System configuration for coal power unit to adapt to flexible operation

Abstract

The utility model provides a system configuration for a coal power unit to adapt to flexible operation, which is characterized in that a newly-added final-stage high-pressure heater and a newly-added external steam cooler are sequentially arranged at an existing final-stage high-pressure water supply outlet in a water supply pipeline, and a steam side inlet of the newly-added external steam cooler is connected with a pressurization module; steam lower than the target steam extraction pressure grade is introduced into an inlet of the pressurization module, and a steam side outlet of the newly-added external steam cooler communicates with a steam inlet of the newly-added final-stage high-pressure heater. Steam lower than a target steam extraction pressure grade is introduced and pressurized by a pressurization module, and then is subjected to two times of supplementary heating in a newly-added external steam cooler and a newly-added final-stage high-pressure heater, so that the in-furnace feed water temperature of the unit is increased, and meanwhile, a certain feed water pressure is maintained, so that feed water at an outlet of a coal economizer is kept at a certain supercooling degree; the denitration system of the unit can be continuously and stably put into operation under the working condition of deep peak regulation, the energy consumption of the unit is prevented from being greatly increased, and the operation economy of the unit is effectively improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of power generation, especially to a system configuration for flexible operation of coal power unit. BACKGROUND

[0002] At present, the ultra (ultra) supercritical unit with high parameters, large capacity and high efficiency and low carbon has become the mainstream of the selection of new units in thermal power plants. However, for the stock units, about 1000 subcritical units of 300-600 MW level, the installed capacity is about 350 million kilowatts.

[0003] In recent years, the installed capacity and power generation of new energy have reached a new high, but due to the uncertainty of power generation of new energy generation, traditional thermal power units, especially coal-fired thermal power units, still have to bear the role of basic guarantee power supply and flexible peak regulation power supply for new energy power generation.

[0004] Taking a 300 MW subcritical unit as an example, its high-pressure cylinder adopts full circumference admission, and no regulating stage is configured. The load range of the power grid in this area is 40%-100% THA. However, with the rapid development of new energy, the power grid in this area has informed the unit to run in deep peak regulation, and the lower limit of load scheduling needs to be as low as 20%.

[0005] For subcritical units that need to participate in deep peak regulation, the high-pressure cylinder adopts full circumference admission, and no regulating stage is configured. The load range is 20%-100% THA, of which the deep peak regulation load range is 20%-30% THA, or even lower. The following problems will be faced:

[0006] (1) Under the condition of deep peak regulation, the flue gas temperature at the outlet of the economizer will be lower than the lower limit of the normal operating temperature of the denitration catalyst, such as 300℃. The denitration system will not be able to operate normally, and it is predicted that the NO X emission will increase explosively and be much higher than the standard required value, such as the emission index from 25mg / Nm 3 to 200mg / Nm 3 , which is far beyond the standard value of 50mg / Nm 3 .

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

[0008] Therefore, how the subcritical unit maintains the continuous and stable operation of the denitration system under the condition of deep peak regulation, avoids the significant increase of unit energy consumption and the significant decrease of operation economy, has become a problem to be solved. INVENTION CONTENTS

[0009] The utility model wants to solve the technical problem that how the subcritical unit maintains the denitration system to run continuously and stably under the condition of deep peak regulation, avoids the unit energy consumption to rise greatly, the operation economy to drop greatly greatly, provides a kind of system configuration of coal power unit adaptive flexible operation.

[0010] The utility model solves the above technical problem by the following technical scheme:

[0011] The utility model provides a kind of system configuration of coal power unit adaptive flexible operation, it includes: boiler, deaerating system, high pressure cylinder, existing last stage high pressure heater, feedwater line and steam pipe, boiler includes economizer, steam drum, superheater, header, downcomer and water-cooled wall;The economizer, steam drum, superheater are sequentially connected by pipeline, the water in the lower part of steam drum is to header by downcomer, then is heated to steam drum again by water-cooled wall;High pressure cylinder adopts full circumference admission mode, is not configured to adjust level;In feedwater line, deaerating system, existing last stage high pressure heater, new last stage high pressure heater, new external steam cooler are sequentially arranged along the feedwater flow direction, steam pipe includes main steam pipe connected between the steam outlet of boiler and the steam inlet of high pressure cylinder and extraction pipe connected between the steam extraction port of high pressure cylinder and the steam inlet of existing last stage high pressure heater;Main steam pipe is provided with main steam throttling assembly, and extraction pipe is provided with extraction isolation valve;The steam side inlet of new external steam cooler is connected with booster module, the inlet of booster module is connected with steam below target extraction pressure level, and the steam side outlet of new external steam cooler is communicated with the steam inlet of new last stage high pressure heater.

[0012] In the scheme, the feedwater outlet of existing last stage high pressure in feedwater line is sequentially provided with new last stage high pressure heater and new external steam cooler, the steam side inlet of new external steam cooler is connected with booster module, the inlet of booster module is connected with steam below target extraction pressure level, and the steam side outlet of new external steam cooler is communicated with the steam inlet of new last stage high pressure heater, steam below target extraction pressure level is first heated in new external steam cooler after being boosted by booster module, and then is heated in new last stage high pressure heater, that is, on the basis of existing last stage high pressure heater being normally put into use to heat feedwater, steam below target extraction pressure level is boosted by booster module and is heated twice in new external steam cooler and new last stage high pressure heater respectively, so as to improve the inlet feedwater temperature of unit, with the improvement of inlet feedwater temperature of unit, the inlet water temperature of economizer is improved, and then the outlet water temperature of economizer is improved, and the outlet flue gas temperature of economizer is improved and meets the requirement of denitration inlet flue gas temperature.

[0013] Preferably, a steam compressor is installed in the pipeline of the booster module. The steam compressor is used to boost the steam entering the booster module that is below the target extraction pressure level, so that the steam below the target extraction pressure level is boosted by the steam compressor to a pressure higher than the pressure of the final stage extraction steam of the high-pressure cylinder.

[0014] In this scheme, a steam compressor is installed in the pressurization module. The steam compressor pressurizes the steam that is below the target extraction pressure level and then sequentially enters the newly added external steam cooler and the newly added final stage high-pressure heater to supplement the heating of the feedwater. The steam that is below the target extraction pressure level is pressurized by the steam compressor to a pressure higher than the final stage extraction pressure of the high-pressure cylinder. This ensures that the steam pressure entering the newly added external steam cooler after being compressed by the steam compressor is higher than the final stage extraction pressure entering the existing final stage high-pressure heater, thereby ensuring that the feedwater is heated to a higher temperature to improve the boiler feedwater temperature of the unit under deep peak shaving conditions.

[0015] Preferably, the steam pressure at the steam-side outlet of the newly added external steam cooler is higher than the extraction steam pressure of the final stage of the high-pressure cylinder.

[0016] In this scheme, the steam pressure at the steam outlet of the newly added external steam cooler is higher than the final stage extraction steam pressure of the high-pressure cylinder, which makes the steam pressure entering the newly added final stage high-pressure heater higher than the final stage extraction steam pressure of the high-pressure cylinder, thereby achieving supplementary heating of the feedwater that has been heated by the existing final stage high-pressure heater at the newly added final stage high-pressure heater.

[0017] Preferably, the booster module is equipped with a new steam extraction isolation valve in its pipeline, and the new steam extraction isolation valve is located at the front end of the steam compressor.

[0018] In this solution, a new extraction steam isolation valve is installed in the booster module and positioned upstream of the steam compressor. The new extraction steam isolation valve regulates the fluid flow rate entering the booster module. Furthermore, in the event of a malfunction in the steam compressor, the new external steam cooler, or other equipment, the new extraction steam isolation valve can be closed to prevent steam from entering the booster module, ensuring system safety and improving system operational flexibility.

[0019] Preferably, the steam below the target extraction pressure level originates from a portion of the final stage extraction steam from the high-pressure cylinder, the inlet of the booster module is connected to the extraction steam pipeline via a pipe, and the interface of the booster module connected to the extraction steam pipeline is located upstream of the extraction steam isolation valve.

[0020] In the scheme, the inlet of the pressurizing module is connected to the existing final-stage high-pressure heating extraction steam pipeline through a pipeline, part of the final-stage extraction steam of the high-pressure cylinder enters the existing final-stage high-pressure heater to heat the feed water, and the other part of the final-stage extraction steam of the high-pressure cylinder is pressurized by the pressurizing module and then enters the newly added external steam cooler and the newly added final-stage high-pressure heater in sequence to supplementally heat or secondarily heat the feed water heated by the existing final-stage high-pressure heater, so as to improve the inlet feed water temperature of the unit under the deep peak shaving condition; the interface of the pressurizing module connected to the extraction steam pipeline is located upstream of the extraction steam isolation valve, so that part of the final-stage extraction steam is led out in front of the inlet of the extraction steam isolation valve, and the extraction steam isolation valve can control the part of the final-stage extraction steam of the high-pressure cylinder to enter the existing final-stage high-pressure heater to heat the feed water, that is, even when the existing final-stage high-pressure heater cannot work, the extraction steam isolation valve is closed, and the normal work of the pressurizing module and the newly added final-stage high-pressure heater is not affected, thereby improving the flexibility of the unit operation.

[0021] Preferably, the steam with a pressure lower than the target extraction steam pressure level is the extraction steam in the regenerative system or the steam in the reheating system or the steam in the superheater system of the unit or other units.

[0022] In the scheme, the steam with a pressure lower than the target extraction steam pressure level is optimized to be the extraction steam in the regenerative system or the steam in the reheating system or the steam in the superheater system of the unit or other units, which improves the flexibility of the unit operation on the premise that the outlet steam pressure of the steam compressor is higher than the final-stage extraction steam of the high-pressure cylinder.

[0023] Preferably, a circulating pump is arranged in the downcomer connected between the steam drum and the header in the boiler.

[0024] In the scheme, the circulating pump arranged in the downcomer connected between the steam drum and the header in the boiler enhances the driving force of the working medium circulation, so that the water at the lower part of the steam drum flows to the header through the downcomer smoothly.

[0025] Preferably, the main steam throttling assembly is a high-pressure cylinder inlet valve group or a regulating valve.

[0026] In the scheme, the main steam throttling assembly is a high-pressure cylinder inlet valve group or a regulating valve, which facilitates the adjustment of the pressure and flow of the main steam.

[0027] Preferably, the system configuration is configured to throttle the main steam by using the main steam throttling assembly to maintain a certain feed water pressure and keep a certain subcooling degree of the economizer outlet feed water.

[0028] In the scheme, the steam lower than the target extraction pressure level is pressurized by the booster module, then enters the newly added external steam cooler and the newly added last-stage high-pressure heater in sequence to supplementally heat the feed water, so as to improve the feed water temperature into the furnace of the unit under the deep peak shaving condition, the main steam is throttled by operating the main steam throttling assembly to maintain a certain feed water pressure, and the feed water at the economizer outlet is kept at a certain supercooling degree.

[0029] Preferably, a throttling assembly is arranged in the feed water or steam pipeline from the economizer outlet to the high-pressure cylinder inlet, and the throttling assembly is adjusted to maintain a certain feed water pressure.

[0030] In the scheme, a throttling assembly such as a regulating valve can also be arranged in the feed water pipeline or steam pipeline from the economizer outlet to the high-pressure cylinder inlet, and the throttling assembly is adjusted to maintain a certain feed water pressure, so as to keep the feed water at the economizer outlet at a certain supercooling degree.

[0031] The positive progress effect of the utility model lies in: the existing last-stage high-pressure feed water outlet in the feed water pipeline is sequentially provided with a newly added last-stage high-pressure heater and a newly added external steam cooler, the steam side inlet of the newly added external steam cooler is connected with a booster module, the inlet of the booster module is connected with steam lower than the target extraction pressure level, the steam side outlet of the newly added external steam cooler is communicated with the steam inlet of the newly added last-stage high-pressure heater, the steam lower than the target extraction pressure level is pressurized by the booster module and then supplemented with heat twice in the newly added external steam cooler and the newly added last-stage high-pressure heater respectively, so as to improve the feed water temperature into the furnace of the unit and maintain a certain feed water pressure to keep the feed water at the economizer outlet at a certain supercooling degree, realize the continuous and stable operation of the denitration system of the unit under the deep peak shaving condition, avoid the sharp rise of the energy consumption of the unit, and effectively improve the operation economy of the unit. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a system schematic diagram of the existing boiler feed water heating.

[0033] Figure 2 It is a system configuration schematic diagram of the coal-fired unit adaptive flexible operation according to an embodiment of the utility model. DETAILED DESCRIPTION

[0034] The utility model will be explained more clearly and completely by combining with the preferred embodiments and the drawings.

[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 a water-cooled wall. 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 wall, and then returns to the steam drum. The deaerator system includes a deaerator, a pre-pump, and a feedwater pump. The high-pressure cylinder uses a full-circumference steam inlet method and is not equipped with a regulating stage. The feedwater inlet of the existing final-stage high-pressure heater is connected to the feedwater outlet of the deaerator system, and the feedwater outlet of the existing final-stage high-pressure heater is connected to the feedwater inlet of the boiler. The steam outlet of the boiler is connected to the high-pressure cylinder through a main steam pipeline, and the steam inlet of the existing final-stage high-pressure heater is connected to the extraction port of the high-pressure cylinder through an extraction steam pipeline. A main steam throttling component is installed on the main steam pipeline, and an extraction steam isolation valve is arranged on the steam inlet pipeline.

[0036] This utility model provides a system configuration for coal-fired power units to adapt to flexible operation, such as... Figure 2 As shown, it includes: a boiler, a deaeration 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 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 full-circumference steam inlet method and is not equipped with a regulating stage. In the feedwater pipelines, along the feedwater flow direction, the deaeration system, the existing final-stage high-pressure heater, the newly added final-stage high-pressure heater, and the newly added external... The newly added external steam cooler 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 inlet of the existing final-stage high-pressure heater. A main steam throttling component is installed on the main steam pipeline, and an extraction steam isolation valve is installed on the extraction steam pipeline. A booster module is connected to the steam-side inlet of the newly added external steam cooler. The inlet of the booster module receives steam at a pressure lower than the target extraction steam pressure level, and the steam-side outlet of the newly added external steam cooler is connected to the inlet of the newly added final-stage high-pressure heater. The target extraction steam pressure level can be understood as the steam that, if using the existing boiler feedwater heating system (i.e., without a booster module, directly heats the feedwater to the required temperature and pressure in the existing final-stage high-pressure heater), would be present.

[0037] The feed water is sent to the boiler feed water inlet after passing through the deaeration system, the existing last-stage high-pressure heater, the newly-added last-stage high-pressure heater and the newly-added external steam cooler in sequence, the steam lower than the target extraction pressure level is first sent to the newly-added external steam cooler after being pressurized by the pressurizing module for supplementary heating of the feed water, and then is sent to the newly-added last-stage high-pressure heater for supplementary heating of the feed water heated by the existing last-stage high-pressure heater, that is, on the basis of the existing last-stage high-pressure heater being normally put into use for heating of the feed water, the steam lower than the target extraction pressure level is introduced to be pressurized by the pressurizing module and then is twice supplementary heated in the newly-added external steam cooler and the newly-added last-stage high-pressure heater respectively, so as to improve the inlet boiler feed water temperature of the unit, while maintaining a certain feed water pressure to keep the feed water at the economizer outlet in a certain supercooling degree, so as to improve the inlet boiler feed water temperature of the unit in the deep peak shaving condition, and then improve the economizer inlet water temperature, the economizer outlet water temperature, the economizer outlet flue gas temperature and the steam temperature at the drum outlet, so as to finally realize the continuous and stable operation of the denitration system of the unit in the deep peak shaving condition, avoid the sharp rise of the unit energy consumption and effectively improve the unit operation economy.

[0038] Figure 2 The high-pressure cylinder steam inlet valve group is arranged on the main steam pipeline, and of course can be other main steam throttling components, such as a regulating valve, for regulating the pressure and flow of the main steam. It needs to be emphasized here that when the steam lower than the target extraction pressure level is pressurized in the pressurizing module and then enters the newly-added external steam cooler for supplementary heating of the feed water and flows out of the newly-added external steam cooler and then enters the newly-added last-stage high-pressure heater for supplementary heating of the feed water to improve the inlet boiler feed water temperature of the unit in the deep peak shaving condition, the original high-pressure cylinder steam inlet valve group can also be used to throttle the main steam by operating the high-pressure cylinder steam inlet valve group, with the purpose of maintaining a certain feed water pressure and keeping the feed water at the economizer outlet in a certain supercooling degree to ensure the normal operation of the unit. Of course, in other embodiments, a throttling component, such as a regulating valve, can also be arranged in the feed water or steam pipeline system from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feed water pressure and keep the feed water at the economizer outlet in a certain supercooling degree.

[0039] As shown in Figure 2 The steam compressor is arranged in the pipeline of the pressurizing module and is used to pressurize the steam lower than the target extraction pressure level entering the pressurizing module, so that the pressure of the steam lower than the target extraction pressure level after being pressurized by the steam compressor is higher than the pressure of the last-stage extraction steam of the high-pressure cylinder, and the pressure of the steam after being compressed by the steam compressor and then entering the newly-added external steam cooler is higher than the pressure of the last-stage extraction steam entering the existing last-stage high-pressure heater, so as to ensure that the feed water is heated to a higher temperature to improve the inlet boiler feed water temperature of the unit in the deep peak shaving condition.

[0040] Further, the steam pressure at the outlet of the steam side of the newly added external steam cooler is higher than the last stage extraction steam pressure of the high pressure cylinder, so that the steam pressure entering the newly added last stage high pressure heater is higher than the last stage extraction steam pressure of the high pressure cylinder, thereby realizing supplementary heating of the feed water heated by the existing last stage high pressure heater at the newly added last stage high pressure heater.

[0041] As shown in Figure 2 The newly added extraction isolation valve is arranged in the pipeline of the pressurizing module and located at the front end of the steam compressor. Arranging the newly added extraction isolation valve upstream of the steam compressor can adjust the flow of fluid entering the pressurizing module, and can also prevent steam from entering the pressurizing module by closing the newly added extraction isolation valve when the steam compressor, the newly added external steam cooler and other equipment fail, thereby ensuring the safety of system operation and improving the flexibility of system operation.

[0042] As shown in Figure 2 The steam with a pressure lower than the target extraction steam pressure level is derived from part of the last stage extraction steam of the high pressure cylinder, the inlet of the pressurizing module is connected to the extraction pipeline through a pipeline, and the interface of the pressurizing module connected to the extraction pipeline is located upstream of the extraction isolation valve. The inlet of the pressurizing module is connected to the extraction pipeline of the existing last stage high pressure heater through a pipeline, part of the last stage extraction steam of the high pressure cylinder enters the existing last stage high pressure heater to heat the feed water, and the other part of the last stage extraction steam of the high pressure cylinder is pressurized by the pressurizing module and then enters the newly added external steam cooler and the newly added last stage high pressure heater in sequence to supplementally heat or secondarily heat the feed water heated by the existing last stage high pressure heater, so as to improve the inlet feed water temperature of the unit under deep peak regulation condition; the interface of the pressurizing module connected to the extraction pipeline is located upstream of the extraction isolation valve, so that part of the last stage extraction steam is led out at the front end of the inlet of the extraction isolation valve, and the extraction isolation valve can control the part of the last stage extraction steam of the high pressure cylinder entering the existing last stage high pressure heater to heat the feed water, that is, even when the existing last stage high pressure heater cannot work, closing the extraction isolation valve will not affect the normal work of the pressurizing module and the newly added last stage high pressure heater, thereby improving the flexibility of unit operation.

[0043] Of course, in other embodiments, the steam with a pressure lower than the target extraction steam pressure level is derived from the regenerative extraction steam in the unit or other units or the steam in the reheating system or the steam in the superheater system. Optimizing the steam with a pressure lower than the target extraction steam pressure level to the regenerative extraction steam in the unit or other units or the steam in the reheating system or the steam in the superheater system improves the flexibility of the unit operation under the premise that the steam pressure at the outlet of the steam compressor is higher than the last stage extraction steam pressure of the high pressure cylinder.

[0044] Although in Figure 2In the middle, the water in the boiler, in the drum directly through the downcomer to the header, of course, in other embodiments, the downcomer connected between the drum and the header can also be provided with a circulating pump to enhance the driving force of the working fluid circulation flow, so that the water at the lower part of the drum flows to the header through the downcomer.

[0045] The system configuration that the coal power unit is adapted to flexible operation provided by the utility model, under the deep peak regulation working condition, taking 20% THA working condition as an example, the unit boiler feed water temperature can be raised to 75% THA or even 100% THA feed water temperature level;With the improvement of the unit boiler feed water temperature, the economizer inlet water temperature is improved, and then the economizer outlet water temperature is improved, and the economizer outlet flue gas temperature is improved and meets the denitration inlet flue gas temperature demand;While the economizer outlet water temperature is improved, a certain feed water pressure is maintained, so that the economizer outlet feed water maintains a certain supercooling degree;With the improvement of the feed water pressure, the steam water mixture pressure in the steam drum is also improved, the wet saturated steam temperature at the upper part of the steam drum is also improved, and the main steam temperature can also be improved;With the improvement of the main steam temperature, the main steam quantity and the reheated steam quantity ratio, the cold reheated steam and the hot reheated steam temperature are improved, so that the unit energy consumption can be avoided to rise greatly, and the unit operation economy can be effectively improved.

[0046] Taking the data of 20% THA working condition of the adjusting stage of a 300MW subcritical unit as an example, the high pressure cylinder of the unit adopts full circumference steam admission mode.

[0047] Existing scheme: main generator load 60MW, existing last stage high pressure heater inlet steam pressure, temperature parameter 1.29MPa, 370℃ and outlet feed water pressure, temperature parameter 8.5MPa, 192℃, economizer outlet water temperature 211℃, supercooling degree 107.3℃, under-enthalpy 521kJ / kg, economizer outlet flue gas temperature 272℃, and the denitration system cannot be put into use.

[0048] The embodiment scheme: main generator load 60MW, existing last stage extraction pressure, temperature parameter 0.97MPa, 348℃, the newly added last stage high pressure heater inlet steam pressure, temperature parameter 3.53MPa, 399℃ after being pressurized by the steam compressor and being temperature reduced by the newly added external steam cooler and outlet feed water pressure, temperature parameter 10.5MPa, 246℃, the water side temperature rise of the newly added external steam cooler is 6℃, the economizer outlet water temperature is 275℃, the supercooling degree is 39.6℃, the under-enthalpy is 221kJ / kg, the economizer outlet flue gas temperature is 340℃, the denitration system is stably and continuously put into use, and the unit operation economy is improved due to the relative rise of the feed water temperature.

[0049] Although the specific embodiments of the present application are described above, those skilled in the art should understand that this is only an example, the protection scope of the present application 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 the present application, but these changes and modifications all fall within the protection scope of the present application.

Claims

1. A system configuration for coal-fired power plant adaptive flexibility operation, comprising: The boiler, oxygen removal system, high-pressure cylinder, existing last-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 flows to the header through the downcomer, and then returns to the steam drum after being heated by the water cooling wall; the high-pressure cylinder adopts a full-circumferential admission mode and is not provided with an adjusting stage; in the feedwater pipeline, the oxygen removal system, the existing last-stage high-pressure heater, the newly-added last-stage high-pressure heater and the newly-added external steam cooler are sequentially arranged along the feedwater flow direction; 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 last-stage high-pressure heater; the main steam pipeline is provided with a main steam throttling assembly, and the steam extraction pipeline is provided with a steam extraction isolation valve; the steam-side inlet of the newly-added external steam cooler is connected with a pressure boosting module, the inlet of the pressure boosting module is connected to steam at a pressure lower than a target steam extraction pressure level, and the steam-side outlet of the newly-added external steam cooler is communicated with the steam inlet of the newly-added last-stage high-pressure heater.

2. The system configuration of claim 1, wherein, The pipeline of the pressure boosting module is provided with a steam compressor, and the steam compressor is used to boost the steam at a pressure lower than the target steam extraction pressure level entering the pressure boosting module, so that the steam at a pressure lower than the target steam extraction pressure level is boosted by the steam compressor and has a pressure higher than that of the last-stage steam extraction of the high-pressure cylinder.

3. The system configuration of claim 2, wherein, The steam pressure at the steam-side outlet of the newly-added external steam cooler is higher than the last-stage steam extraction pressure of the high-pressure cylinder.

4. The system configuration of claim 3, wherein, The pipeline of the pressure boosting module is provided with a newly-added steam extraction isolation valve, and the newly-added steam extraction isolation valve is located at the front end of the steam compressor.

5. The system configuration of claim 4, wherein, The steam at a pressure lower than the target steam extraction pressure level is derived from part of the last-stage steam extraction of the high-pressure cylinder, the inlet of the pressure boosting module is connected to the steam extraction pipeline through a pipeline, and the interface of the pressure boosting module connected to the steam extraction pipeline is located upstream of the steam extraction isolation valve.

6. The system configuration of claim 4, wherein, The steam at a pressure lower than the target steam extraction pressure level is derived from regenerative steam extraction or steam in a reheat system or steam in a superheater system in the unit or other units.

7. The system configuration of claim 1, wherein, In the boiler, a circulating pump is arranged in the downcomer connected between the steam drum and the header.

8. The system configuration of claim 1, wherein The main steam throttling assembly is a high-pressure cylinder admission valve group or an adjusting valve.

9. The system configuration of any one of claims 1-8, wherein, The system configuration is configured to throttle the main steam by using the main steam throttling assembly to maintain a certain feedwater pressure and keep the feedwater at the outlet of the economizer at a certain subcooling degree.

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

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