A waste heat-driven open absorption heat pump refrigeration system and a method for cooling water treatment.

Abstract

This invention provides a waste heat-driven open-type absorption heat pump refrigeration system and a method for cooling water treatment, relating to the field of cooling equipment technology. It includes: a main cooling tower, a negative pressure evaporator, a negative pressure water tank, an absorber, an auxiliary cooling tower, a cooler, a regenerator, a first heating unit, a second heating unit, and a concentration absorption tower. By constructing a synergistic closed-loop system of "circulating water cooling - waste heat recovery - wastewater concentration," the system achieves synergistic functionality of refrigeration and wastewater reduction.

Description

Technical Field

[0001] This invention relates to the field of cooling equipment technology, and more specifically, to a waste heat-driven open absorption heat pump refrigeration system and a method for cooling water treatment. Background Technology

[0002] In industrial production, cooling towers, as key cooling equipment, are widely used in industries such as power, chemical, and metallurgy. The temperature control of their circulating water directly affects the operating efficiency of the production system. Cooling tower wastewater is an important component of industrial wastewater, and its reduction treatment is of great significance for achieving water conservation and emission reduction goals. Currently, the industrial sector faces two major pain points: First, traditional cooling towers rely on air cooling or simple water cooling for temperature reduction, resulting in limited cooling efficiency of the circulating water. Especially in high-temperature environments, it is difficult to reduce the circulating water temperature to the low-temperature range required by the process, leading to increased energy consumption of subsequent production equipment. Second, cooling tower wastewater contains high salt and high suspended solids, making it difficult to treat. Traditional treatment methods mostly involve direct discharge or simple treatment before discharge, resulting in serious water waste and failing to meet the water conservation and emission reduction requirements under the "dual-carbon" strategy.

[0003] In existing technologies, circulating water cooling and wastewater reduction are mostly independent treatment systems, lacking coordinated design. While solution refrigeration technology can achieve deep cooling, its energy consumption is high when used alone. Although waste heat recovery technology can utilize industrial waste heat, it is not effectively integrated with cooling tower wastewater treatment, resulting in low energy and water resource utilization efficiency. Therefore, developing a comprehensive system that can synergistically achieve deep cooling of circulating water and efficient wastewater reduction, enhancing the cooling effect through solution refrigeration and using industrial waste heat to drive wastewater concentration, is key to overcoming current technological bottlenecks and has significant practical implications for improving industrial production energy efficiency and reducing water consumption.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide an open-type absorption heat pump refrigeration system driven by waste heat and a method for cooling water treatment, thereby constructing a synergistic closed-loop system of "circulating water cooling - waste heat recovery - wastewater concentration" to achieve synergistic functions of refrigeration and wastewater reduction.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a waste heat-driven open absorption heat pump refrigeration system, comprising: a main cooling tower, a negative pressure evaporator, a negative pressure water tank, an absorber, an auxiliary cooling tower, a cooler, a regenerator, a first heating unit, a second heating unit, and a concentration absorption tower. The main cooling tower includes a main cooling tower cooling water inlet, a main cooling tower cooling water outlet, a fresh air inlet, a fresh air outlet, and a main cooling tower wastewater outlet. The main cooling tower cooling water outlet is connected to the negative pressure evaporator, which has a cooling water outlet. A wastewater circulation pipeline is provided between the negative pressure evaporator and the negative pressure water tank. The negative pressure water tank also has a concentrated water outlet. The main cooling tower wastewater outlet is connected to the auxiliary cooling tower, which has an auxiliary cooling tower wastewater outlet connected to the negative pressure water tank. The negative pressure evaporator has a negative pressure steam outlet connected to the absorber, and the absorber is also connected to a vacuum pump to pump out the non-condensable gases in the absorber; the absorber has a cooling circulating water inlet and a cooling circulating water outlet, the cooling circulating water inlet is connected to the auxiliary cooling tower, and the cooling circulating water outlet is connected to the cooler, and the cooler and the auxiliary cooling tower are connected by a pipeline to realize the circulation of cooling circulating water; the absorber has a circulating hygroscopic solution outlet that is sequentially connected to the regenerator, the first heating unit, the second heating unit, the concentration absorption tower, the regenerator, the cooler, and the absorption tower to realize the circulation of hygroscopic solution; The first heating unit is connected to the concentration absorption tower via an intermediate circulating water pipeline; the second heating unit has an inlet and outlet for waste hot water and / or waste heat steam, and the concentration absorption tower has an inlet and outlet for fresh air. The auxiliary cooling tower has a fresh air inlet and a fresh air outlet.

[0007] The cooling water entering through the main cooling tower cooling water inlet includes, but is not limited to, cooling water from industries such as power, chemical, and metallurgy.

[0008] This invention organically integrates equipment such as a main cooling tower, a negative pressure evaporator, a negative pressure water tank, an absorber, an auxiliary cooling tower, a cooler, a regenerator, a heating unit, and a concentration absorption tower to construct a synergistic closed-loop system of "circulating water cooling - waste heat recovery - wastewater concentration". It utilizes a circulating hygroscopic solution and an absorber to deeply cool the circulating water in the cooling tower, improving the cooling effect. Simultaneously, it collects waste heat from industrial production (such as process exhaust steam and high-temperature wastewater waste heat) to provide heat for the concentration of the circulating hygroscopic solution. This heat is then used to absorb negative pressure steam and provides energy for the concentration of wastewater from the cooling tower, thus reducing wastewater volume. This system achieves synergistic cooling and wastewater reduction, significantly reducing energy and water consumption. It is suitable for various industrial cooling tower applications and boasts advantages such as high cooling efficiency, good wastewater reduction, energy saving, and environmental protection.

[0009] This invention employs a multi-stage collaborative system design to achieve extreme reduction in cooling tower wastewater volume. It innovatively constructs a multi-stage cascade treatment system consisting of a main cooling tower, auxiliary cooling tower, negative pressure water tank, and negative pressure evaporator, overcoming the reduction bottleneck of traditional single-stage treatment. First, the wastewater from the main cooling tower is used as makeup water for the auxiliary cooling tower, achieving preliminary cascade reuse of water resources and reducing the consumption of fresh makeup water. Then, the high-salt wastewater from the auxiliary cooling tower is sent to a negative pressure water tank for pressure stabilization and pretreatment, avoiding the impact of water quality fluctuations on subsequent concentration. Finally, the negative pressure evaporator serves as the core concentration unit, leveraging the low-pressure environment to enhance evaporation, converting most of the wastewater into negative pressure steam, with the remaining small amount of high-concentration brine entering a dedicated treatment system. This multi-stage process, through its tiered design of "reuse-pretreatment-deep concentration," significantly improves the wastewater reduction rate, achieving a reduction effect of over 70% compared to traditional single-stage concentration technology. It completely solves the industry pain points of large volumes and high treatment difficulty of cooling tower wastewater, while avoiding operational instability caused by excessive load on a single device, achieving both high efficiency and reliability in the wastewater reduction process.

[0010] A circulating hygroscopic solution directly absorbs negative pressure vapor, creating a highly efficient and environmentally friendly refrigeration mode. Abandoning the traditional high-energy-consumption approach of compression refrigeration, this innovative method uses a specialized solution with strong absorption properties (circulating hygroscopic solution) to directly absorb negative pressure vapor, achieving cooling of the circulating water through phase change heat absorption. The negative pressure vapor generated by the negative pressure evaporator comes into full contact with the low-temperature solution within the absorber. The vapor is rapidly captured and condensed by the solution, and the latent heat released during this process is carried away by the cooling water. The solution, in turn, absorbs the vapor, resulting in a change in its own concentration, laying the foundation for subsequent regeneration and circulation. This refrigeration method eliminates the need for complex compressor equipment, utilizing the direct absorption reaction between the solution and vapor to replace mechanical compression, reducing refrigeration energy consumption by more than 50% compared to traditional technologies. It also avoids the environmental impact of refrigerant leakage, and the cooling process is deeply coupled with wastewater evaporation, dynamically adapting the refrigeration efficiency to the amount of wastewater evaporation, achieving synergistic effects between refrigeration and wastewater treatment, and significantly improving the overall energy efficiency of the system.

[0011] This invention utilizes the cascade reuse of waste heat to achieve low-energy operation of wastewater concentration. It innovatively integrates low-grade waste heat within the plant (such as process exhaust steam and high-temperature wastewater waste heat) to construct an energy transfer chain of "waste heat-solution-wastewater," providing continuous power for wastewater concentration. First, the waste heat is transferred to the absorbed solution through a heating unit, enhancing the solution's regeneration capacity and achieving the first efficient utilization of waste heat. Subsequently, the solution exchanges heat with fresh air in the concentration absorption tower to release moisture, completing the regeneration cycle while indirectly ensuring the heat supply to the negative pressure evaporator. Finally, the negative pressure evaporator, supported by the system's waste heat and solution circulation, maintains a low-pressure evaporation environment, driving efficient wastewater concentration. This design transforms previously idle low-grade waste heat into the core energy source for wastewater concentration, replacing the traditional fossil fuel-driven mode. This eliminates the need for additional external energy consumption during the wastewater concentration process, reducing energy consumption by more than 60% compared to traditional electric-driven concentration technology. Simultaneously, it achieves a deep integration of waste heat resource utilization and wastewater concentration, solving the problem of industrial waste heat waste and reducing the operating costs of wastewater treatment, achieving a dual improvement in environmental and economic benefits.

[0012] In a preferred embodiment of the present invention, a cooling water bypass is also provided on the connecting pipe between the cooling water outlet of the main cooling tower and the negative pressure evaporator. The cooling water bypass merges with the cooling water pipe leading out from the cooling water outlet of the negative pressure evaporator. The circulating water that has been cooled by the enhanced cooling effect of negative pressure evaporation is fully mixed with the uncooled circulating water in the bypass to form a stable low-temperature circulating water, which is then re-supplied to the various cooling water users in the plant to meet their cooling needs.

[0013] In a preferred embodiment of the present invention, the concentrated water outlet of the negative pressure water tank is connected to the wastewater treatment equipment. After evaporation and concentration, the remaining small amount of high-concentration brine, due to its significantly reduced volume, is transported to the plant's wastewater treatment equipment or system for compliant disposal or resource recovery, ultimately achieving the goal of efficient reduction of the main cooling tower's wastewater volume.

[0014] In a preferred embodiment of the present invention, the main cooling tower also has a main cooling tower water inlet. Fresh water can be added according to water quality balance requirements.

[0015] In a preferred embodiment of the present invention, a pressure reducing valve is also provided on the circulating hygroscopic solution delivery pipeline between the cooler and the absorber.

[0016] In a preferred embodiment of the present invention, the concentration absorption tower has a heat exchange coil connected to an intermediate circulating water pipeline. The heat exchange coil can exchange heat with the heated fresh air. In the concentration absorption tower, a circulating hygroscopic solution at a certain temperature is sprayed, making full contact with the low-temperature fresh air for heat exchange, thereby removing some of the moisture from the circulating hygroscopic solution (increasing the humidity of the fresh air) and raising the temperature of the fresh air.

[0017] Secondly, the present invention also provides a method for cooling water treatment using an open absorption heat pump refrigeration system driven by waste heat. The method includes a cooling water cooling step, a circulating hygroscopic solution absorbing negative pressure steam, and cooling water circulation. The cooling water cooling step includes: introducing the cooling water to be treated into the main cooling tower for cooling water cooling, and then evaporating the cooled cooling water through a negative pressure evaporator to form low-temperature circulating water, which is then transported to the cooling water user; the wastewater discharged from the main cooling tower is used as makeup water to enter the auxiliary cooling tower to participate in the circulating cooling process of the auxiliary cooling tower, and the generated wastewater is transported to a negative pressure water tank for pressure stabilization treatment and then introduced into the negative pressure evaporator as a cold source. Part of the wastewater is converted into low-temperature negative pressure steam, and the remaining concentrated water is treated for sewage discharge. The process of circulating hygroscopic solution absorbing negative pressure steam includes: the negative pressure steam after heat exchange enters the absorber from the negative pressure evaporator and exchanges heat with the circulating hygroscopic solution; the circulating hygroscopic solution, having absorbed the heat of the negative pressure steam, enters the regenerator, the first heating unit, and the second heating unit in sequence; the idle low-grade waste heat is used to heat the circulating hygroscopic solution, which then enters the concentration absorption tower and comes into direct contact with fresh air. The fresh air is used as the moisture-carrying gas, and the sprayed circulating hygroscopic solution exchanges heat with the fresh air. The concentrated high-temperature circulating hygroscopic solution is sent to the regenerator to exchange heat with the low-temperature circulating hygroscopic solution to be heated to achieve preliminary cooling, and then enters the cooler for deep cooling, before flowing back to the absorber to continuously absorb the negative pressure steam generated by the negative pressure evaporator; The cooling water circulation includes: the circulating cooling water in the auxiliary cooling tower first enters the absorber to absorb heat, and the cooling water carrying the waste heat enters the cooler to exchange heat with the circulating hygroscopic solution to be cooled to obtain heated cooling water. The heated cooling water flows back to the auxiliary cooling tower, fully contacts the introduced fresh air to cool it down, and then is transported to the absorber.

[0018] Specifically, in the cooling water refrigeration process: Hot water heated by users within the plant is pumped back to the main cooling tower. Inside the main cooling tower, the hot water comes into full contact with the introduced ambient temperature fresh air, undergoing initial cooling through heat exchange. Simultaneously, fresh water is added according to water quality balance requirements, and some high-salt wastewater is discharged. After partial cooling, the cooling water enters the negative pressure evaporator. Inside the negative pressure evaporator, the low-pressure environment lowers the boiling point of the wastewater, causing it to evaporate rapidly and absorb a large amount of heat from the circulating water, achieving deep cooling of the circulating water. The circulating water, after enhanced cooling by negative pressure evaporation, mixes thoroughly with the bypassed, uncooled circulating water to form a stable low-temperature circulating water, which is then returned to the plant's cooling water users to meet their cooling needs. After heat exchange at the user end, the circulating water is heated again and pumped back to the main cooling tower, repeating the process of "fresh air pre-cooling + negative pressure evaporation deep cooling," thus constructing a highly efficient closed-loop circulating water refrigeration system.

[0019] In the process of absorbing negative pressure steam with circulating hygroscopic solution, a low-temperature solution with strong absorption performance (circulating hygroscopic solution) is sent into the absorber, where it comes into full contact with the negative pressure steam generated by the negative pressure evaporator and is absorbed efficiently, causing the steam to condense quickly and the solution temperature to rise. The large amount of heat released by the solution during the absorption of negative pressure steam is then absorbed by the circulating water in the auxiliary cooling tower. The solution that has absorbed steam sequentially enters the regenerator and heating unit, gradually increasing in temperature by utilizing idle low-grade waste heat within the plant (such as process exhaust steam and high-temperature wastewater waste heat). It then enters the concentration absorption tower and comes into direct contact with low-temperature fresh air, which serves as the humidifying gas. The low-temperature fresh air enters the lower part of the concentration absorption tower and directly contacts the sprayed solution for heat exchange, increasing its temperature and moisture content. After being demisted by the demister at the top of the concentration absorption tower, it is discharged. The concentrated high-temperature circulating hygroscopic solution is sent to the regenerator to exchange heat with the low-temperature circulating hygroscopic solution to be heated, achieving initial cooling. It then enters the cooler for deep cooling, returning to its initial low-temperature state before flowing back to the absorber to continuously absorb steam generated by the negative pressure evaporator, forming a stable circulating solution absorption system.

[0020] In the wastewater concentration process, the high-salt wastewater discharged from the main cooling tower is first transported as makeup water to the auxiliary cooling tower, participating in the circulating cooling process of the auxiliary cooling tower and achieving preliminary cascade utilization of water resources. Wastewater generated during the operation of the auxiliary cooling tower, due to further salt enrichment, is temporarily stored in a negative pressure water tank. After pressure stabilization, it is introduced into the negative pressure evaporator as a cold source. Under the low-pressure environment of the negative pressure evaporator, the wastewater fully absorbs heat and evaporates in large quantities, with most of the water converted into negative pressure steam, providing a cold source and medium for the circulating water cooling and solution absorption processes. After evaporation and concentration, the remaining small amount of high-concentration brine, due to its significantly reduced volume, is transported to the plant's wastewater treatment system for compliant disposal or resource recovery, ultimately achieving the goal of highly efficient volume reduction of the main cooling tower wastewater.

[0021] In the cooling water circulation process, the circulating cooling water in the auxiliary cooling tower is first pumped into the absorber, where it absorbs the large amount of heat released by the solution during the absorption of negative pressure steam, causing its own temperature to rise. The cooling water, carrying residual heat, then enters the cooler, where it indirectly exchanges heat with the circulating hygroscopic solution to be cooled, helping the solution quickly restore its low-temperature absorption performance, while the cooling water temperature rises further. The high-temperature cooling water, after heat exchange, flows back to the auxiliary cooling tower, where it comes into full contact with the introduced fresh air, achieving cooling through evaporative cooling and restoring its cooling capacity. It is then pumped back to the absorber to continuously absorb the heat generated during the solution absorption process, constructing a stable and efficient closed-loop cooling water circulation system, providing a reliable guarantee for the continuous operation of the solution absorption system.

[0022] In a preferred embodiment of the present invention, in the cooling water refrigeration step, the circulating water that has been cooled by negative pressure evaporation is mixed with the uncooled circulating water from the cooling water bypass to form low-temperature circulating water, which is then delivered to the cooling water user.

[0023] In a preferred embodiment of the present invention, the concentration absorption tower has a heat exchange coil. The intermediate circulating water flowing out of the first heating unit enters the heat exchange coil for heat exchange and then flows back to the first heating unit. The heat exchange coil is located at the top of the concentration absorption tower.

[0024] In a preferred embodiment of the present invention, the cooling water to be treated in the main cooling tower exchanges heat with the introduced fresh air to achieve cooling of the cooling water, and at the same time, water is replenished from the water inlet of the main cooling tower according to the water quality balance requirements.

[0025] Compared with the prior art, the beneficial effects of the present invention are: This invention constructs a multi-stage cascade treatment system consisting of "main cooling tower → auxiliary cooling tower → negative pressure water tank → negative pressure evaporator". Through a stepped design of "reuse-pretreatment-deep concentration", it significantly improves the wastewater reduction rate, achieving a reduction effect of more than 70% compared to traditional single-stage concentration technology. It completely solves the industry pain points of large volume and high treatment difficulty of cooling tower wastewater, while avoiding the problem of unstable operation caused by excessive load on a single device, thus achieving high efficiency and reliability in the reduction process.

[0026] The circulating hygroscopic solution provided by this invention can directly absorb negative pressure steam, constructing a highly efficient and environmentally friendly refrigeration mode. This refrigeration method eliminates the need for complex compressor equipment, utilizing the direct absorption reaction between the solution and steam to replace mechanical compression work, reducing refrigeration energy consumption by more than 50% compared to traditional technologies. Simultaneously, it avoids the environmental impact caused by refrigerant leakage, and the cooling process is deeply coupled with wastewater evaporation, dynamically adapting the refrigeration efficiency to the amount of wastewater evaporation, achieving synergistic effects between refrigeration and wastewater treatment, and significantly improving the overall energy utilization efficiency of the system.

[0027] This invention utilizes the cascade reuse of waste heat to achieve low-energy operation of wastewater concentration. It innovatively integrates low-grade waste heat within the plant (such as process exhaust steam and high-temperature wastewater waste heat) to construct an energy transfer chain of "waste heat-solution-wastewater," providing continuous power for wastewater concentration. This design transforms previously idle low-grade waste heat into the core energy source for wastewater concentration, replacing the traditional fossil fuel-driven model. This eliminates the need for additional external energy consumption during the wastewater concentration process, reducing energy consumption by more than 60% compared to traditional electric-driven concentration technology. Simultaneously, it achieves a deep integration of waste heat resource utilization and wastewater concentration, solving the problem of industrial waste heat waste and reducing the operating costs of wastewater treatment, thus achieving a dual improvement in environmental and economic benefits. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 One of the structural schematic diagrams of an open absorption heat pump refrigeration system driven by waste heat; Figure 2 The second schematic diagram of an open absorption heat pump refrigeration system driven by waste heat.

[0030] Icons: 1-Main cooling tower; 2-Negative pressure evaporator; 3-Cooling water users within the plant; 4-Auxiliary cooling tower; 5-Absorber; 6-Negative pressure water tank; 7-Sewage treatment system; 8-Cooler; 9-Pressure reducing valve; 10-Regenerator; 11-First heating unit; 12-Second heating unit; 13-Concentration absorption tower; 14-Fresh air inlet; 15-Fresh air outlet; 16-Main cooling tower cooling water inlet; 17-Main cooling tower cooling water outlet; 18-Main cooling tower wastewater outlet; 19-Main cooling tower water makeup outlet; 20-Negative pressure steam outlet; 21-Concentrated water outlet; 22-Auxiliary cooling tower wastewater outlet; 23-Sewage circulation pipeline. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0033] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0034] In the description of this invention, it should be noted that the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0035] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0036] Example 1 Please see Figure 1 and Figure 2 This embodiment provides a waste heat-driven open absorption heat pump refrigeration system, which includes: a main cooling tower 1, a negative pressure evaporator 2, a negative pressure water tank 6, an absorber 5, an auxiliary cooling tower 4, a cooler 8, a regenerator 10, a first heating unit 11, a second heating unit 12, and a concentration absorption tower 13. The main cooling tower 1 has a main cooling tower cooling water inlet 16, a main cooling tower cooling water outlet 17, a fresh air inlet 14, a fresh air outlet 15, a main cooling tower wastewater outlet 18, and a main cooling tower water makeup inlet 19.

[0037] The cooling water to be cooled enters the main cooling tower 1 through the cooling water inlet 16. In the main cooling tower 1, it comes into full contact with the introduced ambient temperature fresh air and completes the initial cooling through heat exchange. At the same time, fresh water is added according to the water quality balance requirements, and some high-salt wastewater is discharged to the auxiliary cooling tower 4 through the wastewater outlet 18 of the main cooling tower for further wastewater cooling treatment.

[0038] The cooling water outlet 17 of the main cooling tower is connected to the negative pressure evaporator 2. In the negative pressure evaporator 2, the boiling point of the wastewater is reduced by the low pressure environment, so that the wastewater evaporates quickly and absorbs a large amount of heat from the cooling water entering the negative pressure evaporator 2, thereby achieving deep cooling of the cooling water.

[0039] The negative pressure evaporator 2 has a cooling water outlet connected to each cooling water user 3 within the plant. Furthermore, the circulating water, after being cooled by the enhanced negative pressure evaporation, can be thoroughly mixed with the bypass circulating water that has not been cooled, forming a stable low-temperature circulating water, which is then returned to each cooling water user 3 within the plant to meet their cooling needs. After completing heat exchange at the user end, the circulating water is heated again and pumped back to the main cooling tower 1, repeating the process of "fresh air pre-cooling + negative pressure evaporation deep cooling," thus constructing a highly efficient closed-loop circulating water cooling system.

[0040] A wastewater circulation pipeline 23 connects the negative pressure evaporator 2 and the negative pressure water tank 6. The negative pressure water tank 6 also has a concentrated water outlet 21. Wastewater from the main cooling tower 1 is first transported as makeup water to the auxiliary cooling tower 4, participating in the circulating cooling process of the auxiliary cooling tower 4 to achieve preliminary cascade utilization of water resources. The auxiliary cooling tower 4 has a fresh air inlet 14 and a fresh air outlet 15. In the auxiliary cooling tower 4, heat exchange and reduction of water content in wastewater are achieved through fresh air. Wastewater generated during the operation of the auxiliary cooling tower 4, due to further salt enrichment, is discharged through the auxiliary cooling tower wastewater outlet 22 and transported to the negative pressure water tank 6 for temporary storage. After pressure stabilization, it is introduced into the negative pressure evaporator 2 as a cold source. Under the low-pressure environment of the negative pressure evaporator 2, the wastewater fully absorbs heat and evaporates in large quantities, with most of the water being converted into negative pressure steam, providing a cold source and medium for the circulating water cooling and solution absorption processes. After evaporation and concentration, the remaining small amount of high-concentration brine, due to its significant volume reduction, is transported to the plant's wastewater treatment system 7 for compliant disposal or resource recovery, ultimately achieving the goal of efficient volume reduction of wastewater discharged from the main cooling tower 1.

[0041] The negative pressure evaporator 2 has a negative pressure steam outlet 20 connected to the absorber 5, and the absorber 5 is also connected to a vacuum pump to pump out the non-condensable gas in the absorber 5; the absorber 5 has a cooling circulating water inlet and a cooling circulating water outlet, the cooling circulating water inlet is connected to the auxiliary cooling tower 4, and the cooling circulating water outlet is connected to the cooler 8, and the cooler 8 and the auxiliary cooling tower 4 are connected by a pipeline to realize the circulation of cooling circulating water; the absorber 5 has a circulating hygroscopic solution outlet connected in sequence to the regenerator 10, the first heating unit 11, the second heating unit 12, the concentration absorption tower 13, the regenerator 10, the cooler 8 and the absorber 5 to realize the circulation of hygroscopic solution; the circulating hygroscopic solution conveying pipeline between the cooler 8 and the absorber 5 is also equipped with a pressure reducing valve 9.

[0042] A low-temperature circulating hygroscopic solution with strong absorption properties is fed into absorber 5, where it comes into full contact with and efficiently absorbs the negative pressure steam generated by negative pressure evaporator 2, causing the steam to condense rapidly and the solution temperature to rise. The solution then absorbs the large amount of heat released during the absorption of negative pressure steam through the circulating water in auxiliary cooling tower 4. The solution that has absorbed steam then enters regenerator 10 and heating unit in sequence, gradually increasing its temperature by utilizing idle low-grade waste heat in the plant (such as process exhaust steam and high-temperature wastewater waste heat). Subsequently, it enters concentration absorption tower 13 and comes into direct contact with low-temperature fresh air, which serves as the humidifying gas. The low-temperature fresh air enters the lower part of concentration absorber 5 and directly contacts the sprayed solution for heat exchange, increasing its temperature and moisture content. After being demisted by the demister at the top of concentration absorber 5, the solution is discharged. The concentrated high-temperature solution is then sent to regenerator 10 to exchange heat with the low-temperature solution to be heated for initial cooling. It then enters cooler 8 for deep cooling, returning to its initial low-temperature state before flowing back to absorber 5 to continuously absorb steam generated by negative pressure evaporator 2, forming a stable circulating solution absorption system.

[0043] The first heating unit 11 is connected to the concentration absorption tower 13 by an intermediate circulating water pipeline; the second heating unit 12 has a waste hot water and / or waste heat steam inlet and outlet, and the concentration absorption tower 13 has a fresh air inlet 14 and outlet. The concentration absorption tower 13 has a heat exchange coil, which is connected to the intermediate circulating water pipeline.

[0044] The cooling water circulation process in the above system is as follows: The circulating cooling water in the auxiliary cooling tower 4 is first pumped into the absorber 5, where it absorbs the large amount of heat released by the solution during the absorption of negative pressure steam, causing its own temperature to rise. The cooling water, carrying residual heat, then enters the cooler 8, where it indirectly exchanges heat with the circulating hygroscopic solution to be cooled, helping the solution quickly restore its low-temperature absorption performance, while the cooling water temperature rises further. The high-temperature cooling water, having completed its heat exchange mission, flows back to the auxiliary cooling tower 4, where it comes into full contact with the introduced fresh air, achieving cooling through evaporative cooling and restoring its cooling capacity. It is then pumped back to the absorber 5 to continuously absorb the heat generated during the solution absorption process, constructing a stable and efficient closed-loop cooling water circulation system, providing a reliable guarantee for the continuous operation of the solution absorption system.

[0045] Example 2 This embodiment provides a method for treating high-salt cooling wastewater generated during the production process of a chemical enterprise and providing circulating cooling water for equipment within the plant.

[0046] A chemical company generates high-salt cooling wastewater during its production process, which also needs to provide circulating cooling water for the equipment in the plant (equipment outlet water temperature 40℃). It is necessary to simultaneously achieve "circulating water cooling + wastewater reduction".

[0047] I. The core operating parameters are as follows: Circulating water parameters: The outlet water temperature of the cooling water in the plant is 40℃, and the flow rate is 3000t / h; the water temperature after cooling in the main cooling tower 1 is 34℃, and the flow rate is 3000t / h; the flow rate of the circulating water treated by the negative pressure evaporator is 3000t / h, and the water temperature after cooling is 31℃.

[0048] Wastewater discharge parameters: Wastewater discharge from main cooling tower 1: 30t / h; wastewater discharge from auxiliary cooling tower 4: 15t / h; concentrated brine from negative pressure evaporator 2: 3t / h (reduction rate 90%).

[0049] Solution and residual heat parameters: Circulating absorbent solution flow rate: 500t / h, initial temperature 43℃; Waste hot water / exhaust steam in the plant: flow rate 320t / h, temperature 90℃; Fresh air parameters: Concentrated absorption tower 13, fresh air volume 100,000 Nm³ / h, temperature 30℃ (moisture content 3%).

[0050] II. System Operation Flow 1. Circulating water cooling process The 40℃ hot water (3000t / h) of the cooling water users in the plant is returned to the main cooling tower 1, where it directly exchanges heat with the fresh air and is cooled to 34℃; Two-way circulating water system at 34℃: 2000t / h is fed into negative pressure evaporator 2 via a bypass, and 1000t / h enters negative pressure evaporator 2; Wastewater discharged from the negative pressure evaporator 2 evaporates under a low pressure of -97 kPa.G, absorbing heat from the circulating water. After the 1000 t / h circulating water cools to 25°C, it merges with the 2000 t / h, 34°C circulating water. The resulting 3000 t / h, 31°C circulating water is then transported to the cooling water user, heated, and sent to the main cooling tower 1, completing the refrigeration closed loop.

[0051] 2. Wastewater Reduction Process Wastewater (30t / h) from the main cooling tower 1 is sent to the auxiliary cooling tower 4 as makeup water; Wastewater (15t / h) from auxiliary cooling tower 4 is sent to negative pressure water tank 6 for pressure stabilization, and then introduced into negative pressure evaporator 2; Wastewater in negative pressure evaporator 2 evaporates to generate 12t / h of negative pressure steam, and the remaining 3t / h of concentrated brine is sent to wastewater treatment system 7, achieving a 90% reduction in wastewater volume.

[0052] 3. Solution absorption and waste heat utilization process.

[0053] A circulating absorbent solution of 500t / h and 43℃ enters the absorber 5 to absorb the negative pressure steam of the negative pressure evaporator 2, increasing the flow rate to 512t / h. The heat is absorbed by the cooling water in the auxiliary cooling tower 4, and the temperature remains unchanged. The 512t / h, 43℃ solution is heated to 52℃ by the regenerator 10, and then heated to 80℃ by the heating units 1 and 2 (using the 90℃ residual hot water in the plant); The 80℃ solution is fed into the concentration absorption tower 13 and comes into contact with 100,000 Nm³ / h of fresh air at 30℃ with a moisture content of 3%. The fresh air is heated and the moisture content is raised to 15% before being discharged. The flow rate of the concentrated solution is 500t / h and the temperature is 60℃.

[0054] The concentrated 500t / h, 60℃ solution is cooled to 43℃ by the regenerator 10 and the cooler 8, and then circulated in the reflux absorber 5.

[0055] 4. Cooling water circulation process The 1600t / h circulating water (34℃) from the auxiliary cooling tower 4 is sent to the absorber 5, where it absorbs heat and rises to 37℃. Cooling water at 37°C is fed into cooler 8, and after cooling the solution, it is heated to 40°C and then returned to auxiliary cooling tower 4. The fresh air in the auxiliary cooling tower 4 cools the cooling water to 34°C and then sends it to the absorber 5 to complete the cooling water closed loop.

[0056] IV. Operational Results Circulating water cooling: The inlet water temperature of the equipment in the plant is stably controlled at 34℃, and the energy consumption of equipment operation is reduced by 28%; Wastewater discharge reduction: 30t / h of wastewater ultimately produces only 3t / h of concentrated brine, a reduction rate of 90%; Energy saving effect: Using waste hot water within the plant to replace purchased energy; Stability: No scaling or corrosion issues after 180 days of continuous operation, reducing equipment maintenance costs by 35%.

[0057] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A waste heat-driven open-type absorption heat pump refrigeration system, characterized in that, It includes: main The system comprises a cooling tower, a negative pressure evaporator, a negative pressure water tank, an absorber, an auxiliary cooling tower, a cooler, a regenerator, a first heating unit, a second heating unit, and a concentration absorption tower. The main cooling tower includes a main cooling tower cooling water inlet, a main cooling tower cooling water outlet, a fresh air inlet, a fresh air outlet, and a main cooling tower wastewater outlet. The main cooling tower cooling water outlet is connected to the negative pressure evaporator, which has a cooling water outlet. A wastewater circulation pipeline connects the negative pressure evaporator and the negative pressure water tank. The negative pressure water tank also has a concentrated water outlet. The main cooling tower wastewater outlet is connected to the auxiliary cooling tower, which has an auxiliary cooling tower wastewater outlet connected to the negative pressure water tank. The negative pressure evaporator has a negative pressure steam outlet connected to the absorber, and the absorber is also connected to a vacuum pump to pump out non-condensable gases from the absorber; the absorber has a cooling circulating water inlet and a cooling circulating water outlet, the cooling circulating water inlet is connected to the auxiliary cooling tower, and the cooling circulating water outlet is connected to the cooler, the cooler and the auxiliary cooling tower are connected by a pipeline to achieve the circulation of cooling circulating water; the absorber has a circulating hygroscopic solution outlet that is sequentially connected to a regenerator, a first heating unit, a second heating unit, a concentration absorption tower, a regenerator, a cooler, and an absorption tower to achieve the circulation of the hygroscopic solution; The first heating unit is connected to the concentration absorption tower via an intermediate circulating water pipeline; the second heating unit has an inlet and outlet for waste hot water and / or waste heat steam, and the concentration absorption tower has an inlet and outlet for fresh air; The auxiliary cooling tower has a fresh air inlet and a fresh air outlet.

2. The waste heat-driven open absorption heat pump refrigeration system according to claim 1, characterized in that, The cooling water outlet of the main cooling tower and the connecting pipe of the negative pressure evaporator are also provided with a cooling water bypass, which merges with the cooling water pipe leading out of the cooling water outlet of the negative pressure evaporator.

3. The waste heat-driven open absorption heat pump refrigeration system according to claim 2, characterized in that, The concentrated water outlet of the negative pressure water tank is connected to the sewage treatment equipment.

4. The waste heat-driven open absorption heat pump refrigeration system according to claim 2, characterized in that, The main cooling tower also has a main cooling tower water inlet.

5. The waste heat-driven open absorption heat pump refrigeration system according to claim 1, characterized in that, The circulating hygroscopic solution delivery pipeline between the cooler and the absorber is also equipped with a pressure reducing valve.

6. The waste heat-driven open absorption heat pump refrigeration system according to claim 1, characterized in that, The concentration absorption tower has a heat exchange coil, which is connected to the intermediate circulating water pipeline.

7. A method for cooling water treatment based on the waste heat-driven open absorption heat pump refrigeration system according to any one of claims 1-6, characterized in that, It includes a cooling water refrigeration step, a circulating hygroscopic solution absorbing negative pressure steam, and cooling water circulation. The cooling water refrigeration step includes: introducing the cooling water to be treated into the main cooling tower for cooling water temperature reduction, and then evaporating the cooled water through a negative pressure evaporator to form low-temperature circulating water, which is then delivered to the cooling water user; the wastewater discharged from the main cooling tower is used as makeup water to enter the auxiliary cooling tower to participate in the auxiliary cooling tower's circulating cooling process, and the generated wastewater is transported to a negative pressure water tank for pressure stabilization treatment and then introduced into the negative pressure evaporator as a cold source, where part of the wastewater is converted into low-temperature negative pressure steam, and the remaining concentrated water is discharged as wastewater. The process of the circulating hygroscopic solution absorbing negative pressure steam includes: the negative pressure steam after heat exchange enters the absorber from the negative pressure evaporator and exchanges heat with the circulating hygroscopic solution; the circulating hygroscopic solution, having absorbed the heat of the negative pressure steam, sequentially enters the regenerator, the first heating unit, and the second heating unit; the idle low-grade waste heat is used to heat the circulating hygroscopic solution, which then enters the concentration absorption tower and comes into direct contact with fresh air. The fresh air is used as the moisture-carrying gas, and the sprayed circulating hygroscopic solution exchanges heat with the fresh air. The concentrated high-temperature circulating hygroscopic solution is sent to the regenerator to exchange heat with the low-temperature circulating hygroscopic solution to be heated to achieve preliminary cooling, and then enters the cooler for deep cooling, before flowing back to the absorber to continuously absorb the negative pressure steam generated by the negative pressure evaporator; The cooling water circulation includes: the circulating cooling water in the auxiliary cooling tower first enters the absorber to absorb heat, and the cooling water carrying the residual heat enters the cooler to exchange heat with the circulating hygroscopic solution to be cooled to obtain heated cooling water. The heated cooling water flows back to the auxiliary cooling tower, fully contacts the introduced fresh air to cool it down, and then is transported to the absorber.

8. The method according to claim 7, characterized in that, In the cooling water refrigeration step, the circulating water that has been cooled by negative pressure evaporation is mixed with the uncooled circulating water from the cooling water bypass to form low-temperature circulating water, which is then delivered to the cooling water user.

9. The method according to claim 7, characterized in that, The concentration absorption tower has a heat exchange coil. The intermediate circulating water flowing out of the first heating unit enters the heat exchange coil for heat exchange and then flows back to the first heating unit.

10. The method according to claim 7, characterized in that, The cooling water to be treated in the main cooling tower exchanges heat with the introduced fresh air to achieve cooling water cooling, and at the same time, water is replenished from the water inlet of the main cooling tower according to the water quality balance requirements.

Images