Deep peak regulation operation system configuration of coal power unit based on water supply supplementary heating

Abstract

The utility model provides a deep peak regulation operation system configuration of a coal power unit based on water supply supplementary heating, which is characterized in that a newly-added final-stage high-pressure heater and a newly-added external steam cooler are additionally arranged 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 level 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 the steam is used for performing two times of supplementary heating on feed water in a newly-added external steam cooler and a newly-added final-stage high-pressure heater, so that the temperature of feed water entering a furnace of the unit is increased, meanwhile, certain feed water pressure is maintained, stable denitration operation of the unit under the deep peak regulation working condition is achieved, and the aim of improving the denitration efficiency is achieved. The energy consumption of the unit is prevented from being greatly increased, and the unit operation economy is effectively improved.

Description

Technical Field

[0001] This utility model relates to the field of power generation technology, and in particular to a deep peak-shaving operation system configuration for coal-fired power units based on feedwater supplementary heating. Background Technology

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

[0003] Although the installed capacity and power generation of new energy sources have reached new highs, traditional thermal power units, especially coal-fired power units, still need to play the role of basic backup power sources and flexible peak-shaving power sources to support new energy power generation due to the uncertainty of power generation from new energy sources.

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

[0005] For subcritical units that need to participate in deep peak shaving operation, such as those with a load variation range of 20%-100% THA, where the deep peak shaving load range is 20%-30% THA or even lower, the following problems will be faced:

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

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

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

[0009] The technical problem to be solved by this utility model is to overcome the defects that the denitrification system of subcritical units will not be able to operate normally under deep peak shaving conditions, the unit energy consumption will increase significantly, and the operating economy will decrease significantly. The present invention provides a deep peak shaving operation system configuration for coal-fired power units based on feedwater supplementary heating.

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

[0011] This utility model provides a deep peak-shaving operation system configuration for coal-fired power units based on feedwater supplemental heating, comprising: a boiler, a deaerator system, a high-pressure cylinder, an existing final-stage high-pressure heater, feedwater pipelines, and steam pipelines. The boiler includes an economizer, a steam drum, a superheater, a header, a downcomer, and water-cooled walls. The economizer, steam drum, and superheater are connected sequentially by pipelines. Water from the lower part of the steam drum flows through the downcomer to the header, is heated by the water-cooled walls, and then returns to the steam drum. The high-pressure cylinder adopts a partial steam intake method and is equipped with a regulating stage. In the feedwater pipelines, the deaerator system and the existing final-stage high-pressure heater are sequentially arranged along the feedwater flow direction. The system includes a new final-stage high-pressure heater and a new external steam cooler. The steam pipeline consists of a main steam pipeline connecting the boiler steam outlet and the high-pressure cylinder inlet, and an extraction steam pipeline connecting the high-pressure cylinder extraction steam outlet and the existing final-stage high-pressure heater inlet. A regulating stage inlet valve group is installed on the main steam pipeline, and an extraction steam isolation valve is installed on the extraction steam pipeline. The steam-side inlet of the new external steam cooler is connected to a booster module, and the inlet of the booster module is connected to steam at a pressure lower than the target extraction steam pressure level. The steam-side outlet of the new external steam cooler is connected to the inlet of the new final-stage high-pressure heater.

[0012] In this scheme, a new final-stage high-pressure heater and a new external steam cooler are sequentially installed at the feedwater outlet of the existing final-stage high-pressure system in the feedwater pipeline. The steam-side inlet of the new external steam cooler is connected to a booster module. The inlet of the booster module receives steam at a pressure lower than the target extraction pressure. The steam-side outlet of the new external steam cooler is connected to the steam inlet of the new final-stage high-pressure heater. The steam at a pressure lower than the target extraction pressure is boosted by the booster module and first goes to the new external steam cooler to supplement the feedwater at that location before proceeding to the new final-stage high-pressure heater. The feedwater, after being heated by the existing final-stage high-pressure heater, is supplemented with additional heating. That is, on the basis of the existing final-stage high-pressure heater normally heating the feedwater, steam lower than the target extraction steam pressure level is introduced, pressurized by the booster module, and then supplemented twice in the newly added external steam cooler and the newly added final-stage high-pressure heater to increase the unit's feedwater temperature. As the unit's feedwater temperature increases, the economizer inlet water temperature increases, which in turn increases the economizer outlet water temperature, and the economizer outlet flue gas temperature increases to meet the denitrification inlet flue gas temperature requirements.

[0013] Preferably, 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 at the front end of the steam compressor. The new extraction steam isolation valve regulates the fluid flow rate entering the booster module. 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, a heat exchanger is also provided in the pipeline of the booster module, the heat exchanger being located upstream of the steam compressor or between the steam compressor and the newly added external steam cooler.

[0020] In this scheme, a heat exchanger is installed in the pipeline of the booster module. Steam in the pipeline enters the heat exchanger to heat other working media, such as air, water, and coal, before entering the corresponding equipment. For example, after heat exchange, the heat exchanger is located upstream of the steam compressor. Steam with a pressure lower than the target extraction pressure level first enters the heat exchanger to heat other working media, such as air, water, and coal. After being pressurized by the steam compressor, it enters the newly added external steam cooler to heat the feedwater. This reduces the steam temperature entering the steam compressor and relatively increases the steam flow rate of the newly added external steam cooler. Alternatively, the heat exchanger is located between the steam compressor and the newly added external steam cooler. Steam with a pressure lower than the target extraction pressure level is pressurized by the steam compressor before entering the heat exchanger to heat other working media, such as air, water, and coal, before entering the newly added external steam cooler to heat the feedwater. This reduces the steam temperature entering the newly added external steam cooler and relatively increases the steam flow rate of the newly added external steam cooler.

[0021] 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.

[0022] In this scheme, the inlet of the booster module is connected to the existing extraction steam pipeline of the final-stage high-pressure heater via a pipeline. Part of the final-stage extraction steam from the high-pressure cylinder enters the existing final-stage high-pressure heater to heat the feedwater, while the other part of the final-stage extraction steam from the high-pressure cylinder is pressurized by the booster module and then sequentially enters the newly added external steam cooler and the newly added final-stage high-pressure heater to supplement or reheat the feedwater that has been heated by the existing final-stage high-pressure heater, thereby increasing the feedwater temperature entering the boiler under deep peak shaving conditions. The interface of the booster module 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 from the front end of the extraction steam isolation valve inlet. This allows the extraction steam isolation valve to independently control a portion of the final-stage extraction steam from the high-pressure cylinder to enter the existing final-stage high-pressure heater to heat the feedwater. Even if the existing final-stage high-pressure heater cannot work, closing the extraction steam isolation valve will not affect the normal operation of the booster module and the newly added final-stage high-pressure heater, thus improving the flexibility of unit operation.

[0023] Preferably, the steam source below the target extraction pressure level is regenerative extraction steam or reheat system steam or superheater system steam in this unit or other units.

[0024] In this scheme, steam below the target extraction pressure level is optimized into reheat extraction steam or reheat system steam or superheater system steam in this unit or other units. Under the premise of ensuring that the steam compressor outlet steam pressure is higher than the final stage extraction steam of the high-pressure cylinder, the operation flexibility of this unit is improved.

[0025] Preferably, the boiler is equipped with a circulating pump in the downcomer connecting the steam drum and the header.

[0026] And / or, the number of valves in the regulating stage inlet valve group is four or six.

[0027] In this scheme, a circulating pump is installed in the downcomer connecting the steam drum and the header to enhance the driving force of the working fluid circulation, so that the water in the lower part of the steam drum can flow smoothly through the downcomer to the header; and the number of valves in the regulating stage inlet valve group is four or six. By regulating the main steam flow through multiple valves, not only is the flow control accuracy high, but the flow of a single valve is relatively small, which makes the pressure control of the main steam more precise and convenient.

[0028] Preferably, the deep peak shaving operation system is configured to: throttle the main steam using the regulating stage inlet steam valve group to maintain a certain feedwater pressure and keep the economizer outlet feedwater at a certain degree of subcooling.

[0029] In this scheme, steam below the target extraction pressure level is pressurized by a booster module and then sequentially enters the newly added external steam cooler and the newly added final-stage high-pressure heater to supplement the feedwater that has been heated by the existing final-stage high-pressure heater. This is to increase the feedwater temperature at the boiler inlet of the unit under deep peak shaving conditions. At the same time, the main steam is throttled by operating the original regulating stage inlet valves. The purpose is to maintain a certain feedwater pressure and keep the economizer outlet feedwater at a certain degree of subcooling. Furthermore, the regulating stage inlet valve group can control the main steam while also obtaining a certain steam enthalpy drop, thereby relatively improving the unit's economy.

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

[0031] In this scheme, throttling components, such as regulating valves, can be installed in the feedwater or steam pipeline from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feedwater pressure, thereby keeping the economizer outlet feedwater at a certain degree of subcooling.

[0032] The positive and progressive effects of this utility model are as follows: A new final-stage high-pressure heater and a new external steam cooler are sequentially installed at the feedwater outlet of the existing final-stage high-pressure system in the feedwater pipeline. A booster module is connected to the steam-side inlet of the new external steam cooler, and steam with a pressure lower than the target extraction pressure is introduced into the booster module. The steam-side outlet of the new external steam cooler is connected to the steam inlet of the new final-stage high-pressure heater. Based on the existing final-stage high-pressure heater's normal operation for heating the feedwater, steam with a pressure lower than the target extraction pressure is introduced, boosted by the booster module, and then subjected to two supplementary heating processes in the new external steam cooler and the new final-stage high-pressure heater. This increases the feedwater temperature into the boiler and simultaneously maintains a certain feedwater pressure to keep the economizer outlet feedwater at a certain degree of subcooling. This enables the denitrification system to operate continuously and stably under deep peak-shaving conditions, avoiding a significant increase in unit energy consumption and effectively improving the unit's operational economy. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a boiler feedwater heating system in the prior art.

[0034] Figure 2 This is a schematic diagram of the configuration of a deep peak-shaving operation system for a coal-fired power unit based on supplementary heating of feedwater, according to an embodiment of the present invention. Detailed Implementation

[0035] The present invention will be described more clearly and completely below with reference to the accompanying drawings, using a preferred embodiment.

[0036] Figure 1 This is a schematic diagram of a boiler feedwater heating system in the prior art. The system includes a boiler, a deaerator system, a high-pressure cylinder, and an existing final-stage high-pressure heater. The boiler includes an economizer, a steam drum, a superheater, a header, a downcomer, and water-cooled walls. The economizer, steam drum, and superheater are connected sequentially by pipelines. Water from the lower part of the steam drum flows through the downcomer to the header, is heated by the water-cooled walls, and then returns to the steam drum. The deaerator system includes a deaerator, a booster pump, and a feedwater pump. The high-pressure cylinder uses a partial steam inlet method and is equipped with a regulating stage. A regulating stage inlet valve group is arranged on the main steam pipeline. An extraction steam isolation valve is installed on the inlet pipeline connecting the high-pressure cylinder and the existing final-stage high-pressure heater. The steam source for the existing final-stage high-pressure heater is the final-stage extraction steam from the high-pressure cylinder. During system operation: the low-pressure condensate from the deaerator outlet is pressurized sequentially by the booster pump and the feedwater pump before entering the high-pressure heater for heating. The heated feedwater enters the boiler, is further heated by the economizer, and then enters the steam drum. The steam-water mixture undergoes steam-water separation in the steam drum. Specifically, the water in the lower part of the steam drum flows through the downcomer to the header, is heated by the water-cooled wall, and then returns to the steam drum. The wet saturated steam in the upper part of the steam drum enters the superheater and other heating surfaces for heating, and finally obtains the main steam which enters the high-pressure cylinder to do work.

[0037] This utility model provides a configuration for a deep peak-shaving operation system for coal-fired power units based on feedwater supplemental heating, 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 adopts a partial steam intake method and is equipped with a regulating stage. In the feedwater pipelines, along the feedwater flow direction, a deaeration system, an existing final-stage high-pressure heater, a newly added final-stage high-pressure heater, and a newly added external high-pressure heater are sequentially arranged. The 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 existing final-stage high-pressure heater inlet. A regulating stage inlet valve group is installed on the main steam pipeline, and an extraction steam isolation valve is installed on the extraction steam pipeline. The steam-side inlet of the newly added external steam cooler is connected to a booster module. The booster module inlet 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 used in existing boiler feedwater heating systems, i.e., without a booster module, directly entering the existing final-stage high-pressure heater to heat the feedwater to the required temperature and pressure.

[0038] Feedwater is sequentially delivered to the boiler feedwater inlet via the deaeration system, the existing final-stage high-pressure heater, and the newly added external steam cooler. Steam below the target extraction pressure level is pressurized by the booster module and first used to supplement the feedwater in the newly added external steam cooler for additional heating. Then, it is used in the newly added final-stage high-pressure heater to supplement the feedwater heated by the existing final-stage high-pressure heater. In other words, in addition to the existing final-stage high-pressure heater normally heating the feedwater, steam below the target extraction pressure level is introduced, pressurized by the booster module, and then used for supplementary heating twice, once in the newly added external steam cooler and once in the newly added final-stage high-pressure heater. This not only increases the feedwater temperature at the boiler inlet under deep peak shaving conditions but also improves heat utilization. At the same time, the regulating stage inlet valve group installed on the main steam pipeline throttles the main steam to maintain a certain feedwater pressure and keeps the economizer outlet feedwater at a certain degree of subcooling. This ensures the continuous and stable operation of the denitrification system under deep peak shaving conditions, avoids a significant increase in unit energy consumption, and effectively improves the unit's operating economy.

[0039] Compared to the scheme of replacing the inlet steam of the final stage high-pressure heater with the main steam after cooling and depressurization, this utility model can save the amount of high-temperature and high-pressure pipeline used, avoid the negative safety impact caused by the instantaneous change in the heat absorption ratio of the main and reheat steam due to the use of main steam, and the extraction steam used in this utility model is lower than the target extraction steam pressure level, which has better thermal economy than the main steam that does not do work in the steam turbine. Therefore, this scheme has the advantages of relative safety, low cost, high operational flexibility and good economy.

[0040] When increasing the boiler feedwater temperature under deep peak-shaving conditions, the main steam is throttled by operating the regulating stage inlet steam valve group to maintain a certain feedwater pressure and keep the economizer outlet feedwater at a certain degree of subcooling. Compared to the isenthalpic throttling method using valves without a regulating stage, the regulating stage inlet steam valve group achieves the same pressure control effect for the main steam while also obtaining a certain steam enthalpy drop, thus improving the unit's economy. Furthermore, because the flow rate of each valve in the regulating stage inlet steam valve group is relatively small, its pressure control of the main steam is more precise and convenient. Of course, in other embodiments, throttling components, such as regulating valves, can also be installed in the feedwater or steam pipeline from the economizer outlet to the high-pressure cylinder inlet to maintain a certain feedwater pressure, thereby keeping the economizer outlet feedwater at a certain degree of subcooling.

[0041] like Figure 2 As shown, a steam compressor is installed in the pipeline of the booster module. The steam compressor is used to pressurize the steam entering the booster module that is below the target extraction pressure level, so that the steam below the target extraction pressure level, after being pressurized by the steam compressor, has a pressure higher than the pressure of the final stage extraction steam of the high-pressure cylinder. After being pressurized by the steam compressor, the steam below the target extraction pressure level enters the newly added external steam cooler and the newly added final stage high-pressure heater in sequence to supplement the heating of the feedwater. The steam below the target extraction pressure level, after being pressurized by the steam compressor, has a pressure higher than the pressure of the final stage extraction steam 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 pressure of the final stage extraction steam 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.

[0042] Furthermore, the steam pressure at the steam outlet of the newly added external steam cooler is higher than the final stage extraction 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 pressure of the high-pressure cylinder, thereby enabling 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.

[0043] like Figure 2As shown, a new steam extraction isolation valve is installed in the pipeline of the booster module, and the new steam extraction isolation valve is located at the front end of the steam compressor. By adjusting the fluid flow rate entering the booster module through the new steam extraction isolation valve, and in the event of equipment failure such as the steam compressor or the new external steam cooler, the new steam extraction isolation valve can be closed to prevent steam from entering the booster module, ensuring the safety of system operation and improving the flexibility of system operation.

[0044] Of course, a heat exchanger can also be installed in the pipeline of the booster module. The heat exchanger is installed upstream of the steam compressor or between the steam compressor and the newly added external steam cooler. A heat exchanger is installed in the pipeline of the booster module. Steam in the pipeline enters the heat exchanger to heat other working media, such as air, water, and coal, before entering the corresponding equipment. For example, after heat exchange, the heat exchanger is located upstream of the steam compressor. Steam with a pressure lower than the target extraction pressure level first enters the heat exchanger to heat other working media, such as air, water, and coal. After being pressurized by the steam compressor, it enters the newly added external steam cooler to heat the feedwater. This reduces the steam temperature entering the steam compressor and relatively increases the steam flow rate of the newly added external steam cooler. Alternatively, the heat exchanger can be placed between the steam compressor and the newly added external steam cooler. Steam with a pressure lower than the target extraction pressure level is pressurized by the steam compressor before entering the heat exchanger to heat other working media, such as air, water, and coal, before entering the newly added external steam cooler to heat the feedwater. This reduces the steam temperature entering the newly added external steam cooler and relatively increases the steam flow rate of the newly added external steam cooler.

[0045] like Figure 2 As shown, 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. The inlet of the booster module is connected to the existing extraction steam pipeline of the final-stage high-pressure heater via a pipeline. Part of the final-stage extraction steam from the high-pressure cylinder enters the existing final-stage high-pressure heater to heat the feedwater, while the other part of the final-stage extraction steam from the high-pressure cylinder is pressurized by the booster module and then sequentially enters the newly added external steam cooler and the newly added final-stage high-pressure heater to supplement or reheat the feedwater that has been heated by the existing final-stage high-pressure heater, thereby increasing the feedwater temperature entering the boiler under deep peak shaving conditions. The interface of the booster module 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 from the front end of the extraction steam isolation valve inlet. This allows the extraction steam isolation valve to independently control a portion of the final-stage extraction steam from the high-pressure cylinder to enter the existing final-stage high-pressure heater to heat the feedwater. Even if the existing final-stage high-pressure heater is not working, closing the extraction steam isolation valve will not affect the normal operation of the booster module and the newly added final-stage high-pressure heater, improving the flexibility of unit operation.

[0046] Of course, in other embodiments, the steam source below the target extraction pressure level is regenerative extraction steam or steam in the reheat system or superheater system of this unit or other units. Optimizing the steam below the target extraction pressure level to regenerative extraction steam or steam in the reheat system or superheater system of this unit or other units improves the operational flexibility of the unit while ensuring that the steam compressor outlet steam pressure is higher than the final stage extraction steam of the high-pressure cylinder.

[0047] Figure 2 In the regulating stage, the number of valves in the steam inlet valve group is four, but it can also be set to six. By regulating the main steam flow through multiple valves, the main steam flow can be controlled, and a certain steam enthalpy drop can be obtained, which improves the economic efficiency of the unit. Not only is the flow control accuracy high, but the flow of a single valve is relatively small, making the pressure control of the main steam more precise and convenient.

[0048] Although Figure 2 In this embodiment, the water in the boiler drum flows directly to the header through the downcomer. Of course, in other embodiments, a circulation pump can also be installed in the downcomer connecting the boiler drum and the header to enhance the driving force of the working fluid circulation, so that the water in the lower part of the drum can flow smoothly to the header through the downcomer.

[0049] This utility model provides a deep peak-shaving operation system configuration for coal-fired power units based on feedwater supplementary heating. Under deep peak-shaving conditions, taking 20% ​​THA as an example: the feedwater temperature at the unit inlet can be increased to 75% THA or even 100% THA. With the increase in feedwater temperature, the economizer inlet water temperature increases, leading to an increase in economizer outlet water temperature, and consequently, an increase in economizer outlet flue gas temperature, meeting the denitrification inlet flue gas temperature requirements. While the economizer outlet water temperature increases, a certain feedwater pressure is maintained, ensuring a certain degree of subcooling at the economizer outlet. With the increase in feedwater pressure, the pressure of the steam-water mixture in the steam drum also increases, leading to an increase in the wet saturated steam temperature at the top of the steam drum, and further, an increase in the main steam temperature. As the ratio of main steam temperature, main steam quantity, and reheat steam quantity increases, both cold reheat steam and hot reheat steam temperatures are increased, thus preventing a significant increase in unit energy consumption and effectively improving the unit's operational economy.

[0050] Taking a 300MW subcritical unit with a partial steam inlet in its high-pressure cylinder and a regulating stage as an example, under 20% THA conditions.

[0051] The current system has the following parameters: main generator load 60MW, current final stage high pressure heater inlet steam pressure and temperature parameters 1.29MPa, 370℃, outlet feedwater pressure and temperature parameters 8.5MPa, 192℃, economizer outlet water temperature 211℃, subcooling 107.3℃, underenthalpy 521kJ / kg, economizer outlet flue gas temperature 272℃, and denitrification system cannot be put into operation.

[0052] This embodiment's scheme: The main generator load is 60MW. The existing final-stage extraction steam pressure and temperature parameters are 0.96MPa and 346℃. After being pressurized by the steam compressor and de-cooled by the newly added external steam cooler, the new final-stage high-pressure heater inlet steam pressure and temperature parameters are 3.55MPa and 396℃, and the outlet feedwater pressure and temperature parameters are 10.6MPa and 245℃. The water-side temperature rise of the newly added external steam cooler is 5℃. The economizer outlet water temperature is 272℃, subcooling is 43.3℃, ​​underenthalpy is 239.8kJ / kg, and the economizer outlet flue gas temperature is 338℃. The denitrification system is stably and continuously put into operation, and the unit is relatively stable due to the feedwater temperature. The improved efficiency enhances the unit's operational economy. Meanwhile, the inlet and outlet flow rates, pressures, and temperatures of the regulating stage are 206 t / h, 10.2 MPa, and 532℃, and 206 t / h, 2.5 MPa, and 443℃, respectively. The effective enthalpy drop per unit working fluid is 118.7 kJ / kg, corresponding to a power output of 6.8 MW. Compared to the isenthalpic throttling method using valves without a regulating stage, the regulating stage inlet valve group achieves the same pressure control effect on the main steam while improving the unit's economic efficiency. Furthermore, because the flow rate of each valve in the regulating stage inlet valve group is relatively small, its pressure control of the main steam is more precise and convenient.

[0053] This embodiment provides a deep peak-shaving operation system configuration for coal-fired power units based on supplementary feedwater heating. For subcritical units, the high-pressure cylinder adopts a partial steam inlet method and is equipped with a regulating stage. At the outlet of the existing final-stage high-pressure heater, a new final-stage high-pressure heater and a new external steam cooler are added sequentially. By drawing out a portion of the final-stage extracted steam, after being pressurized by the steam compressor, it enters the new external steam cooler to heat the feedwater. The steam from the steam side outlet of the new external steam cooler then enters the new final-stage high-pressure heater to heat the feedwater. At the same time, the main steam is throttled using the regulating stage inlet steam valve group to maintain a certain feedwater pressure so that the feedwater at the economizer outlet maintains a certain degree of subcooling, thereby increasing the feedwater temperature into the boiler under deep peak-shaving conditions. This, in turn, increases the economizer inlet water temperature, economizer outlet water temperature, economizer outlet flue gas temperature, and steam drum outlet steam temperature. Ultimately, this enables the unit to continuously and stably operate the denitrification system under deep peak-shaving conditions, avoiding a significant increase in unit energy consumption and effectively improving the unit's operating economy.

[0054] While specific embodiments of this utility model have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this utility model is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this utility model, but all such changes and modifications fall within the scope of protection of this utility model.

Claims

1. A deep peak-shaving operation system configuration for a coal-fired power unit based on supplementary feedwater heating, comprising: A boiler, deaerator system, high-pressure cylinder, existing final-stage high-pressure heater, feedwater pipeline, and steam pipeline are characterized in that the boiler includes an economizer, steam drum, superheater, header, downcomer, and water-cooled wall; the economizer, steam drum, and superheater are connected sequentially by pipelines; water from the lower part of the steam drum flows through the downcomer to the header, is heated by the water-cooled wall, and then returns to the steam drum; the high-pressure cylinder adopts a partial steam inlet method and is equipped with a regulating stage; in the feedwater pipeline, along the feedwater flow direction, a deaerator system, an existing final-stage high-pressure heater, a newly added final-stage high-pressure heater, and a newly added external high-pressure heater are sequentially arranged. The 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 existing final-stage high-pressure heater inlet. A regulating stage inlet valve group is installed on the main steam pipeline, and an extraction steam isolation valve is installed on the extraction steam pipeline. A booster module is connected to the steam-side inlet of the newly added external steam cooler. The booster module inlet 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.

2. The deep peak shaving operation system configuration as described in claim 1, characterized in that, 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.

3. The deep peak shaving operation system configuration as described in claim 2, characterized in that, The steam pressure at the steam-side outlet of the newly added external steam cooler is higher than the extraction steam pressure of the last stage of the high-pressure cylinder.

4. The deep peak-shaving operation system configuration as described in claim 3, characterized in that, 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.

5. The deep peak-shaving operation system configuration as described in claim 4, characterized in that, A heat exchanger is also installed in the pipeline of the booster module. The heat exchanger is located upstream of the steam compressor or between the steam compressor and the newly added external steam cooler.

6. The deep peak-shaving operation system configuration as described in claim 4, characterized in that, 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.

7. The deep peak-shaving operation system configuration as described in claim 4, characterized in that, Steam sources below the target extraction pressure level are reheat extraction steam or reheat system steam or superheater system steam in this unit or other units.

8. The deep peak-shaving operation system configuration as described in claim 1, characterized in that, The boiler is equipped with a circulating pump in the downcomer connecting the steam drum and the header. And / or, the number of valves in the regulating stage inlet valve group is four or six.

9. The deep peak-shaving operation system configuration as described in any one of claims 1-8, characterized in that, A throttling component is installed in the feedwater or steam pipeline from the economizer outlet to the high-pressure cylinder inlet.

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