Flexible operation system configuration based on feed water heating

Abstract

The utility model provides a flexible operation system configuration based on feed water heating, 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 in 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 a temperature reduction module, steam with the pressure grade higher than that of regenerative steam extraction of the high-pressure cylinder is connected into an inlet of the temperature reduction module, and a steam side outlet of the newly-added external steam cooler communicates with a steam inlet of an existing final-stage high-pressure heater. 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] The utility model relates to the technical field of power generation, especially to a flexible operation system configuration based on feedwater heating. BACKGROUND

[0002] At present, the (ultra) supercritical unit with high parameters, large capacity and high efficiency and low carbon has become the mainstream of the selection of newly-built units in thermal power plants.

[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, 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 300MW subcritical unit as an example, the high-pressure cylinder adopts full-circumferential admission, and no regulating stage is configured. The load range of the regional power grid is 40%-100%THA. However, with the rapid development of new energy, the regional power grid 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 units that need to participate in deep peak regulation, such as load change range of 20%-100%THA, among which the deep peak regulation load range is 20%-30%THA, or even lower, the high-pressure cylinder of the subcritical unit adopts full-circumferential admission, and no regulating stage is configured, which will face the following problems:

[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℃), and 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 increases from 25mg / Nm 3 to 200mg / Nm 3 , which is much higher than the standard value of 50mg / Nm 3 ).

[0007] (2) The temperature at the outlet of the boiler drum drops significantly, the main and reheat steam temperatures will decrease significantly, the energy consumption of the unit will increase significantly, and the operating 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, and avoids the significant increase of energy consumption and the significant decrease of operating economy, has become a problem to be solved. INVENTION CONTENTS

[0009] The utility model wants to solve the technical problem that is to overcome the defect that the denitration system will not be able to normally operate, the unit energy consumption rises greatly, the operation economy greatly drops under the depth peak shaving condition of subcritical unit, provides a kind of flexible operation system configuration based on feedwater heating.

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

[0011] The utility model provides a kind of flexible operation system configuration based on feedwater heating, it includes boiler, deaerating system, high pressure cylinder, existing last stage high pressure heater, feedwater pipeline and steam pipeline, it is characterized in that, the 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 back to steam drum by water-cooled wall;The high pressure cylinder adopts full circumferential admission;Deaerating system, existing last stage high pressure heater, newly added external steam cooler are sequentially arranged in the feedwater pipeline, and the feedwater outlet of newly added external steam cooler is connected with the boiler feedwater inlet;The steam pipeline includes main steam pipeline connected between the boiler steam outlet and high pressure cylinder gas inlet and steam extraction pipeline connected between the high pressure cylinder steam extraction port and the gas inlet of existing last stage high pressure heater;Main steam throttling assembly is arranged on the main steam pipeline, and steam extraction isolation valve is arranged on the steam extraction pipeline;The steam side inlet of newly added external steam cooler is connected with temperature reducing module, the inlet of temperature reducing module is connected with the steam of higher pressure grade than the regenerative steam extraction of high pressure cylinder, and the steam side outlet of newly added external steam cooler is communicated with the gas inlet of existing last stage high pressure heater.

[0012] In the scheme, an oxygen removal system, an existing last-stage high-pressure heater and a 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 boiler feedwater inlet, 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, the steam side outlet of the newly-added external steam cooler is communicated with the steam inlet of the existing last-stage high-pressure heater, the steam of the higher pressure grade than the regenerative extraction steam of the high-pressure cylinder is first heated to the feedwater in the newly-added external steam cooler after being desuperheated by the desuperheating module, and then the steam at the steam outlet of the newly-added external steam cooler is sent to the existing last-stage high-pressure heater to heat the feedwater located at the front end of the newly-added external steam cooler. In the whole process, the steam out of the desuperheating module first heats the feedwater at the rear end in the newly-added external steam cooler, and then the steam at the steam side outlet of the newly-added external steam cooler is sent to the existing last-stage high-pressure heater to heat the feedwater at the front end. This not only improves the inlet feedwater temperature of the unit under deep peak-regulation conditions, but also improves the heat utilization rate. With the improvement of the inlet feedwater temperature of the unit, the inlet water temperature of the economizer is improved, and then the outlet water temperature of the economizer is improved, and the outlet flue gas temperature of the economizer is improved and meets the requirement of the inlet flue gas temperature of the denitration.

[0013] Preferably, the desuperheating module comprises an isolation valve, a pressure reducing valve and a desuperheater connected in sequence by pipelines, and the desuperheater is connected to desuperheating water.

[0014] In the scheme, the steam of a higher pressure grade than the regenerative extraction steam of the high-pressure cylinder is desuperheated and pressure-reduced in the desuperheating module by the pressure reducing valve and mixed with desuperheating water in the desuperheater, so as to realize the desuperheating and pressure-reducing of the steam of a higher pressure grade than the regenerative extraction steam of the high-pressure cylinder, and ensure the safe operation of the system.

[0015] Preferably, the steam side outlet of the newly-added external steam cooler is connected to the steam inlet of the existing last-stage high-pressure heater by a pipeline, or the steam side outlet of the newly-added external steam cooler is communicated with the extraction pipeline by a pipeline, and the communication port is located downstream of the extraction isolation valve.

[0016] In the scheme, the steam side outlet of the newly-added external steam cooler is directly connected to the steam inlet of the existing last-stage high-pressure heater by a pipeline, or the steam side outlet of the newly-added external steam cooler is communicated with the extraction pipeline by a pipeline, and the communication port is located downstream of the extraction isolation valve. When the outlet steam of the newly-added external steam cooler is used to heat the feedwater in the existing last-stage high-pressure heater, the extraction isolation valve is closed to realize the replacement of the outlet steam of the newly-added external steam cooler with the regenerative extraction steam of the existing last-stage high-pressure heater.

[0017] Preferably, the main steam throttling assembly is a high-pressure cylinder inlet valve group or a regulating valve.

[0018] In the present scheme, the main steam throttling assembly adopts a high-pressure cylinder inlet valve group or a regulating valve to conveniently regulate the pressure and flow of the main steam.

[0019] Preferably, when the steam at the steam-side outlet of the newly added external steam cooler is used to heat the feed water in the existing final high-pressure heater, the extraction isolation valve on the extraction pipeline of the existing final 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 pressure of the high-pressure cylinder.

[0020] In the present scheme, the steam pressure at the steam-side outlet of the newly added external steam cooler is higher than the regenerative extraction pressure of the high-pressure cylinder, so that the steam pressure entering the existing final high-pressure heater is higher than the regenerative extraction pressure of the high-pressure cylinder, thereby further increasing the temperature of the boiler feed water.

[0021] Preferably, a circulating pump is arranged in the downcomer connected between the steam drum and the header in the boiler.

[0022] In the present scheme, the circulating pump arranged in the downcomer connected between the steam drum and the header 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.

[0023] Preferably, the steam of a higher pressure level than the regenerative extraction of the high-pressure cylinder is sourced from the main steam in the unit or the steam in the superheater system or the mixed steam of any one of the main steam and the steam in the superheater system in the unit and the regenerative extraction or the reheated steam of the unit.

[0024] Alternatively, the steam of a higher pressure level than the regenerative extraction 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.

[0025] In the present scheme, the steam in the unit is fully utilized, and multiple schemes are provided for the source of the steam of a higher pressure level than the regenerative extraction of the high-pressure cylinder. On the premise that the steam entering the newly added external steam cooler is higher than the existing regenerative extraction, the operation flexibility of the unit is improved. Alternatively, the inlet of the desuperheating module is connected to the main steam pipeline, part of the main steam is introduced into the desuperheating module, and the steam after being desuperheated and depressurized is sent to the newly added external steam cooler to heat the feed water, so as to improve the temperature of the boiler feed water in the deep peak shaving condition.

[0026] Preferably, the steam of a higher pressure level than the regenerative extraction of the high-pressure cylinder is sourced from the main steam in another unit or the steam in the superheater system or the mixed steam of any one of the main steam and the steam in the superheater system in another unit and the regenerative extraction or the reheated steam.

[0027] In the scheme, steam of other units is utilized to improve the operation flexibility of the unit and optimize the thermal cycle of the whole system under the premise that the steam entering the newly added external steam cooler is higher than the existing regenerative extraction steam.

[0028] Preferably, the flexible operation system is configured to throttle the main steam by using a main steam throttling component to maintain a certain feed water pressure and keep the feed water at the economizer outlet at a certain supercooling degree.

[0029] In the scheme, the steam of a higher pressure grade than the regenerative extraction steam of the high-pressure cylinder is reduced in temperature and pressure in the temperature reducing module and then enters the newly added external steam cooler to supplement the heating of the feed water and enters the existing final high-pressure heater after the newly added external steam cooler to heat the feed water to improve the feed water temperature of the unit under the deep peak shaving condition, the original high-pressure cylinder inlet valve group is used to throttle the main steam by operating the high-pressure cylinder inlet valve group, and the purpose is to maintain a certain feed water pressure and keep the feed water at the economizer outlet at a certain supercooling degree.

[0030] Preferably, a throttling component is arranged in the feed water pipeline or steam pipeline from the economizer outlet to the high-pressure cylinder inlet, and the throttling component is adjusted to maintain a certain feed water pressure.

[0031] In the scheme, a throttling component 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 to maintain a certain feed water pressure, so that the feed water at the economizer outlet is kept at a certain supercooling degree.

[0032] The positive progress effect of the utility model lies in: on the basis of the existing boiler feed water heating system, an oxygen removal system, an existing final high-pressure heater and a newly added external steam cooler are arranged in the feed water pipeline in sequence, the feed water outlet of the newly added external steam cooler is connected with the boiler feed water inlet, the steam side inlet of the newly added external steam cooler is connected with a temperature reducing module, the inlet of the temperature reducing module is connected with steam of a higher pressure grade than the regenerative extraction steam of the high-pressure cylinder, the steam side outlet of the newly added external steam cooler is communicated with the steam inlet of the existing final high-pressure heater, the steam out of the temperature reducing module is first heated to the feed water at the rear end in the newly added external steam cooler and then the steam at the steam side outlet of the newly added external steam cooler is sent to the existing final high-pressure heater to heat the feed water at the front end, which not only improves the feed water temperature of the unit under the deep peak shaving condition, but also improves the heat utilization rate; with the improvement of the feed water temperature of the unit, the inlet water temperature of the economizer is improved, the outlet water temperature of the economizer is improved, and the outlet flue gas temperature of the economizer is improved and meets the requirement of the inlet flue gas temperature of denitration. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1A schematic diagram of a system for heating boiler feed water in the prior art.

[0034] Figure 2 A schematic diagram of a flexible operation system configuration based on feed water heating according to an embodiment of the present application. DETAILED DESCRIPTION

[0035] The present application will be described in greater detail below with reference to the preferred embodiments and accompanying drawings.

[0036] Figure 1 A schematic diagram of a system for heating boiler feed water in the prior art, which comprises a boiler, an oxygen removal system, a high-pressure cylinder and an existing final-stage high-pressure heater, the boiler comprising an economizer, a steam drum, a superheater, a header, a downcomer and a water-cooled wall; the economizer, the steam drum and the superheater are sequentially connected by pipelines, water at the lower part of the steam drum is heated by the water-cooled wall after passing through the downcomer and the header and then returns to the steam drum, the oxygen removal system comprises an oxygen remover, a pre-pump and a feed water pump, the high-pressure cylinder adopts a full-circumferential-steam-admission mode and is not configured with an adjusting stage, the feed water inlet of the existing final-stage high-pressure heater is communicated with the feed water outlet of the oxygen removal system, the feed water outlet of the existing final-stage high-pressure heater is communicated with the feed water inlet of the boiler, the steam outlet of the boiler is communicated with the high-pressure cylinder through a main steam pipeline, and the steam admission pipe of the existing final-stage high-pressure heater is communicated with the steam extraction port of the high-pressure cylinder through a steam extraction pipeline; a main steam throttling assembly is arranged on the main steam pipeline, and a steam extraction isolation valve is arranged on the steam admission pipeline.

[0037] When the system is running, the feed water at the outlet of the oxygen remover is sequentially pressurized by the pre-pump and the feed water pump and then enters the existing final-stage high-pressure heater for heating, the heated feed water enters the boiler, is further heated by the economizer and then enters the steam drum, and the steam-water mixture is separated in the steam drum, wherein: the water at the lower part of the steam drum is heated by the water-cooled wall after passing through the downcomer and the header and then returns to the steam drum, the wet saturated steam at the upper part of the steam drum enters the superheater and other heating surfaces for heating, and finally the main steam enters the high-pressure cylinder for work. The high-pressure cylinder adopts a full-circumferential-steam-admission mode and is not configured with an adjusting stage, and the main steam throttling assembly arranged on the main steam pipeline adjusts the pressure and flow of the main steam.

[0038] In order to overcome the defects that the denitration system cannot normally operate, the energy consumption of the unit greatly increases and the operation economy greatly decreases of the subcritical unit under the deep peak shaving working condition, the present application provides a flexible operation system configuration based on feed water supplementary heating, as shown in Figure 2As shown, in this flexible operation system configuration, the boiler includes an economizer, steam drum, superheater, header, downcomer, and water-cooled walls. The economizer, steam drum, and superheater are connected sequentially via 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. 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. A main steam throttling component is installed on the main steam pipeline. An extraction steam isolation valve is arranged on the extraction steam pipeline. A desuperheating module is connected to the steam-side inlet of the newly added external steam cooler. The inlet of the desuperheating module is connected to... Steam with a higher pressure rating than the regenerative extraction steam of the high-pressure cylinder is introduced. The steam-side outlet of the newly added external steam cooler is connected to the extraction steam pipeline through a pipeline, and the connection port is located downstream of the extraction steam isolation valve. The steam coming out of the desuperheating module first heats the feedwater at the downstream end at the newly added external steam cooler, and then the steam at 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 at the front 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, 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.

[0039] 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.

[0040] like Figure 2 As shown, 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.

[0041] 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.

[0042] When the steam at the steam side outlet of the newly added external steam cooler enters the existing final stage high pressure heater to heat the feed water, the extraction isolation valve on the extraction pipeline 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 pressure of the high pressure cylinder, so that the steam pressure entering the existing final stage high pressure heater is higher than the regenerative extraction pressure of the high pressure cylinder, thereby further increasing the feed water temperature entering the boiler.

[0043] Although in Figure 2 the water in the boiler in the steam drum is directly passed to the header through the downcomer, of course, in other embodiments, a circulating pump can also be arranged in the downcomer connected between the steam drum and the header in the boiler to enhance the driving force of the working fluid circulation flow, so that the water at the lower part of the steam drum flows to the header through the downcomer smoothly.

[0044] Figure 2 The high pressure cylinder steam inlet valve group arranged on the main steam pipeline in the embodiment is a high pressure cylinder steam inlet valve group, and of course, an adjusting valve can also be selected, and the high pressure cylinder steam inlet valve group adjusts the pressure and flow of the main steam. It needs to be emphasized here that when the steam at a higher pressure level than the regenerative extraction steam of the high pressure cylinder is reduced in temperature and pressure in the desuperheating module, enters the newly added external steam cooler to supplement the heating of the feed water, and then enters the existing final stage high pressure heater from the newly added external steam cooler to heat the feed water to increase the feed water temperature entering the boiler in the deep peak regulation condition, the high pressure cylinder steam inlet valve group is operated to throttle the main steam using the original high pressure cylinder steam inlet valve group, and the purpose is to maintain a certain feed water pressure and keep the feed water at the economizer outlet at a certain degree of supercooling, so as to ensure the normal operation of the unit.

[0045] Of course, in other embodiments, a throttling component such as an adjusting valve can also be arranged in the feed water or steam pipeline system from the economizer outlet to the high pressure cylinder inlet, so as to maintain a certain feed water pressure and keep the feed water at the economizer outlet at a certain degree of supercooling.

[0046] As Figure 2As shown, the steam source of 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 enters the desuperheater in sequence through the isolation valve and the pressure reducing valve in the desuperheating module to mix with the desuperheating water, and then is sent to the newly added external steam cooler to supplementally heat the feed water, and then the steam at the steam outlet of the external steam cooler is sent to the existing final high-pressure heater to heat the feed water, so as to improve the inlet feed water temperature of the unit under the deep peak shaving condition. Of course, in other embodiments, the steam source of higher pressure level than the regenerative extraction steam of the high-pressure cylinder can be the main steam in the unit or the steam in the superheater system or the mixed steam of any one of the main steam and the steam in the superheater system of the unit and the regenerative extraction steam or the reheated steam of the unit, so that the steam of the unit can be fully utilized, and multiple schemes of the steam source of higher pressure level than the regenerative extraction steam of the high-pressure cylinder are provided, the operation flexibility of the unit is improved under the premise that the steam entering the external steam cooler is higher than the existing regenerative extraction steam, and the thermal cycle of the whole system is optimized.

[0047] The flexible operation system configuration based on feed water heating provided by the utility model can improve the inlet feed water temperature of the unit to 75% THA or even 100% THA under the deep peak shaving condition, for example, under the 20% THA condition, further, with the improvement of the inlet feed water temperature of the unit, the inlet water temperature of the economizer is improved, and then the outlet water temperature of the economizer is improved, and the outlet flue gas temperature of the economizer is improved and meets the requirement of the inlet flue gas temperature of the denitration, further, the outlet feed water of the economizer maintains a certain degree of supercooling while the outlet water temperature of the economizer is improved and a certain feed water pressure is maintained, further, with the improvement of the feed water pressure, the pressure of the steam-water mixture in the steam drum is also improved, the temperature of the wet saturated steam at the upper part of the steam drum is also improved, and the main steam temperature can also be improved, further, with the improvement of the main steam temperature, the main steam quantity and the ratio of the reheated steam quantity, the cold reheated steam temperature and the hot reheated steam temperature are also improved, so that the unit energy consumption can be greatly reduced, and the operation economy of the unit is effectively improved.

[0048] Taking a 300MW subcritical unit as an example, the high-pressure cylinder of the unit adopts full-circumferential admission, and no regulating stage is configured, and the data of the unit under the 20% THA condition is taken as an example.

[0049] The existing scheme: the main generator load is 60MW, the existing final stage high pressure inlet steam pressure and temperature parameters are 1.29MPa and 370℃, the outlet feed water pressure and temperature parameters are 8.5MPa and 192℃, the economizer outlet water temperature is 211℃, the supercooling degree is 107.3℃, the enthalpy deficit is 521kJ / kg, the economizer outlet flue gas temperature is 272℃, and the denitration system cannot be put into use.

[0050] The embodiment scheme: the main generator load is 60MW, the existing final stage high pressure inlet steam pressure and temperature parameters after temperature reduction by the external steam cooler are 3.71MPa and 423℃, the outlet feed water pressure and temperature parameters are 10.6MPa and 246℃, the water side temperature rise of the newly added external steam cooler is 6℃, the economizer outlet water temperature is 211℃, the supercooling degree is 107.3℃, the enthalpy deficit is 521kJ / kg, the economizer outlet flue gas temperature is 272℃, and the denitration system cannot be put into use. temperature 272℃, supercooling 43.3℃, enthalpy deficit 239.8kJ / kg, saving coal heater outlet flue gas temperature 339℃, denitration system The system is stable and continuously put into use, and the operation economy of the unit is improved due to the relative rise of the feed water temperature.

[0051] Although the specific embodiments of the utility model are described above, those skilled in the art should understand that this is only an example, the protection scope of the 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 the utility model, but these changes and modifications all fall within the protection scope of the utility model.

Claims

1. A flexible operation system configuration based on feedwater heating, comprising a boiler, a deaerating system, a high pressure cylinder, an existing last stage high pressure heater, a feedwater line, and a steam line, characterized in that, The boiler comprises an economizer, a steam drum, a superheater, a header, a downcomer and a water 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 heated by the water wall and returned to the steam drum; the high-pressure cylinder adopts a full-circumferential-steam-inlet mode; an oxygen removal system, an existing final-stage high-pressure heater and a newly-added external steam cooler are sequentially arranged in the feedwater pipeline, and a feedwater outlet of the newly-added external steam cooler is connected to a boiler feedwater inlet; the steam pipeline comprises a main steam pipeline connected between a boiler steam outlet and a high-pressure cylinder steam inlet, and a steam extraction pipeline connected between a high-pressure cylinder steam extraction port and a steam inlet of the existing final-stage high-pressure heater; a main steam throttling assembly is arranged on the main steam pipeline, and a steam extraction isolation valve is arranged on the steam extraction pipeline; a desuperheating module is connected to a steam-side inlet of the newly-added external steam cooler, an 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 a 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, 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 through a pipeline, or the steam-side outlet of the newly-added external steam cooler is communicated with the steam extraction pipeline through a pipeline, and a communication port is located downstream of the steam extraction isolation valve.

4. The flexible operating system configuration of claim 2, wherein, The main steam throttling assembly is a high-pressure cylinder steam inlet valve group or a regulating valve.

5. The flexible operating system configuration of claim 4, wherein, When steam at the steam-side outlet of the newly-added external steam cooler enters the existing final-stage high-pressure heater to heat feedwater, 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, 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.

6. The flexible operating system configuration of claim 5, wherein, In the boiler, a circulating pump is arranged in the downcomer connected between the steam drum and the header.

7. The flexible operating system configuration of claim 5, wherein, The steam of a higher pressure grade than the regenerative extraction steam of the high-pressure cylinder is sourced from main steam in the unit or steam in a superheater system of the unit or mixed steam of any one of the main steam and the steam in the superheater system of the unit and the regenerative extraction steam or the reheated steam of the unit; And / or, the steam of a higher pressure grade than the regenerative extraction steam of the high-pressure cylinder is sourced from main steam of the unit, and an inlet of the desuperheating module is connected to the main steam pipeline to introduce part of the main steam.

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

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

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