System configuration for coal power unit to adapt to deep peak regulation operation

Abstract

The utility model provides a system configuration for a coal power unit to adapt to deep peak regulation 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 a water supply outlet of an existing final-stage high-pressure heater on a water supply pipeline, and a steam side inlet of the newly added external steam cooler is connected with a pressurization module; the steam lower than the target steam extraction pressure level is introduced into an inlet of the pressurization module, and a steam side outlet of the newly-added external steam cooler is connected 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; and boiler dry-state operation of the unit under the deep peak regulation working condition is achieved, hydrodynamic force is kept stable, and a denitration system operates stably.

Description

TECHNICAL FIELD

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

[0002] At present, the ultra (ultra) supercritical unit with high parameters, large capacity, high efficiency and low carbon has become the mainstream of the new unit selection of thermal power plants. For the ultra (ultra) supercritical unit, its capacity is mainly 350MW, 660MW, 1000MW and so on, and there are also a small amount of 1200MW, 1350MW and so on.

[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 1000MW ultra-supercritical unit as an example, the load range of the regional power grid dispatching is 40%-100%THA, the feedwater flow of the boiler equipment corresponding to the load of the unit is higher than the minimum flow of the boiler to keep dry operation, so in the current normal load dispatching range, the boiler always keeps dry operation and there is no dry-wet state conversion process. However, with the rapid development of new energy, the regional power grid has informed the unit to operate in deep peak regulation, and the lower limit of load dispatching needs to be as low as 20%, the feedwater flow of the boiler equipment corresponding to 20% load of the unit has been lower than the minimum flow of the boiler to keep dry operation, and the boiler will have to be converted to wet operation.

[0005] For the ultra (ultra) supercritical unit that needs to participate in deep peak regulation, such as the load range of 20%-100%THA, among 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 boiler dry-wet state conversion is frequent, the control of coal, water and wind is very difficult, and the risk of non-stop of the boiler increases sharply;

[0007] (2) Under the condition of deep peak regulation, due to the increase of water underpotential at the inlet of water wall, the water power stability of the boiler water wall is poor, and the risk of water wall over-temperature explosion increases sharply;

[0008] (3) 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 operation temperature of the denitration catalyst, such as 300℃, the denitration system will not be able to operate normally, and it is predicted that the NOX emission will increase sharply and be much higher than the standard value, such as the emission index increases from 25mg / Nm3 to more than 200mg / Nm3, which is much higher than the standard value of 50mg / Nm3.

[0009] (4) In the wet operation condition of the boiler, if the water separated from the steam-water separator at the outlet of the water cooling wall of the boiler is directly discharged to the atmospheric flash tank, a large amount of working medium and energy will be lost, the energy consumption of the unit will be greatly increased, and the operation economy will be greatly reduced.

[0010] Therefore, how to maintain the dry operation of the boiler in the deep peak shaving condition, and keep the water power stability and the continuous and stable operation of the denitration system, has become a problem to be solved. Practical new type content

[0011] The technical problem to be solved by the utility model is how to maintain the dry operation of the boiler in the deep peak shaving condition, and keep the water power stability and the continuous and stable operation of the denitration system, and a system configuration for the coal-fired unit to adapt to the deep peak shaving operation is provided.

[0012] The utility model solves the above technical problem through the following technical scheme:

[0013] The utility model provides a system configuration for the coal-fired unit to adapt to the deep peak shaving operation, including a boiler, an oxygen removal system, a high-pressure cylinder, an existing last-stage high-pressure heater, a feedwater pipeline and a steam pipeline, the boiler includes a coal economizer, a water cooling wall and a superheater which are sequentially connected through pipelines, the high-pressure cylinder adopts full-circumferential admission, and is not configured with an adjusting stage, in the feedwater pipeline, the oxygen removal system, the existing last-stage high-pressure heater, a newly-added last-stage high-pressure heater and a newly-added external steam cooler are sequentially arranged along the feedwater flow direction, the steam pipeline includes 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, 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, 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 with steam lower than the 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.

[0014] In the scheme, a new last-stage high-pressure heater and a new external steam cooler are sequentially arranged at the existing last-stage high-pressure water outlet of the water supply pipeline, and the steam side inlet of the new external steam cooler is connected with a pressurizing module, the inlet of the pressurizing module is connected with steam at a pressure lower than a target steam extraction pressure level, the steam side outlet of the new external steam cooler is connected with the steam inlet of the new last-stage high-pressure heater, and the steam at a pressure lower than the target steam extraction pressure level is first supplied to the new external steam cooler for supplementary heating of the water in the new external steam cooler, and then is supplied to the new last-stage high-pressure heater for supplementary heating of the 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 used for heating the water, the steam at a pressure lower than the target steam extraction pressure level is pressurized by the pressurizing module and then is twice heated in the new external steam cooler and the new last-stage high-pressure heater, so as to increase the temperature of the water entering the boiler, and with the increase of the temperature of the water entering the boiler, the temperature of the water entering the economizer is increased, and then the temperature of the water exiting the economizer is increased, and the temperature of the flue gas exiting the economizer is increased and meets the requirement of the temperature of the flue gas entering the denitration device.

[0015] Preferably, a steam compressor is arranged in the pipeline of the pressurizing module, and the steam compressor is used for pressurizing the steam at a pressure lower than the target steam extraction pressure level entering the pressurizing module, so that the steam at a pressure lower than the target steam extraction pressure level is pressurized by the steam compressor and has a pressure higher than the pressure of the last-stage steam extraction of the high-pressure cylinder.

[0016] In the scheme, the steam compressor is arranged in the pressurizing module, and the steam at a pressure lower than the target steam extraction pressure level is pressurized by the steam compressor and then is sequentially supplied to the new external steam cooler and the new last-stage high-pressure heater for supplementary heating of the water. The steam at a pressure lower than the target steam extraction pressure level is pressurized by the steam compressor and has a pressure higher than the pressure of the last-stage steam extraction of the high-pressure cylinder, so that the steam pressurized by the steam compressor has a pressure higher than the pressure of the last-stage steam extraction of the high-pressure cylinder and is supplied to the new external steam cooler, and the pressure of the steam supplied to the new last-stage high-pressure heater is higher than the pressure of the last-stage steam extraction of the high-pressure cylinder, so as to ensure that the water is heated to a higher temperature and the temperature of the water entering the boiler is increased in the deep peak-regulation mode.

[0017] Preferably, the steam at the steam side outlet of the new external steam cooler has a pressure higher than the pressure of the last-stage steam extraction of the high-pressure cylinder.

[0018] In the scheme, the steam at the steam side outlet of the new external steam cooler has a pressure higher than the pressure of the last-stage steam extraction of the high-pressure cylinder, so that the steam supplied to the new last-stage high-pressure heater has a pressure higher than the pressure of the last-stage steam extraction of the high-pressure cylinder, and the water heated by the existing last-stage high-pressure heater is supplementary heated in the new last-stage high-pressure heater.

[0019] Preferably, a new steam extraction isolation valve is arranged in the pipeline of the pressurizing module, and the new steam extraction isolation valve is located at the front end of the steam compressor.

[0020] Preferably, a heat exchanger is further arranged in the pipeline of the pressurizing module, and the heat exchanger is located upstream of the steam compressor or between the steam compressor and the new external steam cooler.

[0021] In the present scheme, the new steam extraction isolation valve is arranged in the pressurizing module and located at the front end of the steam compressor, the flow rate of the fluid entering the pressurizing module is adjusted through the new steam extraction isolation valve, and when the steam compressor, the new external steam cooler and other equipment fail, the steam is prevented from entering the pressurizing module by closing the new steam extraction isolation valve, thereby ensuring the safety of the system operation and improving the flexibility of the system operation. The heat exchanger is arranged in the pipeline of the pressurizing module, the steam in the pipeline enters the heat exchanger to heat other working substances such as air, water and coal, and then enters the corresponding equipment. For example, when the heat exchanger is arranged upstream of the steam compressor, the steam below the target steam extraction pressure level enters the heat exchanger to heat other working substances such as air, water and coal, and then enters the new external steam cooler after being pressurized by the steam compressor to heat the feed water. In this way, the steam temperature entering the steam compressor is reduced, and the steam flow rate of the new external steam cooler is relatively increased. When the heat exchanger is arranged between the steam compressor and the new external steam cooler, the steam below the target steam extraction pressure level is pressurized by the steam compressor, enters the heat exchanger to heat other working substances such as air, water and coal, and then enters the new external steam cooler to heat the feed water. In this way, the steam temperature entering the new external steam cooler is reduced, and the steam flow rate of the new external steam cooler is relatively increased.

[0022] Preferably, the steam below the target steam extraction pressure level is derived from part of the final stage extraction steam of the high-pressure cylinder, and the inlet of the pressurizing module is connected to the extraction pipeline through a pipeline.

[0023] In the present scheme, the inlet of the pressurizing module is connected to the existing final stage high-pressure heating extraction 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 new external steam cooler and the new 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 deep peak regulation conditions.

[0024] Preferably, the interface at which the pressurizing module is connected to the extraction pipeline is located upstream of the steam extraction isolation valve.

[0025] In the scheme, the interface of the pressurizing module connected to the extraction pipe is located upstream of the extraction isolation valve, so that part of the last-stage extraction steam is extracted before the front end of the extraction isolation valve inlet, and the extraction isolation valve can control the part of the last-stage extraction steam of the high-pressure cylinder to enter 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, the extraction isolation valve is closed, and the normal work of the pressurizing module and the newly added last-stage high-pressure heater is not affected, and the flexibility of the unit operation is improved.

[0026] Preferably, the steam source with a pressure lower than the target extraction steam pressure level is the regenerative extraction steam in the unit or other units or the steam in the reheating system or the steam in the superheater system.

[0027] In the scheme, the steam source with a pressure lower than the target extraction steam pressure level is optimized to be the regenerative extraction steam in the unit or other units or the steam in the reheating system or the steam in the superheater system, and under the premise that the outlet steam pressure of the steam compressor is higher than the last-stage extraction steam of the high-pressure cylinder, the flexibility of the unit operation is improved.

[0028] Preferably, the main steam throttling assembly is a high-pressure cylinder inlet valve group or a regulating valve.

[0029] In the scheme, the main steam throttling assembly adopts a high-pressure cylinder inlet valve group or a regulating valve to conveniently adjust the pressure and flow of the main steam.

[0030] 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 the feed water at the economizer outlet at a certain subcooling degree.

[0031] In the scheme, the steam with a pressure lower than the target extraction steam pressure level is pressurized by the pressurizing module and then sequentially enters the newly added external steam cooler and the newly added last-stage high-pressure heater to supplement the heating of the feed water heated by the existing last-stage high-pressure heater, so that when the feed water temperature entering the furnace of the unit under deep peak regulation is improved, the main steam is throttled by operating the main steam throttling assembly to maintain a certain feed water pressure and keep the feed water at the economizer outlet at a certain subcooling degree.

[0032] 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.

[0033] 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 that the feed water at the economizer outlet is kept at a certain subcooling degree.

[0034] The positive progress effect of the utility model lies in: on the water supply pipeline, the water supply outlet of the existing last-stage high-pressure heater is sequentially provided with a newly-added last-stage high-pressure heater, a newly-added external steam cooler, and 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 with steam with a pressure lower than a target steam extraction pressure level, and the steam side outlet of the newly-added external steam cooler is connected with the steam inlet of the newly-added last-stage high-pressure heater, that is, on the basis of the existing last-stage high-pressure heater normally heating the water supply, steam with a pressure lower than the target steam extraction pressure level is introduced, boosted by the pressure boosting module, and then heated twice in the newly-added external steam cooler and the newly-added last-stage high-pressure heater, so as to increase the boiler inlet water temperature of the unit, maintain a certain water supply pressure, keep the boiler outlet water supply at a certain supercooling degree, increase the boiler inlet water temperature, the boiler outlet water temperature, the boiler outlet flue gas temperature, reduce the water cooling wall inlet enthalpy deficiency, shorten the hot water section in the water cooling wall, and keep the water cooling wall outlet steam with a certain superheating degree, so as to realize the boiler dry running of the unit under the deep peak shaving condition, keep the water power stability, and continuously and stably put the denitration system into operation. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a system schematic diagram for heating the boiler water supply in the prior art.

[0036] Figure 2 It is a system configuration schematic diagram for the coal power unit to adapt to the deep peak shaving operation according to an embodiment of the utility model. DETAILED DESCRIPTION

[0037] The utility model will be described below in combination with the drawings.

[0038] Figure 1 It is a system schematic diagram for heating the boiler inlet water supply in the prior art. The system comprises a boiler, a deaeration system, a high-pressure cylinder and an existing last-stage high-pressure heater. The boiler comprises a coal economizer, a water cooling wall and a superheater which are sequentially connected by pipelines. The deaeration system comprises a deaerator, a pre-pump and a water supply pump which are sequentially connected by pipelines. The water supply inlet of the existing last-stage high-pressure heater is communicated with the water supply outlet of the deaeration system, the water supply outlet of the existing last-stage high-pressure heater is communicated with the water supply 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 inlet of the existing last-stage high-pressure heater is communicated with the steam extraction port of the high-pressure cylinder through a steam extraction pipeline. The low-pressure condensate at the outlet of the deaerator is sequentially boosted by the pre-pump and the water supply pump and then enters the existing last-stage high-pressure heater to be heated. The heated water supply enters the boiler and is heated by the heating surfaces of the coal economizer, the water cooling wall and the superheater in sequence, and finally the main steam enters the high-pressure cylinder to do work.

[0039] The utility model provides a kind of system configuration that coal power unit adapts to depth peak shaving operation, as shown in Figure 2 Described, including boiler, deaerating system, high pressure cylinder, existing last stage high pressure heater, feedwater line and steam pipeline, the boiler includes economizer, water-cooled wall, superheater sequentially connected by pipeline, the high pressure cylinder adopts full circumferential admission, and is not configured to adjust level;In the feedwater line, deaerating system, existing last stage high pressure heater, newly added last stage high pressure heater, newly added external steam cooler are sequentially arranged along the feedwater flow direction, the steam pipeline includes main steam pipeline connected between the boiler steam outlet and high pressure cylinder steam inlet and extraction pipeline connected between high pressure cylinder extraction port and the steam inlet of existing last stage high pressure heater, main steam pipeline is provided with main steam throttling assembly, and extraction isolation valve is arranged on the extraction pipeline;The steam side inlet of newly added 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 newly added external steam cooler is communicated with the steam inlet of newly added last stage high pressure heater.

[0040] Feedwater sequentially passes through deaerating system, existing last stage high pressure heater, newly added last stage high pressure heater, newly added external steam cooler and then is sent to boiler feedwater inlet, steam below target extraction pressure level is boosted by booster module, and then is added to newly added external steam cooler to supplement the heating of feedwater, and then is added to newly added last stage high pressure heater to supplement the heating of feedwater heated by existing last stage high pressure heater, that is, on the basis of existing last stage high pressure heater normally put into use to heat feedwater, steam below target extraction pressure level is boosted by booster module and is added to newly added external steam cooler and newly added last stage high pressure heater to supplement heating twice, so as to improve the inlet feedwater temperature of unit, maintain certain feedwater pressure, keep the supercooling degree of economizer outlet feedwater, improve the inlet water temperature of economizer, the outlet water temperature of economizer, improve the outlet flue gas temperature of economizer, reduce the water enthalpy deficit of water-cooled wall inlet, shorten the hot water section in water-cooled wall and keep the steam at water-cooled wall outlet to have certain superheat degree, finally realize the dry operation of boiler, keep water power stability and continuously and stably put denitration system into operation under depth peak shaving condition.

[0041] Figure 2The high-pressure cylinder inlet valve group is arranged on the main steam pipeline, and of course, it can also be arranged for other main steam throttling components, such as a regulating valve, to regulate the pressure and flow of the main steam. It is emphasized here that when the steam below the target extraction pressure level is pressurized in the pressurizing module and then enters the newly added external steam cooler to supplement the heating of the feed water and then flows out of the newly added external steam cooler and enters the newly added final high-pressure heater to supplement the heating of the feed water to improve the inlet feed water temperature of the unit in the deep peak shaving condition, the high-pressure cylinder inlet valve group can also be operated to throttle the main steam by using the original high-pressure cylinder inlet valve group, and the purpose is to maintain a certain feed water pressure and keep the feed water at the outlet of the economizer at 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 from the outlet of the economizer to the inlet of the high-pressure cylinder to maintain a certain feed water pressure and keep the feed water at the outlet of the economizer at a certain supercooling degree.

[0042] As shown in Figure 2 The steam compressor is arranged in the pipeline of the pressurizing module, and the steam compressor is used to pressurize the steam below the target extraction pressure level entering the pressurizing module, so that the pressure of the steam below the target extraction pressure level after being pressurized by the steam compressor is higher than the pressure of the final extraction steam of the high-pressure cylinder. The steam below the target extraction pressure level after being pressurized by the steam compressor is sequentially introduced into the newly added external steam cooler and the newly added final high-pressure heater to supplement the heating of the feed water. The pressure of the steam below the target extraction pressure level after being pressurized by the steam compressor is higher than the pressure of the final extraction steam of the high-pressure cylinder, which ensures that the pressure of the steam entering the newly added external steam cooler after being compressed by the steam compressor is higher than the pressure of the final extraction steam entering the existing final high-pressure heater, so as to heat the feed water to a higher temperature to improve the inlet feed water temperature of the unit in the deep peak shaving condition.

[0043] Further, the steam pressure at the steam side outlet of the newly added external steam cooler is higher than the final extraction steam pressure of the high-pressure cylinder.

[0044] In this scheme, the steam pressure at the steam side outlet of the newly added external steam cooler is higher than the final extraction steam pressure of the high-pressure cylinder, so that the steam pressure entering the newly added final high-pressure heater is higher than the final extraction steam pressure of the high-pressure cylinder, thereby supplementing the heating of the feed water heated by the existing final high-pressure heater at the newly added final high-pressure heater.

[0045] As shown in Figure 2As shown, the pipeline of the pressurizing module is provided with a newly added steam extraction isolation valve, which is located at the front end of the steam compressor. By arranging the newly added steam extraction isolation valve upstream of the steam compressor, the fluid flow into the pressurizing module is adjusted through the newly added steam extraction isolation valve, and when the steam compressor, the newly added external steam cooler and other equipment fail, the steam is prevented from entering the pressurizing module by closing the newly added steam extraction isolation valve, thereby ensuring the safety of system operation and improving the flexibility of system operation.

[0046] Of course, the pipeline of the pressurizing module is also provided with a heat exchanger, which is located upstream of the steam compressor or between the steam compressor and the newly added external steam cooler. By arranging the heat exchanger in the pipeline of the pressurizing module, the steam in the pipeline enters the heat exchanger to heat other working substances such as air, water and coal, and then enters the corresponding equipment. For example, when the heat exchanger is arranged upstream of the steam compressor, the steam below the target steam extraction pressure level first enters the heat exchanger to heat other working substances such as air, water and coal, and then enters the newly added external steam cooler after being pressurized by the steam compressor to heat the feed water. In this way, the steam temperature entering the steam compressor is reduced, and the steam flow into the newly added external steam cooler is relatively increased. When the heat exchanger is arranged between the steam compressor and the newly added external steam cooler, the steam below the target steam extraction pressure level is pressurized by the steam compressor, enters the heat exchanger to heat other working substances such as air, water and coal, and then enters the newly added external steam cooler to heat the feed water. In this way, the steam temperature entering the newly added external steam cooler is reduced, and the steam flow into the newly added external steam cooler is relatively increased.

[0047] As shown in Figure 2 The steam below the target steam extraction pressure level is derived from part of the final stage extraction steam of the high-pressure cylinder, and the inlet of the pressurizing module is connected to the extraction steam pipeline through a pipeline, so that 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 deep peak regulation condition. The interface of the pressurizing module connected to the extraction steam pipeline is located upstream of the extraction steam isolation valve to lead part of the final stage extraction steam out of the front end of the extraction steam isolation valve inlet, so that 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. Even when the existing final stage high-pressure heater cannot work, closing the extraction steam isolation valve will not affect the normal work of the pressurizing module and the newly added final stage high-pressure heater, thereby improving the flexibility of unit operation.

[0048] Of course, in other embodiments, the source of steam below the target extraction pressure level is the extraction steam in the regenerative system or the steam in the reheat system or the steam in the superheater system in the unit or in other units. Optimizing the source of steam below the target extraction pressure level to be the extraction steam in the regenerative system or the steam in the reheat system or the steam in the superheater system in the unit or in other units improves the operation flexibility of the unit on the premise that the outlet steam pressure of the steam compressor is higher than the last stage extraction steam pressure of the high-pressure cylinder.

[0049] The system configuration of the coal-fired unit for adaptive deep peak regulation operation provided by the utility model is under the deep peak regulation working condition, taking 20% THA working condition as an example: the unit inlet feed water temperature can be raised to 75% THA or even 100% THA feed water temperature level, with the increase of the unit inlet 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 requirement; 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 increase of the economizer outlet water temperature, the water wall inlet water temperature is improved, and then the water wall inlet enthalpy deficit is reduced, and the hydrodynamic stability is strengthened; with the increase of the water wall inlet water temperature, the water wall outlet steam can maintain a certain superheating degree, that is, the boiler dry operation is realized.

[0050] Taking the data of a 1000MW unit under 20% THA working condition as an example.

[0051] Prior art scheme: the main generator load is 200MW, the existing last stage high-pressure heater inlet steam pressure and temperature parameters are 1.75MPa and 436℃, the outlet feed water pressure and temperature parameters are 6MPa and 192℃, the economizer outlet water temperature is 240℃, the supercooling degree is 36℃, the enthalpy deficit is 176kJ / kg, the economizer outlet flue gas temperature is 245℃, the water wall outlet is wet saturated steam, the unit is in a wet state operation state, and the denitration system cannot be put into use.

[0052] The present embodiment scheme: the main generator load is 200MW, the existing last stage extraction steam pressure and temperature parameters are 1.0MPa and 340℃, the newly added last stage high-pressure heater inlet steam pressure and temperature parameters after being pressurized by the steam compressor and being temperature reduced by the newly added external steam cooler are 5.9MPa and 401℃, the outlet feed water pressure and temperature parameters are 11.8MPa and 274℃, the water side temperature rise of the newly added external steam cooler is 5℃, the economizer outlet water temperature is 307℃, the supercooling degree is 16.4℃, the enthalpy deficit is 102.1kJ / kg, the economizer outlet flue gas temperature is 312℃, the water wall outlet superheating degree is 13℃, the unit is in a dry state operation state, the water wall inlet water enthalpy deficit is relatively reduced by 73.9kJ / kg, the water wall outlet steam temperature deviation is controlled, the hydrodynamic stability is strengthened, and the denitration system is stably and continuously put into use.

[0053] The system configuration provided by the embodiment is suitable for deep peak regulation operation of a coal-fired unit, and comprises a newly-added final-stage high-pressure heater and a newly-added external steam cooler arranged in sequence at the outlet of an existing final-stage high-pressure heater, wherein part of the final-stage extraction steam is introduced, the extraction steam is pressurized by a steam compressor, and then the extraction steam enters the newly-added external steam cooler to heat feed water; the steam at the steam side outlet of the newly-added external steam cooler reenters the newly-added final-stage high-pressure heater to heat the feed water, and a certain feed water pressure is maintained to keep the feed water at the outlet of an economizer at a certain supercooling degree, so as to increase the inlet feed water temperature of the unit under the deep peak regulation condition, and then to increase the inlet water temperature of the economizer, the outlet water temperature of the economizer, the outlet flue gas temperature of the economizer, to reduce the water enthalpy deficit at the inlet of the water-cooled wall, to shorten the hot water section in the water-cooled wall, and to keep the steam at the outlet of the water-cooled wall having a certain superheating degree, so as to finally realize the dry operation of the boiler under the deep peak regulation condition, to keep the water power stable, and to keep the denitration system continuously and stably in operation.

[0054] 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 adapting deep peak shaving operation of a coal-fired power unit, comprising a boiler, a deaerator 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 a coal economizer, a water cooling wall and a superheater connected in sequence through pipelines, the high-pressure cylinder adopts full-circumferential admission and is not provided with an adjusting stage; in the feedwater pipeline, an oxygen removal system, an existing final-stage high-pressure heater, a newly-added final-stage high-pressure heater and a newly-added external steam cooler are arranged in sequence along the feedwater flow direction, the steam pipeline comprises a main steam pipeline connected between the boiler steam outlet and the high-pressure cylinder steam inlet and a steam extraction pipeline connected between the high-pressure cylinder steam extraction port and the steam inlet of the existing final-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 the 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 final-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, which is used for boosting the steam at a pressure lower than the target steam extraction pressure level entering the pressure boosting module, so that the pressure of the steam at a pressure lower than the target steam extraction pressure level after being boosted by the steam compressor is higher than the pressure of the final-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 final-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, which is located at the front end of the steam compressor. And / or, the pipeline of the pressure boosting module is further provided with a heat exchanger, which is located upstream of the steam compressor or between the steam compressor and the newly-added external steam cooler.

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 final-stage steam extraction of the high-pressure cylinder, and the inlet of the pressure boosting module is connected to the steam extraction pipeline through a pipeline.

6. The system configuration of claim 5, wherein, The interface of the pressure boosting module connected to the steam extraction pipeline is located upstream of the steam extraction isolation valve.

7. The system configuration of claim 1, wherein, The steam at a pressure lower than the target steam extraction pressure level is derived from the regenerative extraction or the steam in the reheating system or the steam in the superheater system in the unit or other units.

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 coal economizer outlet 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 coal economizer outlet to the high-pressure cylinder inlet, and the throttling assembly is adjusted to maintain a certain feedwater pressure.

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