Methods and systems for improving the stability of steam soot blowing in heat exchange equipment in boiler flue

Abstract

This invention proposes a method and system for improving the stability of steam soot blowing in heat exchange equipment in boiler flues, belonging to the field of boiler soot blowing technology. The method involves real-time monitoring of the flue gas temperature at the tail end of the boiler flue during boiler operation. This temperature includes the flue gas temperature on the superheater side, the tube wall temperature of the superheater tube, the flue gas temperature on the economizer side, the tube wall temperature of the economizer tube, the flue gas temperature on the air preheater side, and the tube wall temperature of the air preheater tube. By monitoring the flue gas temperature at the tail end of the boiler flue, the start and stop of steam soot blowing are controlled based on this temperature. The flue gas temperature at the tail end of the boiler flue directly reflects boiler load fluctuations and the soot characteristics of the heated surfaces, solving the technical problem of wasted steam due to over-blowing or incomplete soot removal due to under-blowing, leading to unstable soot blowing and ensuring the stability of steam soot blowing.

Description

Technical Field

[0001] This invention belongs to the field of boiler soot blowing technology, and relates to soot blowing technology for heat exchange equipment in circulating fluidized bed boiler flue, specifically a method and system for improving the stability of steam soot blowing in heat exchange equipment in boiler flue. Background Technology

[0002] In traditional technology, to maximize the recovery of waste heat in the flue gas of a circulating fluidized bed (CFB) boiler and improve its thermal efficiency, multiple heat exchange devices are installed at the tail end of the flue gas duct to absorb heat from the flue gas and avoid energy waste. These heat exchange devices include superheaters, economizers, and air preheaters, which are arranged sequentially from front to back along the flue gas flow direction at the tail end of the flue gas duct. The superheater further heats and dries the saturated steam from the steam drum, turning it into superheated steam. The economizer uses the waste heat from the flue gas to heat the boiler feedwater. The air preheater uses the waste heat from the flue gas to heat the air needed for fuel combustion. However, during heat exchange, the flue gas carries a large amount of fly ash particles. When the flue gas washes over the heat exchange surface (tube bank), these particles deposit on the tube wall due to inertial collision, electrostatic adsorption, or condensation adhesion, forming ash deposits or slag. This leads to deterioration of heat exchange and a significant decrease in boiler efficiency. Furthermore, the sulfur oxides in the ash absorb moisture at specific temperatures to form sulfuric acid, causing severe corrosion of the metal tube walls and ultimately perforation and leakage. Therefore, it is necessary to blow soot from these heat exchange devices in the flue to prevent severe ash accumulation.

[0003] Traditional soot blowing for heat exchangers in flues primarily employs steam blowing. This involves high-speed steam jets through nozzles, the resulting kinetic energy and impact force directly striking the accumulated ash, thus loosening the ash deposited on the pipe walls and achieving the purpose of cleaning. However, existing soot blowing control systems suffer from a lack of dynamic adjustment of key parameters such as blowing pressure and frequency based on boiler load fluctuations and the characteristics of the ash on the heated surfaces. This leads to repeated instances of "overblowing" resulting in wasted steam or "underblowing" causing incomplete cleaning, indicating a technical problem of unstable soot blowing. Summary of the Invention

[0004] In response to the technical problem described in the background section above, when performing soot blowing on the heat exchange equipment arranged on the tail heating surface of the circulating fluidized bed boiler flue, the soot blowing control system fails to adjust the key parameters of soot blowing in conjunction with boiler load fluctuations and the ash characteristics of the heating surface, resulting in repeated situations of "overblowing" leading to wasted steam or "underblowing" leading to incomplete ash removal, causing unstable soot blowing. To address this technical problem, the present invention proposes a method and system for improving the steam soot blowing stability of heat exchange equipment in boiler flue.

[0005] This invention monitors the flue gas temperature at the tail end of the boiler flue and controls the start and stop of steam soot blowing based on the flue gas temperature at the tail end of the boiler flue. The flue gas temperature at the tail end of the boiler flue can directly reflect the boiler load fluctuation and the soot characteristics of the heated surface. This solves the technical problem in the prior art where "overblowing" causes wasted steam or "underblowing" causes incomplete soot removal, resulting in unstable soot blowing.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for improving the stability of steam soot blowing in heat exchange equipment in boiler flue gas includes the following steps: S1: During boiler operation, the flue gas temperature at the tail end of the boiler flue is monitored in real time. The flue gas temperature at the tail end of the boiler flue includes the superheater side flue gas temperature, the superheater heating surface tube wall temperature, the economizer side flue gas temperature, the economizer heating surface tube wall temperature, the air preheater side flue gas temperature, and the air preheater heating surface tube wall temperature. S2: The control system determines whether the corresponding air preheater, economizer and superheater have met the soot blowing start conditions according to the set priority, based on the flue gas temperature on the air preheater side, the flue gas temperature on the economizer side and the flue gas temperature on the superheater side. If the conditions for starting soot blowing are not met, continue monitoring; If the soot blowing start-up conditions are met, steam soot blowing will be performed on the air preheater according to the timing control logic based on the flue gas temperature on the air preheater side and the tube wall temperature of the air preheater heating surface, or steam soot blowing will be performed on the economizer based on the flue gas temperature on the economizer side and the tube wall temperature of the economizer heating surface, or steam soot blowing will be performed on the superheater based on the flue gas temperature on the superheater side and the tube wall temperature of the superheater heating surface.

[0007] Further specifying, in S2, the priority setting refers to the priority of the air preheater > the priority of the economizer > the priority of the superheater.

[0008] Further defined, in S2, the soot blowing start condition refers to the soot blowing trigger condition of the air preheater side flue gas temperature reaching the soot blowing trigger condition of the air preheater, the soot blowing trigger condition of the economizer side flue gas temperature reaching the economizer soot blowing trigger condition, or the soot blowing trigger condition of the superheater side flue gas temperature reaching the superheater soot blowing trigger condition.

[0009] Further specified, the soot blowing trigger condition for the air preheater is that the flue gas temperature on the air preheater side is ≥240℃, the soot blowing trigger condition for the economizer is that the flue gas temperature on the economizer side is ≥450℃, and the soot blowing trigger condition for the superheater is that the flue gas temperature on the superheater side is ≥600℃.

[0010] Further specifying, in S2, the timing control logic includes: Within the preset soot blowing time, ① if the flue gas temperature on the heat exchanger side is within the normal operating threshold range and the tube wall temperature of the heat exchanger heating surface is 5°C lower than the normal tube wall temperature, steam soot blowing shall be stopped immediately; ② if the flue gas temperature on the heat exchanger side is within the normal operating threshold range and the tube wall temperature of the heat exchanger heating surface is at the normal tube wall temperature, steam soot blowing shall be stopped until the preset soot blowing time is reached; ③ if the flue gas temperature on the heat exchanger side is lower than the normal operating threshold range and the tube wall temperature of the heat exchanger heating surface is 5°C higher than the normal tube wall temperature, steam soot blowing shall be stopped immediately. If the preset soot blowing time is exceeded and the flue gas temperature on the heat exchanger side is lower than the normal operating threshold range, while the tube wall temperature of the heat exchanger heating surface is at the normal temperature of the tube wall, steam soot blowing will continue until any of the above conditions ①-③ are met, or until the maximum soot blowing time is reached.

[0011] Further specified, the preset blowing time is 60 seconds; the maximum blowing time is 90 seconds.

[0012] Further specifying, in S2, the timing control logic also includes: Within the same heat exchanger, multiple heat exchanger steam branch pipes are arranged from top to bottom; When starting steam soot blowing, each heat exchanger steam branch pipe is started in a top-down order. After the previous heat exchanger steam branch pipe is soot blown, there should be an interval of at least 10 seconds before starting the next heat exchanger steam branch pipe.

[0013] Further specifying, in S2, the timing control logic also includes: when the control system starts the air preheater, economizer and superheater in sequence according to the set priority for steam soot blowing, the interval between two adjacent heat exchangers is at least 30 seconds, wherein the heat exchanger refers to the air preheater, economizer or superheater.

[0014] A system for improving the steam soot blowing stability of heat exchange equipment in a boiler flue, used to achieve the aforementioned method for improving the steam soot blowing stability of heat exchange equipment in a boiler flue, includes a superheater, an economizer, and an air preheater sequentially arranged along the flow direction of the flue gas at the tail end of the boiler flue. The system further includes an inlet main pipe, superheater steam branch pipes, economizer steam branch pipes, and air preheater steam branch pipes. Multiple superheater steam branch pipes are arranged on opposite sides of the superheater, multiple economizer steam branch pipes are arranged on opposite sides of the economizer, and multiple air preheater steam branch pipes are arranged on opposite sides of the air preheater. The system has multiple air preheater steam branch pipes. The inlet of each superheater steam branch pipe, the inlet of each economizer steam branch pipe, and the inlet of each air preheater steam branch pipe are all connected to the main air intake pipe. The outlet of each superheater steam branch pipe is connected to the corresponding nozzle of the superheater, and the corresponding nozzle of the superheater is set towards the heating surface of the superheater. The outlet of each economizer steam branch pipe is connected to the corresponding nozzle of the economizer, and the corresponding nozzle of the economizer is set towards the heating surface of the economizer. The outlet of each air preheater steam branch pipe is connected to the corresponding nozzle of the air preheater, and the corresponding nozzle of the air preheater is set towards the heating surface of the air preheater.

[0015] Further specified, an electric main intake valve and a manual main intake valve are sequentially arranged on the main intake pipe along the steam flow direction; a branch valve group is arranged on each steam branch pipe of the superheater, each steam branch pipe of the economizer, and each steam branch pipe of the air preheater; a temperature measuring unit for measuring the tube wall temperature of the superheater heating surface is arranged on the heating surface of the superheater, a temperature measuring unit for measuring the tube wall temperature of the economizer heating surface is arranged on the heating surface of the economizer, and a temperature measuring unit for measuring the tube wall temperature of the air preheater is arranged on the heating surface of the air preheater; a temperature measuring unit for measuring the flue gas temperature on the superheater side is arranged at the position corresponding to the superheater in the boiler flue, a temperature measuring unit for measuring the flue gas temperature on the economizer side is arranged at the position corresponding to the economizer in the boiler flue, and a temperature measuring unit for measuring the flue gas temperature on the air preheater side is arranged at the position corresponding to the air preheater in the boiler flue.

[0016] Compared with the prior art, the advantages of the present invention are as follows: 1. The present invention provides a method for improving the stability of steam soot blowing in heat exchange equipment in boiler flue. It monitors the flue gas temperature at the tail end of the boiler flue and controls the start and stop of steam soot blowing based on the flue gas temperature at the tail end of the boiler flue. The flue gas temperature at the tail end of the boiler flue can directly reflect the boiler load fluctuation and the soot characteristics of the heated surface. This solves the technical problem of "overblowing" causing steam waste or "underblowing" causing incomplete soot removal, which leads to unstable soot blowing, thus ensuring the stability of steam soot blowing.

[0017] 2. This invention starts the air preheater, economizer and superheater in sequence according to the set priority for steam soot blowing, which can strictly prevent multiple areas from blowing soot at the same time, thereby avoiding the consumption of a large amount of steam during soot blowing operation, which would affect the main steam parameters of the boiler and the stable operation of the steam turbine.

[0018] 3. The timing control logic of the present invention, after the soot blowing of the steam branch pipe of the previous heat exchanger is completed, waits at least 10 seconds before starting the steam branch pipe of the next heat exchanger. At the same time, there is an interval of at least 30 seconds between two adjacent heat exchangers. This mechanism allows the flue gas temperature and steam pressure to return to stability when switching between two adjacent heat exchangers or when switching between two adjacent heat exchanger steam branch pipes, creating stable operating conditions for the next soot blowing and avoiding the cumulative impact of continuous disturbances on boiler combustion and steam-water system.

[0019] 4. The timing control logic of the present invention starts steam soot blowing in the same heat exchanger, and starts each heat exchanger steam branch pipe in a top-to-bottom order to prevent the blown-up ash from falling onto the heating surface of the lower heat exchanger and causing the heating surface of the lower heat exchanger to accumulate ash again. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the method for improving the steam soot blowing stability of heat exchange equipment in boiler flue according to the present invention; Figure 2 A schematic diagram showing the layout of heat exchange equipment in a boiler flue. Explanation of reference numerals in the attached figures: 1-Superheater, 2-Economizer, 3-Air preheater, 4-Inlet main pipe, 5-Inlet electric main valve, 6-Inlet manual main valve, 7-Branch valve group, 8-Superheater steam branch pipe, 9-Economizer steam branch pipe, 10-Air preheater steam branch pipe. Detailed Implementation

[0021] The technical solution of the present invention will be further explained and described below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the embodiments described below.

[0022] See Figure 1 This invention proposes a method for improving the stability of steam soot blowing in heat exchange equipment in boiler flue, comprising the following steps: S1: During boiler operation, the flue gas temperature at the tail end of the boiler flue is monitored in real time. This flue gas temperature includes the superheater side flue gas temperature, the superheater heating surface tube wall temperature, the economizer side flue gas temperature, the economizer heating surface tube wall temperature, the air preheater side flue gas temperature, and the air preheater heating surface tube wall temperature. Specifically, this invention provides a temperature measuring unit on the heating surface of superheater 1 for measuring the superheater heating surface tube wall temperature, and provides a [missing information - likely a unit or component] on the heating surface of economizer 2. A temperature measuring unit for measuring the wall temperature of the economizer heating surface tubes is provided on the heating surface of the air preheater 3. A temperature measuring unit for measuring the flue gas temperature on the superheater side is provided in the boiler flue corresponding to the superheater 1, the economizer side flue gas temperature is provided in the boiler flue corresponding to the economizer 2, and the air preheater side flue gas temperature is provided in the boiler flue corresponding to the air preheater 3. The branch valve group 7 includes a soot blowing inlet pressure regulating valve, a soot blowing inlet valve, and a soot blowing steam pressure regulator. The soot blowing inlet pressure regulating valve and the soot blowing inlet valve are used to regulate the steam flow rates corresponding to the superheater steam branch pipe 8, the economizer steam branch pipe 9, and the air preheater steam branch pipe 10. In a preferred embodiment of the invention, the temperature measuring unit is a thermocouple; however, it can also be other temperature measuring units known to those skilled in the art.

[0023] S2: The control system determines whether the corresponding air preheater, economizer, and superheater have met the soot blowing start conditions according to the set priority, based on the flue gas temperature on the air preheater side, the flue gas temperature on the economizer side, and the flue gas temperature on the superheater side. The set priority is that the priority of the air preheater > the priority of the economizer > the priority of the superheater. The soot blowing start conditions are that the flue gas temperature on the air preheater side reaches the soot blowing trigger condition of the air preheater, the flue gas temperature on the economizer side reaches the soot blowing trigger condition of the economizer, or the flue gas temperature on the superheater side reaches the soot blowing trigger condition of the superheater. If the conditions for starting soot blowing are not met, continue monitoring; If the soot blowing start-up conditions are met, steam soot blowing will be performed on the air preheater according to the timing control logic based on the flue gas temperature on the air preheater side and the tube wall temperature of the air preheater heating surface, or steam soot blowing will be performed on the economizer based on the flue gas temperature on the economizer side and the tube wall temperature of the economizer heating surface, or steam soot blowing will be performed on the superheater based on the flue gas temperature on the superheater side and the tube wall temperature of the superheater heating surface.

[0024] In a preferred embodiment of the present invention, the soot blowing trigger condition for the air preheater is that the flue gas temperature on the air preheater side is ≥240°C, the soot blowing trigger condition for the economizer is that the flue gas temperature on the economizer side is ≥450°C, and the soot blowing trigger condition for the superheater is that the flue gas temperature on the superheater side is ≥600°C.

[0025] In S2, the timing control logic includes: Within the preset soot blowing time, ① if the flue gas temperature on the heat exchanger side is within the normal operating threshold range and the tube wall temperature of the heat exchanger heating surface is 5°C lower than the normal tube wall temperature, steam soot blowing shall be stopped immediately; ② if the flue gas temperature on the heat exchanger side is within the normal operating threshold range and the tube wall temperature of the heat exchanger heating surface is at the normal tube wall temperature, steam soot blowing shall be stopped until the preset soot blowing time is reached; ③ if the flue gas temperature on the heat exchanger side is lower than the normal operating threshold range and the tube wall temperature of the heat exchanger heating surface is 5°C higher than the normal tube wall temperature, steam soot blowing shall be stopped immediately. If the preset soot blowing time is exceeded and the flue gas temperature on the heat exchanger side is lower than the normal operating threshold range, while the tube wall temperature of the heat exchanger heating surface is at the normal temperature, steam soot blowing will continue until any of the conditions ①-③ above are met, or until the maximum soot blowing time is reached. The preset soot blowing time is 60 seconds; the maximum soot blowing time is 90 seconds.

[0026] In a preferred embodiment of the present invention, multiple heat exchanger steam branch pipes are arranged in a sparse manner from top to bottom in the same heat exchanger; when starting steam soot blowing, each heat exchanger steam branch pipe is started in sequence from top to bottom, wherein after the soot blowing of the previous heat exchanger steam branch pipe is completed, there is an interval of at least 10 seconds before starting the next heat exchanger steam branch pipe.

[0027] As a preferred embodiment of the present invention, the timing control logic further includes: when the control system starts the air preheater 3, the economizer 2 and the superheater 1 in sequence according to the set priority for steam soot blowing, the interval between two adjacent heat exchangers is at least 30 seconds, wherein the heat exchanger refers to the air preheater 3, the economizer 2 or the superheater 1.

[0028] The priorities set in this invention are based on a comprehensive consideration of the impact of ash accumulation on boiler safety and efficiency. First priority: Ash accumulation in the air preheater directly reduces primary and secondary air temperatures, worsens combustion conditions, significantly increases flue gas heat loss, and easily causes low-temperature corrosion and flue blockage. It is a core component affecting boiler efficiency and continuous operation, and has the highest priority. Second priority: Ash accumulation in the economizer reduces feedwater preheating efficiency, increases fuel consumption, and ash blockage also increases flue gas resistance, affecting flue gas flow, and has the next highest priority. Third priority: Ash accumulation in the superheater leads to insufficient steam superheating, causing steam parameters to deviate from design values, affecting the safe and stable operation of the turbine, and has the third highest priority.

[0029] See Table 1 below for the temperature parameters of the boiler flue during steam soot blowing.

[0030] Table 1: Temperature parameters of boiler flue gas during steam soot blowing In Table 1, the normal operation threshold refers to the temperature threshold of flue gas as it passes sequentially through the superheater, economizer, and air preheater along the tail flue. As heat is gradually absorbed and the temperature decreases, the normal operation threshold is adjusted downwards synchronously from the superheater to the air preheater. The warning threshold refers to the critical temperature at the initial stage of ash accumulation and the beginning of a decline in heat exchange efficiency. At this point, the control system (specifically the DCS control system) only displays a pop-up notification and does not initiate soot blowing. The soot blowing trigger threshold refers to the critical temperature at which severe ash accumulation occurs, the flue gas temperature rises significantly, and the flue gas discharge temperature increases. Once met, soot blowing in the corresponding area is automatically initiated. The over-limit protection threshold refers to the critical temperature at which extreme ash accumulation easily leads to ash blockage or abnormal heating surfaces. Upon triggering, an emergency interlock soot blowing is immediately initiated, a fault is reported, and load is limited if necessary.

[0031] See Table 2 below for the temperature parameters of the heat exchanger's heating surface during steam soot blowing.

[0032] Table 1: Temperature parameters of the heat exchanger heating surface during steam soot blowing During steam soot blowing, the steam pressure regulating valve (including the electric main inlet valve 5, the manual main inlet valve 6, and the branch valve group 7) cannot adjust the pressure during soot blowing. The steam pressure for soot blowing is determined only based on the flue gas temperature at the tail flue. Specifically, the steam pressure of the soot blower ranges from 1.5 MPa to 2.0 MPa, and the soot blowing pressure increases by 0.025 MPa for every 1°C increase in trigger temperature.

[0033] The core principle of the timing control logic in this invention is: high priority first, then low priority; soot blowing in a single area one by one; time delay between adjacent heat exchangers; simultaneous soot blowing of multiple heat exchangers is strictly prohibited to avoid drastic fluctuations in steam pressure that could affect the boiler's main steam parameters. On the same heat exchanger, soot blowers are started and stopped sequentially from upstream to downstream according to the flue gas flow direction to prevent blown-up ash from clogging downstream equipment again. Operating parameters: the running time of a single soot blower is set to 30-90 seconds, with a 10-second interval between adjacent soot blowers; the soot blowing interval between adjacent heat exchangers is 30 seconds, and the next area is started only after the flue gas temperature and soot blowing steam pressure parameters have stabilized. Intelligent interlock: if the temperature in a certain area drops to the normal threshold and the temperature drop of the heated surface tube wall is greater than 5°C, or the flue gas discharge temperature is lower than the lower limit of the normal value, the remaining soot blowing in that area is immediately terminated, and the system switches to the next area to be triggered to avoid the temperature being too low and affecting the normal operation of the boiler.

[0034] The following example illustrates the method of improving the steam soot blowing stability of heat exchange equipment in boiler flue gas ducts, using the air preheater side flue gas temperature of 244℃ (reaching the first priority soot blowing trigger threshold of 240℃) and the economizer side flue gas temperature of 445℃ (only reaching the warning threshold of 440℃, not triggering soot blowing): S1: During boiler operation, the flue gas temperature at the tail end of the boiler flue is monitored in real time. The flue gas temperature on the air preheater side is 244℃, and the flue gas temperature on the economizer side is 445℃. S2: The control system issues soot blowing commands according to the priority principle of air preheater 3; automatically pre-adjusts the steam header pressure to 1.6MPa, opens the branch valve group 7 on the corresponding steam branch pipe 10 of air preheater 3 to complete the pipe warm-up and prepare for soot blowing; the soot blowers corresponding to air preheater 3 are started one by one in the order of upstream to downstream of flue gas, with each blower running for 60 seconds and adjacent blowers spaced 10 seconds apart; during the soot blowing operation, the control system monitors the flue gas temperature on the air preheater side and the tube wall temperature of the air preheater heating surface in real time. When the tube wall temperature of the air preheater heating surface drops to 205℃, it returns to the normal threshold of 200℃. When the temperature reaches 210℃ and the wall temperature of the air preheater's heating surface is 164℃, immediately stop soot blowing; when the wall temperature of the air preheater's heating surface is not lower than 165℃ and the flue gas temperature on the air preheater side is lower than 200℃, immediately stop soot blowing; when the temperature drops to 205℃ and returns to the normal threshold of 200℃-210℃ and the wall temperature of the air preheater's heating surface is 175℃, blow for 60 seconds; after 60 seconds, if the flue gas temperature is higher than 210℃, increase the soot blowing time until the maximum time of 90 seconds, and immediately stop when the temperature reaches the above conditions within 60 to 90 seconds.

[0035] After the soot blowing of air preheater 3 is completed, close the corresponding soot blowing valve, maintain the steam pressure at 1.8MPa, delay for 30 seconds, and wait for the flue temperature to stabilize.

[0036] After the delay ends, the control system determines that the flue gas temperature on the economizer side is 447℃, which is still within the warning threshold area and has not reached the soot blowing trigger threshold. Therefore, the economizer soot blowing will not be started for the time being, and the warning prompt will only be retained on the interface of the control system for continuous monitoring.

[0037] The control system continued to assess the flue gas temperature on the superheater side, which was within the normal range, indicating no need for soot blowing. Subsequently, the steam header pressure gradually decreased from 1.6 MPa to the reference value of 1.5 MPa, and the soot blowing system entered standby mode.

[0038] See Figure 2This invention also proposes a system for improving the steam soot blowing stability of heat exchange equipment in boiler flue gas, and a method for achieving the above-mentioned improvement of steam soot blowing stability of heat exchange equipment in boiler flue gas. The system includes a superheater 1, an economizer 2, and an air preheater 3 arranged sequentially along the flue gas flow direction on the heating surface at the tail end of the boiler flue gas. The system further includes an inlet main pipe 4, superheater steam branch pipes 8, economizer steam branch pipes 9, and air preheater steam branch pipes 10. Multiple superheater steam branch pipes 8 are arranged on opposite sides of the superheater 1, multiple economizer steam branch pipes 9 are arranged on opposite sides of the economizer 2, and multiple air preheater steam branch pipes 10 are arranged on opposite sides of the air preheater 3. There are multiple air preheater steam branch pipes 10. The inlet of each superheater steam branch pipe 8, the inlet of each economizer steam branch pipe 9, and the inlet of each air preheater steam branch pipe 10 are all connected to the main air inlet pipe 4. The outlet of each superheater steam branch pipe 8 is connected to the nozzle corresponding to superheater 1, and the nozzle corresponding to superheater 1 is set towards the heating surface of superheater 1. The outlet of each economizer steam branch pipe 9 is connected to the nozzle corresponding to economizer 2, and the nozzle corresponding to economizer 2 is set towards the heating surface of economizer 2. The outlet of each air preheater steam branch pipe 10 is connected to the nozzle corresponding to air preheater 3, and the nozzle corresponding to air preheater 3 is set towards the heating surface of air preheater 3.

[0039] It should be noted that the number of superheater steam branch pipes 8 on both sides of superheater 1, the number of economizer steam branch pipes 9 on both sides of economizer 2, and the number of air preheater steam branch pipes 10 on both sides of air preheater 3 can be 2, 3, 4, 5, or even more. The specific number can be set by those skilled in the art according to the requirements of steam soot blowing. In a preferred embodiment of the present invention, the number of superheater steam branch pipes 8 on both sides of superheater 1 is 3, the number of economizer steam branch pipes 9 on both sides of economizer 2 is 3, and the number of air preheater steam branch pipes 10 on both sides of air preheater 3 is 3, that is, there are a total of 18 heat exchanger steam branch pipes in the present invention.

[0040] In a preferred embodiment of the present invention, an electric main valve 5 and a manual main valve 6 are sequentially arranged on the main intake pipe 4 along the steam flow direction; a branch valve group 7 is provided on each superheater steam branch pipe 8, each economizer steam branch pipe 9, and each air preheater steam branch pipe 10; a temperature measuring unit for measuring the tube wall temperature of the superheater heating surface is provided on the heating surface of the superheater 1, a temperature measuring unit for measuring the tube wall temperature of the economizer heating surface is provided on the heating surface of the economizer 2, and a temperature measuring unit for measuring the tube wall temperature of the air preheater is provided on the heating surface of the air preheater 3; a temperature measuring unit for measuring the flue gas temperature on the superheater side is provided at the position corresponding to the superheater 1 in the boiler flue, a temperature measuring unit for measuring the flue gas temperature on the economizer side is provided at the position corresponding to the economizer 2 in the boiler flue, and a temperature measuring unit for measuring the flue gas temperature on the air preheater side is provided at the position corresponding to the air preheater 3 in the boiler flue. Among them, the branch valve group 7 includes a soot blowing inlet pressure regulating valve, a soot blowing inlet valve, and a soot blowing steam pressure transmission.

[0041] The above description is only used to illustrate the technical solutions of the present invention, and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing, those skilled in the art should understand that modifications can still be made to the technical solutions described above, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for improving the stability of steam soot blowing in heat exchange equipment in boiler flue, characterized in that, Includes the following steps: S1: During boiler operation, the flue gas temperature at the tail end of the boiler flue is monitored in real time. The flue gas temperature at the tail end of the boiler flue includes the superheater side flue gas temperature, the superheater heating surface tube wall temperature, the economizer side flue gas temperature, the economizer heating surface tube wall temperature, the air preheater side flue gas temperature, and the air preheater heating surface tube wall temperature. S2: The control system determines whether the corresponding air preheater, economizer and superheater have met the soot blowing start conditions according to the set priority, based on the flue gas temperature on the air preheater side, the flue gas temperature on the economizer side and the flue gas temperature on the superheater side. If the conditions for starting soot blowing are not met, continue monitoring; If the soot blowing start-up conditions are met, steam soot blowing will be performed on the air preheater according to the timing control logic based on the flue gas temperature on the air preheater side and the tube wall temperature of the air preheater heating surface, or steam soot blowing will be performed on the economizer based on the flue gas temperature on the economizer side and the tube wall temperature of the economizer heating surface, or steam soot blowing will be performed on the superheater based on the flue gas temperature on the superheater side and the tube wall temperature of the superheater heating surface.

2. The method for improving the steam soot blowing stability of heat exchange equipment in boiler flue according to claim 1, characterized in that, In S2, the priority is set as follows: priority of air preheater > priority of economizer > priority of superheater.

3. The method for improving the steam soot blowing stability of heat exchange equipment in boiler flue according to claim 1, characterized in that, In S2, the soot blowing start-up condition refers to the flue gas temperature on the air preheater side reaching the soot blowing trigger condition of the air preheater, the flue gas temperature on the economizer side reaching the soot blowing trigger condition of the economizer, or the flue gas temperature on the superheater side reaching the soot blowing trigger condition of the superheater.

4. The method for improving the steam soot blowing stability of heat exchange equipment in boiler flue according to claim 3, characterized in that, The soot blowing trigger condition for the air preheater is that the flue gas temperature on the air preheater side is ≥240℃, the soot blowing trigger condition for the economizer is that the flue gas temperature on the economizer side is ≥450℃, and the soot blowing trigger condition for the superheater is that the flue gas temperature on the superheater side is ≥600℃.

5. The method for improving the steam soot blowing stability of heat exchange equipment in boiler flue according to claim 1, characterized in that, In S2, the timing control logic includes: Within the preset soot blowing time, ① if the flue gas temperature on the heat exchanger side is within the normal operating threshold range and the tube wall temperature of the heat exchanger heating surface is 5°C lower than the normal tube wall temperature, steam soot blowing shall be stopped immediately; ② if the flue gas temperature on the heat exchanger side is within the normal operating threshold range and the tube wall temperature of the heat exchanger heating surface is at the normal tube wall temperature, steam soot blowing shall be stopped until the preset soot blowing time is reached; ③ if the flue gas temperature on the heat exchanger side is lower than the normal operating threshold range and the tube wall temperature of the heat exchanger heating surface is 5°C higher than the normal tube wall temperature, steam soot blowing shall be stopped immediately. If the preset soot blowing time is exceeded and the flue gas temperature on the heat exchanger side is lower than the normal operating threshold range, while the tube wall temperature of the heat exchanger heating surface is at the normal temperature of the tube wall, steam soot blowing will continue until any of the above conditions ①-③ are met, or until the maximum soot blowing time is reached.

6. The method for improving the steam soot blowing stability of heat exchange equipment in boiler flue according to claim 5, characterized in that, The preset blowing time is 60 seconds; the maximum blowing time is 90 seconds.

7. The method for improving the steam soot blowing stability of heat exchange equipment in boiler flue according to claim 5, characterized in that, In S2, the timing control logic further includes: Within the same heat exchanger, multiple heat exchanger steam branch pipes are arranged from top to bottom; When starting steam soot blowing, each heat exchanger steam branch pipe is started in a top-down order. After the previous heat exchanger steam branch pipe is soot blown, there should be an interval of at least 10 seconds before starting the next heat exchanger steam branch pipe.

8. The method for improving the steam soot blowing stability of heat exchange equipment in boiler flue according to claim 7, characterized in that, In the S2, the timing control logic further includes: when the control system starts the air preheater (3), economizer (2) and superheater (1) in sequence according to the set priority for steam soot blowing, the interval between two adjacent heat exchangers is at least 30 seconds, wherein the heat exchanger refers to the air preheater (3), economizer (2) or superheater (1).

9. A system for improving the steam soot blowing stability of heat exchange equipment in a boiler flue, used to implement the method for improving the steam soot blowing stability of heat exchange equipment in a boiler flue as described in any one of claims 1-8, comprising a superheater (1), an economizer (2), and an air preheater (3) sequentially arranged along the flow direction of the flue gas on the heating surface at the tail end of the boiler flue, characterized in that, The system for stabilizing steam soot blowing in the heat exchange equipment of the boiler flue also includes an inlet main pipe (4), superheater steam branch pipes (8), economizer steam branch pipes (9), and air preheater steam branch pipes (10). Multiple superheater steam branch pipes (8) are installed on opposite sides of the superheater (1), multiple economizer steam branch pipes (9) are installed on opposite sides of the economizer (2), and multiple air preheater steam branch pipes (10) are installed on opposite sides of the air preheater (3). The inlet of each superheater steam branch pipe (8), the inlet of each economizer steam branch pipe (9), and the inlet of each air preheater steam branch pipe (10) are all connected. The inlet of each steam branch pipe (10) is connected to the main air intake pipe (4), and the outlet of each superheater steam branch pipe (8) is connected to the nozzle corresponding to the superheater (1). The nozzle corresponding to the superheater (1) is set facing the heating surface of the superheater (1). The outlet of each economizer steam branch pipe (9) is connected to the nozzle corresponding to the economizer (2). The nozzle corresponding to the economizer (2) is set facing the heating surface of the economizer (2). The outlet of each air preheater steam branch pipe (10) is connected to the nozzle corresponding to the air preheater (3). The nozzle corresponding to the air preheater (3) is set facing the heating surface of the air preheater (3).

10. The system for improving the steam soot blowing stability of heat exchange equipment in boiler flue according to claim 9, characterized in that, An electric main valve (5) and a manual main valve (6) are sequentially installed on the main intake pipe (4) along the steam flow direction; a branch valve group (7) is installed on each superheater steam branch pipe (8), each economizer steam branch pipe (9), and each air preheater steam branch pipe (10); a temperature measuring unit for measuring the wall temperature of the superheater heating surface is installed on the heating surface of the superheater (1), and a unit for measuring the wall temperature of the economizer heating surface is installed on the heating surface of the economizer (2). The temperature measuring unit is provided on the heating surface of the air preheater (3) for measuring the temperature of the tube wall of the heating surface of the air preheater; a temperature measuring unit is provided in the boiler flue corresponding to the superheater (1) for measuring the flue gas temperature on the superheater side; a temperature measuring unit is provided in the boiler flue corresponding to the economizer (2) for measuring the flue gas temperature on the economizer side; and a temperature measuring unit is provided in the boiler flue corresponding to the air preheater (3) for measuring the flue gas temperature on the air preheater side.

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