Device and method for improving density of metal coating on heating surface of boiler

Abstract

The embodiment of the invention provides a device and a method for improving the density of a metal coating on a boiler heating surface. The device comprises a first electrode, a second electrode and a high-voltage square-wave pulse power supply, the first electrode and the second electrode are respectively connected with the positive electrode and the negative electrode of the high-voltage square-wave pulse power supply through connecting wires; the first side of the first electrode is arranged to be a first clamping structure which can correspond to a tube bundle on the heating surface of the boiler and is used for being embedded in the tube bundle; the first side of the second electrode is arranged to be a second clamping structure which can correspond to the tube row and is used for being embedded in the tube row; wherein the first electrode is located on the metal coating coated on the tube bundle, and the second electrode is located on the metal coating coated on the tube bundle or located at the position, not coated with the metal coating, of the tube bundle. According to the device for improving the density of the metal coating on the heating surface of the boiler disclosed by the embodiment of the invention, the metal coating can be densified by adopting a pulse current densification process, so that the strength, wear resistance and corrosion resistance of the metal coating are improved.

Description

Technical Field

[0001] The embodiments of the present disclosure belong to the technical field of boiler heating surface coatings, and particularly relate to a device and method for improving the density of a metal coating on a boiler heating surface. Background Art

[0002] To achieve the carbon peak and carbon neutrality targets on schedule and promote the absorption of renewable energy, coal-fired units, currently the mainstay of power generation, are widely participating in deep peak-shaving operations. On the one hand, the low-load conditions during peak-shaving operations exacerbate corrosion on boiler heating surfaces and increase the frequency of tube bursts. On the other hand, to adapt to market-driven coal prices, many coal-fired power plants have implemented coal blending. The blending of high-sulfur, high-chloride, high-alkali coals or biomass has exacerbated the corrosive nature of boiler flue gas, leading to frequent tube bursts and jeopardizing safe boiler operation. To mitigate high-temperature corrosion on boiler heating surfaces, major thermal power plants have implemented measures including optimizing fuel blending ratios, technological upgrades to combustion systems, combustion optimization adjustments, and active protection measures such as in-furnace desulfurization. While these measures can mitigate high-temperature corrosion on heating surfaces to a certain extent, their effectiveness is relatively limited. Given the imperfect nature of active protection technologies for high-temperature corrosion on boiler heating surfaces, surface modification and passive protection to enhance corrosion and wear resistance are the most direct and effective means of preventing corrosion and wear on boiler heating surfaces.

[0003] Although various technologies are currently available for producing high-bond-strength coatings, such as laser cladding, induction cladding, and overlay welding, arc spraying remains the most suitable coating production technology for field applications, based on comprehensive analysis of field adaptability, technical complexity, equipment costs, and construction costs. Arc spraying offers advantages such as convenience, flexibility, high efficiency, and strong field adaptability. However, coatings produced using this technology have high porosity, with numerous pores and interconnected pores extending throughout the entire thickness of the coating.

[0004] Whether burning coal or biomass fuels in power plant boilers, corrosive media are generated in the furnace. Gaseous corrosive media such as SO₃ and HCl in the flue gas can easily penetrate the coating through pores, and even enter the interface between the coating and the substrate through through-holes, causing premature coating shedding. Furthermore, alkali metal sulfates have low melting points and are molten at typical wall temperatures. They can also penetrate into the coating pores, reducing the coating's corrosion resistance. Summary of the Invention

[0005] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a device and method for improving the density of the metal coating on the heating surface of a boiler.

[0006] In one aspect, an embodiment of the present disclosure provides a device for improving the density of a metal coating on a heating surface of a boiler, the device comprising a first electrode, a second electrode, and a high-voltage square wave pulse power supply;

[0007] The first electrode and the second electrode are respectively connected to the positive electrode and the negative electrode of the high-voltage square wave pulse power supply through connecting wires;

[0008] The first side of the first electrode is provided with a first engaging structure capable of corresponding to the boiler heating surface tube bank, so as to be embedded in the tube bank;

[0009] The first side of the second electrode is configured as a second engaging structure that can correspond to the tube row and is embedded in the tube row; wherein,

[0010] When the first electrode and the second electrode are embedded in the tube bank, the first electrode is located on the metal coating coated on the tube bank, and the second electrode is located on the metal coating coated on the tube bank, or at a position on the tube bank not coated with the metal coating.

[0011] Optionally, the device further comprises a magnetic base;

[0012] The magnetic base is arranged at two opposite ends of the first electrode and the second electrode, and the magnetic base is connected to the boiler tube by being fitted to fix the first electrode and the second electrode.

[0013] Optionally, the device further comprises a first insulating layer and a second insulating layer;

[0014] The first insulating layer covers the outer surface of the first electrode and exposes the first locking structure;

[0015] The second insulating layer covers the outer surface of the second electrode and exposes the second locking structure.

[0016] Optionally, the device further comprises a first insulating handle and a second insulating handle;

[0017] The first insulating handle is overlapped with the insulating layer portion on the second side of the first electrode, and the second insulating handle is overlapped with the insulating layer portion on the second side of the second electrode; the first side and the second side of each electrode are opposite sides.

[0018] Optionally, the voltage range of the high-voltage square wave pulse power supply is set to 5V~200V, the pulse current width range is 200μs~600μs, the duty cycle range is 20%~80%, and the current density range is 15A / cm 2 ~20A / cm 2 , the duration ranges from 2min to 10min.

[0019] Optionally, the first electrode and the second electrode are both configured as copper electrodes.

[0020] On the other hand, an embodiment of the present disclosure provides a method for improving the density of a metal coating on a heating surface of a boiler, using the device described above, the method comprising:

[0021] Arc spraying is used to spray metal coatings on the fins and tubes of the boiler heating surface to a predetermined thickness;

[0022] embedding a first electrode in the fin and the furnace tube, wherein the first electrode is located on the metal coating;

[0023] Embedding a second electrode in the fin and the furnace tube, wherein the second electrode is located on the metal coating or at a portion of the fin and the furnace tube where the metal coating is not sprayed;

[0024] Connecting the first electrode and the second electrode to the positive electrode and the negative electrode of a high-voltage square wave pulse power supply respectively;

[0025] The parameters of the high-voltage square wave pulse power supply are set and the power is turned on to perform a densification treatment on the metal coating of the boiler heating surface.

[0026] Optionally, the setting of the parameters of the high-voltage square wave pulse power supply includes:

[0027] The voltage range of the high-voltage square wave pulse power supply is set to 5V~200V, the pulse current width range is 200μs~600μs, the duty cycle range is 20%~80%, and the current density range is 15A / cm 2 ~20A / cm 2 , the duration ranges from 2min to 10min.

[0028] Optionally, before spraying the metal coating to a predetermined thickness on the fins and furnace tubes of the boiler heating surface, the method further comprises:

[0029] The fins and furnace tubes of the boiler heating surface are sandblasted.

[0030] Optionally, when the device further includes a magnetic seat, the first electrode is locked by the magnetic seats provided at both ends of the first electrode so that the first electrode is in contact with the heating surface of the furnace tube;

[0031] The second electrode is locked by magnetic seats provided at both ends of the second electrode so that the second electrode is in contact with the heating surface of the furnace tube.

[0032] The disclosed embodiments of the apparatus and method for increasing the density of a boiler heating surface metal coating employ a pulsed current densification process using a first electrode, a second electrode, and a high-voltage square-wave pulse power supply. This densifies the metal coating, improving its overall strength, wear resistance, and corrosion resistance. The device is simple, requires no consumables, offers low application costs, and is flexible, making it suitable for both on-site and in-workshop construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic structural diagram of a device for improving the density of a metal coating on a heating surface of a boiler according to an embodiment of the present disclosure;

[0034] Figure 2 is a schematic cross-sectional view of a mating connection portion of a first electrode according to another embodiment of the present disclosure;

[0035] Figure 3 is a schematic cross-sectional view of a mating connection portion of a second electrode according to another embodiment of the present disclosure;

[0036] Figure 4 for Figure 1 Schematic diagram of the densification application of the device;

[0037] Figure 5 The present invention is a flowchart of a method for improving the density of a metal coating on a boiler heating surface according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0039] like Figures 1 to 4 As shown, a device 100 for improving the density of a metal coating on a boiler heating surface comprises a first electrode 110, a second electrode 120, and a high-voltage square-wave pulse power supply 130. The first electrode 110 and the second electrode 120 are connected to the positive and negative electrodes of the high-voltage square-wave pulse power supply 130, respectively, via connecting wires 200. A first side of the first electrode 110 is provided with a first engaging structure 111 that can correspond with a boiler heating surface tube bank 300 for embedding within the tube bank 300.

[0040] A first side of the second electrode 120 is provided with a second engaging structure 121 that can correspond to the tube bank 300 and is embedded in the tube bank 300. When the first electrode 110 and the second electrode 120 are embedded in the tube bank 300, the first electrode 110 is located on the metal coating 400 coated on the tube bank 300, and the second electrode 120 is located on the metal coating 400 coated on the tube bank 300, or at a location on the tube bank 300 not coated with the metal coating 400.

[0041] Specifically, if Figures 1 to 4 As shown, when the device 100 is in use, the first electrode 110 can be embedded in the tube array 300 via the snap-fit ​​structure 111 on its first side. The first electrode 110 is embedded in the surface of the metal coating 400. The second electrode 120 can also be embedded in the tube array 300 via the snap-fit ​​structure 121 on its first side. The second electrode 120 can be embedded in the surface of the metal coating 400, or it can be embedded in a position of the tube array 300 that is not coated with the metal coating 400. The first electrode 110 and the second electrode 120 are respectively connected to the positive and negative poles of a high-voltage square wave pulse power supply 130 via connecting wires 200. When the high-voltage square wave pulse power supply 130 is activated, the metal coating 400 can be densified through a pulse current densification process.

[0042] It should be noted that when the second electrode 120 is embedded in the surface of the metal coating 400, activating the high-voltage square-wave pulse power supply 130 can primarily produce a significant densification effect on the interior of the metal coating 400. When the second electrode 120 is embedded in a portion of the tube bank 300 not coated with the metal coating 400, activating the high-voltage square-wave pulse power supply 130 can densify and strengthen the interior of the metal coating 400 and the interface between the metal coating 400 and the tube bank 300.

[0043] The first engaging structure 111 and the second engaging structure 121 are both configured to be correspondingly embedded in the tube bank 300. The two structures are identical and both have the characteristics of the shape of the boiler heating surface tube bank. As a specific example, Figures 1 to 4 As shown, the cross-sections of the first engaging structure 111 and the second engaging structure 121 are both arch-shaped, so as to be correspondingly embedded in the tube bank 300 and corresponding to the fins 310 and the furnace tubes 320 of the tube bank 300 .

[0044] The device for increasing the density of the metal coating on the heating surface of a boiler disclosed in the embodiments utilizes a pulsed current densification process, using a first electrode, a second electrode, and a high-voltage square-wave pulse power supply, to densify the interior of the metal coating and the interface between the metal coating and the tube bank. This reduces internal porosity in the metal coating and unbonded areas at the interface between the metal coating and the tube bank. Furthermore, after treatment, the overall strength of the metal coating is enhanced, as is its wear and corrosion resistance. The device has a simple structure, requires no consumables, and offers low application costs.

[0045] For example, Figure 2 and Figure 3 As shown, the device further includes a magnetic base 130. The magnetic base 130 is disposed at two opposite ends of the first electrode 110 and the second electrode 120, and the magnetic base 130 is connected to the boiler tube 320 by being attached to fix the first electrode 110 and the second electrode 120.

[0046] Specifically, if Figures 2 to 4 As shown, magnetic bases 130 are respectively provided at the left and right ends of the first electrode 110. The magnetic bases 130 can lock and fix the first electrode 110, so that the first electrode 110 is closely fitted to the heating surface of the furnace tube 320. Magnetic bases 130 are also respectively provided at the left and right ends of the second electrode 120. The magnetic bases 130 can lock and fix the second electrode 120, so that the second electrode 120 is closely fitted to the heating surface of the furnace tube 320.

[0047] For example, Figures 1 to 3 As shown, the device 100 further includes a first insulating layer 140 and a second insulating layer 160. The first insulating layer 140 is coated on the outer surface of the first electrode 110 and exposes the first engaging structure 111. The second insulating layer 160 is coated on the outer surface of the second electrode 120 and exposes the second engaging structure 121. Specifically, Figures 1 to 3 As shown, the first insulating layer 140 covers the upper surface, left surface and right surface of the first electrode 110 , and the second insulating layer 160 covers the upper surface, left surface and right surface of the second electrode 120 .

[0048] Furthermore, the device includes a first insulating handle 150 and a second insulating handle 170 to facilitate operation. The first insulating handle 150 overlaps the portion of the insulating layer 140 on the second side of the first electrode 110, and the second insulating handle 170 overlaps the portion of the insulating layer 160 on the second side of the second electrode 120. The first side and the second side of each electrode (electrode 110, electrode 120) are opposite sides.

[0049] Specifically, if Figures 1 to 3As shown, the first insulating handle 150 is fixed to the insulating layer 140 on the upper surface of the first electrode 110, and the second insulating handle 170 is fixed to the insulating layer 160 on the upper surface of the second electrode 120. It is easy to understand that the first side and the second side of the first electrode 110 are both sides of its upper and lower surfaces, and the first side and the second side of the second electrode 120 are both sides of its upper and lower surfaces.

[0050] For example, the voltage range of the high-voltage square wave pulse power supply 130 can be set to 5V to 200V, the pulse current width range to 200μs to 600μs, the duty cycle range to 20% to 80%, and the current density range to 15A / cm 2 ~20A / cm 2 By setting the above parameters, the high-voltage square wave pulse power supply 130 can provide a specific pulse current to the first electrode 110 and the second electrode 120, thereby performing a pulse current densification process and improving the density of the metal coating.

[0051] As a specific example, the first electrode 110 and the second electrode 120 are both configured as copper electrodes for better densification control.

[0052] On the other hand, Figure 5 As shown, embodiments of the present disclosure provide a method for increasing the density of a metal coating on a boiler heating surface, utilizing the aforementioned apparatus 100. The specific structure of apparatus 100 can be found in the aforementioned description and will not be described in detail here. The method comprises: first, sandblasting the fins and tubes of the boiler heating surface to remove surface dirt, rust, etc., and increasing surface roughness to improve the adhesion of subsequent coatings.

[0053] S510, using arc spraying to spray metal coating to a predetermined thickness on the fins and furnace tubes of the boiler heating surface.

[0054] Specifically, in this step, arc spraying is used to spray the metal coating to a set thickness on the sandblasted fins and furnace tubes. It should be noted that the metal coating is a metal coating or a metal ceramic coating with conductive function.

[0055] S520 , embedding a first electrode in the fin and the furnace tube, and the first electrode is located on the metal coating.

[0056] Specifically, in this step, the first electrode is locked and connected to the fin and the furnace tube via a magnetic base, so that the first electrode is tightly fitted to the heating surface of the furnace tube.

[0057] S530: embedding a second electrode in the fin and the furnace tube, and the second electrode is located on the metal coating, or located at a portion of the fin and the furnace tube where the metal coating is not sprayed.

[0058] Specifically, in this step, the second electrode is locked and connected to the fins and furnace tubes via a magnetic base, ensuring a tight fit between the second electrode and the heated surface of the furnace tubes. Furthermore, the second electrode can be placed on the metal coating to complement the first electrode in densifying the interior of the metal coating. The second electrode can also be placed on uncoated fins and furnace tubes to complement the first electrode in densifying the interior of the metal coating and the interface between the metal coating and the tube bank.

[0059] At step S540, the first electrode and the second electrode are connected to the positive and negative electrodes of a high-voltage square-wave pulse power supply, respectively. Once the connections are complete, the process continues with step S550, where parameters of the high-voltage square-wave pulse power supply are set and the power is applied to densify the metal coating on the boiler heating surface.

[0060] Specifically, in this step, the voltage range of the high-voltage square wave pulse power supply is set to 5V~200V, the pulse current width range is 200μs~600μs, the duty cycle range is 20%~80%, and the current density range is 15A / cm 2 ~20A / cm 2 The duration range is 2 minutes to 10 minutes. The densification treatment of the metal coating on the boiler heating surface is completed by powering on.

[0061] The disclosed method for increasing the density of a boiler heating surface metal coating densifies the interior of the coating and the interface between the coating and the tube bank, reducing internal porosity and unbonded areas between the coating and the tube bank. Furthermore, the treatment enhances the overall strength of the metal coating and improves its wear and corrosion resistance. This method is simple and flexible, suitable for both on-site and in-workshop construction.

[0062] The following is a detailed description of a specific implementation case: Figures 1 to 4 Arc spraying was used to apply a 45CT coating (a material with the designation 45CT (Ni43Cr1Ti) developed by TAFA, USA, as a corrosion-resistant protective coating for boiler tubes in high-temperature, sulfur-containing atmospheres) to the water-cooled wall surface (boiler heating surface) of a 600MW unit. The metal coating 400 was 0.3mm thick, and the spraying area was 14m long and 5m wide. Using the apparatus 100 for increasing the density of the metal coating on the boiler heating surface of this embodiment, a first electrode 110 was placed on the surface of the 45CT metal coating 400 at the 5-meter width edge, and the first electrode 110 was locked by magnetic bases 130 at both ends.

[0063] The second electrode 120 is tightly fitted to the heated surface of the boiler tube at the other end of 5 meters wide, which is not sprayed with the metal coating 400. At this time, the distance between the two electrodes is 5m, and the second electrode 120 is locked by the magnetic base 130. The first electrode 110 and the second electrode 120 are respectively connected to the positive and negative poles of the high-voltage square wave pulse power supply 130. Set the voltage of the pulse power supply 130 to 30V, the pulse current width to 500μs, the duty cycle to 60%, the current density flowing through the coating interface to 20A / cm2, and the duration to 2min. Since this embodiment processes 4 furnace tubes and the corresponding fin areas at a time, they are processed sequentially in the 14-meter length direction, and it takes about 3 hours to complete all the processing.

[0064] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present disclosure, and such modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A device for improving the density of metal coating on boiler heating surface, characterized in that: The device comprises a first electrode, a second electrode and a high-voltage square wave pulse power supply; The first electrode and the second electrode are respectively connected to the positive electrode and the negative electrode of the high-voltage square wave pulse power supply through connecting wires; The first side of the first electrode is configured as a first engaging structure that can correspond to the tube bank of the boiler heating surface, and is used to be embedded in the tube bank; The first side of the second electrode is configured as a second engaging structure that can correspond to the tube row and is embedded in the tube row; wherein, When the first electrode and the second electrode are embedded in the tube row, the first electrode is located on the metal coating coated on the tube row, and the second electrode is located on the metal coating coated on the tube row, or at a position of the tube row not coated with the metal coating.

2. The device according to claim 1, characterized in that The device also includes a magnetic base; The magnetic base is disposed at two opposite ends of the first electrode and the second electrode, and the magnetic base is connected to the boiler tube by being fitted to fix the first electrode and the second electrode.

3. The device according to claim 1, characterized in that The device also includes a first insulating layer and a second insulating layer; The first insulating layer covers the outer surface of the first electrode and exposes the first clamping structure; The second insulating layer covers the outer surface of the second electrode and exposes the second locking structure.

4. The device according to claim 3, characterized in that The device also includes a first insulating handle and a second insulating handle; The first insulating handle overlaps the insulating layer portion on the second side of the first electrode, and the second insulating handle overlaps the insulating layer portion on the second side of the second electrode; the first side and the second side of each electrode are opposite sides.

5. The device according to any one of claims 1 to 4, characterized in that The voltage range of the high-voltage square wave pulse power supply is set to 5V-200V, the pulse current width range is 200μs-600μs, the duty cycle range is 20%-80%, and the current density range is 15A / cm 2 ~20A / cm 2 , the duration ranges from 2min to 10min.

6. The device according to any one of claims 1 to 4, characterized in that The first electrode and the second electrode are both configured as copper electrodes.

7. A method for improving the density of a metal coating on a boiler heating surface, characterized in that: Using the device according to any one of claims 1 to 6, the method comprises: The fins and tubes of the boiler heating surface are sprayed with metal coating to a predetermined thickness by arc spraying; embedding a first electrode in the fin and the furnace tube, wherein the first electrode is located on the metal coating; Embedding a second electrode in the fin and the furnace tube, and the second electrode is located on the metal coating, or located at a portion of the fin and the furnace tube where the metal coating is not sprayed; Connecting the first electrode and the second electrode to the positive electrode and the negative electrode of a high-voltage square wave pulse power supply respectively; The parameters of the high-voltage square wave pulse power supply are set and the power is turned on to perform a densification treatment on the metal coating of the boiler heating surface.

8. The method according to claim 7, characterized in that The parameters for setting the high-voltage square wave pulse power supply include: The voltage range of the high-voltage square wave pulse power supply is set to 5V-200V, the pulse current width range is 200μs-600μs, the duty cycle range is 20%-80%, and the current density range is 15A / cm 2 ~20A / cm 2 , the duration ranges from 2min to 10min.

9. The method according to claim 7, characterized in that: Before spraying the metal coating to a predetermined thickness on the fins and furnace tubes of the boiler heating surface, the method further comprises: The fins and furnace tubes of the boiler heating surface are sandblasted.

10. The method according to claim 7, characterized in that When the device further includes a magnetic seat, the first electrode is locked by the magnetic seats arranged at both ends of the first electrode so that the first electrode is in contact with the heating surface of the furnace tube; The second electrode is locked by magnetic seats arranged at both ends of the second electrode, so that the second electrode is in contact with the heating surface of the furnace tube.

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