishment branch pipe, and a pneumatic valve installed at the inlet of the water storage tank. The discharge device includes a discharge pipe connected to the outlet of the flue gas heat exchanger. The discharge pipe is equipped with a check valve and a pneumatic regulating valve, and the discharge pipe is connected to the demineralized water tank of the demineralized water station.

[0008] The monitoring device includes a first thermocouple and a first pressure transmitter installed at the outlet of the flue gas heat exchanger, a second thermocouple installed at the hot water inlet of each lithium bromide refrigeration unit, a level gauge installed on the water storage tank, and a flow meter installed on the discharge pipe.

[0009] The intelligent control device includes an intelligent processor, which has a built-in temperature change rate prediction algorithm module, a three-level pressure response algorithm module, a liquid level linkage control module, and a collaborative control decision module. The modules achieve data interaction and unified decision-making through a PLC or DCS system.

[0010] Furthermore, the water replenishment device also includes a premixed buffer tank, which is located between the water replenishment branch pipe and the water storage tank. The premixed buffer tank is also equipped with a heating connection pipe connected to the outlet of the flue gas heat exchanger.

[0011] Furthermore, an online conductivity meter is installed on the discharge pipe, and the discharge pipe is also equipped with a waste discharge branch pipe that switches to the wastewater collection tank.

[0012] The temperature control method of the heat source temperature control system of this lithium bromide refrigeration unit includes the following steps: S1: Real-time acquisition of flue gas heat exchanger outlet water temperature T1 and lithium bromide chiller inlet temperature T2; calculation of flue gas heat exchanger outlet water temperature change rate dT1 / dt; comprehensive judgment of water replenishment strategy based on change rate dT1 / dt and current temperature T1. S2: Real-time acquisition of the system pressure P of the first pressure transmitter, setting the first pressure threshold P1 and the second pressure threshold P2, and controlling the opening of the pneumatic regulating valve (14) on the discharge pipeline according to the comparison results of P with P1 and P2; S3: Real-time acquisition of the water level L in the storage tank, and control of the opening and closing of the pneumatic valve at the inlet of the storage tank and the operating frequency of the variable frequency water supply pump based on L; S4: Taking the inlet temperature T2 of the lithium bromide chiller unit as the first priority control target, the system pressure P as the constraint condition, and the liquid level L of the water storage tank as the guarantee condition, the water replenishment strategy, the exhaust strategy, and the liquid level control strategy are decided in a unified manner through a collaborative control algorithm.

[0013] Furthermore, the step S1, which involves comprehensively determining the water replenishment strategy based on the rate of change dT1 / dt and the current temperature T1, specifically includes: When dT1 / dt > +0.5℃ / min and T1 > 105℃, start the variable frequency water supply pump and run it at the first frequency; When dT1 / dt > +1.0℃ / min and T1 > 110℃, the frequency of the variable frequency water supply pump is increased to the second frequency, and the second frequency is greater than the first frequency; When T2 drops below 95℃ and dT1 / dt tends to stabilize, reduce the frequency of the variable frequency water supply pump to the third frequency to maintain micro-water supply.

[0014] Furthermore, the first frequency is 20Hz, the second frequency is 40-50Hz, and the third frequency is 10-15Hz.

[0015] Further, in step S2, the first pressure threshold P1 = 1.2P0, and the second pressure threshold P2 = 1.5P0, where P0 is the normal operating pressure of the system; The steps for controlling the opening of the pneumatic regulating valve on the discharge pipeline based on the comparison results of P with P1 and P2 specifically include: When P < P1, the pneumatic regulating valve is closed, and the system operates under pressure. When P1≤P<P2, the pneumatic regulating valve opens 15~20% to slowly exhaust and release pressure. When P≥P2, the pneumatic regulating valve is fully open, and at the same time, the frequency of the variable frequency water supply pump is reduced by interlock, triggering an alarm.

[0016] Furthermore, the steps in step S3, which involve controlling the opening and closing of the pneumatic valve at the inlet of the water storage tank and the operating frequency of the variable frequency water supply pump based on the liquid level L of the water storage tank, specifically include: When L < 1.5m, the pneumatic valve at the inlet of the water storage tank will be automatically opened to replenish the liquid; When L > 2.0m, close the pneumatic valve at the inlet of the water storage tank; When L < 1.2m, the maximum operating frequency of the variable frequency water supply pump is limited to no more than 30Hz; When L > 2.2m, close the inlet pneumatic valve and reduce the frequency of the variable frequency water supply pump to the third frequency.

[0017] Furthermore, the cooperative control algorithm described in step S4 specifically includes: When the temperature rises and the water supply needs to be increased, first determine the current pressure level of the system: If P < P1, adjust the frequency of the variable frequency water supply pump according to the temperature requirement; if P1 ≤ P < P2, open the pneumatic regulating valve simultaneously before water supply. If P≥P2, prioritize fully opening the pneumatic regulating valve to release pressure, and start water replenishment only after the pressure drops back to P<P2; During the water replenishment operation, if the water level in the storage tank L < 1.2m, the water replenishment frequency should be limited; if L > 2.2m, water replenishment should be stopped and the frequency reduced.

[0018] Furthermore, in the linkage control between the pneumatic valve at the inlet of the water storage tank and the level gauge: When the liquid level L rises from below 1.5m to 1.5m, the pneumatic valve opens and remains fully open until the liquid level rises to 2.0m. When the liquid level L drops from above 2.0m to 2.0m, the pneumatic valve remains closed and remains fully closed until the liquid level drops to 1.5m. The pneumatic valve has a hysteresis range of 0.5m when it opens and closes to prevent it from operating frequently when the liquid level fluctuates.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention continuously replenishes low-temperature demineralized water from the demineralized water station to the closed-loop pipeline, actively reducing the temperature of the heat source water. Combined with a predictive control algorithm based on the rate of temperature change, it achieves proactive intervention rather than delayed response, and can stably control the inlet water temperature of the lithium bromide chiller within the required range of 90-100℃, realizing dynamic and stable control of the heat source water temperature, and fundamentally eliminating the risk of lithium bromide solution crystallization.

[0020] 2. This invention is the first to unify and coordinate the three dimensions of temperature control, pressure control, and liquid level protection through an intelligent decision-making algorithm, solving the technical problem of multi-variable coupling in a closed-loop system, such as temperature rise leading to pressure rise, pressure rise affecting water replenishment, and water replenishment affecting liquid level, thus achieving overall dynamic stability of the system.

[0021] 3. This invention addresses the issue of pressure rise in closed-loop systems by establishing a three-level pressure gradient response mechanism. Differentiated venting and pressure relief strategies are adopted according to the pressure level, ensuring the system's tightness under normal operating conditions while enabling rapid response during abnormal pressure conditions. This fundamentally suppresses the occurrence of water hammer phenomena caused by flow interruption, avoids pipeline vibration and pipe wall fatigue cracking, and extends the service life of the pipeline.

[0022] 4. This invention reuses the discharged high-temperature water in the demineralized water tank and monitors the quality of the discharged water in real time using an online conductivity meter to ensure the quality of the recycled water and avoid water resource waste.

[0023] 5. This invention requires no additional cooling heat exchangers; it only requires the addition of a water supply device, an external drainage device, and an intelligent control device to the existing closed-loop system. The modification structure is simple and the modification cost is low, making it suitable for various lithium bromide chiller units that use high-temperature hot water as the driving heat source. Furthermore, this invention features fully automated intelligent control, significantly reducing maintenance workload. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0025] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the water replenishment device; Figure 3 This is a schematic diagram of the external discharge device; Figure 4 This is a schematic diagram illustrating the water flow direction of the present invention; Figure 5 This is a schematic diagram of the temperature prediction control process; Figure 6This is a schematic diagram of a three-stage pressure gradient control process; Figure 7 This is a block diagram of the temperature-pressure-liquid coordinated control logic. Reference numerals: 1. Flue gas heat exchanger; 2. Hot water pump; 3. Lithium bromide refrigeration unit; 4. Demineralized water station; 5. Water supply management; 6. Water storage tank; 7. Makeup water branch pipe; 8. Variable frequency water pump; 9. Pneumatic valve; 10. Premixed buffer tank; 11. Heating connection pipe; 12. External discharge pipe; 13. Check valve; 14. Pneumatic regulating valve; 15. Demineralized water tank; 16. Online conductivity meter; 17. Waste discharge branch pipe; 18. First thermocouple; 19. First pressure transmitter; 20. Second thermocouple; 21. Level gauge; 22. Flow meter. Detailed Implementation

[0026] 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do 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, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] like Figure 1The present invention provides a specific embodiment of a lithium bromide chiller heat source temperature control system, comprising a flue gas heat exchanger 1, a hot water pump 2, and several lithium bromide chiller units 3 connected sequentially via pipelines. This embodiment uses two lithium bromide chiller units 3, designated as Unit 1 and Unit 2, which are connected in parallel. Specifically, the outlet of the flue gas heat exchanger 1 is connected to the hot water pump 2 via a pipeline, the hot water pump 2 is connected to the inlet of each lithium bromide chiller unit 3 via a pipeline, and the outlet of each lithium bromide chiller unit 3 is connected to the inlet of the flue gas heat exchanger 1 via a pipeline. Thus, the flue gas heat exchanger 1, the hot water pump 2, and the several lithium bromide chiller units 3 are sequentially connected via pipelines to form a closed-loop main circulation pipeline. The system also includes a water replenishment device, an external discharge device, a monitoring device, and an intelligent control device.

[0030] The water replenishment device includes a demineralized water station 4, a water supply pipeline 5 leading out from the demineralized water station 4, the water supply pipeline 5 connecting to a water storage tank 6, and a water supply branch pipe 7 connected to each lithium bromide chiller unit 3. Each water supply branch pipe 7 is equipped with a variable frequency water supply pump 8. Specifically, in this embodiment, two variable frequency water supply pumps 8 are set, namely variable frequency water supply pump 1 and variable frequency water supply pump 2. A pneumatic valve 9 is installed at the inlet of the water storage tank 6.

[0031] More specifically, the water replenishment device also includes a premixed buffer tank 10, which is located between the water replenishment branch pipe 7 and the water storage tank. The premixed buffer tank 10 is also equipped with a heating connection pipe 11 connected to the outlet of the flue gas heat exchanger 1. Specifically, the heating connection pipe 11 is connected to a water pump and a valve that controls its opening and closing, such as... Figure 2 As shown, a heating connection pipe 11 is installed to allow low-temperature demineralized water (approximately 25-30°C) to first enter the premixing buffer tank. There, it is premixed with a small amount of high-temperature hot water drawn from the main circulation pipeline within the premixing buffer tank 10, raising the temperature of the makeup water to 50-60°C before being injected into the lithium bromide chiller unit 3 via the variable frequency water pump 8. This avoids the direct injection of low-temperature demineralized water into the high-temperature pipeline, which could cause excessive local thermal stress and lead to pipeline fatigue cracks. The temperature difference between the makeup water and the main circulation water is controlled within 40°C, improving mixing efficiency.

[0032] The discharge device includes a discharge pipe 12 connected to the outlet of the flue gas heat exchanger 2. The discharge pipe 12 is equipped with a check valve 13 and a pneumatic regulating valve 14, and the discharge pipe 12 is connected to the demineralized water tank 15 of the demineralized water station 4. Specifically, the discharge pipe 12 is connected to a water pump and a valve that controls its opening and closing. The demineralized water tank 15 is used to store and transport the water discharged by the discharge device. The output end of the demineralized water tank 15 is connected to the demineralized water station 4, which can transport the discharged water back to the demineralized water station 4 for re-purification. The treated water can be reused in the system as makeup water, thereby realizing the recycling of water resources, reducing water consumption during production and operation, and avoiding resource waste and additional environmental burden caused by direct discharge of wastewater.

[0033] In this embodiment, an online conductivity meter 16 is installed on the discharge pipe 12, and the discharge pipe 12 is also equipped with a wastewater branch pipe 17 that switches to the wastewater collection tank. Specifically, the wastewater branch pipe 17 is equipped with an electric valve, such as... Figure 3 As shown, the conductivity parameters of the external drainage body can be monitored in real time by the online conductivity meter 16. When the conductivity exceeds the preset qualified range, it is determined that the pollutant content of the water body does not meet the recycling requirements. At this time, the electric valve of the waste discharge branch pipe 17 is automatically opened to guide the unqualified water body into the wastewater collection tank for unified disposal by the subsequent wastewater treatment system. When the conductivity is within the preset qualified range, the electric valve of the waste discharge branch pipe 17 is closed to keep the main external discharge pipeline open, so that the water body that meets the recycling requirements can be smoothly discharged into the demineralized water tank 15 for subsequent recycling.

[0034] The monitoring device includes a first thermocouple 18 and a first pressure transmitter 19 installed on the outlet of the flue gas heat exchanger 1, and a second thermocouple 20 installed on the hot water inlet of each lithium bromide chiller unit 3. Specifically, the first thermocouple 18 and the first pressure transmitter 19 are used for the system temperature and pressure, respectively, and the second thermocouple 20 is used to monitor the inlet water temperature of each lithium bromide chiller unit 3 in real time. It also includes a level gauge 21 installed on the water storage tank 6 and a flow meter 22 installed on the outflow pipe 12. Specifically, the level gauge 21 is used to monitor the water level of the water storage tank in real time, and the flow meter 22 is used to monitor the hot water outflow of the outflow pipe 12 in real time. The collected flow data is transmitted to the system control unit in real time to provide accurate data support for the opening adjustment of the pneumatic regulating valve 14.

[0035] The intelligent control device includes an intelligent processor, which has a built-in temperature change rate prediction algorithm module, a three-level pressure response algorithm module, a liquid level linkage control module, and a collaborative control decision module. The modules achieve data interaction and unified decision-making through a PLC or DCS system.

[0036] Control logic: (1) Temperature prediction control: Real-time acquisition of the outlet water temperature T1 of flue gas heat exchanger 1 and the inlet temperature T2 of lithium bromide chiller 3, and calculation of the rate of change dT1 / dt of the outlet water temperature of flue gas heat exchanger 1; Based on the rate of change dT1 / dt and the current temperature T1, a comprehensive judgment is made on the water replenishment strategy. The temperature prediction control process diagram is shown below. Figure 5 As shown.

[0037] When dT1 / dt > +0.5℃ / min and T1 > 105℃, start the variable frequency water supply pump 8 and run it at the first frequency of 20Hz; When dT1 / dt > +1.0℃ / min and T1 > 110℃, the frequency of the variable frequency water supply pump 8 is increased to a second frequency of 40-50Hz. When T2 drops below 95℃ and dT1 / dt tends to stabilize, the frequency of the variable frequency water supply pump 8 is reduced to a third frequency of 10-15Hz to maintain a micro-water supply state.

[0038] The #1 and #2 variable frequency water supply pumps are backups for each other. When one of the pumps trips, the other will automatically start.

[0039] (2) Water level linkage of water storage tank 6: The water level L of water storage tank 6 is collected in real time, and the opening and closing of the pneumatic valve 9 at the inlet of water storage tank 6 and the frequency conversion are controlled according to L: When L < 1.5m, the pneumatic valve 9 at the inlet of the water storage tank 6 will be automatically opened to replenish the liquid; When L > 2.0m, close the pneumatic valve 9 at the inlet of water storage tank 6; When L < 1.2m, the maximum operating frequency of the variable frequency water supply pump 8 is limited to no more than 30Hz; When L > 2.2m, close the inlet pneumatic valve 9 and reduce the frequency of the variable frequency water supply pump 8 to the third frequency.

[0040] More specifically, when the liquid level L rises from below 1.5m to 1.5m, the pneumatic valve 9 opens and remains fully open until the liquid level rises to 2.0m; When the liquid level L drops from above 2.0m to 2.0m, the pneumatic valve 9 remains closed and remains fully closed until the liquid level drops to 1.5m. The pneumatic valve 9 has a hysteresis range of 0.5m when it is opened and closed to prevent it from operating frequently when the liquid level fluctuates.

[0041] (3) Three-stage pressure gradient control: The system pressure P of the first pressure transmitter 19 is collected in real time, and the first pressure threshold P1 = 1.2P and the second pressure threshold P2 = 1.5P0 are set, where P0 is the normal operating pressure of the system. The opening of the pneumatic regulating valve 14 on the discharge pipeline 12 is controlled according to the comparison results of P with P1 and P2. The schematic diagram of the three-stage pressure gradient control process is shown below. Figure 6 As shown.

[0042] The step of controlling the opening of the pneumatic regulating valve 14 on the discharge pipe 12 based on the comparison results of P with P1 and P2 specifically includes: When P < P1, the pneumatic regulating valve 14 is closed, and the system operates under pressure. When P1≤P<P2, the pneumatic regulating valve 14 opens 15~20% to slowly exhaust and release pressure. When P≥P2, the pneumatic regulating valve 14 is fully open, and at the same time, the frequency of the variable frequency water supply pump is reduced by interlocking, triggering an alarm.

[0043] (4) Cooperative control: Taking the inlet temperature T2 of the lithium bromide chiller unit 3 as the first priority control target, the system pressure P as the constraint condition, and the liquid level L of the water storage tank 6 as the guarantee condition, the water replenishment strategy, the exhaust strategy, and the liquid level control strategy are decided uniformly through the cooperative control algorithm. The logic block diagram of temperature, pressure, and liquid cooperative control is as follows. Figure 7 As shown.

[0044] When the temperature rises and the water supply needs to be increased, first determine the current pressure level of the system: If P < P1, adjust the frequency of the variable frequency water pump 8 according to the temperature requirement; if P1 ≤ P < P2, open the pneumatic regulating valve 14 simultaneously before water replenishment. If P≥P2, prioritize fully opening the pneumatic regulating valve 14 to release pressure, and start water replenishment only after the pressure drops back to P<P2; During the water replenishment operation, if the water level L in storage tank 6 is less than 1.2m, the water replenishment frequency should be limited; if L is greater than 2.2m, water replenishment should be stopped and the frequency reduced.

[0045] In the above control process, the water flow direction of the system is as follows: Figure 4 As shown in the diagram. Actual operation testing revealed that when the outlet water temperature of flue gas heat exchanger 1 was 120℃, the inlet temperature of lithium bromide chiller unit 3 was stably controlled within the range of 90-95℃ through the regulation of this system, fully meeting the operating temperature requirements of the chiller unit (90-100℃). System pressure fluctuations were reduced by more than 60%, and water hammer no longer occurred. All discharged high-temperature demineralized water was reused in the demineralized water tank. The system operates fully automatically without manual intervention.

[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A lithium bromide chiller heat source temperature control system, comprising a flue gas heat exchanger (1), a hot water pump (2), and several lithium bromide chillers (3) connected sequentially by pipes, characterized in that: Also includes The water replenishment device includes a demineralized water station (4), a water supply pipeline (5) leading out from the demineralized water station (4), the water supply pipeline (5) being connected to a water storage tank (6), the water storage tank (6) being provided with a water replenishment branch pipe (7) connected to each lithium bromide chiller unit (3), each water replenishment branch pipe (7) being provided with a variable frequency water replenishment pump (8), and a pneumatic valve (9) being installed at the inlet of the water storage tank (6). The external discharge device includes an external discharge pipe (12) connected to the outlet of the flue gas heat exchanger (1), the external discharge pipe (12) is provided with a check valve (13) and a pneumatic regulating valve (14), and the external discharge pipe (12) is connected to the demineralized water tank (15) of the demineralized water station (4). The monitoring device includes a first thermocouple (18) and a first pressure transmitter (19) installed at the outlet of the flue gas heat exchanger (1), a second thermocouple (20) installed at the hot water inlet of each lithium bromide chiller unit (3), a level gauge (21) installed on the water storage tank (6), and a flow meter (22) installed on the outflow pipe (12). The intelligent control device includes an intelligent processor, which has a built-in temperature change rate prediction algorithm module, a three-level pressure response algorithm module, a liquid level linkage control module, and a collaborative control decision module.

2. The lithium bromide refrigeration unit heat source temperature-pressure-liquid coordinated temperature control system according to claim 1, characterized in that: The water replenishment device also includes a premixed buffer tank (10), which is located between the water replenishment branch pipe (7) and the water storage tank (6). The premixed buffer tank (10) is also provided with a heating connection pipe (11) connected to the outlet of the flue gas heat exchanger (1).

3. The lithium bromide refrigeration unit heat source temperature-pressure-liquid coordinated temperature control system according to claim 2, characterized in that: An online conductivity meter (16) is installed on the discharge pipe (12), and the discharge pipe (12) is also equipped with a waste discharge branch pipe (17) that switches to the wastewater collection tank.

4. The temperature control method of the lithium bromide refrigeration unit heat source temperature-pressure-liquid coordinated temperature control system as described in claims 1 to 3, characterized in that: Includes the following steps: S1: Real-time acquisition of the outlet water temperature T1 of the flue gas heat exchanger (1) and the inlet temperature T2 of the lithium bromide chiller (3), and calculation of the rate of change dT1 / dt of the outlet water temperature of the flue gas heat exchanger (1); Based on the rate of change dT1 / dt and the current temperature T1, a comprehensive judgment is made on the water replenishment strategy; S2: Real-time acquisition of the system pressure P of the first pressure transmitter (19), setting the first pressure threshold P1 and the second pressure threshold P2, and controlling the opening of the pneumatic regulating valve (14) on the discharge pipeline (12) according to the comparison results of P with P1 and P2; S3: Real-time acquisition of the liquid level L of the water storage tank (6), and control the opening and closing of the pneumatic valve (9) at the inlet of the water storage tank (6) and the operating frequency of the variable frequency water supply pump (8) according to L; S4: Taking the inlet temperature T2 of the lithium bromide refrigeration unit (3) as the first priority control target, the system pressure P as the constraint condition, and the liquid level L of the water storage tank (6) as the guarantee condition, the water replenishment strategy, the exhaust strategy and the liquid level control strategy are decided in a unified manner through the collaborative control algorithm.

5. The temperature control method of the lithium bromide refrigeration unit heat source temperature-pressure-liquid coordinated temperature control system according to claim 4, characterized in that: The step S1, which involves comprehensively determining the water replenishment strategy based on the rate of change dT1 / dt and the current temperature T1, specifically includes: When dT1 / dt>+0.5℃ / min and T1>105℃, start the variable frequency water supply pump (8) to run at the first frequency; When dT1 / dt>+1.0℃ / min and T1>110℃, the frequency of the variable frequency water supply pump (8) is increased to the second frequency, and the second frequency is greater than the first frequency; When T2 drops below 95℃ and dT1 / dt tends to stabilize, the frequency of the variable frequency water supply pump (8) is reduced to the third frequency to maintain a micro-water supply state.

6. The temperature control method of the lithium bromide refrigeration unit heat source temperature-pressure-liquid coordinated temperature control system according to claim 5, characterized in that: The first frequency is 20Hz, the second frequency is 40-50Hz, and the third frequency is 10-15Hz.

7. The temperature control method of the lithium bromide refrigeration unit heat source temperature-pressure-liquid coordinated temperature control system according to claim 4, characterized in that: In step S2, the first pressure threshold P1 = 1.2P0, and the second pressure threshold P2 = 1.5P0, where P0 is the normal operating pressure of the system. The steps of controlling the opening degree of the pneumatic regulating valve (14) on the discharge pipeline based on the comparison results of P with P1 and P2 specifically include: When P < P1, the pneumatic regulating valve (14) is closed, and the system operates under pressure. When P1≤P<P2, the pneumatic regulating valve (14) is opened by 15-20% to slowly exhaust and release pressure; When P≥P2, the pneumatic regulating valve (14) is fully open, and at the same time, the frequency of the variable frequency water supply pump (8) is reduced by interlocking, triggering an alarm.

8. The temperature control method of the lithium bromide refrigeration unit heat source temperature-pressure-liquid coordinated temperature control system according to claim 4, characterized in that: The steps in step S3, which involve controlling the opening and closing of the pneumatic valve (9) at the inlet of the water storage tank (6) and the operating frequency of the variable frequency water supply pump (8) based on the liquid level L of the water storage tank (6), specifically include: When L < 1.5m, the pneumatic valve (9) at the inlet of the water storage tank (6) will be automatically opened to replenish the liquid; When L > 2.0m, close the pneumatic valve (9) at the inlet of the water storage tank (6); When L < 1.2m, the maximum operating frequency of the variable frequency water supply pump (8) is limited to no more than 30Hz; When L > 2.2m, close the inlet pneumatic valve (9) and reduce the frequency of the variable frequency water supply pump (8) to the third frequency.

9. The temperature control method of the lithium bromide refrigeration unit heat source temperature-pressure-liquid coordinated temperature control system according to claim 8, characterized in that: In the linkage control of the inlet pneumatic valve (9) of the water storage tank (6) and the level gauge (21): When the liquid level L rises from below 1.5m to 1.5m, the pneumatic valve (9) opens and remains fully open until the liquid level rises to 2.0m. When the liquid level L drops from above 2.0m to 2.0m, the pneumatic valve (9) remains closed and remains fully closed until the liquid level drops to 1.5m.

10. The temperature control method of the lithium bromide refrigeration unit heat source temperature-pressure-liquid coordinated temperature control system according to claim 4, characterized in that: The cooperative control algorithm described in step S4 specifically includes: When the temperature rises and the water supply needs to be increased, first determine the current pressure level of the system: If P < P1, adjust the frequency of the variable frequency water pump (8) according to the temperature requirement; if P1 ≤ P < P2, open the pneumatic regulating valve (14) simultaneously before water replenishment. If P≥P2, the pneumatic regulating valve (14) should be fully opened first to release pressure, and water replenishment should be started after the pressure drops back to P<P2; During the water replenishment operation, if the water level L in the storage tank (6) is less than 1.2m, the water replenishment frequency is limited; if L is greater than 2.2m, water replenishment is stopped and the frequency is reduced.

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