Coal-fired power generating unit and method of operating the same

Abstract

The present disclosure relates to a coal-fired power generating unit and a method for operating the same. The coal-fired power generating unit comprises a furnace, an SCR denitration device, a first low-temperature economizer, a main flue, a flue gas bypass, a second low-temperature economizer arranged in the flue gas bypass, a main feedwater pipeline, a first feedwater bypass, and a second feedwater bypass. The coal-fired power generating unit is configured to: when the load rate of the coal-fired power generating unit is 75% to 100%, close the flue gas bypass and the second feedwater bypass, and open the first feedwater bypass; when the load rate of the coal-fired power generating unit is 50% to 75%, open the first feedwater bypass, the flue gas bypass, and the second feedwater bypass; and when the load rate of the coal-fired power generating unit is 30% to 50%, close the first feedwater bypass, open the flue gas bypass and the second feedwater bypass. The coal-fired power generating unit and the method for operating the same provided by the present disclosure can solve the technical problem that the improvement of the variable load rate of the coal-fired power generating unit and the safe and efficient operation of the SCR denitration system cannot be considered simultaneously.

Description

Technical Field

[0001] This disclosure relates to the field of thermal power generation technology, specifically to a coal-fired power generation unit and its operation method. Background Technology

[0002] Wind and solar energy are susceptible to environmental influences and exhibit strong time-varying characteristics, posing a certain threat to the safe operation of the power grid. Meanwhile, coal-fired power generation, as my country's primary source of electricity supply, needs to undertake more peak-shaving and frequency regulation tasks.

[0003] Among related technologies, improving the load change rate of coal-fired power generating units while ensuring the safe and efficient operation of the SCR denitrification system of coal-fired power generating units, so as to improve the power generation efficiency of coal-fired power generating units, is an urgent issue to be addressed. Summary of the Invention

[0004] The purpose of this disclosure is to provide a coal-fired power generation unit and its operation method to solve the technical problem that it is impossible to simultaneously improve the variable load rate of the coal-fired power generation unit and the safe and efficient operation of the SCR denitrification system.

[0005] To achieve the above objectives, according to a first aspect of this disclosure, a coal-fired power generation unit is provided, comprising: a furnace in which coal is burned to generate flue gas; an SCR denitrification device disposed downstream of the furnace along the flow direction of the flue gas for denitrifying the flue gas; a first low-temperature economizer disposed downstream of the SCR denitrification device along the flow direction; a main flue connecting the SCR denitrification device and the furnace; a first low-temperature reheater and a first low-temperature superheater disposed side-by-side in the main flue; a low-temperature reheat-side economizer and a low-temperature superheat-side economizer disposed side-by-side in the main flue, wherein the low-temperature reheat-side economizer is disposed downstream of the first low-temperature reheater along the flow direction, and the low-temperature superheat-side economizer is disposed downstream of the first low-temperature superheater along the flow direction; and a flue gas bypass connected intermittently between the first low-temperature superheater and the low-temperature superheat-side economizer in the main flue to the inlet of the SCR denitrification device. The furnace is equipped with a second low-temperature economizer, a main feedwater pipeline that runs from the feedwater pump outlet through a high-pressure heater, the low-temperature reheat side economizer, and the low-temperature superheat side economizer to the furnace, a first feedwater bypass that connects the feedwater pump outlet through the first low-temperature economizer to the outlet of the high-pressure heater, and a second feedwater bypass that connects the inlet of the low-temperature reheat side economizer through the second low-temperature economizer to the outlet of the low-temperature superheat side economizer. The coal-fired power generation unit is configured such that: when the load rate of the coal-fired power generation unit is 75% to 100%, the flue gas bypass and the second feedwater bypass are closed, and the first feedwater bypass is opened; when the load rate of the coal-fired power generation unit is 50% to 75%, the first feedwater bypass, the flue gas bypass, and the second feedwater bypass are opened; when the load rate of the coal-fired power generation unit is 30% to 50%, the first feedwater bypass is closed, and the flue gas bypass and the second feedwater bypass are opened.

[0006] Optionally, it also includes a third feedwater bypass, which is connected to the furnace from the inlet of the economizer on the low-temperature reheat side. The coal-fired generator set is further configured to open the third feedwater bypass when the load rate of the coal-fired generator set is 30% to 50%.

[0007] Optionally, a third regulating valve with an adjustable opening is provided on the third water supply bypass.

[0008] Optionally, the flue gas bypass is provided with a flue gas damper for opening and closing the flue gas bypass, and the opening degree of the flue gas damper is adjustable.

[0009] Optionally, the maximum amount of flue gas flowing through the flue gas bypass is 20% of the total amount of flue gas generated in the furnace.

[0010] Optionally, a first regulating valve with adjustable opening is provided on the first water supply bypass, and a second regulating valve with adjustable opening is provided on the second water supply bypass.

[0011] Optionally, a second low-temperature reheater and a second low-temperature superheater are also arranged side by side in the main flue. The second low-temperature reheater is arranged between the first low-temperature reheater and the low-temperature reheat-side economizer along the flow direction. The second low-temperature superheater is arranged between the first low-temperature superheater and the low-temperature superheat-side economizer along the flow direction. The flue gas bypass route is connected intermittently between the first low-temperature superheater and the second low-temperature superheater in the main flue to the inlet of the SCR denitrification device.

[0012] According to a second aspect of this disclosure, a method for operating a coal-fired power generation unit is provided. The coal-fired power generation unit includes: a furnace in which coal is burned to generate flue gas; an SCR denitrification device disposed downstream of the furnace along the flow direction of the flue gas for denitrifying the flue gas; a first low-temperature economizer disposed downstream of the SCR denitrification device along the flow direction; a main flue connecting the SCR denitrification device and the furnace; a first low-temperature reheater and a first low-temperature superheater disposed side-by-side in the main flue; a low-temperature reheat-side economizer and a low-temperature superheat-side economizer disposed side-by-side in the main flue, wherein the low-temperature reheat-side economizer is disposed downstream of the first low-temperature reheater along the flow direction, and the low-temperature superheat-side economizer is disposed downstream of the first low-temperature superheater along the flow direction; and a flue gas bypass that is connectable and disconnectable between the first low-temperature superheater and the low-temperature superheat-side economizer in the main flue to the inlet of the SCR denitrification device. The unit is equipped with a second low-temperature economizer, a main feedwater pipeline that runs from the feedwater pump outlet through a high-pressure heater, the low-temperature reheat side economizer, and the low-temperature superheat side economizer to the furnace, a first feedwater bypass that connects the feedwater pump outlet through the first low-temperature economizer to the outlet of the high-pressure heater, and a second feedwater bypass that connects the inlet of the low-temperature reheat side economizer through the second low-temperature economizer to the outlet of the low-temperature superheat side economizer. The operation method of the coal-fired power generation unit includes the following steps: when the load rate of the coal-fired power generation unit is 75% to 100%, the flue gas bypass and the second feedwater bypass are closed, and the first feedwater bypass is opened; when the load rate of the coal-fired power generation unit is 50% to 75%, the first feedwater bypass, the flue gas bypass, and the second feedwater bypass are opened; when the load rate of the coal-fired power generation unit is 30% to 50%, the first feedwater bypass is closed, and the flue gas bypass and the second feedwater bypass are opened.

[0013] Optionally, the coal-fired power generation unit further includes a third feedwater bypass, which is connected to the furnace via the inlet of the economizer on the low-temperature reheat side; the operation method of the coal-fired power generation unit further includes the following steps: when the load rate of the coal-fired power generation unit is 30% to 50%, the third feedwater bypass is opened.

[0014] Optionally, the flue gas bypass is provided with a flue gas damper for opening and closing the flue gas bypass, and the opening degree of the flue gas damper is adjustable; the operation method of the coal-fired power generation unit further includes the following steps: when the load rate of the coal-fired power generation unit is 30% to 75%, the smaller the load rate, the larger the opening degree of the flue gas damper; the larger the load rate, the smaller the opening degree of the flue gas damper.

[0015] Through the above technical solution, during the transition of the coal-fired power generation unit's load rate to a high load rate of 75% to 100%, the temperature of the flue gas generated in the furnace rapidly increases. As the flue gas flows through the first low-temperature reheater and the first low-temperature superheater, the low-temperature reheat side economizer and the low-temperature superheat side economizer in the main flue, and reaches the flue gas inlet of the SCR denitrification device, the flue gas inlet temperature of the SCR denitrification device can be maintained within the high-efficiency operating temperature range. Simultaneously, the temperature of the first low-temperature economizer downstream of the SCR denitrification device also rapidly increases. At this time, the first feedwater bypass is opened to utilize the waste heat of the first low-temperature economizer. For feedwater heating, meaning the high-pressure heater and the waste heat from the coal-fired power plant can simultaneously heat the feedwater, rapidly increasing the feedwater temperature entering the furnace and enabling the coal-fired power plant's load rate to quickly reach 75% to 100%. During the transition from a medium load rate of 50% to 75%, the flue gas bypass can be opened, allowing some of the high-temperature flue gas not cooled by the low-temperature reheat economizer and the low-temperature superheat economizer to directly reach the flue gas inlet of the SCR denitrification unit. This ensures that the flue gas inlet temperature of the SCR denitrification unit remains within its high-efficiency operating temperature range. To prevent the SCR denitrification unit from operating at a reduced load rate and thus lowering the standard coal consumption rate of the coal-fired power generation unit, the second feedwater bypass should be opened to regulate the flue gas temperature in the bypass via the second low-temperature economizer. This not only improves the load change rate of the coal-fired power generation unit but also assists in the peak shaving process. Simultaneously, the first feedwater bypass should be opened to utilize the waste heat from the first low-temperature economizer for feedwater heating. When the load rate of the coal-fired power generation unit shifts towards a lower load rate of 30% to 50%, the flue gas bypass can be opened to allow some of the coal not yet used for low-temperature reheating to be saved. The high-temperature flue gas cooled by the economizer and the low-temperature superheated economizer directly reaches the flue gas inlet of the SCR denitrification unit through the flue gas bypass. This keeps the flue gas inlet temperature of the SCR denitrification unit within the high-efficiency operating temperature range, preventing a decrease in the load rate of the coal-fired power generation unit from affecting the efficient operation of the SCR denitrification unit and reducing the standard coal consumption rate of the coal-fired power generation unit. Simultaneously, the second feedwater bypass is opened to regulate the flue gas temperature in the bypass through the second low-temperature economizer. This not only improves the load change rate of the coal-fired power generation unit but also assists in the peak-shaving process. The first feedwater bypass is then closed. The operating method of the coal-fired power generation unit provided in this disclosure has the same technical effects as the coal-fired power generation unit in the above-described technical solution; therefore, it will not be elaborated upon here to avoid unnecessary repetition.

[0016] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0018] Figure 1 This is a schematic diagram of the structure of a coal-fired power generating unit in a specific embodiment of this disclosure;

[0019] Figure 2 This is a flowchart of the operation method of a coal-fired power generating unit in a specific embodiment of this disclosure.

[0020] Explanation of reference numerals in the attached figures

[0021] 1-Furnace, 2-SCR denitrification unit, 31-First low-temperature economizer, 32-Second low-temperature economizer, 40-Main flue, 41-Flue gas bypass, 411-Flue gas damper, 51-First low-temperature reheater, 52-First low-temperature superheater, 53-Second low-temperature reheater, 54-Second low-temperature superheater, 61-Low-temperature reheat side economizer, 62-Low-temperature superheat side economizer, 70-Main feedwater pipeline, 71-First feedwater bypass, 711-First regulating valve, 72-Second feedwater bypass, 721-Second regulating valve, 73-Third feedwater bypass, 731-Third regulating valve, 74-Feedwater pump outlet, 8-High-pressure heater, 9-Air preheater. Detailed Implementation

[0022] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0023] In this disclosure, unless otherwise stated, directional terms such as "upstream" and "downstream" generally refer to upstream and downstream along the direction of flue gas flow, that is, flue gas flows from upstream to downstream along the flow direction. The terms "first," "second," etc., used in this disclosure are for distinguishing one element from another and do not indicate sequence or importance. Furthermore, when the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0024] According to a first aspect of the embodiments of the present disclosure, a coal-fired power generation unit is provided, with reference to... Figure 1As shown, the coal-fired power generation unit includes a furnace 1, a denitrification device 2, a first low-temperature economizer 31, a main flue 40, a flue gas bypass 41, a second low-temperature economizer 32, a first low-temperature reheater 51 and a first low-temperature superheater 52, a low-temperature reheat side economizer 61 and a low-temperature superheat side economizer 62, a main feedwater pipeline 70, a first feedwater bypass 71 and a second feedwater bypass 72.In this system, coal is burned in furnace 1 to produce flue gas; the SCR denitrification device 2 can be located downstream of furnace 1 along the flow direction of the flue gas to denitrate the flue gas. The temperature at the flue gas inlet of the SCR denitrification device 2 usually needs to be maintained between 320℃ and 400℃ to ensure the safe and efficient operation of the SCR denitrification device 2; the first low-temperature economizer 31 can be located downstream of the SCR denitrification device 2 along the flow direction; the main flue 40 can connect the SCR denitrification device 2 and furnace 1; the first low-temperature reheater 51 and the first low-temperature superheater 52 can be arranged side by side in the main flue 40; the low-temperature reheat side economizer 61 and the low-temperature superheat side economizer 62 can be arranged side by side. The low-temperature reheat economizer 61 is installed in the main flue 40, and the low-temperature reheat economizer 62 can be located downstream of the first low-temperature reheater 51 along the flow direction. The low-temperature superheat economizer 62 can be located downstream of the first low-temperature superheater 52 along the flow direction. The flue gas bypass 41 can be connected intermittently between the first low-temperature superheater 52 and the low-temperature superheat economizer 62 in the main flue 40 to the inlet of the SCR denitrification device 2. That is, the flue gas inlet of the flue gas bypass 41 is opened on the main flue 40 and located between the first low-temperature superheater 52 and the low-temperature superheat economizer 62, so that a part of the high-temperature flue gas flowing through the first low-temperature reheater 51 and the first low-temperature superheater 52 can directly reach the SCR denitrification device 2 via the flue gas bypass 41. The flue gas inlet of the CR denitrification unit 2; the second low-temperature economizer 32 is installed in the flue gas bypass 41; the main feedwater pipeline 70 can reach the furnace 1 from the feedwater pump outlet 74 through the high-pressure heater 8, the low-temperature reheat side economizer 61, and the low-temperature superheat side economizer 62 in sequence; the first feedwater bypass 71 can be connected from the feedwater pump outlet 74 through the first low-temperature economizer 31 to the outlet of the high-pressure heater 8, that is, along the path of feedwater flow, the first low-temperature economizer 31 can be connected in parallel with the high-pressure heater 8 through the first feedwater bypass 71; the second feedwater bypass 72 can be connected from the inlet of the low-temperature reheat side economizer 61 through the second low-temperature economizer 32 to the low-temperature superheat side economizer 62 in a switchable manner. The outlet of 2, i.e., the second low-temperature economizer 32 along the feedwater flow path, can be connected in parallel with the low-temperature reheat side economizer 61 and the low-temperature superheat side economizer 62 through the second feedwater bypass 72; wherein, the coal-fired power generation unit can be configured as follows: when the load rate of the coal-fired power generation unit is 75% to 100%, the flue gas bypass 41 and the second feedwater bypass 72 are closed, and the first feedwater bypass 71 is opened; when the load rate of the coal-fired power generation unit is 50% to 75%, the first feedwater bypass 71, the flue gas bypass 41, and the second feedwater bypass 72 are opened; when the load rate of the coal-fired power generation unit is 30% to 50%, the first feedwater bypass 71 is closed, and the flue gas bypass 41 and the second feedwater bypass 72 are opened.

[0025] Through the above technical solution, during the transition of the load rate of the coal-fired power generation unit provided in this disclosure to a high load rate of 75% to 100%, the temperature of the flue gas generated in the furnace 1 increases rapidly. When the flue gas flows through the first low-temperature reheater 51 and the first low-temperature superheater 52, the low-temperature reheat side economizer 61 and the low-temperature superheat side economizer 62 in the main flue duct 40 and reaches the flue gas inlet of the SCR denitrification device 2, the flue gas inlet temperature of the SCR denitrification device 2 can be maintained within the temperature range for efficient operation. Simultaneously, the temperature of the first low-temperature economizer 31 downstream of the SCR denitrification device 2 also increases rapidly. At this time, the first feedwater bypass 71 is opened to utilize the temperature of the first low-temperature economizer 31. The waste heat from furnace 1 is used to heat the feedwater. This means that the waste heat from the high-pressure heater 8 and the coal-fired generator set can simultaneously heat the feedwater, rapidly increasing the feedwater temperature entering furnace 1 and enabling the coal-fired generator set's load rate to quickly increase to 75% to 100%. During the transition from a medium load rate of 50% to 75% for the coal-fired generator set, the flue gas bypass 41 can be opened. This allows a portion of the high-temperature flue gas, not cooled by the low-temperature reheat economizer 61 and the low-temperature superheat economizer 62, to directly reach the flue gas inlet of the SCR denitrification unit 2 via the bypass 41. This ensures that the flue gas inlet temperature of the SCR denitrification unit 2 remains within its high-efficiency operating range. To prevent the SCR denitrification unit 2 from operating at a reduced load rate and thus reduce the standard coal consumption rate of the coal-fired power generation unit, the second feedwater bypass 72 should be opened to regulate the flue gas temperature in the flue gas bypass 41 via the second low-temperature economizer 32. This not only improves the load change rate of the coal-fired power generation unit but also assists in the peak shaving process. Simultaneously, the first feedwater bypass 71 should be opened to utilize the waste heat from the first low-temperature economizer 31 for feedwater heating. When the load rate of the coal-fired power generation unit shifts towards a lower load rate of 30% to 50%, the flue gas bypass 41 can be opened to allow some of the gas not heated by the low-temperature reheat economizer to reach the lower load rate. The high-temperature flue gas cooled by the economizer 61 and the low-temperature superheated economizer 62 directly reaches the flue gas inlet of the SCR denitrification unit 2 through the flue gas bypass 41, thereby keeping the flue gas inlet temperature of the SCR denitrification unit 2 within the high-efficiency operating temperature range. This prevents the load rate of the coal-fired power generation unit from decreasing and affecting the efficient operation of the SCR denitrification unit 2, and reduces the standard coal consumption rate of the coal-fired power generation unit. At the same time, the second feedwater bypass 72 is opened to regulate the flue gas temperature in the flue gas bypass 41 through the second low-temperature economizer 32. This not only improves the load change rate of the coal-fired power generation unit, but also assists in the peak shaving process of the coal-fired power generation unit. Meanwhile, the first feedwater bypass 71 is closed.

[0026] In addition, refer to Figure 1As shown, the coal-fired power generation unit may also include a third feedwater bypass 73. The third feedwater bypass 73 can be connected to the furnace 1 through the inlet of the low-temperature reheat side economizer 61, that is, along the feedwater flow path, the third feedwater bypass 73 is connected in parallel with the second feedwater bypass 72. The coal-fired power generation unit may also be configured to open the third feedwater bypass 73 when the load rate of the coal-fired power generation unit is 30% to 50%. The third feedwater bypass 73 can directly introduce feedwater that has not been heated by the low-temperature reheat side economizer 61 and the low-temperature superheat side economizer 62 and thus has a lower temperature into the furnace 1, so that the temperature in the furnace 1 drops rapidly, thereby causing the load rate of the coal-fired power generation unit to quickly shift to a low load rate of 30% to 50%. In addition, when the coal-fired power generation unit rapidly changes from a high load rate of 75% to 100% to a medium load rate of 50% to 75%, the third feedwater bypass 73 can also be opened so that the third feedwater bypass 73, the first feedwater bypass 71, the flue gas bypass 41, and the second feedwater bypass 72 work together to help improve the load change rate of the coal-fired power generation unit.

[0027] In addition, when the load rate of the coal-fired power generation unit decreases rapidly, the feedwater flow at the outlet 74 of the feedwater pump can be reduced to decrease the feedwater flow into the furnace 1, thereby reducing the amount of steam generated in the furnace 1, which helps to increase the rate of change of load rate of the coal-fired power generation unit from the load rate to the low load rate.

[0028] In order to control the on / off state of the third water supply bypass 73 and regulate the water supply flow of the third water supply bypass 73, refer to Figure 1 As shown, a third regulating valve 731 with adjustable opening can be installed on the third water supply bypass 73.

[0029] In order to control the on / off state of flue gas bypass 41 and regulate the flow rate of flue gas in flue gas bypass 41, refer to Figure 1 As shown, a flue gas damper 411 for opening and closing the flue gas bypass 41 can be provided in the flue gas bypass 41. The opening degree of the flue gas damper 411 is adjustable to adjust the flow rate of the flue gas in the flue gas bypass 41. When the load rate of the coal-fired power generation unit is between 30% and 75%, the flue gas damper 411 is opened. As the load rate of the coal-fired power generation unit approaches 75%, the flue gas temperature reaching the flue gas inlet of the SCR denitrification device 2 through the main flue duct 40 is higher, resulting in a smaller opening of the flue gas damper 411 to avoid excessively high flue gas inlet temperature of the SCR denitrification device 2. Conversely, when the load rate of the coal-fired power generation unit approaches 30%, the flue gas temperature reaching the flue gas inlet of the SCR denitrification device 2 through the main flue duct 40 is lower, resulting in a larger opening of the flue gas damper 411. This allows more high-temperature flue gas that has not been cooled by the low-temperature reheat side economizer 61 and the low-temperature superheat side economizer 62 to reach the flue gas inlet of the SCR denitrification device 2 through the flue gas bypass 41, preventing the flue gas inlet temperature of the SCR denitrification device 2 from falling below 320℃ and ensuring the safe and efficient operation of the SCR denitrification device 2.

[0030] In a specific embodiment of this disclosure, the maximum amount of flue gas flowing through the flue gas bypass 41 can be 20% of the total amount of flue gas generated by the furnace 1. That is, when the flue gas damper 411 is opened to the maximum opening, up to 20% of the flue gas generated by the furnace 1 can reach the flue gas inlet of the SCR denitrification device 2 through the flue gas bypass 41.

[0031] refer to Figure 1 As shown, in order to control the on / off state of the first water supply bypass 71 and regulate the water supply flow rate in the first water supply bypass 71, a first regulating valve 711 with adjustable opening can be provided on the first water supply bypass 71. In order to control the on / off state of the second water supply bypass 72 and regulate the water supply flow rate in the second water supply bypass 72, a second regulating valve 721 with adjustable opening can be provided on the second water supply bypass 72.

[0032] refer to Figure 1 As shown, a second low-temperature reheater 53 and a second low-temperature superheater 54 can also be arranged side by side in the main flue 40. The second low-temperature reheater 53 can be arranged between the first low-temperature reheater 51 and the low-temperature reheat side economizer 61 along the flow direction. The second low-temperature superheater 54 can be arranged between the first low-temperature superheater 52 and the low-temperature superheat side economizer 62 along the flow direction. At this time, the flue gas bypass 41 can be connected to the inlet of the SCR denitrification device 2 through the first low-temperature superheater 52 and the second low-temperature superheater 54 in the main flue 40.

[0033] According to a second aspect of this disclosure, an operating method for a coal-fired power generating unit is provided, with reference to... Figure 1 and Figure 2 As shown, the coal-fired power generating unit can be the coal-fired power generating unit in the above technical solution, and the operation method of the coal-fired power generating unit includes the following steps:

[0034] S1: When the load rate of the coal-fired power generation unit is 75% to 100%, close the flue gas bypass 41 and the second feedwater bypass 72, and open the first feedwater bypass 71.

[0035] S2: When the load rate of the coal-fired power generation unit is 50% to 75%, open the first water supply bypass 71, the flue gas bypass 41 and the second water supply bypass 72.

[0036] S3: When the load rate of the coal-fired power generation unit is 30% to 50%, close the first feedwater bypass 71 and open the flue gas bypass 41 and the second feedwater bypass 72.

[0037] The operation method of the coal-fired power generation unit provided in this disclosure has the same technical effect as the coal-fired power generation unit in the above technical solution. To avoid unnecessary repetition, it will not be described in detail here.

[0038] refer to Figure 1 As shown, the coal-fired power generating unit may further include a third feedwater bypass 73, which can be switched on and off from the inlet of the low-temperature reheat side economizer 61 to the furnace 1, that is, along the feedwater flow path, the third feedwater bypass 73 is connected in parallel with the second feedwater bypass 72. Correspondingly, the operation method of the coal-fired power generating unit may further include the following steps:

[0039] S31: When the load rate of the coal-fired power generation unit is 30% to 50%, open the third water supply bypass 73.

[0040] Through step S31, the third feedwater bypass 73 can directly introduce feedwater that has not been heated by the low-temperature reheat economizer 61 and the low-temperature superheat economizer 62 and whose temperature has been reduced into the furnace 1, so that the temperature in the furnace 1 drops rapidly, thereby causing the load rate of the coal-fired power generation unit to quickly change to a low load rate of 30% to 50%.

[0041] In addition, the operation method of coal-fired power generating units may also include the following steps:

[0042] S21: When the load rate of the coal-fired power generation unit is 50% to 75%, open the third water supply bypass 73.

[0043] Step S21 enables the third feedwater bypass 73, the first feedwater bypass 71, the flue gas bypass 41, and the second feedwater bypass 72 to work together to help improve the load change rate of the coal-fired power generation unit.

[0044] In order to control the on / off state of flue gas bypass 41 and regulate the flow rate of flue gas in flue gas bypass 41, refer to Figure 1 As shown, a flue gas damper 411 for opening and closing the flue gas bypass 41 can be installed in the flue gas bypass 41. The opening degree of the flue gas damper 411 is adjustable to regulate the flow rate of flue gas in the flue gas bypass 41. The operation method of the coal-fired power generation unit may also include the following steps:

[0045] S4: When the load rate of the coal-fired power generation unit is between 30% and 75%, the smaller the load rate, the larger the opening of the flue gas damper 411; the larger the load rate, the smaller the opening of the flue gas damper 411.

[0046] In step S4, as the load rate of the coal-fired power generation unit approaches 75%, the flue gas temperature at the flue gas inlet of the SCR denitrification device 2 via the main flue duct 40 increases, resulting in a smaller opening of the flue gas damper 411 to prevent the flue gas inlet temperature of the SCR denitrification device 2 from becoming too high. Conversely, as the load rate of the coal-fired power generation unit approaches 30%, the flue gas temperature at the flue gas inlet of the SCR denitrification device 2 via the main flue duct 40 decreases, resulting in a larger opening of the flue gas damper 411. This allows more high-temperature flue gas that has not been cooled by the low-temperature reheat economizer 61 and the low-temperature superheat economizer 62 to reach the flue gas inlet of the SCR denitrification device 2 via the flue gas bypass 41, preventing the flue gas inlet temperature of the SCR denitrification device 2 from falling below 320°C and ensuring the safe and efficient operation of the SCR denitrification device 2.

[0047] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0048] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0049] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A coal-fired power generation unit, comprising: The furnace, in which coal is burned to produce flue gas. The SCR denitrification unit is located downstream of the furnace along the flow direction of the flue gas and is used to denitrify the flue gas. The first low-temperature economizer is located downstream of the SCR denitrification unit along the flow direction. The main flue connects the SCR denitrification unit and the furnace. The first low-temperature reheater and the first low-temperature superheater are arranged side by side in the main flue. A low-temperature reheat side economizer and a low-temperature superheat side economizer are arranged side-by-side in the main flue. The low-temperature reheat side economizer is located downstream of the first low-temperature reheater along the flow direction, and the low-temperature superheat side economizer is located downstream of the first low-temperature superheater along the flow direction. A flue gas bypass is provided, which connects intermittently to the inlet of the SCR denitrification device via the first low-temperature superheater and the low-temperature superheater economizer in the main flue gas duct. A second low-temperature economizer is also provided in the flue gas bypass. The main feedwater pipeline, originating from the feedwater pump outlet, sequentially passes through the high-pressure heater, the low-temperature reheat side economizer, and the low-temperature superheat side economizer before reaching the furnace. The first feedwater bypass, originating from the feedwater pump outlet and connected intermittently via the first cryogenic economizer, is connected to the outlet of the high-pressure heater. The second feedwater bypass is connected from the inlet of the low-temperature reheat side economizer through the second low-temperature economizer to the outlet of the low-temperature superheat side economizer in a way that can be switched on and off. The coal-fired power generation unit is configured such that: when the load rate of the coal-fired power generation unit is 75% to 100%, the flue gas bypass and the second feedwater bypass are closed, and the first feedwater bypass is opened; when the load rate of the coal-fired power generation unit is 50% to 75%, the first feedwater bypass, the flue gas bypass, and the second feedwater bypass are opened; when the load rate of the coal-fired power generation unit is 30% to 50%, the first feedwater bypass is closed, and the flue gas bypass and the second feedwater bypass are opened.

2. The coal-fired power generating unit according to claim 1, characterized in that, It also includes a third feedwater bypass, which is connectable to the furnace via the inlet of the economizer on the low-temperature reheat side. The coal-fired power generation unit is also configured to open the third water supply bypass when the load rate of the coal-fired power generation unit is 30% to 50%.

3. The coal-fired power generating unit according to claim 2, characterized in that, The third water supply bypass is equipped with a third regulating valve with an adjustable opening.

4. The coal-fired power generating unit according to claim 1, characterized in that, The flue gas bypass is provided with a flue gas damper for opening and closing the flue gas bypass, and the opening degree of the flue gas damper is adjustable.

5. The coal-fired power generating unit according to claim 4, characterized in that, The maximum amount of flue gas flowing through the flue gas bypass is 20% of the total amount of flue gas generated in the furnace.

6. The coal-fired power generating unit according to claim 1, characterized in that, The first water supply bypass is equipped with a first regulating valve with adjustable opening, and the second water supply bypass is equipped with a second regulating valve with adjustable opening.

7. The coal-fired power generating unit according to claim 1, characterized in that, A second low-temperature reheater and a second low-temperature superheater are also arranged side by side in the main flue. The second low-temperature reheater is disposed between the first low-temperature reheater and the low-temperature reheat-side economizer along the flow direction, and the second low-temperature superheater is disposed between the first low-temperature superheater and the low-temperature superheat-side economizer along the flow direction. The flue gas bypass route is connectable and disconnectable between the first low-temperature superheater and the second low-temperature superheater in the main flue to the inlet of the SCR denitrification device.

8. A method for operating a coal-fired power generating unit, characterized in that, The coal-fired power generating unit includes: The furnace, in which coal is burned to produce flue gas. The SCR denitrification unit is located downstream of the furnace along the flow direction of the flue gas and is used to denitrify the flue gas. The first low-temperature economizer is located downstream of the SCR denitrification unit along the flow direction. The main flue connects the SCR denitrification unit and the furnace. The first low-temperature reheater and the first low-temperature superheater are arranged side by side in the main flue. A low-temperature reheat side economizer and a low-temperature superheat side economizer are arranged side-by-side in the main flue. The low-temperature reheat side economizer is located downstream of the first low-temperature reheater along the flow direction, and the low-temperature superheat side economizer is located downstream of the first low-temperature superheater along the flow direction. A flue gas bypass is provided, which connects intermittently to the inlet of the SCR denitrification device via the first low-temperature superheater and the low-temperature superheater economizer in the main flue gas duct. A second low-temperature economizer is also provided in the flue gas bypass. The main feedwater pipeline, originating from the feedwater pump outlet, sequentially passes through the high-pressure heater, the low-temperature reheat side economizer, and the low-temperature superheat side economizer before reaching the furnace. The first feedwater bypass, originating from the feedwater pump outlet and connected intermittently via the first cryogenic economizer, is connected to the outlet of the high-pressure heater. The second feedwater bypass is connected from the inlet of the low-temperature reheat side economizer through the second low-temperature economizer to the outlet of the low-temperature superheat side economizer in a way that can be switched on and off. The operation method of the coal-fired power generating unit includes the following steps: When the load rate of the coal-fired power generation unit is 75% to 100%, the flue gas bypass and the second water supply bypass are closed, and the first water supply bypass is opened. When the load rate of the coal-fired power generation unit is 50% to 75%, the first water supply bypass, the flue gas bypass, and the second water supply bypass are opened. When the load rate of the coal-fired power generation unit is 30% to 50%, the first feedwater bypass is closed, and the flue gas bypass and the second feedwater bypass are opened.

9. The operating method of the coal-fired power generating unit according to claim 8, characterized in that, The coal-fired power generating unit also includes a third feedwater bypass, which is connected to the furnace via the inlet of the low-temperature reheat economizer. The operation method of the coal-fired power generating unit also includes the following steps: When the load rate of the coal-fired power generation unit is 30% to 50%, the third water supply bypass is opened.

10. The method for operating a coal-fired power generating unit according to claim 8, characterized in that, The flue gas bypass is provided with a flue gas damper for opening and closing the flue gas bypass, and the opening degree of the flue gas damper is adjustable. The operation method of the coal-fired power generating unit also includes the following steps: When the load rate of the coal-fired power generation unit is between 30% and 75%, the smaller the load rate, the larger the opening of the flue gas damper; the larger the load rate, the smaller the opening of the flue gas damper.

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