A zero-carbon waste heat recovery system and method for a direct air-cooled unit

Abstract

The application discloses a zero-carbon waste heat recovery system and method for a direct air-cooling unit, which comprises an air cooling island, a chemical water supplement pipeline, an air source heat pump, a photovoltaic power generation system, an energy storage system and a control unit. Dry hot air with a temperature of 20-50 DEG C discharged by the air cooling island is used as a low-temperature heat source, and the air source heat pump uses the waste heat to heat the chemical water supplement to 35-45 DEG C and then sends the chemical water supplement into a condenser or a hot well. The photovoltaic power generation system is installed on the windbreak wall around the air cooling island and is matched with the energy storage system to provide zero-carbon power for the air source heat pump. The control unit is in communication connection with a power plant DCS system. The application realizes zero-carbon emission of the water supplement heating link, effectively recovers the waste heat of the air cooling island, reduces coal consumption and power consumption of the unit, improves operation efficiency, has low modification difficulty and high safety, and is suitable for energy-saving modification of the direct air-cooling unit in the northwest region.

Description

Technical Field

[0001] This invention relates to a zero-carbon waste heat recovery system and method for direct air-cooled units, belonging to the field of waste heat recovery and utilization technology in thermal power plants. Background Technology

[0002] Direct air-cooled units are widely distributed in the water-scarce northwest regions of my country. Exhaust steam from the turbine's low-pressure cylinder enters the air-cooled island through exhaust pipes. Driven by a large-diameter axial fan, outside cold air passes through the fin gaps of the finned tube bundle, condensing the steam inside into condensate. The hot air is then discharged openly into the atmosphere. Windbreak walls are installed around the air-cooled island to prevent hot air backflow.

[0003] During normal operation, the outlet air temperature of the air-cooled island remains stable at 20℃-50℃, and the air humidity decreases after being heated by the heat exchange tube bundle. Currently, the waste heat of this dry air is directly discharged without effective utilization, resulting in significant energy waste. On the other hand, the chemical makeup water temperature of the condenser / hot well is typically 15℃-30℃ (lower in winter), requiring heating to the optimal makeup water temperature of 35℃-45℃ by consuming turbine extraction steam or auxiliary steam sources. This significantly increases unit energy consumption and reduces overall operating efficiency.

[0004] In addition, conventional air-cooled island windbreaks are made of 11-13 meter high color steel plates arranged vertically around the platform, which only serve to block the wind and are not effectively utilized, resulting in a waste of space resources.

[0005] In response to the "dual carbon" goals and the requirements for green power plant construction, there is an urgent need for a technical solution that can fully utilize the waste heat of the air-cooled island, reduce fossil energy consumption, and achieve zero-carbon water replenishment heating. Although there are attempts to use heat pumps to recover waste heat in existing technologies, they generally suffer from problems such as reliance on plant power for driving energy, inability to achieve zero-carbon operation, low integration with the original unit system, and insufficient safety redundancy. Summary of the Invention

[0006] This invention addresses the shortcomings of existing direct air-cooled units, such as direct discharge of waste heat from the air-cooled island, high energy consumption due to reliance on steam extraction for chemical makeup water heating, and waste of space resources in the windbreak wall. It provides a zero-carbon waste heat recovery system and method for direct air-cooled units, utilizing the 20℃-50℃ dry hot air discharged from the air-cooled island as a low-grade heat source. Combined with photovoltaic power generation and energy storage systems to drive an air source heat pump, the chemical makeup water is heated to the optimal temperature, achieving zero carbon emissions in the makeup water heating process and improving the unit's operating efficiency.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a zero-carbon waste heat recovery system for a direct air-cooled unit, comprising an air-cooled island, wherein the air-cooled island has an exhaust pipe, a finned tube bundle, and a dry hot air outlet. Exhaust steam from the low-pressure cylinder of the steam turbine enters the finned tube bundle through the exhaust pipe. Outside cold air passes through the finned tube bundle, condensing the steam into condensate to form dry hot air at 20℃-50℃, which is then discharged from the dry hot air outlet. The system further includes: A chemical water supply pipeline, one end of which is connected to a chemical water supply source, and the other end of which is connected to the water supply inlet of the condenser or hot well; An air source heat pump is provided with an air inlet, a water-side inlet, and a water-side outlet. The air inlet is connected to the dry hot air outlet of the air-cooled island, the water-side inlet is connected to the chemical makeup water pipeline, and the water-side outlet is connected to the makeup water inlet of the condenser or hot well. It is used to heat the chemical makeup water to 35°C-45°C using the waste heat of the dry hot air. A photovoltaic power generation system is installed on the windbreak walls around the air-cooled island, replacing the original windbreak walls, and is used to convert solar energy into electrical energy. An energy storage system, which is electrically connected to the photovoltaic power generation system, is used to store excess electrical energy from the photovoltaic power generation system. The power output terminals of the photovoltaic power generation system and the energy storage system are respectively electrically connected to the power supply terminal of the air source heat pump to provide power to the air source heat pump.

[0008] Furthermore, the height of the windbreak wall is 11-13m, and the photovoltaic modules of the photovoltaic power generation system are arranged along the vertical direction of the windbreak wall, with their area adapted to the perimeter of the air-cooled island.

[0009] Furthermore, the chemical makeup water pipeline is provided with a heat pump access branch near the inlet of the condenser or hot well. A branch valve, a pressure gauge and a thermometer are installed in sequence on the heat pump access branch. The inlet and outlet of the heat pump access branch are respectively connected to the chemical makeup water pipeline. The water-side inlet and water-side outlet of the air source heat pump are connected in series in the heat pump access branch.

[0010] Furthermore, it also includes a control unit, which is electrically connected to the photovoltaic power generation system, the energy storage system, the air source heat pump, and the temperature sensor and flow sensor installed on the chemical water supply pipeline. The control unit can collect photovoltaic output, air temperature, water supply flow and inlet and outlet temperatures in real time, and automatically adjust the operating load of the air source heat pump to stabilize the water supply outlet temperature at 40°C.

[0011] Furthermore, the control unit is also connected to the power plant's DCS system for communication and coordinated control, used to monitor the operating status and parameter changes of each device in real time, and realize automatic start-up and shutdown, load regulation and fault alarm.

[0012] Furthermore, the air source heat pump adopts two heat pump units connected in parallel, one for use and one for standby, and is connected in parallel with the original steam extraction heating system of the unit. The power output terminals of the photovoltaic power generation system and the energy storage system are also connected to the plant power backup power supply branch, which is used to switch to plant power supply or the original steam extraction heating process when the photovoltaic output is insufficient or the heat pump fails.

[0013] Furthermore, the air-side heat exchanger of the air source heat pump is equipped with a dustproof device, and its water-side heat exchange pipeline is made of corrosion-resistant material; the photovoltaic modules of the photovoltaic power generation system are wind- and sand-resistant modules.

[0014] Furthermore, the capacity of the energy storage system is set to at least meet the power requirements for driving the air source heat pump to operate throughout the day at night or during periods of insufficient sunlight. The heating capacity of the air source heat pump is ≥1000kW, and the input power is ≤250kW. The installed capacity of the photovoltaic power generation system is sufficient to fully drive the air source heat pump during the day and simultaneously charge the energy storage system.

[0015] A method for zero-carbon waste heat recovery in a direct air-cooled unit includes the following steps: Step S1: Use the 20℃-50℃ dry hot air discharged from the air-cooled island as a low-grade heat source, and recover the remaining heat through an air source heat pump; Step S2: Introduce the chemical makeup water of the unit into the air source heat pump, and use the recovered waste heat to heat the chemical makeup water to 35℃-45℃ before sending it into the condenser or hot well; Step S3: Install a photovoltaic power generation system at the windbreak wall around the air-cooled island, and connect the photovoltaic power generation system with the energy storage system. Use photovoltaic power and energy storage power to supply the air source heat pump, so as to achieve zero carbon emissions in the water replenishment and heating process.

[0016] Furthermore, it also includes step S4: when the photovoltaic output is insufficient, it automatically switches to the plant power supply to supplement the power supply; when the air source heat pump fails, it automatically switches to the original steam extraction heating process to ensure the continuity of water replenishment heating.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: This invention adopts a "photovoltaic drive + waste heat recovery" model. Photovoltaic power is a clean and renewable energy source, and the heat pump recovers the waste heat of the dry air in the air-cooled island to replace the traditional steam extraction heating, achieving zero carbon emissions in the water replenishment heating process and helping power plants achieve their dual carbon targets.

[0018] This invention fully recovers waste heat from dry air at 20℃-50℃, with a heat pump COP≥3.5, and can recover a large amount of low-grade waste heat with a small amount of electricity consumption; photovoltaic drive further reduces plant power consumption, resulting in significant dual energy-saving benefits.

[0019] The heat pump of this invention is perfectly matched to the waste heat characteristics of direct air-cooled units in Northwest China, with high matching degree of chemical water makeup temperature and no impact on the main process of the steam-water system; the photovoltaic system is adapted to the abundant sunshine in Northwest China and has strong power generation stability.

[0020] This invention utilizes auxiliary pipeline modifications without altering the main equipment and main pipelines; the photovoltaic system is deployed using windbreak walls, resulting in a short construction period; and it is equipped with redundant design and DCS linkage control, ensuring safe and reliable operation.

[0021] This invention reduces the amount of steam extracted from the turbine, increases the effective output power, optimizes the makeup water temperature, and reduces the heating load of the deaerator. It is expected that the overall operating efficiency of the unit will be improved by 0.3%~0.5%, and the coal consumption will be reduced by 0.5-1g / kWh. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the zero-carbon waste heat recovery system for direct air-cooled units according to the present invention; Figure 2 This is a flowchart illustrating the zero-carbon heating energy-saving process of the present invention. Figure 3 This is a detailed piping layout diagram for the chemical water replenishment and heating system of this invention; Figure 4 This is the control logic diagram for the present invention.

[0023] Attached reference numerals: 1-Air-cooled island, 11-Exhaust pipe, 12-Finned tube bundle, 13-Dry hot air outlet, 2-Chemical water supply pipe, 3-Air source heat pump, 31-Air inlet, 32-Water side inlet, 33-Water side outlet, 4-Photovoltaic power generation system, 5-Energy storage system, 6-Condenser / Heat well, 7-Windbreak wall, 8-Heat pump access branch, 81-Branch valve, 82-Pressure gauge, 83-Thermometer, 9-Control unit, 10-Power plant DCS system.

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Detailed Implementation

[0025] Embodiment 1 of the present invention: Embodiment 1 of the present invention: A zero-carbon waste heat recovery system for a direct air-cooled unit, comprising an air-cooled island 1, wherein the air-cooled island 1 has an exhaust pipe 11, a finned tube bundle 12 and a dry hot air outlet 13. Exhaust steam from the low-pressure cylinder of the steam turbine enters the finned tube bundle 12 through the exhaust pipe 11. Outside cold air passes through the finned tube bundle 12, condenses the steam into condensate, and forms dry hot air at 20°C-50°C, which is then discharged from the dry hot air outlet 13.

[0026] This system also includes: Chemical water supply pipeline 2, one end of which is connected to a chemical water supply source, and the other end is connected to the water supply inlet of the condenser or hot well 6; An air source heat pump 3 is provided with an air inlet 31, a water-side inlet 32, and a water-side outlet 33. The air inlet 31 is connected to the dry hot air outlet 13 of the air-cooled island 1, the water-side inlet 32 ​​is connected to the chemical makeup water pipeline 2, and the water-side outlet 33 is connected to the makeup water inlet of the condenser or hot well 6. It is used to heat the chemical makeup water to 35℃-45℃ using the waste heat of the dry hot air. A photovoltaic power generation system 4 is installed on the windbreak wall 7 around the air-cooled island 1, replacing the original windbreak wall, and is used to convert solar energy into electrical energy. Energy storage system 5, which is electrically connected to photovoltaic power generation system 4, is used to store excess electrical energy of photovoltaic power generation system 4; The control unit 9 is electrically connected to the photovoltaic power generation system 4, the energy storage system 5, the air source heat pump 3, and the temperature and flow sensors installed on the chemical water supply pipeline 2. The control unit 9 can collect photovoltaic output, air temperature, water supply flow rate, and inlet and outlet temperatures in real time, and automatically adjust the operating load of the air source heat pump 3 to stabilize the water supply outlet temperature at 40℃. The control unit 9 is also connected to the power plant's DCS system 10 for communication and linkage control, used to monitor the operating status and parameter changes of each device in real time, and realize automatic start-up and shutdown, load adjustment, and fault alarm. The power output terminals of the photovoltaic power generation system 4 and the energy storage system 5 are respectively electrically connected to the power supply terminal of the air source heat pump 3 to provide power to the air source heat pump 3.

[0027] Specifically, the windbreak wall 7 has a height of 11-13m, and the photovoltaic modules of the photovoltaic power generation system 4 are arranged along the vertical direction of the windbreak wall 7, with their area matching the perimeter of the air-cooled island 1.

[0028] Specifically, the chemical water supply pipeline 2 is provided with a heat pump access branch 8 near the inlet of the condenser or hot well 6. A branch valve 81, a pressure gauge 82 and a thermometer 83 are installed in sequence on the heat pump access branch 8. The inlet and outlet of the heat pump access branch 8 are respectively connected to the chemical water supply pipeline 2. The water-side inlet 32 ​​and water-side outlet 33 of the air source heat pump 3 are connected in series in the heat pump access branch 8.

[0029] Specifically, the air source heat pump 3 is configured with two heat pump units connected in parallel, one for use and one for standby, and is connected in parallel with the original steam extraction heating system of the unit. The power output terminals of the photovoltaic power generation system 4 and the energy storage system 5 are also connected to the plant power backup power supply branch, which is used to switch to plant power supply or the original steam extraction heating process when the photovoltaic output is insufficient or the heat pump fails.

[0030] Specifically, the air-side heat exchanger of the air source heat pump 3 is equipped with a dustproof device, and its water-side heat exchange pipeline is made of corrosion-resistant material; the photovoltaic modules of the photovoltaic power generation system 4 are wind and sand resistant modules.

[0031] Specifically, the capacity of the energy storage system 5 is set to at least meet the power requirements for driving the air source heat pump 3 to operate throughout the day at night or during periods of insufficient sunlight. The heating capacity of the air source heat pump 3 is ≥1000kW, and the input power is ≤250kW. The installed capacity of the photovoltaic power generation system 4 is sufficient to fully drive the air source heat pump 3 during the day and simultaneously charge the energy storage system 5.

[0032] Embodiment 2 of the present invention: This embodiment provides a method for zero-carbon waste heat recovery in a direct air-cooled unit, implemented using the system described in Embodiment 1, and includes the following steps: Step S1: The 20℃-50℃ dry hot air discharged from the air-cooled island 1 is used as a low-temperature heat source, and the residual heat is recovered through the air source heat pump 3. Specifically, the dry hot air enters the air inlet 31 of the air source heat pump 3 from the dry hot air outlet 13 through the air duct, and is discharged after releasing heat in the heat pump evaporator at a lower temperature.

[0033] Step S2: The chemical makeup water of the unit is introduced into the air source heat pump 3. The recovered waste heat is used to heat the chemical makeup water to 35℃-45℃ before it is sent into the condenser / heat well 6. The chemical makeup water enters the heat pump access branch 8 through the chemical makeup water pipeline 2, enters the heat pump condenser from the water side inlet 32 ​​to absorb heat, and after being heated, it flows out from the water side outlet 33, merges into the original makeup water pipeline through the branch, and finally enters the condenser / heat well 6.

[0034] Step S3: Install a photovoltaic power generation system 4 around the windbreak walls of the air-cooled island 1, and connect the photovoltaic power generation system 4 to the energy storage system 5. Use photovoltaic power and stored energy to power the air source heat pump 3, achieving zero carbon emissions in the water replenishment and heating process. During the day, the photovoltaic power generation system 4 directly drives the heat pump, and excess electricity is stored in the energy storage system 5; at night or when there is insufficient sunlight, the energy storage system 5 discharges to drive the heat pump.

[0035] Step S4: When the photovoltaic output is insufficient (such as during consecutive cloudy days), the control unit 9 automatically switches to the plant power supply for supplementary power; when the air source heat pump 3 fails, the control unit 9 automatically switches to the original steam extraction heating process to ensure the continuity of water replenishment heating.

[0036] Embodiment 3 of the present invention: This embodiment provides a zero-carbon waste heat recovery system for a direct air-cooled unit, which is applied to a 600MW direct air-cooled unit.

[0037] like Figure 1 As shown, the system includes an air-cooled island 1. The air-cooled island 1 has an exhaust pipe 11, a finned tube bundle 12, and a dry hot air outlet 13. The exhaust steam from the low-pressure cylinder of the steam turbine enters the finned tube bundle 12 through the exhaust pipe 11. Driven by a large-diameter axial flow fan, outside cold air passes through the fin gaps of the finned tube bundle 12, condensing the steam into condensate. After heat exchange, it forms dry hot air at 20℃-50℃, which is discharged from the dry hot air outlet 13.

[0038] The system also includes a chemical makeup water pipeline 2, one end of which is connected to the chemical makeup water source and the other end is connected to the makeup water inlet of the condenser / hot well 6.

[0039] The air source heat pump 3 is equipped with an air inlet 31, a water-side inlet 32, and a water-side outlet 33. The air inlet 31 is connected to the dry hot air outlet 13 of the air-cooled island 1 via a duct, the water-side inlet 32 ​​is connected to the chemical makeup water pipeline 2, and the water-side outlet 33 is connected to the makeup water inlet of the condenser / heat well 6. The air source heat pump 3 utilizes the waste heat of the dry hot air to heat the chemical makeup water to 35℃-45℃.

[0040] The photovoltaic power generation system 4 is installed around the windbreak walls of the air-cooled island 1, replacing the original corrugated steel windbreak walls. The windbreak walls 7 are 12m high, and the photovoltaic modules are arranged vertically along the windbreak walls. The perimeter of the air-cooled island is approximately 290m, and the photovoltaic installation area is approximately 4350㎡.

[0041] Energy storage system 5 is electrically connected to photovoltaic power generation system 4 to store excess electrical energy during the day. The power output terminals of photovoltaic power generation system 4 and energy storage system 5 are respectively electrically connected to the power supply terminal of air source heat pump 3.

[0042] like Figure 3 As shown, a heat pump access branch 8 is installed on the chemical makeup water pipeline 2 near the inlet of the condenser / heat well 6. A branch valve 81, a pressure gauge 82, and a thermometer 83 are installed sequentially on the heat pump access branch 8. The inlet and outlet of the heat pump access branch 8 are connected to the chemical makeup water pipeline 2, respectively. The water-side inlet 32 ​​and water-side outlet 33 of the air source heat pump 3 are connected in series in the heat pump access branch 8. This setup does not alter the original main pipeline, resulting in minimal modification work.

[0043] The system also includes control unit 9, (see Figure 4The control unit 9 is electrically connected to the photovoltaic power generation system 4, the energy storage system 5, the air source heat pump 3, and the temperature and flow sensors installed on the chemical water supply pipeline 2. The control unit 9 collects real-time data on photovoltaic output, air temperature, water supply flow rate, and inlet and outlet temperatures, and automatically adjusts the operating load of the air source heat pump 3 to stabilize the water supply outlet temperature at 40℃.

[0044] The control unit 9 is also connected to the power plant's DCS system 10 for coordinated control, real-time monitoring of the operating status and parameter changes of each device, and automatic start-up and shutdown, load regulation and fault alarm.

[0045] The air source heat pump 3 employs two heat pump units connected in parallel, one for operation and one for standby, and is also connected in parallel with the unit's existing steam extraction heating system. The power output terminals of the photovoltaic power generation system 4 and the energy storage system 5 are also connected to a backup power supply branch for the plant. When the photovoltaic output is insufficient, it automatically switches to the plant power supply to supplement the power; when the heat pump fails, it quickly switches back to the original steam extraction heating process to ensure the normal operation of the unit.

[0046] In response to the characteristics of strong winds and sandstorms and high water hardness in Northwest China, the air-side heat exchanger of the air source heat pump 3 is equipped with a dustproof device (such as a removable filter), and the water-side heat exchange pipeline is made of stainless steel or copper alloy corrosion-resistant material. The photovoltaic modules of the photovoltaic power generation system 4 are selected to be wind and sand resistant (with tempered glass surface and dustproof coating).

[0047] In this embodiment, the unit's normal operating water supply is 50 m³ / h, with an initial water temperature of 25℃ and a target temperature of 40℃, resulting in a temperature difference Δt = 15℃. The required heating capacity is Q = G × c × Δt = 50000 × 4.2 × 15 = 3150000 kJ / h = 875 kW. Considering a 10% margin, we take 963 kW, but the actual selected capacity is ≥1000 kW. The air source heat pump inlet air comes from the air-cooled island, which has a dry, hot air temperature of 20-55℃. The rated operating COP is ≥4.0, and the input power is P = 1000 ÷ 4.0 = 250 kW. The total daily power consumption is 250 × 24 = 6000 kWh.

[0048] The photovoltaic system covers an area of ​​4350㎡. Assuming an average of 8 hours of sunshine per day in Northwest China, and an average photovoltaic output of 0.2kW / ㎡, the daily power generation is 4350 × 0.2 × 8 = 6960kWh, sufficient to meet the heat pump's daily power needs. An energy storage system with a capacity of 4500kWh / day is configured for nighttime and rainy days.

[0049] The zero-carbon waste heat recovery system and method for direct air-cooled power units provided by this invention can be widely applied to energy-saving retrofits and new construction projects of direct air-cooled power units in thermal power plants, and is especially suitable for areas in Northwest China with abundant sunshine, scarce water resources, and a high concentration of air-cooled power units. This system fully utilizes existing waste heat resources and combines them with photovoltaic green electricity to drive a heat pump, achieving zero-carbon water replenishment and heating. It has significant economic, environmental, and social benefits, and meets the requirements of "dual-carbon" goals and green power plant construction.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A zero-carbon waste heat recovery system for a direct air-cooled unit, comprising an air-cooled island, the air-cooled island having an exhaust pipe, a finned tube bundle, and a dry hot air outlet, wherein exhaust steam from the low-pressure cylinder of the steam turbine enters the finned tube bundle through the exhaust pipe, and outside cold air passes through the finned tube bundle, condensing the steam into condensate to form dry hot air at 20°C-50°C, which is then discharged from the dry hot air outlet, characterized in that... Also includes: A chemical water supply pipeline, one end of which is connected to a chemical water supply source, and the other end of which is connected to the water supply inlet of the condenser or hot well; An air source heat pump is provided with an air inlet, a water-side inlet, and a water-side outlet. The air inlet is connected to the dry hot air outlet of the air-cooled island, the water-side inlet is connected to the chemical makeup water pipeline, and the water-side outlet is connected to the makeup water inlet of the condenser or hot well. It is used to heat the chemical makeup water to 35°C-45°C using the waste heat of the dry hot air. A photovoltaic power generation system is installed on the windbreak walls around the air-cooled island, replacing the original windbreak walls, and is used to convert solar energy into electrical energy. An energy storage system, which is electrically connected to the photovoltaic power generation system, is used to store excess electrical energy from the photovoltaic power generation system. The power output terminals of the photovoltaic power generation system and the energy storage system are respectively electrically connected to the power supply terminal of the air source heat pump to provide power to the air source heat pump.

2. The zero-carbon waste heat recovery system for direct air-cooled units according to claim 1, characterized in that, The height of the windbreak wall is 11-13m, and the photovoltaic modules of the photovoltaic power generation system are arranged along the vertical direction of the windbreak wall, with their area matching the perimeter of the air-cooled island.

3. The zero-carbon waste heat recovery system for direct air-cooled units according to claim 1, characterized in that, The chemical water supply pipeline has a heat pump access branch at the inlet near the condenser or hot well. A branch valve, pressure gauge and thermometer are installed in sequence on the heat pump access branch. The inlet and outlet of the heat pump access branch are connected to the chemical water supply pipeline. The water-side inlet and water-side outlet of the air source heat pump are connected in series in the heat pump access branch.

4. The zero-carbon waste heat recovery system for direct air-cooled units according to claim 1, characterized in that, It also includes a control unit, which is electrically connected to the photovoltaic power generation system, the energy storage system, the air source heat pump, and the temperature sensor and flow sensor installed on the chemical water supply pipeline. The control unit can collect photovoltaic output, air temperature, water supply flow and inlet and outlet temperatures in real time, and automatically adjust the operating load of the air source heat pump to keep the water supply outlet temperature stable at 40°C.

5. The zero-carbon waste heat recovery system for direct air-cooled units according to claim 4, characterized in that, The control unit is also connected to the power plant's DCS system for coordinated control, used to monitor the operating status and parameter changes of each device in real time, and to realize automatic start-up and shutdown, load regulation and fault alarm.

6. The zero-carbon waste heat recovery system for direct air-cooled units according to claim 1, characterized in that, The air source heat pump is configured with two heat pump units connected in parallel, one for operation and one for standby, and is connected in parallel with the original steam extraction heating system of the unit. The power output terminals of the photovoltaic power generation system and the energy storage system are also connected to the plant power backup power supply branch, which is used to switch to plant power supply or the original steam extraction heating process when the photovoltaic output is insufficient or the heat pump fails.

7. The zero-carbon waste heat recovery system for direct air-cooled units according to claim 1, characterized in that, The air-side heat exchanger of the air source heat pump is equipped with a dustproof device, and its water-side heat exchange pipeline is made of corrosion-resistant material; the photovoltaic modules of the photovoltaic power generation system are wind and sand resistant modules.

8. The zero-carbon waste heat recovery system for direct air-cooled units according to claim 1, characterized in that, The capacity of the energy storage system is set to at least meet the power requirements for driving the air source heat pump to operate throughout the day at night or during periods of insufficient sunlight. The heating capacity of the air source heat pump is ≥1000kW, and the input power is ≤250kW. The installed capacity of the photovoltaic power generation system is sufficient to fully drive the air source heat pump during the day and simultaneously charge the energy storage system.

9. A method for zero-carbon waste heat recovery in a direct air-cooled unit, characterized in that, Includes the following steps: Step S1: Use the 20℃-50℃ dry hot air discharged from the air-cooled island as a low-grade heat source, and recover the remaining heat through an air source heat pump; Step S2: Introduce the chemical makeup water of the unit into the air source heat pump, and use the recovered waste heat to heat the chemical makeup water to 35℃-45℃ before sending it into the condenser or hot well; Step S3: Install a photovoltaic power generation system at the windbreak wall around the air-cooled island, and connect the photovoltaic power generation system with the energy storage system. Use photovoltaic power and energy storage power to supply the air source heat pump, so as to achieve zero carbon emissions in the water replenishment and heating process.

10. The zero-carbon waste heat recovery method for direct air-cooled units according to claim 9, characterized in that, It also includes step S4: when the photovoltaic output is insufficient, it automatically switches to the plant power supply to supplement the power supply; when the air source heat pump fails, it automatically switches to the original steam extraction heating process to ensure the continuity of water replenishment heating.

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