Steam temperature regulation and control method and steam temperature regulation and control system

Abstract

The invention discloses a steam temperature regulation and control method and a steam temperature regulation and control system, and relates to the field of electric power production.The steam temperature regulation and control method comprises the following steps that a steam-pipe wall temperature relation model is established; collecting the pipe wall temperature of a final-stage superheater and a reheater under the conditions of normal load and no peak regulation, comparing the collected temperature with the calculated temperature, and correcting the steam-pipe wall temperature relation model; collecting the pipe wall temperature of a final-stage superheater and a reheater under the conditions of low-load operation and peak regulation, comparing the collected temperature with the calculated temperature, and further correcting the steam-pipe wall temperature relation model; and the pipe wall temperature of the final-stage superheater and the reheater is continuously monitored, and the working state of the pipe wall temperature adjusting device is adjusted according to monitoring data. According to the steam temperature regulation and control method, the steam temperature is judged according to the pipe wall temperature of the final-stage superheater and the pipe wall temperature of the reheater, and the temperature of steam in pipelines is influenced by regulating the temperature of the pipelines of the final-stage superheater and the reheater, so that the temperature of discharged steam meets the working requirement.

Description

Technical Field

[0001] The present invention relates to the field of electric power production, and in particular to a steam pipe outlet temperature control system and a steam pipe outlet temperature control method. Background Art

[0002] Against the backdrop of my country's "dual carbon" goals, my country has begun to build a new power system with renewable energy as the main body. At this stage, a working mode of grid-connected power supply of traditional thermal power generation and renewable energy power generation has been formed. The grid-connected power generation of a large number of renewable energy sources has caused a certain degree of impact on the power grid. For example, the power generation of solar photovoltaic power generation and solar thermal power generation is closely related to the weather and working hours. The power generation of wind power generation and hydropower generation will also be affected by the weather and seasons. The above factors will cause fluctuations in the power generation of renewable energy, which will lead to frequency instability and voltage fluctuations in the power system. In order to meet the highly variable grid load demand, coal-fired power plants are forced to participate in deep peak regulation to balance power demand and supply. Peak regulation refers to the power generation department adapting to the changes in power load by changing the output of the generator to maintain the balance of work power and keep the system frequency stable. For coal-fired power plants, the method of peak regulation is to change the temperature of the steam in the generator set, thereby changing the output power of the generator.

[0003] During the peak-shaving process, the generator set faces problems such as continuous load increase and decrease and low-load operation. Due to the poor regulation performance of the boiler itself, the steam temperature is difficult to control, making it impossible to stably and accurately implement variable load operation and low-load operation. The inventor knows that domestic coal-fired power plants currently perform temperature-changing treatment on the pipes of the final superheater and reheater used to transport steam to the generator during operation, thereby affecting the steam temperature. Commonly used temperature control methods include water spraying / steam cooling method, and regulating the combustion flame center method. The water spraying / steam cooling method is to directly spray water or add low-temperature steam to the high-temperature steam. This method can only be used for cooling and cannot be used for heating, and cannot increase the power of the generator. The method of regulating the combustion flame center is to heat the pipe wall of the final superheater and reheater. This method has low regulation accuracy and can generally only be used for coarse adjustment, and cannot achieve precise peak-shaving. Summary of the invention

[0004] The purpose of the present invention is to provide a steam temperature control method to solve the problems existing in the above-mentioned prior art, establish a steam-tube wall temperature relationship model, judge the steam temperature according to the tube wall temperature of the final superheater and the reheater, when the tube wall temperature is different from the normal working temperature, affect the temperature of the steam in the tube by adjusting the temperature of the final superheater and the reheater tubes, so that the discharged steam temperature meets the working requirements, and the steam-tube wall temperature relationship model can accurately reflect the relationship between the steam temperature and the tube wall temperature under various working conditions after multiple corrections, thereby realizing accurate steam temperature control.

[0005] The present invention also provides a steam temperature control system, in which a tube wall temperature acquisition device and a tube wall temperature adjustment device are arranged on the tube walls of the final superheater and the reheater. The tube wall temperature acquisition device monitors the temperature of the final superheater and the reheater in real time, and can control the working state of the tube wall temperature adjustment device according to the monitoring data. When it is necessary to cool the pipeline, the low-temperature heat exchange medium is directly passed into the tube wall temperature adjustment device without starting the heater. The low-temperature heat exchange medium flowing into the heat exchange tube can play a cooling role. When it is necessary to heat the pipeline, the heater is started, and the heat exchange medium passed into the tube wall temperature adjustment device enters the heat exchange tube after being heated, so as to heat the pipelines of the final superheater and the reheater.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a steam temperature control method, comprising the following steps:

[0008] S1. Establish a steam-tube wall temperature relationship model;

[0009] S2. Collect the tube wall temperature of the final superheater and reheater under normal load and without peak regulation, compare the collected temperature with the calculated temperature, and correct the steam-tube wall temperature relationship model;

[0010] S3, collecting the tube wall temperatures of the final superheater and the reheater under low-load operation and peak load regulation, comparing the collected temperatures with the calculated temperatures, and further correcting the steam-tube wall temperature relationship model;

[0011] S4. Continuously monitor the tube wall temperature of the final stage superheater and reheater, and adjust the working state of the tube wall temperature adjustment device according to the monitoring data.

[0012] Preferably, the steam-tube wall temperature relationship model obtained in step S3 is:

[0013]

[0014] Where: T w,i is the outer wall temperature of the i-th section of the pipeline, unit K; K i is the total heat transfer coefficient between the flue gas in the i-th section and the steam in the tube; T G,i is the high-temperature flue gas temperature of the i-th section, unit K; T in,i is the steam inlet temperature of the i-th section, unit K; h f,i is the convective heat transfer coefficient of steam, in W / (m2·K); w is the thermal conductivity of the tube wall, in units of W / (m2·K); δ w is the pipe wall thickness, in m; T f,i is the working fluid temperature in the i-th section of the pipeline, unit K;

[0015] K i The expression of is,

[0016]

[0017] Where: h G,i is the convective heat transfer coefficient of flue gas, in W / (m 2 ·K); α i is the radiation heat transfer coefficient of the i-th section of the pipeline, unit K 3 ; R is the thermal resistance of the dust layer outside the tube, unit is m 2 K / W;

[0018] T f,i =(T in,i +T out,i ) / 2

[0019] h f,i The expression of is,

[0020]

[0021] h G,i The expression of is,

[0022]

[0023] α i The expression of is,

[0024]

[0025] Where: Nu is the Nusselt number; Re is the Reynolds number; Pr is the Prandtl number; d is the inner diameter of the pipe, in m; D is the outer diameter of the pipe, in m; ε is the system blackness of the wall and the flue gas; σ is the Boltzmann constant.

[0026] Preferably, in step S4, when the tube wall temperatures of the final superheater and the reheater are higher than the normal operating temperature, the tube walls of the final superheater and the reheater are cooled until the tube wall temperatures of the final superheater and the reheater reach the normal operating temperature; when it is monitored that the tube wall temperatures of the final superheater and the reheater are lower than the normal operating temperature, the tube walls of the final superheater and the reheater are heated until the tube wall temperatures of the final superheater and the reheater (2) reach the normal operating temperature.

[0027] The present invention also provides a steam temperature control system, which is based on the above-mentioned steam temperature control method and includes a final superheater, a reheater, a tube wall temperature collection device and a tube wall temperature adjustment device; the tube wall temperature adjustment device includes a heat exchange tube for circulating a heat exchange medium and a heater for heating the heat exchange medium, the heat exchange tube is arranged on the outside of the tube wall of the final superheater and the reheater, the feed end of the heat exchange tube is connected to the discharge end of the heater, the feed end of the heater is connected to the heat exchange medium supply device, and the discharge end of the heat exchange tube is connected to the heat exchange medium recovery device.

[0028] Preferably, the feed end of the heater is connected to the discharge end of the steam turbine unit, and the discharge end of the heat exchange tube is connected to the feed end of the steam turbine unit.

[0029] Preferably, it also includes a molten salt heat storage device, which includes a molten salt heat exchanger. A molten salt heat exchange tube is arranged in the molten salt heat exchanger. The discharge end of the steam turbine unit is connected to the feed end of the molten salt heat exchange tube, and the discharge end of the molten salt heat exchange tube is connected to the feed end of the heater.

[0030] Preferably, the molten salt heat storage device also includes a high-temperature molten salt tank and a low-temperature molten salt tank, the high-temperature molten salt tank is connected to the molten salt heat exchanger, and the low-temperature molten salt tank is connected to the molten salt heat exchanger.

[0031] Preferably, the pipes of the final stage superheater are serpentine pipes, and the pipes of the reheater are serpentine pipes.

[0032] Preferably, the heat exchange tubes are wound around the outer sides of the tube walls of the final stage superheater and the reheater.

[0033] Preferably, the heater is an electric heater.

[0034] Compared with the prior art, the present invention has achieved the following technical effects:

[0035] The present invention provides a steam temperature control method, establishes a steam-tube wall temperature relationship model, judges the steam temperature according to the tube wall temperature of a final superheater and a reheater, and when the tube wall temperature is different from the normal working temperature, affects the temperature of the steam in the tube by adjusting the temperature of the final superheater and the reheater tubes, so that the discharged steam temperature meets the working requirements. The steam-tube wall temperature relationship model can accurately reflect the relationship between the steam temperature and the tube wall temperature under various working conditions after multiple corrections, thereby realizing accurate steam temperature control.

[0036] The present invention also provides a steam temperature control system, in which a tube wall temperature acquisition device and a tube wall temperature adjustment device are arranged on the tube walls of the final superheater and the reheater. The tube wall temperature acquisition device monitors the temperature of the final superheater and the reheater in real time, and can control the working state of the tube wall temperature adjustment device according to the monitoring data. When it is necessary to cool the pipeline, the low-temperature heat exchange medium is directly passed into the tube wall temperature adjustment device without starting the heater. The low-temperature heat exchange medium flowing into the heat exchange tube can play a cooling role. When it is necessary to heat the pipeline, the heater is started, and the heat exchange medium passed into the tube wall temperature adjustment device enters the heat exchange tube after being heated, so as to heat the pipelines of the final superheater and the reheater.

[0037] Compared with the prior art, the present invention also achieves the following technical effects:

[0038] 1. In the present invention, the feed end of the heater is connected to the discharge end of the steam turbine unit, and the steam of the steam turbine unit is used for heat exchange, without the need to use other heat exchange media, thus saving resources and simplifying the equipment structure. The discharge end of the heat exchange tube is connected to the feed end of the steam turbine, and the steam after heat exchange enters the steam turbine unit again for recycling.

[0039] 2. In the present invention, a molten salt heat storage device is also provided. The heat energy in the molten salt heat storage device can adjust the temperature of the steam discharged from the steam turbine unit. When the pipes of the final superheater and the reheater need to be heated up, the molten salt releases heat to the steam, and the steam after absorbing heat enters the pipe wall temperature adjustment device again, which can allow the steam to reach the specified high temperature faster and ensure the heat exchange effect. When the pipes of the final superheater and the reheater need to be cooled down, the molten salt absorbs the heat of the steam, and the steam after releasing heat enters the pipe wall temperature adjustment device again, which can enhance the heat exchange effect of the heat exchange pipe and shorten the cooling time.

[0040] 3. In the present invention, the molten salt heat storage device also includes a high-temperature molten salt tank and a low-temperature molten salt tank, which can separate and store molten salts of different temperatures and can be used at any time, so that the temperature regulation effect of the molten salt heat storage device is more guaranteed.

[0041] 4. In the present invention, the pipes of the final superheater and the reheater are serpentine pipes. In the same space, the serpentine pipes are longer, have sufficient temperature adjustment space, and can provide multiple temperature measurement points, thereby reducing measurement errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1This is a schematic diagram of a pipeline structure of a final stage superheater or reheater in an embodiment of the present invention;

[0044] Figure 2 A schematic diagram of the operating principle of a steam temperature control system in an embodiment of the present invention;

[0045] Figure 3 This is a schematic diagram of the operating principle of a steam temperature control system provided with only heat exchange tubes in an embodiment of the present invention;

[0046] Figure 4 The present invention is a schematic diagram of the operating principle of a steam temperature control system provided with a molten salt heat storage device in an embodiment of the present invention.

[0047] Among them, 1. Final superheater; 2. Reheater; 3. Tube wall temperature collection device; 4. Heat exchange tube; 5. Heater; 6. Steam turbine unit; 7. Molten salt heat exchanger; 8. Molten salt heat exchange tube; 9. High-temperature molten salt tank; 10. Low-temperature molten salt tank; 11. Temperature measurement point; 12. Calculation and control platform. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] The purpose of the present invention is to provide a steam temperature control method to solve the problems existing in the prior art, establish a steam-tube wall temperature relationship model, judge the steam temperature according to the tube wall temperature of the final superheater and the reheater, when the tube wall temperature is different from the normal working temperature, affect the temperature of the steam in the tube by adjusting the temperature of the final superheater and the reheater tubes, so that the discharged steam temperature meets the working requirements, and the steam-tube wall temperature relationship model can accurately reflect the relationship between the steam temperature and the tube wall temperature under various working conditions after multiple corrections, thereby realizing accurate steam temperature control.

[0050] The present invention also provides a steam temperature control system, in which a tube wall temperature acquisition device and a tube wall temperature adjustment device are arranged on the tube walls of the final superheater and the reheater. The tube wall temperature acquisition device monitors the temperature of the final superheater and the reheater in real time, and can control the working state of the tube wall temperature adjustment device according to the monitoring data. When it is necessary to cool the pipeline, the low-temperature heat exchange medium is directly passed into the tube wall temperature adjustment device without starting the heater. The low-temperature heat exchange medium flowing into the heat exchange tube can play a cooling role. When it is necessary to heat the pipeline, the heater is started, and the heat exchange medium passed into the tube wall temperature adjustment device enters the heat exchange tube after being heated, so as to heat the pipelines of the final superheater and the reheater.

[0051] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] The present invention provides a steam temperature control method, which is characterized by comprising the following steps:

[0053] S1. According to the actual structure and materials of the final superheater 1 and the reheater 2, a simulation model is established on the computer. The test parameters are set according to the actual working conditions to conduct simulation tests. According to the simulation test data, the steam temperature and the pipe temperature discharged from the final superheater 1 and the reheater 2 are numerically analyzed to establish a steam-tube wall temperature relationship model.

[0054] S2. Conduct physical tests, where the actual final superheater 1 and reheater 2 are prototype devices of the simulation model, and the test parameters are consistent with the simulation test parameters. Collect the tube wall temperatures of the final superheater 1 and reheater 2 under normal load and without peak regulation, compare the collected temperatures with the calculated temperatures, and modify the steam-tube wall temperature relationship model based on the comparison results to make the calculated values ​​consistent with the actual values.

[0055] S3, collecting the tube wall temperatures of the final superheater 1 and reheater 2 under low-load operation and peak load regulation, comparing the collected temperatures with the calculated temperatures, and further correcting the steam-tube wall temperature relationship model to make its calculated values ​​consistent with the actual values;

[0056] S4. Continuously monitor the tube wall temperature of the final stage superheater and reheater, and adjust the working state of the tube wall temperature adjustment device according to the monitoring data.

[0057] In the power generation process, the product of the boiler is mainly superheated steam, but it may also contain other substances, such as flue gas. Therefore, the influence of impurities must be considered when establishing the steam-tube wall temperature relationship model. In a preferred embodiment, the steam-tube wall temperature relationship model obtained in step S3 is:

[0058]

[0059] Where: T w,i is the outer wall temperature of the i-th section of the pipeline, unit K; K i is the total heat transfer coefficient between the flue gas in the i-th section and the steam in the tube; T G,i is the high-temperature flue gas temperature of the i-th section, unit K; T in,i is the steam inlet temperature of the i-th section, unit K; h f,i is the convective heat transfer coefficient of steam, in W / (m2·K); w is the thermal conductivity of the tube wall, in units of W / (m2·K); δ wis the wall thickness, in m; T f,i is the working fluid temperature in the i-th section of the pipeline, unit K;

[0060] K i The expression of is,

[0061]

[0062] Where: h G,i is the convective heat transfer coefficient of flue gas, in W / (m 2 ·K); α i is the radiation heat transfer coefficient of the i-th section of the pipeline, unit K 3 ; R is the thermal resistance of the dust layer outside the tube, unit is m 2 K / W;

[0063] T f,i =(T in,i +T out,i ) / 2

[0064] h f,i The expression of is,

[0065]

[0066] h G,i The expression of is,

[0067]

[0068] α i The expression of is,

[0069]

[0070] Where: Nu is the Nusselt number; Re is the Reynolds number; Pr is the Prandtl number; d is the inner diameter of the pipe, in m; D is the outer diameter of the pipe, in m; ε is the system blackness of the wall and the flue gas; σ is the Boltzmann constant.

[0071] In a preferred embodiment, in step S4, when the tube wall temperature of the final superheater 1 and the reheater 2 is higher than the normal operating temperature, the tube wall temperature of the final superheater 1 and the reheater 2 is cooled until the tube wall temperature of the final superheater 1 and the reheater 2 reaches the normal operating temperature; when the tube wall temperature of the final superheater 1 and the reheater 2 is lower than the normal operating temperature, the tube wall temperature of the final superheater 1 and the reheater 2 is heated until the tube wall temperature of the final superheater 1 and the reheater 2 reaches the normal operating temperature.

[0072] like Figure 1 and Figure 2As shown, the present invention also provides a steam temperature control system, based on the above-mentioned steam temperature control method, including a final superheater 1, a reheater 2, a tube wall temperature collection device 3 and a tube wall temperature adjustment device, the tube wall temperature adjustment device includes a heat exchange tube 4 for circulating a heat exchange medium and a heater 5 for heating the heat exchange medium, the heat exchange tube 4 is arranged on the outer side of the tube wall of the final superheater 1 and the reheater 2, the feed end of the heat exchange tube 4 is connected to the discharge end of the heater 5, the feed end of the heater 5 is connected to the heat exchange medium supply device, and the discharge end of the heat exchange tube 4 is connected to the heat exchange medium recovery device. The tube wall temperature acquisition device 3 monitors the temperature of each temperature measuring point 11 on the tubes of the final superheater 1 and the reheater 2 in real time, and controls the working state of the tube wall temperature adjustment device according to the monitoring data. When it is necessary to cool the tube, the low-temperature heat exchange medium is directly passed into the tube wall temperature adjustment device without starting the heater 5. The low-temperature heat exchange medium flows into the heat exchange tube 4 to play a cooling role. When it is necessary to heat the tube, the heater 5 is started, and the heat exchange medium passed into the tube wall temperature adjustment device enters the heat exchange tube 4 after being heated 5, so as to heat the tubes of the final superheater 1 and the reheater 2.

[0073] like Figure 3 As shown, in a preferred embodiment, the tube wall temperature adjustment device only includes the heat exchange tube 4, and the heat exchange requirement can be met by directly introducing a heat exchange medium of suitable temperature into the heat exchange tube 4. Alternatively, the heat exchange tube 4 can only introduce a low-temperature heat exchange medium, and when the final superheater 1 and the reheater 2 need to discharge steam with a lower temperature, it can be directly cooled. When the final superheater 1 and the reheater 2 need to discharge steam with a higher temperature, the steam in the final superheater 1 and the reheater 2 can be first raised to a higher temperature and then appropriately cooled.

[0074] like Figure 2 to Figure 4 As shown, in a preferred embodiment, the number of tube wall temperature adjustment devices exceeds one, so different heat exchange tubes 4 are arranged at different positions of the final superheater 1 and the reheater 2. At this time, the temperature information collected by the tube wall temperature acquisition device 3 is first sent to the calculation and control platform 12, and the calculation and control platform 12 issues instructions to each tube wall temperature adjustment device according to the data of each temperature measuring point 11, so as to achieve the purpose of controlling multiple tube wall temperature adjustment devices at the same time by one terminal.

[0075] like Figure 2 As shown, the feed end of the heater 5 is connected to the discharge end of the steam turbine unit 6, and the discharge end of the heat exchange tube 4 is connected to the feed end of the steam turbine unit 6. The steam in the steam turbine unit 6 can be used as a heat exchange medium. The steam during cooling comes from the outlet of the intermediate pressure cylinder of the steam turbine unit 6 or the extraction steam of the first few stages of the low pressure cylinder. The steam source during heating can be the extraction steam of the first few stages of the intermediate pressure cylinder of the steam turbine unit 6.

[0076] like Figure 4As shown, the present invention also includes a molten salt heat storage device, which includes a molten salt heat exchanger 7, a molten salt heat exchange pipe 8 is arranged in the molten salt heat exchanger 7, the discharge end of the steam turbine unit 6 is connected to the feed end of the molten salt heat exchange pipe 8, and the discharge end of the molten salt heat exchange pipe 8 is connected to the feed end of the heater 5. Molten salt capable of absorbing and releasing heat is arranged in the molten salt heat exchanger 7, and when adjusting the pipe temperature of the final superheater 1 and the reheater 2, the heat exchange medium passing through the molten salt heat exchange pipe 8 can first absorb heat or release heat in the molten salt heat exchanger 7, and then enter the pipe wall temperature adjustment device. In a preferred embodiment, the molten salt heat storage device also includes a high-temperature molten salt tank 9 and a low-temperature molten salt tank 10. The high-temperature molten salt tank 9 is connected to the molten salt heat exchanger 7, and the low-temperature molten salt tank 10 is connected to the molten salt heat exchanger 7. The molten salt in the molten salt heat exchanger 7 absorbs heat and is input into the high-temperature molten salt tank 9 for storage, which can effectively ensure the molten salt temperature and provide sufficient high-temperature molten salt during heat exchange. The molten salt releases heat and can be transported to the low-temperature molten salt tank 10 for storage.

[0077] like Figure 1 As shown, the pipeline of the final superheater 1 is a serpentine tube, and the pipeline of the reheater 2 is a serpentine tube. In the same space, the length of the serpentine tube is longer, there is sufficient temperature adjustment space, and multiple temperature measurement points 11 can be provided, thereby reducing the measurement error. In a preferred embodiment, the temperature measurement points 11 are arranged at the feed end, the discharge end, the bend and the straight part of the serpentine tube.

[0078] like Figure 1 As shown, in a preferred embodiment, the heat exchange tube 4 is wound around the outer side of the tube wall of the final stage superheater 1 and the reheater 2. The winding arrangement can effectively cover the tubes of the final stage superheater 1 and the reheater 2, thereby increasing the effective contact area.

[0079] In a preferred embodiment, the heater 5 is an electric heater.

[0080] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A steam temperature control method, characterized in that: The following steps are included: S1. Establish a steam-tube wall temperature relationship model; S2, collecting the tube wall temperatures of the final superheater (1) and the reheater (2) under normal load and without peak regulation, comparing the collected temperatures with the calculated temperatures, and correcting the steam-tube wall temperature relationship model; S3, collecting the tube wall temperatures of the final superheater (1) and the reheater (2) under low-load operation and peak load regulation conditions, comparing the collected temperatures with the calculated temperatures, and further correcting the steam-tube wall temperature relationship model; S4. Continuously monitor the tube wall temperature of the final stage superheater and reheater, and adjust the working state of the tube wall temperature adjustment device according to the monitoring data.

2. The steam temperature control method according to claim 1, characterized in that: The steam-tube wall temperature relationship model obtained in step S3 is: Where: T w,i is the outer wall temperature of the i-th section of the pipeline, unit K; K i is the total heat transfer coefficient between the flue gas in the i-th section and the steam in the tube; T G,i is the high-temperature flue gas temperature of the i-th section, unit K; T in,i is the steam inlet temperature of the i-th section, unit K; h f,i is the convective heat transfer coefficient of steam, in W / (m2·K); w is the thermal conductivity of the tube wall, in units of W / (m2·K); δ w is the wall thickness, in m; T f,i is the working fluid temperature in the i-th section of the pipeline, unit K; K i The expression of is, Where: h G,i is the convective heat transfer coefficient of flue gas, in W / (m 2 K); α i is the radiation heat transfer coefficient of the i-th section of the pipeline, unit K 3 ; R is the thermal resistance of the dust layer outside the tube, unit is m 2 K / W; T f,i =(T in,i +T out,i ) / 2 h f,i The expression of is, h G,i The expression of is, α i The expression of is, Where: Nu is the Nusselt number; Re is the Reynolds number; Pr is the Prandtl number; d is the inner diameter of the pipe, in m; D is the outer diameter of the pipe, in m; ε is the system blackness of the wall and the flue gas; σ is the Boltzmann constant.

3. The steam temperature control method according to claim 1, characterized in that: In step S4, when the tube wall temperature of the final stage superheater (1) and the reheater (2) is higher than the normal operating temperature, the tube wall temperature of the final stage superheater (1) and the reheater (2) is reduced until the tube wall temperature of the final stage superheater (1) and the reheater (2) reaches the normal operating temperature; When the tube wall temperature of the final superheater (1) and the reheater (2) is lower than the normal operating temperature, the tube wall temperature of the final superheater (1) and the reheater (2) is increased until the tube wall temperature of the final superheater (1) and the reheater (2) reaches the normal operating temperature.

4. A steam temperature control system, based on the steam temperature control method according to any one of claims 1 to 3, characterized in that: It comprises a final stage superheater (1), a reheater (2), a tube wall temperature collecting device (3) and a tube wall temperature adjusting device; The tube wall temperature adjustment device comprises a heat exchange tube (4) for circulating a heat exchange medium and a heater (5) for heating the heat exchange medium. The heat exchange tube (4) is arranged on the outer side of the tube wall of the final superheater (1) and the reheater (2). The feed end of the heat exchange tube (4) is connected to the discharge end of the heater (5). The feed end of the heater (5) is connected to a heat exchange medium supply device. The discharge end of the heat exchange tube (4) is connected to a heat exchange medium recovery device.

5. The steam temperature control system according to claim 4, characterized in that: The feed end of the heater (5) is connected to the discharge end of the steam turbine unit (6), and the discharge end of the heat exchange tube (4) is connected to the feed end of the steam turbine unit (6).

6. The steam temperature control system according to claim 5, characterized in that: It also includes a molten salt heat storage device, which includes a molten salt heat exchanger (7). A molten salt heat exchange pipe (8) is arranged in the molten salt heat exchanger (7). The discharge end of the steam turbine unit (6) is connected to the feed end of the molten salt heat exchange pipe (8), and the discharge end of the molten salt heat exchange pipe (8) is connected to the feed end of the heater (5).

7. The steam temperature control system according to claim 6, characterized in that: The molten salt heat storage device further comprises a high-temperature molten salt tank (9) and a low-temperature molten salt tank (10); the high-temperature molten salt tank (9) is connected to the molten salt heat exchanger (7); and the low-temperature molten salt tank (10) is connected to the molten salt heat exchanger (7).

8. The steam temperature control system according to claim 4, characterized in that: The pipeline of the final stage superheater (1) is a serpentine tube, and the pipeline of the reheater (2) is a serpentine tube.

9. The steam temperature control system according to claim 4, characterized in that: The heat exchange tube (4) is wound around the outer side of the tube wall of the final stage superheater (1) and the reheater (2).

10. The steam temperature control system according to claim 4, characterized in that: The heater (5) is an electric heater.

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