A double-coil phase change energy storage power plant circulating water cascade waste heat utilization system and method

Abstract

The application discloses a double-coil phase change energy storage power plant circulating water cascade waste heat utilization system and method, which comprises a circulating water buffer shunt tank, a cascade heat exchange assembly and a phase change energy storage tank body; the circulating water buffer shunt is provided with two water outlet lines, one of which is a bypass pipeline, and the other of which is connected to the cascade heat exchange assembly composed of a plate heat exchanger and a column heat exchanger through a heat exchange water supply branch, and sequentially supplies different temperature level heat sources for heating and breeding; the phase change energy storage tank is internally provided with two groups of insulated spiral coils, which form heat storage, heat release and return circuits respectively. The application realizes stable pressure through the buffer tank shunt, realizes waste heat staged utilization through two-stage heat exchangers, and adapts to two types of heating scenes; the double-coil independent circuits realize waste heat storage and load heat supplement and peak shaving, weaken the impact of water medium fluctuation on the heat exchange equipment, and solve the defects of single heat exchange, unstable heating, low waste heat utilization rate and the like of traditional equipment.

Description

Technical Field

[0001] This invention belongs to the field of power plant waste heat resource utilization and phase change energy storage technology, specifically involving a dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system and method. Background Technology

[0002] Thermal power plants continuously generate a large amount of low-temperature circulating water waste heat during operation. This waste heat is substantial, with a continuous and stable supply, and is a low-grade clean energy source that can be efficiently recovered. Currently, most thermal power plants do not utilize this waste heat for resource recovery, but instead directly dissipate it through cooling towers. This not only results in significant heat energy loss and low energy efficiency but also causes thermal pollution to the surrounding environment. Traditional waste heat utilization solutions for power plant circulating water often employ single-stage heat exchangers, resulting in a limited heat exchange model that fails to achieve tiered and layered utilization of waste heat. This makes it difficult to meet the diverse heating needs of different temperature scenarios, such as residential heating and aquaculture, leading to low adaptability and recovery rates. Furthermore, existing waste heat utilization systems generally lack phase-change energy storage and peak-shaving structures. The heating supply fluctuates entirely with the power plant unit load, failing to effectively store excess heat during periods of surplus and unable to supplement heat and stabilize pressure during peak heating loads and periods of insufficient waste heat, significantly impacting heating stability. In addition, conventional water circuit control structures are simple and cannot effectively buffer fluctuations in the temperature and flow of circulating water, which can easily impact heat exchange equipment and further reduce system operational stability and waste heat utilization efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide a dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system and method to solve the technical defects of existing power plant circulating water waste heat utilization methods, such as single method, inability to achieve cascade heat exchange, difficulty in adapting to heat demand in multiple scenarios, lack of energy storage peak-shaving capability, heating supply fluctuates with unit load, poor heating stability, weak water circuit regulation capability, easy impact of medium temperature and flow fluctuations on heat exchange equipment, and low waste heat utilization efficiency.

[0004] To achieve the above objectives, this application provides the following technical solution: The first aspect of this application provides a dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system, comprising: The circulating water buffer diversion tank has an inlet, a first outlet branch and a second outlet branch. The inlet is connected to the main circulating water pipe of the power plant, the first outlet branch is connected to the bypass pipeline of the circulating water side of the power plant, and the second outlet branch is connected to the cascade heat exchange assembly and forms a heat exchange water supply branch. The cascade heat exchange assembly includes a plate heat exchanger and a column heat exchanger. The plate heat exchanger has a hot-side channel and a cold-side channel. The hot-side channel is connected to the heat exchange water supply branch. The inlet of the cold-side channel is connected to the heating return water pipe, and the outlet of the cold-side channel leads out to the heating water supply pipe. The outlet of the hot-side channel is connected to the inlet of the hot-side channel of the column heat exchanger. The inlet of the cold-side channel of the column heat exchanger is connected to the aquaculture return water pipe, and the outlet of the cold-side channel leads out to the aquaculture water supply pipe. The phase change energy storage tank has an insulation layer fixedly laid on its inner wall, and two sets of mutually isolated spiral coils are arranged in the inner cavity of the tank. The two ends of one set of spiral coils are respectively connected to the heat exchange water supply branch to form a heat storage parallel circuit, and the two ends of the other set of spiral coils are respectively connected to the heating return water pipe to form a heat release parallel circuit.

[0005] In one optional embodiment, the power plant circulating water bypass pipeline and the heat exchange water supply branch are both equipped with branch control components. The branch control components are used to adjust the medium flow rate of the two outlet branches to stabilize the circulating water temperature flowing into the cascade heat exchange assembly.

[0006] In one optional embodiment, a second buffer tank is provided on the heating return water pipe. The two ends of the second buffer tank are respectively connected to the inlet of the cold side channel of the plate heat exchanger and the heat release parallel circuit, which is used to balance the flow rate and temperature of the heating return water.

[0007] In one optional embodiment, the insulation layer is made of aluminum silicate fiber cotton. The phase change energy storage tank is filled with a paraffin-based phase change heat transfer medium, and two sets of spiral coils are immersed in the paraffin-based phase change heat transfer medium.

[0008] In one optional embodiment, both the heat storage parallel circuit and the heat release parallel circuit are equipped with on / off valves; The on / off valve of the heat storage parallel circuit is located in the connecting pipe section between the heat exchange water supply branch and one of the spiral coils, while the on / off valve of the heat release parallel circuit is located in the connecting pipe section between the heating return water pipe and another spiral coil.

[0009] In one optional embodiment, temperature sensors are provided on the heat exchange water supply branch, the heating return water pipe, the heating water supply pipe, and the aquaculture water supply pipe.

[0010] In one alternative embodiment, the branch control component includes a water flow sensor for collecting the medium flow rate of the pipeline.

[0011] In one optional embodiment, two sets of spiral coils are arranged along the axial direction of the phase change energy storage tank, and the spiral coils are of equidistant spiral structure.

[0012] In one alternative embodiment, the hot-side channel outlet of the column heat exchanger is connected to a drain pipe, which is used to transport the power plant circulating water that has completed two-stage heat exchange to the power plant cooling tower.

[0013] A second aspect of this application provides a method for utilizing the waste heat of circulating water in a dual-coil phase change energy storage power plant, applied to the dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system as described above, comprising: The circulating water inside the main circulating water pipe of the power plant is fed into the tank through the inlet of the circulating water buffer distribution tank. The flow rate of the two branches is distributed by the branch control components on the power plant circulating water side bypass pipe and the heat exchange water supply branch, and the circulating water temperature delivered to the cascade heat exchange assembly is stabilized. The circulating water enters the hot side channel of the plate heat exchanger through the heat exchange water supply branch. The heating return water in the cold side channel of the plate heat exchanger absorbs heat and is heated up before being supplied externally by the heating water supply pipe. The circulating water then flows into the hot side channel of the column heat exchanger for secondary heat exchange. The aquaculture return water in the cold side channel of the column heat exchanger absorbs heat and is heated up before being output by the aquaculture water supply pipe. After the heat exchange is completed, the circulating water is transported to the power plant cooling tower along the drainage pipeline. When the power plant has surplus waste heat and the heating load is low, the on / off valve of the heat storage parallel circuit is opened, and high-temperature circulating water is introduced into a set of spiral coils in the phase change energy storage tank to exchange heat with the paraffin-based phase change heat transfer medium in the tank and store heat. During peak heating load periods and when the power plant's circulating water waste heat supply is insufficient, the on / off valve of the heat storage parallel circuit is closed, and the on / off valve of the heat release parallel circuit is opened. The heating return water flows through another set of spiral coils, relying on the phase change medium to store heat and heat the heating return water. Temperature sensors on the heat exchange water supply branch, heating return water pipe, heating water supply pipe, and aquaculture water supply pipe, together with the water flow sensor in the branch control component, collect medium temperature and flow data in real time, and automatically switch the cascade heat exchange, heat storage, and heat release operation modes in conjunction with each on / off valve.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. A circulating water buffer distribution tank is set up to realize the diversion and distribution of circulating water. Combined with plate heat exchangers and column heat exchangers, it forms a tiered heat exchange assembly, which can meet the differentiated heat needs of heating and aquaculture step by step. It solves the defects of traditional waste heat utilization methods, such as being single, unable to perform tiered heat exchange, and having limited adaptability. At the same time, two sets of independent spiral coils are set up to form a dual loop for heat storage and heat release, which has the ability to store energy and regulate peaks. It overcomes the problems of random fluctuations and poor stability of heating. The overall water circuit structure is optimized, the impact of medium fluctuations is reduced, and the efficiency of waste heat utilization is greatly improved.

[0015] 2. Branch control components are installed on the bypass pipeline and the heat exchange water supply branch, which can distribute and adjust the medium flow of the two branches in real time, stabilize the circulating water temperature entering the cascade heat exchange assembly, effectively make up for the deficiency of the traditional system's weak water circuit control capability, suppress drastic fluctuations in circulating water temperature and flow, avoid fluctuations impacting the heat exchange equipment, ensure the smooth and continuous cascade heat exchange process, and improve the system's heat exchange stability and waste heat utilization accuracy.

[0016] 3. A second buffer tank is installed in the heating return water pipe to balance the flow and temperature parameters of the heating return water, stabilize the heat release parallel loop water inlet conditions, solve the problems of large fluctuations in heating return water, uneven phase change heat release, and poor heating stability in traditional systems, effectively buffer water circuit parameter disturbances, improve the phase change heat release energy supplementation effect, ensure continuous and stable heating water supply at the terminal, and further optimize the reliability of system operation.

[0017] 4. The aluminum silicate fiber cotton insulation structure of the tank body and the paraffin-based phase change medium filling method, combined with the complete immersion arrangement of the coil, can effectively reduce the heat loss of the tank body, ensure the full progress of the phase change storage and heat release reaction, solve the problems of poor insulation, insufficient heat exchange and low energy storage efficiency of traditional energy storage structures, improve the heat accumulation and release efficiency of the phase change energy storage system, and ensure the stable realization of the waste heat energy storage peak shaving function.

[0018] 5. Independent on / off valves are installed in the corresponding pipe sections of the parallel circuits for heat storage and heat release, which can realize independent switching between heat storage and heat release modes without interference. This solves the defects of traditional energy storage systems, such as chaotic switching of operating modes and inability to adjust peak loads on demand. The operating mode can be accurately switched according to the surplus heat and heating load, improving the system's adaptability to operating modes and the flexibility of energy storage peak regulation.

[0019] 6. Temperature sensors are installed in each water supply and return water pipeline to monitor the temperature parameters of the system's heat exchange, heating, and aquaculture water supply in real time. This solves the problems of traditional systems having no parameter monitoring and uncontrollable operating status, providing accurate data support for subsequent linkage control and automatic switching of operating conditions, and improving the system's intelligent control capabilities and operational stability.

[0020] 7. Water flow sensors are configured in the branch control components to collect pipeline medium flow parameters in real time, which makes up for the shortcomings of traditional water circuits that can only simply pass water and have no flow monitoring. Combined with temperature monitoring, flow and temperature dual parameter sensing is formed, which provides a data foundation for precise adjustment of branch flow and stable control of heat exchange conditions, effectively improving the system's water circuit control accuracy and operating condition self-adaptation capability.

[0021] 8. The spiral coil adopts an axially equidistant spiral arrangement structure, which makes the contact between the coil and the phase change medium uniform and the heat exchange area sufficient. This solves the problems of uneven heat exchange, local heat exchange inefficiency, and uneven energy storage and heat release of traditional coils. It ensures that the waste heat is fully absorbed during the heat storage stage and the heat is released stably during the heat release stage, which significantly improves the phase change heat exchange efficiency and the system energy storage and pressure stabilization effect.

[0022] 9. The outlet of the column heat exchanger is connected to the drainage pipe and then to the power plant cooling tower, so that the circulating water after the two-stage heat exchange can be uniformly returned for heat dissipation. This solves the problem of disordered drainage and lack of fixed recovery path at the end of the cascade heat exchange, realizes closed-loop reuse of circulating water, standardizes the system water circulation logic, avoids thermal pollution caused by the random discharge of waste heat drainage, and ensures the continuous and stable operation of the unit's circulating water system. Attached Figure Description

[0023] 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.

[0024] Figure 1 A schematic diagram of a dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system provided by the present invention; Figure 2 A schematic diagram of the phase change energy storage tank in a dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system provided by the present invention. In the diagram: 1. First buffer tank; 2. Plate heat exchanger; 3. Column heat exchanger; 4. Phase change energy storage tank; 5. Second buffer tank; 6. Power plant circulating water main pipe; 7. Bypass return pipe; 8. Heat exchanger inlet pipe; 9. Solenoid valve; 10. Water flow sensor; 11. Temperature sensor; 12. First energy storage tank inlet pipe; 13. First energy storage tank outlet pipe; 14. User heating return pipe; 15. User heating inlet pipe; 16. Connecting pipe; 17. Aquaculture circulation return pipe; 18. Aquaculture circulation inlet pipe; 19. Second energy storage tank inlet pipe; 20. Second energy storage tank outlet pipe; 21. Insulation layer; 22. Phase change heat transfer medium; 23. Drainage pipe. Detailed Implementation

[0025] 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.

[0026] 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.

[0027] 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.

[0028] To address the technical deficiencies mentioned in the background section, this embodiment provides a dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system and method.

[0029] The present invention will now be described in further detail with reference to the accompanying drawings: like Figures 1-2 As shown, in a first aspect of the present invention, a dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system is provided, including a circulating water buffer distribution tank, which has an inlet, a first outlet branch, and a second outlet branch. The inlet is connected to the power plant circulating water main 6, the first outlet branch is connected to the power plant circulating water side bypass pipeline, and the second outlet branch is connected to the cascade heat exchange assembly and forms a heat exchange water supply branch. The cascade heat exchange assembly includes a plate heat exchanger 2 and a column heat exchanger 3. The plate heat exchanger 2 has a hot-side channel and a cold-side channel. The hot-side channel is connected to the heat exchange water supply branch, the inlet of the cold-side channel is connected to the heating return water pipe, and the outlet of the cold-side channel leads out to the heating supply water pipe. The outlet of the hot-side channel is connected to the inlet of the hot-side channel of the column heat exchanger 3. The inlet of the cold side channel of the column heat exchanger 3 is connected to the aquaculture return water pipe, and the outlet of the cold side channel leads out to the aquaculture supply water pipe; the phase change energy storage tank has an insulation layer 21 fixedly laid on its inner wall, and two sets of mutually isolated spiral coils are arranged in the inner cavity of the tank; the two ends of one set of spiral coils are respectively connected to the heat exchange water supply branch to form a heat storage parallel loop, and the two ends of the other set of spiral coils are respectively connected to the heating return water pipe to form a heat release parallel loop, which is used to recover the low-temperature waste heat transported by the power plant circulating water main 6. The cascade heat exchange is used to realize the graded heating for both heating and aquaculture scenarios. At the same time, the phase change energy storage tank 4 is matched to complete the heat peak shaving and valley filling, solving the industry pain points of existing waste heat equipment such as single heat exchange, unstable heating, lack of energy storage buffer, and water fluctuation impact on equipment.

[0030] The circulating water buffer diversion tank is the first buffer tank 1. Three types of pipe interfaces are opened on the surface of the tank: an inlet, a first outlet branch, and a second outlet branch. The inlet is sealed to the main circulating water pipe 6 of the power plant via a connecting pipe 16. During the operation of the power plant unit, the circulating cooling water carrying low-temperature waste heat can be continuously transported to the first buffer tank 1 for temporary storage and buffering through the main circulating water pipe 6. The first outlet branch extends outward to form a bypass return pipe 7. This bypass return pipe 7 serves as a bypass depressurization and diversion branch of the system, which can divert part of the circulating water directly back to the cooling tower, reducing the flow rate of the medium entering the heat exchange system. The second outlet branch extends outward to form a heat exchanger inlet pipe 8. The heat exchanger inlet pipe 8 serves as the main medium pipeline for transporting hot circulating water to the cascade heat exchange assembly. It is directly sealed to the heat exchange input end of the cascade heat exchange assembly, realizing the transport of waste heat medium to the heat exchange unit. Among them, the cascade heat exchange assembly is a two-stage series heat exchange structure, which is assembled by plate heat exchanger 2 and column heat exchanger 3 in series. The two-stage heat exchangers sequentially complete the high temperature difference heating heat exchange and the low temperature difference aquaculture heat exchange, realizing the cascade and graded utilization of waste heat, and fully matching the different heating temperature requirements of the two scenarios.

[0031] The internal space of the plate heat exchanger 2 is divided into a hot-side channel and a cold-side channel, which are isolated and have independent heat exchange. Heat is transferred between the hot and cold channels through metal heat exchange plates. The two media do not come into direct contact, thus eliminating the problem of media leakage and contamination. The medium input end of the hot-side channel of the plate heat exchanger 2 is sealed and connected to the heat exchanger inlet pipe 8. The power plant circulating water carrying waste heat is continuously introduced into the hot-side channel. The cold-side channel of the plate heat exchanger 2 is equipped with two types of pipe interfaces. The inlet pipe of the cold-side channel is connected to the user heating return pipe 14. The low-temperature heating return water is continuously introduced into the cold-side channel to exchange heat with the hot-side circulating water. The outlet pipe of the cold-side channel leads out to the user heating inlet pipe 15. The high-temperature heating water after being heated is transported to the heating terminals of the factory residents and office buildings through the user heating inlet pipe 15.

[0032] The medium outlet pipe of the hot side channel of plate heat exchanger 2 is sealed and connected to the inlet of the hot side channel of column heat exchanger 3 through connecting pipe 16. After the power plant circulating water completes the primary heating heat exchange and the temperature drops slightly, it flows directly into the interior of column heat exchanger 3 for secondary heat exchange. Column heat exchanger 3 also has separate hot side channel and cold side channel, and the hot and cold media are isolated by heat exchange through the pipe wall. The inlet of the cold side channel of column heat exchanger 3 is connected to the aquaculture circulation return pipe 17. The low-temperature aquaculture return water is passed into the cold side channel to absorb the residual heat in the circulating water. The outlet of the cold side channel leads out to the aquaculture circulation inlet pipe 18. The heated constant temperature aquaculture water is transported to the aquaculture pond to maintain the constant temperature of the aquaculture water and ensure the thermal environment required for the normal growth of aquatic products.

[0033] The phase change energy storage tank 4 adopts a sealed, pressure-resistant metal tank structure. A heat insulation layer 21 is fixedly laid on all inner wall surfaces of the tank, completely covering all inner wall surfaces, the top, and the bottom of the tank. This minimizes heat exchange losses between the internal medium and the outside air, reducing ineffective heat loss during the heat storage phase. Two sets of completely isolated spiral coils are arranged inside the internal cavity of the phase change energy storage tank 4. These two sets of spiral coils are not interconnected and each forms an independent fluid loop, corresponding to the heat storage and heat release functions respectively. The first set of spiral coils is connected to the first energy storage tank inlet pipe 12 and the first energy storage tank outlet pipe 13 at both ends, respectively. The first energy storage tank inlet pipe 12 and the first energy storage tank outlet pipe 13 are connected to the heat exchanger inlet via a connecting pipe 16. Water pipe 8 forms a parallel heat storage loop. During the surplus heat stage, high-temperature circulating water flows into the coil through the inlet pipe 12 of the first energy storage tank. After heat exchange, it flows out through the outlet pipe 13 of the first energy storage tank, transferring heat to the phase change heat medium 22 inside the tank to complete heat storage. The two ends of the second set of spiral coils are respectively connected to the inlet pipe 19 and the outlet pipe 20 of the second energy storage tank. The inlet pipe 19 and the outlet pipe 20 of the second energy storage tank are connected to the user's heating return pipe 14 through the connecting pipe 16, thus forming a parallel heat release loop. During the peak heating load stage, low-temperature heating return water flows into the coil through the inlet pipe 19 of the second energy storage tank to absorb heat. After the temperature rises, it flows out through the outlet pipe 20 of the second energy storage tank, absorbing the heat stored in the phase change heat medium 22 to complete the heat replenishment and temperature rise.

[0034] In this optional embodiment, branch control components are installed on both the bypass return pipe 7 and the heat exchanger inlet pipe 8. The branch control components of the two pipes are independently controlled and synchronously cooperate to complete the flow distribution. The function of the branch control components is to dynamically adjust the proportion of the power plant circulating water in the two outlet branches. By adjusting the flow rate of the bypass return pipe 7, the temperature of the circulating water flowing into the cascade heat exchange assembly is stabilized, eliminating the drastic fluctuations in the water supply temperature caused by the power plant unit load fluctuations, and avoiding temperature shock damage to the internal heat exchange elements of the plate heat exchanger 2 and the column heat exchanger 3.

[0035] The real-time changes in the power generation load of thermal power plant units directly affect the outlet water temperature and flow rate of the main circulating water pipe 6. Under high load conditions, the circulating water flow rate is large and the temperature is high. If all of it is fed into the heat exchange assembly, it will easily cause thermal stress deformation of the heat exchange plates. Under low load conditions, the circulating water flow rate is reduced and the waste heat temperature is low. If it is directly fed into the heat exchange assembly, it will lead to the heating and aquaculture water supply temperatures not meeting the standards.

[0036] This embodiment uses a branch control component that is synchronously matched with two pipelines to dynamically allocate flow according to real-time operating conditions: when the circulating water temperature is too high, the branch control component increases the opening of the bypass return pipe 7, increases the bypass diversion flow, reduces the total amount of medium entering the heat exchanger inlet pipe 8, and lowers the inlet water temperature of the cascade heat exchange assembly; when the circulating water temperature is too low and the waste heat is insufficient, the branch control component decreases the opening of the bypass return pipe 7, closes part of the bypass diversion, increases the medium flow in the heat exchanger inlet pipe 8, ensures that the total amount of waste heat medium entering the heat exchanger is sufficient, and stabilizes the temperature of the two types of terminal hot water supply.

[0037] The branch control components are assembled in sections along the pipeline axis and use flanges and connecting pipes 16 for sealing installation, which facilitates later maintenance, disassembly and replacement without damaging the original pipeline's overall sealing structure. It is suitable for existing power plant circulating water pipeline renovation construction scenarios, eliminating the need for large-scale cutting and replacement of the original main pipeline, resulting in lower renovation construction costs and shorter construction cycles. It solves the technical defects of traditional waste heat systems, such as the lack of flow distribution structure and the impact of water temperature fluctuations on heat exchange equipment, significantly extending the service life of plate heat exchangers 2 and column heat exchangers 3, and improving the long-term continuous operation stability of the entire system.

[0038] A second buffer tank 5 is added to the user's heating return pipe 14. The second buffer tank 5 is a sealed pressure tank with a bidirectional connecting pipe 16 interface. One end of the tank is connected to the inlet of the cold side channel of the plate heat exchanger 2, and the other end is connected to the heat release parallel loop pipeline. The second buffer tank 5 spans the main heating return water passage and the phase change heat release branch. In order to balance the instantaneous flow and temperature fluctuation of the heating return water, stabilize the water inlet conditions of the heat release parallel loop, ensure uniform heat release during the phase change heat release stage, and avoid fluctuations in the terminal heating temperature caused by sudden changes in the flow of the heating return water.

[0039] Residential heating in winter experiences significant periodic load fluctuations. During peak water usage periods in the morning, noon, and evening, the return water flow rate increases substantially, while it decreases significantly during off-peak hours at night. When these drastic flow rate changes directly flow into the heat release parallel circuit, they cause sudden changes in the flow velocity of the medium inside the spiral coil. This leads to continuous fluctuations in the heat exchange temperature difference between the coil and the phase change heat transfer medium 22, resulting in uneven heat release by the phase change medium. Sometimes the heat release is excessive, and sometimes it is insufficient. Ultimately, this causes the output water temperature of the user's heating inlet pipe 15 to fluctuate, resulting in poor heating comfort for the user.

[0040] In this embodiment, the heating return water is temporarily stored and buffered in the second buffer tank 5. When the instantaneous flow rate of the return water suddenly increases, the excess low-temperature return water is temporarily stored in the second buffer tank 5 and flows into the heat release circuit smoothly. When the return water flow rate decreases, the low-temperature return water stored in the buffer tank is continuously replenished to the heat release parallel circuit to maintain the stable flow rate of the medium inside the coil, ensure that the phase change medium releases the stored heat at a uniform speed and smoothly, and balance the heat exchange conditions of the heating return water.

[0041] Meanwhile, the second buffer tank 5 has a temperature homogenization function. There are slight temperature differences in the return water of heating systems at different times and in different buildings. The return water is fully mixed inside the buffer tank to eliminate local temperature differences before being uniformly transported to the plate heat exchanger 2 and the heat release parallel circuit. The inlet water temperature of the two-stage heat exchange and phase change heat replenishment process remains constant. The working conditions of the cascade heat exchange assembly and the phase change energy storage tank 4 are stable for a long time, reducing the losses caused by frequent changes in equipment operating conditions and further improving the heating stability and waste heat utilization uniformity of the entire system.

[0042] The second buffer tank 5 adopts a vertical tank installation method, with matching support feet for ground fixation. The connecting pipe 16 is arranged in layers to reduce the accumulation of air inside the return water and reduce the risk of air blockage in the pipeline. It is suitable for various installation scenarios in underground and ground equipment rooms in the factory area.

[0043] The internal insulation layer 21 of the tank is made of aluminum silicate fiber cotton. Aluminum silicate fiber cotton has the material characteristics of extremely low thermal conductivity, high temperature resistance, corrosion resistance, moisture resistance and long service life, which is suitable for the low temperature waste heat storage conditions of power plants. The insulation layer 21 adopts a multi-layer stacking process to completely fit the inner wall of the phase change energy storage tank 4, with no gaps or gaps between the layers. The top, bottom and side walls of the tank are completely covered, preventing the heat stored in the tank from being lost to the environment through the tank wall. Compared with polyurethane and rubber and plastic insulation materials, aluminum silicate fiber cotton will not age or crack in the long-term temperature range of 50℃~90℃ of the power plant circulating water waste heat, and its insulation performance will not decline over a long period of time, which will greatly reduce the ineffective heat loss during the heat storage stage and improve the utilization rate of waste heat storage.

[0044] The internal cavity of the phase change energy storage tank 4 is entirely filled with paraffin-based phase change heat transfer medium 22. The phase change temperature of the paraffin-based phase change medium is adapted to the waste heat range of 50~85℃ for power plant circulating water. In its solid state, the medium can stably store low-temperature heat. After being heated to the phase change temperature, it melts into a liquid state and absorbs a large amount of latent heat. When the heating return water flows through the coil at low temperature via the inlet pipe 19 of the second energy storage tank, the medium solidifies and stably releases latent heat to complete the heat replenishment. The paraffin-based medium has stable chemical properties, no corrosion, no volatility, and no risk of flammability or explosion. Long-term circulating phase change will not cause performance degradation, making it suitable for the long-term continuous operation of power plants. There is no need to frequently replace the phase change heat transfer medium 22 inside the tank, resulting in lower operation and maintenance costs.

[0045] Both sets of spiral coils are completely submerged inside the phase change heat transfer medium 22. The filling height of the phase change heat transfer medium 22 inside the tank completely covers all spiral pipe sections connected to the first energy storage tank inlet pipe 12, the first energy storage tank outlet pipe 13, the second energy storage tank inlet pipe 19, and the second energy storage tank outlet pipe 13. The coil walls are in full contact with the liquid and solid phase change heat transfer medium 22 in all directions, and there are no exposed coils or blind spots in heat exchange. During the heat storage stage, the high-temperature circulating water flows in through the first energy storage tank inlet pipe 12 and can quickly and evenly transfer heat to all media. During the heat release stage, the low-temperature return water flows in through the second energy storage tank inlet pipe 19 and can absorb the heat stored in the phase change medium in all directions, eliminating the industry defects of insufficient local heat exchange and low energy storage utilization. The heat storage capacity of the entire phase change energy storage unit is fully released. During the waste heat surplus stage, excess low-temperature heat can be stored to the maximum extent. During the peak heating period, a sufficient amount of supplementary heat source can be stably output.

[0046] Electromagnetic valves 9 are independently installed on the parallel heat storage loop and the parallel heat release loop. The electromagnetic valves 9 of the two types of loops are independently controlled and do not interact with each other. They can be opened and closed individually. The electromagnetic valve 9 corresponding to the parallel heat storage loop is fixedly installed on the connecting pipe 16 section between the heat exchanger inlet pipe 8 and the first energy storage tank inlet pipe 12. The upstream of the electromagnetic valve 9 is the high-temperature circulating water of the heat exchanger inlet pipe 8, and the downstream is the first energy storage tank inlet pipe 12 and the heat storage spiral coil. When the valve is fully open, the high-temperature waste heat medium can flow into the coil to complete the heat storage. When the valve is fully closed, all the medium in the heat exchanger inlet pipe 8 flows to the cascade heat exchange assembly and no longer supplies heat to the phase change energy storage tank 4. The system only performs pure cascade heat exchange operation mode. The electromagnetic valve 9 corresponding to the heat release parallel circuit is installed in the connecting pipe 16 section between the user heating return pipe 14 and the second energy storage tank inlet pipe 19. When the valve is open, the low-temperature heating return water flows into the heat release spiral coil through the second energy storage tank inlet pipe 19 to absorb the heat of the phase change medium. When the valve is closed, all the heating return water flows directly into the cold side channel of the plate heat exchanger 2 without passing through the phase change energy storage tank 4 for heat replenishment.

[0047] After each of the two circuits is independently equipped with a solenoid valve 9, the system can switch between three independent operating conditions: In the first operating condition, the solenoid valve 9 of the heat storage circuit is open and the solenoid valve 9 of the heat release circuit is closed, which corresponds to the power plant having surplus waste heat and low-load heating heat storage operation. The second operating condition is that the solenoid valve 9 of the heat storage circuit is closed and the solenoid valve 9 of the heat release circuit is open, which corresponds to the peak heating season and the heat release and heat supplementation operation when there is insufficient residual heat. In the third operating condition, both solenoid valves 9 are closed, and the system relies solely on the cascade heat exchange assembly to recover waste heat. There is no energy storage or supplementary heat process, making it suitable for balanced operating conditions where waste heat supply and heating load are perfectly matched. The solenoid valves 9 adopt a flange-connected direct-connection pipeline structure with connecting pipe 16, and are equipped with electric actuators. They can receive electrical signals from the control system for remote opening and closing, eliminating the need for manual on-site operation and meeting the requirements of power plant automation centralized control systems.

[0048] Temperature sensors 11 are installed on the heat exchanger inlet pipe 8, the user heating return pipe 14, the user heating inlet pipe 14, and the aquaculture circulation inlet pipe 18. The four pipes cover the entire process of waste heat inlet water, low temperature return water, heating outlet water, and aquaculture outlet water, realizing real-time online monitoring of the medium temperature of the entire system and providing complete temperature data support for the flow regulation of branch control components and the switching of the working conditions of electromagnetic valves 9.

[0049] Temperature sensor 11 on heat exchanger inlet pipe 8 is installed on the connecting pipe 16 section between the first buffer tank 1 and plate heat exchanger 2. It detects the initial temperature of the waste heat circulating water before entering the cascade heat exchange assembly in real time. The control system adjusts the opening of the branch control components according to the temperature data to stabilize the inlet water temperature of the heat exchanger. Temperature sensor 11 on user heating return pipe 14 detects the base temperature of the return water before entering the heat exchange and heat release circuit to determine the heating load level. Temperature sensor 11 on user heating inlet pipe 15 monitors the temperature of the external heating hot water in real time as the basis for heat supplementation adjustment. Temperature sensor 11 on aquaculture circulation inlet pipe 18 monitors the outlet water temperature after aquaculture heat exchange to ensure that the aquaculture water temperature meets the standard.

[0050] Temperature sensor 11 adopts a pipe insertion type assembly, with the sensing probe fully inserted into the medium inside the connecting pipe 16, avoiding data deviation caused by pipe wall temperature measurement, resulting in high temperature measurement accuracy and fast response speed. All temperature sensors 11 are uniformly connected to the power plant PLC control system through signal cables, uploading temperature values ​​in real time. The control system can comprehensively determine the current system supply and demand conditions based on the temperature of the four pipelines, automatically linking the branch control components and two solenoid valves 9 to complete adaptive adjustment, realizing unmanned automatic operation of the entire system, reducing the workload of manual on-site inspection and manual adjustment, and improving the intelligent management and control level of the waste heat recovery system.

[0051] The branch control component integrates a water flow sensor 10, which collects the instantaneous flow rate of the medium inside the bypass return pipe 7 and the heat exchanger inlet pipe 8 in real time. This data, together with the temperature data collected by the temperature sensor 11, forms a dual-dimensional operating parameter of temperature and flow rate.

[0052] Specifically, the water flow sensor 10 is embedded inside the branch control valve body and is integrated with the valve body, eliminating the need for additional drilling. Traditional waste heat systems rely solely on a single temperature parameter for control, making it difficult to identify flow fluctuations and leading to control deviations where the temperature meets the standard but the heat supply is insufficient. In this embodiment, the water flow sensor 10 collects the flow of the two branches in real time, allowing the control system to calculate the total waste heat power. When the total waste heat exceeds the total heat load at the terminal, the solenoid valve 9 of the heat storage circuit is automatically opened to store the excess heat. When the total waste heat cannot meet the heat demand at the terminal, the solenoid valve 9 of the heat release circuit is automatically opened to release the stored heat. This makes the control logic more precise and comprehensive, completely solving the problem of operating condition matching deviation caused by single-parameter control and improving the system's adaptive matching capability for heat supply and demand.

[0053] In this embodiment, both sets of spiral coils are arranged along the central axis of the phase change energy storage tank 4. The coils adopt an equidistant spiral forming structure, with the spacing between two adjacent coils being completely equal, and the overall outer and inner diameters of the coils remaining uniform.

[0054] If the spiral coil spacing is uneven, the phase change heat transfer medium 22 inside the tank will exhibit localized intense heat transfer and localized weak heat transfer: in the dense coil area (sections 12 and 13 of the first energy storage tank inlet pipe), the phase change medium rapidly undergoes phase change for heat storage, while in the sparse coil area, the medium cannot fully exchange heat for a long time, resulting in insufficient utilization of the phase change medium inside the tank and a significant reduction in effective energy storage capacity.

[0055] This embodiment adopts an axially equidistant spiral arrangement, with the coils evenly distributed along the height of the tank. The heat exchange surfaces of the coils are evenly distributed throughout the upper, middle, and lower parts of the tank. Every area of ​​the phase change heat transfer medium 22 can fully contact the coils. During the heat storage stage, the heat is evenly diffused to all media. During the heat release stage, the media releases latent heat synchronously and stably. The overall effective energy storage capacity of the tank is fully utilized. Under the same tank volume conditions, the waste heat storage capacity is increased, and the heat storage and heat release response speeds are uniform and stable.

[0056] The two sets of spiral coils are arranged independently and in a staggered axial configuration. The coils of the first energy storage tank inlet pipe 12 and the first energy storage tank outlet pipe 13 on the heat storage side are not attached to or in contact with the coils of the second energy storage tank inlet pipe 19 and the second energy storage tank outlet pipe 20 on the heat release side. The phase change heat transfer medium 22 is filled in between to form a heat insulation and heat exchange layer. The high-temperature medium in the heat storage circuit will not directly transfer heat to the low-temperature return water in the heat release circuit, thus eliminating the ineffective heat loss caused by direct heat exchange between the two coils in the tank. The heat storage and heat release circuits of the phase change energy storage tank 4 work completely independently and do not interfere with each other, further improving the heat utilization efficiency of the entire system.

[0057] In this optional embodiment, the outlet of the hot side channel of the column heat exchanger 3 is connected to the drain pipe 23 through the connecting pipe 16. The drain pipe 23 is laid along the underground pipe gallery of the plant area, and the end of the pipe is uniformly connected to the water inlet of the original cooling tower of the power plant. The drain pipe 23 uniformly transports the low-temperature power plant circulating water after the two-stage heat exchange of the plate heat exchanger 2 and the column heat exchanger 3 to the power plant cooling tower, forming a complete closed-loop circulation circuit of power plant circulating water.

[0058] After the power plant circulating water carrying waste heat completes the first-stage heat exchange for heating and the second-stage heat exchange for aquaculture, the remaining low-grade waste heat inside the medium is basically released, the water temperature drops significantly, and it no longer has the value of heating. It is then uniformly transported to the cooling tower through the drainage pipe 23, where the water temperature is further reduced by the air cooling of the cooling tower. The cooled low-temperature circulating water flows back to the power plant unit cooling system and re-enters the power plant circulating water main pipe 6 to complete the circulation. There is no need to add additional independent cooling equipment, and the existing cooling tower facilities of the power plant can be directly reused, which greatly reduces the investment cost of the entire waste heat system's supporting equipment.

[0059] Meanwhile, the drainage pipe 23 enables centralized management of wastewater after heat exchange, avoiding the messy pipeline problems caused by separate drainage and scattered laying of connecting pipes 16 for the two-stage heat exchangers, and facilitating later pipeline maintenance and leakage investigation; all circulating water after heat exchange is centrally returned to the cooling tower, eliminating disorderly direct discharge and local thermal pollution problems, meeting the environmental emission control requirements of thermal power plants, and eliminating the defects of local temperature rise and ecological thermal pollution caused by the dispersed drainage of traditional waste heat equipment. The drainage pipe 23 is equipped with a one-way check valve to prevent backflow of cooling water inside the cooling tower, avoid dilution and contamination of the medium inside the column heat exchanger 3, and extend the service life of the plate heat exchanger 2 and the plate tube bundle of the column heat exchanger 3.

[0060] A second aspect of the present invention provides a method for utilizing the waste heat of circulating water in a dual-coil phase change energy storage power plant, applied to the dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system as described above, comprising: S1. During the continuous operation of the power plant unit, the low-temperature waste heat circulating water is continuously transported to the first buffer tank 1 along the main circulating water pipe 6 of the power plant. The first buffer tank 1 performs primary buffering and temporary storage of the instantaneous flow rate. After the medium enters the tank, it is diverted to two paths: the bypass return pipe 7 and the heat exchanger inlet pipe 8. The branch control components installed on the bypass return pipe 7 and the heat exchanger inlet pipe 8 synchronously read the medium parameters collected by the water flow sensor 10 and the temperature sensor 11. The control system dynamically adjusts the flow opening of the two branches according to the real-time temperature and flow rate values, allocates the flow rate ratio of the two mediums, and stably delivers the circulating water temperature into the heat exchanger inlet pipe 8 and to the cascade heat exchange assembly.

[0061] When the power plant unit is under high load and the circulating water inlet temperature and flow rate are high, the branch control components increase the flow rate of the bypass return pipe 7, diverting the medium to flow into the cooling tower through the drain pipe 2, reducing the total medium volume in the heat exchanger inlet pipe 8, and lowering the inlet water temperature of the plate heat exchanger 2. When the unit is under low load and waste heat is insufficient, the opening of the bypass return pipe 7 is reduced, increasing the flow rate of the heat exchanger inlet pipe 8, ensuring sufficient waste heat supply to the plate heat exchanger 2 and column heat exchanger 3, and stabilizing the outlet water temperature of the user heating inlet pipe 15 and the aquaculture circulating inlet pipe 18. This step is a pretreatment process to eliminate inherent fluctuations in the water circuit and provide constant medium conditions for stable cascade heat exchange.

[0062] S2. The circulating water, after being diverted and stabilized, flows into the hot side channel of the plate heat exchanger 2 through the heat exchanger inlet pipe 8; the low-temperature return water from the user heating return pipe 14 enters the cold side channel of the plate heat exchanger 2 to complete the first-stage heat exchange, and the heating medium is output for heating through the user heating inlet pipe 15; the circulating water after heat exchange and cooling flows into the hot side channel of the column heat exchanger 3 through the connecting pipe 16, and the return water from the aquaculture circulation return pipe 17 enters the cold side for secondary heat exchange, and the heating medium is sent out through the aquaculture circulation inlet pipe 18; the low-temperature circulating water after all heat exchange is returned to the power plant cooling tower through the drain pipe 23 to complete the complete closed-loop circulation of the medium.

[0063] S3, temperature sensor 11, and water flow sensor 10 collect parameters of heat exchanger inlet pipe 8, user heating inlet pipe 15, and aquaculture circulation inlet pipe 18 in real time. When the waste heat supply is greater than the terminal load, the system opens the heat storage circuit solenoid valve 9. High-temperature circulating water flows into the first energy storage tank inlet pipe 12 along the heat exchanger inlet pipe 8 and connecting pipe 16, enters the heat storage spiral coil in the tank, and exchanges heat with the phase change heat medium 22. After heat exchange, the medium flows back to the heat exchanger inlet pipe 8 from the first energy storage tank outlet pipe 13. The insulation layer 21 reduces heat dissipation from the tank, and the heat release circuit solenoid valve 9 remains closed. The system synchronously performs cascade heat exchange and heat storage in parallel, storing excess heat and avoiding heat loss from the cooling tower.

[0064] S4. When the sensor data determines that the waste heat supply is insufficient or the heating load is at its peak, the solenoid valve 9 of the heat storage circuit is closed and the solenoid valve 9 of the heat release circuit is opened. After the medium in the user's heating return pipe 14 is balanced by the second buffer tank 5, it enters the heat release spiral coil along the connecting pipe 16 and the inlet pipe 19 of the second energy storage tank, absorbs the phase change heat medium 22 to store heat, and the heated return water flows out through the outlet pipe 20 of the second energy storage tank and flows into the plate heat exchanger 2 to complete the heating, make up for the heat source gap, and stabilize the water supply temperature of the user's heating inlet pipe 15.

[0065] Temperature sensors 11 are installed on S5, heat exchanger inlet pipe 8, user heating return pipe 14, user heating inlet pipe 15, and aquaculture circulation inlet pipe 18. Water flow sensors 10 are installed on the bypass return pipe 7 and heat exchanger inlet pipe 8 to collect data around the clock. The control system compares the heat generation and heat consumption loads and automatically adjusts the branch control components and solenoid valves 9. It switches between three operating conditions—pure heat exchange, parallel heat storage, and parallel heat release—without manual intervention, realizing the system's adaptive fully automatic operation.

[0066] Waste heat from the thermal power plant is sent to the first buffer tank 1 via the main circulating water pipe 6. The pressure and flow are stabilized by the bypass return pipe 7, the heat exchanger inlet pipe 8, the supporting branch control components, the water flow sensor 10, and the temperature sensor 11. The medium undergoes two-stage heat exchange through the plate heat exchanger 2 and the column heat exchanger 3, and is supplied to the user heating inlet pipe 15 and the aquaculture circulating inlet pipe 18 respectively. The heat exchanged cold water is returned to the cooling tower via the drain pipe 23.

[0067] The phase change energy storage tank 4 has a built-in insulation layer 21 and a phase change heat transfer medium 22. It forms a heat storage circuit through the first energy storage tank inlet pipe 12 and the first energy storage tank outlet pipe 13, and forms a heat release circuit through the second energy storage tank inlet pipe 19 and the second energy storage tank outlet pipe 20. The two circuits are independently equipped with electromagnetic valves 9. The user heating return pipe 14 is equipped with a second buffer tank 5 to balance the return water. All pipelines are spliced ​​through connecting pipes 16. Temperature sensors 11 and water flow sensors 10 are deployed throughout the area for real-time monitoring. The system automatically switches between heat storage and heat release modes according to the load, solving problems such as single heat exchange, unstable heating, water circuit impact, waste heat, and thermal pollution of traditional equipment. It is suitable for energy-saving retrofits of various thermal power plants.

[0068] 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 dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system, characterized in that, include: The circulating water buffer diversion tank has an inlet, a first outlet branch and a second outlet branch. The inlet is connected to the main circulating water pipe of the power plant, the first outlet branch is connected to the bypass pipeline of the circulating water side of the power plant, and the second outlet branch is connected to the cascade heat exchange assembly and forms a heat exchange water supply branch. The cascade heat exchange assembly includes a plate heat exchanger and a column heat exchanger. The plate heat exchanger has a hot-side channel and a cold-side channel. The hot-side channel is connected to the heat exchange water supply branch. The inlet of the cold-side channel is connected to the heating return water pipe, and the outlet of the cold-side channel leads out to the heating water supply pipe. The outlet of the hot-side channel is connected to the inlet of the hot-side channel of the column heat exchanger. The inlet of the cold-side channel of the column heat exchanger is connected to the aquaculture return water pipe, and the outlet of the cold-side channel leads out to the aquaculture water supply pipe. The phase change energy storage tank has an insulation layer fixedly laid on its inner wall, and two sets of mutually isolated spiral coils are arranged in the inner cavity of the tank. The two ends of one set of spiral coils are respectively connected to the heat exchange water supply branch to form a heat storage parallel circuit, and the two ends of the other set of spiral coils are respectively connected to the heating return water pipe to form a heat release parallel circuit.

2. The dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system according to claim 1, characterized in that, The power plant circulating water bypass pipeline and the heat exchange water supply branch are equipped with branch control components. The branch control components are used to adjust the medium flow rate of the two outlet branches to stabilize the circulating water temperature flowing into the cascade heat exchange assembly.

3. The dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system according to claim 1, characterized in that, The heating return water pipe is equipped with a second buffer tank. The two ends of the second buffer tank are respectively connected to the inlet of the cold side channel of the plate heat exchanger and the heat release parallel circuit, which is used to balance the flow rate and temperature of the heating return water.

4. The dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system according to claim 1, characterized in that, The insulation layer is made of aluminum silicate fiber cotton. The phase change energy storage tank is filled with a paraffin-based phase change heat transfer medium, and two sets of spiral coils are immersed in the paraffin-based phase change heat transfer medium.

5. The dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system according to claim 1, characterized in that, Both the thermal storage parallel circuit and the thermal release parallel circuit are equipped with on / off valves; The on / off valve of the heat storage parallel circuit is located in the connecting pipe section between the heat exchange water supply branch and one of the spiral coils, while the on / off valve of the heat release parallel circuit is located in the connecting pipe section between the heating return water pipe and another spiral coil.

6. The dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system according to claim 1, characterized in that, Temperature sensors are installed on the heat exchange water supply branch, heating return water pipe, heating water supply pipe, and aquaculture water supply pipe.

7. The dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system according to claim 2, characterized in that, The branch control component includes a water flow sensor, which is used to collect the medium flow rate of the pipeline.

8. The dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system according to claim 1, characterized in that, Two sets of spiral coils are arranged along the axial direction of the phase change energy storage tank, and the spiral coils are of equidistant spiral structure.

9. The dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system according to claim 1, characterized in that, The hot-side channel outlet of the column heat exchanger is connected to a drainage pipe, which is used to transport the power plant circulating water that has completed two-stage heat exchange to the power plant cooling tower.

10. A method for utilizing the waste heat of circulating water in a dual-coil phase change energy storage power plant, applied to the dual-coil phase change energy storage power plant circulating water cascade waste heat utilization system according to any one of claims 1 to 9, characterized in that, include: S1. The circulating water inside the main circulating water pipe of the power plant is fed into the tank through the inlet of the circulating water buffer distribution tank. The flow rate of the two branches is distributed by the branch control components on the power plant circulating water side bypass pipe and the heat exchange water supply branch, and the circulating water temperature delivered to the cascade heat exchange assembly is stabilized. S2. Circulating water enters the hot side channel of the plate heat exchanger through the heat exchange water supply branch. The heating return water in the cold side channel of the plate heat exchanger absorbs heat and is heated up before being supplied externally by the heating water supply pipe. The circulating water then flows into the hot side channel of the column heat exchanger for secondary heat exchange. The aquaculture return water in the cold side channel of the column heat exchanger absorbs heat and is heated up before being output by the aquaculture water supply pipe. After the heat exchange is completed, the circulating water is transported to the power plant cooling tower along the drainage pipeline. S3. When the power plant has surplus waste heat and the heating load is low, open the on / off valve of the heat storage parallel circuit, and high-temperature circulating water enters a set of spiral coils in the phase change energy storage tank to exchange heat with the paraffin-based phase change heat transfer medium in the tank to store heat. S4. When the heating load is at its peak and the power plant's circulating water waste heat supply is insufficient, close the heat storage parallel circuit on / off valve and open the heat release parallel circuit on / off valve. The heating return water flows through another set of spiral coils and relies on the phase change medium to store heat to heat the heating return water. S5, temperature sensors on the heat exchange water supply branch, heating return water pipe, heating water supply pipe, and aquaculture water supply pipe, together with the water flow sensor in the branch control component, collect medium temperature and flow data in real time, and link each on / off valve to automatically switch the cascade heat exchange, heat storage, and heat release operation modes.

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