A method and device for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers

Abstract

The present invention relates to the technical field of coal-fired boilers and provides a method and device for improving the steam oxidation resistance of small-diameter boiler tubes in coal-fired boilers. The method comprises the following steps: cutting the boiler tube panel from the boiler ceiling, then vertically hoisting and fixing it, and cutting a cross section from the bottom of the lower elbow of the boiler tube panel; cleaning the inner tube wall of each tube body in the boiler tube panel; sintering an anti-oxidation coating on the inner tube wall of each tube body in the boiler tube panel; and welding and repairing each tube body in the sintered boiler tube panel. All construction processes of this method can be completed in the furnace during shutdown and maintenance, with high production efficiency, which can significantly reduce the maintenance period. In addition, a steam oxidation resistance layer can be formed on the inner wall of the small-diameter boiler tube, which can significantly improve the steam oxidation resistance of the small-diameter boiler tubes in service coal-fired boilers.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-fired boilers, and in particular to a method and a device for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers. Background Art

[0002] Surface oxidation and corrosion of heat exchanger tubes in the high-temperature section of boilers have long plagued the safe operation of thermal power units. The resulting blockages and bursts account for a significant proportion of unplanned unit shutdowns. Furthermore, with the development of advanced supercritical thermal power technology operating at 630-700°C, the oxidation and corrosion of boiler heat exchanger tubes at higher steam parameters will become even more severe. Based on the characteristics and operating environments of thermal power unit boiler heat exchanger tubes, coating materials and corresponding preparation processes have been developed that can completely address the oxidation and corrosion issues. However, the most critical step in this preparation process is the need to heat treat the heat exchanger tubes to obtain an effective high-temperature oxidation and corrosion-resistant coating structure.

[0003] Existing boiler heat exchangers are constructed from single, small-diameter boiler tubes welded together. Heat treatment of these tubes requires disassembling them and cutting them into individual tubes before traditional heat treatment can be performed individually. This is not only costly and inefficient, but also requires re-welding, reassembling, and reinstalling the treated tubes. Numerous weld seams and defects pose significant risks to the tubes' subsequent use. Oxide scale on the steam side of thermal power plants has long been a major safety hazard, leading to boiler tube blockages and bursts. Data shows that tons of scale can detach from the steam pipes on the heating surface of a 600MW ultra-supercritical boiler. This scale can not only clog the superheater and reheater, potentially causing a burst, but can also be carried out of the boiler by high-velocity steam, damaging turbine blades. In ultra-supercritical thermal power plants, the components with the greatest protection requirements are primarily the small-diameter boiler tubes that transmit high-temperature, high-pressure steam. These tubes are used in large quantities and typically have a design lifespan of at least 20 years. For example, the boiler tubes of a 1000MW unit's superheater / reheater have an inner diameter of 20-50mm, a length of 8-12m, and a large number of panel elbows, using over 1000 tons. With the development of advanced ultra-supercritical thermal power technology at 630-700°C in the near future, the problem of oxide scale at higher steam parameters will become increasingly severe.

[0004] While techniques such as grain refinement, internal wall shot peening, and high-Cr alloying can rapidly grow the Cr2O3 film required for oxidation resistance in austenitic steel, Cr2O3 exhibits poor stability in steam temperatures above 600°C. This problem is exacerbated by the loosening of the oxide film caused by volatile products in units with oxygen treatment. With increasing service life, the alloy's oxidation resistance declines dramatically when the Cr content required for oxide film growth is not replenished. While 25% Cr austenitic steel offers excellent oxidation and corrosion resistance, its poor microstructural stability reduces the alloy's high-temperature endurance strength. Martensitic heat-resistant steel pipes face similar challenges in high-temperature service. After 1000 hours of thermal exposure to pure water vapor at 650°C and atmospheric pressure, the surface oxide scale of 9% Cr martensitic heat-resistant steel can reach a thickness of 200μm. The outer layer, a loose and porous Fe3O4 layer, is easily detached, significantly reducing the reliability of safe operation of 600°C ultra-supercritical thermal power units. Therefore, it is of great significance to improve the steam oxidation resistance of small-diameter boiler tubes for coal-fired boilers based on existing material selection. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is how to improve the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers based on existing material selection, thereby providing a method and device for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers.

[0006] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0007] A method for improving the steam oxidation resistance of small-diameter boiler tubes in a coal-fired boiler comprises the following steps: cutting a boiler tube panel from a boiler ceiling, then vertically hoisting and fixing it, and cutting a cross section from the bottom of a lower elbow of the boiler tube panel; cleaning the inner tube wall of each tube body in the boiler tube panel; sintering an anti-oxidation coating on the inner tube wall of each tube body in the boiler tube panel; and repairing each tube body in the sintered boiler tube panel by welding.

[0008] Furthermore, cleaning the inner tube wall of each tube body in the boiler tube panel specifically includes: using a sandblasting device to remove the oxide scale grown on the inner wall of each boiler tube in the service tube panel; wherein the sand material sprayed by the sandblasting device includes one or more of brown corundum, white corundum and quartz sand, and the particle size of the sand material is less than 500 mesh.

[0009] Furthermore, sintering the anti-oxidation coating on the inner tube wall of each tube body in the boiler tube panel specifically includes: using a spraying device to apply paint to the boiler tube after sandblasting cleaning; using a screen-type integral heating and curing sintering device to sinter the boiler tube after the paint is applied to form an anti-oxidation coating on the inner tube wall of the boiler tube; and using a sandblasting device to clean the residue of the boiler tube after sintering.

[0010] Furthermore, the coating is prepared using aluminum powder and nickel powder in a mass ratio of 1:1 as a penetrant, a phosphate aqueous solution as a solvent, CrO3 as an acid inhibitor, and MgO as a curing agent, and is prepared according to the ratio of 100g penetrant: 100ml phosphate aqueous solution: 10g acid inhibitor: 2g curing agent.

[0011] Furthermore, the coating is sprayed to a thickness of 0.2 mm to 0.3 mm.

[0012] A device for improving the steam oxidation resistance of small-diameter boiler tubes in coal-fired boilers, comprising at least: a sandblasting device suitable for removing oxide scale grown on the inner wall of each boiler tube in a service tube panel; a spraying device suitable for coating the boiler tubes after sandblasting; and a panel-type integral heating, curing and sintering device suitable for sintering the boiler tubes after coating to form an anti-oxidation coating on the inner tube wall of the boiler tube.

[0013] Furthermore, the sandblasting device includes a hollow motor, a first nozzle and a sand material tube; the hollow motor is connected to the first nozzle and is suitable for driving the first nozzle to rotate so that the sand material in the cavity of the first nozzle is ejected through the strip opening on the surface of the first nozzle; one end of the sand material tube passes through the hollow motor and extends into the cavity of the first nozzle, and the other end is suitable for being connected to an external sand material source.

[0014] Furthermore, the sandblasting device also includes a traction rope, one end of which is connected to the end of the hollow motor away from the first nozzle, and the other end is suitable for being connected to an external traction device, so that the external traction device drives the sandblasting device to move in the boiler tube through the traction rope.

[0015] Furthermore, an annular sealing ring is provided on the outer wall of the hollow motor and / or the first nozzle, and the outer diameter of the annular sealing ring is consistent with the inner diameter of the boiler tube.

[0016] Furthermore, the spraying device includes a connected driving mechanism and a spraying mechanism, wherein the driving mechanism is suitable for driving the spraying mechanism to move in the boiler tube, and the spraying mechanism is suitable for spraying the paint on the inner wall of the boiler tube.

[0017] Furthermore, the driving mechanism includes a first shell, a driving wheel and a power battery; a plurality of the driving wheels are arranged at intervals on the outer wall of the first shell along the circumferential direction of the first shell, and each of the driving wheels can be telescopically moved along the radial direction of the first shell; the power battery is arranged in the first shell and is electrically connected to each of the driving wheels, and is suitable for driving the driving wheels to rotate.

[0018] Furthermore, the spraying mechanism includes a second shell, a second nozzle, an air motor, an air pipe and a feeding pipe; the second shell is connected to the first shell, and the second nozzle is arranged at an end of the second shell away from the first shell; the air motor is arranged in the second shell, the air outlet of the air motor is connected to the air inlet of the second nozzle, and the air inlet of the air motor is connected to the external air source through the air pipe; one end of the feeding pipe is connected to the feed port of the second nozzle, and the other end is connected to an external paint source.

[0019] Furthermore, a plurality of positioning wheels are arranged at intervals on the outer wall of the second shell along the circumferential direction of the second shell, and each of the positioning wheels can telescopically move along the radial direction of the second shell.

[0020] Furthermore, the spraying device also includes a front camera, a rear camera and a thickness sensor suitable for monitoring the spraying process; the front camera is arranged at an end of the second shell away from the first shell; the rear camera is arranged at an end of the first shell away from the second shell; the thickness sensor is arranged at an end of the second shell away from the first shell.

[0021] Furthermore, the screen-type integral heating, curing and sintering device includes an air-cooled induction heating coil, a coil moving track, a crawler, an intelligent control cabinet and an induction coil power supply; one end of the coil moving track is suitable for being set on the boiler ceiling, and the other end extends vertically downward and exceeds the bottom of the boiler tube; the crawler is set on the inner side of the coil moving track, and the air-cooled induction heating coil is connected to the crawler; the induction coil power supply is electrically connected to the air-cooled induction heating coil; the intelligent control cabinet is electrically connected to the crawler, and the intelligent control cabinet controls the crawler to drive the air-cooled induction heating coil to move along the coil moving track to sinter the boiler tube located in the air-cooled induction heating coil.

[0022] Furthermore, the screen-type integral heating, curing and sintering device also includes a first limiter and a second limiter; the first limiter and the second limiter are arranged at intervals on the coil moving track to limit the starting and ending positions of the crawler on the coil moving track.

[0023] The technical solution of the present invention has the following advantages:

[0024] The present invention provides a method for improving the steam oxidation resistance of small-diameter boiler tubes in coal-fired boilers. The method involves first cutting the boiler tube panel from the boiler ceiling, then vertically hoisting and securing it, and cutting a cross section from the bottom of the lower elbow of the boiler tube panel. The inner wall of each tube body in the boiler tube panel is then cleaned. An anti-oxidation coating is then sintered onto the inner wall of each tube body in the boiler tube panel. Finally, each tube body in the sintered boiler tube panel is repaired by welding. This method, which can be completed entirely within the furnace during maintenance, offers high production efficiency and significantly reduces maintenance time. Furthermore, it forms an anti-steam oxidation layer on the inner wall of the small-diameter boiler tube, significantly improving the steam oxidation resistance of small-diameter boiler tubes in in-service coal-fired boilers. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 Schematic diagram of the overall structure of a device for improving the steam oxidation resistance of small-diameter boiler tubes of a coal-fired boiler in an embodiment of the present invention;

[0027] Figure 2 for Figure 1 Schematic diagram of the sandblasting device;

[0028] Figure 3 for Figure 2 sectional view of

[0029] Figure 4 for Figure 1 Schematic diagram of the spraying device;

[0030] Figure 5 for Figure 4 An enlarged schematic diagram of the middle drive wheel;

[0031] Figure 6 for Figure 4 An enlarged schematic diagram of the middle positioning wheel;

[0032] Figure 7 for Figure 1 Schematic diagram of the screen-type integral heating, curing and sintering device;

[0033] Figure 8 for Figure 7 Main view at the middle crawler;

[0034] Figure 9 for Figure 7 Top view at the middle crawler;

[0035] Figure 10 for Figure 7 Side view at the mid-crawler;

[0036] Figure 11 for Figure 7 Schematic diagram of the screen-type integral heating, curing and sintering device in working condition.

[0037] 10. Ceiling cut surface; 11. Inlet header; 12. Outlet header; 13. Lower elbow cut surface; 14. Tube screen; 15. Boiler ceiling; 21. Induction coil power supply; 22. Coil moving track; 23. Crawler; 24. Air-cooled induction heating coil; 25. Intelligent control cabinet; 31. Sandblasting device; 32. Sand storage tank; 33. Sand pipe; 41. Spraying device; 42. Paint storage tank; 43. Feed pipe; 44. Gas pipe;

[0038] 221, track slot; 222, track ball; 231, first stopper; 232, second stopper; 233, coil fixing bolt; 234, first wire entry hole; 235, second wire entry hole; 236, drive motor; 237, boss;

[0039] 311, hollow motor; 312, first nozzle; 313, first connector; 314, annular sealing ring; 315, strip opening; 316, traction rope; 317, wire; 321, first interface; 3131, first coupling; 3211, fastening nut;

[0040] 411. Driving mechanism; 412. Spraying mechanism; 413. Driving wheel; 414. First shell; 415. Rear camera; 416. Second connector; 417. Positioning wheel; 418. Second nozzle; 419. Pneumatic motor; 420. Front camera; 421. Second shell; 422. Second coupling; 423. Thickness sensor; 4131. First wheel; 4132. DC motor; 4133. Hydraulic telescopic rod; 4134. Hydraulic box; 4135. Power battery; 4171. Second wheel; 4172. Sliding rod; 4173. Sliding cavity; 4174. Compression spring; 4175. Partition. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0042] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0043] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0044] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] Figure 1 FIG. 1 is a schematic diagram of the overall structure of a device for improving the steam oxidation resistance of small-diameter boiler tubes of a coal-fired boiler in an embodiment of the present invention; FIG. Figure 1 As shown, in this embodiment, when the boiler tube panel is cut at the ceiling, the position of the ceiling cutting surface 10 and the position of the lower elbow cutting surface 13 are as shown in FIG. Figure 1 As shown, the boiler tube panel 14 is separated from the inlet header 11 and the outlet header 12, cut and separated at the lowest point of the lower elbow of the boiler tube panel 14, and the cut boiler tube panel 14 is suspended and fixed using a suspension device in the furnace.

[0046] In this embodiment, an induction coil power supply 21, a sand storage tank 32, and a paint storage tank 42 are placed on the boiler ceiling 15. The sand storage tank 32 is connected to the sandblasting device 31 through a sand pipe 33. The paint storage tank 42 can be connected to the spraying device 41 through a feeding pipe 43.

[0047] The sandblasting device 31 and the spraying device 41 in this embodiment can both be sent into the pipeline from the upper cutting surface of the boiler tube panel 14 for operation.

[0048] like Figure 1As shown, this embodiment provides a device for improving the steam oxidation resistance of small-diameter boiler tubes of a coal-fired boiler, which at least includes: a sandblasting device 31, suitable for removing oxide scale grown on the inner wall of each boiler tube in the service tube panel 14; a spraying device 41, suitable for coating the boiler tube after sandblasting; and a panel-type integral heating, curing and sintering device, suitable for sintering the boiler tube after coating to form an anti-oxidation coating on the inner tube wall of the boiler tube.

[0049] The device for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers provided in this embodiment can first remove the oxide scale grown on the inner wall of each boiler tube in the service tube panel 14 by a sandblasting device 31; then, the sandblasted boiler tubes can be coated with paint by a spraying device 41; finally, the coated boiler tubes can be sintered by a screen-type integral heating and curing sintering device to form an anti-oxidation coating on the inner tube wall of the boiler tube, which can significantly improve the steam oxidation resistance of the small-diameter boiler tubes of the in-service coal-fired boilers.

[0050] Figure 2 for Figure 1 Schematic diagram of the sandblasting device; Figure 3 for Figure 2 A cross-sectional view of Figure 2 and Figure 3 As shown, the sandblasting device 31 includes a hollow motor 311, a first nozzle 312 and an abrasive material tube 33; the hollow motor 311 is connected to the first nozzle 312, and is suitable for driving the first nozzle 312 to rotate so that the abrasive material in the cavity of the first nozzle 312 is ejected through the strip opening 315 on the surface of the first nozzle 312; one end of the abrasive material tube 33 passes through the hollow motor 311 and extends into the cavity of the first nozzle 312, and the other end is suitable for being connected to an external abrasive material source.

[0051] The sandblasting device 31 also includes a traction rope 316, one end of the traction rope 316 is connected to the end of the hollow motor 311 away from the first nozzle 312, and the other end is suitable for being connected to an external traction device so that the external traction device drives the sandblasting device 31 to move in the boiler tube through the traction rope 316.

[0052] The outer wall of the hollow motor 311 and / or the first nozzle 312 is provided with an annular sealing ring 314 , and the outer diameter of the annular sealing ring 314 is consistent with the inner diameter of the boiler tube.

[0053] Specifically, the hollow motor 311 is located at the rear end of the entire sandblasting device 31 and is connected to an external power source via a wire 317. It is also connected to an external traction device via a traction rope 316. The first nozzle 312 is mounted at the front end of the sandblasting device 31 and is coaxially connected in series with the hollow motor 311 via a first connector 313 and a first coupling 3131. The axes of the two components are aligned after the connection. The abrasive tube 33 passes through the interior of the hollow motor 311 and the first nozzle 312. The axis of the abrasive tube 33 is fixed by a fastening nut 3211. A first interface 321 can be provided at the rear end of the abrasive tube 33 for connection to the external abrasive storage tank 32.

[0054] The hollow motor 311 can be powered by direct current, with a wire 317 connected to an external power source. A first coupling 3131 is installed within the hollow motor 311, connecting the hollow motor 311 to the first nozzle 312. Rotation of the hollow motor 311 drives the first nozzle 312 to rotate at high speed, with the no-load speed exceeding 30,000 rpm. The head of the first nozzle 312 can have a conical structure with a plurality of strip-shaped openings 315 defined on the conical surface. The centrifugal force generated by the high-speed rotation of the first nozzle 312 ejects abrasive material from the strip-shaped openings 315 onto the inner wall of the boiler tube. The connection between the first nozzle 312 and the hollow motor 311 can be a cylindrical hollow housing, which, on the one hand, provides a coaxial connection with the hollow motor 311; on the other hand, the hollow structure of the first nozzle 312 allows a small amount of abrasive material to be stored within the cavity, ensuring continuous sandblasting even with an unstable abrasive material supply. An annular sealing ring 314 of equal diameter is installed on the outside of the hollow motor 311 and the first nozzle 312. By adjusting the diameter of the annular sealing ring 314, a tight fit with the inner wall of the boiler tube is achieved to ensure that the entire sandblasting device 31 is always located in the center of the pipeline during movement.

[0055] In order to ensure the quality of sandblasting, the sandblasting device 31 operates in a reverse spraying mode during use. Before the sandblasting operation, the diameter of the annular sealing ring 314 is adjusted, the sandblasting device 31 is placed in the inner cavity of the boiler tube to be sandblasted, and the sandblasting device 31 is moved to the front end of the boiler tube to be sandblasted. After connecting the external sand storage tank 32, the traction device, and the power supply for the hollow motor 311, the sandblasting operation speed is adjusted by controlling the operating speed of the external traction device. The sand used in the sandblasting device 31 can be a variety of sandblasting materials such as corundum sand and quartz sand, and the sand particle size should be less than 500 mesh.

[0056] Figure 4 for Figure 1 Schematic diagram of the spraying device; Figure 5 for Figure 4 An enlarged schematic diagram of the middle drive wheel; Figure 6 for Figure 4An enlarged schematic diagram of the middle positioning wheel; Figure 4 、 Figure 5 as well as Figure 6 As shown, the spraying device 41 includes a connected driving mechanism 411 and a spraying mechanism 412, the driving mechanism 411 is suitable for driving the spraying mechanism 412 to move in the boiler tube, and the spraying mechanism 412 is suitable for spraying the paint on the inner wall of the boiler tube.

[0057] Among them, the driving mechanism 411 includes a first shell 414, a driving wheel 413 and a power battery 4135; a plurality of driving wheels 413 are arranged at intervals on the outer wall of the first shell 414 along the circumferential direction of the first shell 414, and each driving wheel 413 can be telescopically moved along the radial direction of the first shell 414; the power battery 4135 is arranged in the first shell 414 and is electrically connected to each driving wheel 413, suitable for driving the driving wheel 413 to rotate.

[0058] Among them, the spraying mechanism 412 includes a second shell 421, a second nozzle 418, an air motor 419, an air circuit pipe 44 and a feeding pipe 43; the second shell 421 is connected to the first shell 414, and the second nozzle 418 is arranged at one end of the second shell 421 away from the first shell 414; the air motor 419 is arranged in the second shell 421, and the air outlet of the air motor 419 is connected to the air inlet of the second nozzle 418, and the air inlet of the air motor 419 is connected to the external air source through the air circuit pipe 44; one end of the feeding pipe 43 is connected to the feed port of the second nozzle 418, and the other end is connected to the external paint source.

[0059] A plurality of positioning wheels 417 are arranged at intervals on the outer wall of the second shell 421 along the circumferential direction of the second shell 421 , and each positioning wheel 417 can telescopically move along the radial direction of the second shell 421 .

[0060] Among them, the spraying device 41 also includes a front camera 420, a rear camera 415 and a thickness sensor 423 suitable for monitoring the spraying process; the front camera 420 is arranged at an end of the second shell 421 away from the first shell 414; the rear camera 415 is arranged at an end of the first shell 414 away from the second shell 421; the thickness sensor 423 is arranged at an end of the second shell 421 away from the first shell 414.

[0061] Specifically, the spraying device 41 mainly consists of a drive mechanism 411 and a spraying mechanism 412. The arrow indicates the rear end of the spraying device 41. The drive mechanism 411 is located at the rear end of the spraying device 41 and is used to provide forward and reverse power. The drive mechanism 411 includes a first housing 414, four cross-distributed drive wheels 413 mounted on the first housing 414, and a power battery 4135 within the first housing 414.

[0062] The spraying mechanism 412 is installed at the front end of the spraying device 41 and is used to spray paint on the inner wall of the boiler tube. The spraying mechanism 412 has a second shell 421, four cross-distributed positioning wheels 417 installed on the second shell 421, an air motor 419 arranged in the second shell 421, a second nozzle 418 arranged outside the second shell 421, and a front camera 420, a rear camera 415 and a thickness sensor 423 for monitoring the spraying process.

[0063] The driving mechanism 411 and the spraying mechanism 412 in the spraying device 41 can be connected in series using a second connector 416, and the axes of the two parts are kept consistent after the connection. The spray paint required during use can be provided by the paint storage tank 42, and the selected carrier gas can be provided by an external air compressor.

[0064] The air pipe 44 passes through the first housing 414 and the second housing 421 and is connected to the air pipe 44 interface of the pneumatic motor 419. The feed pipe 43 passes through the first housing 414 and the second housing 421 and is connected to the feed pipe 43 interface of the second nozzle 418.

[0065] The drive wheels 413 are equipped with hydraulic telescopic rods 4133 that connect the first wheel 4131 to the first housing 414. A miniature hydraulic tank 4134 is located at the bottom of the drive wheels 413 to provide the required pressure for the hydraulic telescopic rods 4133. The four sets of drive wheels 413 are arranged in a cross pattern and have the same structure. The power battery 4135 is centrally located within the first housing 414, with space reserved for the air pipe 44 and the feed pipe 43 to pass through.

[0066] Among them, the positioning wheel 417 is used to ensure that the axes of the driving mechanism 411 and the spraying mechanism 412 are aligned. It does not have a power function to reduce unnecessary control units and connection lines. The positioning wheel 417 is composed of a second wheel 4171, a sliding cavity 4173, a sliding rod 4172 built into the sliding cavity 4173, a compression spring 4174 and a partition 4175. When an external force squeezes the second wheel 4171, the compression spring 4174 contracts and deforms, and the elastic force is transmitted through the sliding rod 4172, fixing the second wheel 4171 to the inner wall of the boiler tube. Among them, the four groups of positioning wheels 417 are arranged in a cross shape and have the same structure. The pneumatic motor 419 is centrally placed inside the second shell 421, and a space is reserved between the second shell 421 and the pneumatic motor 419 for the feeding pipe 43 to pass through; an air pipe 44 interface is provided at the tail of the pneumatic motor 419 for connecting the air pipe 44, and a second coupling 422 is installed on the top for connecting the second nozzle 418. The second nozzle 418 has a strip-shaped opening, and the centrifugal force generated by high-speed rotation sprays the paint from the strip-shaped opening onto the inner wall of the boiler tube.

[0067] To ensure the quality of the sprayed coating, the spraying device 41 operates in a reverse spraying mode. Before spraying, adjust the extension length of the hydraulic telescopic rod 4133 and the sliding rod 4172, position the spraying device 41 within the inner cavity of the boiler tube to be sprayed, connect the external air compressor and the paint storage tank 42, activate the power battery 4135 to power the DC motor 4132 of the four drive wheels 413, and move the spraying device 41 to the front end of the boiler tube to be sprayed. Then, activate the front camera 420, rear camera 415, and thickness sensor 423 to monitor the coating process.

[0068] Figure 7 for Figure 1 Schematic diagram of the screen-type integral heating, curing and sintering device; Figure 8 for Figure 7 Main view at the middle crawler; Figure 9 for Figure 7 Top view at the middle crawler; Figure 10 for Figure 7 Side view at the mid-crawler; Figure 11 for Figure 7 Schematic diagram of the screen-type integral heating and curing sintering device in working state; Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 as well as Figure 11 As shown, the screen-type integral heating, curing and sintering device includes an air-cooled induction heating coil 24, a coil moving track 22, a crawler 23, an intelligent control cabinet 25 and an induction coil power supply 21; one end of the coil moving track 22 is suitable for being set on the boiler ceiling 15, and the other end extends vertically downward and exceeds the bottom of the boiler tube; the crawler 23 is set on the inner side of the coil moving track 22, and the air-cooled induction heating coil 24 is connected to the crawler 23; the induction coil power supply 21 is electrically connected to the air-cooled induction heating coil 24; the intelligent control cabinet 25 is electrically connected to the crawler 23, and the intelligent control cabinet 25 controls the crawler 23 to drive the air-cooled induction heating coil 24 to move along the coil moving track 22 to sinter the boiler tube located in the air-cooled induction heating coil 24.

[0069] Among them, the screen-type integral heating, curing and sintering device also includes a first limiter 231 and a second limiter 232; the first limiter 231 and the second limiter 232 are arranged at intervals on the coil moving track 22 to limit the starting and ending positions of the crawler 23 on the coil moving track 22.

[0070] Specifically, the air-cooled induction heating coil 24 is fixed at both ends to the crawler 23, which is installed on the inner side of the coil moving track 22. The intelligent control cabinet 25 is electrically connected to the crawler 23, and the induction coil power supply 21 is connected to the air-cooled induction heating coil 24 through the crawler 23. The upper end of the coil moving track 22 is fixed to the boiler ceiling 15, and the lower section is vertically suspended below the bottom of the boiler tube. The coil moving track 22 is usually used in pairs. A first limiter 231 and a second limiter 232 are arranged at intervals on the coil moving track 22. The first limiter 231 can be arranged 0.3m below the boiler ceiling 15, and the second limiter 232 can be arranged 0.5m below the bottom of the boiler tube. They are used to automatically locate the starting and ending positions of the crawler 23. The crawler 23 is located between the first limiter 231 and the second limiter 232, and keeps both ends horizontal.

[0071] The coil moving track 22 is provided with a track slot 221, embedded with a track ball 222 that can roll 360°. The crawler 23 includes a coil fixing bolt 233, a drive motor 236, a boss 237, a second wire entry hole 235, and a first wire entry hole 234. The crawler 23 is connected to the coil moving track 22 via the boss 237 and the track slot 221. The track ball 222 is used to reduce the crawling resistance of the crawler 23, and the drive motor 236 provides the crawling force. The forward and reverse rotation of the drive motor 236 enables the crawler 23 to crawl up and down. Before heat treatment of the boiler tubes, the system is constructed and installed. Among them, large auxiliary equipment such as the induction coil power supply 21 and the intelligent control cabinet 25 are arranged above the entire heating system and fixed on the boiler ceiling 15. The remaining components are arranged in a longitudinal vertical downward manner. The span size of the air-cooled induction heating coil 24 can be flexibly changed according to the size of the boiler tube panel 14 and is not restricted by the size of the boiler tube panel 14 and other workpieces.

[0072] As one of the preferred methods of this embodiment, the crawler 23 is adjusted by the intelligent control cabinet 25 so that the crawler 23 is located at the first limiter 231. According to the heat treatment temperature required by the boiler tube, the size of the boiler tube and other information, the power, operating speed and operating time required by the air-cooled induction heating coil 24 are set. The operation button of the intelligent control cabinet 25 is started. Under the regulation of the PLC in the intelligent control cabinet 25, the crawler 23 starts to crawl from top to bottom driven by the drive motor 236. When it passes the first limiter 231, the induction The coil power supply 21 is automatically turned on, and the air-cooled induction heating coil 24 begins to automatically perform chemical heat treatment on the tube panel 14 formed by the boiler tubes. At the same time, it continues to crawl downward with the crawler 23. After the heat treatment of the entire tube panel 14 is completed and reaches the second limiter 232, the intelligent control cabinet 25 sends a signal, the induction coil power supply 21 is automatically turned off, the induction heating stops, and the crawler 23 starts to crawl from bottom to top under the reverse rotation of the drive motor 236 until it returns to its initial position. The intelligent control cabinet 25 stops working, and the heat treatment process of the tube panel 14 is completed.

[0073] Another embodiment provides a method for improving the steam oxidation resistance of small-diameter boiler tubes in a coal-fired boiler, comprising the following steps: cutting the boiler tube panel 14 from the boiler ceiling 15, then vertically hoisting and fixing it, and cutting a cross section from the bottom of the lower elbow of the boiler tube panel 14; cleaning the inner tube wall of each tube body in the boiler tube panel 14; sintering an anti-oxidation coating on the inner tube wall of each tube body in the boiler tube panel 14; and welding and repairing each tube body in the sintered boiler tube panel 14.

[0074] This embodiment provides a method for improving the steam oxidation resistance of small-diameter boiler tubes in coal-fired boilers. The method involves first cutting the boiler tube panel 14 from the boiler ceiling 15, then vertically hoisting and securing it, and cutting a cross section from the bottom of the lower elbow of the boiler tube panel 14. The inner tube wall of each tube body in the boiler tube panel 14 is then cleaned. An anti-oxidation coating is then sintered onto the inner tube wall of each tube body in the boiler tube panel 14. Finally, each tube body in the sintered boiler tube panel 14 is repaired by welding. This method, which can be completed entirely within the furnace during shutdown and maintenance, offers high production efficiency and can significantly reduce maintenance time. Furthermore, it forms an anti-steam oxidation layer on the inner wall of the small-diameter boiler tubes, significantly improving the steam oxidation resistance of small-diameter boiler tubes in in-service coal-fired boilers.

[0075] The cleaning of the inner tube wall of each tube body in the boiler tube panel 14 specifically includes: using a sandblasting device 31 to remove the oxide scale grown on the inner wall of each boiler tube in the service tube panel 14; wherein the sand material sprayed by the sandblasting device 31 includes one or more of brown corundum, white corundum and quartz sand, and the particle size of the sand material is less than 500 mesh.

[0076] The sintering of the anti-oxidation coating on the inner wall of each tube in the boiler tube panel 14 specifically includes: coating the boiler tubes after sandblasting using a spraying device 41; sintering the coated boiler tubes using a panel-type integral heating and curing sintering device to form an anti-oxidation coating on the inner wall of the boiler tubes. The sintering temperature can be 800-900°C, and the holding time is controlled to be 10-15 minutes. After sintering, the sandblasting device 31 is used to clean the boiler tubes of any residue.

[0077] Among them, the coating is prepared using aluminum powder and nickel powder in a mass ratio of 1:1 as a penetrant, phosphate aqueous solution as a solvent, CrO3 as an acid inhibitor, and MgO as a curing agent, and is prepared according to the ratio of 100g penetrant: 100ml phosphate aqueous solution: 10g acid inhibitor: 2g curing agent.

[0078] Preferably, the spraying thickness of the coating is 0.2mm-0.3mm.

[0079] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers, characterized in that: The method comprises the following steps: Cut the boiler tube panel from the boiler ceiling, then vertically hoist and fix it, and cut the section from the bottom of the lower elbow of the boiler tube panel; Place the sandblasting device in the inner cavity of the boiler tube to be sandblasted, and move the sandblasting device to the front end of the boiler tube to be sandblasted to clean the inner tube wall of each tube body in the boiler tube panel; Sintering the anti-oxidation coating on the inner wall of each tube body in the boiler tube panel; Welding repair is performed on each tube body in the sintered boiler tube panel; Cleaning the inner wall of each tube in the boiler tube panel specifically includes: Use sandblasting equipment to remove the oxide scale grown on the inner wall of each boiler tube in the service tube panel; The sand material sprayed by the sand blasting device includes one or more of brown corundum, white corundum and quartz sand, and the particle size of the sand material is less than 500 mesh; Sintering the anti-oxidation coating on the inner wall of each tube body in the boiler tube panel specifically includes: The spraying device moves to the front end of the boiler tube to be sprayed, and the paint is applied to the boiler tube after sandblasting by reverse spraying, while the coating process is monitored. The paint is prepared using aluminum powder and nickel powder in a mass ratio of 1:1 as a penetrant, a phosphate aqueous solution as a solvent, CrO3 as an acid inhibitor, and MgO as a curing agent. The boiler tube coated with the coating is sintered using a screen-type integral heating and curing sintering device to form an anti-oxidation coating on the inner tube wall of the boiler tube; A sandblasting device is used to clean the residue of the sintered boiler tubes.

2. The method for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers according to claim 1, characterized in that: The sandblasting device is suitable for removing the oxide scale grown on the inner wall of each boiler tube in the service tube panel: The spraying device is suitable for coating the boiler tube after sandblasting; The screen-type integral heating and curing sintering device is suitable for sintering the boiler tube coated with paint to form an anti-oxidation coating on the inner tube wall of the boiler tube; The sandblasting device includes a hollow motor, a first nozzle and a sand material pipe; The hollow motor is connected to the first nozzle and is suitable for driving the first nozzle to rotate so that the sand material in the cavity of the first nozzle is ejected through the strip-shaped opening on the surface of the first nozzle; One end of the abrasive material tube passes through the hollow motor and extends into the cavity of the first nozzle, and the other end is suitable for being connected to an external abrasive material source; The head of the first nozzle is a conical structure, and the conical surface is provided with a plurality of strip-shaped openings. The connecting section between the first nozzle and the hollow motor is a cylindrical hollow shell. The first nozzle is coaxially connected to the hollow motor, and the hollow structure of the first nozzle can store sand in the cavity; The screen-type integral heating, curing and sintering device includes an air-cooled induction heating coil, a coil moving track, a crawler, an intelligent control cabinet and an induction coil power supply; One end of the coil moving track is adapted to be positioned on the boiler ceiling, and the other end extends vertically downward and beyond the bottom of the boiler tube; The crawler is arranged on the inner side of the coil moving track, and the air-cooled induction heating coil is connected to the crawler; The induction coil power supply is electrically connected to the air-cooled induction heating coil; The intelligent control cabinet is electrically connected to the crawler, and the intelligent control cabinet controls the crawler to drive the air-cooled induction heating coil to move along the coil moving track to sinter the boiler tube located in the air-cooled induction heating coil.

3. The method for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers according to claim 1, characterized in that: The coating is prepared by mixing 100 g of penetrant, 100 ml of phosphate aqueous solution, 10 g of acid inhibitor, and 2 g of curing agent.

4. The method for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers according to claim 1, characterized in that: The spraying thickness of the paint is 0.2mm-0.3mm.

5. The method for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers according to claim 2, characterized in that: The sandblasting device also includes a traction rope, one end of which is connected to the end of the hollow motor away from the first nozzle, and the other end is suitable for being connected to an external traction device, so that the external traction device drives the sandblasting device to move in the boiler tube through the traction rope.

6. The method for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers according to claim 2, characterized in that: An annular sealing ring is provided on the outer wall of the hollow motor and / or the first nozzle, and the outer diameter of the annular sealing ring is consistent with the inner diameter of the boiler tube.

7. The method for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers according to claim 2, characterized in that: The spraying device comprises a driving mechanism and a spraying mechanism connected to each other. The driving mechanism is suitable for driving the spraying mechanism to move in the boiler tube, and the spraying mechanism is suitable for spraying the paint on the inner wall of the boiler tube.

8. The method for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers according to claim 7, characterized in that: The driving mechanism includes a first housing, a driving wheel and a power battery; A plurality of driving wheels are arranged at intervals on the outer wall of the first shell along the circumferential direction of the first shell, and each of the driving wheels can telescopically move along the radial direction of the first shell; The power battery is disposed in the first housing and is electrically connected to each of the driving wheels, and is suitable for driving the driving wheels to rotate.

9. The method for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers according to claim 8, characterized in that: The spraying mechanism includes a second shell, a second nozzle, a pneumatic motor, an air pipe and a feeding pipe; The second shell is connected to the first shell, and the second nozzle is arranged at an end of the second shell away from the first shell; The pneumatic motor is arranged in the second housing, the air outlet of the pneumatic motor is connected to the air inlet of the second nozzle, and the air inlet of the pneumatic motor is connected to an external air source through an air pipe; One end of the feeding pipe is connected to the feeding port of the second nozzle, and the other end is connected to an external coating source.

10. The method for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers according to claim 9, characterized in that: A plurality of positioning wheels are arranged at intervals on the outer wall of the second shell along the circumferential direction of the second shell, and each of the positioning wheels can telescopically move along the radial direction of the second shell.

11. The method for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers according to claim 9, characterized in that: The spraying device also includes a front camera, a rear camera and a thickness sensor suitable for monitoring the spraying process; The front camera is arranged at an end of the second housing away from the first housing; The rear camera is arranged at an end of the first housing away from the second housing; The thickness sensor is arranged at an end of the second housing away from the first housing.

12. The method for improving the steam oxidation resistance of small-diameter boiler tubes of coal-fired boilers according to claim 11, characterized in that: The screen-type integral heating, curing and sintering device further includes a first stopper and a second stopper; The first limiter and the second limiter are arranged on the coil moving track at intervals to limit the running starting point and ending point of the crawler on the coil moving track.

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