Method and apparatus for improving steam oxidation resistance of small diameter boiler tubes in coal-fired boilers

Abstract

This application 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 of coal-fired boilers. The method includes the steps of cutting the tube panel of the boiler from the boiler ceiling, then vertically lifting and fixing it, and cutting the cross section at the bottom of the lower bend of the tube panel of the boiler, cleaning the inner tube wall of each tube body in the tube panel of the boiler, sintering an oxidation-resistant coating on the inner tube wall of each tube body in the tube panel of the boiler, and welding and repairing each tube body after sintering in the tube panel of the boiler. All the steps of the method can be carried out in the furnace during the period when the furnace is stopped for inspection, so that the production efficiency is high, the inspection period can be significantly shortened, and a steam oxidation prevention layer can be formed on the inner wall of the small-diameter boiler tube, and the steam oxidation resistance of the small-diameter boiler tube of the coal-fired boiler during use can be greatly improved.

Description

[Technical field]

[0001] This application claims priority to a Chinese patent application, Application No. 202211325248.6, entitled "Method and Apparatus for Improving the Steam Oxidation Resistance of Small Diameter Boiler Tubes of Coal-Fired Boilers", filed with the China Patent Office on October 27, 2022, the entire contents of which are incorporated herein by reference. This application relates to the technical field of coal-fired boilers, and more particularly to a method and apparatus for improving the steam oxidation resistance of small diameter boiler tubes of coal-fired boilers. [Background technology]

[0002] The surface oxidation and corrosion of the heat exchanger tubes in the high temperature section of the boiler has hindered thermal power generation units for many years, and the accidents of pipe clogging and pipe bursting account for a large part of unplanned equipment shutdowns. In addition, with the development of advanced supercritical thermal power generation technology at 630-700°C, the problem of oxidation corrosion of the heat exchanger tubes of the boiler at higher steam parameters becomes more serious. In view of the characteristics and use environment of the heat exchanger tubes of the boiler of the thermal power generation unit, a coating material and a corresponding manufacturing process have been developed at present, which can completely solve the problem of oxidation corrosion of the heat exchanger tubes. However, the most important step of the manufacturing process is to carry out the corresponding heat treatment on the heat exchanger tubes, otherwise it is impossible to obtain an effective coating structure that can withstand high temperature oxidation corrosion.

[0003] In the prior art, all the boiler heat exchangers are made of single small diameter boiler tubes welded together. To heat treat the heat exchanger tubes, all the pipes must be removed and cut into individual tubes, which cannot be done one by one using the traditional heat treatment method. This is not only expensive and inefficient, but also requires re-welding, reassembly and re-arrangement of the pipes after heat treatment, and many weld seams and defects will cause potential safety hazards when the heat exchanger tubes are reused. The problem of oxide film on the steam side of a thermal power generation unit is a major potential safety hazard that can cause accidents such as boiler pipe clogging and pipe rupture. Data shows that the amount of peeled oxide film in the steam pipes on the heat transfer surface of a 600MW ultra-supercritical boiler can reach several tons. These oxide films not only block the over / reheater and cause pipe rupture accidents, but also are carried out of the boiler by the high-velocity steam, causing damage to the blades of the steam turbine. In ultra-supercritical thermal power generation units, the components that need protection the most are mainly small diameter boiler tubes that deliver high temperature and high pressure steam, which are used in large quantities and have a design life of generally more than 20 years. For example, the superheater of a 1000MW unit has a boiler tube with an inner diameter of 20-50mm, a length of 8-12m, a large number of bends in the tube panel, and a usage of more than 1000 tons. With the development of advanced ultra-supercritical thermal power generation technology at 630-700℃ in the near future, the problem of oxide film at higher steam parameters will become increasingly serious.

[0004] Techniques such as grain refinement, shot blasting of the inner wall and high Cr alloying can rapidly grow the Cr2O3 film required for oxidation resistance on austenitic steel, but the stability of Cr2O3 in steam above 600℃ is relatively low, which aggravates the problem that the oxide film caused by volatile products is easily peeled off in oxygen-added units. As the service time increases, if the Cr required to grow the oxide film is not replenished, the oxidation resistance of the alloy will also rapidly decrease. 25% Cr-based austenitic steel has excellent oxidation resistance and corrosion resistance, but its low structural stability reduces the high-temperature endurance strength of the alloy. Martensitic heat-resistant steel tubes also face the same problem when used in high-temperature regions: when 9%Cr martensitic heat-resistant steel is exposed to 650℃ and normal pressure pure steam for 1000 hours, the thickness of the surface oxide film reaches 200μm, and the outer layer is a porous Fe3O4 layer that easily falls off, which significantly reduces the reliability of safe operation of 600℃ ultra-supercritical thermal power generation units. For this reason, it is very important to improve the steam oxidation resistance of small diameter boiler tubes for coal-fired boilers based on conventionally used materials. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, the technical problem to be solved by this application is to provide a method and an apparatus for improving the steam oxidation resistance of a small-diameter boiler tube of a coal-fired boiler by improving the steam oxidation resistance of the small-diameter boiler tube of a coal-fired boiler based on materials that have been conventionally used. [Means for solving the problem]

[0006] In order to solve the above technical problems, the technical proposal of the present application is as follows:

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

[0008] Optionally, when cleaning the inner tube wall of each tube body in the tube panel of the boiler, the method specifically includes removing an oxide film grown on the inner wall of each boiler tube in the tube panel in use by a sandblasting device, and the sand material ejected from the sandblasting device includes one or more of brown fused alumina, white fused alumina and quartz sand, and the grain size of the sand material is smaller than 500 mesh.

[0009] Optionally, sintering the antioxidant coating on the inner tube wall of each tube body in the tube panel of the boiler specifically includes: applying paint to the boiler tube after sandblasting cleaning by a spraying device; sintering the boiler tube with the paint applied by a screen-type whole heating hardening sintering device to form an antioxidant coating on the inner tube wall of the boiler tube; and cleaning residues from the boiler tube after sintering by a sandblasting device.

[0010] Optionally, in the preparation of the coating material, aluminum powder and nickel powder in a mass ratio of 1:1 are used as the penetrant, phosphate aqueous solution is used as the solvent, CrO3 is used as the acid inhibitor, and MgO is used as the hardener, and the ratio is prepared as follows: penetrant 100g:phosphate aqueous solution 100ml:acid inhibitor 10g:hardener 2g.

[0011] Optionally, the paint spray thickness is 0.2mm~0.3mm.

[0012] An apparatus for improving the steam oxidation resistance of small-diameter boiler tubes of a coal-fired boiler includes at least a sandblasting device configured to remove an oxide film grown on the inner wall of each boiler tube in a tube panel in use, a spraying device configured to apply paint to the boiler tube after sandblasting cleaning, and a screen-type overall heat-hardening and sintering device configured to sinter the boiler tube with the paint applied thereto, thereby forming an oxidation-resistant coating on the inner tube wall of the boiler tube.

[0013] Optionally, the sandblasting apparatus comprises a hollow motor, a first nozzle and a sand transport pipe, the hollow motor is connected to the first nozzle and configured to drive and rotate the first nozzle to eject sand material in the chamber of the first nozzle from a band-shaped opening on the surface of the first nozzle, and the sand transport pipe is configured such that one end extends through the hollow motor into the chamber of the first nozzle and the other end is connected to an external sand source.

[0014] Optionally, the sandblasting apparatus further comprises a towing rope, one end of which is connected to an end of the hollow motor remote from the first nozzle and the other end of which is configured to be connected to an external towing device, whereby the external towing device drives the sandblasting apparatus via the towing rope to move it within the boiler tube.

[0015] Optionally, an annular sealing ring is fitted to an outer wall of the hollow motor and / or the first nozzle, and an outer diameter of the annular sealing ring is held to match an inner diameter of a boiler tube.

[0016] Optionally, the spraying device comprises a drive mechanism and a spraying mechanism connected to each other, the drive mechanism configured to drive the spraying mechanism to move within the boiler tube, and the spraying mechanism configured to spray paint onto an inner wall of the boiler tube.

[0017] Optionally, the drive mechanism comprises a first case, a drive wheel, and a power battery, a plurality of the drive wheels are installed on the outer wall of the first case at intervals along the circumferential direction of the first case, and each of the drive wheels is capable of extending and retracting along the radial direction of the first case, and the power battery is installed within the first case and electrically connected to each of the drive wheels and configured to drive and rotate the drive wheels.

[0018] Optionally, the spray mechanism comprises a second case, a second nozzle, an air motor, a gas conveying pipe and a material supply pipe, the second case is connected to the first case, the second nozzle is installed at an end of the second case remote from the first case, the air motor is installed in the second case, its exhaust port is connected to the intake port of the second nozzle, the intake port is connected to an external gas source via the gas conveying pipe, and the material supply pipe has one end connected to the material supply port of the second nozzle and the other end connected to an external paint source.

[0019] Optionally, a plurality of positioning rings are installed on an outer wall of the second case at intervals along a circumferential direction of the second case, and each of the positioning rings is extendable and retractable along a radial direction of the second case.

[0020] Optionally, the spraying device further comprises an in-camera, an out-camera and a thickness sensor configured to monitor the spraying process, the in-camera being installed at an end of the second case remote from the first case, the out-camera being installed at an end of the first case remote from the second case, and the thickness sensor being installed at an end of the second case remote from the first case.

[0021] Optionally, the screen-type whole heating hardening sintering apparatus includes an air-cooled induction heating coil, a coil moving track, a crawler, an intelligent control cabinet, and an induction coil power supply, wherein the coil moving track has one end configured to be installed on the boiler ceiling and the other end extending vertically downward beyond the bottom of the boiler tube, the crawler is installed inside the coil moving track, 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, and the intelligent control cabinet is electrically connected to the crawler, and controls the crawler to drive the air-cooled induction heating coil to move along the coil moving track, thereby sintering the boiler tube located in the air-cooled induction heating coil.

[0022] Optionally, the screen-type whole heating hardening sintering device further comprises a first stopper and a second stopper, the first stopper and the second stopper being installed at an interval on the coil movement track to limit the start position and the end position of the crawler's movement on the coil movement track. Effect of the Invention

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

[0024] In the method for improving the steam oxidation resistance of the small diameter boiler tube of the coal-fired boiler according to the present invention, the boiler tube panel is first cut from the boiler ceiling, then vertically lifted and fixed, and the cross section is cut at the bottom of the lower bend of the boiler tube panel, then the inner tube wall of each tube body in the boiler tube panel is cleaned, then an oxidation-resistant coating is sintered on the inner tube wall of each tube body in the boiler tube panel, and finally, the sintered tube bodies in the boiler tube panel are welded and repaired. All the steps of the method can be carried out in the furnace during the period when the furnace is stopped for inspection, so that the production efficiency is high, the inspection period can be significantly shortened, and a steam oxidation-resistant layer can be formed on the inner wall of the small diameter boiler tube, and the steam oxidation resistance of the small diameter boiler tube of the coal-fired boiler during use can be greatly improved.

[0025] In order to more clearly describe the specific embodiments of the present application or the technical solutions of the prior art, the following briefly describes the drawings necessary for describing the specific embodiments or the prior art. Obviously, the drawings described below are only examples of the embodiments of the present application, and those skilled in the art can further obtain other drawings based on these drawings without any creative efforts. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a schematic diagram of the overall structure of an apparatus for improving the steam oxidation resistance of a small-diameter boiler tube of a coal-fired boiler according to an embodiment of the present application. [Diagram 2] FIG. 2 is a schematic diagram of the sandblasting device in FIG. [Diagram 3] FIG. 3 is a cross-sectional view of FIG. [Figure 4] FIG. 4 is a schematic diagram of the spraying device in FIG. [Diagram 5] FIG. 5 is an enlarged schematic view of the driving wheel in FIG. [Figure 6] FIG. 6 is an enlarged schematic view of the positioning ring in FIG. [Figure 7]FIG. 7 is a schematic diagram of the screen-type overall heat-hardening and sintering apparatus shown in FIG. [Figure 8] FIG. 8 is a front view of the crawler in FIG. [Figure 9] FIG. 9 is a plan view of the crawler in FIG. [Figure 10] FIG. 10 is a side view of the crawler in FIG. [Figure 11] FIG. 11 is a schematic diagram of the screen type overall heat-hardening and sintering apparatus in FIG. 7 in an operating state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The technical solution of the present application will be described below clearly and completely with reference to the drawings, but it is clear that the described embodiments are only some of the embodiments of the present application, and are not all of the embodiments. Based on the embodiments of the present application, any other embodiments that a person skilled in the art can obtain without inventive efforts fall within the scope of protection of the present application.

[0028] In the description of this application, the orientations or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the orientations or positional relationships shown in the drawings, and are merely for the purpose of making the application easier to explain and simplifying the description, and do not indicate or imply that the relevant devices or elements necessarily have a specific orientation or must be constructed and operated in a specific orientation, and therefore should not be understood as limiting the application. In addition, the terms "first," "second," and "third" are merely for the purpose of explanation, and should not be understood as indicating or implying relative importance.

[0029] In the description of the present application, unless otherwise clearly specified and limited, the terms "attach", "connect" and "connection" should be understood in a broad sense, for example, may be fixed connection, detachable connection, or integral connection, may be mechanical connection, electrical connection, direct connection, indirect connection through an intermediate element, or internal communication between two elements. Those skilled in the art can understand the specific meaning of the above terms in the present application according to the specific situation.

[0030] Furthermore, unless they conflict with each other, the technical features related to different embodiments of the present application described below may be combined with each other.

[0031] FIG. 1 is a schematic diagram of the overall structure of an apparatus for improving the steam oxidation resistance of a small-diameter boiler tube of a coal-fired boiler according to an embodiment of the present application. As shown in FIG. 1, in this embodiment, when cutting the boiler tube panel on the ceiling, the position of the ceiling cut surface 10 and the position of the lower bend cut surface 13 are determined as follows: the boiler tube panel 14 is detached from the inlet container 11 and the outlet container 12, and the boiler tube panel 14 is cut and separated at the lowest point of the lower bend, as shown in FIG. 1, and the boiler tube panel 14 after cutting is hoisted and fixed by a suspension device in the hearth.

[0032] In this embodiment, the induction coil power supply 21, the sand storage tank 32 and the paint storage tank 42 are arranged on the boiler ceiling 15, and the sand storage tank 32 is connected to the sandblasting device 31 via a sand conveying pipe 33. The paint storage tank 42 may be connected to the spraying device 41 via a material supply pipe 43.

[0033] The sandblasting device 31 and the spraying device 41 of this embodiment can both be sent to the piping through an opening in the upper cut surface of the tube panel 14 of the boiler to carry out the work.

[0034] As shown in FIG. 1, this embodiment provides an apparatus for improving the steam oxidation resistance of small-diameter boiler tubes of a coal-fired boiler, the apparatus comprising at least a sandblasting device 31 configured to remove an oxide film grown on the inner wall of each boiler tube in a tube panel 14 in use, a spraying device 41 configured to apply paint to the boiler tube after sandblasting cleaning, and a screen-type overall heat-hardening and sintering device configured to sinter the boiler tube coated with paint to form an oxidation-resistant coating on the inner tube wall of the boiler tube.

[0035] The apparatus for improving the steam oxidation resistance of small-diameter boiler tubes of a coal-fired boiler in this embodiment first removes the oxide film that has grown on the inner wall of each boiler tube in a tube panel 14 that is in use using a sandblasting device 31, then uses a spraying device 41 to apply paint to the boiler tubes after sandblasting and cleaning, and finally uses a screen-type full-body heating and sintering device to sinter the boiler tubes with the paint applied thereto, thereby forming an oxidation-resistant 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 a coal-fired boiler in use.

[0036] 2 is a schematic diagram of the sandblasting apparatus in FIG. 1, and FIG. 3 is a cross-sectional view of FIG. 2. As shown in FIGS. 2 and 3, the sandblasting apparatus 31 comprises a hollow motor 311, a first nozzle 312, and a sand transport pipe 33. The hollow motor 311 is connected to the first nozzle 312 and configured to drive and rotate the first nozzle 312 to eject the sand material in the chamber of the first nozzle 312 from a band-shaped opening 315 on the surface of the first nozzle 312. The sand transport pipe 33 is configured such that one end extends through the hollow motor 311 into the chamber of the first nozzle 312 and the other end is connected to an external sand source.

[0037] The sandblasting apparatus 31 further includes a towing rope 316, one end of which is connected to an end of the hollow motor 311 remote from the first nozzle 312 and the other end of which is configured to be connected to an external towing device, whereby the external towing device drives the sandblasting apparatus 31 via the towing rope 316 to move it within the boiler tube.

[0038] An annular seal ring 314 is fitted to the outer wall of the hollow motor 311 and / or the first nozzle 312, and the outer diameter of the annular seal ring 314 is kept consistent with the inner diameter of the boiler tube.

[0039] Specifically, the hollow motor 311 is located at the rear of the entire sandblasting device 31, and is connected to an external power source by a conductor 317, and is connected to an external towing device via a towing rope 316. The first nozzle 312 is attached to the front of the sandblasting device 31, and is connected in series with the hollow motor 311 coaxially by a first connector 313 and a first shaft coupling 3131, and the shaft center connecting the two rear parts is held to be consistent. The sand conveying pipe 33 passes through the inside of the hollow motor 311 and the first nozzle 312, and the shaft center position of the sand conveying pipe 33 is fixed by a tightening nut 3211. The end of the sand conveying pipe 33 is provided with a first joint 321, and may be connected to an external sand storage tank 32.

[0040] The hollow motor 311 may be powered by DC, and the conductor 317 is connected to an external power source. A first shaft coupling 3131 for connecting the hollow motor 311 and the first nozzle 312 is attached inside the hollow motor 311, and the first nozzle 312 is driven by the rotation of the hollow motor 311 to rotate at high speed, and the no-load rotation speed of the hollow motor 311 is greater than 30,000 rpm. The tip of the first nozzle 312 may have a tapered structure, and a plurality of strip-shaped openings 315 are provided on the tapered surface, and the sand material is sprayed from the strip-shaped openings 315 onto the inner wall of the boiler tube by the centrifugal force generated by the high-speed rotation of the first nozzle 312. The connection section between the first nozzle 312 and the hollow motor 311 may be a cylindrical hollow casing, which allows for coaxial connection with the hollow motor 311, while the hollow structure of the first nozzle 312 allows for a small amount of sand material to be stored in the chamber, ensuring continuous sandblasting even when the supply of sand material is unstable. An equal-diameter annular seal ring 314 is installed on the outside of each of the hollow motor 311 and the first nozzle 312, and the diameter of the annular seal ring 314 is adjusted to achieve close contact with the inner wall of the boiler tube, thereby ensuring that the entire sandblasting device 31 is always in the center of the piping during the forward movement.

[0041] In order to ensure the quality of sandblasting cleaning, the sandblasting device 31 operates in a backward blowing mode when used. Before sandblasting, the diameter of the annular seal 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 marched to the very end of the boiler tube to be sandblasted. After connecting the power supply to the external sand storage tank 32, the traction device and the hollow motor 311, the sandblasting speed is adjusted by controlling the operating speed of the external traction device. The sand material used by the sandblasting device 31 can be various kinds of sandblasting materials such as emery sand and quartz sand, and the grain size of the sand material should be smaller than 500 mesh.

[0042] Figure 4 is a schematic diagram of the spraying device in Figure 1, Figure 5 is an enlarged schematic diagram of the drive wheel in Figure 4, and Figure 6 is an enlarged schematic diagram of the positioning wheel in Figure 4. As shown in Figures 4, 5 and 6, the spraying device 41 has a drive mechanism 411 and a spraying mechanism 412 connected to each other, the drive mechanism 411 is configured to drive the spraying mechanism 412 to move it within the boiler tube, and the spraying mechanism 412 is configured to spray paint onto the inner wall of the boiler tube.

[0043] The drive mechanism 411 comprises a first case 414, drive wheels 413 and a power battery 4135, and a plurality of drive wheels 413 are installed at intervals along the circumferential direction of the first case 414 on the outer wall of the first case 414, and each drive wheel 413 is capable of extending and retracting along the radial direction of the first case 414. The power battery 4135 is installed within the first case 414 and electrically connected to each drive wheel 413, and is configured to drive and rotate the drive wheels 413.

[0044] The spray mechanism 412 comprises a second case 421, a second nozzle 418, an air motor 419, a gas conveying pipe 44 and a material supply pipe 43, the second case 421 is connected to the first case 414, the second nozzle 418 is installed at the end of the second case 421 remote from the first case 414, the air motor 419 is installed within the second case 421 and has an exhaust port connected to an intake port of the second nozzle 418 which is connected to an external gas source via the gas conveying pipe 44, and the material supply pipe 43 has one end connected to the material supply port of the second nozzle 418 and the other end connected to an external paint source.

[0045] A plurality of positioning rings 417 are installed at intervals along the circumferential direction of second case 421 on the outer wall of second case 421 , and each positioning ring 417 is extendable and contractable along the radial direction of second case 421 .

[0046] The spraying device 41 further comprises an in-camera 420, an out-camera 415 and a thickness sensor 423 configured to monitor the spraying process, the in-camera 420 being installed at an end of the second case 421 remote from the first case 414, the out-camera 415 being installed at an end of the first case 414 remote from the second case 421, and the thickness sensor 423 being installed at an end of the second case 421 remote from the first case 414.

[0047] Specifically, the spray device 41 is mainly composed of a drive mechanism 411 and a spray mechanism 412, and the arrow indicates the rear direction of the spray device 41. The drive mechanism 411 is located at the rear end of the spray device 41 and serves to supply power for forward and backward movement, and has a first case 414, four drive wheels 413 attached to the first case 414 in a cross shape, and a power battery 4135 inside the first case 414.

[0048] The spraying mechanism 412 is attached to the tip of the spraying device 41 and is used to spray paint onto the inner walls of the boiler tubes. The spraying mechanism 412 has a second case 421, four positioning wheels 417 attached to the second case 421 in a cross shape, an air motor 419 provided within the second case 421, a second nozzle 418 provided outside the second case 421, and an in-camera 420, an out-camera 415 and a thickness sensor 423 for monitoring the spraying process.

[0049] The driving mechanism 411 and the spray mechanism 412 of the spray device 41 may be connected in series by a second connector 416, and the axis connecting the two rear parts is kept aligned. In the process of use, the spray paint used may be supplied by the paint storage tank 42, and the carrier gas used may be supplied by an external air compressor.

[0050] The gas carrier pipe 44 passes through the first case 414 and the second case 421, and is connected to a joint of the gas carrier pipe 44 of the air motor 419. The material supply pipe 43 passes through the first case 414 and the second case 421, and is connected to a joint of the material supply pipe 43 of the second nozzle 418.

[0051] The driving wheels 413 are provided with hydraulic telescopic rods 4133 that connect the first wheels 4131 and the first case 414, and a micro hydraulic tank 4134 is provided at the bottom of the driving wheels 413 to supply the necessary pressure to the hydraulic telescopic rods 4133. The four sets of driving wheels 413 are arranged crosswise and have the same structure, and the power battery 4135 inside the first case 414 is arranged in the center, and a space is left for the gas carrier pipe 44 and the material supply pipe 43 to pass through.

[0052] The positioning wheel 417 is for ensuring that the axis of the driving mechanism 411 and the blowing mechanism 412 are aligned, and does not have a power function, thereby reducing unnecessary control units and connection circuits. The positioning wheel 417 is composed of a second wheel 4171, a slide chamber 4173, a slide rod 4172 built into the slide chamber 4173, a compression spring 4174, and a partition plate. When the second wheel 4171 is pressed by an external force, the compression spring 4174 contracts and deforms, and the elastic force is transmitted through the slide rod 4172 to fix the second wheel 4171 to the inner wall of the boiler tube. The four sets of positioning wheels 417 are arranged crosswise and have the same structure. The air motor 419 inside the second case 421 is disposed in the center, and a space is left between the second case 421 and the air motor 419 to allow the material supply pipe 43 to pass through. The air motor 419 has a joint for the gas carrier pipe 44 at its end for connecting to the gas carrier pipe 44, and a second shaft coupling 422 for connecting to the second nozzle 418 is attached to its top. The second nozzle 418 has a strip-shaped opening, and the paint is sprayed from the strip-shaped opening onto the inner wall of the boiler tube by centrifugal force caused by high-speed rotation.

[0053] In order to ensure the quality of the spray coating, the spray device 41 operates in a backward spraying mode when in use. Before spraying, the extension length of the hydraulic telescopic rod 4133 and the slide rod 4172 is adjusted to place the spray device 41 in the inner cavity of the boiler tube to be sprayed, and the external air compressor and the paint storage tank 42 are connected, and then the power battery 4135 is started to supply power to the DC motors 4132 of the four driving wheels 413, so that the spray device 41 marches to the very end of the boiler tube to be sprayed, and the in-camera 420, the out-camera 415 and the thickness sensor 423 are operated to monitor the paint coating process.

[0054] 7 is a schematic diagram of the screen type overall heat-hardening and sintering apparatus in FIG. 1, FIG. 8 is a front view of the crawler in FIG. 7, FIG. 9 is a plan view of the crawler in FIG. 7, FIG. 10 is a side view of the crawler in FIG. 7, and FIG. 11 is a schematic diagram of the screen type overall heat-hardening and sintering apparatus in FIG. 7 in an operating state. As shown in FIG. 7, FIG. 8, FIG. 9, FIG. 10 and FIG. 11, the screen type overall heat-hardening and sintering apparatus is equipped with 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, and the coil moving track 22 is a coil moving track 22. The moving track 22 is configured so that one end is installed on the boiler ceiling 15 and the other end extends vertically downward beyond the bottom of the boiler tube, the crawler 23 is installed inside the coil moving track 22, 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, and the intelligent control cabinet 25 is electrically connected to the crawler 23 and controls the crawler 23 to drive the air-cooled induction heating coil 24 to move along the coil moving track 22, thereby sintering the boiler tube in the air-cooled induction heating coil 24.

[0055] The screen-type full heating hardening sintering device further includes a first stopper 231 and a second stopper 232, which are installed at an interval on the coil movement track 22 to limit the start and end positions of the crawler 23's movement on the coil movement track 22.

[0056] Specifically, both ends of the air-cooled induction heating coil 24 are fixed to the crawlers 23, the crawlers 23 are attached inside the coil moving track 22, the intelligent control cabinet 25 is electrically connected to the crawlers 23, the induction coil power supply 21 is connected to the air-cooled induction heating coil 24 by the crawlers 23, the upper end of the coil moving track 22 is fixed to the boiler ceiling 15 and the lower end is vertically suspended below the bottom of the boiler tube, and the coil moving track 22 is generally used in pairs. A first stopper 231 and a second stopper 232 are arranged at an interval on the coil movement track 22, and the first stopper 231 may be arranged at a position 0.3 m away from the bottom of the boiler ceiling 15, and the second stopper 232 may be arranged at a position 0.5 m below the bottom of the boiler tube, which are for automatically positioning the start and end positions of the operation of the crawler 23, and the crawler 23 is located between the first stopper 231 and the second stopper 232 and holds both ends horizontally.

[0057] A track locking groove 221 is provided on the coil movement track 22, and track slide beads 222 capable of rolling 360° are fitted into the track locking groove 221. The crawler 23 includes a coil fixing bolt 233, a drive motor 236, a boss 237, a second lead-in hole 235, and a first lead-in hole 234. The crawler 23 is connected to the coil movement track 22 by the boss 237 and the track locking groove 221, the track slide beads 222 are for reducing the crawling resistance of the crawler 23, the drive motor 236 supplies crawling power, and the crawler 23 is able to crawl upward and downward by setting the forward and reverse rotation of the drive motor 236. The system of the present invention is assembled and installed before the boiler tube is heat treated, where all the large auxiliary machines such as the induction coil power supply 21 and the intelligent control cabinet 25 are arranged in the entire heating system and fixed to the boiler ceiling 15, and the remaining parts are arranged vertically downward, and the span dimension of the air-cooled induction heating coil 24 can be flexibly changed according to the dimension of the boiler tube panel 14, and is not limited by the dimension of the workpiece such as the boiler tube panel 14.

[0058] As one of the selectable modes of this embodiment, the crawler 23 is adjusted by the intelligent control cabinet 25 to position the crawler 23 at the position of the first stopper 231, and the power, operating speed, operating time, etc. required for the air-cooled induction heating coil 24 are set based on information such as the heat treatment temperature required for the boiler tube and the dimensions of the boiler tube, and the operation button of the intelligent control cabinet 25 is pressed and adjusted by the PLC of the intelligent control cabinet 25. The crawler 23 starts crawling from top to bottom by the drive of the drive motor 236, and when it passes the first stopper 231, the induction coil current is increased. The source 21 is automatically operated, the air-cooled induction heating coil 24 automatically starts to chemically heat-treat the tube panel 14 formed on the boiler tube, and continues to crawl downwards according to the crawler 23, when it completes the heat-treatment of the entire tube panel 14 and reaches the second stopper 232, the intelligent control cabinet 25 sends a signal, the induction coil power supply 21 is automatically turned off, and the induction heating is stopped, and the crawler 23 crawls from bottom to top by the reverse rotation of the driving motor 236 until it returns to its initial position, and the intelligent control cabinet 25 stops working, thus completing the heat-treatment process of the tube panel 14.

[0059] In another embodiment, a method for improving the steam oxidation resistance of small diameter boiler tubes of a coal-fired boiler is provided, the method includes the steps of cutting a boiler tube panel 14 from a boiler ceiling 15, then vertically lifting and fixing it, and cutting a cross section at the bottom of the lower bend of the boiler tube panel 14; cleaning the inner tube wall of each tube body in the boiler tube panel 14; sintering an oxidation-resistant 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 boiler tube panel 14 after sintering.

[0060] In the method for improving the steam oxidation resistance of the small diameter boiler tube of the coal-fired boiler according to the embodiment, the boiler tube panel 14 is first cut from the boiler ceiling 15, then vertically lifted and fixed, and the cross section is cut at the bottom of the lower bend of the boiler tube panel 14, then the inner tube wall of each tube body in the boiler tube panel 14 is cleaned, then an oxidation-resistant coating is sintered on the inner tube wall of each tube body in the boiler tube panel 14, and finally, the tube bodies in the boiler tube panel 14 after sintering are welded and repaired. All the steps of the method can be carried out in the furnace during the period when the furnace is stopped for inspection, so that the production efficiency is high, the inspection period can be significantly shortened, and a steam oxidation-resistant layer can be formed on the inner wall of the small diameter boiler tube, and the steam oxidation resistance of the small diameter boiler tube of the coal-fired boiler during use can be greatly improved.

[0061] When cleaning the inner tube walls of each tube body in the boiler tube panel 14, the process specifically includes removing the oxide film grown on the inner wall of each boiler tube in the tube panel 14 in use by the sandblasting device 31, and the sand material ejected from the sandblasting device 31 includes one or more of brown fused alumina, white fused alumina and quartz sand, and the grain size of the sand material is smaller than 500 mesh.

[0062] Sintering the oxidation-resistant coating on the inner tube wall of each tube body in the boiler tube panel 14 specifically includes the steps of applying paint to the boiler tube after sandblasting cleaning with a spraying device 41, sintering the boiler tube coated with paint with a screen-type whole heat-hardening sintering device to form an oxidation-resistant coating on the inner tube wall of the boiler tube, setting the sintering temperature at 800-900°C, controlling the heat retention time to 10-15 minutes, and cleaning the residue from the sintered boiler tube with a sandblasting device 31.

[0063] In the preparation of the paint, aluminum powder and nickel powder in a mass ratio of 1:1 are used as the penetrating agent, phosphate aqueous solution is used as the solvent, CrO3 is used as the acid inhibitor, and MgO is used as the hardener, and the ratio is prepared as follows: penetrating agent 100g:phosphate aqueous solution 100ml:acid inhibitor 10g:hardener 2g.

[0064] Optionally, the paint spray thickness is 0.2mm~0.3mm.

[0065] Obviously, the above examples are merely examples given for clarity and are not intended to limit the embodiments. Those skilled in the art may make other various modifications or variations based on the above description. It is not possible or necessary to list all the embodiments here. Any obvious modifications or variations derived therefrom are still within the scope of protection of the present application. [Explanation of symbols]

[0066] 10 Ceiling cut surface 11 Entrance Container 12 Exit Container 13 Lower bend cut surface 14 Tube Panel 15 Boiler ceiling 21 Induction coil power supply 22 Coil movement trajectory 23 Crawler 24 Air-cooled induction heating coil 25 Intelligent Control Cabinet 31 Sandblasting Equipment 32 Sand Storage Tank 33 Sand transport pipe 41 Spraying equipment 42 Paint storage tank 43 Material supply pipe 44 Gas conveying pipes 221 Track locking groove 222 Orbital Slide Beads 231 First stopper 232 Second Stopper 233 Coil fixing bolt 234 First intake hole 235 Second intake hole 236 Drive motor 237 Boss 311 Hollow Motor 312 No. 1 nozzle 313 First Connector 314 Annular seal ring 315 Strip opening 316 Towing Rope 317 Conductor 321 First joint 3131 First shaft coupling 3211 Fastening nut 411 Driving Mechanism 412 Spraying mechanism 413 Drive Wheel 414 Case 1 415 Rear Camera 416 Second Connector 417 Positioning wheel 418 No. 2 nozzle 419 Air Motor 420 In-camera 421 Case 2 422 Second Shaft Coupling 423 Thickness Sensor 4131 1st wheel 4132 DC motor 4133 Hydraulic telescopic rod 4134 Hydraulic tank 4135 Power battery 4171 2nd wheel 4172 Slide Rod 4173 Slide Room 4174 Compression spring

Claims

1. 1. A method for improving steam oxidation resistance of small diameter boiler tubes in a coal-fired boiler, comprising: Cutting the boiler tube panel from the boiler ceiling, then vertically lifting and fixing it, and cutting a section at the bottom of the lower bend of the boiler tube panel; cleaning the inner tube walls of each tube body in a tube panel of a boiler; sintering an oxidation-resistant coating on an inner tube wall of each tube body in a tube panel of a boiler; and repairing each sintered tube body in a tube panel of the boiler by welding.

2. When cleaning the inner tube walls of each tube body in the boiler tube panel, specifically, removing oxide coatings that have grown on the inside walls of each boiler tube in an in-service tube panel with a sandblasting device; 2. The method for improving the steam oxidation resistance of small diameter boiler tubes of a coal-fired boiler as claimed in claim 1, wherein the sand material ejected from the sandblasting device comprises one or more of brown fused alumina, white fused alumina and quartz sand, and the grain size of the sand material is smaller than 500 mesh.

3. Specifically, sintering an oxidation-resistant coating on the inner tube wall of each tube body in a boiler tube panel includes the following steps: applying paint to the boiler tubes after sandblasting with a spraying device; Sintering the painted boiler tube with a screen-type full heat-hardening sintering device to form an oxidation-resistant coating on the inner wall of the boiler tube; 2. The method for improving the steam oxidation resistance of small diameter boiler tubes of a coal-fired boiler according to claim 1, further comprising: cleaning the residue from the boiler tube after sintering with a sandblasting device.

4. In the preparation of the paint, aluminum powder and nickel powder in a mass ratio of 1:1 are used as the penetrant, phosphate solution is used as the solvent, and CrO ３ 4. The method for improving the steam oxidation resistance of small diameter boiler tubes of a coal-fired boiler according to claim 3, characterized in that the method comprises the steps of: using as an acid inhibitor, using as an acid hardener, and preparing the solution in the ratio of 100 g of penetrant, 100 ml of phosphate aqueous solution, 10 g of acid inhibitor, and 2 g of hardener.

5. The method for improving the steam oxidation resistance of small diameter boiler tubes of a coal-fired boiler according to claim 3, characterized in that the coating thickness is 0.2 mm to 0.3 mm.

6. An apparatus for improving the steam oxidation resistance of small diameter boiler tubes of a coal-fired boiler, comprising: a sandblasting device configured to remove oxide coatings that have grown on the inner walls of each boiler tube in an in-use tube panel; a spraying device configured to apply paint to the boiler tubes after sandblasting; and a screen-type overall heat-hardening and sintering device configured to sinter the painted boiler tube to form an oxidation-resistant coating on the inner wall of the boiler tube.

7. The sandblasting device includes a hollow motor, a first nozzle, and a sand conveying pipe; the hollow motor is connected to the first nozzle and configured to drive and rotate the first nozzle to eject sand material in the chamber of the first nozzle from a band-shaped opening on a surface of the first nozzle; The apparatus for improving the steam oxidation resistance of small diameter boiler tubes of a coal-fired boiler as described in claim 6, characterized in that one end of the sand transport pipe extends through the hollow motor into the chamber of the first nozzle and the other end is configured to communicate with an external sand source.

8. 8. The apparatus for improving the steam oxidation resistance of a small diameter boiler tube of a coal-fired boiler as claimed in claim 7, wherein the sandblasting apparatus further comprises a towing rope, one end of the towing rope being connected to an end of the hollow motor away from the first nozzle and the other end being connected to an external towing device, whereby the external towing device drives the sandblasting apparatus via the towing rope to move it within the boiler tube.

9. 8. The device for improving the steam oxidation resistance of a small diameter boiler tube of a coal-fired boiler as described in claim 7, characterized in that an annular seal ring is fitted to the outer wall of the hollow motor and / or the first nozzle, and the outer diameter dimension of the annular seal ring is maintained so as to match the inner diameter dimension of the boiler tube.

10. The apparatus for improving the steam oxidation resistance of a small diameter boiler tube of a coal-fired boiler as described in claim 6, characterized in that the spraying device comprises a drive mechanism and a spraying mechanism connected to each other, the drive mechanism is configured to drive the spraying mechanism to move it within the boiler tube, and the spraying mechanism is configured to spray paint onto the inner wall of the boiler tube.

11. the drive mechanism includes a first case, a drive wheel, and a power battery; A plurality of the drive wheels are installed at intervals along a circumferential direction of the first case on an outer wall of the first case, and each of the drive wheels is extendable and retractable along a radial direction of the first case, 11. The device for improving the steam oxidation resistance of small diameter boiler tubes of a coal-fired boiler as described in claim 10, wherein the power battery is installed in the first case and electrically connected to each of the drive wheels so as to drive and rotate the drive wheels.

12. the spray mechanism includes a second case, a second nozzle, an air motor, a gas conveying pipe, and a material supply pipe; the second case is connected to the first case, and the second nozzle is disposed at an end of the second case remote from the first case; the air motor is installed in the second case, an exhaust port of the air motor is connected to an intake port of the second nozzle, and the intake port is connected to an external gas source via a gas carrier pipe; The device for improving the steam oxidation resistance of a small diameter boiler tube of a coal-fired boiler according to claim 11, characterized in that one end of the material supply pipe is connected to the material supply port of the second nozzle and the other end is connected to an external paint source.

13. 13. The device for improving the steam oxidation resistance of a small diameter boiler tube of a coal-fired boiler as described in claim 12, characterized in that a plurality of positioning rings are installed at intervals along the circumferential direction of the second case on the outer wall of the second case, and each of the positioning rings is expandable and contractible along the radial direction of the second case.

14. The spraying device further includes an in-camera, an out-camera, and a thickness sensor configured to monitor the spraying process; the in-camera is installed at an end of the second case away from the first case, the rear camera is installed at an end of the first case away from the second case, 13. The apparatus for improving steam oxidation resistance of a small diameter boiler tube of a coal-fired boiler as claimed in claim 12, wherein the thickness sensor is installed at an end of the second case remote from the first case.

15. The screen-type full heating hardening 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; The coil movement track is configured such that one end is installed on the boiler ceiling and the other end extends vertically downward beyond the bottom of the boiler tube; The crawler is installed inside the coil movement 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 device for improving the steam oxidation resistance of a small-diameter boiler tube of a coal-fired boiler as described in claim 6, characterized in that the intelligent control cabinet is electrically connected to the crawler and controls the crawler to drive the air-cooled induction heating coil to move along the coil moving track, thereby sintering the boiler tube located within the air-cooled induction heating coil.

16. The screen-type overall heat-hardening and sintering device further includes a first stopper and a second stopper, The device for improving the steam oxidation resistance of a small diameter boiler tube of a coal-fired boiler as described in claim 15, characterized in that the first stopper and the second stopper are installed at an interval on the coil movement track and limit the start and end positions of the crawler's movement on the coil movement track.

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