A system and operation method for coupling steam energy storage with a main engine coaxial feed water pump

Abstract

The present invention discloses a system for coupling a main engine coaxial feedwater pump with steam heat storage, comprising: a boiler for generating high-temperature and high-pressure steam; a steam turbine unit connected to the boiler, utilizing the impact force of the high-temperature and high-pressure steam to generate rotational mechanical energy, and cooperating with a generator to generate electrical energy; a steam heat storage structure connected to the boiler, for utilizing the flue gas of the boiler to heat condensed water to generate high-temperature and high-pressure steam when the boiler needs to reduce the load, and for being connected to the steam turbine unit to ensure normal water supply to the boiler when the unit is started or stopped or a fault occurs. The provision of the steam heat storage structure can utilize the flue gas of the boiler to heat and generate high-temperature and high-pressure steam when the unit load needs to be reduced, and can ensure normal water supply to the boiler when the unit is started or stopped or a fault occurs, thereby improving the energy utilization efficiency of the coal-fired unit, reducing energy loss, and improving the operational flexibility and safety of the coal-fired unit.

Description

Technical Field

[0001] The present invention relates to the technical field of peak-shaving power generation of coal-fired units, and in particular to a system and an operating method for a main engine coaxial feedwater pump coupled with steam heat storage. Background Art

[0002] The development of clean energy, such as solar, wind, and tidal energy, is an inevitable trend in future power generation. Improving the flexibility of coal-fired units is key to addressing the intermittent and unpredictable nature of renewable energy. As a key enabler of operational flexibility, thermal power plants play a vital role in enabling large-scale renewable energy generation and ensuring the safe and stable operation of the power grid during the ongoing transformation of the current power system.

[0003] Existing coal-fired units primarily use steam-driven and electric feedwater pumps for their feedwater pumps. Electric feedwater pumps have a particularly high plant consumption rate, while steam-driven feedwater pumps experience significant fluctuations in feedwater flow, both hindering the flexible and efficient operation of coal-fired units. Using a coaxial feedwater pump with the main engine offers both flexibility and efficiency, but it struggles to operate during unit startup and shutdown, during failures, or under other adverse operating conditions. Consequently, electric feedwater pumps are often deployed to replace these pumps for pressurized feedwater. This requirement for an additional electric feedwater pump and increased plant electricity consumption makes it less economical. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention designs a main engine coaxial feed water pump coupled with steam heat storage system, including: a boiler, used to generate high-temperature and high-pressure steam; a steam turbine unit, connected to the boiler, using the impact force of the high-temperature and high-pressure steam to generate rotational mechanical energy, and cooperating with the generator to generate electrical energy; a steam heat storage structure, connected to the boiler, used to use the boiler's flue gas to heat condensate to generate high-temperature and high-pressure steam when the boiler needs to reduce the load, and connected to the steam turbine unit to ensure normal boiler feed water when the unit is started or stopped or a failure occurs.

[0005] Preferably, the steam heat storage structure includes a steam heat accumulator, a small steam turbine, a condensate storage tank and a flue gas heat exchanger connected in sequence, wherein the flue gas heat exchanger is also connected to the steam heat accumulator; the flue gas heat exchanger is connected to the boiler, and is used to use the flue gas of the boiler to heat the condensate to generate high-temperature and high-pressure steam when the boiler needs to reduce the load; the small steam turbine is connected to the steam turbine unit, and is used to ensure normal water supply to the boiler when the unit is started or stopped or a failure occurs.

[0006] Preferably, the flue gas heat exchanger is a shell and tube heat exchanger that adopts countercurrent heat exchange, with the flue gas flowing on the shell side and the condensed water flowing on the tube side.

[0007] Preferably, a thermal insulation layer is provided on the outer side of the shell of the flue gas heat exchanger.

[0008] Preferably, the operating temperature range of the steam thermal storage structure is 70°Ϲ-330°Ϲ, the temperature of the water in the condensed water storage tank is fixed at 70°Ϲ, and the temperature of the high-temperature and high-pressure steam in the steam thermal accumulator is 330°Ϲ and the pressure is 27 MPa.

[0009] Preferably, the steam turbine unit includes a high-pressure cylinder, an intermediate-pressure cylinder, a low-pressure cylinder, a condenser, a low-pressure heater, a deaerator, a main engine coaxial feedwater pump and a high-pressure heater connected in sequence, the low-pressure cylinder side is connected to a generator, the low-pressure cylinder is connected to the low-pressure heater, the intermediate-pressure cylinder is connected to the deaerator, and the high-pressure cylinder is connected to the high-pressure heater, and the main engine coaxial feedwater pump is connected to the main shaft of the steam turbine unit through a coupling; the boiler includes a furnace, a low-temperature superheater and a high-temperature superheater connected in sequence, an economizer is also connected to the tail end of the furnace, and also includes a reheater, the high-temperature superheater is connected to the high-pressure cylinder, the high-pressure cylinder is connected to the reheater The reheater is connected to the medium-pressure cylinder, and the high-pressure heater is connected to the economizer; the low-temperature superheater and the economizer are both connected to the flue gas heat exchanger, and the flue gas at the outlet of the low-temperature superheater is transported to the economizer through the flue gas heat exchanger, and the water in the condensate storage tank is transported to the steam accumulator through the flue gas heat exchanger. The flue gas at the outlet of the low-temperature superheater heats the water in the condensate storage tank at the flue gas heat exchanger to generate high-temperature and high-pressure steam, which is stored in the steam accumulator; the small steam turbine is connected to the main engine coaxial feed water pump, and the high-temperature and high-pressure steam in the steam accumulator does work through the small steam turbine, driving the main engine coaxial feed water pump to operate normally.

[0010] Preferably, a flue gas regulating valve is provided between the low-temperature superheater and the flue gas heat exchanger; a high-temperature steam regulating valve is provided between the steam accumulator and the small steam turbine; and a condensate regulating valve is provided between the condensate storage tank and the flue gas heat exchanger.

[0011] Based on the same design concept, the present invention provides an operating method for a system with a main engine coaxial feedwater pump coupled with steam heat storage, including: using the boiler's flue gas to heat condensate to generate high-temperature and high-pressure steam when the boiler needs to reduce its load; and ensuring normal boiler feedwater when the unit is started or stopped or a failure occurs.

[0012] Preferably, when the boiler needs to reduce the load, the flue gas of the boiler is used to heat the condensate to generate high-temperature and high-pressure steam, including: keeping the high-temperature steam regulating valve closed, opening the flue gas regulating valve and the condensate regulating valve, so that the flue gas at the outlet of the low-temperature superheater is transported to the economizer through the flue gas heat exchanger, and the water in the condensate storage tank is transported to the steam accumulator through the flue gas heat exchanger, and the flue gas at the outlet of the low-temperature superheater heats the water in the condensate storage tank at the flue gas heat exchanger to generate high-temperature and high-pressure steam, and stores it in the steam accumulator.

[0013] Preferably, when the unit is started or stopped or a failure occurs, it is used to ensure the normal water supply to the boiler, including: keeping the flue gas regulating valve and the condensate regulating valve closed, opening the high-temperature steam regulating valve, and the high-temperature and high-pressure steam in the steam accumulator is used to perform work through the small steam turbine to drive the main engine coaxial feed water pump to operate normally.

[0014] Compared with the closest prior art, the present invention has the following beneficial effects:

[0015] 1. The steam heat storage structure of the present invention can utilize the flue gas from the boiler to heat condensed water to generate high-temperature and high-pressure steam when the load of the steam turbine unit needs to be reduced. It can ensure normal water supply to the boiler when the unit is started or stopped or a malfunction occurs, thereby improving the energy utilization efficiency of the coal-fired steam turbine unit, reducing energy loss, and enhancing the operational flexibility and safety of the coal-fired unit.

[0016] 2. By setting up a flue gas heat exchanger, the present invention can use the flue gas at the low-temperature superheater outlet to heat condensate when the unit is deloaded, thereby increasing the unit's deload rate, improving the energy utilization efficiency of the coal-fired steam turbine unit, and reducing energy loss.

[0017] 3. The outlet flue gas of the low-temperature superheater of the present invention is used as a heat source to heat the water in the condensate storage tank at the flue gas heat exchanger to generate high-temperature and high-pressure steam, which is stored in the steam accumulator. When the unit is started or stopped, or a failure occurs, or under other severe operating conditions, the high-temperature and high-pressure steam in the steam accumulator is used to perform work through the small steam turbine to drive the main engine coaxial feed water pump to operate normally, thereby achieving efficient heat exchange, improving the energy utilization efficiency of the coal-fired steam turbine unit, and reducing energy loss.

[0018] 4. The present invention can control the heating of condensed water by the flue gas at the outlet of the low-temperature superheater by adjusting the flue gas regulating valve and the condensed water regulating valve; and can control the output power of the small steam turbine to be consistent with the power required by the main engine coaxial feed water pump by adjusting the high-temperature steam regulating valve, thereby improving the load reduction regulation rate of the coal-fired unit and ensuring that the main engine coaxial feed water pump can operate normally when the unit is started or stopped or a fault occurs, thereby improving the operating flexibility and safety of the coal-fired unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the host coaxial water feed pump coupled with steam heat storage system of the present invention.

[0020] Reference numerals:

[0021] 1-furnace, 2-high-temperature superheater, 3-reheater, 4-low-temperature superheater, 5-economizer, 6-high-pressure cylinder, 7-medium-pressure cylinder, 8-low-pressure cylinder, 9-generator, 10-condenser, 11-high-pressure heater, 12-main engine coaxial feedwater pump, 13-deaerator, 14-low-pressure heater, 15-coupling, 16-steam accumulator, 17-condensate storage tank, 18-flue gas heat exchanger, 19-small steam turbine, 20-high-temperature steam regulating valve, 21-condensate regulating valve, 22-flue gas regulating valve. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0023] like Figure 1 As shown, the present invention provides a system for coupling a main engine coaxial feedwater pump with steam heat storage, comprising: a boiler for generating high-temperature and high-pressure steam; a steam turbine unit connected to the boiler, utilizing the impact force of the high-temperature and high-pressure steam to generate rotational mechanical energy, and cooperating with a generator 9 to generate electrical energy; a steam heat storage structure connected to the boiler, for utilizing the flue gas of the boiler to heat condensed water to generate high-temperature and high-pressure steam when the boiler needs to reduce the load, and for being connected to the steam turbine unit to ensure normal boiler feedwater when the unit is started or stopped or a fault occurs. The provision of the steam heat storage structure can utilize the flue gas of the boiler to heat condensed water to generate high-temperature and high-pressure steam when the load of the steam turbine unit needs to be reduced, and can ensure normal boiler feedwater when the unit is started or stopped or a fault occurs, thereby improving the energy utilization efficiency of the coal-fired steam turbine unit, reducing energy loss, and improving the operational flexibility and safety of the coal-fired unit.

[0024] Preferably, the steam heat storage structure includes a steam heat accumulator 16, a small steam turbine 19, a condensate storage tank 17, and a flue gas heat exchanger 18 connected in sequence, wherein the flue gas heat exchanger 18 is also connected to the steam heat accumulator 16; the flue gas heat exchanger 18 is connected to the boiler and is used to use the boiler's flue gas to heat the condensate to generate high-temperature and high-pressure steam when the boiler needs to reduce its load; the small steam turbine 19 is connected to the main engine coaxial feedwater pump 12 of the steam turbine unit and is used to ensure normal boiler feedwater when the unit is started or stopped or a fault occurs. By providing a flue gas heat exchanger, the condensate can be heated with the flue gas at the outlet of the low-temperature superheater when the unit reduces its load, thereby increasing the unit's load reduction rate, improving the energy utilization efficiency of the coal-fired steam turbine unit, and reducing energy loss.

[0025] Preferably, the flue gas heat exchanger 18 is a shell and tube heat exchanger that adopts countercurrent heat exchange, with the flue gas flowing on the shell side and the condensed water flowing on the tube side.

[0026] Preferably, a thermal insulation layer is provided on the outer side of the shell of the flue gas heat exchanger 18 .

[0027] Preferably, the operating temperature range of the steam heat storage structure is 70ºϹ-330ºϹ, the temperature of the water in the condensed water storage tank 17 is fixed at 70ºϹ, the temperature of the high-temperature and high-pressure steam in the steam accumulator 16 is 330ºϹ, and the pressure is 27MPa.

[0028] Preferably, the steam turbine unit includes a high-pressure cylinder 6, an intermediate-pressure cylinder 7, a low-pressure cylinder 8, a condenser 10, a low-pressure heater 14, a deaerator 13, a main engine coaxial feedwater pump 12 and a high-pressure heater 11 connected in sequence, the low-pressure cylinder 8 is connected to the generator 9, the low-pressure cylinder 8 is connected to the low-pressure heater 14, the intermediate-pressure cylinder 7 is connected to the deaerator 13, and the high-pressure cylinder 6 is connected to the high-pressure heater 11, and the main engine coaxial feedwater pump 12 is connected to the main shaft of the steam turbine unit through a coupling 15; the boiler includes a furnace 1, a low-temperature superheater 4 and a high-temperature superheater 2 connected in sequence, an economizer 5 is also connected to the tail end of the furnace 1, and also includes a reheater 3, the high-temperature superheater 2 is connected to the high-pressure cylinder 6, and the high-pressure cylinder 6 is connected to the reheater. 3, the reheater 3 is connected to the medium-pressure cylinder 7, and the high-pressure heater 11 is connected to the economizer 5; the low-temperature superheater 4 and the economizer 5 are both connected to the flue gas heat exchanger 18, and the flue gas at the outlet of the low-temperature superheater 4 is transported to the economizer 5 through the flue gas heat exchanger 18, and the water in the condensate storage tank 17 is transported to the steam accumulator 16 through the flue gas heat exchanger 18. The flue gas at the outlet of the low-temperature superheater 4 heats the water in the condensate storage tank 17 at the flue gas heat exchanger 18 to generate high-temperature and high-pressure steam, which is stored in the steam accumulator 16; the small steam turbine 19 is connected to the main engine coaxial feed water pump 12, and the high-temperature and high-pressure steam in the steam accumulator 16 performs work through the small steam turbine 19, driving the main engine coaxial feed water pump 12 to operate normally. The outlet flue gas of the low-temperature superheater is used as a heat source to heat the water in the condensate storage tank 17 at the flue gas heat exchanger to generate high-temperature and high-pressure steam, which is stored in the steam accumulator 16. When the unit is started or stopped, or a failure occurs, as well as under other severe working conditions, the high-temperature and high-pressure steam in the steam accumulator 16 is used to perform work through the small steam turbine 19, driving the main engine coaxial feed water pump 12 to operate normally, thereby achieving efficient heat exchange, improving the energy utilization efficiency of the coal-fired steam turbine unit, and reducing energy loss.

[0029] Preferably, a flue gas regulating valve 22 is provided between the low-temperature superheater 4 and the flue gas heat exchanger 18; a high-temperature steam regulating valve 20 is provided between the steam accumulator 16 and the small steam turbine 19; and a condensate regulating valve 21 is provided between the condensate storage tank 17 and the flue gas heat exchanger 18.

[0030] The present invention provides an operating method for a system of a main engine coaxial water feed pump coupled with steam heat storage, comprising: utilizing the flue gas of the boiler to heat condensed water to generate high-temperature and high-pressure steam when the boiler needs to reduce the load; and ensuring normal water feed to the boiler when the unit is started or stopped or a failure occurs.

[0031] Preferably, when the boiler needs to reduce its load, the boiler flue gas is used to heat condensate to generate high-temperature, high-pressure steam. This includes: keeping the high-temperature steam regulating valve 20 closed, opening the flue gas regulating valve 22 and the condensate regulating valve 21, allowing the flue gas at the outlet of the low-temperature superheater 4 to be transported to the economizer 5 via the flue gas heat exchanger 18, and transporting the water in the condensate storage tank 17 to the steam accumulator 16 via the flue gas heat exchanger 18. The flue gas at the outlet of the low-temperature superheater 4 heats the water in the condensate storage tank 17 at the flue gas heat exchanger 18 to generate high-temperature, high-pressure steam, which is then stored in the steam accumulator 16. When the unit is operating at reduced load, the main engine coaxial feedwater pump 12 is connected to the main engine via the coupling 15 and driven by the steam turbine unit. The flue gas at the outlet of the low-temperature superheater is used as a heat source to heat the condensate through the flue gas heat exchanger 18, and the high-temperature, high-pressure steam is stored in the steam accumulator 16. The flue gas regulating valve 22 and the condensate regulating valve 21 are opened, and the high-temperature steam regulating valve 20 is closed. The load reduction rate of the unit is adjusted by adjusting the flow rate of the flue gas at the outlet of the low-temperature superheater 4 and the condensed water in the condensed water storage tank 17 entering the flue gas heat exchanger 18. The specific adjustment method is as follows: when the load reduction rate of the unit is lower than the set value, the opening of the flue gas regulating valve 22 and the condensed water regulating valve 21 is increased; when the load reduction rate of the unit is higher than the set value, the opening of the flue gas regulating valve 22 and the condensed water regulating valve (21) is reduced.

[0032] Preferably, when the unit is started or stopped, or a fault occurs, the method for ensuring normal boiler water supply includes: keeping the flue gas regulating valve 22 and the condensate regulating valve 21 closed, opening the high-temperature steam regulating valve 20, and allowing the high-temperature and high-pressure steam in the steam accumulator 16 to perform work through the small steam turbine 19, driving the main engine coaxial feedwater pump 12 to operate normally. When the unit is started or stopped, or a fault occurs, the main engine coaxial feedwater pump 12 is decoupled from the steam turbine unit 6 via the coupling 15, and the high-temperature and high-pressure steam in the steam accumulator 16 enters the small steam turbine 19 to perform work, driving the main engine coaxial feedwater pump 12 to operate normally, opening the high-temperature steam regulating valve 20, and closing the flue gas regulating valve 22 and the condensate regulating valve 21. When high-temperature, high-pressure steam is used to drive the small steam turbine 19 to perform work, the flow rate of high-temperature, high-pressure steam entering the small steam turbine 19 is adjusted to control the output power of the small steam turbine 19 to be consistent with the power required by the main engine coaxial feedwater pump 12. The specific adjustment method is as follows: if the output power of the small steam turbine 19 is lower than the set power of the main engine coaxial feedwater pump 12, the opening of the high-temperature steam regulating valve 20 is increased; if the output power of the small steam turbine 19 is higher than the set power of the main engine coaxial feedwater pump 12, the opening of the high-temperature steam regulating valve 20 is reduced. The heating of the condensate by the flue gas at the outlet of the low-temperature superheater can be controlled by adjusting the flue gas regulating valve and the condensate regulating valve; by adjusting the high-temperature steam regulating valve, the output power of the small steam turbine is controlled to be consistent with the power required by the main engine coaxial feedwater pump, thereby improving the load reduction adjustment rate of the coal-fired unit and ensuring that the main engine coaxial feedwater pump can operate normally when the unit is started or stopped or a fault occurs, thereby improving the operational flexibility and safety of the coal-fired unit.

[0033] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do 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 should not be understood as a limitation on the present application.

[0034] Furthermore, the terms "above" and "below" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Thus, a feature defined as "above" or "below" may explicitly or implicitly include at least one such feature. Throughout the description of this application, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0035] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection, or communication; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0036] In this application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0037] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of the pending claims.

Claims

1. A system for coupling a main engine coaxial water feed pump with steam heat storage, characterized in that: include: Boilers, used to generate high-temperature and high-pressure steam; A steam turbine unit is connected to the boiler, and utilizes the impact force of high-temperature and high-pressure steam to generate rotary mechanical energy, and cooperates with a generator (9) to generate electrical energy; the steam turbine unit includes a high-pressure cylinder (6), an intermediate-pressure cylinder (7), a low-pressure cylinder (8), a condenser (10), a low-pressure heater (14), a deaerator (13), a main engine coaxial feedwater pump (12) and a high-pressure heater (11) connected in sequence, wherein the low-pressure cylinder (8) is connected to the generator (9), the low-pressure cylinder (8) is connected to the low-pressure heater (14), the intermediate-pressure cylinder (7) is connected to the deaerator (13), and the high-pressure cylinder (6) is connected to the high-pressure heater (11), and the main engine coaxial feedwater pump (12) is connected to the main shaft of the steam turbine unit through a coupling (15); A steam heat storage structure comprises a steam heat accumulator (16), a small steam turbine (19), a condensed water storage tank (17) and a flue gas heat exchanger (18) connected in sequence, wherein a condensed water regulating valve (21) is provided between the condensed water storage tank (17) and the flue gas heat exchanger (18), and a high-temperature steam regulating valve (20) is provided between the steam heat accumulator (16) and the small steam turbine (19); the flue gas heat exchanger (18) is also connected to the steam heat accumulator (16). The flue gas heat exchanger (18) is connected to the boiler and is used to use the flue gas of the boiler to heat condensed water to generate high-temperature and high-pressure steam when the boiler needs to reduce the load; the small steam turbine (19) is connected to the main engine coaxial feed water pump (12), and the high-temperature and high-pressure steam in the steam accumulator (16) is driven by the small steam turbine (19) to perform work and drive the main engine coaxial feed water pump (12) to operate normally, so as to ensure normal water supply to the boiler when the unit is started or stopped or a fault occurs.

2. The main engine coaxial water feed pump coupled steam thermal storage system according to claim 1, characterized in that: The flue gas heat exchanger (18) is a shell and tube heat exchanger that adopts countercurrent heat exchange, with the flue gas flowing on the shell side and the condensed water flowing on the tube side.

3. The host coaxial water feed pump coupled steam thermal storage system according to claim 2, characterized in that: A thermal insulation layer is provided on the outer side of the shell of the flue gas heat exchanger (18).

4. The main engine coaxial feedwater pump coupled steam thermal storage system according to claim 1, characterized in that: The operating temperature range of the steam heat storage structure is 70°Ϲ-330°Ϲ, the temperature of water in the condensed water storage tank (17) is fixed at 70°Ϲ, and the temperature of the high-temperature and high-pressure steam in the steam heat accumulator (16) is 330°Ϲ and the pressure is 27 MPa.

5. The main engine coaxial feedwater pump coupled steam thermal storage system according to claim 1, characterized in that: The boiler comprises a furnace (1), a low-temperature superheater (4) and a high-temperature superheater (2) connected in sequence, an economizer (5) is also connected to the tail end of the furnace (1), and also comprises a reheater (3), the high-temperature superheater (2) is connected to the high-pressure cylinder (6), the high-pressure cylinder (6) is connected to the reheater (3), the reheater (3) is connected to the medium-pressure cylinder (7), and the high-pressure heater (11) is connected to the economizer (5); the low-temperature superheater (4) and the economizer (5) are both connected to the flue gas heat exchanger (18). A flue gas regulating valve (22) is provided between the low-temperature superheater (4) and the flue gas heat exchanger (18). The flue gas at the outlet of the low-temperature superheater (4) is transported to the economizer (5) via the flue gas heat exchanger (18). The water in the condensed water storage tank (17) is transported to the steam accumulator (16) via the flue gas heat exchanger (18). The flue gas at the outlet of the low-temperature superheater (4) heats the water in the condensed water storage tank (17) at the flue gas heat exchanger (18) to generate high-temperature and high-pressure steam, which is then stored in the steam accumulator (16).

6. An operating method for a main engine coaxial feedwater pump coupled with steam thermal storage system, applied to the main engine coaxial feedwater pump coupled with steam thermal storage system according to any one of claims 1 to 5, characterized in that: The operation method includes: When the boiler needs to reduce its load, the flue gas of the boiler is used to heat condensed water to generate high-temperature and high-pressure steam; When the unit is started or stopped or a fault occurs, the high-temperature steam regulating valve (20) is opened, and the high-temperature and high-pressure steam in the steam accumulator (16) is used to perform work through the small steam turbine (19), driving the main engine coaxial feed water pump (12) to operate normally, thereby ensuring normal water supply to the boiler.

7. The operating method according to claim 6, characterized in that: When the boiler needs to reduce its load, the flue gas from the boiler is used to heat the condensed water to generate high-temperature and high-pressure steam, including: The high-temperature steam regulating valve (20) is kept closed, and the flue gas regulating valve (22) and the condensate regulating valve (21) are opened, so that the flue gas at the outlet of the low-temperature superheater (4) is transported to the economizer (5) through the flue gas heat exchanger (18), and the water in the condensate storage tank (17) is transported to the steam accumulator (16) through the flue gas heat exchanger (18). The flue gas at the outlet of the low-temperature superheater (4) heats the water in the condensate storage tank (17) at the flue gas heat exchanger (18) to generate high-temperature and high-pressure steam, which is then stored in the steam accumulator (16).

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