A multi-source coupled cycle heat refrigeration back pressure reducing energy saving system for thermal power generation

Abstract

This application discloses a multi-source coupled circulating thermal cooling back pressure reduction energy-saving system for thermal power generation, including a steam turbine, a main exhaust steam pipeline, a condensing unit, a condensate tank, a condensate pump, a main exhaust steam bypass cooling pipeline, a chiller unit, a non-contact heat exchange device for flue gas waste heat, a thermal compensation device, a solar thermal device, and a heat source energy storage device. This application utilizes multiple heat sources—flue gas waste heat and solar thermal energy storage—to drive the chiller unit to produce chilled water at 15℃~20℃. This water is then used for non-contact active pre-cooling of the steam drawn from the bypass of the main exhaust steam pipeline. The cooled steam returns to the main exhaust steam pipeline and, after coupling, enters the condensing unit for condensation. This system can automatically start when the unit back pressure exceeds 13.5kPa, thereby reducing back pressure, coal consumption, and plant power consumption, improving unit operating efficiency and safety.

Description

Technical Field

[0001] This application relates to the field of energy conservation and consumption reduction technology in thermal power generation, specifically to a multi-source coupled cyclic thermal cooling back pressure reduction energy-saving system for thermal power generation. Background Technology

[0002] Direct air-cooled (ACC) and indirect air-cooled units are widely used in coal-fired power plants in water-scarce areas of northern my country due to their low water consumption. Under normal operating conditions, the air-cooled island relies on ambient air to condense and cool the turbine exhaust steam, thereby maintaining normal back pressure operation. However, due to ambient temperature constraints, during the high-temperature period in summer, especially between 10:00 and 20:00 on sunny days, the dry-bulb temperature of the air far exceeds the design temperature, significantly reducing the condensation efficiency of the air-cooled island. This leads to a sharp increase in turbine back pressure, with extreme values ​​reaching 35-40 kPa. The steam temperature in the main exhaust pipe can rise above 77°C, resulting in a decrease in unit output, a significant increase in coal consumption, and over-frequency operation of auxiliary equipment such as air-cooled fans and water pumps, significantly increasing plant power consumption and seriously affecting the unit's economy and safety.

[0003] To address the aforementioned issues, various technical solutions have emerged in the prior art to reduce back pressure during summer operation of air-cooled units. For example, Chinese patent CN113945031B discloses a direct air-cooled unit composite circulation system, which utilizes an ORC system to recover waste heat from the turbine and drive a closed-loop circulation to provide auxiliary cooling for the air-cooled island, achieving a certain degree of improvement in the high back pressure state of the unit. However, this solution fails to fully utilize the combined energy supply from multiple heat sources such as flue gas waste heat and solar energy, only utilizing the waste heat of the main exhaust steam itself, lacking technical means for active pre-cooling of bypass steam, resulting in limited cooling capacity and constrained back pressure reduction effect. Chinese patent CN222298549U discloses a peak cooling system for thermal power plants, which uses a combination of direct and indirect air-cooling devices to provide auxiliary cooling for specific radiators with cooling water, reducing system back pressure to a certain extent. However, this solution only provides water-cooled assistance on the radiator side, without pre-cooling the steam in the exhaust steam pipeline, and the cooling water source does not fully utilize waste heat energy, resulting in high system drive energy consumption. Chinese patent application CN108800652A discloses a summer safety device for air-cooled condensers in thermal power plants based on concentrated photovoltaic (CPV) waste heat utilization. This device uses PPV waste heat to drive a lithium bromide absorption chiller to provide chilled water spray cooling to the air-cooled island, effectively reducing the unit's high back pressure. However, this solution relies solely on PPV waste heat as a heat source, and PPV systems require a large area, are highly susceptible to environmental influences, and cannot provide continuous cooling during cloudy days or nighttime when sunlight is insufficient, resulting in instability in the system.

[0004] In summary, the existing technology has the following shortcomings: First, it uses a single heat source, resulting in poor cooling continuity and difficulty in maintaining stable operation during periods of high temperature throughout the day; second, it only provides auxiliary cooling for the air-cooled radiators, failing to fundamentally reduce the temperature and enthalpy of the steam entering the air-cooled island, thus limiting the reduction of the heat load on the air-cooled island; third, it lacks intelligent control between subsystems, resulting in low overall system energy utilization; and fourth, its energy-saving effect is limited, with insignificant reductions in unit back pressure and coal consumption.

[0005] Therefore, there is an urgent need for an energy-saving system that can comprehensively utilize multiple heat sources, actively pre-cool the exhaust steam, and achieve a significant reduction in unit back pressure. Summary of the Invention

[0006] This application provides a multi-source coupled cyclic thermal cooling back pressure reduction energy-saving system for thermal power generation, in order to solve the technical problems in the prior art where high summer temperatures lead to excessive back pressure in air-cooled units, low operating efficiency, and a significant increase in coal consumption and plant power consumption.

[0007] In a first aspect, this application provides a multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation, including: a steam turbine, a main exhaust steam pipeline, a condensing device, a condensate tank, a condensate pump, a main exhaust steam bypass cooling pipeline, a refrigeration unit, a non-contact heat exchange device for flue gas waste heat, a thermal compensation device, a solar thermal device, and a heat source energy storage device. The steam turbine is provided with an exhaust steam outlet; the main exhaust steam pipeline is provided with an inlet end and an outlet end; the condensation device is provided with a steam inlet and a condensate outlet; the condensate tank is provided with a water inlet, a water outlet, and a water return outlet; the condensate pump is provided with an inlet and an outlet. The exhaust outlet of the steam turbine is connected to the inlet end of the main exhaust steam pipe, and the outlet end of the main exhaust steam pipe is connected to the steam inlet of the condensing device; the condensate outlet of the condensing device is connected to the inlet of the condensate tank; and the outlet of the condensate tank is connected to the inlet of the condensate pump. The main exhaust steam bypass cooling pipe has an inlet end and an outlet end; the inlet end and outlet end of the main exhaust steam bypass cooling pipe are respectively bypassed to the main exhaust steam pipe, and the inlet end and outlet end of the main exhaust steam bypass cooling pipe are respectively equipped with bypass on / off valves; a heat exchanger is installed inside the main exhaust steam bypass cooling pipe; the heat exchanger has a cold water inlet and a cold water outlet; The refrigeration unit is equipped with a chilled water outlet, a chilled water return, a drive heat source inlet, a drive heat source outlet, a cooling water inlet, and a cooling water outlet. The chilled water outlet of the refrigeration unit is connected to the cold water inlet of the heat exchanger, and a first circulation pump is provided on the pipeline between the chilled water outlet and the cold water inlet; the cold water outlet of the heat exchanger is connected to the chilled water return port of the refrigeration unit, forming a chilled water circulation loop. The flue gas waste heat non-contact heat exchange device is provided with a water inlet and a water outlet; the heat energy compensation device is provided with a water inlet and a water outlet. The outlet of the condensate pump is connected to the inlet of the flue gas waste heat non-contact heat exchange device; the outlet of the flue gas waste heat non-contact heat exchange device is connected to the inlet of the heat energy compensation device; the outlet of the heat energy compensation device is connected to the inlet of the driving heat source of the refrigeration unit; the outlet of the driving heat source of the refrigeration unit is connected to the inlet of the flue gas waste heat non-contact heat exchange device, and a second circulation pump is provided on the pipeline between the outlet of the driving heat source and the inlet of the flue gas waste heat non-contact heat exchange device to form a driving heat source circulation loop. The outlet of the condensate tank is connected to the cooling water inlet of the refrigeration unit via a pipe. The cooling water outlet of the refrigeration unit is connected to the return water inlet of the condensate tank. A third circulation pump is provided between the cooling water outlet of the refrigeration unit and the return water inlet of the condensate tank to form a cooling water circulation loop. The photothermal device is provided with a heat energy output end; the heat source energy storage device is provided with an input end and an output end; the heat energy output end of the photothermal device is connected to the input end of the heat source energy storage device, and the heat source energy storage device stores the heat collected by the photothermal device.

[0008] Furthermore, the thermal energy compensation device is also provided with a heat replenishment input terminal, which is connected to the output terminal of the heat source energy storage device; when the heating outlet water temperature of the flue gas waste heat non-contact heat exchange device is lower than the first preset threshold, the thermal energy compensation device calls the heat storage energy in the heat source energy storage device to perform thermal energy compensation on the driving heat source circulation loop, ensuring the normal operation of the refrigeration unit.

[0009] Furthermore, the first preset threshold is 95°C; When the temperature of the heated water outlet of the flue gas waste heat non-contact heat exchange device is lower than the first preset threshold, the heat energy compensation device heats the hot water temperature in the driving heat source circulation loop to 100°C and replenishes the driving heat source circulation loop with heat energy.

[0010] Furthermore, the hot water heated to 100°C serves as a driving heat source to drive the refrigeration component to perform refrigeration work. After performing the work, the hot water is discharged from the outlet of the driving heat source of the refrigeration component at a temperature of 70°C to 80°C. The hot water at 70°C to 80°C is returned to the inlet of the flue gas waste heat non-contact heat exchange device for recycling.

[0011] Furthermore, the solar thermal device uses a solar concentrator to collect solar heat and store it in the heat source energy storage device.

[0012] Furthermore, temperature sensors and pressure sensors are installed at the steam inlet of the condensing device and on the main exhaust pipe of the waste steam; flow rate sensors and flow velocity sensors are installed on the outlet pipes of the first circulation pump, the second circulation pump and the third circulation pump.

[0013] Furthermore, the aforementioned multi-source coupled circulating heat and cooling back pressure reduction energy-saving system for thermal power generation also includes an intelligent linkage control system. The intelligent linkage control system is connected to the temperature and pressure sensors at the steam inlet of the condensing device, the temperature and pressure sensors on the main exhaust steam pipe, the flow and velocity sensors of each circulating pump, and the signals of each bypass opening and closing valve.

[0014] Furthermore, the intelligent linkage control system is configured as follows: (1) Based on the saturated steam temperature and pressure in the main exhaust steam pipe, adjust the flow rate and velocity of the circulating pump between the cooling water outlet and the cooling water inlet of the heat exchanger to regulate the amount of cooling water entering the main exhaust bypass cooling pipe, thereby controlling the steam temperature and back pressure in the main exhaust steam pipe. (2) With the preset target value of the driving heat source water temperature of the refrigeration unit reaching 100°C as the control target, the flow rate of the circulating pump in the driving heat source circulation loop and the heat compensation device are adjusted to balance the heating heat of the flue gas waste heat non-contact heat exchange device and the heat compensation heat of the heat source energy storage device, so as to maintain the stable hot water temperature at the inlet of the driving heat source.

[0015] Furthermore, the multi-source coupled circulating thermal cooling back pressure reduction energy-saving system for thermal power generation also includes: an open cooling tower, which is installed on the pipeline between the cooling water outlet of the refrigeration unit and the return water inlet of the condensate tank; when the cooling water outlet temperature of the refrigeration unit is higher than a second preset threshold, the cooling water is cooled by the open cooling tower and then returned to the return water inlet of the condensate tank.

[0016] Furthermore, the condensate tank provides an open cooling water circulation for the refrigeration unit. The cooling water is connected to the cooling water inlet of the refrigeration unit through a pipe from the outlet of the condensate tank. After completing the cooling work, the cooling water is returned to the return outlet of the condensate tank by a circulation pump. When the cooling water temperature is higher than the second preset threshold, an open cooling tower is introduced for cooling.

[0017] Furthermore, the second preset threshold is 32°C; when the cooling water outlet temperature of the refrigeration unit is higher than 32°C, the cooling water enters the open cooling tower to dissipate heat and cool down.

[0018] Furthermore, the main exhaust bypass cooling pipe can be one or more; When there are multiple main exhaust bypass cooling pipes, they are connected in parallel at the beginning and end of the main exhaust pipe; or, When there are multiple main exhaust bypass cooling pipes, the main exhaust bypass cooling pipes are installed on the branch pipes of the exhaust main exhaust pipe for local cooling and pressure reduction.

[0019] Furthermore, each of the main exhaust bypass cooling pipes is equipped with a heat exchanger.

[0020] Furthermore, the multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation is equipped with a start-up threshold. When the back pressure in the main exhaust steam pipe is higher than 13.5 kPa and the saturated steam temperature is higher than 50°C, the intelligent linkage control system issues a command to start the cooling components into operation.

[0021] Furthermore, the intelligent linkage control system adjusts the output power of the refrigeration unit in real time based on the monitored values ​​of steam temperature and pressure at the steam inlet of the condensing device, thereby controlling the flow rate and temperature of the cooling water and achieving regulation of the steam back pressure and temperature in the main exhaust steam pipe.

[0022] Furthermore, the condensation device can be any one of a direct air-cooling device, an indirect air-cooling device, a water-cooled tower, or a wet-cooled tower.

[0023] Furthermore, the non-contact heat exchange device for waste heat from flue gas adopts a non-contact heat exchange method, so that the condensate circulating water does not come into direct contact with the flue gas medium, thus avoiding pollution of the condensate water quality.

[0024] Furthermore, the refrigeration unit is one of a screw chiller, a lithium bromide chiller, or an air source heat pump chiller.

[0025] Furthermore, the chilled water produced by the refrigeration unit has a temperature of 15°C to 20°C; preferably, the chilled water produced by the refrigeration unit has a temperature of 18°C.

[0026] Furthermore, the steam bypassed from the main exhaust steam pipeline enters the main exhaust steam bypass cooling pipeline. After non-contact heat exchange and cooling with the chilled water produced by the refrigeration unit through the internal heat exchanger, it returns to the main exhaust steam pipeline and couples with the main steam flow for further cooling before entering the condensing device to complete condensation.

[0027] Secondly, this application provides an operation method for a multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation as described in the first aspect, comprising the following steps: (1) System startup The system is started manually or automatically when the back pressure reaches 13.5 kPa and the temperature exceeds 50°C, based on the steam temperature and back pressure at the steam inlet of the condensing device. The condensate formed by the condensing device enters the condensate tank and is pumped by the condensate pump to the flue gas waste heat non-contact heat exchange device for heating to 95℃~100℃. When the temperature of the heated water outlet is lower than 95℃, it is then heated to 100℃ by the heat energy compensation device and used as a driving heat source to enter the refrigeration unit to do work and produce chilled water at 15℃~20℃. After doing work, the 70℃~80℃ hot water discharged from the driving heat source outlet of the refrigeration unit is recycled back to the inlet of the flue gas waste heat non-contact heat exchange device for reheating and reuse. (2) Cooling water circulation The chilled water produced by the refrigeration unit at 15℃~20℃ is transported from the chilled water outlet of the refrigeration unit to the heat exchanger in the main exhaust bypass cooling pipe, where it performs non-contact heat exchange to cool and depressurize the steam in the main exhaust bypass cooling pipe. The cooled and depressurized steam returns to the exhaust main exhaust pipe to couple with the main steam flow for further cooling and depressurization, and then enters the condensing device to complete condensation. After the chilled water performs heat exchange and work on the steam, its temperature rises to 20℃~25℃, and it returns to the chilled water return port of the refrigeration unit through the cold water outlet of the heat exchanger, completing the chilled water circulation. (3) Cooling water circulation The condensate in the condensate tank enters the cooling water inlet of the refrigeration unit through the outlet of the condensate tank. After cooling the refrigeration unit, the cooling water returns to the return outlet of the condensate tank through the third circulation pump. (4) Intelligent linkage control The intelligent linkage control system monitors the inlet steam temperature and pressure of the condensing unit and the operating parameters of each key node in real time. Based on the changes in the unit's back pressure and saturated steam temperature, it automatically adjusts the output power of the refrigeration unit and the opening and closing degree of each circulating pump and control valve to achieve control of the back pressure and steam temperature in the main exhaust steam pipeline.

[0028] Furthermore, when the temperature of the cooling water in step (3) is higher than the second preset threshold, an open cooling tower is introduced to cool it down.

[0029] Furthermore, the operation method also includes a thermal energy compensation step. When the outlet water temperature of the flue gas waste heat non-contact heat exchange device is lower than a first preset threshold of 95°C, the thermal energy compensation device is automatically activated, and the thermal energy stored in the heat source energy storage device is used to perform thermal energy compensation on the driving heat source circulation loop.

[0030] Compared with the prior art, the technical solution provided in this application has the following beneficial effects: This application reduces the temperature of the steam entering the condenser before it enters the condenser, thereby significantly reducing the heat exchange load of the condenser. As a result, the auxiliary equipment such as the air-cooled fan and water pump of the condenser does not need to operate at overclock, the plant power consumption rate is significantly reduced, and the power consumption of auxiliary equipment is greatly reduced.

[0031] This application uses multiple heat sources, including waste heat from flue gas and solar thermal energy, to drive the refrigeration unit. When the temperature of the heat source driven by waste heat from flue gas is insufficient, it is automatically compensated by solar thermal energy storage, ensuring uninterrupted cooling capacity around the clock and effectively solving the problem that a single heat source cannot provide continuous cooling.

[0032] This application draws a portion of the steam from the main exhaust pipe and uses low-temperature chilled water produced by the refrigeration unit for non-contact heat exchange pre-cooling, which significantly reduces the temperature of the steam entering the condensing unit, thereby effectively reducing the back pressure of the unit and alleviating the problem of limited unit output during high-temperature periods in summer.

[0033] This application uses waste heat from flue gas to heat condensate. When the temperature after heating by waste heat from flue gas is below 95°C, the heat energy compensation device raises it to 100°C and drives the lithium bromide chiller unit. After doing work, the hot water temperature drops to 70°C to 80°C and is returned for recycling, realizing the cascaded and efficient utilization of heat energy. At the same time, it utilizes solar thermal energy storage to continuously store heat during non-working periods, significantly improving the overall energy utilization rate of the system.

[0034] The non-contact heat exchange device for waste heat from flue gas described in this application adopts a non-contact heat exchange method, in which the flue gas and condensate circulating water do not come into direct contact, effectively avoiding the pollution of condensate water quality by harmful components in the flue gas and ensuring the safe operation of the unit's water and steam system.

[0035] This application adopts a bypass cooling scheme, diverting a portion of the steam from the main exhaust pipe for pre-cooling, requiring no major modifications to the main system. Both the drive heat source circulation and the cooling water circulation are closed-loop systems, without introducing new media or altering the original steam-water system balance. The cooling water uses an open-loop circulation, fully utilizing the condensate in the condensate tank as the cooling medium, and an open cooling tower can be introduced to assist in heat dissipation when the temperature exceeds a second preset threshold of 32°C.

[0036] This application adopts an intelligent linkage control system that uses the inlet steam parameters of the condensing unit as a reference to adjust each component of the system in real time, thereby realizing the automated closed-loop control of the system and ensuring that the unit operates in a high-efficiency and safe state. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the overall structure of the multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation provided in the embodiments of this application.

[0039] The components include: 1. Condensation unit; 2. Condensate tank; 3. Condensate pump; 4. Flue gas waste heat non-contact heat exchanger; 5. Condensate polishing unit; 6. Low-pressure heater; 7. Deaerator; 8. Feed water pump; 9. High-pressure heater; 10. Boiler; 11. Super-reheater; 12. Steam turbine; 13. Exhaust steam main exhaust pipe; 14. Solar thermal unit; 15. Refrigeration unit; 16. Heat source energy storage device; 17. Thermal energy compensation device; 18. Generator; 19. First main exhaust steam bypass cooling pipe; 20. Second main exhaust steam bypass cooling pipe. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0041] See Figure 1 The multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation provided in this application consists of four parts: a driving heat source subsystem, a cooling power generation subsystem, a main exhaust steam bypass cooling subsystem, and an intelligent linkage control subsystem. Each subsystem operates in coordination with the others.

[0042] The core working principle of the multi-source coupled circulating heat and cooling back pressure reduction energy-saving system for thermal power generation is as follows: The waste heat from the flue gas at the tail end of the thermal power unit boiler is used as the main driving heat source, with solar thermal energy storage as a supplementary heat source. The driving heat source water is heated to 100℃ through the heat energy compensation device 17, driving the chiller unit 15 to produce chilled water at 15-20℃. The produced chilled water is sent through a closed-loop pipeline to the heat exchangers in the first main exhaust bypass cooling pipeline 19 and the second main exhaust bypass cooling pipeline 20, where it performs non-contact cooling and heat exchange on the steam drawn from the bypass of the exhaust steam main exhaust pipeline 13. The cooled steam returns to the exhaust steam main exhaust pipeline 13, couples with the main steam flow for further cooling, and then enters the condensing device 1 to complete the final condensation, thereby significantly reducing the turbine back pressure based on the original condensation process.

[0043] The exhaust outlet of the steam turbine 12 is connected to the inlet of the main exhaust pipe 13, and the outlet of the main exhaust pipe 13 is connected to the steam inlet of the condensing unit 1. The condensate outlet of the condensing unit 1 is connected to the inlet of the condensate tank 2; the outlet of the condensate tank 2 is connected to the inlet of the condensate pump 3, and the outlet of the condensate pump 3 is connected to the inlet of the flue gas waste heat non-contact heat exchange device 4; the outlet of the flue gas waste heat non-contact heat exchange device 4 is connected to the inlet of the heat energy compensation device 17; the outlet of the heat energy compensation device 17 is connected to the inlet of the driving heat source of the refrigeration unit 15; the outlet of the driving heat source of the refrigeration unit 15 is returned to the inlet of the flue gas waste heat non-contact heat exchange device 4 via the second circulation pump, forming a driving heat source circulation loop.

[0044] The refrigeration unit 15 is equipped with a chilled water outlet, a chilled water return, a drive heat source inlet, a drive heat source outlet, a cooling water inlet, and a cooling water outlet. The chilled water outlet of the refrigeration unit 15 is connected to the cold water inlet of the heat exchanger in the first main exhaust bypass cooling pipe 19 or the second main exhaust bypass cooling pipe 20 via a first circulating pump. The cold water outlet of the heat exchanger returns to the chilled water return of the refrigeration unit 15, forming a chilled water circulation loop.

[0045] The outlet of the condensate tank 2 is connected to the cooling water inlet of the refrigeration unit 15 via a pipe, and the cooling water outlet of the refrigeration unit 15 is returned to the return port of the condensate tank 2 via the third circulation pump, forming a cooling water circulation loop.

[0046] The inlet and outlet ends of the first main exhaust bypass cooling pipe 19 or the second main exhaust bypass cooling pipe 20 are respectively bypassed to the exhaust main exhaust pipe 13, and the inlet and outlet ends of the first main exhaust bypass cooling pipe 19 or the second main exhaust bypass cooling pipe 20 are respectively equipped with bypass on / off valves. A heat exchanger is installed inside the first main exhaust bypass cooling pipe 19 or the second main exhaust bypass cooling pipe 20. The heat exchanger has a cold water inlet and a cold water outlet. The cold water inlet is connected to the chilled water outlet end of the chiller unit 15, and the cold water outlet is connected to the chilled water return end of the chiller unit 15.

[0047] The intelligent linkage control system is connected to the steam temperature and pressure sensors at the steam inlet of the condensing unit 1, the temperature and pressure sensors on the main exhaust steam pipe 13, the flow and velocity sensors of each circulating pump, and the signal signals of each bypass valve. The intelligent linkage control system uses the steam temperature and back pressure at the steam inlet of the condensing unit 1 as the starting and control reference. The system is triggered to start when the back pressure reaches 13.5 kPa and the temperature exceeds 50°C. During system operation, by monitoring the flow, velocity, pressure, and temperature parameters of each key node in real time, the system automatically adjusts the output power of the refrigeration unit 15 and the opening and closing degrees of each circulating pump and control valve, achieving precise control of the back pressure and steam temperature within the main exhaust steam pipe 13.

[0048] Depend on Figure 1 The multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation provided in this application also includes a solar thermal compensation subsystem and a cooling tower auxiliary subsystem.

[0049] The solar thermal device 14 uses a solar concentrator to collect solar heat and stores it in the heat source energy storage device 16. The heat energy compensation device 17 is also equipped with a heat compensation input terminal, which is connected to the output terminal of the heat source energy storage device 16. When the heating outlet water temperature of the flue gas waste heat non-contact heat exchange device 4 is lower than the first preset threshold of 95°C, the heat energy compensation device 17 automatically starts, calling on the heat storage energy in the heat source energy storage device 16 to perform heat energy compensation on the driving heat source circulation loop, heating the driving heat source water to 100°C to ensure the continuous and stable cooling of the chiller unit 15. After doing work, the temperature of the driving heat source water drops to 70°C to 80°C and returns to the inlet of the flue gas waste heat non-contact heat exchange device 4 for recycling.

[0050] The multi-source coupled circulating thermal cooling back pressure reduction energy-saving system for thermal power generation may also include an independent open cooling tower, which is installed on the pipeline between the cooling water outlet of the chiller unit 15 and the return water inlet of the condensate tank 2. When the cooling water outlet temperature of the chiller unit 15 is higher than the second preset threshold of 32°C, the cooling water is cooled by the open cooling tower and then returned to the return water inlet of the condensate tank 2, ensuring that the cooling water temperature always meets the equipment requirements.

[0051] In a preferred embodiment, the main exhaust steam bypass cooling pipes of the multi-source coupled circulating thermal cooling back pressure reduction energy-saving system for thermal power generation provided in this application consist of two pipes: a first main exhaust steam bypass cooling pipe 19 and a second main exhaust steam bypass cooling pipe 20. These two main exhaust steam bypass cooling pipes are connected in parallel on the exhaust steam main exhaust pipe 13, and each main exhaust steam bypass cooling pipe is equipped with a heat exchanger. The intelligent linkage control system can adjust the flow rate and velocity of chilled water produced by the chiller unit entering the bypass cooling pipes according to the unit back pressure and saturated steam temperature, thereby achieving the purpose of temperature and pressure control, realizing single-path operation or dual-path parallel operation, and improving the system's operational flexibility and reliability.

[0052] Depend on Figure 1The multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation provided in this application also includes a feedwater system, which includes: a condensate polishing device 5, a low-pressure heater 6, a deaerator 7, a feedwater pump 8, a high-pressure heater 9, a boiler 10, a superheater 11, and a generator 18; the outlet of the flue gas waste heat non-contact heat exchange device 4 is connected to the inlet of the condensate polishing device 5 via a pipeline, and the outlet of the condensate polishing device 5 is connected to the inlet of the low-pressure heater 6 via a pipeline; the outlet of the low-pressure heater 6 is connected to the inlet of the deaerator 7 via a pipeline, and the outlet of the deaerator 7 is connected to the inlet of the feedwater pump 8 via a pipeline; the outlet of the feedwater pump 8 is connected to the inlet of the high-pressure heater 9 via a pipeline, and the outlet of the high-pressure heater 9 is connected to the feedwater inlet of the boiler 10 via a pipeline; the main steam outlet of the boiler 10 is connected to the inlet of the superheater 11 via a pipeline, and the outlet of the superheater 11 is connected to the steam inlet of the turbine 12 via a pipeline; the turbine 12 is coaxially connected to the generator 18 to convert the mechanical energy of the turbine 12 into electrical energy.

[0053] Example 1 This embodiment uses a 350 MW direct air-cooled coal-fired unit as the application object. The air-cooled island of this unit is designed with a back pressure of 12 kPa. Under extreme high temperature conditions in summer, the measured back pressure can reach 38 kPa. The measured temperature of the main exhaust pipe 13 is 77.5℃. The unit output is severely limited, and the coal consumption increases by 32 g / kWh.

[0054] The condensate at 35°C in the condensate tank 2 is pumped by the condensate pump 3 into the flue gas waste heat non-contact heat exchange device 4. The condensate is heated to 95°C to 100°C by the flue gas at 130°C after the boiler air preheater. When the temperature of the condensate after heating by the flue gas waste heat non-contact heat exchange device 4 is less than 95°C, the heated circulating water enters the heat energy compensation device 17 through the pipeline for secondary heating to 100°C. It then enters the refrigeration unit 15 as the driving heat source water to do work at the inlet end of the driving heat source. After doing work, the temperature of the driving heat source water drops to 75°C and returns to the inlet end of the flue gas waste heat non-contact heat exchange device 4 for recycling via the second circulation pump.

[0055] When the waste heat exchange of flue gas is insufficient and the outlet water temperature is below 95°C, the solar thermal energy stored in the heat source energy storage device 16 is automatically replenished by the heat energy compensation device 17 to maintain the driving heat source temperature at 100°C.

[0056] The refrigeration unit 15 uses the aforementioned 100°C heat source water as its driving energy to produce 18°C ​​chilled water with a cooling capacity of 2800 kW. The chilled water is driven by the first circulation pump through a closed-loop pipeline to the chilled water inlet of the heat exchanger in the first main exhaust bypass cooling pipeline 19 and the second main exhaust bypass cooling pipeline 20. Simultaneously, the condensate tank 2 provides 30°C cooling water to the lithium bromide refrigeration unit 15. After cooling and performing work, the water returns to the condensate tank 2 via the third circulation pump. In this embodiment, the refrigeration unit 15 is a lithium bromide chilled water coupling generator.

[0057] Exhaust steam is drawn from the main exhaust pipe 13 via a bypass and enters the heat exchanger within the first main exhaust bypass cooling pipe 19. There, it undergoes non-contact heat exchange with 18°C ​​chilled water. The steam then returns to the main exhaust pipe 13 from the outlet of the first main exhaust bypass cooling pipe 19, where it couples and mixes with the main steam flow. It then enters the heat exchanger within the second main exhaust bypass cooling pipe 20, where it again undergoes non-contact heat exchange with 18°C ​​chilled water. The steam temperature drops from the initial 77°C to 65°C. The cooled steam then returns to the main exhaust pipe 13 from the outlet of the second main exhaust bypass cooling pipe 20, where it couples and mixes with the main steam flow. The resulting steam temperature is 65°C, and it enters the condenser 1 for condensation. The chilled water temperature of the cooling steam rises to 28°C and is then returned to the refrigerant water return port of the lithium bromide refrigeration unit via a circulating pump, completing the refrigerant water circulation.

[0058] After the implementation of the multi-source coupled cycle heat and cooling back pressure reduction energy-saving system for thermal power generation, the unit back pressure dropped from 38 kPa to 18 kPa, a reduction of 20 kPa; the temperature of the main exhaust steam pipe 13 dropped from 77℃ to 58℃; the unit coal consumption decreased by 22 g / kWh; the power consumption rate of the air-cooled fan plant decreased by 48%; and the economic benefits and safety of the unit during the high-temperature period in summer were significantly improved.

[0059] Example 2 This embodiment takes a 600 MW indirect air-cooled coal-fired unit as the application object. Under extreme summer conditions, the back pressure of this unit can reach 36 kPa and the temperature of the main exhaust pipe 13 can reach 75℃. After configuring a multi-source coupled cycle thermal cooling and back pressure reduction energy-saving system for thermal power generation, the system parameters are as follows.

[0060] The flue gas waste heat non-contact heat exchange device 4 heats the condensate circulating water to 95℃~100℃. When the temperature after heating by the flue gas waste heat non-contact heat exchange device 4 is less than 95℃, it is heated to 100℃ again by the heat energy compensation device 17. The heat source water flow rate is 220t / h. The refrigeration unit 15 has a cooling capacity of 4500 kW and produces chilled water at a temperature of 18°C. In this embodiment, the refrigeration unit 15 is a lithium bromide chilled water coupling generator.

[0061] The exhaust steam drawn to the main exhaust bypass cooling pipe is cooled from 75°C to 48°C after heat exchange through the first main exhaust bypass cooling pipe 19 and the second main exhaust bypass cooling pipe 20. After returning to the main exhaust pipe and coupling, the main steam temperature drops to 66°C and enters the indirect air-cooled radiator for condensation and heat exchange. The back pressure drops from 36 kPa to 15 kPa, a reduction of 21 kPa. Coal consumption decreases by 25 g / kWh, and the energy consumption of auxiliary equipment such as the indirect air-cooled circulating water pump decreases by 52%.

[0062] When the waste heat exchange of flue gas is insufficient at night and on cloudy days, the heat source energy storage device 16, with a capacity of 5000 kWh, automatically replenishes the heat to the driving heat source circulation loop through the heat energy compensation device 17, ensuring that the system can operate continuously and stably for 6 hours, so that the system can maintain its cooling capacity during the high temperature period of the whole day.

[0063] Example 3 This embodiment takes a 450 MW condensing unit with a wet cooling tower as the application object. Under extreme high temperature conditions in summer, the circulating water temperature is high and the unit back pressure reaches 35 kPa. After configuring a multi-source coupled circulating heat and cooling energy-saving system for thermal power generation to reduce back pressure, the system operating parameters are as follows.

[0064] The condensate water temperature is 40℃. It is pumped by condensate water pump 3 into the flue gas waste heat non-contact heat exchange device 4, where it is heated to 95℃~100℃. When the temperature after heating by the flue gas waste heat non-contact heat exchange device 4 is less than 95℃, the heat compensation device 17 supplements the heat to 100℃, driving the refrigeration unit 15 to produce 18℃ chilled water, with a cooling capacity of 3200 kW. In this embodiment, the refrigeration unit 15 is a screw chiller.

[0065] When the waste heat exchange of flue gas is insufficient and the outlet water temperature is below 95°C, the solar thermal energy stored in the heat source energy storage device 16 is automatically replenished by the heat energy compensation device 17 to maintain the driving heat source temperature at 100°C.

[0066] Steam drawn from the main exhaust pipe 13 is cooled from 74°C to 45°C after passing through the first main exhaust bypass cooling pipe 19 and the second main exhaust bypass cooling pipe 20. After coupling back, the main steam temperature drops to 62°C, the unit back pressure drops from 35 kPa to 14 kPa, a decrease of 21 kPa; coal consumption decreases by 24 g / kWh; and the power consumption of auxiliary equipment such as the wet cooling tower circulating water pump decreases by 45%.

[0067] When the cooling water temperature is insufficient, especially under extreme high-temperature conditions, the condensate tank 2 is connected to an open cooling tower for auxiliary cooling to ensure that the cooling water temperature of the screw chiller unit 15 always meets the equipment requirements and ensures reliable system operation.

[0068] Comparative Example 1 In this comparative example, on the unit of Example 1, only the flue gas waste heat non-contact heat exchange device 4 is used as the driving heat source, and the compensation functions of the solar thermal device 14 and the heat source energy storage device 16 are not used. The rest of the system structure is the same.

[0069] In this comparative example, under cloudy or nighttime operating conditions, the waste heat exchange capacity of the flue gas is low, and the outlet temperature of the driving heat source water is only 78°C, which does not meet the driving temperature requirement of 15-100°C for the lithium bromide chiller unit. The system cooling capacity is only 800 kW, which is 71% lower than that of Example 1. The bypass cooling effect is significantly reduced, and the back pressure is only reduced by 6 kPa, which illustrates the necessity of the solar thermal energy storage compensation system to maintain the system's all-weather cooling capacity.

[0070] Comparative Example 2 In this comparative example, on the unit of Example 1, the chilled water produced by the lithium bromide refrigeration unit 15 is directly used for spray cooling on the surface of the air-cooled radiator, without introducing the main exhaust bypass cooling pipe, that is, without actively pre-cooling the exhaust steam.

[0071] In this comparative example, under the same cooling capacity, the unit back pressure was reduced by only 8 kPa and the coal consumption was reduced by 9 g / KWh, which is far lower than the effect of reducing back pressure by 20 kPa and reducing coal consumption by 22 g / KWh in Example 1. This indicates that bypassing the main exhaust pipe for active pre-cooling of exhaust steam has a more significant effect on reducing back pressure than simply using air-cooled auxiliary cooling.

[0072] Table 1 Key technical effects data of each embodiment and comparative example As shown in the table above, Examples 1 to 3 of this application all achieved a significant reduction in back pressure, with a reduction of 20-21 kPa, a reduction in coal consumption of 22-25 g / kWh, and a reduction in plant power consumption of 45%-52%, which is far superior to the comparative examples.

[0073] In this application, the plant power consumption rate refers to the proportion of electricity consumed by the power plant itself during the power generation process to the total power generation.

[0074] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation, comprising: The system comprises a steam turbine, a main exhaust steam pipeline, a condensing unit, a condensate tank, and a condensate pump; the exhaust outlet of the steam turbine is connected to the inlet end of the main exhaust steam pipeline, and the outlet end of the main exhaust steam pipeline is connected to the steam inlet of the condensing unit; the condensate outlet of the condensing unit is connected to the inlet of the condensate tank; and the outlet of the condensate tank is connected to the inlet of the condensate pump; characterized in that it further comprises: a main exhaust steam bypass cooling pipeline, a refrigeration unit, a non-contact heat exchange device for flue gas waste heat, a thermal energy compensation device, a solar thermal device, and a heat source energy storage device; The inlet and outlet ends of the main exhaust steam bypass cooling pipe are respectively connected to the main exhaust steam pipe. A heat exchanger is installed in the main exhaust bypass cooling pipe, and the heat exchanger has a cold water inlet and a cold water outlet; The refrigeration unit is equipped with a chilled water outlet and a chilled water return, a drive heat source inlet and a drive heat source outlet, a cooling water inlet and a cooling water outlet; The chilled water outlet of the chiller unit is connected to the cold water inlet of the heat exchanger, and the chilled water return of the chiller unit is connected to the cold water outlet of the heat exchanger, forming a chilled water circulation loop. The outlet of the condensate pump is connected to the inlet of the flue gas waste heat non-contact heat exchange device; the outlet of the flue gas waste heat non-contact heat exchange device is connected to the inlet of the heat energy compensation device; the outlet of the heat energy compensation device is connected to the inlet of the driving heat source of the refrigeration unit; and the outlet of the driving heat source of the refrigeration unit is connected to the inlet of the flue gas waste heat non-contact heat exchange device, forming a driving heat source circulation loop. The condensate tank is equipped with a return water inlet; the outlet of the condensate tank is connected to the cooling water inlet of the refrigeration unit, and the return water inlet of the condensate tank is connected to the cooling water outlet of the refrigeration unit, forming a cooling water circulation loop. The thermal energy output end of the solar thermal device is connected to the input end of the heat source energy storage device.

2. The multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation as described in claim 1, characterized in that, The main exhaust bypass cooling pipe is equipped with bypass on / off valves at both its inlet and outlet ends. A first circulation pump is installed on the pipeline between the chilled water outlet of the refrigeration unit and the cold water inlet of the heat exchanger. A second circulation pump is installed on the pipeline between the outlet end of the driving heat source of the refrigeration unit and the inlet of the flue gas waste heat non-contact heat exchange device. A third circulation pump is provided between the cooling water outlet of the refrigeration unit and the return water inlet of the condensate tank.

3. The multi-source coupled cycle thermal cooling and back pressure reduction energy-saving system for thermal power generation as described in claim 2, characterized in that, Temperature sensors and pressure sensors are installed at the steam inlet of the condensing device and on the main exhaust pipe of the waste steam; flow sensors and velocity sensors are installed on the outlet pipes of the first circulation pump, the second circulation pump and the third circulation pump. The multi-source coupled circulating heat and cooling back pressure reduction energy-saving system for thermal power generation also includes an intelligent linkage control system. The intelligent linkage control system is connected to the temperature and pressure sensors at the steam inlet of the condensing device, the temperature and pressure sensors on the main exhaust steam pipeline, the flow rate and flow sensor of each circulating pump, and the signal of each bypass opening and closing valve.

4. The multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation as described in claim 1, characterized in that, The thermal energy compensation device is also provided with a heat replenishment input terminal, which is connected to the output terminal of the heat source energy storage device. When the heating outlet water temperature of the flue gas waste heat non-contact heat exchange device is lower than the first preset threshold, the thermal energy compensation device calls the heat storage energy in the heat source energy storage device to perform thermal energy compensation on the driving heat source circulation loop.

5. The multi-source coupled cycle thermal cooling and back pressure reduction energy-saving system for thermal power generation as described in claim 4, characterized in that, The first preset threshold is 95°C; When the temperature of the heated water outlet of the flue gas waste heat non-contact heat exchange device is lower than the first preset threshold, the heat energy compensation device heats the hot water temperature in the driving heat source circulation loop to 100°C. The hot water heated to 100°C serves as the driving heat source, driving the refrigeration component to perform refrigeration work. After the work is performed, the hot water is discharged from the outlet of the driving heat source of the refrigeration component at a temperature of 70°C to 80°C. The hot water at 70°C to 80°C is returned to the inlet of the flue gas waste heat non-contact heat exchange device for recycling.

6. The multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation as described in claim 1, characterized in that, The multi-source coupled circulating thermal cooling back pressure reduction energy-saving system for thermal power generation also includes: an open cooling tower, which is installed on the pipeline between the cooling water outlet of the refrigeration unit and the return water inlet of the condensate tank; when the cooling water outlet temperature of the refrigeration unit is higher than a second preset threshold, the cooling water is cooled by the open cooling tower and then returned to the return water inlet of the condensate tank.

7. The multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation as described in claim 1, characterized in that, The main exhaust bypass cooling pipe may be one or more; when there are multiple main exhaust bypass cooling pipes, they are connected in parallel to the sections before and after the main exhaust pipe; or, When there are multiple main exhaust bypass cooling pipes, the main exhaust bypass cooling pipes are installed on the branch pipes of the exhaust main exhaust pipe.

8. The multi-source coupled cycle thermal cooling and back pressure reduction energy-saving system for thermal power generation as described in claim 1, characterized in that, The condensation device can be any one of a direct air-cooling device, an indirect air-cooling device, a water-cooled tower, or a wet cooling tower. The refrigeration unit is one of a screw chiller, a lithium bromide refrigeration unit, or an air source heat pump chiller. The chilled water produced by the refrigeration unit has a temperature of 15℃ to 20℃.

9. A method for operating a multi-source coupled cycle thermal cooling back pressure reduction energy-saving system for thermal power generation as described in any one of claims 1 to 8, comprising the following steps: (1) The system is started based on the steam temperature and back pressure at the steam inlet of the condenser. When the back pressure reaches 13.5 kPa and the temperature exceeds 50°C, the system is triggered to start. The condensate formed by the condensing device enters the condensate tank and is pumped by the condensate pump to the flue gas waste heat non-contact heat exchange device to be heated to 95℃~100℃. When the temperature of the heated water outlet is lower than 95℃, it is heated to 100℃ by the heat energy compensation device and used as a driving heat source to enter the refrigeration unit to do work and produce 15℃~20℃ cold water. After doing work, the 70℃~80℃ hot water discharged from the driving heat source outlet of the refrigeration unit is recycled back to the inlet of the flue gas waste heat non-contact heat exchange device for reheating and reuse. (2) The chilled water produced by the chiller unit at 15℃~20℃ is transported to the heat exchanger in the main exhaust bypass cooling pipe through the chilled water outlet of the chiller unit. The steam in the main exhaust bypass cooling pipe is cooled and depressurized by non-contact heat exchange. The cooled and depressurized steam returns to the exhaust steam main exhaust pipe and couples with the main steam flow to cool and depressurize. Then it enters the condenser to complete the condensation. The temperature of the chilled water rises to 20℃~25℃ after heat exchange and work on the steam. It returns to the chilled water return port of the chiller unit through the chilled water outlet of the heat exchanger to complete the chilled water circulation. (3) The condensate in the condensate tank enters the cooling water inlet of the refrigeration unit through the outlet of the condensate tank. After cooling the refrigeration unit, the cooling water returns to the return outlet of the condensate tank through the third circulation pump.

10. The operating method as described in claim 9, characterized in that, The operating method further includes step (4), the specific process of which is as follows: The intelligent linkage control system monitors the inlet steam temperature and pressure of the condensing unit and the steam parameters of the main exhaust steam pipeline in real time. Based on the changes in the unit's back pressure and saturated steam temperature, the intelligent linkage control system automatically adjusts the output power of the refrigeration unit, the speed of each circulating pump, and the opening and closing of each bypass valve. The operation method also includes a thermal energy compensation step. When the outlet water temperature of the flue gas waste heat non-contact heat exchange device is lower than the first preset threshold of 95°C, the thermal energy compensation device is automatically activated and the thermal energy stored in the heat source energy storage device is used to perform thermal energy compensation on the driving heat source circulation loop. In the operation method, when the temperature of the cooling water in step (3) is higher than the second preset threshold, an open cooling tower is introduced to cool it down.

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