A coal-fired power generation system with integrated heat absorption flue gas heat storage and its operation method

Abstract

The present invention discloses a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas and its operating method, belonging to the technical field of coal-fired power generation. The coal-fired power generation system with integrated heat storage of heat-absorbing flue gas provided by the present invention, by setting a No. 1 flue gas-molten salt heat exchanger and a No. 2 flue gas-molten salt heat exchanger in the boiler tail flue, fully utilizes the abundant flue gas heat in the boiler tail flue to heat the molten salt, thereby improving energy utilization efficiency. Compared with the existing technology, it breaks the traditional limitation of molten salt heating temperature, abandons the multi-stage heat transfer mode, reduces heat loss during the heat transfer process, and thus improves 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 controlled 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.

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 absorption and flue gas heat storage and an operation method thereof. Background Art

[0002] Against the backdrop of a global energy transition, my country's energy sector is undergoing an unprecedented structural transformation. The core of this transformation lies in the gradual shift from a traditional coal-dependent energy structure to a new power system dominated by renewable energy sources such as wind and solar. This transformation is aimed not only at addressing environmental pressures and resource depletion, but also at promoting sustainable economic and social development. However, the intermittent and volatile nature of renewable energy poses significant challenges for its large-scale grid integration. While traditional coal-fired power generation units can, to a certain extent, ensure the safe and stable operation of the power grid through their regulation capabilities, as the proportion of renewable energy continues to increase, their regulation capabilities are no longer sufficient to meet the growing demand for grid integration. Therefore, further improving the power generation flexibility of coal-fired units is key to promoting the integration of renewable energy into the power grid.

[0003] Integrating a molten salt heat storage system into a traditional coal-fired unit is an important means of improving the operational flexibility of coal-fired units. Through the heat storage and release of the molten salt heat storage system, it is possible to achieve "peak shifting and valley filling" of energy. 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, which limits the heating temperature of the molten salt. On the other hand, during the steam heating of the molten salt, there is a flue gas-steam-molten salt heat exchange process, and the increased 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, making it difficult to maintain the flue gas temperature at the inlet of the SCR device in 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 purpose of the present invention is to provide a coal-fired power generation system and its operation method that integrates heat absorption and flue gas heat storage, so as to overcome the problems of limited molten salt heating temperature, large heat transfer loss and poor denitrification efficiency in existing coal-fired power generation systems.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] The present invention provides a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas, comprising a boiler thermal system, a molten salt heat storage system and a flue gas recirculation system; the boiler thermal system comprises 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 provided in 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 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 is used to adjust the flow rate of unheated flue gas flowing into the SCR denitrification device; a No. 4 flue gas damper and a No. 2 flue gas-molten salt heat exchanger are sequentially provided on the other side along the flue gas flow direction of the boiler, and the No. 4 flue gas damper is used to adjust the flow rate of flue gas flowing into the SCR denitrification device after being heated by the No. 2 flue gas-molten salt heat exchanger;

[0008] 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 medium outlet of the molten salt heat storage system is connected to the low-temperature molten salt inlet;

[0009] 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.

[0010] The present invention is further improved in 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 in sequence through the low-temperature molten salt pump and the No. 1 flue gas-molten salt heat exchanger, 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 through the No. 1 molten salt control valve and the molten salt tank. -The first route is connected to the molten salt working medium inlet of the feed water heat exchanger, the second route 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 route 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-feed water 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-feed water heat exchanger is merged with the water working medium outlet of the economizer and then fed into the water-cooled wall of the boiler.

[0011] 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 routes, one route is connected to the water working medium inlet of the economizer through the No. 1 feed water control valve, and the other route is connected to the water working medium inlet of the molten salt-feed water heat exchanger through the No. 2 feed water control valve.

[0012] 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.

[0013] A further improvement of the present invention is that heat exchangers are provided inside the first parallel partitioned flue and the second parallel partitioned flue.

[0014] A further improvement of the present invention is that the cross-sectional areas of the first parallel partitioned flue and the second parallel partitioned flue are set according to the heat exchange power ratio of their respective heat exchangers.

[0015] The present invention also provides an operation method of a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas, which adopts 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;

[0016] When the coal-fired power generation system is in heat storage mode, the No. 1 flue gas-molten salt heat exchanger is used to heat the low-temperature molten salt from the molten salt heat storage system. 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 opening of the No. 1 flue gas damper and the No. 2 flue gas damper, respectively, to reduce the desuperheating water flow rate of the main steam and reheat steam.

[0017] 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. By adjusting the molten salt working medium flow of the molten salt heat storage system, the feed water temperature entering the water-cooled wall of the boiler is adjusted. By adjusting the opening of the No. 4 flue gas damper, the flue gas flow heated by the No. 2 flue gas-molten salt heat exchanger and flowing into the SCR denitrification device is adjusted. By adjusting the opening of the No. 3 flue gas damper, the unheated flue gas flow flowing into the SCR denitrification device is adjusted. 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 operating temperature range.

[0018] 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 pipe to avoid the risk of overheating of the No. 1 flue gas-molten salt heat exchanger and decomposition of the molten salt.

[0019] A further improvement of the present invention is that the operating temperature range of the SCR denitration device is 300°C to 400°C.

[0020] A further improvement of the present invention is that the outlet water temperature of the economizer is 260°C to 280°C.

[0021] A further improvement of the present invention is that the heat storage mode and the heat release mode can be performed simultaneously.

[0022] Compared with the prior art, the present invention has the following positive effects:

[0023] The coal-fired power generation system with integrated heat storage of heat-absorbing 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 No. 1 flue gas-molten salt heat exchanger and 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 existing technology, it breaks the traditional limitation of the molten salt heating temperature, abandons the multi-stage heat transfer mode, reduces the heat loss in the heat transfer process, and thus improves the overall thermal efficiency; based on the synergistic effect of the flue gas recirculation system and the molten salt heat storage system, by flexibly adjusting the flue gas temperature entering the SCR denitrification device, it is ensured 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.

[0024] 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.

[0025] Furthermore, the provision of high-temperature superheaters and high-temperature reheaters ensures the temperature levels 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.

[0026] Furthermore, setting the flue's cross-sectional area based on the heat exchanger's heat transfer power ratio helps achieve uniform distribution of flue gas within the flue. When flue gas flows evenly through the heat exchanger, it ensures uniform heating of all parts of the heat exchanger, reducing the occurrence of thermal deviations. This improves the heat exchanger's service life and reliability by preventing damage caused by local overheating. Uniform heating also helps improve the heat exchange efficiency and heat recovery rate of the heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary 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.

[0028] Figure 1 This is a schematic structural diagram of a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to the present invention;

[0029] 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

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only 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 herein can be arranged and designed in various different configurations.

[0031] 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 as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0032] 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, it does not need to be further defined or explained in subsequent drawings.

[0033] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0034] Furthermore, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be interpreted broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, which are intended to explain the present invention rather than to limit it.

[0036] A coal-fired power generation system with integrated heat absorption flue gas heat storage, including a boiler thermal system, a molten salt heat storage system and a flue gas recirculation system; the boiler thermal system includes 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 is used to adjust the main steam temperature of the low-temperature superheater 7, and a No. 1 flue gas damper 5 is 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. 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. The No. 3 flue gas damper 10 is used to adjust the flow rate of unheated flue gas flowing into the SCR denitrification 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. The No. 4 flue gas damper 11 is used to adjust the flow rate of flue gas flowing into the SCR denitrification device 13 after being heated by the No. 2 flue gas-molten salt heat exchanger 12.

[0037] 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;

[0038] 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 through the flue gas recirculation fan 18 and the flue gas recirculation pipe 24.

[0039] The coal-fired power generation system with integrated heat storage of heat-absorbing 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 No. 1 flue gas-molten salt heat exchanger and 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 existing technology, it breaks the traditional limitation of the molten salt heating temperature, abandons the multi-stage heat transfer mode, reduces the heat loss in the heat transfer process, and thus improves the overall thermal efficiency; based on the synergistic effect of the flue gas recirculation system and the molten salt heat storage system, by flexibly adjusting the flue gas temperature entering the SCR denitrification device, it is ensured 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.

[0040] 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 through 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 and the The molten salt-feed water heat exchanger 23 is connected to the molten salt working medium inlet, 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.

[0041] 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 working medium inlet of the economizer 9 through the No. 1 feed water control valve 21, and the other route is connected to the water working medium inlet of the molten salt-feed water heat exchanger 23 through the No. 2 feed water control valve 22.

[0042] The configuration of feedwater control valves No. 1 and No. 2 allows the system to flexibly adjust feedwater distribution based on operational requirements and load changes, enabling the system to better adapt to varying operating conditions and load demands. Furthermore, by precisely controlling feedwater distribution and preheating temperature, the boiler's thermal efficiency and operational performance can be further optimized. For example, in the molten salt heat storage system's heat release mode, the water flow through feedwater control valve No. 2 22 can be increased to fully utilize the heat released by the high-temperature molten salt. In heat storage mode, this water flow can be reduced to avoid unnecessary interference with the molten salt heat storage process.

[0043] Specifically, the boiler thermal system also includes a high-temperature superheater 2 and a high-temperature reheater 3 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.

[0044] 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.

[0045] Specifically, heat exchangers are provided inside the first parallel partitioned flue and the second parallel partitioned flue.

[0046] Specifically, the cross-sectional areas of the first parallel partitioned flue and the second parallel partitioned flue are set according to the heat exchange power ratio of their respective heat exchangers.

[0047] The cross-sectional area determines the achievable heat exchange power, so its cross-sectional area is set according to the heat exchange power ratio of each heat exchanger. Setting the flue cross-sectional area based on the heat exchange power ratio of the heat exchanger helps to achieve uniform distribution of flue gas within 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, reducing the occurrence of thermal deviation, thereby increasing the service life and reliability of the heat exchanger by avoiding damage to the heat exchanger due to local overheating. At the same time, uniform heating also helps to improve the heat exchange efficiency and heat recovery rate of the heat exchanger.

[0048] Based on the same inventive concept, the present invention also provides an operating method of a coal-fired power generation system with integrated heat storage of heat from 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;

[0049] When the coal-fired power generation system is in heat storage mode, the No. 1 flue gas-molten salt heat exchanger 4 is used to heat the low-temperature molten salt from the molten salt heat storage system. 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 openings of the No. 1 flue gas damper 5 and the No. 2 flue gas damper 6, respectively, to reduce the desuperheating water flow rate of the main steam and reheat steam.

[0050] 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;

[0051] 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 4. 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 pipe 24 to avoid the risk of overheating of the No. 1 flue gas-molten salt heat exchanger 4 and decomposition of the molten salt.

[0052] Specifically, the operating temperature range of the SCR denitration device 13 is 300°C to 400°C.

[0053] Specifically, the outlet water temperature of the economizer 9 is 260°C to 280°C.

[0054] Specifically, the heat storage mode and the heat release mode can be performed simultaneously.

[0055] Example 1

[0056] 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;

[0057] The boiler thermal system includes a boiler 1, along the flue gas flow direction of the boiler, 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; on one side of the first parallel partition flue, 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, and on the other side, 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 one side of the second parallel partition flue, a No. 3 flue gas damper 10 is arranged along the flue gas flow direction of the boiler, and on the other side, 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;

[0058] 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 through 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 through 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 fed into the water-cooled wall of the boiler 1;

[0059] 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 through the flue gas recirculation fan 18 and the flue gas recirculation pipe 24.

[0060] 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 it 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 passed through the molten salt-feed water heat exchanger to preheat the boiler feed water, which not only improves the operating safety of the boiler and heat storage system, but also ensures the efficient denitrification of the SCR device under wide load conditions.

[0061] Example 2

[0062] An operating method of a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas, using the coal-fired power generation system described in Example 1, wherein the coal-fired power generation system includes a heat storage mode, a heat release mode, and a heat preservation mode;

[0063] 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 of the low-temperature molten salt pump 15. The main steam temperature of the low-temperature superheater 7 and the reheated 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, to reduce the cooling water flow of the main steam and reheated steam, thereby achieving energy saving. The reheated steam of the low-temperature reheater 8 comes from the high-pressure cylinder exhaust steam.

[0064] 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 of the molten salt-feed water heat exchanger 23 is adjusted by the No. 1 molten salt control valve 19, thereby adjusting the feed water temperature entering the water-cooled wall of the boiler 1. By adjusting the opening of the No. 4 flue gas damper 11, the flow of heated flue gas flowing into 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 flow of unheated flue gas 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;

[0065] When the coal-fired power generation system is in 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 through the No. 1 flue gas-molten salt heat exchanger 4. 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 pipe 24 to avoid the risk of overheating of the No. 1 flue gas-molten salt heat exchanger 4 and decomposition of molten salt.

[0066] Finally, it should be noted that the embodiments listed above are merely one or more specific manifestations of the technical solution of the present invention. Their purpose is to clearly illustrate the concept, principles, and application of the present invention through specific examples, and is in no way intended to limit the scope of protection of the present invention to these specific embodiments. In fact, the true value of this invention lies in its technical ideas and innovations, not in its form of expression or implementation.

[0067] For ordinary technicians in the relevant technical field, after thoroughly reading and understanding the technical solutions of the present invention, they are fully capable of making various forms of changes, modifications or equivalent replacements 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 modified 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.

[0068] Furthermore, with the continuous advancement and development of technology, new technical means and methods continue to emerge, providing ample room for further improvement and perfection of the present invention. Therefore, the scope of protection of the present invention should also include reasonably foreseeable improvements and extensions based on existing technologies. As long as these improvements and extensions do not deviate from the basic principles and core concepts of the present invention, they should be considered equivalent to the present invention and equally 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), and a No. 1 flue gas-molten salt heat exchanger (4), a first parallel separated flue, an economizer (9), a second parallel separated 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 separated 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) is used to adjust the reheat steam temperature of the low-temperature reheater (8); a third flue gas damper (10) is 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) is used to adjust the flow rate of unheated flue gas flowing into the SCR denitrification device (13); a fourth flue gas damper (11) and a second flue gas-molten salt heat exchanger (12) are provided in sequence along the flue gas flow direction of the boiler on the other side, the fourth flue gas damper (11) is used to adjust the flow rate of flue gas flowing into the SCR denitrification 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 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) through the flue gas recirculation fan (18) and the flue gas recirculation pipe (24); the molten salt heat storage system includes the 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), and the No. 1 molten salt The outlet of the low-temperature molten salt tank (14) is connected to the inlet of the high-temperature molten salt tank (16) through the low-temperature molten salt pump (15) and the No. 1 flue gas-molten salt heat exchanger (4). 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 is connected to the molten salt of the No. 1 molten salt control valve (19) and the molten salt of the molten salt-feed water heat exchanger (23). The first path is connected to the working medium inlet of the second flue gas-molten salt heat exchanger (12), the second path is connected to the molten salt working medium inlet of the second flue gas-molten salt heat exchanger (12) through the second molten salt control valve (20), and the third path is merged into the molten salt inlet of the first flue gas-molten salt heat exchanger (4) through the third 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 second flue gas-molten salt heat exchanger (12) and is connected to the inlet of the low-temperature molten salt tank (14); the water of the molten salt-feed water heat exchanger (23) ... The working medium outlet is combined with the water working medium outlet of the economizer (9) and then fed into the water-cooled wall of the boiler (1); 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 routes, one route is connected to the water working medium inlet of the economizer (9) through the No. 1 water supply control valve (21), and the other route 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).

2. The coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 1 is characterized in that: The boiler thermal system further includes a high-temperature superheater (2) and a high-temperature reheater (3) 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).

3. 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 provided inside the first parallel partitioned flue and the second parallel partitioned flue.

4. The coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 3 is characterized in that: The cross-sectional areas of the first parallel partitioned flue and the second parallel partitioned flue are set according to the heat exchange power ratio of their respective heat exchangers.

5. An operating 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 according to any one of claims 1 to 4 is used, 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 (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, 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). By adjusting the molten salt working medium flow 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 heated by the No. 2 flue gas-molten salt heat exchanger (12) and flowing into the SCR denitrification device (13) is adjusted. By adjusting the opening of the No. 3 flue gas damper (10), the unheated flue gas flow 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 through 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 pipe (24) to avoid the risk of overheating of the No. 1 flue gas-molten salt heat exchanger (4) and decomposition of the molten salt.

6. The method for operating a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 5, characterized in that: The operating temperature range of the SCR denitrification device (13) is 300°C to 400°C.

7. The method for operating a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 5, characterized in that: The outlet water temperature of the economizer (9) is 260℃~280℃.

8. The method for operating a coal-fired power generation system with integrated heat storage of heat-absorbing flue gas according to claim 5, characterized in that: Heat storage mode and heat release mode can be carried out at the same time.

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