Apparatus and method for improving the density of a boiler heating surface metal coating

Abstract

The embodiment of the present disclosure provides a device and method for improving the density of a metal coating of a boiler heating surface, the device comprising a first electrode, a second electrode and a high-voltage square-wave pulse power supply; the first electrode and the second electrode are connected to the positive electrode and the negative electrode of the high-voltage square-wave pulse power supply through connecting wires respectively; the first side of the first electrode is provided with a first clamping structure corresponding to a tube bank of the boiler heating surface, for embedding in the tube bank; the first side of the second electrode is provided with a second clamping structure corresponding to the tube bank, for embedding in the tube bank; wherein 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 where the tube bank is not coated with the metal coating. The device for improving the density of the metal coating of the boiler heating surface in the embodiment of the present disclosure can perform densification treatment on the metal coating by using a pulse current densification process, so as to improve the strength and the wear resistance and corrosion resistance of the metal coating.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure belong to the technical field of boiler heating surface coating, and particularly relate to a device and method for improving the density of a boiler heating surface metal coating. BACKGROUND

[0002] In order to achieve the "carbon peak" and "carbon neutralization" targets on schedule and promote the consumption of new energy, coal-fired units, as the main body of power generation at present, widely participate in deep peak shaving. On the one hand, the low load condition in the process of peak shaving causes the corrosion of the boiler heating surface to intensify and the frequency of pipe bursts to increase. On the other hand, in order to adapt to the marketization of coal prices, many coal-fired power plants implement coal blending, and the blending of high-sulfur, high-chlorine and high-alkali coal or biomass causes the corrosiveness of the boiler flue gas to intensify, and the boiler to have frequent pipe burst accidents, which endangers the safe operation of the boiler. In order to reduce the problem of high-temperature corrosion of the boiler heating surface, the major thermal power plants take the following measures for treatment: optimizing the blending ratio of fuels, technical transformation of the combustion system, combustion optimization adjustment, and injection of desulfurizing agents into the furnace, etc. Although these measures can slow down the high-temperature corrosion of the heating surface to some extent, the effect is relatively limited. Against the background of imperfect active protection technology for the high-temperature corrosion of the boiler heating surface, carrying out surface modification and protection treatment on the heating surface and improving the corrosion and wear resistance of the boiler heating surface through passive protection are the most direct and effective technical means for preventing the corrosion and wear of the boiler heating surface.

[0003] Although there are currently various technical means such as laser cladding, induction cladding, and overlay welding for the preparation of high-bonding-strength coatings, from the aspects of field adaptability, technical complexity, equipment cost, and construction cost, etc., electric arc spraying is still the most suitable coating preparation technology at present. Electric arc spraying has the characteristics of convenience, flexibility, high efficiency, and strong field adaptability. However, the coating prepared by this technology has high porosity, and there are many pores in the coating, and there are also connected pores that penetrate through the entire thickness of the coating.

[0004] In power station boilers, whether burning coal or burning biomass fuel, corrosive media will be generated in the furnace. Gaseous corrosive media such as SO3 and HCl in the flue gas can easily enter the inside of the coating through the pores of the coating, and even enter the interface between the coating and the substrate through the penetrating pores, causing the coating to fall off prematurely. In addition, alkali metal sulfates have low melting points and are in a molten state at normal wall temperatures, and can also penetrate into the pores of the coating, causing the corrosion resistance of the coating to decrease. SUMMARY

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

[0006] In one aspect, the embodiments of the present disclosure provide a device for improving the density of a metal coating on a boiler heating surface, 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 and negative poles 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 clamping structure corresponding to a tube bank of the boiler heating surface, for embedding in the tube bank;

[0009] The first side of the second electrode is provided with a second clamping structure corresponding to the tube bank, for embedding in the tube bank; 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 of the tube bank, and the second electrode is located on the metal coating of the tube bank or at a position where the tube bank is not coated with the metal coating.

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

[0012] The magnetic base is arranged at the opposite ends of the first electrode and the second electrode, and the magnetic base is attached to the boiler tube 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 clamping structure;

[0015] The second insulating layer covers the outer surface of the second electrode and exposes the second clamping 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 part on the second side of the first electrode, and the second insulating handle is overlapped with the insulating layer part 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 5V-200V, the pulse current width range is 200μs-600μs, the duty cycle range is 20%-80%, the current density range is 15A / cm 2 -20A / cm 2 , and the duration range is 2min-10min.

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

[0020] In another aspect, embodiments of the present disclosure provide a method for improving the density of a metal coating on a boiler heating surface, using the device described above, the method comprising:

[0021] applying a metal coating to the fins and tubes of the boiler heating surface to a predetermined thickness using arc spraying;

[0022] embedding a first electrode in the fins and tubes, and the first electrode being on the metal coating;

[0023] embedding a second electrode in the fins and tubes, and the second electrode being on the metal coating or on a part of the fins and tubes that is not coated with the metal coating;

[0024] connecting the first electrode and the second electrode to the positive and negative poles of a high-voltage square wave pulse power source, respectively;

[0025] setting parameters of the high-voltage square wave pulse power source and applying power to densify the metal coating on the boiler heating surface.

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

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

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

[0029] sandblasting the fins and tubes of the boiler heating surface.

[0030] Optionally, when the device further comprises a magnetic base, the first electrode is locked by the magnetic base arranged at both ends of the first electrode, so that the first electrode is attached to the boiler heating surface;

[0031] the second electrode is locked by the magnetic base arranged at both ends of the second electrode, so that the second electrode is attached to the boiler heating surface.

[0032] The device and method for improving the density of the metal coating of the boiler heating surface of the embodiment of the present disclosure, by the first electrode, the second electrode and the high-voltage square wave pulse power source arranged, adopts the pulse current densification process to densify the metal coating, and the overall strength, the wear resistance and the corrosion resistance of the metal coating are improved. The device is simple, has no consumables, has low application cost, is flexible to operate, and is suitable for on-site and workshop construction. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A structural schematic view of a device for improving the density of the metal coating of the boiler heating surface of an embodiment of the present disclosure;

[0034] Figure 2 A cross-sectional schematic view of a matching connecting part of a first electrode of another embodiment of the present disclosure;

[0035] Figure 3 A cross-sectional schematic view of a matching connecting part of a second electrode of another embodiment of the present disclosure;

[0036] Figure 4 A Figure 1 A densification application schematic view of the device;

[0037] Figure 5 A flow schematic block diagram of a method for improving the density of the metal coating of the boiler heating surface of an embodiment of the present disclosure. DETAILED DESCRIPTION

[0038] In order for those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure will be further described in detail below in combination with the drawings and specific embodiments.

[0039] As Figures 1 to 4 shown, a device 100 for improving the density of the metal coating of the boiler heating surface, the device 100 comprising a first electrode 110, a second electrode 120 and a high-voltage square wave pulse power source 130. The first electrode 110 and the second electrode 120 are respectively connected with the positive and negative electrodes of the high-voltage square wave pulse power source 130 through connecting wires 200. The first side of the first electrode 110 is provided with a first clamping structure 111 corresponding to the boiler heating surface tube bank 300, so as to be embedded in the tube bank 300.

[0040] The first side of the second electrode 120 is provided with a second clamping structure 121 corresponding to the tube bank 300, so as to be 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 position where the tube bank 300 is not coated with the metal coating 400.

[0041] Specifically, as shown in Figures 1 to 4 When the device 100 is applied, the first electrode 110 can be correspondingly embedded in the tube bank 300 through the clamping structure 111 on the first side of the first electrode 110, and the first electrode 110 is embedded on the surface of the metal coating 400. The second electrode 120 can also be correspondingly embedded in the tube bank 300 through the clamping structure 121 on the first side of the second electrode 120, and the second electrode 120 can be embedded on the surface of the metal coating 400 or at a position where the tube bank 300 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 electrodes of the high-voltage square wave pulse power supply 130 through the connecting wires 200, the high-voltage square wave pulse power supply 130 is started, and the metal coating 400 can be densified by the pulse current densification process.

[0042] It should be noted that when the second electrode 120 is embedded on the surface of the metal coating 400, the high-voltage square wave pulse power supply 130 can mainly produce obvious densification effect inside the metal coating 400. When the second electrode 120 is embedded at a position where the tube bank 300 is not coated with the metal coating 400, the high-voltage square wave pulse power supply 130 can perform densification strengthening treatment on the inside of the metal coating 400 and the contact interface between the metal coating 400 and the tube bank 300.

[0043] The first clamping structure 111 and the second clamping structure 121 are both provided as structures capable of being correspondingly embedded in the tube bank 300, and the structures of the two are the same, both being structures with the shape characteristics of the boiler heating surface tube bank. As a specific example, as shown in Figures 1 to 4 The cross sections of the first clamping structure 111 and the second clamping structure 121 are both multiple arch shapes, so as to be correspondingly embedded in the tube bank 300 and correspond to the fins 310 and the furnace tubes 320 of the tube bank 300.

[0044] The device for improving the density of the metal coating of the heating surface of the boiler of the embodiments of the present disclosure can produce densification treatment on the inside of the metal coating and the contact interface of the metal coating-tube bank by the first electrode, the second electrode and the high-voltage square wave pulse power source, and reduce the internal porosity of the metal coating and the unbinding of the contact interface of the metal coating and the tube bank. After the treatment of the metal coating, the overall strength of the metal coating is improved, and the wear resistance and corrosion resistance are improved. The device has a simple structure, no consumables and low application cost.

[0045] Exemplarily, as shown in Figure 2 and Figure 3 , the device further comprises a magnetic base 130. The magnetic base 130 is arranged at the 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 fitting to fix the first electrode 110 and the second electrode 120.

[0046] Specifically, as shown in Figures 2 to 4 , the magnetic base 130 is arranged at the left and right ends of the first electrode 110 respectively, and the magnetic base 130 can lock and fix the first electrode 110, so that the first electrode 110 is tightly fitted with the heating surface of the tube 320. The magnetic base 130 is also arranged at the left and right ends of the second electrode 120 respectively, and the magnetic base 130 can lock and fix the second electrode 120, so that the second electrode 120 is tightly fitted with the heating surface of the tube 320.

[0047] Exemplarily, as shown in Figures 1 to 3 , the device 100 further comprises a first insulating layer 140 and a second insulating layer 160. The first insulating layer 140 covers the outer surface of the first electrode 110 and exposes the first clamping structure 111. The second insulating layer 160 covers the outer surface of the second electrode 120 and exposes the second clamping structure 121. Specifically, as shown in Figures 1 to 3 , the first insulating layer 140 covers the upper surface, the left surface and the right surface of the first electrode 110, and the second insulating layer 160 covers the upper surface, the left surface and the right surface of the second electrode 120.

[0048] Further, the device further comprises a first insulating handle 150 and a second insulating handle 170 to facilitate operation. The first insulating handle 150 is overlapped with the insulating layer 140 part on the second side of the first electrode 110, and the second insulating handle 170 is overlapped with the insulating layer 160 part 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, as shown in Figures 1 to 3As shown, the first insulation handle 150 is fixed on the insulation layer 140 on the upper surface of the first electrode 110, and the second insulation handle 170 is fixed on the insulation layer 160 on the upper surface of the second electrode 120. It is not difficult to understand that the first side and the second side of the first electrode 110 are the upper and lower surfaces thereof, and the first side and the second side of the second electrode 120 are the upper and lower surfaces thereof.

[0050] Exemplarily, the voltage range of the high-voltage square wave pulse power supply 130 can be set to 5V-200V, the pulse current width range can be set to 200μs-600μs, the duty cycle range can be set to 20%-80%, the current density range can be set to 15A / cm 2 -20A / cm 2 , and the duration range can be set to 2min-10min. Through the above parameter setting, 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, so as to perform the pulse current densification process and improve the density of the metal coating.

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

[0052] On the other hand, as Figure 5 shown, the embodiment of the present disclosure provides a method for improving the density of the metal coating of the heating surface of a boiler, which adopts the device 100 described in the foregoing, and the specific structure of the device 100 can be referred to the related description in the foregoing, which will not be described in detail here. The method comprises: first, performing sandblasting treatment on the fins and the furnace tubes of the heating surface of the boiler to remove dirt, rust, etc. on the surface and increase the surface roughness to improve the adhesion of the subsequent coating.

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

[0054] Specifically, in this step, arc spraying is adopted to spray a 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 a conductive function.

[0055] S520, embedding the first electrode in the fins and the furnace tubes, and the first electrode is located on the metal coating.

[0056] Specifically, in this step, the first electrode is connected to the fins and the furnace tubes by a magnetic force seat locking, so that the first electrode is tightly attached to the heating surface of the furnace tube. Moreover, the first electrode is located on the metal coating.

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

[0058] Specifically, in this step, the second electrode is locked and connected to the fin and the furnace tube by the magnetic force seat, so that the second electrode is tightly attached to the heating surface of the furnace tube. And the second electrode can be provided on the metal coating to cooperate with the first electrode to densify the inside of the metal coating. The second electrode can also be provided at a position where the fin and the furnace tube are not sprayed with the metal coating to cooperate with the first electrode to densify the inside of the metal coating and the contact interface of the metal coating-tube row.

[0059] S540, connecting the first electrode and the second electrode to the positive and negative poles of the high-voltage square wave pulse power source respectively. After the connection is completed, proceed to step S550, set the parameters of the high-voltage square wave pulse power source and power on to densify the metal coating of the boiler heating surface.

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

[0061] The method for improving the density of the metal coating of the boiler heating surface of the embodiment of the present disclosure can produce densification treatment on the inside of the coating and the contact interface of the coating-tube row, reduce the internal pores of the metal coating, and reduce the unbinding of the contact interface of the metal coating and the tube row. After the treatment of the metal coating, the overall strength of the metal coating is improved, and the wear resistance and corrosion resistance are improved. The method is simple in process and flexible in operation, and is suitable for on-site and workshop construction.

[0062] The following will be described in detail with a specific implementation case: Figures 1 to 4 Arc spraying is used to spray 45CT coating on the surface of the water-cooled wall (boiler heating surface) of a 600MW level unit. The material with the brand 45CT(Ni43Cr1Ti) developed by TAFA company in the United States is used as the corrosion-resistant protective coating of the boiler tube in the high-temperature sulfur-containing atmosphere. The thickness of the metal coating 400 is 0.3mm, and the size of the spraying area is 14m long and 5m wide. The first electrode 110 is placed on the surface of the 45CT metal coating 400 with a width of 5m by using the device 100 for improving the density of the metal coating of the boiler heating surface of the embodiment, and the first electrode 110 is locked by the magnetic force seat 130 at both ends.

[0063] The second electrode 120 is closely attached to the other end of the 5-meter-wide boiler tube heating surface without the sprayed metal coating 400. At this time, the distance between the two electrodes is 5 m, and the second electrode 120 is locked by the magnetic force seat 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. The voltage of the pulse power supply 130 is set to 30 V, the pulse current width is 500 μs, the duty cycle is 60%, the current density flowing through the coating interface is 20 A / cm2, and the duration is 2 min. Since the present embodiment processes 4 furnace tubes and the corresponding fin areas at a time, the processing is sequentially performed in the 14-meter length direction, and it takes about 3 hours to complete the entire processing.

[0064] It can be understood that the above embodiments are only exemplary embodiments adopted for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Various modifications and improvements can be made by those of ordinary skill in the art without departing from the spirit and essence of the present disclosure, and these modifications and improvements are also considered to be within the protection scope of the present disclosure.

Claims

1. An apparatus for improving the density of a metal coating on a boiler heating surface, characterized in that, The device includes 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 and negative terminals of the high-voltage square wave pulse power supply via connecting wires; The first side of the first electrode is configured with a first engaging structure that corresponds to the boiler heating surface tube bank, for embedding in the tube bank; The first side of the second electrode is configured with a second engaging structure that corresponds to the tube array, for embedding in the tube array; wherein... When the first electrode and the second electrode are embedded in the tube array, the first electrode is located on the metal coating of the tube array, and the second electrode is located on the metal coating of the tube array or at a position where the tube array is not coated with the metal coating; The device further 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 engaging structure; The second insulating layer covers the outer surface of the second electrode and exposes the second locking structure.

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

3. The apparatus according to claim 1, 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.

4. The apparatus according to any one of claims 1 to 3, characterized in that, The voltage range of the high-voltage square wave pulse power supply is set to 5V to 200V, the pulse current width range is 200μs to 600μs, the duty cycle range is 20% to 80%, and the current density range is 15A / cm². 2 ~20A / cm 2 The duration ranges from 2 minutes to 10 minutes.

5. The apparatus according to any one of claims 1 to 3, characterized in that, Both the first electrode and the second electrode are copper electrodes.

6. A method for improving the density of a metal coating on a boiler heating surface, characterized in that, The method, employing the apparatus according to any one of claims 1 to 5, comprises: Arc spraying is used to coat the fins and furnace tubes of the boiler heating surface with a metal coating to a predetermined thickness. The first electrode is embedded in the fins and the furnace tube, and the first electrode is located on the metal coating; The second electrode is embedded in the fins and furnace tube, and the second electrode is located on the metal coating or in the part of the fins and furnace tube where the metal coating is not applied; wherein, the first insulating layer covers the outer surface of the first electrode and exposes the first engaging structure, and the second insulating layer covers the outer surface of the second electrode and exposes the second engaging structure; Connect the first electrode and the second electrode to the positive and negative terminals of the high-voltage square wave pulse power supply, respectively. The parameters of the high-voltage square wave pulse power supply are set and energized to densify the metal coating on the boiler heating surface.

7. The method according to claim 6, 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 to 200V, the pulse current width range is 200μs to 600μs, the duty cycle range is 20% to 80%, and the current density range is 15A / cm². 2 ~20A / cm 2 The duration ranges from 2 minutes to 10 minutes.

8. The method according to claim 6, characterized in that, Before spraying a metallic coating to a predetermined thickness onto the fins and furnace tubes of the boiler heating surface, the method further includes: The fins and furnace tubes of the boiler heating surface are sandblasted.

9. The method according to claim 6, characterized in that, When the device further includes a magnetic base, the first electrode is locked by the magnetic base located at both ends of the first electrode, so that the first electrode is in contact with the heated surface of the furnace tube; The second electrode is locked by magnetic seats located 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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