Coal-fired power generation system integrating heat absorption and flue gas heat storage and operation method of coal-fired power generation system

Abstract

The invention discloses a coal-fired power generation system integrating heat absorption and flue gas heat storage and an operation method of the coal-fired power generation system, and belongs to the technical field of coal-fired power generation. According to the coal-fired power generation system integrating heat absorption and flue gas heat storage, the first flue gas-fused salt heat exchanger and the second flue gas-fused salt heat exchanger are arranged in the tail flue of the boiler, rich flue gas heat in the tail flue of the boiler is fully utilized to heat fused salt, and therefore the utilization efficiency of energy is improved, and compared with the prior art, the energy utilization rate is improved. The traditional limitation of the molten salt heating temperature is broken through, a multi-stage heat transfer mode is abandoned, and the heat loss in the heat transfer process is reduced, so that the overall heat efficiency is improved; based on the synergistic effect of the flue gas recirculation system and the fused salt heat storage system, the temperature of flue gas entering the SCR denitration device is flexibly regulated and controlled, it is ensured that the flue gas is always kept within the ideal range of efficient denitration, the stability of the denitration process is enhanced, and the denitration efficiency can also be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-fired power generation, and in particular to a coal-fired power generation system integrating heat storage with heat absorption flue gas and an operation method thereof. Background Art

[0002] Against the backdrop of global energy transformation, my country's energy sector is undergoing an unprecedented structural change. The core of this change is to gradually shift from a traditional energy structure that relies on coal to a new power system dominated by renewable energy such as wind and solar energy. This transformation is not only to cope with the challenges of environmental pressure and resource depletion, but also to promote the sustainable development of the economy and society. However, the intermittent and volatile characteristics of renewable energy have brought great challenges to its large-scale grid connection. Although traditional coal-fired power generation units can ensure the safe and stable operation of the power grid through regulation functions to a certain extent, with the continuous increase in the proportion of renewable energy, their regulation capabilities have been unable to meet the growing demand for grid connection. Therefore, further improving the power generation flexibility of coal-fired units has become the key to promoting the consumption of renewable energy in the power grid.

[0003] Integrating a molten salt heat storage system into a traditional coal-fired unit is an important means to improve the operational flexibility of the coal-fired unit. Through the heat storage and release of the molten salt heat storage system, the energy can be "shifted to the peak and filled to the valley". However, the use of steam to heat the molten salt is limited by the temperature difference at the pinch point of the steam and molten salt heat transfer process, and the heating temperature of the molten salt is limited. On the other hand, in the process of steam heating the molten salt, there is a flue gas-steam-molten salt heat exchange process, and the increase in the heat transfer process causes greater irreversible losses. In addition, during the frequent and rapid load changes of the coal-fired unit, the main steam and reheat steam temperatures fluctuate greatly, and the flue gas temperature at the inlet of the SCR device is difficult to maintain within its efficient denitrification range.

[0004] Therefore, it is necessary to optimize the design of coal-fired power generation systems with integrated molten salt heat storage to obtain a more flexible system solution. Summary of the invention

[0005] The object of the present invention is to provide a coal-fired power generation system with integrated heat storage of flue gas heat and an operation method thereof, so as to overcome the problems of limited molten salt heating temperature, large heat transfer loss and poor denitrification efficiency existing in the existing coal-fired power generation system.

[0006] The present invention solves the above technical problems through the following technical solutions: The present invention provides a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas, including a boiler thermal system, a molten salt heat storage system and a flue gas recirculation system; the boiler thermal system includes a boiler, and a No. 1 flue gas-molten salt heat exchanger, a first parallel partition flue, an economizer, a second parallel partition flue and an SCR denitrification device are sequentially arranged along the flue gas flow direction of the boiler; a No. 1 flue gas damper and a low-temperature superheater are sequentially arranged on one side of the first parallel partition flue along the flue gas flow direction of the boiler, the No. 1 flue gas damper is used to adjust the main steam temperature of the low-temperature superheater, and ... A No. 2 flue gas damper and a low-temperature reheater are sequentially arranged along the flue gas flow direction of the boiler, and the No. 2 flue gas damper is used to adjust the reheat steam temperature of the low-temperature reheater; a No. 3 flue gas damper is arranged along the flue gas flow direction of the boiler on one side of the second parallel partition flue, and the No. 3 flue gas damper is used to adjust the unheated flue gas flow flowing into the SCR denitration device; a No. 4 flue gas damper and a No. 2 flue gas-molten salt heat exchanger are sequentially arranged along the flue gas flow direction of the boiler on the other side, and the No. 4 flue gas damper is used to adjust the flue gas flow flowing into the SCR denitration device after being heated by the No. 2 flue gas-molten salt heat exchanger; The low-temperature molten salt outlet of the molten salt heat storage system is connected to the inlet of the No. 1 flue gas-molten salt heat exchanger, the outlet of the No. 1 flue gas-molten salt heat exchanger is connected to the high-temperature molten salt inlet of the molten salt heat storage system, the inlet of the No. 2 flue gas-molten salt heat exchanger is connected to the low-temperature molten salt outlet, the outlet of the No. 2 flue gas-molten salt heat exchanger is connected to the low-temperature molten salt inlet, and the molten salt working fluid outlet of the molten salt heat storage system is connected to the low-temperature molten salt inlet; The flue gas recirculation system includes a flue gas recirculation fan and a flue gas recirculation duct; the tail flue of the economizer is connected to the flue gas inlet of the No. 1 flue gas-molten salt heat exchanger through the flue gas recirculation fan and the flue gas recirculation duct.

[0007] A further improvement of the present invention is that the molten salt heat storage system includes a No. 2 flue gas-molten salt heat exchanger, a low-temperature molten salt tank, a low-temperature molten salt pump, a high-temperature molten salt tank, a high-temperature molten salt pump, a No. 1 molten salt control valve, a No. 2 molten salt control valve, a molten salt-feed water heat exchanger and a No. 3 molten salt control valve; the outlet of the low-temperature molten salt tank is connected to the inlet of the high-temperature molten salt tank via the low-temperature molten salt pump and the No. 1 flue gas-molten salt heat exchanger in sequence, and the outlet of the high-temperature molten salt tank is divided into three paths after passing through the high-temperature molten salt pump. The first path is connected to the molten salt tank via the No. 1 molten salt control valve. -The first path is connected to the molten salt working medium inlet of the No. 2 flue gas-molten salt heat exchanger through the No. 2 molten salt control valve, the second path is connected to the molten salt working medium inlet of the No. 2 flue gas-molten salt heat exchanger through the No. 2 molten salt control valve, the third path is merged into the molten salt inlet of the No. 1 flue gas-molten salt heat exchanger through the No. 3 molten salt control valve, the molten salt working medium outlet of the molten salt-feedwater heat exchanger is merged with the molten salt working medium outlet of the No. 2 flue gas-molten salt heat exchanger and then connected to the inlet of the low-temperature molten salt tank; the water working medium outlet of the molten salt-feedwater heat exchanger is merged with the water working medium outlet of the economizer and then sent to the water-cooled wall of the boiler.

[0008] A further improvement of the present invention is that the molten salt heat storage system also includes a boiler feed water device, a No. 1 feed water control valve and a No. 2 feed water control valve. The boiler feed water device is divided into two paths, one path is connected to the water working medium inlet of the economizer through the No. 1 feed water control valve, and the other path is connected to the water working medium inlet of the molten salt-feed water heat exchanger through the No. 2 feed water control valve.

[0009] A further improvement of the present invention is that the boiler thermal system also includes a high-temperature superheater and a high-temperature reheater arranged in sequence along the flue gas flow direction of the boiler, and the high-temperature reheater is connected to the No. 1 flue gas-molten salt heat exchanger.

[0010] A further improvement of the present invention is that heat exchangers are arranged inside the first parallel partitioned flue and the second parallel partitioned flue.

[0011] A further improvement of the present invention is that the cross-sectional areas of the first parallel partitioned flues and the second parallel partitioned flues are set according to the heat exchange power ratio of their respective heat exchangers.

[0012] The present invention also provides an operation method of a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas, using the above-mentioned coal-fired power generation system, wherein the coal-fired power generation system includes a heat storage mode, a heat release mode and a heat preservation mode; When the coal-fired power generation system is in the heat storage mode, the low-temperature molten salt from the molten salt heat storage system is heated by using the No. 1 flue gas-molten salt heat exchanger, and the flue gas temperature flowing through the No. 1 flue gas-molten salt heat exchanger is adjusted by adjusting the molten salt flow rate. The main steam temperature of the low-temperature superheater and the reheat steam temperature of the low-temperature reheater are adjusted by adjusting the openings of the No. 1 flue gas damper and the No. 2 flue gas damper, respectively, to reduce the cooling water flow of the main steam and the reheat steam; When the coal-fired power generation system is in the heat release mode, the high-temperature molten salt from the molten salt heat storage system is used to heat the flue gas in the boiler feed water bypass and in front of the SCR denitrification device. The feed water temperature entering the water-cooled wall of the boiler is adjusted by adjusting the molten salt working medium flow rate of the molten salt heat storage system. The flue gas flow rate flowing into the SCR denitrification device after being heated by the No. 2 flue gas-molten salt heat exchanger is adjusted by adjusting the opening of the No. 4 flue gas damper. The unheated flue gas flow rate flowing into the SCR denitrification device is adjusted by adjusting the opening of the No. 3 flue gas damper. The flue gas heated by the No. 2 flue gas-molten salt heat exchanger and the unheated flue gas flowing through the No. 3 flue gas damper are mixed so that the flue gas temperature entering the SCR denitrification device meets the SCR denitrification working temperature range. When the coal-fired power generation system is in insulation mode, the high-temperature molten salt of the molten salt heat storage system is insulated by the No. 1 flue gas-molten salt heat exchanger. At the same time, the flue gas recirculation system is started, the flue gas recirculation fan is turned on, and the inlet flue gas temperature of the No. 1 flue gas-molten salt heat exchanger is adjusted by controlling the flue gas flow in the flue gas recirculation pipeline to avoid the risk of overheating of the No. 1 flue gas-molten salt heat exchanger and decomposition of the molten salt.

[0013] A further improvement of the present invention is that the operating temperature range of the SCR denitration device is 300°C to 400°C.

[0014] A further improvement of the present invention is that the outlet water temperature of the economizer is 260°C to 280°C.

[0015] A further improvement of the present invention is that the heat storage mode and the heat release mode can be performed simultaneously.

[0016] Compared with the prior art, the positive and progressive effects of the present invention are: The coal-fired power generation system with integrated heat storage by absorbing heat from flue gas provided by the present invention integrates a molten salt heat storage system that directly absorbs heat from flue gas for heat storage, reduces the heat energy loss caused by multi-stage heat exchange in traditional coal-fired power generation systems, and improves the energy utilization efficiency of the overall system. Specifically, by arranging a No. 1 flue gas-molten salt heat exchanger and a No. 2 flue gas-molten salt heat exchanger in the boiler tail flue, the abundant flue gas heat in the boiler tail flue is fully utilized to heat the molten salt, thereby improving the energy utilization efficiency. Compared with the prior art, the traditional limitation of the molten salt heating temperature is broken, the multi-stage heat transfer mode is abandoned, and the heat loss in the heat transfer process is reduced, thereby improving the overall thermal efficiency. Based on the synergistic effect of the flue gas recirculation system and the molten salt heat storage system, the flue gas temperature entering the SCR denitrification device is flexibly adjusted to ensure that it is always maintained within the ideal range of high-efficiency denitrification, which not only enhances the stability of the denitrification process but also improves the denitrification efficiency.

[0017] Furthermore, the setting of feed water control valve No. 1 and feed water control valve No. 2 allows the system to flexibly adjust the distribution of feed water according to operating requirements and load changes, so that the system can better adapt to different operating conditions and load requirements; at the same time, by precisely controlling the distribution and preheating temperature of feed water, the thermal efficiency and operating performance of the boiler can be further optimized.

[0018] Furthermore, the provision of a high-temperature superheater and a high-temperature reheater ensures the temperature levels of the main steam and the reheated steam, which is beneficial to improving the working capacity of the steam, thereby improving the power generation efficiency of the system.

[0019] Furthermore, setting the cross-sectional area of ​​the flue according to the heat exchange power ratio of the heat exchanger helps to achieve uniform distribution of the flue gas in the flue. When the flue gas flows evenly through the heat exchanger, it can ensure that all parts of the heat exchanger are heated evenly, reduce the occurrence of thermal deviation, and thus improve the service life and reliability of the heat exchanger, because it can avoid damage to the heat exchanger caused by local overheating. At the same time, uniform heating also helps to improve the heat exchange efficiency and heat recovery rate of the heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0021] Figure 1 This is a schematic diagram of the structure of a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to the present invention; Among them, boiler-1; high-temperature superheater-2; high-temperature reheater-3; No. 1 flue gas-molten salt heat exchanger-4; No. 1 flue gas damper-5; No. 2 flue gas damper-6; low-temperature superheater-7; low-temperature reheater-8; economizer-9; No. 3 flue gas damper-10; No. 4 flue gas damper-11; No. 2 flue gas-molten salt heat exchanger-12; SCR denitrification device-13; low-temperature molten salt tank-14; low-temperature molten salt pump-15; high-temperature molten salt tank-16; high-temperature molten salt pump-17; No. 1 molten salt control valve-19; No. 2 molten salt control valve-20; No. 1 feed water control valve-21; No. 2 feed water control valve-22; molten salt-feed water heat exchanger-23; flue gas recirculation pipeline-24; No. 3 molten salt control valve-25. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0025] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0026] In addition, it should be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, which are intended to explain the present invention rather than to limit it.

[0028] A coal-fired power generation system with integrated heat storage of heat-absorbing flue gas comprises a boiler thermal system, a molten salt heat storage system and a flue gas recirculation system; the boiler thermal system comprises a boiler 1, and a No. 1 flue gas-molten salt heat exchanger 4, a first parallel partition flue, an economizer 9, a second parallel partition flue and an SCR denitrification device 13 are sequentially arranged along the flue gas flow direction of the boiler 1; a No. 1 flue gas damper 5 and a low-temperature superheater 7 are sequentially arranged on one side of the first parallel partition flue along the flue gas flow direction of the boiler, the No. 1 flue gas damper 5 is used to adjust the main steam temperature of the low-temperature superheater 7, and a No. 1 flue gas damper 5 and a low-temperature superheater 7 are sequentially arranged on the other side along the flue gas flow direction of the boiler A No. 2 flue gas damper 6 and a low-temperature reheater 8 are provided, and the No. 2 flue gas damper 6 is used to adjust the reheat steam temperature of the low-temperature reheater 8; a No. 3 flue gas damper 10 is provided on one side of the second parallel partition flue along the flue gas flow direction of the boiler, and the No. 3 flue gas damper 10 is used to adjust the flow rate of unheated flue gas flowing into the SCR denitration device 13; a No. 4 flue gas damper 11 and a No. 2 flue gas-molten salt heat exchanger 12 are provided in sequence along the flue gas flow direction of the boiler on the other side, and the No. 4 flue gas damper 11 is used to adjust the flow rate of flue gas flowing into the SCR denitration device 13 after being heated by the No. 2 flue gas-molten salt heat exchanger 12; The low-temperature molten salt outlet of the molten salt heat storage system is connected to the inlet of the No. 1 flue gas-molten salt heat exchanger 4, the outlet of the No. 1 flue gas-molten salt heat exchanger 4 is connected to the high-temperature molten salt inlet of the molten salt heat storage system, the inlet of the No. 2 flue gas-molten salt heat exchanger 12 is connected to the low-temperature molten salt outlet, the outlet of the No. 2 flue gas-molten salt heat exchanger 12 is connected to the low-temperature molten salt inlet, and the molten salt working fluid outlet of the molten salt heat storage system is connected to the low-temperature molten salt inlet; The flue gas recirculation system includes a flue gas recirculation fan 18 and a flue gas recirculation pipe 24; the tail flue of the economizer 9 is connected to the flue gas inlet of the No. 1 flue gas-molten salt heat exchanger 4 via the flue gas recirculation fan 18 and the flue gas recirculation pipe 24.

[0029] The coal-fired power generation system with integrated heat storage by absorbing heat from flue gas provided by the present invention integrates a molten salt heat storage system that directly absorbs heat from flue gas for heat storage, reduces the heat energy loss caused by multi-stage heat exchange in traditional coal-fired power generation systems, and improves the energy utilization efficiency of the overall system. Specifically, by arranging a No. 1 flue gas-molten salt heat exchanger and a No. 2 flue gas-molten salt heat exchanger in the boiler tail flue, the abundant flue gas heat in the boiler tail flue is fully utilized to heat the molten salt, thereby improving the energy utilization efficiency. Compared with the prior art, the traditional limitation of the molten salt heating temperature is broken, the multi-stage heat transfer mode is abandoned, and the heat loss in the heat transfer process is reduced, thereby improving the overall thermal efficiency. Based on the synergistic effect of the flue gas recirculation system and the molten salt heat storage system, the flue gas temperature entering the SCR denitrification device is flexibly adjusted to ensure that it is always maintained within the ideal range of high-efficiency denitrification, which not only enhances the stability of the denitrification process but also improves the denitrification efficiency.

[0030] Specifically, the molten salt heat storage system includes a No. 2 flue gas-molten salt heat exchanger 12, a low-temperature molten salt tank 14, a low-temperature molten salt pump 15, a high-temperature molten salt tank 16, a high-temperature molten salt pump 17, a No. 1 molten salt control valve 19, a No. 2 molten salt control valve 20, a molten salt-feed water heat exchanger 23 and a No. 3 molten salt control valve 25; the outlet of the low-temperature molten salt tank 14 is connected to the inlet of the high-temperature molten salt tank 16 via the low-temperature molten salt pump 15 and the No. 1 flue gas-molten salt heat exchanger 4 in sequence, and the outlet of the high-temperature molten salt tank 16 is divided into three routes after passing through the high-temperature molten salt pump 17. The first route is connected to the No. 1 molten salt control valve 19 via the No. 2 molten salt control valve 20. The first path is connected to the molten salt working medium inlet of the molten salt-feed water heat exchanger 23, the second path is connected to the molten salt working medium inlet of the No. 2 flue gas-molten salt heat exchanger 12 through the No. 2 molten salt control valve 20, and the third path is merged into the molten salt inlet of the No. 1 flue gas-molten salt heat exchanger 4 through the No. 3 molten salt control valve 25. The molten salt working medium outlet of the molten salt-feed water heat exchanger 23 is merged with the molten salt working medium outlet of the No. 2 flue gas-molten salt heat exchanger 12 and then connected to the inlet of the low-temperature molten salt tank 14; the water working medium outlet of the molten salt-feed water heat exchanger 23 is merged with the water working medium outlet of the economizer 9 and then sent to the water-cooled wall of the boiler 1.

[0031] Specifically, the molten salt heat storage system also includes a boiler feed water device 26, a No. 1 feed water control valve 21 and a No. 2 feed water control valve 22. The boiler feed water device 26 is divided into two routes, one route is connected to the water medium inlet of the economizer 9 through the No. 1 feed water control valve 21, and the other route is connected to the water medium inlet of the molten salt-feed water heat exchanger 23 through the No. 2 feed water control valve 22.

[0032] The setting of the No. 1 feedwater control valve and the No. 2 feedwater control valve allows the system to flexibly adjust the distribution of feedwater according to the operation requirements and load changes, so that the system can better adapt to different operating conditions and load requirements; at the same time, by accurately controlling the distribution and preheating temperature of the feedwater, the thermal efficiency and operation performance of the boiler can be further optimized. For example, in the heat release mode of the molten salt heat storage system, the water supply through the No. 2 feedwater control valve 22 can be increased to make full use of the heat released by the high-temperature molten salt; while in the heat storage mode, this part of the water supply can be reduced to avoid unnecessary interference with the molten salt heat storage process.

[0033] Specifically, the boiler thermal system also includes a high-temperature superheater 2 and a high-temperature reheater 3 which are arranged in sequence along the flue gas flow direction of the boiler, and the high-temperature reheater 3 is connected to the No. 1 flue gas-molten salt heat exchanger 4.

[0034] The setting of high-temperature superheater and high-temperature reheater ensures the temperature level of main steam and reheated steam, which is beneficial to improving the work capacity of steam and thus improving the power generation efficiency of the system.

[0035] Specifically, heat exchangers are disposed inside the first parallel partitioned flue and the second parallel partitioned flue.

[0036] Specifically, the cross-sectional areas of the first parallel partitioned flues and the second parallel partitioned flues are set according to the heat exchange power ratio of their respective heat exchangers.

[0037] The cross-sectional area determines the heat exchange power that can be achieved, so its cross-sectional area is set according to the heat exchange power ratio of each heat exchanger. Setting the cross-sectional area of ​​the flue according to the heat exchange power ratio of the heat exchanger helps to achieve uniform distribution of flue gas in the flue. When the flue gas flows evenly through the heat exchanger, it can ensure that all parts of the heat exchanger are heated evenly, reduce the occurrence of thermal deviation, and thus improve the service life and reliability of the heat exchanger, because it can avoid damage to the heat exchanger caused by local overheating. At the same time, uniform heating also helps to improve the heat exchange efficiency and heat recovery rate of the heat exchanger.

[0038] Based on the same inventive concept, the present invention also provides an operation method of a coal-fired power generation system with integrated heat storage of heat absorbing flue gas, using the above-mentioned coal-fired power generation system, the coal-fired power generation system includes a heat storage mode, a heat release mode and a heat preservation mode; When the coal-fired power generation system is in the heat storage mode, the low-temperature molten salt from the molten salt heat storage system is heated by the No. 1 flue gas-molten salt heat exchanger 4, and the flue gas temperature flowing through the No. 1 flue gas-molten salt heat exchanger 4 is adjusted by adjusting the molten salt flow rate. The main steam temperature of the low-temperature superheater 7 and the reheat steam temperature of the low-temperature reheater 8 are adjusted by adjusting the opening of the No. 1 flue gas damper 5 and the No. 2 flue gas damper 6, respectively, to reduce the cooling water flow of the main steam and the reheat steam; When the coal-fired power generation system is in the heat release mode, the high-temperature molten salt from the molten salt heat storage system is used to heat the flue gas in the boiler feed water bypass and in front of the SCR denitrification device 13. The feed water temperature entering the water-cooled wall of the boiler 1 is adjusted by adjusting the molten salt working medium flow rate of the molten salt heat storage system. The flue gas flow rate flowing into the SCR denitrification device 13 after being heated by the No. 2 flue gas-molten salt heat exchanger 12 is adjusted by adjusting the opening of the No. 4 flue gas damper 11. The unheated flue gas flow rate flowing into the SCR denitrification device 13 is adjusted by adjusting the opening of the No. 3 flue gas damper 10. The flue gas heated by the No. 2 flue gas-molten salt heat exchanger 12 and the unheated flue gas flowing through the No. 3 flue gas damper 10 are mixed, so that the flue gas temperature entering the SCR denitrification device 13 meets the SCR denitrification working temperature range. When the coal-fired power generation system is in the insulation mode, the high-temperature molten salt of the molten salt heat storage system is insulated by the No. 1 flue gas-molten salt heat exchanger 4, and at the same time, the flue gas recirculation system is started, the flue gas recirculation fan 18 is turned on, and the inlet flue gas temperature of the No. 1 flue gas-molten salt heat exchanger 4 is adjusted by controlling the flue gas flow in the flue gas recirculation duct 24 to avoid the risk of overheating of the No. 1 flue gas-molten salt heat exchanger 4 and decomposition of the molten salt.

[0039] Specifically, the operating temperature range of the SCR denitration device 13 is 300°C to 400°C.

[0040] Specifically, the outlet water temperature of the economizer 9 is 260°C to 280°C.

[0041] Specifically, the heat storage mode and the heat release mode can be performed simultaneously.

[0042] Embodiment 1 See also Figure 1 , a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas, including a boiler thermal system, a molten salt heat storage system and a flue gas recirculation system; The boiler thermal system comprises a boiler 1, and a No. 1 flue gas-molten salt heat exchanger 4, a first parallel partition flue, an economizer 9, a second parallel partition flue and an SCR denitrification device 13 are sequentially arranged along the flue gas flow direction of the boiler; a No. 1 flue gas damper 5 and a low-temperature superheater 7 are sequentially arranged along the flue gas flow direction of the boiler on one side of the first parallel partition flue, and a No. 2 flue gas damper 6 and a low-temperature reheater 8 are sequentially arranged along the flue gas flow direction of the boiler on the other side; a No. 3 flue gas damper 10 is arranged along the flue gas flow direction of the boiler on one side of the second parallel partition flue, and a No. 4 flue gas damper 11 and a No. 2 flue gas-molten salt heat exchanger 12 are sequentially arranged along the flue gas flow direction of the boiler on the other side; The molten salt heat storage system includes a No. 1 flue gas-molten salt heat exchanger 4, a No. 2 flue gas-molten salt heat exchanger 12, a low-temperature molten salt tank 14, a low-temperature molten salt pump 15, a high-temperature molten salt tank 16, a high-temperature molten salt pump 17, a No. 1 molten salt control valve 19, a No. 2 molten salt control valve 20, a molten salt-feed water heat exchanger 23 and a No. 3 molten salt control valve 25; the outlet of the low-temperature molten salt tank 14 is connected to the inlet of the high-temperature molten salt tank 16 via the low-temperature molten salt pump 15 and the No. 1 flue gas-molten salt heat exchanger 4 in sequence, and the outlet of the high-temperature molten salt tank 16 is divided into three routes after passing through the high-temperature molten salt pump 17, the first route is connected to the inlet of the high-temperature molten salt tank 16 via the No. 1 molten salt control valve 20, and the outlet of the high-temperature molten salt tank 16 is connected to the inlet of the high-temperature molten salt tank 16 via the low-temperature molten salt pump 15 and the No. 1 flue gas-molten salt heat exchanger 4 in sequence, and the outlet of the high-temperature molten salt tank 16 is divided into three routes after passing through the high-temperature molten salt pump 17, and the first route is connected to the inlet of the high-temperature molten salt tank 16 via the No. 1 molten salt control valve 20. The valve 19 is connected to the molten salt working medium inlet of the molten salt-feed water heat exchanger 23, the second route is connected to the molten salt working medium inlet of the No. 2 flue gas-molten salt heat exchanger 12 through the No. 2 molten salt control valve 20, and the third route is merged into the molten salt inlet of the No. 1 flue gas-molten salt heat exchanger 4 through the No. 3 molten salt control valve 25. The molten salt working medium outlet of the molten salt-feed water heat exchanger 23 is merged with the molten salt working medium outlet of the No. 2 flue gas-molten salt heat exchanger 12 and then connected to the inlet of the low-temperature molten salt tank 14; the water working medium outlet of the molten salt-feed water heat exchanger 23 is merged with the water working medium outlet of the economizer 9 and then sent to the water-cooled wall of the boiler 1; The flue gas recirculation system includes a flue gas recirculation fan 18 and a flue gas recirculation pipe 24; the tail flue of the economizer 9 is connected to the flue gas inlet of the No. 1 flue gas-molten salt heat exchanger 4 via the flue gas recirculation fan 18 and the flue gas recirculation pipe 24.

[0043] This system integrates a molten salt heat storage system that directly absorbs the heat of flue gas for heat storage. The molten salt in the low-temperature molten salt tank is transported to the No. 1 flue gas-molten salt heat exchanger through a low-temperature molten salt pump to absorb the heat of the high-temperature flue gas generated by the boiler, thereby heating up and converting it into high-temperature molten salt, which is then sent to the high-temperature molten salt tank for storage. The molten salt is used as a heat carrier to directly absorb the heat of the flue gas, reducing the heat energy loss caused by multi-stage heat exchange in traditional coal-fired power generation systems and improving the energy utilization efficiency of the overall system. The molten salt heat storage system can efficiently store and release heat, provide a stable heat energy supply for the system, and enhance the flexibility of the system; the No. 1 flue gas- The molten salt heat exchanger and the No. 2 flue gas-molten salt heat exchanger are arranged upstream of the low-temperature superheater and the low-temperature reheater respectively. The flue gas temperature can be changed by adjusting the molten salt flow rate, and then the temperature of the main steam and reheated steam can be accurately controlled by the opening of the flue gas damper, thereby reducing the cooling water flow rate of the main steam and reheated steam, and also reducing the minimum power load rate of the system, thereby promoting the renewable energy power consumption of the power grid; a molten salt-feed water heat exchanger is provided, and the high-temperature molten salt is used to preheat the boiler feed water through the molten salt-feed water heat exchanger, which not only improves the operating safety of the boiler and the heat storage system, but also ensures the efficient denitrification of the SCR device under a wide load condition.

[0044] Embodiment 2 An operation method of a coal-fired power generation system integrating heat storage of heat from heat-absorbing flue gas, using the coal-fired power generation system described in the first embodiment, the coal-fired power generation system including a heat storage mode, a heat release mode and a heat preservation mode; When the coal-fired power generation system is in the heat storage mode, the low-temperature molten salt pump 15 is started, and the low-temperature molten salt from the low-temperature molten salt tank 14 is heated by the No. 1 flue gas-molten salt heat exchanger 4. The flue gas temperature flowing through the No. 1 flue gas-molten salt heat exchanger 4 is adjusted by adjusting the molten salt flow rate of the low-temperature molten salt pump 15. The main steam temperature of the low-temperature superheater 7 and the reheat steam temperature of the low-temperature reheater 8 are adjusted by adjusting the opening of the No. 1 flue gas damper 5 and the No. 2 flue gas damper 6, respectively, to reduce the cooling water flow of the main steam and the reheat steam, and realize energy saving. Among them, the reheat steam source of the low-temperature reheater 8 is the high-pressure cylinder exhaust steam; When the coal-fired power generation system is in the heat release mode, the high-temperature molten salt pump 17 is started, and the high-temperature molten salt from the high-temperature molten salt tank 16 is used to heat the flue gas in the boiler feed water bypass and in front of the SCR denitrification device 13. The molten salt flow rate of the molten salt-feed water heat exchanger 23 is adjusted by the No. 1 molten salt control valve 19, so as to adjust the feed water temperature entering the water-cooled wall of the boiler 1. The heated flue gas flow rate flowing into the No. 2 flue gas-molten salt heat exchanger 12 is adjusted by adjusting the opening of the No. 4 flue gas damper 11. The unheated flue gas flow rate flowing into the SCR denitrification device 13 is adjusted by adjusting the opening of the No. 3 flue gas damper 10. The flue gas heated by the No. 2 flue gas-molten salt heat exchanger 12 and the unheated flue gas flowing through the No. 3 flue gas damper 10 are mixed, so that the flue gas temperature entering the SCR denitrification device 13 meets the SCR denitrification working temperature range; When the coal-fired power generation system is in the insulation mode, the high-temperature molten salt pump 17 is started, the No. 1 molten salt control valve 19 and the No. 2 molten salt control valve 20 are closed, and the No. 3 molten salt control valve 25 is opened. The high-temperature molten salt in the high-temperature molten salt tank 16 is insulated by the No. 1 flue gas-molten salt heat exchanger 4. At the same time, the flue gas recirculation system is started, and the flue gas recirculation fan 18 is turned on. The inlet flue gas temperature of the No. 1 flue gas-molten salt heat exchanger 4 is adjusted by controlling the flue gas flow in the flue gas recirculation pipe 24 to avoid the risk of overheating of the No. 1 flue gas-molten salt heat exchanger 4 and decomposition of molten salt.

[0045] Finally, it should be noted that the above-listed embodiments exist only as one or more specific forms of expression of the technical solution of the present invention. Their purpose is to clearly explain the concept, principle and application of the present invention through specific examples, and it is by no means intended to limit the protection scope of the present invention to these specific embodiments. In fact, the real value of the present invention lies in the technical ideas and innovations it proposes, rather than its form of expression or means of implementation.

[0046] For ordinary technicians in the relevant technical field, after in-depth reading and understanding of the technical solution of the present invention, they are fully capable of making various forms of changes, modifications or equivalent substitutions to the specific implementation methods of the invention based on their own professional knowledge and skills. These changes may include but are not limited to: adjusting the value range of technical parameters, optimizing algorithm processes to improve efficiency, replacing some technical components to achieve better compatibility or reduce costs, etc. As long as these changed technical solutions still substantially maintain the technical features claimed for protection by the original invention, that is, they can still achieve the core functions and effects of the present invention, then these changes should be deemed to fall within the scope of protection of the pending claims of the present invention.

[0047] In addition, with the continuous progress and development of technology, new technical means and methods continue to emerge, which also provides broad space for further improvement and perfection of the present invention. Therefore, the protection scope of the present invention should also include those reasonably foreseeable improvements and extensions based on the existing technology. As long as these improvements and extensions do not deviate from the basic principles and core concepts of the present invention, they should be regarded as equivalents of the present invention and are also protected by patent rights.

Claims

1. A coal-fired power generation system with integrated heat storage of heat-absorbing flue gas, characterized in that: The invention comprises a boiler thermal system, a molten salt heat storage system and a flue gas recirculation system; the boiler thermal system comprises a boiler (1), wherein a No. 1 flue gas-molten salt heat exchanger (4), a first parallel partition flue, an economizer (9), a second parallel partition flue and an SCR denitration device (13) are sequentially arranged along the flue gas flow direction of the boiler (1); a No. 1 flue gas damper (5) and a low-temperature superheater (7) are sequentially arranged on one side of the first parallel partition flue along the flue gas flow direction of the boiler, wherein the No. 1 flue gas damper (5) is used to adjust the main steam temperature of the low-temperature superheater (7); and a No. 2 flue gas damper (6) and a low-temperature superheater (7) are sequentially arranged on the other side along the flue gas flow direction of the boiler. A low-temperature reheater (8), the second flue gas damper (6) being used to adjust the reheat steam temperature of the low-temperature reheater (8); a third flue gas damper (10) being provided on one side of the second parallel partition flue along the flue gas flow direction of the boiler, the third flue gas damper (10) being used to adjust the flow rate of unheated flue gas flowing into the SCR denitration device (13); a fourth flue gas damper (11) and a second flue gas-molten salt heat exchanger (12) being provided in sequence along the flue gas flow direction of the boiler, the fourth flue gas damper (11) being used to adjust the flow rate of flue gas flowing into the SCR denitration device (13) after being heated by the second flue gas-molten salt heat exchanger (12); The low-temperature molten salt outlet of the molten salt heat storage system is connected to the inlet of the No. 1 flue gas-molten salt heat exchanger (4), the outlet of the No. 1 flue gas-molten salt heat exchanger (4) is connected to the high-temperature molten salt inlet of the molten salt heat storage system, the inlet of the No. 2 flue gas-molten salt heat exchanger (12) is connected to the low-temperature molten salt outlet, the outlet of the No. 2 flue gas-molten salt heat exchanger (12) is connected to the low-temperature molten salt inlet, and the molten salt working medium outlet of the molten salt heat storage system is connected to the low-temperature molten salt inlet; The flue gas recirculation system comprises a flue gas recirculation fan (18) and a flue gas recirculation duct (24); the tail flue of the economizer (9) is connected to the flue gas inlet of the No. 1 flue gas-molten salt heat exchanger (4) via the flue gas recirculation fan (18) and the flue gas recirculation duct (24).

2. A coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 1, characterized in that: The molten salt heat storage system comprises a No. 2 flue gas-molten salt heat exchanger (12), a low-temperature molten salt tank (14), a low-temperature molten salt pump (15), a high-temperature molten salt tank (16), a high-temperature molten salt pump (17), a No. 1 molten salt control valve (19), a No. 2 molten salt control valve (20), a molten salt-feed water heat exchanger (23) and a No. 3 molten salt control valve (25); the outlet of the low-temperature molten salt tank (14) is connected to the inlet of the high-temperature molten salt tank (16) via the low-temperature molten salt pump (15) and the No. 1 flue gas-molten salt heat exchanger (4), and the outlet of the high-temperature molten salt tank (16) is divided into three paths after passing through the high-temperature molten salt pump (17). The first path passes through the No. 1 molten salt control valve (19). The first path is connected to the molten salt working medium inlet of the molten salt-feed water heat exchanger (23) through the second molten salt control valve (20), and the third path is connected to the molten salt working medium inlet of the second flue gas-molten salt heat exchanger (12) through the third molten salt control valve (25). The molten salt working medium outlet of the molten salt-feed water heat exchanger (23) is connected to the molten salt working medium outlet of the second flue gas-molten salt heat exchanger (12) and is connected to the inlet of the low-temperature molten salt tank (14). The water working medium outlet of the molten salt-feed water heat exchanger (23) is connected to the water working medium outlet of the economizer (9) and is sent to the water-cooled wall of the boiler (1).

3. A coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 2, characterized in that: The molten salt heat storage system also includes a boiler water supply device (26), a No. 1 water supply control valve (21) and a No. 2 water supply control valve (22). The boiler water supply device (26) is divided into two paths, one path is connected to the water working medium inlet of the economizer (9) through the No. 1 water supply control valve (21), and the other path is connected to the water working medium inlet of the molten salt-feed water heat exchanger (23) through the No. 2 water supply control valve (22).

4. A coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 1, characterized in that: The boiler thermal system also includes a high-temperature superheater (2) and a high-temperature reheater (3) which are arranged in sequence along the flue gas flow direction of the boiler, and the high-temperature reheater (3) is connected to the No. 1 flue gas-molten salt heat exchanger (4).

5. The coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 1 is characterized in that: Heat exchangers are disposed inside the first parallel partitioned flue and the second parallel partitioned flue.

6. A coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 5, characterized in that: The cross-sectional areas of the first parallel partition flue and the second parallel partition flue are set according to the heat exchange power ratio of their respective heat exchangers.

7. An operation method of a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas, characterized in that: A coal-fired power generation system as claimed in any one of claims 1 to 6, wherein the coal-fired power generation system comprises a heat storage mode, a heat release mode and a heat preservation mode; When the coal-fired power generation system is in the heat storage mode, the low-temperature molten salt from the molten salt heat storage system is heated by using the No. 1 flue gas-molten salt heat exchanger (4), the flue gas temperature flowing through the No. 1 flue gas-molten salt heat exchanger (4) is adjusted by adjusting the molten salt flow rate, and the main steam temperature of the low-temperature superheater (7) and the reheat steam temperature of the low-temperature reheater (8) are adjusted by adjusting the openings of the No. 1 flue gas damper (5) and the No. 2 flue gas damper (6), respectively, so as to reduce the cooling water flow rates of the main steam and the reheat steam; When the coal-fired power generation system is in the heat release mode, the high-temperature molten salt from the molten salt heat storage system is used to heat the flue gas in the boiler feed water bypass and in front of the SCR denitrification device (13). By adjusting the molten salt working medium flow rate of the molten salt heat storage system, the feed water temperature entering the water-cooled wall of the boiler (1) is adjusted. By adjusting the opening of the No. 4 flue gas damper (11), the flue gas flow rate flowing into the SCR denitrification device (13) after being heated by the No. 2 flue gas-molten salt heat exchanger (12) is adjusted. By adjusting the opening of the No. 3 flue gas damper (10), the unheated flue gas flow rate flowing into the SCR denitrification device (13) is adjusted. The flue gas heated by the No. 2 flue gas-molten salt heat exchanger (12) and the unheated flue gas flowing through the No. 3 flue gas damper (10) are mixed, so that the flue gas temperature entering the SCR denitrification device (13) meets the SCR denitrification operating temperature range. When the coal-fired power generation system is in the insulation mode, the high-temperature molten salt of the molten salt heat storage system is insulated by the No. 1 flue gas-molten salt heat exchanger (4), and at the same time, the flue gas recirculation system is started, the flue gas recirculation fan (18) is turned on, and the inlet flue gas temperature of the No. 1 flue gas-molten salt heat exchanger (4) is adjusted by controlling the flue gas flow in the flue gas recirculation duct (24) to avoid the risk of overheating of the No. 1 flue gas-molten salt heat exchanger (4) and decomposition of the molten salt.

8. The method for operating a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 7, characterized in that: The operating temperature range of the SCR denitration device (13) is 300°C to 400°C.

9. The method for operating a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 7, characterized in that: The outlet water temperature of the economizer (9) is 260°C to 280°C.

10. The method for operating a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 7, characterized in that: The heat storage mode and heat release mode can be performed simultaneously.

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