Main machine coaxial feed pump coupling steam heat storage system and operation method

Abstract

The invention discloses a main machine coaxial water feeding pump coupling steam heat storage system which comprises a boiler, a water pump, a heat storage device and a heat storage device. The boiler is used for generating high-temperature and high-pressure steam; the turboset is connected with the boiler, generates rotary mechanical energy by utilizing the impact force of the high-temperature and high-pressure steam, and is matched with the generator to generate electric energy; and the steam heat storage structure is connected with the boiler, is used for heating condensate water by using flue gas of the boiler to generate high-temperature and high-pressure steam when the load of the boiler needs to be reduced, is connected with the turboset, and is used for ensuring normal water supply of the boiler when the turboset is started or stopped or breaks down. Through the arrangement of the steam heat storage structure, high-temperature and high-pressure steam can be generated through heating of flue gas of the boiler when the load of the unit needs to be reduced, normal water supply of the boiler can be guaranteed when the unit is started or stopped or breaks down, the energy utilization efficiency of the coal-fired unit is improved, energy loss is reduced, and the operation flexibility and safety of the coal-fired unit are improved.

Description

Technical Field

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

[0002] The development of clean energy, such as solar energy, wind energy, tidal energy and other renewable energy is an inevitable trend in the future development of power generation, and improving the flexibility of coal-fired units is the key to dealing with the intermittent and low predictability of renewable energy. As the key to operational flexibility, thermal power plants play an important role in achieving large-scale renewable energy generation and ensuring safe and stable operation of the power grid in the continuous transformation of the current power system.

[0003] In existing coal-fired units, feedwater pumps are mostly steam-driven feedwater pumps and electric feedwater pumps. The plant consumption rate of electric feedwater pumps is particularly high, while the feedwater flow of steam-driven feedwater pumps fluctuates greatly, which is not conducive to the flexible and efficient operation of coal-fired units. The use of main engine coaxial feedwater pumps can take into account both flexibility and efficiency, but when the unit is started or stopped or fails, or under other harsh working conditions, the main engine coaxial feedwater pump is difficult to operate. Most of them are equipped with electric feedwater pumps to replace the main engine coaxial feedwater pumps to pressurize the water supply. Since an additional electric feedwater pump is required and the plant power consumption needs to be increased, the economic efficiency is poor. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention designs a main engine coaxial feedwater pump coupled with steam heat storage system, comprising: 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 a generator to generate electrical energy; a steam heat storage structure, connected to the boiler, used to use the boiler's flue gas to heat condensed water 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 feedwater 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 70ºϹ-330ºϹ, the temperature of the water in the condensate storage tank is fixed at 70ºϹ, the temperature of the high-temperature and high-pressure steam in the steam thermal storage tank is 330ºϹ, and the pressure is 27MPa.

[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 at 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, 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, 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 main engine coaxial feedwater pump coupled with steam heat storage system, including: using the boiler's flue gas to heat condensed water to generate high-temperature and high-pressure steam when the boiler needs to reduce 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 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 allowing the high-temperature and high-pressure steam in the steam accumulator 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 beneficial effects of the present invention are: 1. The steam heat storage structure of the present invention can utilize the flue gas of the boiler to heat the condensed water to generate high-temperature and high-pressure steam when the load of the steam turbine unit needs to be reduced. When the unit is started or stopped or a failure occurs, it can ensure the normal water supply of the boiler, improve the energy utilization efficiency of the coal-fired steam turbine unit, reduce energy loss, and improve the operating flexibility and safety of the coal-fired unit.

[0015] 2. The present invention provides a flue gas heat exchanger, which can heat condensed water with the flue gas at the outlet of the low-temperature superheater when the unit is deloaded, thereby increasing the load reduction rate of the unit, improving the energy utilization efficiency of the coal-fired steam turbine unit, and reducing energy losses.

[0016] 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, as well as under other severe working conditions, the high-temperature and high-pressure steam in the steam accumulator is driven by a small steam turbine to perform work and 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.

[0017] 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 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 failure occurs, thereby improving the operating flexibility and safety of the coal-fired unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the main engine coaxial water feed pump coupled with steam heat storage system of the present invention.

[0019] Reference numerals: 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

[0020] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0021] like Figure 1 As shown, the present invention provides a system of main engine coaxial feedwater pump coupled steam heat storage, including: a boiler for generating 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 9 to generate electrical energy; a steam heat storage structure connected to the boiler, 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, and connected to the steam turbine unit, used to ensure the normal feedwater of the boiler when the unit is started or stopped or a fault occurs. The setting of the steam heat storage structure can use 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 the normal feedwater of the boiler 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.

[0022] 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 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 19 is connected to the main engine coaxial feed water pump 12 of the steam turbine unit, and is used to ensure the normal feed water of the boiler when the unit is started or stopped or fails. By setting up 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 the load, thereby increasing the load reduction rate of the unit, improving the energy utilization efficiency of the coal-fired steam turbine unit, and reducing energy loss.

[0023] 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.

[0024] Preferably, a heat-insulating layer is provided on the outer side of the shell of the flue gas heat exchanger 18 .

[0025] 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.

[0026] 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 a 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, 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, and 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 driven by the small steam turbine 19 to perform work and drive 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.

[0027] 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 .

[0028] The present invention provides an operating method for a main engine coaxial feedwater pump coupled with steam heat storage system, comprising: using the flue gas of the boiler to heat condensed water to generate high-temperature and high-pressure steam when the boiler needs to reduce load; and ensuring normal feedwater to the boiler when the unit is started or stopped or a failure occurs.

[0029] 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 20 closed, opening the flue gas regulating valve 22 and the condensate regulating valve 21, 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, and 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, and stores it in the steam accumulator 16. When the unit is running at reduced load, the main engine coaxial feed water pump 12 is connected to the main engine through the coupling 15, and is driven by the steam turbine unit to run, using the flue gas at the outlet of the low-temperature superheater as a heat source, heating the condensate through the flue gas heat exchanger 18, storing the high-temperature and high-pressure steam in the steam accumulator 16, opening the flue gas regulating valve 22 and the condensate regulating valve 21, and closing the high-temperature steam regulating valve 20. 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 that 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.

[0030] Preferably, when the unit is started or stopped or a fault occurs, the method used to ensure the normal water supply of the boiler includes: keeping the flue gas regulating valve 22 and the condensate regulating valve 21 closed, opening the high-temperature steam regulating valve 20, 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 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 through 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 and high-pressure steam is used to drive the small steam turbine 19 to work, the flow rate of high-temperature and 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 that 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 flue gas at the outlet of the low-temperature superheater can be controlled to heat the condensate by adjusting the flue gas regulating valve and the condensate 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 by adjusting the high-temperature steam regulating valve, the load reduction adjustment rate of the coal-fired unit is improved, and the main engine coaxial feedwater pump can be guaranteed to operate normally when the unit is started or stopped or a failure occurs, thereby improving the operating flexibility and safety of the coal-fired unit.

[0031] 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 referred device or element 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.

[0032] In addition, the terms "above" and "below" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "above" and "below" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0033] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like 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, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0034] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. 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 may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0035] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A main engine coaxial feedwater pump coupled steam heat storage system, characterized in that: include: Boilers, used to generate high-temperature and high-pressure steam; A steam turbine unit connected to the boiler, utilizing the impact force of high-temperature and high-pressure steam to generate rotary mechanical energy, and cooperating with a generator (9) to generate electrical energy; The steam heat storage structure is connected to the boiler and is used to use the boiler's flue gas to heat condensed water to generate high-temperature and high-pressure steam when the boiler needs to reduce its load. It is also 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.

2. The main engine coaxial feedwater pump coupled steam thermal storage system according to claim 1, characterized in that: The steam heat storage structure comprises a steam heat storage device (16), a small steam turbine (19), a condensed water storage tank (17), and a flue gas heat exchanger (18) which are connected in sequence, wherein the flue gas heat exchanger (18) is also connected to the steam heat storage device (16); The flue gas heat exchanger (18) is connected to the boiler and is used to generate high-temperature and high-pressure steam by heating the flue gas of the boiler when the boiler needs to reduce load; The small steam turbine (19) 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.

3. The main engine coaxial feedwater pump coupled steam thermal storage system according to claim 2, 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.

4. The main engine coaxial feedwater pump coupled steam thermal storage system as claimed in claim 3, characterized in that: A thermal insulation layer is provided on the outer side of the shell of the flue gas heat exchanger (18).

5. The main engine coaxial feedwater pump coupled steam thermal storage system according to claim 2, 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 storage tank (16) is 330°Ϲ, and the pressure is 27 MPa.

6. The main engine coaxial feedwater pump coupled steam thermal storage system according to claim 2, characterized in that: The steam turbine unit comprises 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) which are connected in sequence, wherein the low-pressure cylinder (8) is connected to a 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 via a coupling (15); 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); 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); 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), thereby driving the main engine coaxial feed water pump (12) to operate normally.

7. The main engine coaxial feedwater pump coupled steam thermal storage system according to claim 6, characterized in that: 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 heat accumulator (16) and the small steam turbine (19); A condensate regulating valve (21) is provided between the condensate storage tank (17) and the flue gas heat exchanger (18).

8. A method for operating a main engine coaxial feedwater pump coupled with steam thermal storage system, characterized in that: include: When the boiler needs to reduce its load, the flue gas of the boiler is used for heating to generate high-temperature and high-pressure steam; It is used to ensure normal water supply to the boiler when the unit is started or stopped or a failure occurs.

9. The operating method according to claim 8, characterized in that: The method of using 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 includes: 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) via the flue gas heat exchanger (18), and the water in the condensate 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 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).

10. The operating method according to claim 8, characterized in that: When the unit is started or stopped or a fault occurs, it is used to ensure normal water supply to the boiler, including: Keep the flue gas regulating valve (22) and the condensate regulating valve (21) closed, open the high-temperature steam regulating valve (20), and the high-temperature and high-pressure steam in the steam accumulator (16) performs work through the small steam turbine (19), thereby driving the main engine coaxial feed water pump (12) to operate normally.

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