Flexible operation system configuration of coal-fired thermal power generating unit

Abstract

The utility model provides a flexible operation system configuration of a coal-fired thermal power generating unit, which is characterized in that on the basis of an existing boiler feed water heating system, a newly-added external steam cooler is additionally arranged on a water supply pipeline, and a feed water outlet of the newly-added external steam cooler is connected with a boiler feed water inlet; a steam side inlet of the newly-added external steam cooler is connected with the temperature reduction module, a steam side outlet of the newly-added external steam cooler communicates with a steam inlet of an existing final-stage high-pressure heater, and steam with the pressure grade higher than that of regenerative extraction steam of a high-pressure cylinder is introduced into an inlet of the temperature reduction module. Steam discharged from the temperature reduction module firstly heats feed water at the rear end in a newly added external steam cooler and then is conveyed to an existing final-stage high-pressure heater to heat feed water at the front end, so that the temperature of feed water entering a furnace of the unit under the deep peak regulation working condition is increased, and a denitration system of the unit under the deep peak regulation working condition is continuously and stably put into operation; the unit operation economy is effectively improved, and meanwhile the unit operation economy and flexibility are improved.

Description

Technical Field

[0001] This utility model relates to the field of power generation technology, and in particular to a flexible operation system configuration for coal-fired power units. Background Technology

[0002] Currently, high-parameter, large-capacity, high-efficiency, and low-carbon ultra-supercritical units have become the mainstream choice for new thermal power plant units. However, among the existing units, there are approximately 1,000 subcritical units in the 300,000 to 600,000 kW range, with an installed capacity of about 350 million kW.

[0003] In recent years, the installed capacity and power generation of new energy sources have reached new highs. Due to the uncertainty of power generation from new energy sources, traditional thermal power units, especially coal-fired power units, must assume the role of basic power supply and flexible peak-shaving power supply to support new energy power generation.

[0004] Taking a 300MW subcritical unit as an example, its high-pressure cylinder adopts a partial steam inlet method and is equipped with a regulating stage. The power grid dispatch load range in this region is 40%-100% THA. However, with the rapid development of new energy sources, the power grid in this region has now notified the unit that it needs to operate under deep peak shaving, and the lower limit of load dispatch needs to be as low as 20%.

[0005] For subcritical units that need to participate in deep peak shaving operation, such as those with a load variation range of 20%-100% THA, where the deep peak shaving load range is 20%-30% THA or even lower (using partial steam intake in the high-pressure cylinder and equipped with a regulating stage), the following problems will be faced:

[0006] (1) Under deep peak-shaving conditions, the economizer outlet flue gas temperature will be lower than the lower limit of the normal operating temperature of the denitrification catalyst, such as 300℃. The denitrification system will not be able to operate normally, and NO is expected to rise. X Emissions will surge and far exceed standard requirements, such as the emission limit being raised from 25 mg / Nm³. 3 The concentration of Nm2 surged to 200 mg / Nm3 3 The above levels far exceed the standard value of 50 mg / Nm³. 3 .

[0007] (2) The boiler drum outlet temperature drops significantly, the main and reheat steam temperatures will decrease significantly, the unit energy consumption will increase significantly, and the operating economy will decrease significantly.

[0008] Therefore, how to maintain the continuous and stable operation of the denitrification system under deep peak shaving conditions for subcritical units, and avoid a significant increase in unit energy consumption and a significant decrease in operating economy, has become an urgent problem to be solved. Utility Model Content

[0009] The technical problem to be solved by this utility model is to overcome the defects of subcritical units where the denitrification system cannot operate normally under deep peak shaving conditions, the unit's energy consumption increases significantly, and the operating economy decreases significantly, and to provide a flexible operating system configuration for coal-fired power units.

[0010] The present invention solves the above-mentioned technical problems through the following technical solution:

[0011] This utility model provides a flexible operation system configuration for a coal-fired power unit, comprising: a boiler, a deaerator system, a high-pressure cylinder, an existing final-stage high-pressure heater, feedwater pipelines, and steam pipelines. The boiler includes an economizer, a steam drum, a superheater, a header, a downcomer, and water-cooled walls. The economizer, steam drum, and superheater are connected sequentially via pipelines. Water from the lower part of the steam drum flows through the downcomer to the header, is heated by the water-cooled walls, and then returns to the steam drum. The high-pressure cylinder adopts a partial steam intake method. The feedwater pipelines are sequentially equipped with a deaerator system, an existing final-stage high-pressure heater, and a newly added external steam cooler. The feedwater outlet of the device is connected to the boiler feedwater inlet; the steam pipeline includes a main steam pipeline connecting the boiler steam outlet and the high-pressure cylinder steam inlet, and an extraction steam pipeline connecting the high-pressure cylinder extraction steam inlet and the existing final-stage high-pressure heater inlet; the main steam pipeline is equipped with a regulating stage steam inlet valve group, and the extraction steam pipeline is equipped with an extraction steam isolation valve; the steam-side inlet of the newly added external steam cooler is connected to a desuperheating module, and the inlet of the desuperheating module is connected to steam with a higher pressure level than the regenerative extraction steam of the high-pressure cylinder; the steam-side outlet of the newly added external steam cooler is connected to the steam inlet of the existing final-stage high-pressure heater.

[0012] In this scheme, the feedwater is sequentially heated through the deaeration system, the existing final-stage high-pressure heater, and the newly added external steam cooler before being sent to the boiler feedwater inlet. The steam-side inlet of the newly added external steam cooler is connected to a desuperheating module. The inlet of the desuperheating module receives steam with a higher pressure level than the regenerative extraction steam from the high-pressure cylinder. The steam-side outlet of the newly added external steam cooler is connected to the steam inlet of the existing final-stage high-pressure heater. The steam with a higher pressure level than the regenerative extraction steam from the high-pressure cylinder is desuperheated by the desuperheating module and then first goes to the newly added external steam cooler to heat the feedwater. Then, the steam from the steam outlet of the newly added external steam cooler is sent to the existing final-stage high-pressure heater to heat the feedwater located in front of the newly added external steam cooler. This not only improves the feedwater temperature of the unit under deep peak shaving conditions but also improves the heat utilization rate. As the feedwater temperature of the unit increases, the economizer inlet water temperature increases, which in turn increases the economizer outlet water temperature, and the economizer outlet flue gas temperature increases to meet the denitrification inlet flue gas temperature requirements.

[0013] Preferably, the cooling module includes an isolation valve, a pressure reducing valve, and a cooler connected in sequence by pipes, with cooling water connected to the cooler.

[0014] In this scheme, steam with a higher pressure level than the regenerative extraction steam of the high-pressure cylinder enters the desuperheating module, is depressurized by the pressure reducing valve, and then enters the desuperheater to mix with desuperheating water to achieve desuperheating and pressure reduction. Through the function of the desuperheating module, the steam with a higher pressure level than the regenerative extraction steam of the high-pressure cylinder is desuperheated and depressurized, ensuring the safe operation of the system.

[0015] Preferably, when the steam from the steam-side outlet of the newly added external steam cooler is used to heat the feedwater in the existing final stage high-pressure heater, the extraction steam isolation valve on the extraction steam pipeline of the existing final stage high-pressure heater is in the closed state, and the steam pressure at the steam-side outlet of the newly added external steam cooler is higher than the regenerative extraction steam pressure of the high-pressure cylinder.

[0016] In this scheme, the steam pressure at the steam-side outlet of the newly added external steam cooler is higher than the regenerative extraction steam pressure of the high-pressure cylinder, which makes the steam pressure entering the existing final-stage high-pressure heater higher than the regenerative extraction steam of the high-pressure cylinder, thereby further increasing the feedwater temperature entering the boiler.

[0017] Preferably, the boiler is equipped with a circulating pump in the downcomer connecting the steam drum and the header.

[0018] In this scheme, a circulation pump is installed in the downcomer connecting the steam drum and the header to enhance the driving force of the working fluid circulation flow, so that the water in the lower part of the steam drum can flow smoothly through the downcomer to the header.

[0019] Preferably, the steam source with a higher pressure level than the regenerative extraction steam of the high-pressure cylinder is a mixture of the main steam of the unit, the steam in the superheater system, the steam in the rear chamber of the high-pressure cylinder regulating stage, or any one of the main steam, the steam in the superheater system, and the steam in the rear chamber of the high-pressure cylinder regulating stage, with the regenerative extraction steam or reheat steam of the unit.

[0020] This solution makes full use of the steam in the unit and provides multiple options for steam sources with higher pressure levels than the regenerative extraction steam of the high-pressure cylinder. Under the premise that the steam entering the newly added external steam cooler is higher than the existing regenerative extraction steam, the operational flexibility of the unit is improved.

[0021] Preferably, the steam source with a higher pressure level than the regenerative extraction steam of the high-pressure cylinder is the main steam of the unit, and the inlet of the desuperheating module is connected to the main steam pipeline to introduce part of the main steam.

[0022] In this scheme, the inlet of the desuperheating module is connected to the main steam pipeline. By introducing a portion of the main steam into the desuperheating module, the steam is desuperheated and depressurized before being sent to the newly added external steam cooler to heat the feedwater, thereby increasing the feedwater temperature of the unit under deep peak shaving conditions.

[0023] Preferably, the steam source with a higher pressure level than the regenerative extraction steam of the high-pressure cylinder is a mixture of main steam from other units, steam in the superheater system, steam in the regulating chamber of the high-pressure cylinder, or steam in the main steam, steam in the superheater system, or steam in the regulating chamber of the high-pressure cylinder, and regenerative extraction steam or reheat steam.

[0024] In this scheme, steam from other units is used to improve the operational flexibility of the unit and optimize the thermodynamic cycle of the entire system, provided that the steam entering the newly added external steam cooler is higher than that of the existing regenerative extraction steam.

[0025] Preferably, the number of valves in the regulating stage inlet valve group is four or six.

[0026] In this scheme, the number of valves in the regulating stage inlet valve group is four or six. By regulating the main steam flow through multiple valves, not only is the flow control accuracy high, but the flow of a single valve is relatively small, which makes the pressure control of the main steam more precise and convenient.

[0027] Preferably, the flexible operation system is configured to: throttle the main steam using the regulating stage inlet steam valve group to maintain a certain feedwater pressure and keep the economizer outlet feedwater at a certain degree of subcooling.

[0028] In this scheme, steam with a higher pressure rating than the regenerative extraction steam from the high-pressure cylinder is de-cooled and depressurized in the de-cooling module before entering the newly added external steam cooler to supplement the feedwater heating. It also enters the existing final-stage high-pressure heater after the newly added external steam cooler to heat the feedwater, thereby increasing the unit's feedwater temperature under deep peak-shaving conditions. By operating the regulating stage inlet steam valve group, the original regulating stage inlet steam valve group is used to throttle the main steam. The purpose is to maintain a certain feedwater pressure and keep the economizer outlet feedwater at a certain degree of subcooling. Furthermore, by using the regulating stage inlet steam valve group to control the main steam, a certain steam enthalpy drop can also be achieved, thus relatively improving the unit's economic efficiency.

[0029] Preferably, a throttling device is installed in the feedwater or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feedwater pressure.

[0030] In this scheme, throttling components, such as regulating valves, can be installed in the feedwater or steam pipeline from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feedwater pressure, thereby keeping the economizer outlet feedwater at a certain degree of subcooling.

[0031] The positive and progressive effects of this utility model are as follows: Based on the existing boiler feedwater heating system, a new external steam cooler is added to the feedwater pipeline, and the feedwater outlet of the new external steam cooler is connected to the boiler feedwater inlet; the steam-side inlet of the new external steam cooler is connected to a desuperheating module, and the inlet of the desuperheating module is connected to steam with a higher pressure level than the regenerative extraction steam of the high-pressure cylinder; the steam-side outlet of the new external steam cooler is connected to the steam inlet of the existing final-stage high-pressure heater; the steam from the desuperheating module first heats the feedwater at the downstream end in the new external steam cooler, and then the steam from the steam-side outlet of the new external steam cooler is sent to the existing final-stage high-pressure heater to heat the feedwater at the upstream end. This not only improves the feedwater temperature of the unit under deep peak shaving conditions, but also improves the heat utilization rate; as the feedwater temperature of the unit increases, the economizer inlet water temperature increases, and consequently the economizer outlet water temperature increases, and the economizer outlet flue gas temperature increases to meet the denitrification inlet flue gas temperature requirements. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a boiler feedwater heating system in the prior art.

[0033] Figure 2 This is a configuration of a flexible operation system for a coal-fired power unit according to an embodiment of the present invention. Detailed Implementation

[0034] The present invention will be described more clearly and completely below with reference to the accompanying drawings, using a preferred embodiment.

[0035] Figure 1This is a schematic diagram of a boiler feedwater heating system in the prior art. The system includes a boiler, a deaerator system, a high-pressure cylinder, and an existing final-stage high-pressure heater. The boiler includes an economizer, a steam drum, a superheater, a header, a downcomer, and water-cooled walls. The economizer, steam drum, and superheater are connected sequentially by pipelines. Water from the lower part of the steam drum flows through the downcomer to the header, is heated by the water-cooled walls, and then returns to the steam drum. The deaerator system includes a deaerator, a booster pump, and a feedwater pump. The high-pressure cylinder uses a partial steam inlet method and is equipped with a regulating stage. A regulating stage inlet valve group is arranged on the main steam pipeline. An extraction steam isolation valve is installed on the inlet pipeline connecting the high-pressure cylinder and the existing final-stage high-pressure heater. The steam source for the existing final-stage high-pressure heater is the final-stage extraction steam from the high-pressure cylinder. During system operation: the low-pressure condensate from the deaerator outlet is pressurized sequentially by the booster pump and the feedwater pump before entering the high-pressure heater for heating. The heated feedwater enters the boiler, is further heated by the economizer, and then enters the steam drum. The steam-water mixture undergoes steam-water separation in the steam drum. Specifically, the water in the lower part of the steam drum flows through the downcomer to the header, is heated by the water-cooled wall, and then returns to the steam drum. The wet saturated steam in the upper part of the steam drum enters the superheater and other heating surfaces for heating, and finally obtains the main steam which enters the high-pressure cylinder to do work.

[0036] To overcome the shortcomings of subcritical units where the denitrification system cannot operate normally under deep peak-shaving conditions, resulting in a significant increase in unit energy consumption and a substantial decrease in operating economy, this utility model provides a flexible operation system configuration for coal-fired power units, such as... Figure 2 As shown, the boiler includes an economizer, steam drum, superheater, header, downcomer, and water-cooled walls. The economizer, steam drum, and superheater are connected sequentially by pipelines. Water from the bottom of the steam drum flows through the downcomer to the header, is heated by the water-cooled walls, and then returns to the steam drum. The high-pressure cylinder uses a partial steam inlet and is equipped with a regulating stage. The deaeration system, the existing final-stage high-pressure heater, and the newly added external steam cooler are sequentially installed in the feedwater pipeline. The feedwater outlet of the newly added external steam cooler is connected to the boiler feedwater inlet. The steam pipeline includes a main steam pipeline connecting the boiler steam outlet and the high-pressure cylinder inlet, and an extraction steam pipeline connecting the high-pressure cylinder extraction steam outlet and the existing final-stage high-pressure heater inlet. A regulating stage inlet valve group is installed on the main steam pipeline, and an extraction steam isolation valve is arranged on the extraction steam pipeline. The steam-side inlet of the newly added external steam cooler is connected to a desuperheating module. The inlet of the desuperheating module receives steam with a higher pressure level than the regenerative extraction steam of the high-pressure cylinder. The steam-side outlet of the newly added external steam cooler is connected to the inlet of the existing final-stage high-pressure heater. Figure 2The steam-side outlet of the newly added external steam cooler is connected to the extraction steam pipeline via a pipe, with the connection point located downstream of the extraction steam isolation valve. The steam exiting the desuperheating module first heats the feedwater downstream at the newly added external steam cooler, and then the steam from the steam-side outlet of the newly added external steam cooler is sent to the existing final-stage high-pressure heater to heat the feedwater upstream. This not only improves the feedwater temperature at the boiler inlet under deep peak shaving conditions, but also improves the heat utilization rate. At this time, the extraction steam isolation valve on the extraction steam pipeline is in the closed state, and the regulating stage inlet steam valve group set on the main steam pipeline is used to throttle the main steam to maintain a certain feedwater pressure and keep the economizer outlet feedwater at a certain degree of subcooling. As the feedwater temperature of the unit increases under deep peak shaving conditions, the economizer inlet water temperature, economizer outlet water temperature, economizer outlet flue gas temperature, and steam drum outlet steam temperature are all increased. This facilitates the continuous and stable operation of the denitrification system under deep peak shaving conditions, avoids a significant increase in unit energy consumption, effectively improves the unit's operating economy, and avoids large-scale modifications to the boiler and turbine thermal systems. It also better adapts to the wide load range of the unit's response to deep peak shaving of the power grid, while improving the unit's operating economy and flexibility.

[0037] Of course, the steam-side outlet of the newly added external steam cooler can also be connected to the steam inlet of the existing final-stage high-pressure heater through a pipeline. As long as the steam-side outlet of the newly added external steam cooler is connected to the steam inlet of the existing final-stage high-pressure heater, closing the extraction steam isolation valve will not affect the delivery of the steam from the steam-side outlet of the newly added external steam cooler to the existing final-stage high-pressure heater to heat the feedwater. This allows the extraction steam isolation valve to be closed, thus replacing the existing final-stage high-pressure heater regenerative extraction steam with the steam from the outlet of the newly added external steam cooler.

[0038] In this embodiment, when increasing the feedwater temperature of the unit under deep peak shaving conditions, the main steam is throttled by operating the regulating stage steam inlet valve group. The purpose is to maintain a certain feedwater pressure and keep the economizer outlet feedwater at a certain degree of subcooling. In addition, the regulating stage steam inlet valve group can control the main steam while also obtaining a certain steam enthalpy drop, thereby improving the unit's economy. Of course, in other embodiments, throttling components, such as regulating valves, can be installed in the feedwater or steam pipeline from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feedwater pressure and thus keep the economizer outlet feedwater at a certain degree of subcooling.

[0039] like Figure 2As shown, the desuperheating module includes an isolation valve, a pressure reducing valve, and a desuperheater connected in sequence by pipes, with desuperheating water connected to the desuperheater. Steam with a higher pressure level than the regenerative extraction steam from the high-pressure cylinder enters the desuperheating module, is depressurized by the pressure reducing valve, and mixes with the desuperheating water in the desuperheater to achieve desuperheating and pressure reduction. Through the action of the desuperheating module, the steam with a higher pressure level than the regenerative extraction steam from the high-pressure cylinder is desuperheated and depressurized, ensuring the safe operation of the system.

[0040] The steam pressure at the steam-side outlet of the newly added external steam cooler is higher than the regenerative extraction steam pressure of the high-pressure cylinder, which makes the steam pressure entering the existing final-stage high-pressure heater higher than the regenerative extraction steam of the high-pressure cylinder, thereby further increasing the feedwater temperature entering the boiler.

[0041] Although Figure 2 In this embodiment, the water in the boiler drum flows directly to the header through the downcomer. Of course, in other embodiments, a circulation pump can also be installed in the downcomer connecting the boiler drum and the header to enhance the driving force of the working fluid circulation, so that the water in the lower part of the drum can flow smoothly to the header through the downcomer.

[0042] like Figure 2 As shown, the steam source with a higher pressure level than the regenerative extraction steam of the high-pressure cylinder is the main steam. The inlet of the desuperheating module is connected to the main steam pipeline to introduce part of the main steam. The introduced part of the main steam passes through the isolation valve and pressure reducing valve in the desuperheating module and enters the desuperheater to mix with the desuperheating water. Then it is sent to the newly added external steam cooler to supplement the heating of the feedwater. The steam outlet of the external steam cooler is then sent to the existing final stage high-pressure heater to heat the feedwater, so as to improve the feedwater temperature of the unit under deep peak shaving conditions. Of course, in other embodiments, the steam source with a higher pressure level than the regenerative extraction steam of the high-pressure cylinder can be the main steam of the unit, the steam in the superheater system, the steam in the rear chamber of the high-pressure cylinder regulating stage, or a mixture of the main steam, the steam in the superheater system, and the steam in the rear chamber of the high-pressure cylinder regulating stage with the regenerative extraction steam or reheat steam of the unit. This allows for full utilization of the unit's steam and provides multiple options for a steam source with a higher pressure level than the regenerative extraction steam of the high-pressure cylinder. Under the premise that the steam entering the external steam cooler is higher than the existing regenerative extraction steam, it improves... This enhances the operational flexibility of the unit. Furthermore, the source of steam with a higher pressure level than the regenerative extraction steam from the high-pressure cylinder can be a mixture of main steam from other units, steam within the superheater system, steam from the regulating chamber after the high-pressure cylinder, or steam from any of the main steam, superheater system, or regulating chamber after the high-pressure cylinder from other units, along with regenerative extraction steam or reheat steam. This allows for full utilization of steam from other units, improving the operational flexibility of the unit while optimizing the overall system's thermodynamic cycle, provided that the steam entering the external steam cooler is higher than the existing regenerative extraction steam.

[0043] Figure 2 In the regulating stage, the number of valves in the steam inlet valve group is four, but it can also be set to six. By regulating the main steam flow through multiple valves, the main steam flow can be controlled, and a certain steam enthalpy drop can be obtained, which improves the economic efficiency of the unit. Not only is the flow control accuracy high, but the flow of a single valve is relatively small, making the pressure control of the main steam more precise and convenient.

[0044] The flexible operation system for coal-fired power units provided by this utility model, configured under deep peak-shaving conditions (taking 20% ​​THA as an example), allows the feedwater temperature at the boiler inlet to be increased to 75% THA or even 100% THA. As the feedwater temperature increases, the economizer inlet water temperature rises, leading to an increase in the economizer outlet water temperature and consequently, the economizer outlet flue gas temperature, meeting the denitrification inlet flue gas temperature requirements. Furthermore, while the economizer outlet water temperature increases, a certain feedwater pressure is maintained, ensuring a certain degree of subcooling at the economizer outlet. Moreover, with the increase in feedwater pressure, the pressure of the steam-water mixture in the steam drum also increases, raising the temperature of the wet saturated steam at the top of the steam drum, and further increasing the main steam temperature. Furthermore, with the increase in the ratio of main steam temperature, main steam quantity, and reheat steam quantity, both cold reheat steam and hot reheat steam temperatures are increased, thus preventing a significant increase in unit energy consumption and effectively improving the unit's operational economy.

[0045] Taking a 300MW subcritical unit with a partial steam inlet in its high-pressure cylinder and a regulating stage as an example, and the unit operating under 20% THA conditions.

[0046] The current system has the following parameters: main generator load 60MW, current final stage high pressure heater inlet steam pressure and temperature parameters 1.29MPa, 370℃, outlet feedwater pressure and temperature parameters 8.5MPa, 192℃, economizer outlet water temperature 211℃, subcooling 107.3℃, underenthalpy 521kJ / kg, economizer outlet flue gas temperature 272℃, and denitrification system cannot be put into operation.

[0047] In this embodiment, the main generator load is 60MW. After the addition of an external steam cooler for de-cooling, the existing final-stage high-pressure heater inlet steam pressure and temperature parameters are 3.65MPa and 422℃, and the outlet feedwater pressure and temperature parameters are 10.6MPa and 245℃. The water-side temperature rise of the new external steam cooler is 7℃, the economizer outlet water temperature is 272℃, the subcooling is 43.3℃, ​​the under-enthalpy is 239.8kJ / kg, and the economizer outlet flue gas temperature is 338℃. The denitrification system is stably and continuously put into operation, and the unit's operating economy is improved due to the relative increase in feedwater temperature. Meanwhile, The inlet and outlet flow rates, pressures, and temperatures of the regulating stage are 208 t / h, 10 MPa, and 531℃, and 208 t / h, 2.5 MPa, and 440℃, respectively. The effective enthalpy drop per unit working fluid is 125 kJ / kg, corresponding to a power output of 7.2 MW. Compared to the isenthalpic throttling method that simply uses valves without a regulating stage, the regulating stage inlet valve group achieves the same pressure control effect for the main steam while improving the unit's economic efficiency. Furthermore, because the flow rate of each valve in the regulating stage inlet valve group is relatively small, its pressure control of the main steam will be more precise and convenient.

[0048] While specific embodiments of this utility model have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this utility model is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this utility model, but all such changes and modifications fall within the scope of protection of this utility model.

Claims

1. A flexible operation system configuration for a coal-fired thermal power plant, comprising: The boiler, oxygen removal system, high-pressure cylinder, existing final-stage high-pressure heater, feedwater pipeline and steam pipeline are characterized in that the boiler comprises an economizer, a steam drum, a superheater, a header, a downcomer and a water cooling wall; the economizer, the steam drum and the superheater are sequentially connected through pipelines, water at the lower part of the steam drum is led to the header through the downcomer, and then is heated by the water cooling wall and returned to the steam drum; the high-pressure cylinder adopts a partial admission mode; the oxygen removal system, the existing final-stage high-pressure heater and the newly-added external steam cooler are sequentially arranged in the feedwater pipeline, the feedwater outlet of the newly-added external steam cooler is connected to the feedwater inlet of the boiler; the steam pipeline comprises a main steam pipeline connected between the steam outlet of the boiler and the steam inlet of the high-pressure cylinder and a steam extraction pipeline connected between the steam extraction port of the high-pressure cylinder and the steam inlet of the existing final-stage high-pressure heater; the main steam pipeline is provided with an adjusting-stage steam inlet valve group, and the steam extraction pipeline is arranged with a steam extraction isolation valve; the steam-side inlet of the newly-added external steam cooler is connected with a desuperheating module, the inlet of the desuperheating module is connected to steam of a higher pressure grade than the regenerative extraction steam of the high-pressure cylinder, and the steam-side outlet of the newly-added external steam cooler is communicated with the steam inlet of the existing final-stage high-pressure heater.

2. The flexible operating system configuration of claim 1, wherein, The desuperheating module comprises an isolation valve, a pressure-reducing valve and a desuperheater which are sequentially connected through pipelines, and the desuperheater is connected to desuperheating water.

3. The flexible operating system configuration of claim 2, wherein, When the steam at the steam-side outlet of the newly-added external steam cooler is used to heat the feedwater in the existing final-stage high-pressure heater, the steam extraction isolation valve on the steam extraction pipeline between the steam inlets of the existing final-stage high-pressure heater is in a closed state, and the steam pressure at the steam-side outlet of the newly-added external steam cooler is higher than the regenerative extraction steam pressure of the high-pressure cylinder.

4. The flexible operating system configuration of claim 3, wherein, In the boiler, a circulating pump is arranged in the downcomer connected between the steam drum and the header.

5. The flexible operating system configuration of claim 3, wherein, The steam of a higher pressure grade than the regenerative extraction steam of the high-pressure cylinder is sourced from the main steam in the unit, steam in the superheater system or high-pressure cylinder adjusting-stage back cavity, or mixed steam of any one of the main steam, steam in the superheater system, high-pressure cylinder adjusting-stage back cavity and regenerative extraction steam or reheated steam in the unit.

6. The flexible operating system configuration of claim 3, wherein, The steam of a higher pressure grade than the regenerative extraction steam of the high-pressure cylinder is sourced from the main steam in the unit, and the inlet of the desuperheating module is connected to the main steam pipeline to introduce part of the main steam.

7. The flexible operating system configuration of claim 4, wherein, The steam of a higher pressure grade than the regenerative extraction steam of the high-pressure cylinder is sourced from the main steam in other units, steam in the superheater system or high-pressure cylinder adjusting-stage back cavity, or mixed steam of any one of the main steam, steam in the superheater system, high-pressure cylinder adjusting-stage back cavity and regenerative extraction steam or reheated steam in other units.

8. The flexible operational system configuration of claim 1, wherein, The number of valves in the adjusting-stage steam inlet valve group is four or six.

9. The flexible operational system configuration of any of claims 1-8, wherein, The flexible operation system configuration is configured to throttle the main steam by using the adjusting-stage steam inlet valve group to maintain a certain feedwater pressure and keep the feedwater at the economizer outlet at a certain subcooling degree.

10. The flexible operational system configuration of any of claims 1-8, wherein, A throttling component is arranged in the feedwater or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feedwater pressure.

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