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

Abstract

The utility model relates to the technical field of power station boiler air bellow bottom ash deposition blowing air systems, and aims to solve the problems that power station boiler air bellow bottom ash deposition affects safe operation of a boiler and the air distribution effect of a burner and the like. According to the technical scheme, two independent blowing air main pipes are led out from a boiler hot primary air system through a hot primary air taking unit, and each main pipe is provided with an electric inserting plate door and a manual turning plate door; the multi-stage branch pipeline unit extends from the main pipe to the left side and the right side of a boiler hearth to form a symmetrical branch pipe system, and a branch pipe comprises a plurality of branch pipes and extends to the front area and the rear area of an air bellow boiler. The air bellow bottom blowing unit comprises a blowing pipeline arranged in the air bellow, the blowing pipeline is fixed above a truss at the bottom of the air bellow and keeps a preset distance with a bottom plate of the air bellow, blowing holes are evenly distributed in the bottom face of the blowing pipeline in the axial direction, and the blowing pipeline sprays air flow towards the bottom plate of the air bellow and is communicated with the branch pipe through a distribution header. The device is mainly used for effectively purging accumulated dust at the bottom of the power station boiler bellows and guaranteeing stable and safe operation of the boiler.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of thermal power plant, more specifically, the utility model relates to a kind of for power station boiler air bellow bottom dust blowing system. BACKGROUND

[0002] The secondary air bellow of coal-fired boiler opposite combustion swirl burner is used to distribute the secondary air volume of each burner, and the overfire air bellow is used to reasonably distribute the overfire air volume to achieve the purpose of combustion support, burnout and control of nitrogen oxide generation. The air entering the secondary air bellow and the overfire air bellow is heated secondary air through the rotary air preheater. Due to the characteristics of flue gas and air heat exchange of the rotary air preheater, the secondary air carries the ash deposited on the heat exchange elements. Due to the structural characteristics of the bellow itself, the speed of the hot secondary air decreases after entering the bellow, and after a long period of accumulation, there will be ash accumulation at the bottom of the OFA bellow and the burner bellow, which will cause unreasonable air distribution and bellow cracking and ash leakage. Currently, there is no effective measure to prevent it, and the ash at the bottom of the bellow needs to be cleaned according to the needs during the boiler shutdown maintenance. SUMMARY

[0003] An object of the present utility model is to solve at least the above problems and provide at least the advantages to be explained later.

[0004] Another object of the present utility model is to provide a dust blowing system for the bottom of the air bellow of a power station boiler, which is designed to efficiently blow off the accumulated dust to ensure the safe and stable operation of the boiler.

[0005] Another object of the present utility model is to optimize the configuration of the blowing hole parameters to control the energy consumption while ensuring the blowing effect and achieve economic operation of the system.

[0006] Another object of the present utility model is to solve the air flow disturbance problem existing in the traditional air taking method and improve the stability of the blowing air by symmetrical air taking design.

[0007] Another object of the present utility model is to perfect the air bellow branch air distribution structure to ensure the accurate distribution of blowing air volume in different areas.

[0008] Another object of the present utility model is to optimize the installation position and fixing method of the blowing pipeline to improve the reliability of the system operation.

[0009] Another object of the present utility model is to improve the arrangement method of the blowing hole to enhance the uniformity of blowing coverage.

[0010] Another object of the present utility model is to add auxiliary blowing branch pipes to solve the problem of difficult removal of accumulated dust in specific areas.

[0011] Another object of the utility model is to optimize valve combination configuration, promote the convenience and sealing property of system operation.

[0012] Another object of the utility model is to solve the durability problem of pipeline material under high temperature environment, prolong the service life of equipment.

[0013] Another object of the utility model is to improve pipeline connection mode, improve system installation efficiency and sealing performance.

[0014] In order to realize these objects and other advantages according to the utility model, a kind of for power station boiler wind box bottom dust blowing system is provided, including:

[0015] Hot primary air taking unit, it is drawn from two independent blowing main pipe of boiler hot primary air system, and electric plug-in door and manual flap door are provided on each main pipe;

[0016] Multi-stage branch pipeline unit, it is extended to the left and right sides of boiler furnace by blowing main pipe respectively, and symmetrically distributed branch pipe system is formed, and branch pipe system includes multiple branch branch pipes, and branch branch pipe extends to the front and rear area of wind box;

[0017] Wind box bottom blowing unit, it includes blowing pipeline arranged in wind box, it is fixed on wind box bottom truss above by support and keeps predetermined interval with wind box bottom plate, blowing pipeline bottom surface is uniformly distributed blowing hole along axial direction;The direction of blowing gas flow of blowing hole is towards wind box bottom plate;Blowing pipeline is communicated with branch branch pipe by distribution header.

[0018] Preferably, the diameter of blowing hole of the utility model is 8-12mm, and the pitch of adjacent blowing hole is 400-600mm;

[0019] The blowing gas flow velocity of blowing hole is 70-110m / s, and the total mass flow of blowing system is controlled in 4-6t / h range by adjusting electric plug-in door opening degree;

[0020] The pipe diameter of blowing main pipe, branch branch pipe and blowing pipeline decreases gradually, and the wind speed in each section of pipeline is 20-30m / s;

[0021] The working parameter provided by hot primary air taking unit meets the wind pressure not less than 12kPa and temperature not less than 300 DEG C under BMCR condition.

[0022] Preferably, the taking point of hot primary air taking unit of the utility model is located on the downward main pipeline of boiler rear hot primary air, and two independent taking interfaces are symmetrically arranged on the left and right sides.

[0023] Preferably, the air bellow of the utility model includes a burner air bellow and a burnout air bellow, the multi-stage branch pipe unit includes two-stage branch structure, the main pipe branch is divided into two branch pipes, and each branch pipe is divided into a burner air bellow branch pipe and a burnout air bellow branch pipe.

[0024] Preferably, the vertical distance between the blowing pipe of the air bellow bottom blowing unit and the air bellow bottom plate is 400-600mm, and the U-shaped support is fixed to the air bellow bottom truss.

[0025] Preferably, the blowing holes are arranged in an even distribution along the blowing pipe axis, the center distance between adjacent blowing holes is 450-550mm, and the diameter of a single blowing hole is 8-12mm.

[0026] Preferably, an auxiliary blowing branch pipe is additionally arranged on the upper part of the partition plate of the branch pipe in the burner air bellow area, and the auxiliary blowing branch pipe is connected with the main blowing pipe in a T shape.

[0027] Preferably, the electric plug-in door and the manual flap door are arranged in series, the electric plug-in door is located on the upstream side of the manual flap door, and the distance between the two is 1.5-2 times the pipe diameter.

[0028] Preferably, the blowing pipe is made of high-temperature-resistant alloy steel, the pipe wall thickness is 6-8mm, and the surface is subjected to oxidation resistance treatment.

[0029] Preferably, the distribution header is connected with the branch pipe through a flange, and the distribution header is fixed with the blowing pipe through welding.

[0030] The utility model at least has the following beneficial effects:

[0031] The utility model realizes symmetrical blowing on both sides of the furnace through the independent double-way blowing wind main pipe design, effectively covers the whole area of the air bellow bottom, solves the problem of the blind area existing in the traditional single-side blowing, uses hot primary air as the blowing medium, avoids the risk of dewing caused by low-temperature air, ensures the dryness and high temperature of the blowing airflow, and improves the soot removal efficiency.

[0032] The optimized purging hole parameter design of this invention (diameter 8-12mm, pitch 400-600mm) ensures purging coverage while controlling the airflow velocity within an efficient range of 70-110m / s. This avoids energy waste caused by over-purging and ensures effective removal of ash particles. The progressively decreasing pipe diameter design maintains an air velocity of 20-30m / s in each section, preventing ash accumulation in the pipes and improving the system's self-cleaning capability. The symmetrical air intake design effectively reduces airflow disturbance in the main pipeline, ensuring balanced purging airflow between the two paths. The air intake point after the furnace is located in the downstream main pipeline of the hot primary air, utilizing gravity to reduce impurity deposition and ensure purging air quality. The BMCR operating condition parameter design ensures that the system maintains stable purging capability even when the boiler is running at full load. The two-stage branch structure of this invention enables independent air distribution between the burner wind box and the burnout air box, allowing for airflow adjustment based on the ash accumulation characteristics of different areas. The burner area adopts an auxiliary purging branch pipe design to solve the purging problem in the area above the baffle where ash easily accumulates, and improve the overall purging effect.

[0033] This utility model's purging pipe uses a U-shaped bracket fixed above the truss. The installation height of 400-600mm ensures the effective distance of the purging airflow while avoiding direct contact between the pipe and the bottom plate of the wind box, preventing vibration and wear. Symmetrically arranged purging holes ensure uniform airflow coverage of the entire bottom of the wind box, preventing localized ash accumulation. The axially evenly distributed purging hole design (center distance 450-550mm) forms a continuous purging band, combined with an 8-12mm orifice diameter, ensuring purging intensity while preventing airflow interference. This arrangement creates an effective purging width of 2-3m at the bottom of the wind box, adapting to the wind box size requirements of boilers of different capacities. The T-shaped connection design of the auxiliary purging branch pipe allows the purging airflow to bypass baffle obstacles and directly act on the ash-accumulated dead corners of the burner area. This structure improves the targeting of purging in specific areas and reduces the frequency of manual cleaning without changing the original pipe layout.

[0034] This utility model features a series configuration of an electric slide gate and a manual flap gate, providing dual protection through remote operation and mechanical isolation. An installation spacing of 1.5-2 times the pipe diameter ensures sufficient operating space for the valves while preventing the formation of vortex zones between the two valves, thus improving system sealing and operational safety.

[0035] The utility model discloses select high temperature resistant alloy steel material (wall thickness 6-8mm) to ensure that the pipeline is in 300 DEG C above high temperature environment long-term stable operation, surface oxidation treatment effectively delays material aging, prolongs equipment service life. The design makes the system can with boiler body synchronous maintenance, reduces the downtime maintenance time. The utility model discloses adopt the pipeline fixing mode that flange connection and welding are combined, guaranteeing the flexibility of installation, and ensuring system sealability. The flange connection of distribution header and branch branch pipe is convenient to dismount and maintain, and the welding fixation with purging pipeline enhances structural stability, and adapts to the complex vibration environment inside the wind box.

[0036] Other advantages, objects and features of the present utility model will be apparent from the following description, and will be understood by those skilled in the art upon reading and understanding the present utility model. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The utility model discloses a structure diagram for the bottom dust blowing system of the wind box of the power station boiler. DETAILED DESCRIPTION

[0038] The utility model will be further explained in detail below in combination with the drawings and examples, so that the person skilled in the art can implement according to the description.

[0039] It should be understood that the terms such as "have", "contain" and "include" used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0040] It should be noted that the experimental methods described in the following embodiments are all conventional methods, and the reagents and materials, unless otherwise specified, can be obtained from commercial channels.

[0041] In the description of the utility model, the orientation or positional relationship indicated by the terms "transverse", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the utility model.

[0042] As Figure 1 The utility model provides a kind of bottom dust blowing wind system for the wind box of power station boiler, it includes:

[0043] Hot primary air takes wind unit, and it is introduced from two independent blowing wind main pipes of boiler hot primary air system, and electric plug-in door and manual flap door are provided on each main pipe;

[0044] Multi-stage branch pipe unit, which is extended by the purge air main pipe to the left and right sides of the boiler furnace respectively, forming a symmetrically distributed branch pipe system, the branch pipe system contains a plurality of branch pipes, the branch pipes extend to the front and rear areas of the air box;

[0045] Air box bottom purge unit, which includes a purge pipe arranged inside the air box, fixed by a support above the air box bottom truss and maintaining a predetermined distance with the air box bottom plate, the bottom surface of the purge pipe uniformly distributes purge holes along the axial direction; the blowing direction of the purge holes is towards the air box bottom plate; the purge pipe is communicated with the branch pipes through a distribution header.

[0046] Hot primary air taking unit

[0047] The taking point is located at the hot primary air downcomer at the rear of the boiler, and two independent taking interfaces are symmetrically arranged on the left and right sides, with an interface spacing of 800-1200mm.

[0048] The working parameters of the hot primary air are wind pressure ≥12kPa and temperature ≥300℃ under BMCR condition, and the wind speed in the taking pipe is controlled at 20-30m / s.

[0049] The series spacing of the electric plug door and the manual flap door is 1.5-2 times the diameter of the pipe, for example, the spacing of DN250 pipe is 375-500mm.

[0050] The electric plug door can be selected from commercially available models (such as Jiangsu Shentong Valve Z941H type), with a diameter matching the main pipe and a temperature resistance ≥350℃.

[0051] The manual flap door can be selected from cast iron material, with a diameter of DN200-DN300, and equipped with a worm gear adjusting mechanism.

[0052] The taking pipe material can be selected from Q345R low alloy steel, with a wall thickness of 8-10mm, and the surface is sprayed with an aluminum-silicon coating for oxidation resistance.

[0053] The taking interface is welded below the hot primary air downcomer at the rear of the boiler, 2-3m away from the outlet of the air preheater, avoiding elbows and reducers.

[0054] The electric plug door is installed in the vertical section of the taking main pipe, and the manual flap door is located in the downstream horizontal section, with asbestos gasket sealing installed at the flange connection of the valve.

[0055] In implementation, first open the manual flap door to full open state, and then adjust the opening degree of the electric plug door to 30%-50%, so that the purge air mass flow is stabilized at 4-6t / h.

[0056] Multi-stage branch pipe unit

[0057] The main pipe branches are left and right branch pipes, the branch pipe diameter gradually decreases, for example, the main pipe is Φ273, the first level branch pipe is Φ219, and the second level branch pipe is Φ159.

[0058] The branch pipe system extends to the front and rear areas of the wind box furnace, the branch angle is 45°-60°, the branch pipe spacing matches the burner layer spacing, for example, 1200-1500mm.

[0059] The flow distribution ratio of the burner wind box branch pipe and the overfire air wind box branch pipe is 6:4, which is adjusted by the branch pipe orifice plate.

[0060] The branch pipe can be selected from GB / T8163 standard seamless steel pipe, and the elbow adopts 90° long radius elbow (R=1.5D) formed by molding. The distribution header tank can be selected from a segmented rectangular tank, which is provided with a guide plate inside, and is made of Q235B carbon steel with a wall thickness of 6mm. The flange connection can be selected from HG / T20592 standard protruding flange, and the sealing surface is covered with a graphite metal winding gasket.

[0061] The left and right branch pipes are laid horizontally along the boiler steel frame, 200-300mm away from the outer wall of the furnace, and are fixed to the support beam by U-shaped clamps. The burner wind box branch pipe penetrates into the upper part of the wind box partition, 100-150mm away from the top surface of the partition, and the auxiliary purge branch pipe is connected with the main branch pipe in a T shape with an included angle of 30°. The distribution header tank is installed near the maintenance door of the wind box side wall, connected with the branch pipe through flanges, and a blowdown valve (model J41H-16C) is arranged at the bottom of the header tank.

[0062] Wind box bottom purge unit

[0063] The vertical distance between the purge pipe and the wind box bottom plate is 400-600mm, the purge hole diameter is 8-12mm, the pitch is 450-550mm, and the single hole gas flow velocity is 70-110m / s.

[0064] The purge pipe adopts Φ89 seamless steel pipe with a wall thickness of 6-8mm, and the number of holes per meter in the axial direction is 8-10.

[0065] The U-shaped support spacing is 1.2-1.5m, and the support height is adjustable with an adjustment range of ±50mm.

[0066] The purge pipe can be selected from 06Cr25Ni20 heat-resistant alloy steel, and the surface is treated by aluminizing, and the temperature resistance is ≥600℃.

[0067] The U-shaped support can be selected from S30408 stainless steel with a thickness of 4-5mm, and the bolt hole is a long circular hole to adapt to thermal expansion.

[0068] The purge hole is processed by laser cutting process, and the hole edge chamfer is 0.5mm to prevent airflow turbulence.

[0069] The sweeping pipeline is arranged in parallel above the bottom truss of the air box, deviated from the center line of the truss by ≤10 mm, and is fixed by U-shaped support bolts.

[0070] The axis of the sweeping hole is at an angle of 15°-20° with the bottom plate of the air box, and the airflow impact area covers a width of 2-3 m of the bottom plate.

[0071] After installation, a sweeping test is performed using compressed air at a pressure of 0.5 MPa for 10 minutes to check for pipeline leaks and orifice blockage.

[0072] The hot primary air intake unit is designed with symmetric double channels to avoid airflow deflection caused by unilateral air intake and ensure balanced distribution of sweeping air volume. The multi-stage branch pipeline unit is designed with a stepwise decreasing pipe diameter to maintain a wind speed of 20-30 m / s in the pipeline, prevent ash deposition, and reduce system resistance. The directional sweeping hole layout of the air box bottom sweeping unit forms a continuous air film covering the bottom plate, increases the ash removal efficiency by 40%-60%, and reduces the frequency of manual cleaning.

[0073] Working process of the hot primary air intake unit

[0074] Two independent sweeping air main pipes (pipe diameter Φ273) are symmetrically introduced from the downward main pipeline of the boiler post-heating primary air (2-3 m away from the outlet of the air preheater), each main pipe is sequentially connected with an electric plug-in door (such as Z941H type) and a manual flap door. The distance between the two valves is 1.5-2 times the diameter of the pipeline (DN250 pipeline distance 375-500 mm). When the system starts, first fully open the manual flap door, then adjust the opening degree of the electric plug-in door to 30%-50%, introduce the hot primary air (BMCR condition, wind pressure ≥12 kPa, temperature ≥300℃) into the main pipeline, and control the sweeping air mass flow rate to be 4-6 t / h. The air intake point avoids bends and reducers to ensure stable airflow and avoid impurity deposition.

[0075] Working process of the multi-stage branch pipeline unit

[0076] The sweeping air main pipe symmetrically extends to the left and right sides of the boiler furnace, and after the first branch (Φ219 branch pipe), it is divided into a burner air box branch pipe and a combustion air box branch pipe (Φ159). The branch pipes are laid horizontally along the boiler steel frame, 200-300 mm away from the outer wall of the furnace. The burner air box branch pipe penetrates into the upper part of the air box partition (100-150 mm away from the top surface of the partition), and an auxiliary sweeping branch pipe (Φ89) is additionally arranged above the partition, which is connected with the main branch pipe in a T shape (angle 30°). The end of the branch pipe is connected with a distribution header (Q235B material), which is connected with the sweeping pipeline through flanges. A blowdown valve (J41H-16C type) is arranged at the bottom of the distribution header for periodic discharge of impurities.

[0077] Working process of the air box bottom sweeping unit

[0078] The blowing pipe (Φ89 heat-resistant alloy steel pipe, wall thickness 6-8 mm) is fixed on the upper side of the bottom truss of the air bellow by a U-shaped support (S30408 stainless steel) and is kept 400-600 mm vertically apart from the bottom plate of the air bellow. A Φ10 blowing hole is opened on the bottom surface of the pipe along the axial direction every 450-550 mm, the jet flow speed is 70-110 m / s, and the direction is 15°-20° to the bottom plate. The jet flow covers 2-3 m of the width of the bottom plate and forms a continuous blowing air film to make the accumulated dust continuously suspended and enter the furnace with the secondary air. During the operation of the system, blowing test is carried out periodically by compressed air (0.5 MPa) to check the pipe leakage and hole blockage and ensure the blowing effect.

[0079] Through the above process, the system realizes symmetrical air taking and staged air distribution, the blowing air flow uniformly covers the bottom plate of the air bellow, the accumulated dust removal efficiency is improved by 40%-60%, and the need for manual cleaning is avoided. The high-temperature characteristics of the hot primary air prevent dewing, the pipe diameter is designed to gradually decrease to maintain the wind speed of 20-30 m / s, and the risk of pipe accumulated dust is reduced. The directional layout and parameter optimization (Φ10 hole, 70-110 m / s flow speed) of the blowing hole balance the energy consumption and dust removal efficiency and ensure the safe operation of the boiler.

[0080] In another technical solution, the diameter of the blowing hole is 8-12 mm, and the pitch of adjacent blowing holes is 400-600 mm.

[0081] The jet flow speed of the blowing hole is 70-110 m / s, and the total mass flow of the blowing air system is controlled in the range of 4-6 t / h by adjusting the opening degree of the electric gate valve.

[0082] The pipe diameter of the blowing air main pipe, branch pipe and blowing pipe gradually decreases, and the wind speed in each section of the pipe is 20-30 m / s.

[0083] The working parameters provided by the hot primary air taking unit meet the requirements of wind pressure not less than 12 kPa and temperature not less than 300℃ under the BMCR condition.

[0084] The blowing hole parameter configuration: the diameter of the blowing hole is 8 mm, 10 mm or 12 mm, which is adjusted according to the particle size (0.5-2 mm) of the accumulated dust on the bottom plate of the air bellow, and the 10 mm hole diameter is suitable for most conditions.

[0085] The pitch of adjacent blowing holes is 400 mm, 500 mm or 600 mm, preferably 500 mm, corresponding to 8-10 holes per meter of pipe, covering a width of 2-3 m.

[0086] The jet flow speed is 70 m / s, 90 m / s or 110 m / s, which is selected according to the adhesion strength of the accumulated dust, and 90 m / s can effectively strip the accumulated dust layer under normal conditions.

[0087] The purge holes can be processed by laser cutting process, with a 0.5mm chamfer on the hole edge to reduce airflow turbulence.

[0088] The purge pipe can be made of 06Cr25Ni20 heat-resistant alloy steel (corresponding to ASTM 310S) with a wall thickness of 6mm and a temperature resistance of ≥600℃. The pipe surface can be sprayed with an aluminum-silicon coating (thickness 50-80μm) to delay high-temperature oxidation. The purge holes are evenly distributed along the pipe axis, with a 15°-20° angle between the hole centerline and the wind box bottom plate, covering the full width of the bottom plate. The hole spacing and angle are optimized by CFD simulation before installation to ensure that the airflow covers no dead angle. During commissioning, an anemometer (such as Testo405i) is used to measure the orifice flow rate, and the electric plug door opening is adjusted to meet the airflow speed standard.

[0089] The purge air system flow and pipe: The total mass flow of the purge air is controlled in the range of 4t / h, 5t / h or 6t / h, adjusted by the opening of the electric plug door (30%-50%), and the corresponding valve opening signal is fed back to the DCS system. The pipe diameter decreases step by step: main pipe Φ273 (DN250), first-stage branch pipe Φ219 (DN200), second-stage branch pipe Φ159 (DN150), and purge pipe Φ89 (DN80). The wind speed in each section of the pipe is 20m / s, 25m / s or 30m / s, with a main pipe wind speed ≤25m / s to reduce resistance and a branch pipe wind speed ≥20m / s to prevent dust accumulation.

[0090] The electric plug door can be selected from Jiangsu Shentong Valve Z941H type (DN250, pressure resistance 1.6MPa) with a 4-20mA electric actuator. The branch pipe can be selected from GB / T8163 standard seamless steel pipe with a bend curvature radius of 1.5D (such as Φ219 bend R=330mm). The pipe connection flange can be selected from HG / T20592 standard protruding flange with a stainless steel graphite wound gasket (pressure rating PN16).

[0091] The main pipe is laid horizontally along the boiler steel frame, and the branch pipe is provided with an expansion joint (such as JZH type axial compensator) before entering the wind box to compensate for thermal expansion displacement. A concentric reducer (such as Φ273 to Φ219) is used at the pipe diameter transition, with a transition length ≥300mm to avoid airflow sudden changes. After the system is put into operation, the main pipe pressure drop (≤2kPa) is monitored by a differential pressure transmitter, and if it exceeds the limit, the branch pipe filter (mesh size 20-40 mesh) is cleaned.

[0092] Hot primary air working parameters: under BMCR conditions, the hot primary air pressure is 12 kPa, 13 kPa or 14 kPa, the air taking point is located 2-3 m downstream of the outlet of the post-furnace air preheater to avoid the turbulent flow area. The hot primary air temperature is 300℃, 320℃ or 350℃, which is monitored in real time by a thermocouple (K type, accuracy ±1.5℃) to ensure that the blowing air is dry. The air speed in the air taking pipeline is controlled to be 20 m / s, 25 m / s or 30 m / s, which is determined by matching the pipeline diameter and flow rate.

[0093] The thermocouple can be selected from the WR series of Shanghai Automatic Instrument Factory No. 3 and installed in the straight pipe section (length ≥ 5D) of the air taking main pipe. The air taking pipeline can be selected from Q345R low alloy steel with a wall thickness of 10 mm and the inner wall is polished (roughness Ra ≤ 3.2 μm). The air taking interface can be welded with a reinforcing rib plate (thickness 12 mm) to prevent stress concentration of the main pipeline.

[0094] The air taking point is located at the bottom of the hot primary air downpipe, and the air taking pipe is inclined upward by 15° to connect to the blowing main pipe to avoid ash deposition. The temperature measuring point is arranged in the middle of the air taking pipe, which is ≥1 m away from the valve to reduce the interference of the valve throttling on the measurement. The thermocouple and pressure transmitter (such as ROSEMOUNT 3051 type) are regularly checked to ensure the accuracy of the parameter feedback.

[0095] In the technical solution, the optimized design of the blowing hole parameters (Φ10 hole, 500 mm pitch, 90 m / s flow rate) balances the ash removal efficiency and energy consumption, and the ash deposition removal rate is increased by 50%-70%. The stepwise decrease in pipe diameter and the control of wind speed (20-30 m / s) reduce the pipeline resistance (pressure drop ≤2 kPa), reduce the energy consumption of the fan, and avoid secondary ash deposition. The high temperature (≥300℃) of the hot primary air and the stable air pressure (≥12 kPa) ensure that the blowing air flow is dry and has sufficient power, which meets the long-term operation requirements of the BMCR condition.

[0096] In another technical solution, the air taking point of the hot primary air taking unit is located on the hot primary air downpipe of the post-furnace of the boiler, and two independent air taking interfaces are symmetrically arranged on the left and right sides.

[0097] Air taking point position design

[0098] The air taking point is located on the hot primary air downpipe of the post-furnace of the boiler, and is specifically arranged in the straight pipe section 2-3 m downstream of the outlet of the air preheater to avoid the turbulent flow area of the elbow, the variable diameter section and the valve. The air taking interface spacing is 800-1200 mm and is symmetrically distributed on the centerline positions of the main pipe. The air taking pipeline is connected to the main pipeline at an upward angle of 30° to avoid ash deposition. The wall thickness of the main pipeline in the air taking point area can be increased to 12-14 mm, and a reinforcing rib plate (thickness 10 mm) is welded to reduce the risk of stress concentration.

[0099] The main pipe of hot primary air can be made of Q345R low alloy steel, with polished inner wall (roughness Ra≤3.2 μm) and sprayed aluminum-silicon coating (thickness 50-80 μm) on the outer wall to delay oxidation. The flange of the air extraction interface can be a HG / T20592 standard raised flange (PN16 pressure rating), and the sealing gasket can be a stainless steel graphite wound gasket. During installation, the air extraction pipe needs to be perpendicular to the main pipe axis with a deviation of ≤2°, and the weld quality is detected by ultrasonic testing.

[0100] Symmetrical air extraction interface configuration

[0101] The left and right air extraction interfaces are independently set, with a matching interface diameter and a blowing wind main pipe (such as DN250), and the center elevation deviation of the interface flange is ≤5 mm. Each air extraction interface is equipped with a set of electric plug-in door (such as Jiangsu Shentong Z941H type) and a manual flap door (such as Shanghai Lianggong L41H type), and the valve series spacing is 1.5-2 times the pipe diameter (DN250 pipe spacing 375-500 mm). The valve actuator is directed outward, which is convenient for operation and maintenance. The air extraction branch pipe can be made of Q345R steel pipe with the same material as the main pipe, and the elbow is a molded 90° long radius elbow (R=1.5D). When the branch pipe penetrates through the boiler steel frame, an axial compensator (such as JZH type) is set to absorb thermal expansion displacement with a compensation amount of ≥20 mm. After installation, the pipeline tightness is detected by water injection test (pressure 1.25 times working pressure) with a pressure retention time of ≥30 minutes without leakage.

[0102] The hot primary air parameters at the air extraction point need to meet the wind pressure ≥12 kPa and the temperature ≥300℃ under BMCR working condition, which are monitored in real time by differential pressure transmitter (such as ROSEMOUNT 3051 type) and K-type thermocouple (such as Shanghai Automation Instrument Factory No.3 WR series). The air velocity in the air extraction pipe is controlled at 20-30 m / s, which is determined by pipe diameter and flow rate (such as Φ273 pipe corresponding to 4-6 t / h flow rate).

[0103] During commissioning, the portable air speed meter (such as Testo 405i) is used to measure the flow rate at the air extraction pipe outlet, and the electric plug-in door opening is adjusted to stabilize the flow rate at 25±5 m / s. The air extraction pipe inlet filter screen (mesh size 20-40 mesh) is cleaned regularly to prevent ash blockage. After the system is put into operation, the air extraction interface weld and support bolt fastening state are checked every quarter, the data are recorded and compared with the initial parameters, and the deviation is more than 10% when the calibration and maintenance are carried out.

[0104] The air taking point position optimization (2-3 m straight pipe section downstream of the air preheater) ensures stable airflow and low ash content, reducing the wear of the system caused by impurities in the purge air; the symmetrical air taking interface design (spacing 800-1200 mm) balances the distribution of the purge air on both sides, avoiding the problem of uneven air distribution caused by one-sided flow; real-time monitoring of air taking parameters and valve adjustment (flow rate 25±5 m / s) ensure stable operation of the system under BMCR conditions, and the fluctuation range of the purge air volume is ≤5%.

[0105] In another technical solution, the air taking point position optimization (2-3 m straight pipe section downstream of the air preheater) ensures stable airflow and low ash content, reducing the wear of the system caused by impurities in the purge air; the symmetrical air taking interface design (spacing 800-1200 mm) balances the distribution of the purge air on both sides, avoiding the problem of uneven air distribution caused by one-sided flow; real-time monitoring of air taking parameters and valve adjustment (flow rate 25±5 m / s) ensure stable operation of the system under BMCR conditions, and the fluctuation range of the purge air volume is ≤5%.

[0106] Two-stage branch pipe structure design

[0107] The main pipe is divided into two symmetrical first-stage branch pipes (Φ219) after being drawn from the hot primary air pipe, and each first-stage branch pipe is further divided into a burner air box branch pipe (Φ159) and a burnout air box branch pipe (Φ159). The branch angle is 45°-60°, and the flow distribution ratio of the burner air box branch pipe to the burnout air box branch pipe is 6:4, which is adjusted by a branch pipe orifice plate (hole diameter Φ30-Φ50). The branch pipe spacing matches the burner layer spacing, for example, 1200-1500 mm, to ensure uniform distribution of airflow to different areas of the air box. The branch pipe can be made of GB / T8163 standard seamless steel pipe with Q345R low alloy steel and a wall thickness of 6-8 mm. The orifice plate can be made of 304 stainless steel with a surface polishing treatment (roughness Ra≤3.2 μm). During assembly, the first-stage branch pipe is laid horizontally along the boiler steel frame, 200-300 mm away from the outer wall of the furnace, and is fixed to the support beam by a U-shaped clamp. The burner air box branch pipe penetrates into the upper part of the air box partition, 100-150 mm away from the top surface of the partition, and the burnout air box branch pipe extends to the rear wall area of the air box, with a distribution header set at 500 mm from the bottom plate.

[0108] Branch pipe connection and flow control

[0109] The burner wind box branch pipe and the overfire air wind box branch pipe end are connected with the blowing pipe through the distribution header tank (Q235B material, wall thickness 6mm), the inside of the header tank is provided with a flow guide plate (thickness 3mm), and the airflow turbulence is reduced. The branch pipe and the header tank are connected through flanges (HG / T20592 standard flange), and the sealing gasket is a stainless steel graphite winding gasket (temperature resistance ≥400℃). The flow control is adjusted to 30%-50% through the opening degree of the electric plug-in plate door (such as Z941H type), and the differential pressure transmitter (ROSEMOUNT 3051 type) is used to monitor the branch pipe differential pressure (≤2kPa), so that the flow is stably controlled in the range of 4-6t / h. An axial compensator (JZH type) is arranged in front of the branch pipe penetrating into the wind box, and the compensation amount is ≥20mm, so that the thermal expansion displacement is absorbed. During the debugging, the portable air speed meter (Testo 405i) is used to measure the flow velocity of the branch pipe outlet, and the orifice plate aperture is adjusted to make the flow velocity stable at 25±5m / s. The inlet filter screen (mesh number 20-40 mesh) of the branch pipe is cleaned regularly to prevent the ash slag from being blocked.

[0110] The burner and the overfire air wind box are independently provided with air

[0111] The burner wind box branch pipe is additionally provided with an auxiliary blowing branch pipe (Φ89) above the partition plate, which is connected with the main branch pipe in a T-shaped mode (included angle 30°), the blowing holes (Φ10) are arranged in the axial direction, the spacing is 500mm, the airflow velocity is 90m / s, and the ash accumulation area on the top of the partition plate is covered. The overfire air wind box branch pipe blowing pipe is arranged above the bottom plate truss, and the spacing between the bottom plate is 500mm. The blowing hole direction is 15° with the bottom plate, and a continuous air film is formed to disturb the accumulated ash. The auxiliary blowing branch pipe can be made of 06Cr25Ni20 heat-resistant alloy steel and is subjected to aluminizing treatment (thickness 50μm). During installation, the auxiliary branch pipe is welded on the top of the main branch pipe and is fixed to the side wall of the wind box through a support (S30408 stainless steel). After the system is put into operation, the branch pipe welding seam and the flange sealing property are checked every quarter, the differential pressure data are recorded, and when the deviation exceeds 10%, the valve opening degree is calibrated.

[0112] In the technical scheme, the two-stage branch structure (main pipe→left and right branch pipes→burner / overfire air branch pipe) realizes accurate distribution of air volume, the blowing strength of the burner area is increased by 30%-40%, and different ash accumulation characteristics are adapted. The independent air supply design (flow ratio 6:4) considers the ash removal efficiency of the burner and the overfire air wind box, the ash removal rate is increased by 50%-70%, and the risk of wind box cracking is reduced. The auxiliary blowing branch pipe (T-shaped connection) covers the dead angle on the top of the partition plate, and forms a three-dimensional ash removal network with the main blowing pipe, and the manual cleaning frequency is reduced by more than 60%.

[0113] In another technical scheme, the vertical distance between the blowing pipe of the wind box bottom blowing unit and the wind box bottom plate is 400-600mm, and the U-shaped support is fixed to the wind box bottom truss.

[0114] Purge pipe installation spacing control

[0115] The vertical distance between the purge pipe and the bottom plate of the wind box is set to 400 mm, 500 mm, or 600 mm, preferably 500 mm. This distance is achieved by U-shaped bracket height adjustment, with an error control within ±10 mm. The purge pipe is arranged in parallel above the truss, with a deviation of ≤5 mm from the truss center line, ensuring uniform airflow coverage. A laser range finder (such as Leica DISTO series) is used to calibrate the spacing during installation, and the bracket position is locked after adjustment. The purge pipe can be made of Φ89 seamless steel pipe (material 06Cr25Ni20) with a surface aluminizing treatment (thickness 50 μm) and a temperature resistance ≥600℃. The U-shaped bracket can be made of S30408 stainless steel with a thickness of 4-5 mm, and the bolt hole is a long circular hole (length 20-30 mm) allowing thermal expansion displacement. The bracket spacing is 1.2-1.5 m, and at least 3 sets of brackets are provided for each section of pipe to prevent vibration deformation.

[0116] U-shaped bracket structure and fixing method

[0117] The U-shaped bracket is composed of a bottom plate, side plates, and a top clamp. The bottom plate is fixed to the upper surface of the truss by M12 expansion bolts, and the height of the side plates can be adjusted within the range of 400-600 mm. The top clamp is lined with a ceramic fiber pad (thickness 3 mm) to prevent direct friction between the pipe and metal. During bracket assembly, first position the bottom plate, then weld the side plates, install the clamp, and finally adjust the pipe height and lock the bolts. The bracket bottom plate can be made of Q235B carbon steel with dimensions 200 mm x 100 mm x 10 mm and a surface zinc plating for rust prevention. The expansion bolts can be selected from the FIS V series of Huishu, with a tensile strength ≥8.8 grade. After installation, hammer test (impact energy 10 J) is required to check the firmness of the bracket fixation, with no looseness or displacement.

[0118] Purge pipe and truss collaborative design

[0119] The purge pipe is laid along the truss girder, avoiding the internal support rib of the wind box. The gap between the pipe and the truss is ≥50 mm, facilitating maintenance operations. Guide brackets (such as sliding supports) are set at the truss corners to compensate for the pipe displacement caused by thermal expansion (compensation ≥15 mm). The direction of the purge hole forms a 15°-20° angle with the truss beam to avoid direct airflow impact on the truss structure. The guide bracket can be made of a polytetrafluoroethylene sliding gasket (thickness 5 mm) with a friction coefficient ≤0.1. After installation, water injection test (pressure 0.5 MPa) is performed to detect the pipe sealing performance, with no leakage for 10 minutes of pressure retention. The bracket bolt torque (standard value 25-30 N·m) is checked regularly to prevent pipe sagging caused by looseness.

[0120] In the technical solution, the precise control (500mm±10mm) of the blowing pipe spacing ensures that the airflow effectively impacts the bottom plate, the dust suspension rate is increased by 50%-60%, and the frequency of manual cleaning is reduced. The adjustable design of the U-shaped support adapts to different wind box structures, and the installation efficiency is improved by 30%. The support vibration resistance meets the boiler operation vibration requirements (amplitude ≤0.1mm). The pipeline and truss are arranged cooperatively to avoid airflow interference, improve system operation stability, reduce wind box bottom plate wear rate by 40%, and prolong equipment service life.

[0121] In another technical solution, the blowing hole arrangement is uniformly distributed along the blowing pipe axis, the center distance between adjacent blowing holes is 450-550mm, and the diameter of a single blowing hole is 8-12mm.

[0122] Blowing hole arrangement: blowing holes are uniformly distributed along the blowing pipe axis, and the center distance between adjacent holes can be selected as 450mm, 500mm or 550mm. This parameter design is based on the characteristics of wind box bottom plate dust particles, and is verified by CFD simulation to ensure that the airflow coverage width reaches 2-3m. Laser cutting process can be used to process the hole position, and 0.5mm chamfering treatment is performed on the hole edge to avoid airflow turbulence.

[0123] Hole diameter parameter selection: the diameter of a single blowing hole can be selected as 8mm, 10mm or 12mm. Specific selection needs to be combined with dust particle size (0.5-2mm) and adhesion strength, for example, 10mm hole diameter can balance blowing strength and energy consumption under most working conditions. The hole flow rate is controlled within 70-110m / s by the opening degree of the electric plug-in door, which can be adjusted by on-site measurement with Testo 405i anemometer.

[0124] Pipe and installation: the blowing pipe can be selected as Φ89×6mm 06Cr25Ni20 heat-resistant alloy steel pipe, and the surface is treated with aluminizing (thickness 50-80μm). The S30408 stainless steel U-shaped support is fixed to the wind box bottom truss, the support spacing is 1.2-1.5m, and the vertical distance between the pipe and the bottom plate is 400-600mm. During installation, the pipe levelness is adjusted by long round hole bolts, and the deviation is controlled within ±10mm.

[0125] In the modification of a certain 660MW unit, the blowing holes are arranged at a pitch of 500mm and a diameter of 10mm, and cooperate with an airflow speed of 90m / s to increase the wind box bottom dust removal rate by 50%-70%. Regularly check the hole state through compressed air (0.5MPa) blowing test, and the inspection shows that the pipe has no obvious wear after 2000 hours of system operation, and the blowing coverage rate is more than 95%.

[0126] For the burner windbox partition area, a Φ89 auxiliary branch pipe can be connected to the main pipe T, and a 30° inclined sweeping hole (hole diameter 8 mm, pitch 400 mm) is added to solve the problem of dust deposition on the top of the partition. This structure has been applied in a certain Huaneng power plant, which reduces the dust deposition in this area by 80% and prolongs the maintenance period to more than 6 months.

[0127] This scheme realizes uniform sweeping of the entire area at the bottom of the windbox through parameterized design and engineering verification, effectively suppresses dust deposition, and ensures long-term stable operation of the boiler. The system configuration meets the requirements of DL / T 5254-2010 "Technical Code for Design of Flue Gas, Air and Pulverized Coal Piping in Thermal Power Plants", the sweeping air speed is matched with the piping flow rate, and the risk of secondary dust deposition is avoided.

[0128] In another technical solution, the auxiliary sweeping branch pipe is added to the top of the partition in the branch pipe of the burner windbox area, and the auxiliary sweeping branch pipe is connected to the main sweeping pipe in a T shape.

[0129] The auxiliary branch pipe is installed at the top of the partition in the burner windbox branch pipe, and the installation position is 100-150 mm away from the top surface of the partition. This area is prone to dust deposition, and CFD simulation shows that the addition of the branch pipe can increase the sweeping coverage by 30%. Φ89 seamless steel pipe with a wall thickness of 6 mm and a material of 06Cr25Ni20 heat-resistant alloy steel can be used, and the surface is treated with aluminizing (thickness 50-80 μm).

[0130] Connection design: The auxiliary branch pipe and the main sweeping pipe are connected in a T shape with an included angle of 30°±5°. The welding process meets the DL / T 869-2012 standard, and the weld needs to be detected by ultrasonic flaw detection. The end of the branch pipe can be equipped with a manual regulating valve (such as Shanghai Lianggong L41H type) with an opening adjustment range of 0-90°, and a differential pressure transmitter (such as Rosemount 3051 type) is used to monitor the flow.

[0131] Sweeping hole parameter configuration: Φ8-12 mm sweeping holes are arranged on the bottom surface of the auxiliary branch pipe with a hole spacing of 400-500 mm and an air flow speed of 80-100 m / s. In the application of a certain 660 MW unit, Φ10 holes with a pitch of 450 mm are used to increase the dust removal rate on the top of the partition from 35% to 85%. The hole can be equipped with a flow guide cover (material 304 stainless steel) to adjust the airflow direction to an angle of 45° with the partition.

[0132] Installation and fixation: auxiliary branch pipes are fixed to the side wall of the wind box by S30408 stainless steel U-shaped supports with a spacing of 1.2-1.5 m. The vertical distance between the pipeline and the bottom plate of the wind box is kept at 400-600 mm, and the height adjustment of ±50 mm is realized through long round hole bolts. During debugging, the Testo 405i anemometer is used to measure the orifice flow rate, and the valve opening is adjusted to make the flow rate deviation of each hole ≤10%.

[0133] In the reconstruction of a certain Huaneng power plant, the amount of ash accumulated in the burner wind box partition area was reduced from 2.3 tons per month to 0.4 tons after the auxiliary branch pipe was put into operation, and the maintenance period was extended to 6 months. The wear of the purge hole was detected as 0.1 mm after 2000 hours of operation, which meets the requirements of DL / T 5190.5-2012 "Code for Design of Steam and Water Piping in Thermal Power Plants".

[0134] This scheme solves the problem of ash accumulation in the burner wind box partition area by adding auxiliary purge branch pipes. The design of the branch pipe parameters meets the DL / T 5254-2010 standard, and the purge gas flow rate is matched with the pipeline flow rate to avoid interference with the main air distribution system. Practical application shows that this structure can effectively improve the ash removal efficiency in a specific area and reduce the cost of manual maintenance.

[0135] In another technical solution, the electric plug-in door and the manual flap door are arranged in series, and the electric plug-in door is located on the upstream side of the manual flap door with a spacing of 1.5-2 times the pipe diameter.

[0136] Valve configuration parameters: the electric plug-in door and the manual flap door are arranged in series, and the electric plug-in door is located on the upstream side with a spacing of 1.5-2 times the pipe diameter. For example, the spacing of DN250 pipes is 375-500 mm, which is determined by fluid mechanics calculation to ensure that there is no mutual interference during valve operation. The electric plug-in door can be selected from Jiangsu Shentong Z941H type (nominal diameter DN250, temperature resistance 350℃), and the manual flap door can be selected from Shanghai Lianggong L41H type (nominal diameter DN250, operating torque ≤120 N·m).

[0137] Installation position design: the electric plug-in door is installed on the vertical section of the air intake main pipe, and the manual flap door is located on the downstream horizontal section. The vertical section is convenient for maintenance of the electric actuator, and the horizontal section is convenient for manual operation. Asbestos rubber gaskets (thickness 3 mm, temperature resistance 400℃) are installed at the flange connection of the valve, and 35CrMoA alloy steel is used for bolts, which are fastened according to HG / T20592 standard with a torque control of 150-200 N·m.

[0138] System verification and maintenance: In the transformation of a 660 MW unit, the valve spacing is configured according to 1.8 times the pipe diameter (450 mm), and there is no leakage after water pressure test (1.25 times the working pressure) for 30 minutes. After the system is put into operation, the opening of the electric gate valve is controlled at 30%-50%, and the differential pressure transmitter (Rosemont 3051 type) is used to monitor the pressure difference before and after the valve ≤2kPa. The sealing test of the manual flap valve is carried out every year during maintenance, and the leakage shall be ≤0.1% of the rated flow.

[0139] Function implementation process: When the system starts, first open the manual flap valve, then adjust the purge air volume to 4-6t / h through the electric gate valve. When the system needs to be isolated, first close the electric gate valve, then manually close the flap valve to ensure double sealing. The valve operation signal is connected to the DCS system, which has a fault alarm function. When the travel deviation of the electric actuator exceeds 5%, the alarm is triggered.

[0140] Material and process: The valve body can be made of WCB cast steel, and the sealing surface can be welded with STL alloy (thickness ≥3mm) to adapt to working conditions above 300℃. The flange connection adopts HG / T20592 protruding flange, and the bolt is selected as 8.8 grade high strength bolt with double nut anti-loose design. When installing, the deviation between the valve axis and the pipeline axis shall be ≤2° to ensure smooth flow.

[0141] This scheme realizes reliable control and maintenance of the purge air system through reasonable valve selection and arrangement. The series configuration ensures the safety of operation, and the spacing design avoids vortex and improves the sealing performance of the system. In the application of a certain power plant of China Huaneng, the valve leakage rate is reduced from 3% before the transformation to 0.2%, the maintenance period is extended to 24 months, which meets the requirements of DL / T 5190.5-2012 "Code for Design of Steam and Water Piping in Thermal Power Plants".

[0142] In another technical scheme, the purge air system for the dust blowing of the bottom of the air box of the power plant boiler is made of high-temperature resistant alloy steel, and the wall thickness of the pipeline is 6-8mm, and the surface is subjected to oxidation resistance treatment.

[0143] Material selection and wall thickness parameters: The purge air pipeline can be made of 06Cr25Ni20 heat-resistant alloy steel (corresponding to ASTM 310S), which has good oxidation resistance in an environment above 300℃. The wall thickness of the pipeline can be selected as 6mm, 7mm or 8mm according to the design pressure, for example, 8mm wall thickness is used in the transformation of a certain 660 MW unit to meet the requirement of 1.6MPa working pressure. The material shall meet the requirements of GB / T 14976 standard, and the delivery state is solid solution treatment.

[0144] Surface treatment process: The outer surface of the pipeline can be treated by aluminizing, the thickness of the aluminized layer is 50-80 μm, the treatment temperature is 950-1050 ℃, and the holding time is 4-6 hours. This process can form a dense Al2O3 protective film, significantly improving the high-temperature oxidation resistance. After treatment, the surface roughness Ra is ≤6.3 μm, meeting the requirements of DL / T 774-2015 "Operation and Maintenance Regulations for Thermal Automation System of Power Plant".

[0145] Installation and verification: The pipeline is fixed to the bottom truss of the wind box by S30408 stainless steel U-shaped support, the support spacing is 1.2-1.5 m. During installation, the vertical distance between the pipeline and the bottom plate is controlled at 400-600 mm, the levelness is adjusted by long round hole bolts, and the deviation is ≤10 mm. In a certain power plant application, after 2000 hours of operation, the aluminized layer integrity rate reaches 98%, and the wall thickness thinning amount is only 0.1 mm.

[0146] Performance test: Under laboratory conditions, the 310S steel pipe test piece is placed in a muffle furnace, heated to 600 ℃ at a rate of 5 ℃ / min and held for 100 hours, and the oxidation weight gain is ≤0.5 mg / cm². On-site infrared temperature measurement instrument is used to monitor the surface temperature of the pipeline to ensure that the long-term operating temperature does not exceed the design value of 350 ℃.

[0147] Engineering application: In the transformation of a certain Huaneng power plant, the pipeline of this material has no obvious oxide skin peeling after 3 years of operation, while the ordinary carbon steel pipeline has appeared local perforation at the same period. After aluminizing treatment, the service life of the pipeline is extended from 18 months to more than 5 years, and the annual maintenance cost is reduced by 60%.

[0148] This scheme effectively solves the problem of pipeline oxidation in high temperature environment through material optimization and surface treatment. The wall thickness design meets the requirements of DL / T 5190.5-2012 "Design Specification for Steam and Water Piping in Power Plant", ensuring the pressure bearing capacity. Practical application shows that this structure can be synchronized with the boiler body for maintenance, reducing downtime and improving system reliability.

[0149] In another technical scheme, the distribution header and the branch pipe are connected by flanges, and the distribution header and the blowing pipeline are fixed by welding.

[0150] Flange connection parameter design: The distribution header and the branch pipe are connected by HG / T20592 standard flange connection, the flange material can be selected as Q235B carbon steel, the nominal pressure PN16, and the sealing surface is covered with stainless steel graphite winding gasket (thickness 3 mm, temperature resistance 400 ℃). The bolt can be selected as 8.8 grade high strength bolt (GB / T 5782), and the fastening torque is controlled at 150-200 N·m. The flange spacing and the pipeline diameter are matched, for example, the flange spacing of DN150 pipeline is 1.5-2 times the pipe diameter.

[0151] Welding fixation process: The distribution header and the purge pipe adopt full penetration structure, and the welding process meets the DL / T 869-2012 standard. The material of the header is Q235B carbon steel (wall thickness 6 mm), and the material of the pipe is 06Cr25Ni20 heat-resistant alloy steel (wall thickness 6-8 mm). Before welding, the groove is processed (angle 60°±5°), argon arc welding is used for backing, and electric arc welding is used for filling. The weld needs to be detected by 100% ultrasonic flaw detection (II level qualified). Stress relief treatment is carried out after welding to eliminate welding deformation.

[0152] Installation and verification: The distribution header is installed near the access door of the wind box side wall, fixed on the wind box structure beam by a support, and the horizontal deviation is ≤3 mm / m. When the branch pipe flange is connected, the coaxiality deviation should be ≤1 mm to avoid welding stress concentration. In the modification of a certain 660 MW unit, after using this connection method, the system leakage rate is reduced from 0.5% to 0.1%, and no leakage is found after 1.25 times working pressure water pressure test for 30 minutes.

[0153] Maintenance convenience design: The flange connection is convenient for quick disassembly during system maintenance, and the disassembly time of a single flange group is about 1.5 hours. The welding fixation ensures that the purge pipe does not loosen in the 300℃ operating environment, and the weld displacement is ≤0.5 mm after 2000 hours of vibration test. A blowdown valve (such as J41H-16C type) is arranged at the bottom of the distribution header to discharge impurities regularly, and the blowdown period can be set to once every 1000 hours of operation.

[0154] Material and process verification: After high temperature aging test (350℃×1000 hours), the compression rate change of stainless steel graphite wound gasket is ≤5%. The tensile strength of the welded joint is ≥500 MPa, and the impact toughness is ≥34 J (-20℃). In the application of a certain Huaneng power plant, the inspection after 3 years of operation shows that there is no leakage and no crack in the weld, which meets the requirements of DL / T 5190.5-2012 "Code for Design of Steam and Water Piping in Thermal Power Plants".

[0155] This scheme combines flange and welding connection methods to balance system sealing and maintenance convenience. Flange connection ensures efficient maintenance, and welding fixation ensures high temperature operation stability. Practical application shows that this structure can reduce the risk of leakage, prolong the maintenance period, and meet the requirements of the piping design specification of thermal power plants.

[0156] Application example of a certain 660 MW ultra-supercritical unit wind box dust blowing and purging system

[0157] I. System configuration

[0158] The unit adopts wall opposed firing, equipped with 6 layers of swirl burner and 1 layer of OFA. The purge system is symmetrically introduced from the main pipe of the hot primary air after the furnace (BMCR condition: air pressure 13.14 kPa, temperature 333℃) to two Φ273 main pipes, and is provided with an electric gate valve (Z941H type) and a manual flap valve (L41H type) in series. The main pipe is divided into Φ219 primary branch pipes, which are further divided into Φ159 burner air box branch pipes and OFA air box branch pipes. The Φ89 purge pipe is arranged inside the air box, made of 06Cr25Ni20 heat-resistant alloy steel pipe (wall thickness 8mm), 500mm away from the bottom plate, and Φ10 purge holes are arranged at an interval of 500mm. The auxiliary branch pipe is arranged on the upper part of the air box partition, and is connected with the main pipe in a 30° T shape.

[0159] II. Work flow

[0160] 1. Air taking stage: the manual flap valve is fully opened at start-up, and the electric gate valve is adjusted to 40% opening to introduce the hot primary air into the system, with the total mass flow stabilized at 5t / h. The air taking point is located 2.5 meters downstream of the straight pipe section of the air preheater outlet, avoiding bends and valves to ensure stable airflow.

[0161] 2. Air distribution stage: the main pipe air velocity is 25m / s, which is divided into the burner air box (60% flow) and the OFA air box (40% flow) through the primary branch pipe (22m / s). The auxiliary branch pipe (flow velocity 90m / s) is arranged above the partition of the burner air box branch pipe to blow the top of the partition, and the main branch pipe blowing pipe covers the bottom plate area at a flow velocity of 85m / s.

[0162] 3. Purging stage: the blowing pipe in the air box forms a continuous air film, and the accumulated ash is lifted by the airflow and enters the furnace with the secondary air. The system automatically switches to the standby route for blowing every 8 hours of operation, and the electric gate valve of the other route is closed when operating in single route, while the manual flap valve remains fully open.

[0163] 4. Maintenance stage: blowing test is conducted every month by compressed air (0.5MPa) to check the blockage of the orifice. The valve tightness is checked every quarter to ensure that the leakage rate is less than 0.1%. The thickness of the aluminized layer is checked during annual maintenance, and the average thinning amount is controlled within 0.05mm / year.

[0164] III. Effect of use

[0165] 1. Ash accumulation control: after the transformation, the amount of accumulated ash at the bottom of the air box is reduced from 3.2 tons per month to 0.6 tons, the ash removal rate on the top of the partition is increased to 85%, and the outlet flue gas temperature deviation of the furnace is reduced from ±25℃ to ±12℃.

[0166] 2. Operation reliability: No pipeline leakage or valve jam occurred in 18 months of operation. The primary air temperature was stable at 320-340℃, and the secondary air temperature was not affected. The response time of the electric plug door adjustment was less than 5 seconds, meeting the control requirements of the DCS system.

[0167] 3. Economic benefits: The maintenance period was extended from 3 months to 6 months, and the time for cleaning accumulated dust during a single maintenance was reduced by 80%. Based on 5000 hours of annual operation, labor costs were saved by about 280,000 yuan, and the risk of unplanned shutdown due to accumulated dust was reduced.

[0168] 4. Environmental benefits: After improving the air distribution uniformity of the burner, the NOx emission concentration decreased by 15-20 mg / m³, the oxygen deviation was less than 0.5%, and the boiler efficiency increased by 0.3%.

[0169] Four, application verification

[0170] After implementation in a certain Huaneng power plant, a third-party testing agency tested:

[0171] The coverage width of the purge hole reached 2.8m, and the wind speed deviation between adjacent holes was less than 8%

[0172] The thickness of the accumulated dust layer at the bottom of the wind box was reduced from 15-20mm before the transformation to 3-5mm

[0173] The system resistance was less than 1.8kPa, which was 2kPa lower than the design value

[0174] The oxidation rate of the aluminized layer was less than 0.01mm / year in a 350℃ operating environment

[0175] This example shows that the purge system realizes efficient control of the accumulated dust at the bottom of the wind box through parameterized design and reasonable layout, meets the requirements of DL / T 5174-2017 "Technical Regulations for Boiler Furnace Safety Monitoring System of Thermal Power Plants", and provides a replicable transformation scheme for similar units.

[0176] The number of devices and the processing scale described here are used to simplify the description of the utility model. The application, modification and change of the utility model are obvious to those skilled in the art.

[0177] Although the embodiments of the utility model have been disclosed as above, they are not limited to the applications listed in the specification and the embodiments. They can be fully applied to various fields suitable for the utility model, and additional modifications can be easily realized by those skilled in the art. Therefore, the utility model is not limited to specific details and the figures shown and described herein without departing from the general concept defined by the claims and the equivalent scope.

Claims

1. A system for blowing away ash accumulated at the bottom of a power plant boiler air box, characterized in that, include: The hot primary air intake unit draws two independent purge air mains from the boiler hot primary air system. Each main is equipped with an electric slide gate and a manual flap gate. The multi-level branch pipe unit extends from the main purging air pipe to the left and right sides of the boiler furnace, forming a symmetrically distributed branch pipe system. The branch pipe system includes multiple branch pipes, which extend to the front and rear areas of the wind box. The bottom purging unit of the air box includes a purging pipe arranged inside the air box, which is fixed above the bottom truss of the air box by a bracket and maintains a predetermined distance from the bottom plate of the air box. Purging holes are evenly distributed along the axial direction on the bottom surface of the purging pipe. The direction of the airflow ejected from the purging holes is towards the bottom plate of the air box. The purging pipe is connected to the branch pipe through the distribution box.

2. The ash-blowing air system for the bottom of the wind box of a power plant boiler as described in claim 1, characterized in that, The diameter of the purge hole is 8-12mm, and the pitch between adjacent purge holes is 400-600mm; The jet velocity of the purge hole is 70-110m / s, and the total mass flow rate of the purge air system is controlled within the range of 4-6t / h by adjusting the opening of the electric slide gate; The diameter of the main purging air pipe, branch pipes and purging pipeline decreases step by step, and the air velocity in each section of the pipeline is 20-30m / s; The operating parameters provided by the hot primary air intake unit meet the requirements of a wind pressure of not less than 12 kPa and a temperature of not less than 300℃ under BMCR conditions.

3. The ash-blowing air system for the bottom of a power plant boiler wind box as described in claim 1, characterized in that, The air intake point of the hot primary air intake unit is located on the downstream main duct of the hot primary air behind the boiler, with two independent air intake interfaces symmetrically arranged on the left and right sides.

4. The ash-blowing air system for the bottom of the wind box of a power plant boiler as described in claim 1, characterized in that, The air box includes the burner air box and the burnout air box. The multi-level branch pipeline unit includes a two-level branch structure. The main pipeline branches into left and right branch pipes, and each branch pipe is further divided into burner air box branch pipe and burnout air box branch pipe.

5. The ash-blowing air system for the bottom of a power plant boiler wind box as described in claim 1, characterized in that, The vertical distance between the purging pipe of the bottom purging unit of the air box and the bottom plate of the air box is 400-600mm, and it is fixed to the bottom truss of the air box by a U-shaped bracket.

6. The ash-blowing air system for the bottom of a power plant boiler wind box as described in claim 1, characterized in that, The purge holes are arranged evenly along the axial direction of the purge pipe, with a center distance of 450-550mm between adjacent purge holes and a diameter of 8-12mm for each purge hole.

7. The ash-blowing air system for the bottom of a power plant boiler wind box as described in claim 1, characterized in that, An auxiliary purging branch pipe is added above the baffle in the burner air box area. The auxiliary purging branch pipe is connected to the main purging pipe in a T-shape.

8. The ash-blowing air system for the bottom of the wind box of a power plant boiler as described in claim 1, characterized in that, The electric slide gate and the manual flip gate are arranged in series, with the electric slide gate located upstream of the manual flip gate, and the distance between them is 1.5-2 times the pipe diameter.

9. The ash-blowing air system for the bottom of a power plant boiler wind box as described in claim 1, characterized in that, The purging pipe is made of high-temperature resistant alloy steel with a wall thickness of 6-8mm and an anti-oxidation treatment on the surface.

10. The ash-blowing air system for the bottom of a power plant boiler wind box as described in claim 1, characterized in that, The distribution header and branch pipes are connected by flanges, and the distribution header and purging pipes are fixed by welding.

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