System configuration for deep peak regulation operation of coal power unit

Abstract

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

Description

Technical Field

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

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

[0003] In recent years, the installed capacity and power generation of new energy sources have reached new highs. However, due to the uncertainty of power generation from new energy sources, traditional thermal power units, especially coal-fired power units, still need to play the role of basic backup power supply and flexible peak-shaving power supply in coordination with new energy power generation.

[0004] Taking a 300MW subcritical unit as an example, its high-pressure cylinder adopts a partial steam intake method and is equipped with a regulating stage. The power grid dispatch load range in this region is 40%-100% THA. However, with the rapid development of new energy sources, coal-fired power units need 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, their high-pressure cylinders adopt a partial steam intake method and are equipped with a regulating stage. The load variation range is 20%-100% THA, of which 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 this invention aims to solve is how to maintain the continuous and stable operation of the denitrification system in subcritical units under deep peak shaving conditions, avoiding the defects of a significant increase in unit energy consumption and a significant decrease in operating economy, and providing a system configuration for deep peak shaving operation of coal-fired power units.

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

[0011] This utility model provides a system configuration for deep peak-shaving operation of a coal-fired power unit, comprising: 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 a 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 intake method and is equipped with a regulating stage. The feedwater pipelines are sequentially configured with a deaeration system, an existing final-stage high-pressure heater, a newly added external steam cooler, and a newly added external... The feedwater outlet of the external steam cooler is connected to the boiler feedwater inlet; the steam pipeline includes a main steam pipeline connecting the boiler steam outlet and the high-pressure cylinder inlet, and an extraction steam pipeline connecting the high-pressure cylinder extraction steam outlet and the existing final-stage high-pressure heater inlet; the main steam pipeline is equipped with a regulating stage inlet valve group, and the extraction steam pipeline is equipped with an extraction steam isolation valve; the steam-side inlet of the newly added external steam cooler is connected to a booster module, the inlet of the booster module is connected to steam with 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 existing final-stage high-pressure heater.

[0012] In this scheme, a new external steam cooler is installed at the feedwater outlet of the existing final-stage high-pressure 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 level. The steam-side outlet of the new external steam cooler is connected to the steam inlet of the existing final-stage high-pressure heater. The steam at a pressure lower than the target extraction pressure level is boosted by the booster module and first heats the feedwater in the new external steam cooler before heating it in the existing final-stage high-pressure heater. That is, the feedwater is heated twice, in the new external steam cooler and the existing final-stage high-pressure heater, to increase the feedwater temperature entering the boiler. As the feedwater temperature entering the boiler 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 pressurized 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 first heats the feedwater in the newly added external steam cooler. Then, the feedwater is heated in the existing final stage high-pressure heater. 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. This ensures that the feedwater is heated to a higher temperature, thereby improving the boiler feedwater temperature of the unit under deep peak shaving conditions.

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

[0016] In this scheme, the extraction isolation valve is in the closed state, and the steam from the steam-side outlet of the newly added external steam cooler is sent into the existing final-stage high-pressure heater to replace the final-stage extraction steam of the high-pressure cylinder. The steam pressure at the steam-side outlet of the newly added external steam cooler is higher than the final-stage extraction steam pressure of the high-pressure cylinder, so that the steam pressure entering the existing final-stage high-pressure heater is higher than the final-stage extraction steam of the high-pressure cylinder, thereby further increasing the feedwater temperature entering the boiler.

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

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

[0019] Preferably, 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, if the heat exchanger is located upstream of the steam compressor, steam below 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 then 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, if the heat exchanger is located between the steam compressor and the newly added external steam cooler, steam below 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 the final stage extraction steam of the high-pressure cylinder, the inlet of the booster module is connected to the extraction steam pipeline via a pipeline, 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 steam connected to the booster module at a pressure lower than the target extraction pressure level is the final stage extraction steam of the high-pressure cylinder of the unit. The booster module inlet is connected to the existing extraction steam pipeline of the final stage high-pressure heater. After being pressurized by the booster module, the final stage extraction steam of the high-pressure cylinder first heats the feedwater in the newly added external steam cooler, and then heats the feedwater in the existing final stage high-pressure heater to improve the feedwater temperature of the unit 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. The final stage extraction steam of the high-pressure cylinder is led out from the front end of the extraction steam isolation valve inlet. When the extraction steam isolation valve is closed, the final stage extraction steam of the high-pressure cylinder can enter the booster module, 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, a circulating pump is installed in the downcomer connecting the steam drum and the header inside the boiler;

[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 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 fed into the newly added external steam cooler and the existing final-stage high-pressure heater for two heating cycles. This is to increase the feedwater temperature at the boiler inlet of the unit under deep peak shaving conditions. The main steam is throttled by operating the existing regulating stage inlet valve group to maintain a certain feedwater pressure and keep the economizer outlet feedwater at a certain degree of subcooling. In addition, the regulating stage inlet valve group can control the main steam while also achieving 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 external steam cooler is installed at the feedwater outlet of the existing final-stage high-pressure feedwater 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 pressure level. The steam-side outlet of the new external steam cooler is connected to the steam inlet of the existing final-stage high-pressure heater. This means that the feedwater is heated twice, in both the new external steam cooler and the existing final-stage high-pressure heater, to increase the feedwater temperature entering the boiler and simultaneously maintain 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 operating 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 system configuration for deep peak shaving operation of a coal-fired power unit 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 system configuration for deep peak-shaving operation of coal-fired power units, such as... Figure 2As shown, the system includes: a boiler, a deaerator system, a high-pressure cylinder, an existing final-stage high-pressure heater, feedwater piping, and steam piping. 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 piping. Water from the bottom of the steam drum flows through the downcomer to the header, is heated by the water-cooled walls, and then returns to the steam drum. The high-pressure cylinder uses a partial steam inlet system and is equipped with a regulating stage. The feedwater piping sequentially includes the deaerator system, the existing final-stage high-pressure heater, and a newly added external steam cooler. The feedwater outlet of the newly added external steam cooler is shown in the diagram. The system connects to the boiler feedwater inlet; the steam pipeline includes a main steam pipeline connecting the boiler steam outlet and the high-pressure cylinder inlet, and an extraction steam pipeline connecting the high-pressure cylinder extraction steam outlet and the existing final-stage high-pressure heater inlet; the main steam pipeline is equipped with a regulating stage inlet valve group, and the extraction steam pipeline is equipped with an extraction steam isolation valve; the steam-side inlet of the newly added external steam cooler is connected to a booster module, the inlet of the booster module receives steam at a pressure lower than the target extraction steam pressure level, and the steam-side outlet of the newly added external steam cooler is connected to the inlet of the existing final-stage high-pressure heater. The target extraction steam pressure level can be understood as the steam that, if using the existing boiler feedwater heating system (i.e., without a booster module, directly enters 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 with a pressure lower than the target extraction pressure is pressurized by the booster module and first heated in the newly added external steam cooler before being heated again in the existing final-stage high-pressure heater. This means the feedwater is heated twice, once in the newly added external steam cooler and once in the existing final-stage high-pressure heater, to increase the unit's feedwater temperature. Simultaneously, the regulating stage inlet steam valve group installed on the main steam pipeline throttles the main steam to maintain a certain feedwater pressure and keep 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] 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.

[0040] 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. It has advantages such as relative safety, low cost, high operational flexibility and good economy.

[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 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 stage extraction steam of the high-pressure cylinder. After the steam below the target extraction pressure level is pressurized by the steam compressor, it first heats the feedwater in the newly added external steam cooler, and then heats the feedwater in the existing final stage high-pressure heater. 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 stage extraction steam of the high-pressure cylinder, ensuring 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. This ensures that the feedwater is heated to a higher temperature, thereby improving the boiler feedwater temperature of the unit under deep peak shaving conditions.

[0042] Furthermore, when the steam from the steam-side outlet of the newly added external steam cooler enters the existing final-stage high-pressure heater to heat the feedwater, the extraction steam isolation valve on the extraction steam pipeline is in the closed state. The steam pressure at the steam-side outlet of the newly added external steam cooler is higher than the final-stage extraction steam pressure of the high-pressure cylinder. With the extraction steam isolation valve closed, the steam from the steam-side outlet of the newly added external steam cooler is sent into the existing final-stage high-pressure heater to replace the final-stage extraction steam of the high-pressure cylinder. The higher steam pressure at the steam-side outlet of the newly added external steam cooler compared to the final-stage extraction steam pressure of the high-pressure cylinder results in a higher steam pressure entering the existing final-stage high-pressure heater than the final-stage extraction steam of the high-pressure cylinder, thereby further increasing the feedwater temperature entering the boiler.

[0043] like Figure 2 As 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 upstream of the steam compressor. By placing the new steam extraction isolation valve upstream of the steam compressor, the flow rate of fluid entering the booster module can be regulated. Furthermore, in the event of a malfunction in the steam compressor, the new external steam cooler, or other equipment, the new steam extraction isolation valve can be closed to prevent steam from entering the booster module, ensuring system safety and improving system operational flexibility.

[0044] Of course, a heat exchanger can also be 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. Steam in the pipeline enters a heat exchanger to heat other working media, such as air, water, or coal, before entering the corresponding equipment. For example, if the heat exchanger is located upstream of the steam compressor, steam below the target extraction pressure level first enters the heat exchanger to heat other working media, such as air, water, or coal. After being pressurized by the steam compressor, it then 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, if the heat exchanger is located between the steam compressor and the newly added external steam cooler, steam below 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, or 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 2As shown, the steam below the target extraction pressure level originates from the final stage extraction steam of 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 connecting 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. After being pressurized by the booster module, the final stage extraction steam of the high-pressure cylinder first heats the feedwater in the newly added external steam cooler, and then heats the feedwater in the existing final stage high-pressure heater to improve the feedwater temperature of the unit under deep peak shaving conditions. The interface of the booster module connecting to the extraction steam pipeline is located upstream of the extraction steam isolation valve. The final stage extraction steam of the high-pressure cylinder is led out from the front end of the extraction steam isolation valve inlet. When the extraction steam isolation valve is closed, the final stage extraction steam of the high-pressure cylinder can enter the booster module, improving the operational flexibility of the unit.

[0046] Of course, in other embodiments, the steam source below the target extraction pressure level is the regenerative extraction steam or reheat system steam or superheater system steam in this unit or other units.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] This utility model provides a system configuration for deep peak-shaving operation of a coal-fired power unit. Taking a 20% THA (Total Heat Amount) operating condition as an example: the feedwater temperature at the boiler 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 to ensure a certain degree of subcooling at the economizer outlet. As the feedwater pressure increases, 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. With the increase in the ratio of main steam temperature, main steam quantity, and reheat steam quantity, both cold reheat steam and hot reheat steam temperatures are increased, thus preventing a significant increase in unit energy consumption and effectively improving the unit's operational economy.

[0051] 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.

[0052] 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.

[0053] This embodiment's scheme: The main generator load is 60MW. The existing final-stage extraction steam pressure and temperature parameters are 0.93MPa and 343℃. After being pressurized by the steam compressor and de-cooled by the newly added external steam cooler, the existing final-stage high-pressure heater inlet steam pressure and temperature parameters are 3.5MPa and 394℃, and the outlet feedwater pressure and temperature parameters are 10.3MPa and 242℃. The water-side temperature rise of the newly added external steam cooler is 7℃, the economizer outlet water temperature is 270℃, the subcooling degree is 43.2℃, the under-enthalpy is 237.1kJ / kg, and the economizer outlet flue gas temperature is 336℃. 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 209 t / h, 9.9 MPa, and 530℃, and 209 t / h, 2.5 MPa, and 440℃, respectively. The effective enthalpy drop per unit working fluid is 123.6 kJ / kg, corresponding to a power output of 7.2 MW. Compared to the isoenthalpy 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 relatively improving the unit's economic efficiency. Furthermore, because the flow rate of each valve in the regulating stage inlet valve group is relatively small, its pressure control of the main steam will be more precise and convenient.

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

2. The 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 pressurized by the steam compressor to a pressure higher than the pressure of the final stage extraction steam of the high-pressure cylinder.

3. The system configuration as described in claim 2, characterized in that, When the steam from the steam-side outlet of the newly added external steam cooler enters the existing final-stage high-pressure heater to heat the feedwater, the extraction steam isolation valve on the extraction steam pipeline is closed, and the steam pressure at the steam-side outlet of the newly added external steam cooler is higher than the final-stage extraction steam pressure of the high-pressure cylinder.

4. The 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 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 system configuration as described in claim 4, characterized in that, The steam below the target extraction pressure level originates from the final stage extraction of 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 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 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 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 system from the economizer outlet to the high-pressure cylinder inlet.

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