Air blowing system for soot deposition at bottom of air bellow of power station boiler

Abstract

The invention discloses an air blowing system for soot deposition at the bottom of a power station boiler air bellow, and belongs to the technical field of thermal power plant boiler dust removal. Air is symmetrically taken through a hot primary air pipeline to form two paths of blowing air main pipes, and the two paths of blowing air main pipes are adjusted through an electric plug plate door and a manual flap door, then extend to the left side and the right side of a hearth in a branched mode and finally are connected to a blowing pipeline horizontally arranged at the bottom of an air bellow. The purging pipeline is fixed above the air bellow truss, purging holes are formed in the bottom of the purging pipeline, high-speed airflow is sprayed out to form a disturbance air film, and accumulated dust is brought into a hearth by secondary air after being suspended. The hot primary air source is adopted to avoid secondary air temperature fluctuation, the symmetrical design is coordinated with a combustion system and does not interfere with air distribution, and the flow speed and the distance of the purging holes give consideration to ash removal efficiency and bottom plate protection. The device can remarkably reduce dust accumulation at the bottom of the air bellow, prevent a welded junction from cracking and improve the operation stability of the boiler, does not need additional air supply equipment, is low in transformation cost and convenient to maintain, and meets the continuous dust removal requirement of the coal-fired power plant boiler.

Description

Technical Field

[0001] The present invention relates to the technical field of power station boilers. More specifically, the present invention relates to a soot blowing air system for the bottom ash accumulation of a power station boiler wind box. Background Art

[0002] In a coal-fired boiler system, the secondary air wind box and the overfire air wind box (OFA wind box) are key air distribution components, and their function is to provide a reasonably distributed secondary air volume for the burners to support fuel combustion, burnout, and control the generation of nitrogen oxides. The hot secondary air enters the wind box after being heated by a rotary air preheater. However, due to the interaction between the flue gas and the air during the heat exchange process of the air preheater, the secondary air inevitably carries some ash particles that have fallen off the surface of the heat exchange elements. When the hot secondary air enters the wind box, due to the increase in the internal flow cross-sectional area of the wind box, the wind speed decreases significantly, resulting in the gradual settlement and accumulation of ash particles at the bottom of the wind box, especially in the areas of the front and rear walls of the furnace and near the partitions. This ash accumulation phenomenon intensifies with the extension of the operation time, forming a local ash layer, which in turn causes a series of problems. Firstly, the ash accumulation at the bottom of the wind box will significantly reduce the effective flow area of the wind box, resulting in uneven distribution of the secondary air. The air volume required by the burners is difficult to be delivered according to the design ratio due to the blockage of the ash accumulation, directly affecting the combustion efficiency and stability. For example, the ash accumulation may cause insufficient secondary air volume in some burners, resulting in incomplete combustion or flame deviation, while the excess air volume in other areas may exacerbate the generation of nitrogen oxides. Secondly, the ash accumulation at the bottom of the wind box will increase the overall weight load of the wind box. Especially under high-temperature conditions, the welds of the wind box are prone to cracking or deformation due to the superposition of thermal stress and mechanical load, resulting in air leakage problems. Air leakage not only reduces the boiler efficiency but also may cause local high-temperature corrosion or affect the normal operation of the burners. In addition, the ash accumulation inside the wind box causes great inconvenience to the maintenance and repair, and it is necessary to frequently stop the furnace for cleaning, increasing the unplanned outage time and affecting the operation economy of the power plant. Traditionally, the cleaning of the ash accumulation at the bottom of the wind box mainly relies on manual cleaning during the boiler shutdown for maintenance. However, manual cleaning has low efficiency, a long cycle, and it is difficult to completely remove the ash in hidden areas. More importantly, this passive cleaning method cannot solve the problem of continuous deposition of ash during operation, and the ash will still accumulate rapidly after the boiler is restarted. In addition, there is a lack of effective on-line ash cleaning means in the existing technologies. Although some solutions attempt to add mechanical vibration or compressed air spraying devices, these methods have obvious limitations: mechanical vibration may cause impact damage to the wind box structure, while compressed air spraying requires an additional air supply system, which not only increases the equipment complexity but also may cause fluctuations in the secondary air temperature due to the mixing of cold air, affecting the combustion stability. During the process of technological improvement, how to achieve online continuous cleaning of ash deposition has become the main challenge. Specifically, the following conditions need to be met: First, the ash cleaning system needs to provide sufficient air flow velocity and pressure to disturb and carry the deposited ash, while avoiding erosion and wear on the bottom plate of the wind box or internal components; Second, the selection of the ash cleaning air source needs to be compatible with the existing air system to avoid adding additional fans or significantly changing the temperature of the secondary air; Third, the system layout needs to be coordinated with the boiler combustion air distribution structure to prevent the normal air volume distribution from being disturbed by the ash cleaning air flow. In addition, engineering practical problems such as pipeline thermal expansion, valve sealing, and anti-blocking of purging holes in high-temperature environments also need to be solved. These technical difficulties have restricted the popularization and application of traditional ash cleaning solutions, making the problem of ash deposition at the bottom of the wind box unable to be effectively solved for a long time. Summary of the Invention

[0003] An object of the present invention is to solve at least the above problems and provide at least the advantages described hereinafter.

[0004] Another object of the present invention is to provide a purging air system for the ash deposition at the bottom of the wind box of a power station boiler. Aiming at the problems of low ash cleaning efficiency, high energy consumption, and complex maintenance of the existing ash deposition cleaning at the bottom of the wind box, the present invention improves the ash cleaning ability through dual-channel independent air intake, multi-stage branched pipe layout, and directional purging structure.

[0005] Another object of the present invention is to solve the problem of unstable purging effect caused by insufficient matching between purging parameters and the wind box structure. The present invention realizes efficient and stable purging by optimizing purging hole parameters, air flow velocity, and pipe diameter design.

[0006] Another object of the present invention is to solve the safety hazard problem of incomplete isolation and pressure residue of the hot primary air during maintenance. The present invention ensures maintenance safety through valve combination design and pressure relief mechanism.

[0007] Another object of the present invention is to solve the problem that the purging air volume cannot be adjusted in real time and dynamically according to the change of ash thickness. The present invention realizes intelligent air volume adjustment through the linkage of sensors and the control system.

[0008] Another object of the present invention is to solve the problem that the fluctuation of purging air pressure affects the system stability. The present invention realizes pressure stability through the linkage control of pressure sensors and valve openings.

[0009] Another object of the present invention is to solve the problem of short service life caused by insufficient high-temperature and wear-resistant performance of the purging pipeline. The present invention improves the durability of the pipeline through composite coatings and groove structures.

[0010] Another object of the present invention is to solve the problem that the pressure pulsation of the branched pipeline affects the purging uniformity. The present invention maintains the stability of the branched pressure through a dynamic pressure compensator.

[0011] Another object of the present invention is to improve the orifice performance through laser drilling and chamfering design in view of the problems of insufficient machining accuracy and anti-wear ability of the purging holes.

[0012] Another object of the present invention is to achieve precise control of the single-hole flow rate through an electric ball valve in view of the problem that the flow rate fluctuation of a single purging hole affects the overall purging effect.

[0013] Another object of the present invention is to achieve multi-region purging coverage through a layered pipeline design in view of the problem that layered ash accumulation cannot be effectively removed.

[0014] To achieve these and other advantages in accordance with the present invention, there is provided a purging air system for ash accumulation at the bottom of a power plant boiler wind box, including a hot primary air intake unit, which includes two independent purging air main pipes led out from the boiler hot primary air system, and an electric slide gate and a manual flap gate are provided on each purging air main pipe; a multi-stage branch pipeline unit, which extends from the purging air main pipes to the left and right sides of the boiler furnace respectively to form a branch pipe system including a plurality of branch pipes, and the branch pipes extend to the front and rear areas of the wind box in front of the furnace; a wind box bottom purging unit, which includes a purging pipeline arranged inside the wind box, which is fixed above the bottom truss of the wind box through a bracket and maintains a predetermined distance (400 - 600 mm) from the wind box bottom plate, purging holes are uniformly distributed along the axial direction on the bottom surface of the purging pipeline, and the jet flow direction of the purging holes is towards the wind box bottom plate; the purging pipeline is communicated with the branch pipes through a distribution header.

[0015] Preferably, the diameter of the purging holes of the present invention is 8 - 12 mm, the pitch L between adjacent purging holes = 0.8W, where W is the width of the wind box; the jet flow velocity of the purging holes is 60 - 110 m / s, and the total mass flow rate of the purging air system is controlled within the range of 0.6 - 7 t / h by adjusting the opening of the electric slide gate; the pipe diameters of the purging air main pipes, branch pipes and purging pipelines decrease gradually, and the air velocity in each section of the pipeline is 20 - 30 m / s; the working parameters provided by the hot primary air intake unit satisfy the wind pressure ≥ 12 kPa and the temperature ≥ 300 °C under the BMCR condition.

[0016] Preferably, the electric slide gate and the manual flap gate of the present invention are arranged in series on the main pipe, and the manual flap gate is arranged on the downstream side of the electric slide gate; an overhaul isolation section is formed between the electric slide gate and the manual flap gate, and an automatic pressure relief valve is arranged in the overhaul isolation section. When the manual flap gate is closed, the pressure relief valve is opened within 5 s to release the residual pressure, and the pressure release rate ≤ 0.3 MPa / s.

[0017] Preferably, a dust accumulation thickness sensor is provided at the bottom of the bellows of the present invention to monitor the dust accumulation thickness data in real time and transmit it to the boiler control system; the data of the dust accumulation thickness sensor needs to be detected more than the threshold value continuously for 3 times to trigger the air volume adjustment: when the dust accumulation thickness is less than the first preset value (10 mm), the boiler control system starts the electric actuator to control the opening degree of the electric slide gate to decrease, so that the purging air flow rate is reduced to 20-30% (0.12-2.1 t / h) of the total mass flow rate; when the dust accumulation thickness is not less than the first preset value and less than the second preset value (20 mm), the boiler control system starts the electric actuator to control the opening degree of the electric slide gate to increase, so that the purging air flow rate is between 30-60% of the total mass flow rate (corresponding to 2.1-4.2 t / h); when the dust accumulation thickness is not less than the second preset value, the boiler control system starts the electric actuator to adjust the opening degree of the electric slide gate to the maximum, so that the purging air flow rate reaches 60-100% of the total mass flow rate (corresponding to 4.2-7 t / h).

[0018] Preferably, a pressure sensor is provided on the upstream side of the maintenance isolation section between the electric slide gate and the manual flap gate of the present invention. Its detection surface is perpendicular to the air flow direction. The pressure sensor is used to detect the purging air pressure data provided by the primary hot air system in real time and transmit it to the boiler control system; when the detected pressure value P real is higher than the preset upper pressure threshold value P high , the electric actuator controls the opening degree of the electric slide gate to decrease at a rate of 2-5% per minute until the purging air flow rate drops to 70-80% of the current set value; when the detected pressure value P real is lower than the preset lower pressure threshold value P low , the electric actuator triggers the full-open mode, and the electric slide gate is opened to the maximum opening degree within 30 s. At the same time, the boiler control system generates a three-level alarm signal; P high =P BMCR ×115%; P low =P BMCR ×85%; where P BMCR is the designed purging air pressure value under the BMCR working condition; P high is the preset upper pressure threshold value; P low is the preset lower pressure threshold value; the detection time interval is 30 s (abnormal values are automatically filtered).

[0019] Preferably, the outer to inner of the purging pipeline of the present invention sequentially includes a high-temperature and oxidation-resistant layer, a nanofiber-reinforced buffer layer, and an ultra-smooth and wear-resistant inner layer; micron-scale groove arrays are distributed on the surface of the inner layer, the groove depth is 0.1-0.3 mm, the width is 0.2-0.5 mm, and they are arranged in a spiral shape along the air flow direction.

[0020] Preferably, a dynamic pressure compensator is provided in the multi-stage branch pipeline unit of the present invention, which includes an energy storage chamber and a piezoelectric ceramic driven throttle valve integrated at the branch pipe interface; when it is detected that the pressure fluctuation of the branch pipe exceeds ±5%, the piezoelectric ceramic driven throttle valve responds within 10 ms, and releases / absorbs the pulsating energy of the air flow through the energy storage chamber to maintain the stable pressure of the branch pipeline.

[0021] Preferably, the purging pipeline of the present invention uses a high-temperature and wear-resistant alloy steel pipe with a coating thickness of 0.3 - 0.5 mm; the purging holes are processed by a laser precision drilling process, and the orifice is designed with a 30° chamfer.

[0022] Preferably, an electric ball valve throttling mechanism is provided in the purging holes of the present invention, and the opening degree is directly controlled by the signal of the pressure sensor; when it is detected that the air flow velocity at the outlet of the purging hole is lower than 60 m / s, the opening degree of the ball valve increases; when it is higher than 100 m / s, the opening degree decreases.

[0023] Preferably, the purging pipeline of the present invention is fixed above the bottom truss of the air box by U-shaped bolts, and the distance between the bottom surface of the purging pipeline and the bottom plate of the air box is 400 - 600 mm; a partition is arranged inside the air box to divide the purging air flow into multiple areas, and branch pipelines are added in the area above the partition to form a stratified purging pipeline, and the stratified purging pipeline is connected in parallel with the main purging pipeline.

[0024] The present invention has at least the following beneficial effects: By reasonably designing the structure and layout of the purging air system, the present invention uses the primary hot air as the purging air source, without the need to additionally increase the air supply equipment, reducing the system complexity and cost. The two independent purging air main pipes cooperate with the electric slide gate and the manual flap gate, which can not only ensure the stable supply of the purging air, but also facilitate the isolation operation during equipment maintenance or repair. The multi-stage branch pipeline unit evenly distributes the purging air to each area of the air box, especially the areas in front of and behind the furnace, ensuring no dead angle in purging. The purging pipeline of the purging unit at the bottom of the air box is fixed above the bottom truss of the air box through brackets and maintains an appropriate distance from the bottom plate of the air box. The purging holes evenly distributed on the bottom surface enable the air flow to effectively impact the bottom of the air box, lift the accumulated ash and enter the furnace with the secondary air, realizing online cleaning, avoiding the long-term accumulation of the accumulated ash, solving the problems such as unreasonable air distribution and ash leakage caused by the accumulated ash at the bottom of the air box, improving the stability and safety of the boiler operation, and reducing the maintenance cost and shutdown maintenance time. The traditional compressed air injection requires an additional air supply system. The present invention uses the primary hot air as the purging air source, which is compatible with the existing air system and avoids the influence of cold air mixing on the secondary air temperature.

[0025] The present invention precisely controls parameters such as the diameter, pitch, and ejected air flow velocity of the purging holes to ensure that the purging air can impact the ash accumulation at the bottom of the air box with sufficient energy, achieving effective cleaning. At the same time, according to the requirements under different operating conditions of the boiler, the total mass flow rate of the purging air system is controlled within a reasonable range by adjusting the opening degree of the electric slide gate, avoiding energy waste caused by excessive air volume or incomplete purging due to insufficient air volume. The diameters of the main purging air pipe, branch pipes, and purging pipelines are designed to gradually decrease, keeping the wind speed within the standard range of 20 - 30 m / s in each section of the pipeline, which can not only ensure the wind transportation efficiency but also reduce pipeline wear. The working parameters provided by the primary hot air extraction unit meet the requirements of wind pressure and temperature under the BMCR condition, ensuring that the purging air system can still operate stably when the boiler is operating at full load, without affecting the temperature of the secondary air, guaranteeing the normal operation of the boiler combustion system, improving the purging effect and system reliability, and optimizing the overall performance of the boiler.

[0026] The series arrangement of the electric slide gate and the manual flap gate in the present invention, and the manual flap gate being arranged downstream of the electric slide gate, form a reasonable valve operation sequence and safety protection mechanism. When the equipment is shut down or under maintenance, the manual flap gate can be closed first, and then isolated through the electric slide gate, ensuring the safety of the operators. The setting of the maintenance isolation section and the installation of the automatic pressure relief valve further improve the safety of the system. When the manual flap gate is closed, the pressure relief valve can quickly open within 5 seconds and release the residual pressure at a pressure release rate of ≤0.3 MPa / s (the pressure release rate ≤0.3 MPa / s meets the requirements of GB / T 12243 - 2021 "Spring Direct Loaded Safety Valves"), preventing damage to equipment or personnel caused by excessive pressure in the pipeline, ensuring the safety and reliability of the purging air system during maintenance, reducing the operation risk, and meeting the safety specifications and requirements of the industrial site.

[0027] The ash accumulation thickness sensor installed at the bottom of the bellows of the present invention can monitor the ash accumulation situation in real time and transmit the data to the boiler control system, realizing the online monitoring of the ash accumulation state inside the bellows. By setting the threshold value of the ash accumulation thickness and based on the logic that the air volume adjustment is triggered only when the detection exceeds the threshold value for three consecutive times, it effectively avoids the misoperation caused by occasional errors or interferences of the sensor, improving the stability and reliability of the system. Automatically adjust the opening degree of the electric slide gate according to different ash accumulation thicknesses, precisely control the purging air flow rate, and make the purging air volume match the actual ash accumulation degree, ensuring both the purging effect and energy conservation. When the ash accumulation thickness is small, reduce the purging air flow rate to 20 - 30% of the total mass flow rate, avoiding unnecessary air volume consumption; when the ash accumulation thickness is in the middle range, adjust the purging air flow rate to 30 - 60% of the total mass flow rate to ensure the purging effect; when the ash accumulation thickness reaches a large value, adjust the opening degree of the electric slide gate to the maximum, making the purging air flow rate reach 60 - 100% of the total mass flow rate to achieve strong purging and quickly clean the ash. The air volume adjustment response time ≤ 15 seconds, which can respond to the ash accumulation change in a timely manner, ensuring the timeliness and effectiveness of the purging operation, improving the intelligent level and automation degree of the boiler operation, reducing manual intervention, and enhancing the overall operation efficiency.

[0028] The present invention installs a pressure sensor on the upstream side of the maintenance isolation section between the electric slide gate and the manual flap gate to detect the purging air pressure data provided by the primary hot air system in real time and transmit it to the boiler control system, providing a basis for the precise control of the purging air volume. By setting the preset pressure upper limit threshold and the preset pressure lower limit threshold and comparing with the actual detected pressure value P real automatically adjust the opening degree of the electric slide gate to achieve the closed-loop control of the purging air pressure. When the detected pressure value is higher than the preset pressure upper limit threshold P high , decrease the opening degree of the electric slide gate at a rate of 2 - 5% per minute, making the purging air flow rate drop to 70 - 80% of the current set value, avoiding excessive purging air volume caused by too high air pressure, resulting in energy waste or impact on the equipment; when the detected pressure value is lower than the preset pressure lower limit threshold P low , trigger the full-open mode of the electric slide gate and open it to the maximum opening degree within 30 seconds, while generating a three-level alarm signal to remind the operator to pay attention, ensuring the sufficient supply of the purging air volume and preventing the purging effect from being affected due to insufficient air pressure. This pressure control mechanism can automatically adjust the purging air volume according to the changes in the boiler operating conditions, ensuring the stable operation of the purging system, improving the adaptability and reliability of the system, further optimizing the operating performance of the boiler, and reducing the operating cost.

[0029] The high-temperature resistant and oxidation-resistant layer, nanofiber-reinforced buffer layer, and ultra-smooth wear-resistant inner layer are sequentially arranged from the outside to the inside of the purging pipeline of the present invention, forming a multi-layer protection structure, which significantly improves the service life and performance of the purging pipeline. The high-temperature resistant and oxidation-resistant layer can effectively resist oxidation corrosion in high-temperature environments and protect the pipeline matrix from damage; the nanofiber-reinforced buffer layer has good buffering and shock-absorbing properties, can absorb the vibration energy generated by the purging air in the pipeline, and reduce the mechanical fatigue and wear of the pipeline; the ultra-smooth wear-resistant inner layer has a smooth surface and a small friction coefficient, can reduce the flow resistance of the purging air in the pipeline, improve the conveying efficiency of the air, and at the same time has excellent wear-resistant performance and can withstand the long-term erosion of high-speed air flow without being easily damaged. The micron-level groove array distributed on the inner layer surface, with the grooves arranged in a spiral shape along the air flow direction, can guide the air flow to form an orderly swirling flow, enhance the disturbance effect of the purging air, improve the cleaning ability of the ash accumulation at the bottom of the air box. At the same time, the depth and width of the grooves are reasonably designed and will not cause too much resistance to the air flow, ensuring the flow rate and pressure of the purging air, further improving the purging effect and the service life of the pipeline, and reducing the maintenance and replacement costs. The high-temperature resistant and oxidation-resistant layer is made of Inconel 625 alloy, the nanofiber layer is a carbon nanotube-reinforced ceramic matrix composite material, and the ultra-smooth inner layer is a WC-Co coating (thickness 0.3 mm).

[0030] The dynamic pressure compensator provided in the multi-stage branch pipeline unit of the present invention includes an energy storage cavity and a piezoelectric ceramic-driven throttle valve integrated at the branch pipe interface, which can effectively address the problem of branch pipe pressure fluctuations. When it is detected that the branch pipe pressure fluctuation exceeds ±5%, the piezoelectric ceramic-driven throttle valve responds quickly within 10 milliseconds, releases or absorbs the air flow pulsation energy through the energy storage cavity, and quickly stabilizes the branch pipeline pressure, ensuring that the purging air can be evenly and stably conveyed to each area of the air box. This dynamic pressure compensation mechanism can effectively reduce the uneven purging air volume caused by pipeline pressure fluctuations, improve the stability of the purging effect, avoid affecting the ash cleaning effect due to excessive or too little local air volume, ensure the uniformity and reliability of the entire bottom purging system of the air box, further optimize the operation performance of the boiler, and reduce the equipment loss and maintenance costs caused by pressure fluctuations.

[0031] The purging pipeline of the present invention adopts a high-temperature and wear-resistant alloy steel pipe, which has excellent high-temperature strength and wear resistance, and can adapt to the working environment of high-temperature and high-speed gas flow scouring inside the boiler air box, ensuring that the purging pipeline is not easily deformed, worn or damaged during long-term operation, and extending the service life of the pipeline. A special coating with a thickness of 0.3 - 0.5 mm further improves the high-temperature and wear resistance of the pipeline and enhances the protection ability of the pipeline. The purging holes are processed by a laser precision drilling process, and the orifice is designed with a 30° chamfer, which can ensure the dimensional accuracy and shape accuracy of the purging holes, so that the purging air is ejected at the best angle and speed, improving the purging effect. The laser drilling process can also achieve precise processing of micro-apertures, meet the design requirements of the purging hole diameter of 8 - 12 mm, ensure the uniform distribution and precise spraying of the purging air, further improve the performance and reliability of the purging system, reduce the maintenance and replacement frequency, and save the operation cost.

[0032] The electric ball valve throttling mechanism set inside the purging hole of the present invention directly controls the opening degree through the signal of the pressure sensor, realizing precise adjustment of the air flow velocity at the outlet of the purging hole. When it is detected that the air flow velocity at the outlet of the purging hole is lower than 60 m / s, the opening degree of the ball valve automatically increases to increase the air volume and improve the purging intensity; when the air flow velocity is higher than 100 m / s, the opening degree of the ball valve automatically decreases to reduce the air volume and avoid energy waste or equipment damage caused by excessive purging. This automatic adjustment mechanism can adjust the air volume and velocity of the purging hole in real time according to the actual purging requirements, ensure the optimization of the purging effect, improve the intelligent level and automation degree of the system, reduce manual intervention, further optimize the operation efficiency and economy of the boiler, and extend the service life of the purging pipeline and related equipment.

[0033] The purging pipeline of the present invention is fixed above the bottom truss of the air box by U-bolts. This fixing method is simple and reliable, convenient for installation and disassembly, and can adapt to the structural characteristics and space limitations inside the air box at the same time. The distance between the bottom surface of the purging pipeline and the bottom plate of the air box is 400 - 600 mm, which not only ensures that the purging air can effectively cover the bottom of the air box, but also avoids the purging damage of the bottom plate of the air box caused by too close distance or the poor purging effect caused by too far distance. The partition plate set inside the air box divides the purging air flow into multiple areas, and branch pipelines are added in the area above the partition plate to form a stratified purging pipeline, which is connected in parallel with the main purging pipeline, realizing stratified and zoned purging of the internal space of the air box. This design can distribute the purging air more evenly, ensure that the ash accumulation in all corners of the air box can be effectively cleaned, improve the comprehensiveness and thoroughness of purging, further optimize the purging effect, reduce the impact of ash accumulation on the operation of the boiler, improve the stability and economy of the boiler operation, and at the same time, the parallel design of the stratified purging pipeline also increases the redundancy and reliability of the system, facilitating maintenance and repair when some pipelines have problems.

[0034] Other advantages, objects and features of the present invention will be partly reflected by the following description, and partly will be understood by those skilled in the art through the research and practice of the present invention. Brief Description of the Drawings

[0035] Figure 1 It is a schematic structural diagram of the ash blowing air system for the bottom of the plenum chamber of a power station boiler according to the present invention. Detailed Embodiments

[0036] The following further detailed description of the present invention is made in conjunction with the drawings and embodiments, so that those skilled in the art can implement it according to the description in the specification.

[0037] It should be understood that the terms such as "having", "comprising" and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0038] It should be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0039] In the description of the present invention, the orientation or positional relationship indicated by the terms "transverse", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0040] The present invention provides an ash blowing air system for the bottom of the plenum chamber of a power station boiler, which includes: A hot primary air intake unit, which includes two independent main purge air pipes led out from the boiler hot primary air system. An electric slide gate and a manual flap gate are provided on each main purge air pipe. There are various models of electric slide gates available on the market, such as the common Z-type electric slide valve, which has the characteristics of good sealing performance and flexible operation, and can be applied to the boiler environment of high temperature and high pressure; the manual flap gate can be a flap gate made of cast steel, which has the advantages of high temperature resistance and high strength. The pipe diameters of the two main purge air pipes can be determined according to the actual air volume requirements, and generally can be selected in the range of DN200 - DN400. For example, a DN300 pipe is widely used in many boiler systems and can meet the large air volume transportation requirements. In the assembly position, the air intake point is usually set at the downstream of the hot primary air at the rear of the furnace, which can ensure the stability of air intake and the sufficiency of air pressure, and at the same time facilitate the layout and connection of the pipes.

[0041] Multi-stage branched pipeline unit, which extends from the main purging air pipe to the left and right sides of the boiler furnace respectively, forming a branch pipe system including multiple branch pipes, and the branch pipes extend to the front and rear areas of the wind box in front of the furnace. The pipe diameters of the branch pipes gradually decrease, generally selectable according to 1 / 2 - 1 / 3 of the main pipe diameter, and the branch pipes can select pipes with DN150 - DN200. In terms of material selection, ordinary carbon steel pipes can be used, which have the advantages of high strength, low cost, easy processing, etc., and can adapt to the working environment inside the boiler wind box. The layout of the branch pipes should be reasonably designed according to the structure and size of the wind box to ensure that the purging air can be evenly distributed to each area of the wind box, especially pay attention to the coverage of the front and rear areas of the furnace to avoid purging dead angles.

[0042] Bottom purging unit of the wind box, which includes a purging pipeline arranged inside the wind box, fixed above the bottom truss of the wind box through brackets and maintaining a predetermined distance (400 - 600mm) from the bottom plate of the wind box. The bottom surface of the purging pipeline is evenly distributed with purging holes along the axis, and the air flow direction ejected from the purging holes is towards the bottom plate of the wind box; the purging pipeline is connected to the branch pipes through a distribution header. The purging pipeline can select ordinary seamless steel pipes, which have good mechanical properties and pressure resistance, and can withstand the impact of high-speed air flow. The brackets can be made of angle steel or channel steel, which have the characteristics of high strength and good stability, and can reliably fix the purging pipeline. The diameter of the purging holes is generally in the range of 8 - 12mm, and the pitch L between adjacent purging holes = 0.8W (W is the width of the wind box, applicable to wind boxes with a width ≤ 3m, for wide wind boxes, L = 0.5W). For example, for a wind box with a width of 2m, the pitch can be set to about 1.6m. The purging holes can be processed by laser drilling technology to ensure the accuracy and quality of the holes. The distribution header can be selected and welded from common pressure vessel steel plates, which have sufficient strength and sealing performance, and can evenly distribute the air from the branch pipes into the purging pipeline.

[0043] The working process of this technical solution: During the working process, the hot primary air enters from the two independent main purging air pipes of the air intake unit, and after being adjusted by the electric slide gate and the manual flap gate, it is respectively transported to the multi-stage branched pipeline units on the left and right sides of the boiler furnace. The multi-stage branched pipeline unit distributes the air step by step to each branch pipe, and finally extends to the front and rear areas of the wind box in front of the furnace. After the air reaches the bottom purging unit of the wind box, it is evenly distributed into the purging pipeline through the distribution header. The purging holes on the bottom surface of the purging pipeline eject high-speed air flow, forming a disturbing air film, which makes the ash accumulated at the bottom of the wind box rise and suspend, and then is carried into the furnace by the secondary air, realizing the continuous cleaning of the ash accumulated at the bottom of the wind box.

[0044] The diameter and pitch of the purging holes are important parameters affecting the purging effect. When setting the diameter of the purging holes, factors such as the flow rate and pressure of the purging air, as well as the particle size of the ash accumulated at the bottom of the air box, need to be comprehensively considered. Generally speaking, larger hole diameters can provide higher air speeds and flow rates, but may lead to uneven air distribution; smaller hole diameters can make the air more evenly distributed, but may require higher air pressures to ensure sufficient purging force. In practical applications, the optimal hole diameter and pitch can be determined through on-site tests. For example, during the renovation of a 660MW ultra-supercritical boiler, after multiple tests, it was finally determined that when the purging hole diameter is 10mm and the pitch is 500mm, the purging effect is the best.

[0045] The purging air system for the ash accumulated at the bottom of the air box of a power station boiler provided by this technical solution, through the reasonable design of the hot primary air intake unit, multi-stage branch pipe unit and the air box bottom purging unit, uses the hot primary air as the purging air source, without the need to additionally increase air supply equipment, reducing the system complexity and cost. The two independent purging air main pipes cooperate with the electric slide gate and the manual flap gate, which can not only ensure the stable supply of the purging air, but also facilitate the isolation operation during equipment maintenance or repair. The multi-stage branch pipe unit evenly distributes the purging air to each area of the air box, especially the areas in front of and behind the furnace, ensuring no dead corners in purging. The purging pipes of the air box bottom purging unit are fixed above the bottom truss of the air box through brackets and maintain an appropriate distance from the air box bottom plate. The purging holes evenly distributed on the bottom surface enable the air flow to effectively impact the bottom of the air box, lift the accumulated ash and enter the furnace with the secondary air, realizing on-line cleaning, avoiding the long-term accumulation of ash, solving problems such as unreasonable air distribution and air box cracking and ash leakage caused by the ash accumulated at the bottom of the air box, improving the stability and safety of boiler operation, and reducing the maintenance cost and shutdown maintenance time.

[0046] Combined with the attached Figure 1 Taking a 660MW ultra-supercritical boiler as an example for detailed description: A 660MW ultra-supercritical boiler is equipped with three layers of burners at the front and back of the furnace, one layer of OFA nozzles, and a burner annular air box and an OFA annular air box are respectively set. A partition is set between the second layer of burners and the third layer of burners in the burner air box. The air preheater adopts the Howden rotary regenerative three-compartment design. Inevitably, the secondary air will carry high-temperature dust into the air box after passing through the air preheater. After long-term accumulation, ash accumulation will occur at the front and rear walls of the OFA air box and the burner air box. In order to achieve the purging purpose, the purging air system provided by this technical solution is adopted.

[0047] This boiler has a left coal bunker layout structure. It is considered to take the air intake points at the positions where the hot primary air descends from the rear of the furnace. There are two air intake points. The main pipe is equipped with an electric slide gate and a manual flap gate, and then it is divided into two branch pipes respectively to enter the burner wind box and the OFA wind box from the left and right sides at the rear of the furnace. Inside the wind box, each branch pipe is further divided into two branches to enter the front and rear distribution headers of the furnace. Pipes with a certain distance between the purge holes are connected between the distribution headers to purge the bottom plate and partition of the wind box, so as to form a purge air film at the bottom of the wind box, making the ash deposition not easy to accumulate on the ground and always in a disturbed suspension state, and being carried into the furnace by the secondary air. The wind pressure of the hot primary air pipeline of this power plant under the BMCR condition is 13.14 KPa, the primary air temperature is 333 °C, and the primary air mass flow rate is 384 t / h. After calculation, the main purge air pipeline is selected as Φ273, the branch pipe is Φ219, the secondary branch pipe is Φ159, the purge pipe specification is Φ89, and the purge pipeline is provided with Φ10 purge holes at a pitch of 500, and the number of holes is about 500. When the purge air mass flow rate is in the range of 4 - 6 t / h, the flow velocities of the main pipe and the branch pipes are within the standard range, and the flow velocity of the purge holes is in the range of 70 - 110 m / s, all of which can achieve a good purge effect.

[0048] In another technical solution, the diameter of the purge hole is 8 - 12 mm, and the pitch L between adjacent purge holes = 0.8W, where W is the width of the wind box; The ejection air flow velocity of the purge hole is 60 - 110 m / s, and the total mass flow rate of the purge air system is controlled within the range of 0.6 - 7 t / h by adjusting the opening of the electric slide gate; The diameters of the purge air main pipe, the branch pipes and the purge pipes decrease gradually, and the air flow velocities in each section of the pipeline are 20 - 30 m / s; The working parameters provided by the hot primary air intake unit meet the wind pressure ≥ 12 kPa and temperature ≥ 300 °C under the BMCR condition (Boiler Maximum Continuous Rating).

[0049] In this technical solution, the diameter of the purging holes is set to 8 - 12 mm. The selection of this range is based on the particle size of the ash accumulation at the bottom of the air box and the kinetic energy requirement of the purging air. When the diameter of the purging holes is relatively small, such as less than 8 mm, a higher wind speed can be provided, but the flow rate is relatively small; while when the diameter is relatively large, such as greater than 12 mm, the flow rate increases, but the wind speed will decrease. The pitch L between adjacent purging holes = 0.8W (W is the width of the air box). This pitch setting is aimed at ensuring the uniform distribution of the purging air at the bottom of the air box and avoiding purging dead zones. For example, for an air box with a width of 2 m, the pitch can be set to about 1.6 m. The ejection air flow speed of the purging holes is 60 - 110 m / s. This speed range can ensure that the purging air has sufficient energy to lift and suspend the ash accumulation, and at the same time will not cause excessive erosion to the bottom plate of the air box. The unified air flow speed range is 60 - 100 m / s (delete the upper limit of 110 m / s). Under normal operating conditions, the flow rate is maintained at 70 - 100 m / s, and in extreme operating conditions, it can be reduced to 60 m / s; The total mass flow rate of the purging air system is controlled within the range of 0.6 - 7 t / h (BMCR operating condition) by adjusting the opening of the electric slide gate. The determination of this flow rate range comprehensively considers the different operating conditions of the boiler and the cleaning requirements of the ash accumulation at the bottom of the air box. During low-load operation, a smaller flow rate can meet the purging requirements, while during high-load operation or when the ash accumulation is relatively serious, a larger flow rate is required to ensure the purging effect. The opening adjustment of the electric slide gate can adopt an electric actuator. There are various models of electric actuators commonly available on the market. For example, an actuator of a certain brand model has characteristics such as high adjustment accuracy and fast response speed, and can meet the requirements of the flow rate control of the purging air system.

[0050] The diameters of the main purging air pipe, branch pipes and purging pipes decrease gradually. The wind speeds in each section of the pipes are 20 - 30 m / s. The design of the pipe diameters needs to be calculated and selected according to the requirements of the air volume and wind speed. For example, a larger pipe diameter, such as DN300, can be selected for the main purging air pipe to ensure sufficient air volume transportation; the branch pipes and purging pipes gradually reduce the pipe diameters according to the air volume distribution. For example, DN200 can be selected for the branch pipes and DN150 for the purging pipes, etc. The wind speed is controlled within the range of 20 - 30 m / s, which can not only ensure the air transportation efficiency, but also reduce pipe wear and avoid noise problems caused by too high wind speed.

[0051] The working parameters provided by the hot primary air extraction unit meet the requirements of wind pressure ≥ 12 kPa and temperature ≥ 300 °C under BMCR operating conditions. This parameter requirement ensures that the purging air system can still operate stably during the full-load operation of the boiler and will not affect the purging effect due to insufficient wind pressure or temperature. In practical applications, the air extraction unit can be reasonably selected and designed by monitoring the wind pressure and temperature of the hot primary air system and combining with the operating data of the boiler to meet this parameter requirement.

[0052] In this technical solution, by precisely controlling parameters such as the diameter, pitch, and ejected air flow velocity of the purging holes, it is ensured that the purging air can impact the ash accumulation at the bottom of the air box with sufficient energy to achieve effective cleaning. At the same time, according to the requirements under different operating conditions of the boiler, by adjusting the opening degree of the electric slide gate, the total mass flow rate of the purging air system is controlled within a reasonable range, avoiding energy waste caused by excessive air volume or incomplete purging due to insufficient air volume. The pipe diameters of the main purging air pipe, branch pipes, and purging pipes are designed to gradually decrease, keeping the wind speed within the standard range of 20 - 30 m / s in each section of the pipe, which can not only ensure the wind transportation efficiency but also reduce pipe wear. The working parameters provided by the hot primary air extraction unit meet the requirements of the wind pressure and temperature under the BMCR condition, ensuring that the purging air system can still operate stably when the boiler is running at full load, without affecting the temperature of the secondary air, guaranteeing the normal operation of the boiler combustion system, improving the purging effect and system reliability, and optimizing the overall performance of the boiler.

[0053] In another technical solution, for the purging air system at the bottom of the air box of a power station boiler, the electric slide gate and the manual flap gate are arranged in series on the main pipe, and the manual flap gate is set on the downstream side of the electric slide gate; An overhaul isolation section is formed between the electric slide gate and the manual flap gate, and an automatic pressure relief valve is set in the overhaul isolation section. When the manual flap gate is closed, the pressure relief valve opens within 5 s to release the residual pressure, and the pressure release rate ≤ 0.3 MPa / s.

[0054] In this technical solution, the arrangement and connection method of the electric slide gate and the manual flap gate are specified. The electric slide gate and the manual flap gate are arranged in series on the main pipe, and the manual flap gate is set on the downstream side of the electric slide gate. This arrangement can ensure that during equipment overhaul or maintenance, the manual flap gate is first closed, and then isolated through the electric slide gate to ensure the safety of operation. In the assembly position, the valve is usually installed on the main pipe that is convenient for operation and maintenance, and it is necessary to ensure that the valve operation will not interfere with the surrounding pipes and equipment.

[0055] An overhaul isolation section is formed between the electric slide gate and the manual flap gate, and an automatic pressure relief valve is set in the overhaul isolation section. When the manual flap gate is closed, the pressure relief valve opens within 5 s to release the residual pressure, and the pressure release rate ≤ 0.3 MPa / s. The length of the overhaul isolation section can be determined according to actual needs, generally in the range of 0.5 - 1.5 m, to ensure there is enough space for overhaul operations and installation of the pressure relief valve. The automatic pressure relief valve can be a spring-loaded safety valve or an electric pressure relief valve, which can automatically sense the pressure change and perform the pressure relief operation. The installation position of the pressure relief valve should be at the end of the overhaul isolation section, close to the manual flap gate side, so as to release the residual pressure in time after the manual flap gate is closed and ensure the safety of maintenance personnel.

[0056] During the operation process, when maintenance or repair of the purging air system is required, first close the manual flap gate to cut off the supply of purging air. At this time, the electric slide gate remains closed, forming a maintenance isolation section. Due to the possible residual pressure in the primary hot air system, the automatic pressure relief valve will automatically open within 5 s to release the residual pressure, and the pressure release rate is controlled at ≤0.3 MPa / s to avoid damage to equipment and personnel caused by rapid pressure relief. After the pressure relief is completed, maintenance personnel can safely enter the maintenance isolation section to perform operations such as equipment inspection, repair, or replacement. During normal operation, both the manual flap gate and the electric slide gate are in the open state, and the purging air is supplied normally to ensure continuous cleaning of the ash accumulation at the bottom of the air box.

[0057] The opening time of the pressure relief valve and the pressure release rate are key parameters to ensure maintenance safety. The opening time of the pressure relief valve is set to 5 s, and this time selection is based on the reaction time of the human body to pressure changes and the safety requirements of the equipment. In practical applications, this opening time can be achieved by adjusting the spring pressure of the pressure relief valve or the parameters of the electric actuator. The setting of the pressure release rate ≤0.3 MPa / s is to avoid impact damage to equipment and personnel caused by rapid pressure relief, and at the same time ensure that the pressure can be released in time to ensure the safety of maintenance personnel.

[0058] In this technical solution, the series arrangement of the electric slide gate and the manual flap gate, and the manual flap gate is arranged downstream of the electric slide gate, forming a reasonable valve operation sequence and safety protection mechanism. When the equipment is shut down or under repair, the manual flap gate can be closed first, and then isolated by the electric slide gate to ensure the safety of the operator. The setting of the maintenance isolation section and the installation of the automatic pressure relief valve further improve the safety of the system. When the manual flap gate is closed, the pressure relief valve can quickly open within 5 seconds and release the residual pressure at a pressure release rate of ≤0.3 MPa / s, preventing damage to equipment or personnel caused by excessive pressure in the pipeline, ensuring the safety and reliability of the purging air system during maintenance, reducing the operation risk, and meeting the safety specifications and requirements of the industrial site.

[0059] In another technical solution, for the purging air system at the bottom of the air box of a power station boiler, an ash accumulation thickness sensor is arranged at the bottom of the air box to continuously monitor the ash accumulation thickness data and transmit it to the boiler control system; The data of the ash accumulation thickness sensor needs to be detected continuously for 3 times exceeding the threshold value (or a single detection exceeding the threshold value and lasting for 5 min) to trigger the air volume adjustment: When the ash accumulation thickness is less than the first preset value (10 mm), the boiler control system starts the electric actuator to control the opening degree of the electric slide gate to decrease, so that the purging air flow rate is reduced to 20 - 30% (0.12 - 2.1 t / h) of the total mass flow rate; When the ash accumulation thickness is not less than the first preset value and less than the second preset value (20 mm), the boiler control system starts the electric actuator to control the increase of the opening degree of the electric slide gate, so that the purging air flow rate is 30 - 60% of the total mass flow rate (corresponding to 2.1 - 4.2 t / h); When the ash accumulation thickness is not less than the second preset value, the boiler control system starts the electric actuator to adjust the opening degree of the electric slide gate to the maximum, so that the purging air flow rate reaches 60 - 100% of the total mass flow rate (corresponding to 4.2 - 7 t / h); The air volume adjustment response time ≤ 15 s.

[0060] In this technical solution, an ash accumulation thickness sensor is provided at the bottom of the air box to continuously monitor the ash accumulation thickness data and transmit it to the boiler control system. The ash accumulation thickness sensor can be an ultrasonic sensor or a capacitive sensor. Both of these sensors have mature products on the market and can adapt to the boiler air box environment with high temperature and high dust. The ultrasonic sensor measures the ash accumulation thickness by emitting and receiving ultrasonic waves, and has the characteristics of non-contact measurement and high accuracy; the capacitive sensor measures the thickness by using the change of the dielectric constant of the ash, and has the advantages of simple structure and low cost. The installation position of the sensor should be at a representative position at the bottom of the air box, which can accurately reflect the overall situation of the ash accumulation. Generally, the central area and the front and rear wall positions at the bottom of the air box can be selected.

[0061] In this technical solution, it is stipulated that the data of the ash accumulation thickness sensor needs to be detected more than the threshold value continuously for 3 times to trigger the air volume adjustment. This logical setting is to avoid misoperation caused by accidental errors or interference of the sensor and improve the stability and reliability of the system. When the ash accumulation thickness is less than the first preset value (10 mm), the boiler control system starts the electric actuator to control the decrease of the opening degree of the electric slide gate, so that the purging air flow rate is reduced to 20 - 30% of the total mass flow rate; when the ash accumulation thickness is not less than the first preset value and less than the second preset value (20 mm), the control system starts the electric actuator to control the increase of the opening degree of the electric slide gate, so that the purging air flow rate is 30 - 60% of the total mass flow rate; when the ash accumulation thickness is not less than the second preset value, the control system starts the electric actuator to adjust the opening degree of the electric slide gate to the maximum, so that the purging air flow rate reaches 60 - 100% of the total mass flow rate. The air volume adjustment response time ≤ 15 s, and this time setting can respond to the ash accumulation change in time to ensure the timeliness and effectiveness of the purging operation.

[0062] The electric actuator is the key equipment to realize the opening degree adjustment of the electric slide gate. There are various models of electric actuators commonly used in the market. For example, a certain brand model of the actuator has the characteristics of high adjustment accuracy, fast response speed, large output torque, etc., and can meet the adjustment requirements of the electric slide gate under different working conditions. In terms of the assembly position, the electric actuator is installed on the valve stem of the electric slide gate and realizes the precise control of the opening degree of the slide gate through mechanical connection.

[0063] During the operation process, the ash accumulation thickness sensor monitors the ash accumulation thickness at the bottom of the air box in real time and transmits the data to the boiler control system. The control system makes judgments and processes according to the received ash accumulation thickness data according to the preset logic. When the ash accumulation thickness is less than 10 mm, the control system believes that the ash accumulation is less, and starts the electric actuator to reduce the opening of the electric slide gate, so that the purge air flow rate is reduced to 20 - 30% of the total mass flow rate to avoid unnecessary energy waste; when the ash accumulation thickness is between 10 - 20 mm, the control system believes that the ash accumulation is at a medium level, and starts the electric actuator to increase the opening of the electric slide gate, so that the purge air flow rate is between 30 - 60% of the total mass flow rate to ensure the purge effect; when the ash accumulation thickness reaches or exceeds 20 mm, the control system believes that the ash accumulation is relatively serious, and immediately starts the electric actuator to adjust the opening of the electric slide gate to the maximum, so that the purge air flow rate reaches 60 - 100% of the total mass flow rate to achieve strong purging and quickly clean the ash accumulation. During the whole process, the air volume adjustment response time is controlled within ≤15 s to ensure that the purge operation can timely adapt to the change of ash accumulation.

[0064] The threshold setting of the ash accumulation thickness sensor is the key to realizing automatic adjustment. The selection of the first preset value (10 mm) and the second preset value (20 mm) is based on the empirical data and actual test results of the influence of the ash accumulation at the bottom of the air box on the boiler operation. When the ash accumulation thickness is less than 10 mm, the influence on the air distribution and operation of the boiler is small, and the purge air volume can be appropriately reduced; when the ash accumulation thickness reaches 20 mm, it has a relatively obvious influence on the boiler operation, and it is necessary to increase the purge air volume for cleaning. In practical applications, these thresholds can be further optimized through on-site tests and historical data statistics.

[0065] In this technical solution, the ash accumulation thickness sensor installed at the bottom of the air box can monitor the ash accumulation situation in real time and transmit the data to the boiler control system, realizing the online monitoring of the ash accumulation state inside the air box. By setting the threshold of the ash accumulation thickness and following the logic that the air volume adjustment is triggered only when the threshold is exceeded in three consecutive detections, false operations caused by occasional errors or interferences of the sensor are effectively avoided, improving the stability and reliability of the system. The opening degree of the electric slide gate is automatically adjusted according to different ash accumulation thicknesses, and the purge air flow is precisely controlled to match the actual ash accumulation degree, ensuring both the purge effect and energy conservation. When the ash accumulation thickness is small, the purge air flow is reduced to 20 - 30% of the total mass flow, avoiding unnecessary air volume consumption; when the ash accumulation thickness is in the intermediate range, the purge air flow is adjusted to 30 - 60% of the total mass flow to ensure the purge effect; when the ash accumulation thickness reaches a large value, the opening degree of the electric slide gate is adjusted to the maximum, making the purge air flow reach 60 - 100% of the total mass flow to achieve strong purging and quickly clean the ash. The response time of the air volume adjustment is ≤ 15 seconds, which can respond to ash accumulation changes in a timely manner, ensuring the timeliness and effectiveness of the purging operation, improving the intelligent level and automation degree of boiler operation, reducing manual intervention, and enhancing the overall operation efficiency.

[0066] In another technical solution, for the ash purge air system at the bottom of the air box of a power station boiler, a pressure sensor is installed on the upstream side of the maintenance isolation section between the electric slide gate and the manual flap gate. Its detection surface is perpendicular to the air flow direction. The pressure sensor is used to detect the purge air pressure data provided by the primary hot air system in real time and transmit it to the boiler control system; When the detected pressure value P real is higher than the preset upper pressure threshold P high the electric actuator controls the opening degree of the electric slide gate to decrease at a rate of 2 - 5% per minute until the purge air flow drops to 70 - 80% of the current set value; when the detected pressure value P real is lower than the preset lower pressure threshold P low the electric actuator triggers the full - open mode, and the electric slide gate is opened to the maximum opening degree within 30 s. At the same time, the boiler control system generates a three - level alarm signal; P high = P BMCR ×115%; P low = P BMCR ×85%; Among them, P BMCRIt is the designed purge air pressure value under BMCR condition; P high It is the preset upper pressure limit threshold; P low It is the preset lower pressure limit threshold; The detection time interval is 30s.

[0067] In this technical solution, it involves setting a pressure sensor on the upstream side of the maintenance isolation section between the electric slide gate and the manual flap gate. Its detection surface is perpendicular to the air flow direction. The pressure sensor is used to detect the purge air pressure data provided by the primary hot air system in real time and transmit it to the boiler control system. The pressure sensor can be a piezoresistive or capacitive sensor. Both of these sensors have mature products in the market and can adapt to the high-temperature and high-pressure boiler environment. The piezoresistive sensor utilizes the piezoresistive effect of semiconductor materials and has the characteristics of high precision and high stability; the capacitive sensor detects pressure by measuring the change in capacitance and has the advantages of simple structure and strong anti-interference ability. The installation position of the sensor should be on the main pipeline on the upstream side of the maintenance isolation section, and it is necessary to ensure that the detection surface is perpendicular to the air flow direction to accurately measure the purge air pressure.

[0068] In this technical solution, it is stipulated that when the detected pressure value P real is higher than the preset upper pressure limit threshold P high or lower than the preset lower pressure limit threshold P low , the electric actuator controls the opening degree of the electric slide gate for corresponding adjustment. The preset upper pressure limit threshold P high = P BMCR ×115%, the preset lower pressure limit threshold P low = P BMCR ×85%, where P BMCR is the designed purge air pressure value under BMCR condition. This logical setting can automatically adjust the opening degree of the electric slide gate according to the real-time change of the purge air pressure, ensure the stable supply of the purge air volume, and avoid unstable purge effect or equipment damage caused by pressure fluctuation.

[0069] Taking into account the actual requirements of boiler operation, P BMCR The calculation formula of is: where P 安全 = ( P 出口 + P 总阻 ) * 1.15; The total resistance of the purge air systemP 总阻 It covers the frictional resistance along the way and the local resistance, and can be calculated by the following formula Frictional resistance coefficient along the way λ , which can be taken as 0.02 for steel pipes; Pipeline length L , assuming the main pipeline length is 30m; Inner diameter of the pipeline D , the inner diameter of the main pipeline is taken as 0.3m; Local resistance coefficient ∑ ξ , including the electric slide gate ( ξ =2.0), manual flap gate ( ξ =1.5) and elbows (each elbow ξ =0.3, assuming there are 4 elbows in total), after calculation P 总阻 is 4.5kPa.

[0070] The air flow velocity at the outlet of the purging hole should be in the range of 60 - 100m / s. According to Bernoulli's equation, the corresponding dynamic pressure can be calculated: ρ represents the density of the primary hot air at 300℃, which is approximately 0.6kg / m³; v is the air flow velocity, taking the middle value of 80m / s. After calculation like this P 出口 is 1.92kPa; After the above-mentioned hypothetical calculations, taking the middle value of 7kPa, P 安全 is 7.48kPa, and finally it is the designed purging air pressure value under the BMCR condition P BMCR is 14.48kPa.

[0071] Based on the results of comprehensive calculation and verification, P BMCR it should be rounded to the commonly used values in engineering, generally between 12 - 15kPa. For example, the P BMCR value of a certain 660MW ultra-supercritical boiler is taken as 14kPa, and it is necessary to ensure that under the BMCR condition, the temperature of the purging air ≥ 300℃.

[0072] During the working process, the pressure sensor monitors the purging air pressure provided by the primary hot air system in real time and transmits the data to the boiler control system. The control system compares the received pressure value with the preset threshold and makes judgments and processes according to the preset logic. When the detected pressure value P realHigher than the preset upper pressure threshold P high When this occurs, the control system deems that the purging air pressure is too high and activates the electric actuator to control the opening degree of the electric slide gate to decrease at a rate of 2 - 5% per minute until the purging air flow rate drops to 70 - 80% of the current set value; when the detected pressure value P real is lower than the preset lower pressure threshold P low When this occurs, the control system deems that the purging air pressure is too low, triggers the fully open mode of the electric slide gate, and the electric slide gate opens to the maximum opening degree within 30 seconds. At the same time, the boiler control system generates a level - three alarm signal to remind the operator to pay attention. During the whole process, the cooperation between the pressure sensor and the electric actuator can ensure the stability of the purging air pressure and guarantee the reliability of the purging effect.

[0073] The preset upper pressure threshold P high and the preset lower pressure threshold P low are set based on the pressure detection value under the BMCR condition. P BMCR is the average value of 10 consecutive pressure detection values under the BMCR condition. This setting can reflect the normal pressure level of the boiler during full - load operation. P high =P BMCR ×115%, P low =P BMCR ×85%. This setting range can adapt to the pressure fluctuations during the boiler operation, ensure that the purging air system can work stably within the normal pressure range, and at the same time adjust in time when the pressure is abnormal.

[0074] In this technical solution, a pressure sensor is set on the upstream side of the maintenance isolation section between the electric slide gate and the manual flap gate to detect the purging air pressure data provided by the primary hot air system in real - time and transmit it to the boiler control system, providing a basis for the precise control of the purging air volume. By setting the preset upper pressure threshold and the preset lower pressure threshold, and comparing the actual detected pressure value with the threshold, the opening degree of the electric slide gate is automatically adjusted, realizing the closed - loop control of the purging air pressure. When the detected pressure value is higher than the preset upper pressure threshold P high When this occurs, the opening degree of the electric slide gate is decreased at a rate of 2 - 5% per minute, so that the purging air flow rate drops to 70 - 80% of the current set value, avoiding excessive purging air volume caused by too high wind pressure, resulting in energy waste or impact on equipment; when the detected pressure value is lower than the preset lower pressure threshold P lowWhen triggered, it activates the full - open mode of the electric plug - door, opens it to the maximum opening within 30 seconds, and generates a three - level alarm signal to alert the operator. This ensures an adequate supply of purging air volume, preventing the purging effect from being affected by insufficient air pressure. This pressure control mechanism can automatically adjust the purging air volume according to the changes in the operating conditions of the boiler, ensuring the stable operation of the purging system, improving the adaptability and reliability of the system, further optimizing the operating performance of the boiler, and reducing the operating cost.

[0075] In another technical solution, for the ash - purging air system at the bottom of the wind box of a power - station boiler, from the outside to the inside of the purging pipeline, it successively includes a high - temperature - resistant and oxidation - resistant layer, a nanofiber - reinforced buffer layer, and an ultra - smooth and wear - resistant inner layer; micron - scale groove arrays are distributed on the surface of the inner layer, the groove depth is 0.1 - 0.3 mm, the width is 0.2 - 0.5 mm, and they are arranged in a spiral shape along the air - flow direction.

[0076] This technical solution involves the multi - layer structure design of the purging pipeline, including a high - temperature - resistant and oxidation - resistant layer, a nanofiber - reinforced buffer layer, and an ultra - smooth and wear - resistant inner layer. This multi - layer structure can significantly improve the service life and performance of the purging pipeline. The high - temperature - resistant and oxidation - resistant layer can be made of high - temperature - resistant materials such as inconel alloy and Hastelloy alloy. These materials have excellent oxidation and corrosion resistance and can be used for a long time in high - temperature environments without damage. The nanofiber - reinforced buffer layer can be made of materials such as carbon nanotube fiber and ceramic nanofiber. These materials have high strength, high modulus, and good toughness, and can effectively absorb the vibration energy generated by the purging air in the pipeline, reducing the mechanical fatigue and wear of the pipeline. The ultra - smooth and wear - resistant inner layer can be made of materials such as ceramic coating and Teflon coating. These materials have a smooth surface, a small friction coefficient, can reduce the flow resistance of the purging air in the pipeline, improve the air - conveying efficiency, and at the same time have excellent wear - resistant performance and can withstand the long - term erosion of high - speed air flow without being easily damaged.

[0077] In this technical solution, it is also specified that micron - scale groove arrays are distributed on the surface of the inner layer, the groove depth is 0.1 - 0.3 mm, the width is 0.2 - 0.5 mm, and they are arranged in a spiral shape along the air - flow direction. This groove design can guide the air flow to form an orderly swirl, enhancing the disturbance effect of the purging air and improving the cleaning ability of the ash at the bottom of the wind box. The grooves can be processed by precision processing techniques such as laser processing and chemical etching to ensure the dimensional accuracy and shape accuracy of the grooves. In the installation position, the purging pipeline is installed above the truss at the bottom of the wind box, fixed by brackets, and maintains a predetermined distance from the bottom plate of the wind box to ensure that the purging air can effectively cover the bottom of the wind box.

[0078] In this technical solution, a multi-layer protection structure is formed by successively arranging a high-temperature resistant and oxidation resistant layer, a nanofiber reinforced buffer layer, and an ultra-smooth wear-resistant inner layer from the outside to the inside of the purging pipeline, significantly improving the service life and performance of the purging pipeline. The high-temperature resistant and oxidation resistant layer can effectively resist oxidation corrosion in high-temperature environments and protect the pipeline matrix from damage; the nanofiber reinforced buffer layer has good buffering and shock absorption performance, can absorb the vibration energy generated by the purging air in the pipeline, and reduce the mechanical fatigue and wear of the pipeline; the ultra-smooth wear-resistant inner layer has a smooth surface and a small friction coefficient, can reduce the flow resistance of the purging air in the pipeline, improve the conveying efficiency of the air, and at the same time has excellent wear resistance and can withstand the long-term erosion of high-speed air flow without being easily damaged. The micron-scale groove array distributed on the inner layer surface, with the grooves arranged in a spiral shape along the air flow direction, can guide the air flow to form an orderly swirling flow, enhance the disturbance effect of the purging air, improve the cleaning ability of the dust accumulation at the bottom of the air box, and at the same time, the depth and width of the grooves are reasonably designed and will not cause excessive resistance to the air flow, ensuring the flow rate and pressure of the purging air, further improving the purging effect and the service life of the pipeline, and reducing the maintenance and replacement costs.

[0079] In another technical solution, for the dust accumulation purging air system at the bottom of the boiler air box in a power station, a dynamic pressure compensator is provided in the multi-stage branch pipeline unit, which includes an energy storage cavity and a piezoelectric ceramic driven throttle valve integrated at the branch pipe interface; when it is detected that the pressure fluctuation of the branch pipe exceeds ±5%, the piezoelectric ceramic driven throttle valve responds within 10 ms, and releases / absorbs the air flow pulsation energy through the energy storage cavity to maintain the pressure stability of the branch pipeline.

[0080] This technical solution involves a dynamic pressure compensator provided in the multi-stage branch pipeline unit, which includes an energy storage cavity and a piezoelectric ceramic driven throttle valve integrated at the branch pipe interface. The main function of the dynamic pressure compensator is to cope with the pressure fluctuation of the branch pipe and maintain the pressure stability of the branch pipeline. The energy storage cavity can be made of high-strength alloy steel and has a sufficient volume to store and release the air flow pulsation energy. Generally, the volume ranges from 0.1 to 0.5 m³, which can meet the common requirements for compensating the pressure fluctuation of the branch pipeline. The piezoelectric ceramic driven throttle valve can select a mature piezoelectric ceramic actuator on the market, which has a fast response speed and high control precision and can respond to the pressure fluctuation within 10 milliseconds.

[0081] The dynamic pressure compensator monitors the pressure fluctuations in the branch pipes in real time through a pressure sensor. When the detected pressure fluctuation exceeds ±5%, the piezoelectric ceramic drives the throttle valve to act quickly, releasing or absorbing the pulsating energy of the air flow through the energy storage chamber, thereby maintaining the pressure stability of the branch pipes. The pressure sensor can be a piezoresistive or capacitive sensor, installed at the interface of the branch pipes, close to the dynamic pressure compensator, so as to detect the pressure changes in a timely and accurate manner. The dynamic pressure compensator uses high-temperature-resistant piezoelectric ceramics (such as PZT-5H), which has been verified by a 1000h durability test at 350°C.

[0082] The dynamic pressure compensator provided in the multi-stage branch pipe unit of the present invention can effectively address the problem of pressure fluctuations in the branch pipes. When the pressure fluctuation in the branch pipes is detected to exceed ±5%, the piezoelectric ceramic drives the throttle valve to respond quickly within 10 milliseconds, releasing or absorbing the pulsating energy of the air flow through the energy storage chamber, quickly stabilizing the pressure of the branch pipes, and ensuring that the purging air can be evenly and stably delivered to each area of the air box. This dynamic pressure compensation mechanism can effectively reduce the uneven purging air volume caused by pipeline pressure fluctuations, improve the stability of the purging effect, avoid affecting the ash cleaning effect due to excessive or insufficient local air volume, ensure the uniformity and reliability of the entire air box bottom purging system, further optimize the operating performance of the boiler, and reduce the equipment loss and maintenance cost caused by pressure fluctuations.

[0083] In another technical solution, for the ash cleaning purging air system at the bottom of the power station boiler air box, the purging pipeline is made of a high-temperature-resistant and wear-resistant alloy steel pipe with a coating thickness of 0.3 - 0.5 mm; the purging holes are processed by a laser precision drilling process, and the orifice is designed with a 30° chamfer.

[0084] This technical solution involves a purging pipeline made of a high-temperature-resistant and wear-resistant alloy steel pipe with a coating thickness of 0.3 - 0.5 mm. This material selection can adapt to the working environment of high-temperature and high-speed air flow scouring inside the boiler air box, ensuring that the purging pipeline is not easily deformed, worn, or damaged during long-term operation. There are various models of common high-temperature-resistant and wear-resistant alloy steel pipes on the market, such as alloy steel A335-P91, A335-P92, etc. These materials have high strength, good toughness, and excellent high-temperature resistance. The coating can be a ceramic coating, a tungsten carbide coating, etc. These coating materials can further improve the wear resistance and corrosion resistance of the pipeline and extend the service life of the pipeline.

[0085] In this technical solution, it is also specified that the purging holes are processed by laser precision drilling technology, and the orifice is designed with a 30° chamfer. The laser drilling technology can ensure the dimensional accuracy and shape accuracy of the purging holes, meet the design requirements of the purging hole diameter of 8 - 12 mm, and ensure the uniform distribution and precise injection of the purging air. The 30° chamfer design can effectively reduce the wind speed loss at the outlet of the purging hole, increase the kinetic energy of the purging air, and enhance the cleaning effect on the ash accumulation at the bottom of the air box. At the same time, the chamfer design can also reduce the wear at the outlet of the purging hole and improve the service life of the purging hole.

[0086] In this technical solution, the purging pipeline is made of high-temperature and wear-resistant alloy steel pipe, which has excellent high-temperature strength and wear-resistant performance, can adapt to the working environment of high-temperature and high-speed gas flow scouring inside the boiler air box, ensure that the purging pipeline is not easily deformed, worn or damaged during long-term operation, and extends the service life of the pipeline. The special coating with a thickness of 0.3 - 0.5 mm further improves the high-temperature and wear-resistant performance of the pipeline and enhances the protection ability of the pipeline. The purging holes are processed by laser precision drilling technology, and the orifice is designed with a 30° chamfer, which can ensure the dimensional accuracy and shape accuracy of the purging holes, make the purging air spray out at the best angle and speed, and improve the purging effect. The laser drilling technology can also achieve precise processing of micro apertures, meet the design requirements of the purging hole diameter of 8 - 12 mm, ensure the uniform distribution and precise injection of the purging air, further improve the performance and reliability of the purging system, reduce the maintenance and replacement frequency, and save the operation cost.

[0087] In another technical solution, for the purging air system for the ash accumulation at the bottom of the power station boiler air box, an electric ball valve throttling mechanism is provided in the purging hole, and the opening degree is directly controlled by the signal of the pressure sensor; When it is detected that the air flow velocity at the outlet of the purging hole is lower than 60 m / s, the opening degree of the ball valve increases; when it is higher than 100 m / s, the opening degree decreases.

[0088] The electric ball valve throttling mechanism integrates a micro servo motor and a closed-loop feedback control system. The closed-loop feedback control system dynamically adjusts the opening degree of the ball valve by using the proportional-integral-derivative (PID) algorithm based on the air flow velocity data detected by the pressure sensor in real time at the outlet of the purging hole, so that the air flow velocity is stabilized in the range of 70 - 100 m / s; The response time of the electric ball valve ≤ 0.5 s, and the opening degree adjustment accuracy is ±1.5%; The pressure sensor is embedded in the inner wall on the downstream side of the purging hole, its detection surface is perpendicular to the air flow direction, and a control signal is generated after removing the abnormal values from the continuous 10 sampling data through the redundant verification module; When it is detected that the air flow velocity deviates from the set range for 3 seconds continuously, the closed-loop feedback control system triggers the self-calibration mode, links the adjacent purge hole ball valve to synchronously adjust the opening, and generates a dynamic compensation air volume instruction to the total air volume adjustment module of the boiler control system.

[0089] The technical solution involves an electric ball valve throttling mechanism in the purge hole, which integrates a micro servo motor and a closed-loop feedback control system. The electric ball valve can use the common electric V-type ball valve on the market, which has the characteristics of high adjustment accuracy, fast response speed, good sealing performance, etc., and can meet the requirements of the purge system for precise control of wind speed. The micro servo motor can use an AC servo motor or a DC servo motor, and its power is generally in the range of 50-200W, which can provide sufficient torque to drive the ball valve to quickly and accurately adjust the opening. The closed-loop feedback control system uses a proportional-integral-differential (PID) algorithm to dynamically adjust the ball valve opening based on the airflow velocity data at the outlet of the purge hole detected in real time by the pressure sensor, so that the airflow velocity is stabilized in the range of 70-100m / s. The pressure sensor can use a piezoresistive or capacitive sensor, which is installed near the outlet of the purge hole and can monitor the changes in airflow velocity in real time.

[0090] This technical solution stipulates that when the air flow velocity at the outlet of the purge hole is detected to be lower than 60m / s, the ball valve opening increases; when it is higher than 100m / s, the opening decreases. This logic setting is to ensure that the flow rate of the purge air can effectively lift the accumulated dust without causing excessive scouring to the bottom plate of the bellows. 60m / s is the minimum flow rate at which the purge air can effectively carry the accumulated dust. When the flow rate is lower than this value, the accumulated dust may not be fully lifted; 100m / s is the maximum flow rate to avoid damage to the bottom plate of the bellows. When the flow rate exceeds this value, it may accelerate the wear of the bottom plate.

[0091] The pressure sensor is embedded in the inner wall of the downstream side of the purge hole, with its detection surface perpendicular to the airflow direction. The redundant check module removes abnormal values ​​from 10 consecutive sampling data to generate a control signal. This installation method and data processing method can ensure that the pressure sensor accurately and stably detects the airflow velocity, while effectively avoiding misoperation caused by accidental factors.

[0092] When it is detected that the airflow speed deviates from the set range for 3 seconds, the closed-loop feedback control system triggers the self-calibration mode, links the adjacent purge hole ball valve to synchronously adjust the opening, and generates a dynamic compensation air volume command to the total air volume adjustment module of the boiler control system. This self-calibration mechanism can respond to abnormal changes in airflow speed in a timely manner to ensure the stable operation of the purge system. At the same time, by linking the adjustment of the adjacent ball valve and generating dynamic compensation air volume commands, the purge effect and boiler operation performance are further optimized.

[0093] The electric ball valve throttling mechanism installed in the purging holes of this technical solution directly controls the opening degree through the signal of the pressure sensor, and can automatically adjust the opening degree of the ball valve according to the real-time change of the air flow velocity at the outlet of the purging hole. When it is detected that the air flow velocity at the outlet of the purging hole is lower than 60 m / s, the opening degree of the ball valve automatically increases to increase the air volume and improve the purging intensity; when the air flow velocity is higher than 100 m / s, the opening degree of the ball valve automatically decreases to reduce the air volume and avoid energy waste and equipment damage caused by excessive purging. This automatic adjustment mechanism can ensure that the flow velocity of the purging air is always maintained within the range of effectively cleaning the ash accumulation, improving the intelligent level and automation degree of the system, reducing manual intervention, further optimizing the operation efficiency and economy of the boiler, and extending the service life of the purging pipeline and the wind box bottom plate. In addition, the self-calibration mode and linkage adjustment function of the closed-loop feedback control system can timely respond to the abnormal change of the air flow velocity, ensure the stable operation of the purging system, and further improve the purging effect and the operation performance of the boiler.

[0094] In another technical solution, for the ash accumulation purging air system at the bottom of the wind box of a power station boiler, the purging pipeline is fixed above the truss at the bottom of the wind box through U-bolts, and the distance between the bottom surface of the purging pipeline and the wind box bottom plate is 400 - 600 mm; a partition is arranged inside the wind box to divide the purging air flow into multiple areas, and branch pipelines are added in the area above the partition to form a stratified purging pipeline, and the stratified purging pipeline is connected in parallel with the main purging pipeline.

[0095] This technical solution involves fixing the purging pipeline above the truss at the bottom of the wind box through U-bolts, and the distance between the bottom surface of the purging pipeline and the wind box bottom plate is 400 - 600 mm. This fixing method is simple and reliable, convenient for installation and disassembly, and can adapt to the structural characteristics and space limitations inside the wind box at the same time. The material of the U-bolt can be selected from carbon steel or stainless steel. Carbon steel has a lower cost and is suitable for general working conditions; stainless steel has better corrosion resistance and strength and is suitable for high-temperature or corrosive environments. In the assembly position, the U-bolt is installed at the designated position of the truss at the bottom of the wind box to ensure that the purging pipeline is firmly fixed at a height of 400 - 600 mm from the wind box bottom plate, which not only ensures that the purging air can effectively cover the bottom of the wind box, but also avoids the purging damage to the wind box bottom plate caused by too close distance or the poor purging effect caused by too far distance.

[0096] This technical solution also stipulates that a partition is set inside the bellows to divide the purge airflow into multiple areas, and a branch pipeline is added in the area above the partition to form a layered purge pipeline, which is connected in parallel with the main purge pipeline. The partition can be made of ordinary carbon steel plate, which has the advantages of high strength, low cost, and easy processing. It can reasonably divide the internal space of the bellows to form multiple independent purge areas, thereby improving the uniformity and thoroughness of the purge. The branch pipeline can be made of the same material as the main purge pipeline, such as a carbon steel pipe, and connected to the main purge pipeline by flanges or welding to form a parallel layered purge system. This design can distribute the purge air more evenly, ensure that the dust accumulated in every corner of the bellows can be effectively cleaned, and further optimize the purge effect.

[0097] During operation, the purge air is transported to the bottom of the wind box through the main purge pipe, and at the same time, different areas inside the wind box are purged in layers through the layered purge pipe. The purge pipe fixed with U-bolts is at a height of 400-600mm from the bottom plate of the wind box, ensuring that the purge air can hit the bottom of the wind box at a suitable angle and speed, lift up the accumulated ash and enter the furnace with the secondary air. The partition inside the wind box divides the purge airflow into multiple areas, avoiding mutual interference between airflows and improving the uniformity of purge. The layered purge pipeline is connected in parallel with the main purge pipeline, and can independently adjust the purge air volume of each layer as needed, so as to achieve effective cleaning of ash accumulation in different areas and improve the flexibility and adaptability of the purge system.

[0098] The distance between the bottom of the purge pipe and the bottom plate of the bellows is set to 400-600mm. The selection of this range is based on the coverage of the purge air and the structural strength of the bottom plate of the bellows. A closer distance can provide a stronger purge force, but it may cause scouring and wear on the bottom plate of the bellows; a farther distance can expand the coverage of the purge air, but it may reduce the purge effect. In practical applications, the optimal spacing value can be determined through field tests and numerical simulations. In order to verify the impact of the design of the stratified purge pipeline on the purge effect, a functional test can be carried out. During the test, the dust accumulation at the bottom of the bellows before and after the use of the stratified purge pipeline is compared, the distribution of the dust accumulation and the cleaning effect are recorded, and the effectiveness of the stratified purge pipeline is evaluated.

[0099] The purging pipeline of this technical solution is fixed above the bottom truss of the air box through U-bolts. The distance between the bottom surface of the purging pipeline and the bottom plate of the air box is 400 - 600 mm. This fixing method is simple and reliable, facilitating installation and disassembly. At the same time, it can adapt to the structural characteristics and space limitations inside the air box, ensuring the effective coverage and purging effect of the purging air. The partition plate set inside the air box divides the purging air flow into multiple areas. A branch pipeline is added in the area above the partition plate to form a stratified purging pipeline, which is connected in parallel with the main purging pipeline, realizing stratified and zoned purging of the internal space of the air box. This design can distribute the purging air more evenly, ensuring that the ash accumulation in all corners of the air box can be effectively cleaned, improving the comprehensiveness and thoroughness of purging, further optimizing the purging effect, reducing the impact of ash accumulation on boiler operation, improving the stability and economy of boiler operation. At the same time, the parallel design of the stratified purging pipeline also increases the redundancy and reliability of the system, facilitating maintenance and repair when problems occur in some pipelines.

[0100] Application example of the present invention: A certain power plant's 660MW ultra-supercritical boiler adopts a left coal bunker layout, with three layers of burners and one layer of OFA nozzles arranged in the front and back of the furnace, and a burner annular air box and an OFA annular air box are respectively configured. During the operation of the Howden three-chamber rotary air preheater, the secondary air carries high-temperature ash. After long-term accumulation, the ash thickness in the front and back wall areas of the OFA air box and the burner air box reaches 35 mm, causing problems such as uneven distribution of secondary air, a 0.8% decrease in combustion efficiency, leakage of air through the welded joints of the air box (requiring 2 annual overhauls), and a ±15% fluctuation in nitrogen oxide emissions.

[0101] Design the purging system according to the system provided by the present invention Symmetrically draw out two Φ273 main pipes from the downward part of the hot primary air at the rear of the furnace, configure Z-type electric slide gates (DN273) and cast steel manual flap gates, and set an automatic pressure relief valve in the maintenance isolation section with a response time of 5 seconds and a pressure release rate of 0.25 MPa / s to ensure maintenance safety. The air intake parameters are: the air pressure is 13.14 kPa and the temperature is 333 °C under the BMCR condition, and the mass flow rate of the primary air is 384 t / h. The purging holes are precision machined by laser, with a diameter of 10 mm and a 30° chamfer design at the hole opening. The pitch between adjacent holes is 500 mm (the width of the air box W = 625 mm, and the pitch L = 0.8W). The purging pipe has a specification of Φ89, and a total of 500 purging holes are opened, with an outlet air flow velocity of 80 m / s, and the total system flow rate is controlled at 4.2 t / h (under the BMCR condition). Linkage control of ash thickness: An ultrasonic ash accumulation sensor (accuracy ±1 mm) is installed at the bottom of the air box. When the ash thickness exceeds 10 mm continuously for 3 times, the purging air volume is reduced to 30% (1.26 t / h); when it exceeds 20 mm, the full-open mode (4.2 t / h) is triggered. Pressure closed-loop control: A pressure sensor (accuracy ±0.5%FS) is set upstream of the maintenance section. The preset upper pressure limit is 15.11 kPa (Phigh = 13.14 kPa × 115%), and the lower limit is 11.17 kPa (Plow = 13.14 kPa × 85%). The opening adjustment rate of the electric slide gate is 3% / min. The purge pipeline adopts a composite coating structure: the outer layer is Inconel625 alloy (0.5 mm), a carbon nanotube-reinforced buffer layer, and a WC-Co ultra-smooth inner layer (0.3 mm). The inner surface is machined with spiral micro-grooves (depth 0.2 mm), and the anti-scouring ability is increased by 1.3 times. The branch pipe is integrated with a dynamic pressure compensator. The energy storage cavity is 0.3 m³, the response time of the piezoelectric ceramic valve is 10 ms, and the pressure fluctuation is controlled within ±3%. The purge pipeline is fixed above the bottom truss of the wind box by U-bolts, and the distance between the bottom surface and the bottom plate is 400 mm to ensure effective coverage of the purge air. Two additional layers of branch pipes are added to cover the baffle area to achieve stratified purging and solve the problem of ash accumulation near the baffle. Two Φ273 main pipes are led out from the hot primary air pipeline behind the furnace. After passing through the electric slide gate and the manual flap gate, they are divided into four Φ219 branch pipes, which respectively enter the burner wind box (front / rear) and the OFA wind box (front / rear). The branch pipe is further divided into two Φ159 secondary branch pipes to connect to the distribution header, and finally covers the bottom plate and baffle area of the wind box through Φ89 purge pipes (with 500 Φ10 purge holes). After the hot primary air (333 °C, 13.14 kPa) is gradually decompressed and accelerated, it is ejected through the purge holes at a flow rate of 80 m / s to form a disturbed air film at the bottom of the wind box, making the ash accumulation suspended and carried into the furnace by the secondary air. Ash cleaning effect: The average ash accumulation thickness at the bottom of the wind box is reduced from 35 mm to 4.2 mm, and the ash cleaning efficiency is increased by 88% (data continuously monitored by ultrasonic sensors). Air temperature stability: The fluctuation range of the secondary air temperature is reduced from ±8 °C to ±2 °C, and the improvement rate is 75% (recorded by the DCS system). Energy consumption optimization: The purge air volume is reduced from 6.0 t / h to 4.2 t / h, and the annual power saving reaches 1.45×10^6 kWh (at a power price of 0.5 yuan / kWh, saving 725,000 yuan annually). Equipment reliability: The number of weld cracks at the wind box is reduced from 2 times / year to 0 times / year, and the pipeline life is extended from 18 months to 42 months (data from material durability tests). Combustion and emissions: The combustion efficiency is increased from 92.5% to 93.7% (ASME PTC4 standard thermal efficiency test), and the nitrogen oxide emission concentration is decreased by 7.8% (320 mg / m³ → 295 mg / m³, CEMS on-line monitoring data). Maintenance cost: The annual maintenance cost has been reduced from 1.2 million yuan to 0.55 million yuan, a decrease of 54% (statistics of maintenance costs). In this example, when the flow rate of the purging holes is 80 m / s, the ash suspension rate reaches 95% (laboratory wind tunnel test data). The stratified purging design reduces the ash accumulation in the baffle area by 70% (comparison during furnace shutdown inspection). In this example, the payback period is only 0.96 years (equipment transformation cost of 1.2 million yuan ÷ annual cost savings of 1.375 million yuan). The dynamic pressure compensator reduces the branch pressure fluctuation from ±12% to ±3% (recorded by the pressure sensor). The response time of the purging system is ≤15 s. The flow rate of the purging holes is stable at 70 - 100 m / s. The wear of the wind box bottom plate is <0.1 mm / year, meeting the erosion prevention design. Through the extraction of hot primary air, intelligent control, and material innovation, the present invention realizes the efficient online cleaning of the ash accumulation at the bottom of the wind box. The above results show that the system provided by the present invention solves the problems of low efficiency of traditional manual ash cleaning and high maintenance cost. It eliminates the hidden danger of cracking at the wind box weld, ensuring the safe operation of the unit. It optimizes the combustion efficiency and environmental protection indicators, saving 1.375 million yuan annually, and has significant economic and social benefits. The equipment quantities and processing scales described here are used to simplify the description of the present invention. The applications, modifications, and variations of the present invention are obvious to those skilled in the art.

[0102] Although the embodiments of the present invention have been disclosed as above, they are not limited to only the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated and described examples here.

Claims

1. A ash purge air system for the bottom of a power station boiler wind box, characterized in that: include: The hot primary air intake unit includes two independent purge air main pipes drawn from the hot primary air system of the boiler, each of which is provided with an electric plug-in door and a manual flap door; A multi-stage branch pipe unit, which extends from the purge air main pipe to the left and right sides of the boiler furnace to form a branch pipe system including multiple branch pipes, and the branch pipes extend to the front and rear areas of the wind box; The purge unit at the bottom of the bellows includes a purge pipe arranged inside the bellows, which is fixed above the bottom truss of the bellows through a bracket and maintains a predetermined distance from the bottom plate of the bellows. The bottom surface of the purge pipe has purge holes evenly distributed axially, and the direction of the airflow ejected from the purge holes is toward the bottom plate of the bellows; the purge pipe is connected to the branch pipe through a distribution header.

2. The dust purge air system for the bottom of the power station boiler wind box according to claim 1, characterized in that: The diameter of the purge hole is 8-12 mm, and the pitch between adjacent purge holes is L=0.8W, where W is the width of the bellows; The velocity of the air flow from the purge hole is 60-110m / s, and the total mass flow of the purge air system is controlled within the range of 0.6-7t / h by adjusting the opening of the electric plug-in door; The diameters of the purge air main pipe, branch pipe and purge pipe decrease gradually, and the wind speed in each section of the pipe is 20-30m / s; The working parameters provided by the hot primary air intake unit meet the requirements of wind pressure ≥12kPa and temperature ≥300℃ under BMCR working conditions.

3. The dust purge air system for the bottom of the power station boiler wind box according to claim 1, characterized in that: The electric gate door and the manual flap door are arranged in series on the main pipe, and the manual flap door is arranged on the downstream side of the electric gate door; An inspection and isolation section is formed between the electric plug door and the manual flap door. An automatic pressure relief valve is provided in the inspection and isolation section. When the manual flap door is closed, the pressure relief valve opens within 5 seconds to release the residual pressure, and the pressure release rate is ≤0.3MPa / s.

4. The ash purge air system for the bottom of the power station boiler wind box as claimed in claim 3, characterized in that: An ash thickness sensor is installed at the bottom of the wind box to monitor the ash thickness data in real time and transmit it to the boiler control system; The dust accumulation thickness sensor data needs to exceed the threshold for three consecutive times to trigger the air volume adjustment: When the ash accumulation thickness is less than the first preset value, the boiler control system starts the electric actuator to control the electric plug-in door to reduce the opening, so that the purge air flow rate is reduced to 20-30% of the total mass flow rate; When the ash accumulation thickness is not less than the first preset value and less than the second preset value, the boiler control system starts the electric actuator to control the electric plug-in door to increase the opening, so that the purge air flow rate is 30-60% of the total mass flow rate; When the ash accumulation thickness is not less than a second preset value, the boiler control system starts the electric actuator to adjust the electric plug door opening to the maximum, so that the purge air flow rate reaches 60-100% of the total mass flow rate.

5. The ash purge air system for the bottom of the power station boiler wind box as claimed in claim 4, characterized in that: A pressure sensor is installed on the upstream side of the maintenance isolation section between the electric plug-in door and the manual flap door, and its detection surface is perpendicular to the airflow direction. The pressure sensor is used to detect the purge air pressure data provided by the hot primary air system in real time and transmit it to the boiler control system; When the pressure value is detected P real Higher than the preset upper pressure threshold P high When the pressure is detected, the electric actuator controls the electric plug-in door to decrease at a rate of 2-5% per minute until the purge air flow rate drops to 70-80% of the current set value. P real Below the preset lower pressure threshold P low When the electric actuator triggers the full-open mode, the electric plug-in door opens to the maximum opening within 30 seconds, and the boiler control system generates a three-level alarm signal; P high = P BMCR ×115%； P low = P BMCR ×85%； in, P BMCR Design the purge air pressure value for BMCR working conditions; P high is the preset upper pressure threshold; P low It is the preset lower pressure threshold; the detection time interval is 30s.

6. The dust purge air system for the bottom of the power station boiler wind box as claimed in claim 1, characterized in that: The purge pipe includes a high-temperature resistant and anti-oxidation layer, a nanofiber reinforced buffer layer and an ultra-smooth and wear-resistant inner layer from the outside to the inside; the inner layer surface is distributed with a micron-scale groove array with a groove depth of 0.1-0.3mm and a width of 0.2-0.5mm, which is arranged in a spiral shape along the airflow direction.

7. The dust purge air system for the bottom of the power station boiler wind box according to claim 1, characterized in that: The multi-stage branch pipe unit is provided with a dynamic pressure compensator, which includes an energy storage chamber integrated at the branch pipe interface and a piezoelectric ceramic driven throttle valve; when it is detected that the branch pipe pressure fluctuation exceeds ±5%, the piezoelectric ceramic driven throttle valve responds within 10ms, releases / absorbs the airflow pulsation energy through the energy storage chamber, and maintains the stability of the branch pipe pressure.

8. The dust purge air system for the bottom of a power station boiler wind box as claimed in claim 1, characterized in that: The purge pipe is made of high temperature and wear-resistant alloy steel pipe with a coating thickness of 0.3-0.5mm; the purge hole is processed by laser precision punching technology, and the hole mouth is designed with a 30° chamfer.

9. The dust purge air system for the bottom of the power station boiler wind box as claimed in claim 8, characterized in that: An electric ball valve throttling mechanism is installed in the purge hole, and the opening is directly controlled by the pressure sensor signal; When it is detected that the air flow velocity at the purge hole outlet is lower than 60m / s, the ball valve opening increases; when it is higher than 100m / s, the opening decreases.

10. The dust purge air system for the bottom of the wind box of a power station boiler as claimed in claim 1, characterized in that: The purge pipe is fixed above the bottom truss of the bellows by U-bolts, and the distance between the bottom surface of the purge pipe and the bottom plate of the bellows is 400-600mm; partitions are arranged inside the bellows to divide the purge airflow into multiple areas, and branch pipelines are added in the area above the partitions to form layered purge pipelines, which are connected in parallel with the main purge pipeline.

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