A thermal power unit cross-load internal heat storage and release system and operation method

Abstract

The present invention discloses a cross-load internal heat storage and release system and operating method for a thermal power unit. The system specifically includes a boiler, a steam turbine, a low-pressure heater, a high-pressure heater, a steam-water heat exchanger, a hot water tank, a cold water tank, a control valve, and a water pump. The hot water tank absorbs and stores heat when the thermal power unit is under high load. During low-load peak-shaving operation, the heat is released back into the internal circulation. During high-load peak-shaving operation, condensate from the outlet of a certain heater stage can be used for cross-load steam-water reconstitution. This sacrifices some high-load efficiency, increasing the high-load coal consumption rate. However, at low loads, efficiency improves, reducing the low-load coal consumption rate. By sacrificing the high-load coal consumption rate and increasing the low-load coal consumption rate to compensate for the reduced high-load coal consumption rate, the total coal consumption is reduced during peak-shaving operation. This invention provides a method for integrating the thermal power unit and the heat storage tank within the internal circulation, and for cross-load and cross-unit steam-water flow reconfiguration for peak-shaving operation. This method requires only a minimal-capacity heat storage tank to achieve cross-load heat tiered distribution and steam-water flow reconfiguration. Furthermore, low-load coal consumption reduction allows the unit to operate at low loads, achieving both peak-shaving and economic advantages.

Description

Technical Field

[0001] The present invention relates to the technical field of power generation, and in particular to a cross-load internal heat storage and release system for a thermal power unit and an operating method thereof. Background Art

[0002] Currently, there is a heated discussion on using heat storage to promote the consumption of renewable electricity. The integration of heat storage tanks and thermal power units in domestic and foreign research has two main purposes: 1. To avoid the strong coupling of heat and electricity to a certain extent by taking advantage of the heat storage and release process of the heat storage tank; 2. To increase the load response rate of the unit by using the heat storage tank as an additional heat source or heat load. However, the coal consumption of the unit increases significantly at lower loads. For a certain pure condensing unit, the difference in coal consumption between 100% load and 30% load is 37.5g / kWh, and this difference will increase further when the unit is in deep peak regulation. The integration of heat storage tanks and thermal power units based on the above purposes is difficult to fundamentally avoid the problem of increased coal consumption during deep peak regulation of the unit. The use of heat storage tanks in deep peak regulation needs to be expanded. To this end, the present invention proposes a cross-load internal heat storage and release system for a thermal power unit and an operating method. By integrating the thermal power unit and the heat storage tank inside the cycle, heat is stored according to the unit load, and high storage and low use are achieved, thereby realizing cross-load steam-water process reconstruction. By sacrificing the high-load power generation coal consumption rate and increasing the low-load power generation coal consumption rate to compensate for the reduction in the high-load power generation coal consumption rate, the purpose of reducing the total coal consumption during deep peak regulation of the unit is achieved with a small-capacity heat storage tank. Summary of the Invention

[0003] To this end, the present invention proposes a cross-load internal heat storage and release system and operation method for a thermal power unit, so as to realize the integrated integration of the thermal power unit and the heat storage tank, and the reconstruction of the steam-water process for heat cross-load internal transfer, thereby further reducing the total coal consumption of the unit.

[0004] In order to achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0005] In order to realize the flexible heat supply of a heat storage tank according to temperature fluctuation, the present invention proposes a cross-load internal heat storage and release system for a thermal power unit, the system comprising a boiler (1), a steam turbine (2), a steam-water heat exchanger (3), a condenser (4), a first diverter (5), a condensate pump (6), a condensate booster pump (7), a first mixer (8), a second mixer (9), a low-pressure heater (10), a deaerator (11), a feed water pump (12), a high-pressure heater (13), a first control valve (14), a cold fluid source (15), a hot water tank (16), a hot tank outlet pump (17), a second control valve (18), a third control valve (19), a cold tank inlet pump (20), a cold water tank (21), a cold tank outlet pump (22), and a fourth control valve (23).

[0006] Furthermore, the outlet of the boiler (1) is connected to the inlet of the steam turbine (2), the steam extraction port of the steam turbine (2) is connected to the hot fluid inlet of the steam-water heat exchanger (3), the outlet of the steam turbine (2) is connected to the inlet of the condenser (4), the outlet of the condenser (4) is connected to the inlet of the first diverter (5), the first outlet of the first diverter (5) is connected to the inlet of the condensate pump (6), the outlet of the condensate pump (6) is connected to the inlet of the condensate booster pump (7), and the outlet of the condensate booster pump (7) is connected to the inlet of the condensate pump (6). The first inlet of the first mixer (8) and the outlet of the first mixer (8) are connected to the first inlet of the second mixer (9), the outlet of the second mixer (9) is connected to the inlet of the low-pressure heater (10), the outlet of the low-pressure heater (10) is connected to the inlet of the deaerator (11), the outlet of the deaerator (11) is connected to the inlet of the feed water pump (12), the outlet of the feed water pump (12) is connected to the inlet of the high-pressure heater (13), and the outlet of the high-pressure heater (13) is connected to the boiler (1).

[0007] Furthermore, the hot fluid inlet of the steam-water heat exchanger (3) is connected to the steam extraction port of the steam turbine (2), the hot fluid outlet of the steam-water heat exchanger (3) is connected to the inlet of the first control valve (14), and the cold fluid inlet of the steam-water heat exchanger (3) is connected to the cold fluid source (15).

[0008] Furthermore, the inlet of the hot water tank (16) is connected to the outlet of the first control valve (14), the outlet of the hot water tank (16) is connected to the inlet of the hot water tank outlet pump (17), the outlet of the hot water tank outlet pump (17) is connected to the inlet of the second control valve (18), the outlet of the second control valve (18) is connected to the second inlet of the second mixer (9), the second outlet of the first diverter (5) is connected to the inlet of the third control valve (19), the outlet of the third control valve (19) is connected to the inlet of the cold water tank inlet pump (20), the outlet of the cold water tank inlet pump (20) is connected to the inlet of the cold water tank (21), the outlet of the cold water tank (21) is connected to the inlet of the cold water tank outlet pump (22), the outlet of the cold water tank outlet pump (22) is connected to the inlet of the fourth control valve (23), and the outlet of the fourth control valve (23) is connected to the second inlet of the first mixer (8).

[0009] Furthermore, the present invention further proposes a method for operating a cross-load internal heat storage and release system of a thermal power unit, comprising:

[0010] The steam from the outlet of the boiler (1) enters the steam turbine (2) and is divided into two streams in the steam turbine (2). The first stream of steam, after doing part of the work, enters the hot fluid inlet of the steam-water heat exchanger (3) from the steam extraction port of the steam turbine (2) to exchange heat. The second stream of steam, after doing the work of the steam turbine (2), becomes low-pressure steam and enters the condenser (4) from the inlet of the steam turbine (2) to be cooled into condensate and flows into the first diverter (5) to be divided into two streams. The second stream of steam at the outlet of the first diverter (5) flows into the third control valve (19) and enters The first stream of water at the outlet of the first diverter (5) flows out from the first outlet of the first diverter (5), flows into the first mixer (8) from the first inlet of the first mixer (8) after passing through the condensate pump (6) and the condensate booster pump (7), and flows into the second mixer (9) from the first inlet of the second mixer (9), and flows into the low-pressure heater (10) from the outlet of the second mixer (9), and flows through the deaerator (11), the feed water pump (12), and the high-pressure heater (13) in sequence to enter the boiler (1).

[0011] Furthermore, the method further comprises:

[0012] In order to realize that the heat storage tank transfers the heat of the high-load unit to the low-load unit for utilization, the thermal power unit uses internal heat to supplement the heat of the hot water tank during high-load operation: the first control valve (14) and the fourth control valve (23) are in the open state, the second control valve (18) and the third control valve (19) are in the closed state, and the hot water tank (16) stores heat. The steam from the steam extraction port of the steam turbine (2) enters through the hot fluid inlet of the steam-water heat exchanger (3) and, after exchanging heat in the steam-water heat exchanger (3), enters the first control valve (14) through the hot fluid outlet of the steam-water heat exchanger (3), enters the inlet of the hot water tank (16) through the first control valve (14) to store heat, and the fluid in the cold water tank (21) passes through the cold tank outlet pump and the fourth control valve (23), and is mixed with the condensate of the first inlet of the first mixer (8) through the second inlet of the first mixer (8) and enters the low-pressure heater (10) through the second mixer (9) to absorb heat.

[0013] In order to reduce coal consumption during low-load peak regulation of thermal power units, the hot water tank releases high-load heat into the circulation in an orderly manner: the second control valve (18) and the third control valve (19) are in an open state, the first control valve (14) and the fourth control valve (23) are in a closed state, and the hot water tank (16) releases heat. Condensate flows from the second outlet of the first diverter (5) through the third control valve (19) and the water inlet pump of the cold water tank (21) into the cold water tank (21). The outlet fluid of the hot water tank (16) flows through the hot water tank outlet pump (17) and the second control valve (18) through the second inlet of the second mixer (9) and is mixed with the water at the first inlet of the second mixer (9) and continues to absorb heat.

[0014] Furthermore, when the thermal power unit is in low-load peak-shaving operation, during the heat release process of the hot water tank (16), the outlet fluid of the hot water tank (16) is not limited to the heat release position, but can flow into the corresponding position according to the temperature of the heat recovery heaters at each level and the temperature of the hot fluid of the hot water tank (16). By predicting the low-load peak-shaving operation time and high-load operation time of the unit, as well as the current heat storage capacity of the hot water tank (16), the high-load heat storage flow rate and the low-load heat release flow rate of the hot water tank (16) are allocated, thereby ensuring that the cross-load reforming steam-water process can make up for the high-load coal consumption increase value with the low-load coal consumption reduction value within the corresponding time and obtain the maximum cumulative benefit.

[0015] Furthermore, the cold fluid heated by the steam-water heat exchanger (3) can come from inside or outside the cycle, and form different cross-load internal heat storage and release systems and operating modes. When the cold fluid heated by the steam-water heat exchanger (3) comes from the inside of the cycle, such as the cold water tank (21), the outlet water of a certain stage heater, etc., during the system integration process, a regenerative heater can be added to compensate for the efficiency drop caused by the heat storage process and reuse the drain heat storage, or the regenerative heater drain heat storage is directly used to maintain the number of regenerative heating stages, both of which can realize the cross-load internal steam-water process reconstruction of the thermal power unit containing the hot water tank (16) heat storage process; when the cold fluid heated by the steam-water heat exchanger (3) comes from the outside of the cycle, when the cold fluid is the heat network return water, the heat of the hot water tank (16) is transferred between high load and low load, and can realize the cascade utilization and cross-load internal utilization of the exothermic steam with the help of the external heat load, or can be the condensate, feed water, and drain of the adjacent high back pressure unit. At this time, a steam-water heat exchanger (3) can be set to further heat or the steam-water heat exchanger (3) can be directly heated into the heat storage tank without being set to realize the heat transfer across the units, and the cross-unit heat storage and release process is completed according to the coal consumption loss of the high back pressure unit and the coal consumption benefit of the pure condensing unit. The former has a more obvious benefit during deep peak load regulation. The hot fluid of the steam-water heat exchanger (3) can come from the internal circulation, such as steam extraction and drainage from the steam turbine (2), or from the external circulation, such as boiler flue gas, industrial waste heat, steam from adjacent units, or drainage.

[0016] Furthermore, the cold fluid and the hot fluid are not limited to a single source. Multiple cold fluids can come from the inside of the cycle, the outside of the cycle, directly store heat, absorb heat separately, or absorb heat after mixing in accordance with water quality requirements. Multiple hot fluids can come from the inside of the cycle, the outside of the cycle, and provide heat. Depending on the operating state, hot fluids from different sources can heat the cold fluid in stages according to temperature matching at the same time, or hot fluids from different sources can heat the cold fluid separately at different time periods. The cold fluid then gains heat and enters the hot water tank (16) for storage. The destination of the fluid in the hot water tank (16) is also not restricted. It can participate in heat supply or enter the heat recovery system according to demand.

[0017] Furthermore, the system is not limited to dual-tank thermal storage. Using dual-tank thermal storage avoids the temperature impact of heat storage and release, but increases investment and floor space. Using a single-tank thermal storage system also faces the impact of cyclical heat storage and release on the thermocline, impacting coal consumption, but reduces investment and floor space. Regardless of whether the cross-load steam-water process reconfiguration includes an external steam-water source, using a thermocline thermal storage tank instead of dual-tank thermal storage can achieve the same function.

[0018] The present invention has the following advantages:

[0019] The present invention discloses a cross-load internal heat storage and release system for a thermal power unit and its operating method. The system specifically includes a boiler, a steam turbine, a low-pressure heater, a high-pressure heater, a steam-water heat exchanger, a hot tank, a cold tank, a control valve, a water pump, etc. Considering the large fluctuations in unit load under peak-shaving demand, in order to reduce the unit's coal consumption rate during peak-shaving operation, the hot water tank can store heat when the unit is under high load. At this time, the unit sacrifices some efficiency for the heat storage process in the hot water tank. When the unit is under low load operation, the hot water tank releases heat back into the internal circulation. Due to the cross-load exhaust steam extraction effect and the increase in feedwater temperature, the unit efficiency increases and the coal consumption rate decreases. The calculation of a 350MW unit shows the following advantages: 1. The unit's thermal storage process increases the unit's coal consumption rate at 100% load by 0.253g / kWh, while the unit's thermal release process reduces the unit's coal consumption rate at 30% load by 0.860g / kWh. When the unit's operating time at 100% load and 30% load is 1:1, the coal consumption rate can be reduced by 0.606g / kWh. 2. If the unit can achieve a 10-hour change in operating mode, it only takes 1000m 3 The hot water tank is much smaller than the existing hot water tanks in operation. 3. The reduction in power generation coal consumption rate will increase exponentially with the increase in heat storage and release flow rate. The thermal storage tank parameters can be appropriately selected based on peak load timing and demand. The proposed cross-load internal heat storage and release system for thermal power units utilizes a thermal storage tank to achieve integrated integration of the thermal power unit and the thermal storage tank, reconstructing the steam-water flow path for cross-load internal heat transfer. This reduction in high-load power generation coal consumption rate is offset by sacrificing the high-load power generation coal consumption rate and increasing the low-load power generation coal consumption rate, thus reducing the unit's total coal consumption with a small-capacity thermal storage tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are merely exemplary, and those skilled in the art can, without inventive effort, derive other implementation drawings based on the provided drawings.

[0021] Figure 1 The present invention provides a schematic diagram of the system flow of a cross-load internal heat storage and release system for a thermal power unit.

[0022] Figure 2 The present invention provides a schematic diagram of the system flow of a single-tank heat storage and release system for a thermal power unit across loads.

[0023] Figure 3 The present invention provides a flow chart of a condensing unit system with a cross-load internal heat storage and release system in a thermal power unit combined with heat network return water reconstruction.

[0024] Figure 4 This is a schematic diagram of the cross-unit system flow in the cross-load internal heat storage and release system of a thermal power unit provided by the present invention.

[0025] Figure 5 The present invention provides a schematic flow chart of a pure condensing unit system with internal steam-water circulation and reconstruction in a cross-load internal heat storage and release system of a thermal power unit.

[0026] In the figure: 1. Boiler; 2. Steam turbine; 3. Steam-water heat exchanger; 4. Condenser; 5. First diverter; 6. Condensate pump; 7. Condensate booster pump; 8. First mixer; 9. Second mixer; 10. Low-pressure heater; 11. Deaerator; 12. Feedwater pump; 13. High-pressure heater; 14. First control valve; 15. Cold fluid source; 16. Hot water tank; 17. Hot tank outlet pump; 18. Second control valve; 19. Third control valve; 20. Cold tank inlet pump; 21. Cold water tank; 22. Cold tank outlet pump; 23. Fourth control valve; 24. Inclined temperature layer thermal storage tank; 25. Heat user; 26. High back-pressure unit diversion pipeline; 27. High back-pressure unit mixing pipeline; 28. Second diverter. DETAILED DESCRIPTION

[0027] The following describes the implementation of the present invention using specific embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. Obviously, the embodiments described are only a portion of the present invention, not all of it. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0028] The present invention proposes a thermal power unit cross-load internal heat storage and release system, such as Figure 1As shown, the system includes a boiler (1), a steam turbine (2), a steam-water heat exchanger (3), a condenser (4), a first diverter (5), a condensate pump (6), a condensate booster pump (7), a first mixer (8), a second mixer (9), a low-pressure heater (10), a deaerator (11), a feedwater pump (12), a high-pressure heater (13), a first control valve (14), a cold fluid source (15), a hot water tank (16), a hot tank outlet pump (17), a second control valve (18), a third control valve (19), a cold tank inlet pump (20), a cold water tank (21), a cold tank outlet pump (22), and a fourth control valve (23). The hot water tank is used to realize the integration of the thermal power unit and the heat storage tank, and the steam-water flow process reconstruction with heat transfer across the load is realized. By sacrificing the high-load power generation coal consumption rate and increasing the low-load power generation coal consumption rate to compensate for the reduction in the high-load power generation coal consumption rate, the total coal consumption of the unit is reduced by using a small-capacity heat storage tank.

[0029] In this embodiment, the outlet of the boiler (1) is connected to the inlet of the steam turbine (2), the steam extraction port of the steam turbine (2) is connected to the hot fluid inlet of the steam-water heat exchanger (3), the outlet of the steam turbine (2) is connected to the inlet of the condenser (4), the outlet of the condenser (4) is connected to the inlet of the first diverter (5), the first outlet of the first diverter (5) is connected to the inlet of the condensate pump (6), the outlet of the condensate pump (6) is connected to the inlet of the condensate booster pump (7), the outlet of the condensate booster pump (7) is connected to the first inlet of the first mixer (8), the outlet of the first mixer (8) is connected to the first inlet of the second mixer (9), the outlet of the second mixer (9) is connected to the inlet of the low-pressure heater (10), the outlet of the low-pressure heater (10) is connected to the inlet of the deaerator (11), the outlet of the deaerator (11) is connected to the inlet of the feed water pump (12), the outlet of the feed water pump (12) is connected to the inlet of the high-pressure heater (13), and the outlet of the high-pressure heater (13) is connected to the boiler (1).

[0030] The hot fluid inlet of the steam-water heat exchanger (3) is connected to the steam extraction port of the steam turbine (2), the hot fluid outlet of the steam-water heat exchanger (3) is connected to the inlet of the first control valve (14), and the cold fluid inlet of the steam-water heat exchanger (3) is connected to the cold fluid source (15).

[0031] The inlet of the hot water tank (16) is connected to the outlet of the first control valve (14), the outlet of the hot water tank (16) is connected to the inlet of the hot water tank outlet pump (17), the outlet of the hot water tank outlet pump (17) is connected to the inlet of the second control valve (18), the outlet of the second control valve (18) is connected to the second inlet of the second mixer (9), the second outlet of the first diverter (5) is connected to the inlet of the third control valve (19), the outlet of the third control valve (19) is connected to the inlet of the cold water tank inlet pump (20), the outlet of the cold water tank inlet pump (20) is connected to the inlet of the cold water tank (21), the outlet of the cold water tank (21) is connected to the inlet of the cold water tank outlet pump (22), the outlet of the cold water tank outlet pump (22) is connected to the inlet of the fourth control valve (23), and the outlet of the fourth control valve (23) is connected to the second inlet of the first mixer (8).

[0032] The present invention also relates to a method for operating a cross-load internal heat storage and release system of a thermal power unit, comprising the following steps:

[0033] The steam from the outlet of the boiler (1) enters the steam turbine (2) and is divided into two streams in the steam turbine (2). The first stream of steam, after doing part of the work, enters the hot fluid inlet of the steam-water heat exchanger (3) from the steam extraction port of the steam turbine (2) to exchange heat. The second stream of steam, after doing the work of the steam turbine (2), becomes low-pressure steam and enters the condenser (4) from the inlet of the steam turbine (2) to be cooled into condensate and flows into the first diverter (5) to be divided into two streams. The second stream of steam at the outlet of the first diverter (5) flows into the third control valve (19) and enters The first stream of water at the outlet of the first diverter (5) flows out from the first outlet of the first diverter (5), flows into the first mixer (8) from the first inlet of the first mixer (8) after passing through the condensate pump (6) and the condensate booster pump (7), and flows into the second mixer (9) from the first inlet of the second mixer (9), and flows into the low-pressure heater (10) from the outlet of the second mixer (9), and flows through the deaerator (11), the feed water pump (12), and the high-pressure heater (13) in sequence to enter the boiler (1).

[0034] The process of cross-load internal heat storage and release to achieve cross-load expulsion and heat utilization in the present invention includes the following two parts:

[0035] In the first part, in order to realize that the heat storage tank transfers the heat of the high-load unit to the low-load unit for utilization, the thermal power unit uses internal heat to supplement the heat of the hot water tank during high-load operation: the first control valve (14) and the fourth control valve (23) are in the open state, the second control valve (18) and the third control valve (19) are in the closed state, and the hot water tank (16) stores heat. The steam from the steam extraction port of the steam turbine (2) enters the hot fluid inlet of the steam-water heat exchanger (3) and, after exchanging heat in the steam-water heat exchanger (3), enters the first control valve (14) from the hot fluid outlet of the steam-water heat exchanger (3), passes through the first control valve (14) and enters the inlet of the hot water tank (16) for heat storage. The fluid in the cold water tank (21) passes through the cold tank outlet pump and the fourth control valve (23), and then is mixed with the condensate of the first inlet of the first mixer (8) at the second inlet and passes through the second mixer (9) to enter the low-pressure heater (10) to absorb heat.

[0036] In the second part, in order to reduce coal consumption during low-load peak regulation of the thermal power unit, the hot water tank releases high-load heat into the circulation in an orderly manner: the second control valve (18) and the third control valve (19) are in the open state, the first control valve (14) and the fourth control valve (23) are in the closed state, and the hot water tank (16) releases heat. Condensate flows from the second outlet of the first diverter (5) through the third control valve (19) and the water inlet pump of the cold water tank (21) into the cold water tank (21). The outlet fluid of the hot water tank (16) flows through the hot water tank outlet pump (17) and the second control valve (18) and is mixed with the water at the first inlet of the second mixer (9) through the second inlet of the second mixer (9) and continues to absorb heat.

[0037] Furthermore, in order to fully combine the unit operating status and boundaries and give full play to the advantages of the present invention, the following three points should also be considered during the specific implementation process:

[0038] 1. When the thermal power unit is in low-load peak-shaving operation, during the heat release process of the hot water tank (16), the outlet fluid of the hot water tank (16) is not limited to the heat release position, but can flow into the corresponding position according to the temperature of the heat recovery heaters at each level and the temperature of the hot fluid in the hot water tank (16). By predicting the low-load peak-shaving operation time and high-load operation time of the unit and the current heat storage capacity of the hot water tank (16), the high-load heat storage flow rate and the low-load heat release flow rate of the hot water tank (16) are allocated to ensure that the cross-load reforming steam-water process can compensate for the high-load coal consumption increase value with the low-load coal consumption reduction value within the corresponding time and obtain the maximum cumulative benefit.

[0039] 2. The cold fluid heated by the steam-water heat exchanger (3) can come from inside or outside the cycle, forming different cross-load internal heat storage and release systems and operating modes. When the cold fluid heated by the steam-water heat exchanger (3) comes from the inside of the cycle, such as the cold water tank (21), the outlet water of a certain stage heater, etc., during the system integration process, a regenerative heater can be added to compensate for the efficiency drop caused by the heat storage process and reuse the drain heat storage, or the regenerative heater drain heat storage is directly used to maintain the number of regenerative heating stages, both of which can realize the cross-load internal steam-water process reconstruction of the thermal power unit containing the hot water tank (16) heat storage process; when the cold fluid heated by the steam-water heat exchanger (3) comes from the outside of the cycle, when the cold fluid is the heat network return water, the heat of the hot water tank (16) is transferred between high load and low load, and can realize the cascade utilization and cross-load internal utilization of the exothermic steam with the help of the external heat load, or can be the condensate, feed water, and drain of the adjacent high back pressure unit. At this time, a steam-water heat exchanger (3) can be set to further heat or the steam-water heat exchanger (3) can be directly heated into the heat storage tank without being set to realize the heat transfer across the units, and the cross-unit heat storage and release process is completed according to the coal consumption loss of the high back pressure unit and the coal consumption benefit of the pure condensing unit. In deep peak regulation, the benefits of the former are more obvious. The hot fluid of the steam-water heat exchanger (3) can come from the inside of the cycle, such as the steam extraction and drainage of the steam turbine (2), and the hot fluid of the steam-water heat exchanger (3) can come from the outside of the cycle, such as boiler flue gas, industrial waste heat, steam or drainage of adjacent units, etc. Moreover, the cold fluid and the hot fluid are not limited to one source. Multiple cold fluids can come from the inside and outside of the cycle to directly store heat, absorb heat separately, or absorb heat after mixing in accordance with water quality requirements, and multiple hot fluids can come from the inside and outside of the cycle to provide heat. According to the operating status, hot fluids from different sources can heat the cold fluid in stages according to temperature matching at the same time, or hot fluids from different sources can heat the cold fluid separately at different time periods, and then the cold fluid obtains heat and enters the hot water tank (16) for storage. The destination of the fluid in the hot water tank (16) is also not restricted. It can participate in heat supply or enter the heat recovery system according to demand.

[0040] 3. The system is not limited to the double-tank heat storage form. The double-tank heat storage method can avoid the impact of heat storage and release on temperature, but it increases investment and floor space. The single-tank heat storage method will face the impact of the cyclic heat storage and release method on the temperature gradient layer, which will affect the coal consumption reduction effect, but it reduces investment and floor space. Regardless of whether the cross-load steam-water process reconstruction includes an external steam-water source, the use of a temperature gradient layer heat storage tank instead of a double-tank heat storage can also achieve the same function. Figure 2 As shown in , after the cold water tank (21) and the hot water tank (16) are replaced with the thermocline heat storage tank (24), the heat storage and release processes of the cold water tank (21) and the hot water tank (16) are simply combined together, thereby reducing the volume and footprint of the heat storage tank.

[0041] In this invention, the cold fluid heated by the steam-water heat exchanger can come from either internal or external sources within the cycle, and benefits can be achieved regardless of whether an external steam-water source is included in the cross-load steam-water process reconstruction. To fully illustrate the advantages of this invention within the constraints of the aforementioned operating mode and considerations, process examples are provided for cold fluids coming from an external condensing unit, and from a cross-unit and internal condensing unit. Example profit calculations are also provided for cold fluids coming from external condensing units and internal condensing units, fully demonstrating the integration and characteristics of both internal and external heat sources.

[0042] 1. Such as Figure 3 The figure shows the flow chart of the condensing unit system combined with the heat network return water reconstruction according to the idea of ​​the present invention, with the cold fluid heated by the steam-water heat exchanger as the heat network return water from the outside of the cycle. Figure 3 The heat return water heating process of the additional heat user (25) is analyzed for a 350MW air-cooled unit. When the unit is at 100% load, 300t / h of exhaust steam is used for heating in the extraction and condensing mode. After heating, the exhaust steam itself is cooled to 80℃ and used to store heat in the hot water tank. At the same time, the heat in the hot water tank is released at the same flow rate at 30% load. The heat storage and release flow rates are 50t / h, 100t / h, and 200t / h respectively, and the operating time ratio of 100% load to 30% load is 1:1. When the heat storage and release flow rate is 50t / h, the unit's power generation coal consumption rate increases by 0.127g / kWh at 100% load, and the unit's power generation coal consumption rate decreases by 0.436g / kWh at 30% load. The relative benefit of the unit's power generation coal consumption rate is calculated based on the difference between the two values, which is 0.309g / kWh; when the heat storage and release flow rate is 100t / h, the unit's power generation coal consumption rate increases by 0.253g / kWh at 100% load, and the unit's power generation coal consumption rate decreases by 0.860g / kWh at 30% load. The relative benefit of the unit's power generation coal consumption rate is calculated based on the difference between the two values, which is 0.606g / kWh; when the heat storage and release flow rate is 200t / h, the unit's power generation coal consumption rate increases by 0.504g / kWh at 100% load, and the unit's power generation coal consumption rate decreases by 1.666g / kWh at 30% load. The relative benefit of the unit's power generation coal consumption rate is calculated based on the difference between the two values, which is 1.161g / kWh. With the increase of heat storage and release flow rate, the benefits are obvious, and for 1000m 3 The inclined temperature layer hot water tank can run for 20 hours, 10 hours, and 5 hours respectively, with low requirements for the capacity of the heat storage tank. It can promote the access of renewable electricity to the grid and gain benefits when the unit is deeply peak-shaving. Figure 4 The figure shows a cross-unit system flow diagram of circulating external steam-water reconstruction in a cross-load internal heat storage and release system of a thermal power unit. The difference is that the heat storage fluid of the hot water tank (16) comes from the high back pressure unit diversion pipe (26), and the outlet of the cold water tank (21) is connected to the high back pressure unit mixing pipe (27).

[0043] 2. Such as Figure 5The figure shows a schematic diagram of the system flow of a pure condensing unit with internal steam-water reconstructed in a cross-load internal heat storage and release system of a thermal power unit. The second diverter (28) introduces part of the water after a certain stage of heater into the heat storage tank for heat storage. Since the low-pressure and high-pressure heaters use steam extracted from the steam turbine to heat water, the above-mentioned steam-water heat exchanger can be selected to exist or not, and the source and destination of the stored water are not limited to any location. The above-mentioned calculation of the cold fluid heated by the steam-water heat exchanger is external to the cycle. Next, the calculation of the cold fluid from the internal cycle is carried out to reorganize the system steam-water flow. Similarly, a 350MW air-cooled unit example is analyzed in a pure condensing operation mode. Using the drain water from the outlet of the No. 6 low-pressure heater as a thermal storage source, calculations show that at 100% load, with a hot water tank heat storage flow rate of 50 t / h, the unit's coal consumption rate increases by 0.192 g / kWh. At 30% load, the hot water tank releases heat, which enters the system through the inlet of the No. 5 low-pressure heater, maintaining the same 50 t / h heat release flow rate. This reduces the unit's coal consumption rate by 0.707 g / kWh. Based on the difference between these two values, a relative gain in coal consumption rate of 0.515 g / kWh is calculated for a 1:1 operating time ratio. Reforming the steam-water process with cooling fluid from within the cycle significantly improves unit performance, but is limited by the drain water flow rate.

[0044] The above schemes are only exemplary. For example, in the above scheme, a sloped temperature layer heat storage tank can be used instead of a double tank heat storage to achieve the same function. In the optimization scheme of the pure condensing unit, an additional heat exchanger can be added to reduce the negative impact of high load efficiency reduction and used for cascade heat storage to avoid the constraints of drain flow on the operating mode. Other schemes that meet the needs of the power plant can be extended according to the actual status of the power plant.

[0045] Furthermore, during operation, the above-mentioned cold fluid and hot fluid are not limited to a single source. Multiple cold fluids can come from the inside or outside of the cycle to directly store heat, absorb heat separately, or absorb heat after mixing in accordance with water quality requirements. Multiple hot fluids can come from the inside or outside of the cycle to provide heat. Depending on the operating state, hot fluids from different sources can heat the cold fluid in stages according to temperature matching at the same time, or hot fluids from different sources can heat the cold fluid separately at different time periods. After that, the cold fluid obtains heat and enters the hot water tank (16) for storage. The destination of the fluid in the hot water tank (16) is also not restricted. It can participate in heat supply or enter the heat recovery system according to demand.

[0046] The present invention proposes a system and operating method for utilizing a heat storage tank to achieve cross-load optimization and reduce overall coal consumption. The hot water tank can store heat when the unit is under high load. At this time, the unit sacrifices some efficiency for the heat storage process of the hot water tank, and the unit's high-load power generation coal consumption rate increases. When the unit is under low load, the hot water tank releases heat back into the cycle. Due to the cross-load exhaust steam extraction effect and the increase in feed water temperature, the unit efficiency increases and the power generation coal consumption rate decreases. Overall, by sacrificing the high-load power generation coal consumption rate and increasing the low-load power generation coal consumption rate to compensate for the reduction in the high-load power generation coal consumption rate, the unit's total coal consumption is reduced with a small-capacity heat storage tank, and the heat storage process can be further optimized under high load by utilizing the condensate cascade heat exchange at the outlet of a certain heater stage. It is not limited to the form of heat storage tanks. It is divided into external optimization and internal cross-load steam-water process reformation. For example, a 350MW unit is calculated. In the extraction condensing operation mode, the heat storage and release rate is 100t / h as the boundary. When the operation time ratio of 100% load and 30% load units is 1:1, the power generation coal consumption rate can be reduced by 0.606g / kWh. It only takes 1000m3 to achieve a 10-hour heat storage and release process. 3 Hot water tank. And the reduction value of power generation coal consumption rate will show a trend of nearly multiple increase with the increase of heat storage and release flow rate. The heat storage and release flow rate is doubled to 200t / h, the operation time ratio remains unchanged, and the power generation coal consumption rate can be comprehensively reduced by 1.161g / kWh. In pure condensing operation mode, the heat storage tank is used to restructure the steam-water process under different loads across loads. The heat storage and release flow rate is 50t / h. According to the difference in power generation coal consumption rate at 100% load and 30% load, the relative benefit of the power generation coal consumption rate is calculated to be 0.515g / kWh. A cross-load internal heat storage and release system and operation method for thermal power generation units. The system utilizes a heat storage tank to realize the integration of the thermal power generation unit and the heat storage tank, the internal transfer of heat across loads, and the reconstruction of the steam-water process for squeezed utilization, which has great energy-saving advantages during deep peak regulation.

[0047] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A thermal power unit cross-load internal heat storage and release system, characterized in that: The system comprises a boiler (1), a steam turbine (2), a steam-water heat exchanger (3), a condenser (4), a first diverter (5), a condensate pump (6), a condensate booster pump (7), a first mixer (8), a second mixer (9), a low-pressure heater (10), a deaerator (11), a feedwater pump (12), a high-pressure heater (13), a first control valve (14), a cold fluid source (15), a hot water tank (16), a hot tank outlet pump (17), a second control valve (18), a third control valve (19), a cold tank inlet pump (20), a cold water tank (21), a cold tank outlet pump (22), and a fourth control valve (23); The outlet of the boiler (1) is connected to the inlet of the steam turbine (2), the steam extraction port of the steam turbine (2) is connected to the hot fluid inlet of the steam-water heat exchanger (3), the outlet of the steam turbine (2) is connected to the inlet of the condenser (4), the outlet of the condenser (4) is connected to the inlet of the first diverter (5), the first outlet of the first diverter (5) is connected to the inlet of the condensate pump (6), the outlet of the condensate pump (6) is connected to the inlet of the condensate booster pump (7), and the outlet of the condensate booster pump (7) is connected to the inlet of the first diverter (5). A first inlet of a mixer (8), an outlet of the first mixer (8) is connected to a first inlet of the second mixer (9), an outlet of the second mixer (9) is connected to an inlet of the low-pressure heater (10), an outlet of the low-pressure heater (10) is connected to an inlet of the deaerator (11), an outlet of the deaerator (11) is connected to an inlet of the feedwater pump (12), an outlet of the feedwater pump (12) is connected to an inlet of the high-pressure heater (13), and an outlet of the high-pressure heater (13) is connected to the boiler (1); The hot fluid inlet of the steam-water heat exchanger (3) is connected to the steam extraction port of the steam turbine (2), the hot fluid outlet of the steam-water heat exchanger (3) is connected to the inlet of the first control valve (14), and the cold fluid inlet of the steam-water heat exchanger (3) is connected to the cold fluid source (15); The inlet of the hot water tank (16) is connected to the outlet of the first control valve (14), the outlet of the hot water tank (16) is connected to the inlet of the hot water tank outlet pump (17), the outlet of the hot water tank outlet pump (17) is connected to the inlet of the second control valve (18), and the outlet of the second control valve (18) is connected to the second inlet of the second mixer (9); the second outlet of the first diverter (5) is connected to the inlet of the third control valve (19), the outlet of the third control valve (19) is connected to the inlet of the cold water tank inlet pump (20), the outlet of the cold water tank inlet pump (20) is connected to the inlet of the cold water tank (21), the outlet of the cold water tank (21) is connected to the inlet of the cold water tank outlet pump (22), the outlet of the cold water tank outlet pump (22) is connected to the inlet of the fourth control valve (23), and the outlet of the fourth control valve (23) is connected to the second inlet of the first mixer (8).

2. A method for operating the cross-load internal heat storage and release system of a thermal power unit according to claim 1, characterized in that: The method comprises: The steam from the outlet of the boiler (1) enters the steam turbine (2) and is divided into two streams in the steam turbine (2). The first stream of steam, after doing part of the work, enters the hot fluid inlet of the steam-water heat exchanger (3) from the steam extraction port of the steam turbine (2) to exchange heat. The second stream of steam, after doing the work of the steam turbine (2), becomes low-pressure steam and enters the condenser (4) from the inlet of the steam turbine (2) to be cooled into condensate and flows into the first diverter (5) to be divided into two streams. The second stream of steam at the outlet of the first diverter (5) flows into the third control valve (19) and enters The first stream of water at the outlet of the first diverter (5) flows out from the first outlet of the first diverter (5), passes through the condensate pump (6) and the condensate booster pump (7), and then flows into the first mixer (8) from the first inlet of the first mixer (8), and flows into the second mixer (9) from the first inlet of the second mixer (9), and flows into the low-pressure heater (10) from the outlet of the second mixer (9), and then flows through the deaerator (11), the feed water pump (12), and the high-pressure heater (13) in sequence and enters the boiler (1); In order to realize that the heat storage tank transfers the heat of the high-load unit to the low-load unit for utilization, the thermal power unit uses internal heat to supplement the heat of the hot water tank when running at high load: the first control valve (14) and the fourth control valve (23) are in the open state, the second control valve (18) and the third control valve (19) are in the closed state, and the hot water tank (16) stores heat; the steam from the steam extraction port of the steam turbine (2) enters from the hot fluid inlet of the steam-water heat exchanger (3) and, after exchanging heat in the steam-water heat exchanger (3), enters from the hot fluid outlet of the steam-water heat exchanger (3) into the first control valve (14), enters into the inlet of the hot water tank (16) through the first control valve (14) to store heat, and the fluid in the cold water tank (21) passes through the cold tank outlet pump and the fourth control valve (23), is mixed with the condensed water at the first inlet of the first mixer (8) through the second inlet, and enters the low-pressure heater (10) through the second mixer (9) to absorb heat; In order to reduce coal consumption during low-load peak regulation of the thermal power unit, the hot water tank releases high-load heat into the circulation in an orderly manner: the second control valve (18) and the third control valve (19) are in an open state, the first control valve (14) and the fourth control valve (23) are in a closed state, and the hot water tank (16) releases heat; the condensed water flows from the second outlet of the first diverter (5) through the third control valve (19) and the water inlet pump of the cold water tank (21) into the cold water tank (21); the outlet fluid of the hot water tank (16) flows through the hot water tank outlet pump (17) and the second control valve (18) in turn, and is mixed with the water at the first inlet of the second mixer (9) through the second inlet of the second mixer (9) and continues to absorb heat; During the low-load peak-shaving operation of the thermal power unit, during the heat release process of the hot water tank (16), the outlet fluid of the hot water tank (16) is not limited to the heat release position, but can flow into the corresponding position according to the temperature of the heat recovery heaters at each level and the temperature of the hot water fluid in the hot water tank (16). By predicting the low-load peak-shaving operation time and high-load operation time of the unit and the current heat storage capacity of the hot water tank (16), the high-load heat storage flow and the low-load heat release flow of the hot water tank (16) are allocated to ensure that the cross-load reforming steam-water process can make up for the high-load coal consumption increase with the low-load coal consumption reduction within the corresponding time and obtain the maximum cumulative benefit.

3. The operating method according to claim 2, characterized in that: The cold fluid heated by the steam-water heat exchanger (3) comes from the inside or outside of the cycle, and forms different cross-load internal heat storage and release systems and operating modes.

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