Membrane wall, method for producing same, and circulating fluidized bed boiler

Abstract

The invention provides a membrane wall. The membrane wall comprises a plurality of metal base tubes, a plurality of fins, a corrosion-resistant layer and an alloy layer, the metal base tubes are connected through the fins; the corrosion-resistant layer is formed on the outer surface of the metal base pipe and forms metallurgical bonding with the outer surface; the alloy layer is formed on the surface of the corrosion-resistant layer and is metallurgically bonded with the surface of the corrosion-resistant layer; in the alloy layer, the mass percent of iron is smaller than or equal to 10%, the mass percent of chromium is larger than or equal to 12%, the mass percent of molybdenum is larger than or equal to 5%, the mass percent of tungsten is larger than or equal to 4%, the total mass percent of nickel and cobalt is larger than or equal to 50%, and the Vickers hardness of the alloy layer ranges from 350 Hv to 650 Hv. The invention further provides a manufacturing method of the membrane wall and a circulating fluidized bed boiler. The membrane wall formed by the method can effectively resist corrosion and abrasion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of membrane wall, and in particular to a membrane wall, a manufacturing method thereof, and a circulating fluidized bed boiler. BACKGROUND

[0002] The membrane wall mainly comprises a plurality of metal-based tubes and fins. The metal-based tubes are arranged in parallel, and the fins are arranged between the metal-based tubes and connected with the metal-based tubes by welding. In the prior art, the membrane wall is widely used in boilers (such as circulating fluidized bed boilers) as a heating surface structure. Specifically, the membrane wall is mainly arranged around the furnace of the boiler, and the metal-based tubes thereof have a working medium (referred to as working medium for short) that can flow, such as water, water-steam mixture, etc. When the boiler is working, the membrane wall absorbs the heat generated by the combustion of fuel in the furnace and transmits it to the working medium, and the heat is converted and transmitted through the phase change process of the working medium, thereby ensuring the efficient operation of the boiler. In order to ensure that the membrane wall can work for a long time at high temperature, the metal-based tubes in the membrane wall are usually made of a metal with strong pressure-bearing capacity, such as ferrite steel, low-alloy steel, martensitic steel, etc.

[0003] At present, considering government subsidies and fuel costs, some coal-fired boiler operators begin to use the coupling combustion technology of coal and biomass fuel. In the coupling combustion process of coal and biomass fuel, on the one hand, the hard particles generated by the incomplete combustion of coal continuously impact the surface of the membrane wall with high-speed flue gas, thereby causing progressive wear of the membrane wall; on the other hand, the biomass fuel contains chlorine, and the chlorine compounds generated after its combustion have strong corrosiveness. This corrosiveness acting on the existing membrane wall will cause the rapid thinning of the wall thickness of the metal-based tube. Since the metal-based tube relies on the thickness of the tube wall to maintain the pressure stress, when the corrosion and wear cause the tube wall thickness to thin to a certain extent, the metal-based tube will be broken, thereby causing the boiler to be unable to operate normally. Moreover, after the metal-based tube is broken, the high-temperature and high-pressure steam released therefrom will damage the surface of the adjacent metal-based tube in an instant, causing a chain reaction of damage. In this case, the maintenance cost of the boiler is high and time-consuming, and at the same time, the sale of electricity and / or the supply of industrial steam provided by the boiler are also interrupted accordingly, thereby causing the revenue to be damaged.

[0004] To solve the above problems, the current main approach is to form a protective coating on the surface of the metal base tube of the membrane wall to resist corrosion and wear caused by the coupled fuel combustion process. However, the protective coating with wear resistance usually has a certain hardness but relatively poor toughness, which leads to the possibility of cracking of the protective coating when deformed due to the difference in thermal expansion during welding solidification, installation or service, and the cracks formed by cracking can penetrate the entire thickness of the protective coating to reach the outer surface of the metal base tube. This will lead to more serious crevice corrosion of the metal base tube by the chlorides produced by the combustion of biomass fuel. That is, the existing membrane wall cannot effectively resist corrosion and wear caused by coupled combustion. SUMMARY

[0005] To overcome the above-mentioned defects in the prior art, the present application provides a manufacturing method of a membrane wall, which comprises:

[0006] providing a plurality of metal base tubes and a plurality of fins;

[0007] connecting the metal base tubes with the fins and forming a corrosion-resistant layer on the outer surface of the metal base tube which is metallurgically combined with the outer surface; or forming a corrosion-resistant layer on the outer surface of the metal base tube which is metallurgically combined with the outer surface, and connecting the metal base tube with the fins on which the corrosion-resistant layer is formed on the outer surface;

[0008] forming an alloy layer on the surface of the corrosion-resistant layer which is metallurgically combined with the surface to obtain a membrane wall, wherein the mass percentage of iron in the alloy layer is less than or equal to 10%, the mass percentage of chromium is greater than or equal to 12%, the mass percentage of molybdenum is greater than or equal to 5%, the mass percentage of tungsten is greater than or equal to 4%, the total mass percentage of nickel and cobalt is greater than or equal to 50%, and the Vickers hardness of the alloy layer ranges from 350Hv to 650Hv.

[0009] According to one aspect of the present application, in the manufacturing method, the step of connecting the metal base tubes with the fins and forming a corrosion-resistant layer on the outer surface of the metal base tube which is metallurgically combined with the outer surface comprises: connecting the fins with the metal base tubes to form a first tube row structure; forming a corrosion-resistant layer on the entire outer surface of each metal base tube which is metallurgically combined with the entire outer surface, or forming a corrosion-resistant layer on the radially single-sided outer surface of each metal base tube which is metallurgically combined with the radially single-sided outer surface, wherein the corrosion-resistant layers on the outer surfaces of all the metal base tubes are located on the same side of the first tube row structure.

[0010] According to another aspect of the present application, in the manufacturing method, the corrosion-resistant layer extends to the surface of the fin.

[0011] According to yet another aspect of the present application, in the manufacturing method, the material of the metal base pipe comprises one or any combination of carbon steel, low alloy steel, and martensitic steel; and the material of the fin is implemented by using an iron-based alloy.

[0012] According to yet another aspect of the present application, in the manufacturing method, the step of forming a corrosion-resistant layer on the outer surface of the metal base pipe and metallurgically combining the corrosion-resistant layer with the outer surface, and connecting the metal base pipe with the corrosion-resistant layer formed on the outer surface by using the fin, comprises: forming a corrosion-resistant layer on the entire outer surface of each metal base pipe and metallurgically combining the corrosion-resistant layer with the entire outer surface, and connecting the fin with the metal base pipe with the corrosion-resistant layer formed thereon to form a second pipe row structure; or forming a corrosion-resistant layer on the radially single-side outer surface of each metal base pipe and metallurgically combining the corrosion-resistant layer with the radially single-side outer surface, and connecting the fin with the metal base pipe with the corrosion-resistant layer formed thereon to form a second pipe row structure, wherein the corrosion-resistant layers on the outer surfaces of the metal base pipes are located on the same side of the second pipe row structure.

[0013] According to yet another aspect of the present application, in the manufacturing method, the alloy layer extends to the surface of the fin.

[0014] According to yet another aspect of the present application, in the manufacturing method, the material of the metal base pipe comprises one or any combination of carbon steel, low alloy steel, and martensitic steel; and the material of the fin is implemented by using a nickel-based alloy.

[0015] According to yet another aspect of the present application, in the manufacturing method, the material of the corrosion-resistant layer is a nickel-based alloy; and the thickness of the corrosion-resistant layer is greater than or equal to 0.5 mm.

[0016] According to yet another aspect of the present application, in the manufacturing method, the thickness of the alloy layer is greater than or equal to 0.9 mm.

[0017] The present application also provides a membrane wall, comprising:

[0018] a plurality of metal base pipes, a plurality of fins, a corrosion-resistant layer, and an alloy layer;

[0019] The metal base pipes are connected by the fins;

[0020] The corrosion-resistant layer is formed on the outer surface of the metal base pipe and is metallurgically combined with the outer surface;

[0021] The alloy layer is formed on the surface of the corrosion-resistant layer and forms a metallurgical bond with the surface, wherein the mass percentage of iron in the alloy layer is less than or equal to 10%, the mass percentage of chromium is greater than or equal to 12%, the mass percentage of molybdenum is greater than or equal to 5%, the mass percentage of tungsten is greater than or equal to 4%, the total mass percentage of nickel and cobalt is greater than or equal to 50%, and the Vickers hardness of the alloy layer ranges from 350Hv to 650Hv.

[0022] According to an aspect of the present application, in the membrane wall, the corrosion-resistant layer is formed on the entire outer surface of the metal base pipe; or the corrosion-resistant layer is formed on the radially single-side outer surface of the metal base pipe, and the corrosion-resistant layers on all the outer surfaces of the metal base pipes are located on the same side of the membrane wall.

[0023] According to another aspect of the present application, in the membrane wall, the corrosion-resistant layer extends to the surface of the fin.

[0024] According to still another aspect of the present application, in the membrane wall, the material of the metal base pipe comprises one or any combination of carbon steel, low-alloy steel and martensitic steel; and the material of the fin is realized by using an iron-based alloy.

[0025] According to still another aspect of the present application, in the membrane wall, the alloy layer extends to the surface of the fin.

[0026] According to still another aspect of the present application, in the membrane wall, the material of the metal base pipe comprises one or any combination of carbon steel, low-alloy steel and martensitic steel; and the material of the fin is realized by using a nickel-based alloy.

[0027] According to still another aspect of the present application, in the membrane wall, the material of the corrosion-resistant layer is a nickel-based alloy; and the thickness of the corrosion-resistant layer is greater than or equal to 0.5mm.

[0028] According to still another aspect of the present application, in the membrane wall, the thickness of the alloy layer is greater than or equal to 0.9mm.

[0029] The present application also provides a circulating fluidized bed boiler comprising the aforementioned membrane wall.

[0030] The manufacturing method of the membrane wall provided by the application comprises the following steps: forming a corrosion-resistant layer and an alloy layer on the outer surface of a metal base pipe in sequence, wherein the mass percentage of iron in the alloy layer is less than or equal to 10%, the mass percentage of chromium is greater than or equal to 12%, the mass percentage of molybdenum is greater than or equal to 5%, the mass percentage of tungsten is greater than or equal to 4%, and the total mass percentage of nickel and cobalt is greater than or equal to 50%, and the Vickers hardness of the alloy layer ranges from 350 Hv to 650 Hv. The alloy layer with the above composition and hardness can well resist the wear caused by the coupled combustion process. Moreover, even if the alloy layer cracks and produces a crack penetrating the thickness of the alloy layer due to the deformation caused by the difference in thermal expansion during welding solidification, installation or service, since the metal base pipe surface is also formed with the corrosion-resistant layer which has good toughness and is not easy to crack, the damage to the metal base pipe caused by crevice corrosion can be effectively avoided. In addition, the alloy layer on the surface of the corrosion-resistant layer also has a certain protective effect on the corrosion-resistant layer, so that the corrosion-resistant layer will not be abraded and can maintain excellent corrosion resistance, thereby improving the corrosion resistance of the membrane wall. That is, the membrane wall formed by the application can effectively resist the corrosion and wear caused by the coupled combustion. Accordingly, the membrane wall provided by the application has the characteristics of effectively resisting the corrosion and wear caused by the coupled combustion. The circulating fluidized bed boiler formed based on the membrane wall provided by the application has the advantages of long service life, stable operation and low maintenance cost. BRIEF DESCRIPTION OF DRAWINGS

[0031] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments, when read in conjunction with the accompanying drawings:

[0032] Figure 1 is a manufacturing method flow chart of a membrane wall according to a specific embodiment of the application;

[0033] Figure 2 is a cross-sectional structure schematic diagram of a membrane wall according to a specific embodiment of the application;

[0034] Figure 3 is a cross-sectional structure schematic diagram of a membrane wall according to another specific embodiment of the application;

[0035] Figure 4 is a cross-sectional structure schematic diagram of a membrane wall according to another specific embodiment of the application;

[0036] Figure 5 is a cross-sectional structure schematic diagram of a membrane wall according to another specific embodiment of the application.

[0037] The same or similar reference signs in the drawings represent the same or similar components.

[0038] REFERENCE SIGNS

[0039] 100 - metal base pipe, 101 - corrosion resistant layer, 102 - alloy layer, 103 - fin. DETAILED DESCRIPTION

[0040] In order to better understand and illustrate the present application, the present application will be further described in detail below with reference to the accompanying drawings.

[0041] The present application provides a manufacturing method of a membrane wall, the manufacturing method comprising:

[0042] In step S100, a plurality of metal base pipes and a plurality of fins are provided;

[0043] In step S101, the metal base pipes are connected by the fins, and a corrosion resistant layer is formed on the outer surface of the metal base pipes and metallurgically combined with the outer surface; or a corrosion resistant layer is formed on the outer surface of the metal base pipes and metallurgically combined with the outer surface, and the metal base pipes with the corrosion resistant layer formed on the outer surface are connected by the fins;

[0044] In step S102, an alloy layer is formed on the surface of the corrosion resistant layer and metallurgically combined with the surface to obtain a membrane wall, wherein the mass percentage of iron element in the alloy layer is less than or equal to 10%, the mass percentage of chromium element is greater than or equal to 12%, the mass percentage of molybdenum element is greater than or equal to 5%, the mass percentage of tungsten element is greater than or equal to 4%, the total mass percentage of nickel element and cobalt element is greater than or equal to 50%, and the Vickers hardness of the alloy layer ranges from 350Hv to 650Hv.

[0045] The above steps S100 to S102 will be described in detail below.

[0046] Specifically, in step S100, first, a number of metal base tubes are provided with a number of fins. In the present embodiment, the material of the metal base tube includes one or any combination of carbon steel, low alloy steel, and martensitic steel. Those skilled in the art can understand that the above-mentioned carbon steel, low alloy steel, and martensitic steel are only preferred embodiments, which should not be a limitation on the material of the metal base tube. Any material suitable for manufacturing the metal base tube in the prior art and in the future is applicable to the present application. For the sake of simplicity, all possible materials of the metal base tube are not listed one by one. In the present embodiment, the material of the fin is implemented by using iron-based alloy or nickel-based alloy (such as 622 alloy or 625 alloy, etc.). Those skilled in the art can understand that the above-mentioned iron-based alloy and nickel-based alloy are only preferred embodiments, which should not be a limitation on the material of the fin. Any material suitable for manufacturing the fin in the prior art and in the future is applicable to the present application. For the sake of simplicity, all possible materials of the fin are not listed one by one. In addition, the specifications and the number of the metal base tube and the fin depend on the design requirements of the membrane wall, which is not specifically limited in the present application.

[0047] In step S101, in one specific embodiment, the metal-based pipes are first connected by fins, and then a corrosion-resistant layer is formed on the outer surface of the metal-based pipes and metallurgically combined with the outer surface of the metal-based pipes. It should be noted that (1) in this embodiment, the metal-based pipes are arranged in parallel, fins are arranged between two adjacent metal-based pipes, and the fins are connected to the adjacent metal-based pipes by welding to form a first pipe arrangement structure. Those skilled in the art can understand that in this embodiment, the metal-based pipes are arranged in parallel, and the fins are connected to the metal-based pipes by welding, which is only a preferred embodiment and should not be a limitation on the arrangement and connection of the metal-based pipes and fins. The arrangement and connection of the metal-based pipes and fins can be determined according to the actual design requirements. For the sake of simplicity, all possible cases are not listed here. (2) In consideration of performance and cost, the area of the corrosion-resistant layer formed on the outer surface of the metal-based pipe preferably coincides with the projection of the area of the final formed membrane wall exposed to the furnace in the radial direction of the metal-based pipe. For example, for the case where one side surface of the final formed membrane wall is exposed to the furnace, a corrosion-resistant layer is formed on the radial single-side outer surface of each metal-based pipe in the first pipe arrangement structure and metallurgically combined with the radial single-side outer surface, and all the corrosion-resistant layers on the outer surfaces of the metal-based pipes are located on the same side of the first pipe arrangement structure. For example, for the case where the entire surface of the final formed membrane wall is exposed to the furnace, a corrosion-resistant layer is formed on the entire outer surface of each metal-based pipe in the first pipe arrangement structure and metallurgically combined with the entire outer surface. Those skilled in the art can understand that the area of the corrosion-resistant layer formed on the outer surface of the metal-based pipe coincides with the projection of the area of the final formed membrane wall exposed to the furnace in the radial direction of the metal-based pipe, which is only a preferred embodiment and should not be a limitation on the area of the corrosion-resistant layer. In other embodiments, the specific formation area of the corrosion-resistant layer on the outer surface of the metal-based pipe can be selected according to the actual application scenario of the membrane wall, and the present application does not make specific limitations thereon. For the sake of simplicity, all possible formation areas of the corrosion-resistant layer are not listed here. (3) For the case where the fins are made of a material with relatively poor corrosion resistance (such as iron-based alloy), the corrosion-resistant layer on the outer surface of the metal-based pipe preferably extends to the surface of the fin, so that the fin can be prevented from breaking due to corrosion under the premise of preventing the metal-based pipe from breaking due to corrosion.In the case where the fins are made of a material with relatively poor corrosion resistance (for example, iron-based alloy), if one side surface of the finally formed membrane wall is exposed to the furnace, a corrosion-resistant layer covering one side outer surface of the first tube array structure can be formed, so that the corrosion-resistant layer is formed on the radial one-side outer surface of each metal base tube and extends to the surface of the fin; if the entire surface of the finally formed membrane wall is exposed to the furnace, a corrosion-resistant layer covering the entire outer surface of the first tube array structure can be formed, so that the corrosion-resistant layer is formed on the entire outer surface of each metal base tube and extends to the surface of the fin.

[0048] In another specific embodiment, a corrosion-resistant layer metallurgically combined with the outer surface of the metal base tube is first formed on the outer surface of the metal base tube, and then the metal base tube with the corrosion-resistant layer is connected by the fin. It should be noted that (1) in this embodiment, in consideration of performance and cost, the forming area of the corrosion-resistant layer on the outer surface of the metal base tube is preferably consistent with the projection of the area of the finally formed membrane wall exposed to the furnace in the radial direction of the metal base tube. For example, in the case where one side surface of the finally formed membrane wall is exposed to the furnace, a corrosion-resistant layer metallurgically combined with the radial one-side outer surface of each metal base tube is formed on the radial one-side outer surface. For another example, in the case where the entire surface of the finally formed membrane wall is exposed to the furnace, a corrosion-resistant layer metallurgically combined with the entire outer surface of each metal base tube is formed on the entire outer surface. Those skilled in the art can understand that in other embodiments, the specific forming area of the corrosion-resistant layer on the outer surface of the metal base tube can be selected according to the actual application scenario of the membrane wall, which is not limited in the present application. For the sake of simplicity, all possible forming areas of the corrosion-resistant layer are not listed here. (2) In this embodiment, the step of connecting the metal base tube with the corrosion-resistant layer by the fin includes: arranging a plurality of metal base tubes with the corrosion-resistant layer in parallel and arranging fins between adjacent metal base tubes; and connecting the fins and the adjacent metal base tubes by welding to form a second tube array structure. In the case where the radial one-side outer surface of the metal base tube is formed with the corrosion-resistant layer (i.e., the case where one side surface of the finally formed membrane wall is exposed to the furnace), when the metal base tube with the corrosion-resistant layer is connected by the fin to form the second tube array structure, the corrosion-resistant layer on the outer surface of all the metal base tubes needs to be located on the same side of the second tube array structure. (3) In this embodiment, the fin is preferably made of a material with good corrosion resistance (for example, nickel-based alloy).

[0049] It should also be noted that (1) the corrosion-resistant layer can be formed on the outer surface of the metal-based tube by cladding and metallurgically bonded to the outer surface. The high bonding strength of the metallurgical bonding makes the corrosion-resistant layer less likely to peel off, and the defect-free interface formed by the metallurgical bonding is conducive to improving the performance of the corrosion-resistant layer. Those skilled in the art can understand that cladding is only one preferred embodiment of forming a corrosion-resistant layer, and any forming process that can metallurgically bond the corrosion-resistant layer to the outer surface of the metal-based tube is applicable to the present application. For the sake of simplicity, all possible forming processes of the corrosion-resistant layer are not listed here. (2) In this embodiment, the corrosion-resistant layer is implemented by using a nickel-based alloy with excellent corrosion resistance and good toughness and less likely to crack, such as 622 alloy, 625 alloy, etc. The thickness of the corrosion-resistant layer is preferably greater than or equal to 0.5 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, etc. Those skilled in the art can understand that the nickel-based alloy should not be a limitation on the material of the corrosion-resistant layer, and any metal material with corrosion resistance and good toughness and less likely to crack is applicable to the corrosion-resistant layer in the present application. For the sake of simplicity, all possible materials of the corrosion-resistant layer are not listed here.

[0050] In step S102, an alloy layer metallurgically bonded to the surface of the corrosion-resistant layer is formed on the surface of the corrosion-resistant layer to obtain a membrane wall. In this embodiment, the alloy layer includes corrosion-resistant elements (mainly nickel elements), and the alloy layer has a certain hardness. Specifically, the mass percentage of iron elements in the alloy layer is less than or equal to 10%, the mass percentage of chromium elements is greater than or equal to 12%, the mass percentage of molybdenum elements is greater than or equal to 5%, the mass percentage of tungsten elements is greater than or equal to 4%, and the total mass percentage of nickel elements and cobalt elements is greater than or equal to 50%. The Vickers hardness of the alloy layer ranges from 350 Hv to 650 Hv, such as 350 Hv, 450 Hv, 550 Hv, 650 Hv, etc. The alloy layer with the above composition and hardness has excellent wear resistance and can effectively resist wear of the membrane wall during the coupled combustion of coal and biomass fuel. When the Vickers hardness of the alloy layer is less than 350 Hv, the wear resistance of the alloy layer is poor, and when the Vickers hardness of the alloy layer is greater than 650 Hv, the alloy layer is too brittle and prone to breakage. In addition, in this embodiment, the thickness of the alloy layer is preferably greater than or equal to 0.9 mm, such as 0.9 mm, 1 mm, 1.1 mm, etc.

[0051] It should be noted that the specific mass percentage of each element in the alloy layer and the specific Vickers hardness range of the alloy layer are determined according to actual design requirements (for example, manufacturing difficulty, expected service life, etc.), and the present application does not make specific limitations thereon. In one preferred embodiment, the mass percentage of iron in the alloy layer is less than or equal to 8%, the mass percentage of chromium is greater than or equal to 14.5%, the mass percentage of molybdenum is greater than or equal to 5%, the mass percentage of tungsten is greater than or equal to 7%, and the total mass percentage of nickel and cobalt is greater than or equal to 50%, and the Vickers hardness range of the alloy layer is 450Hv to 650Hv. In another preferred embodiment, the mass percentage of iron in the alloy layer is less than or equal to 10%, the mass percentage of chromium is greater than or equal to 12%, the mass percentage of molybdenum is greater than or equal to 13.5%, the mass percentage of tungsten is greater than or equal to 4%, and the total mass percentage of nickel and cobalt is greater than or equal to 50%, and the Vickers hardness range of the alloy layer is 350Hv to 450Hv.

[0052] It should also be noted that (1) preferably, the alloy layer is formed on the entire surface of the corrosion-resistant layer, i.e., the alloy layer covers the entire surface of the corrosion-resistant layer. Of course, those skilled in the art can understand that in other embodiments, the alloy layer can also be formed on part of the surface of the corrosion-resistant layer (i.e., the alloy layer covers part of the surface of the corrosion-resistant layer) according to design requirements, and the present application does not make specific limitations thereon. (2) For the case where the corrosion-resistant layer extends from the outer surface of the metal-based tube to the surface of the fin, the alloy layer is formed on the surface of the corrosion-resistant layer, which includes not only the part on the outer surface of the metal-based tube but also the part extending to the surface of the fin. For example, for the case where the corrosion-resistant layer extends from the outer surface of the metal-based tube to the surface of the fin, if the alloy layer is formed on the entire surface of the corrosion-resistant layer, it means that the alloy layer covers the corrosion-resistant layer on the outer surface of the metal-based tube and the corrosion-resistant layer on the surface of the fin. (3) For the case where the surface of the fin has no corrosion-resistant layer, preferably, the alloy layer extends from the metal-based tube to the surface of the fin, thereby improving the wear resistance of the fin and further improving the wear resistance of the membrane wall. (4) In the present embodiment, the alloy layer is formed by laser welding, and a metallurgical bond is formed between the alloy layer and the surface of the corrosion-resistant layer. The high bonding strength of the metallurgical bond makes the alloy layer less likely to peel off, and the defect-free interface formed by the metallurgical bond is beneficial to improving the performance of the alloy layer. Those skilled in the art can understand that laser welding is only one preferred embodiment for forming the alloy layer, and any forming process that can form a metallurgical bond between the alloy layer and the surface of the corrosion-resistant layer is suitable for the present application, and for the sake of simplicity, all possible forming processes of the alloy layer are not listed here.

[0053] The manufacturing method of the membrane wall provided by the application forms two protective layers of a corrosion-resistant layer and an alloy layer on the surface of the metal base pipe in sequence. The mass percentage of iron in the alloy layer is less than or equal to 10%, the mass percentage of chromium is greater than or equal to 12%, the mass percentage of molybdenum is greater than or equal to 5%, the mass percentage of tungsten is greater than or equal to 4%, the total mass percentage of nickel and cobalt is greater than or equal to 50%, and the Vickers hardness of the alloy layer ranges from 350Hv to 650Hv. In this way, the alloy layer has excellent wear resistance and can well resist the wear caused by the coupled combustion of coal and biomass fuel. Moreover, even if the alloy layer cracks and produces cracks through the thickness of the alloy layer due to the deformation caused by the difference in thermal expansion during welding solidification, installation or service, since the metal base pipe surface is also formed with the corrosion-resistant layer which has good toughness and is not easy to crack, the damage to the metal base pipe caused by crevice corrosion can be effectively avoided. In addition, the alloy layer on the surface of the corrosion-resistant layer also protects the corrosion-resistant layer to some extent, so the corrosion-resistant layer will not be worn and can maintain excellent corrosion resistance, thereby improving the corrosion resistance of the membrane wall. Therefore, the membrane wall obtained by implementing the application can effectively resist the corrosion and wear caused by the coupled combustion process.

[0054] The application further provides a membrane wall, which comprises:

[0055] several metal base pipes, several fins, a corrosion-resistant layer and an alloy layer;

[0056] The metal base pipes are connected through the fins;

[0057] The corrosion-resistant layer is formed on the outer surface of the metal base pipe and forms a metallurgical bond with the outer surface;

[0058] The alloy layer is formed on the surface of the corrosion-resistant layer and forms a metallurgical bond with the surface, wherein the mass percentage of iron in the alloy layer is less than or equal to 10%, the mass percentage of chromium is greater than or equal to 12%, the mass percentage of molybdenum is greater than or equal to 5%, the mass percentage of tungsten is greater than or equal to 4%, the total mass percentage of nickel and cobalt is greater than or equal to 50%, and the Vickers hardness of the alloy layer ranges from 350Hv to 650Hv.

[0059] The various components of the membrane wall will be described in detail below.

[0060] Specifically, the membrane wall provided by the present application comprises several metal base pipes and fins, wherein the metal base pipes are connected by the fins. In the embodiment, the metal base pipes are arranged in parallel, fins are arranged between two adjacent metal base pipes, and the two adjacent metal base pipes and the fins arranged therebetween are connected by welding. Those skilled in the art can understand that, in the embodiment, the metal base pipes are arranged in parallel and the fins are connected to the metal base pipes by welding, which are only preferred embodiments and should not be regarded as a limitation on the arrangement and connection of the metal base pipes and the fins. The arrangement and connection of the metal base pipes and the fins can be determined according to actual design requirements, and for the sake of simplicity, all possible cases are not listed here. In the embodiment, the material of the metal base pipe comprises one or any combination of carbon steel, low alloy steel and martensitic steel. Those skilled in the art can understand that the above-mentioned carbon steel, low alloy steel and martensitic steel are only preferred embodiments and should not be regarded as a limitation on the material of the metal base pipe. Any material suitable for manufacturing the metal base pipe in the prior art and in the future is suitable for the present application, and for the sake of simplicity, all possible materials of the metal base pipe are not listed here. In the embodiment, the material of the fin is implemented by using iron-based alloy or nickel-based alloy (for example, 622 alloy or 625 alloy, etc.). Those skilled in the art can understand that the above-mentioned iron-based alloy and nickel-based alloy are only preferred embodiments and should not be regarded as a limitation on the material of the fin. Any material suitable for manufacturing the fin in the prior art and in the future is suitable for the present application, and for the sake of simplicity, all possible materials of the fin are not listed here. In addition, the specifications and the number of the metal base pipe and the fin depend on the design requirements of the membrane wall, which are not limited in the present application.

[0061] The membrane wall provided by the present application further comprises a corrosion-resistant layer formed on the outer surface of the metal base pipe and forming a metallurgical bond with the outer surface. In this regard, in consideration of performance and cost, the forming area of the corrosion-resistant layer on the outer surface of the metal base pipe preferably coincides with the projection of the area of the membrane wall exposed in the furnace on the radial direction of the metal base pipe. For example, for the case that one side surface of the membrane wall is exposed in the furnace, the corrosion-resistant layer is formed on the radial one-side outer surface of the metal base pipe, and the corrosion-resistant layer on all the outer surfaces of the metal base pipe is located on the same side of the membrane wall. For another example, for the case that the entire surface of the membrane wall is exposed in the furnace, the corrosion-resistant layer is formed on the entire outer surface of the metal base pipe. It can be understood by those skilled in the art that the forming area of the corrosion-resistant layer on the outer surface of the metal base pipe, which coincides with the projection of the area of the membrane wall exposed in the furnace on the radial direction of the metal base pipe, is only a preferred embodiment, and should not be a limitation on the forming area of the corrosion-resistant layer. In other embodiments, the specific forming area of the corrosion-resistant layer on the outer surface of the metal base pipe can be selected according to the actual application scene of the membrane wall, which is not limited in the present application. For the sake of simplicity, all possible forming areas of the corrosion-resistant layer are not listed here. In the present embodiment, the corrosion-resistant layer is implemented by using a nickel-based alloy with excellent corrosion resistance and good toughness and not easy to crack, such as 622 alloy, 625 alloy, etc. The thickness of the corrosion-resistant layer is preferably greater than or equal to 0.5 mm, such as 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, etc. It can be understood by those skilled in the art that the nickel-based alloy should not be a limitation on the material of the corrosion-resistant layer. Any metal material with corrosion resistance and good toughness and not easy to crack is suitable for the corrosion-resistant layer in the present application. For the sake of simplicity, all possible materials of the corrosion-resistant layer are not listed here.

[0062] For the case that the fins are implemented by using a material with excellent corrosion resistance (such as a nickel-based alloy), the corrosion-resistant layer only needs to be formed on the outer surface of the metal base pipe. For the case that the fins are implemented by using a material with relatively poor corrosion resistance (such as an iron-based alloy), preferably, the corrosion-resistant layer located on the outer surface of the metal base pipe extends to the surface of the fins, so that the fins can be prevented from being broken due to corrosion under the premise of preventing the metal base pipe from being broken due to corrosion.

[0063] The membrane wall provided by the present application further comprises an alloy layer formed on the surface of the corrosion-resistant layer and forming a metallurgical bond with the surface of the corrosion-resistant layer. In the embodiment, the alloy layer comprises corrosion-resistant elements (mainly nickel elements), and the alloy layer has a certain hardness. Specifically, the mass percentage of iron elements in the alloy layer is less than or equal to 10%, the mass percentage of chromium elements is greater than or equal to 12%, the mass percentage of molybdenum elements is greater than or equal to 5%, the mass percentage of tungsten elements is greater than or equal to 4%, and the total mass percentage of nickel elements and cobalt elements is greater than or equal to 50%, and the Vickers hardness of the alloy layer ranges from 350Hv to 650Hv, such as 350Hv, 450Hv, 550Hv, 650Hv, etc. The alloy layer with the above composition and hardness has excellent wear resistance and can effectively resist the wear of the membrane wall in the coupled combustion process of coal and biomass fuel. When the Vickers hardness of the alloy layer is less than 350Hv, the wear resistance of the alloy layer is poor, and when the Vickers hardness of the alloy layer is greater than 650Hv, the alloy layer is too brittle and is prone to breakage. In addition, in the embodiment, the thickness of the alloy layer is preferably greater than or equal to 0.9mm, such as 0.9mm, 1mm, 1.1mm, etc.

[0064] It should be noted that the specific mass percentage of each element in the alloy layer and the specific Vickers hardness range of the alloy layer are determined according to the actual design requirements (such as manufacturing difficulty, expected service life, etc.), and the present application does not make specific limitations thereon. In a preferred embodiment, the mass percentage of iron elements in the alloy layer is less than or equal to 8%, the mass percentage of chromium elements is greater than or equal to 14.5%, the mass percentage of molybdenum elements is greater than or equal to 5%, the mass percentage of tungsten elements is greater than or equal to 7%, and the total mass percentage of nickel elements and cobalt elements is greater than or equal to 50%, and the Vickers hardness of the alloy layer ranges from 450Hv to 650Hv. In another preferred embodiment, the mass percentage of iron elements in the alloy layer is less than or equal to 10%, the mass percentage of chromium elements is greater than or equal to 12%, the mass percentage of molybdenum elements is greater than or equal to 13.5%, the mass percentage of tungsten elements is greater than or equal to 4%, and the total mass percentage of nickel elements and cobalt elements is greater than or equal to 50%, and the Vickers hardness of the alloy layer ranges from 350Hv to 450Hv.

[0065] It should be further noted that (1) preferably, the alloy layer is formed on the entire surface of the corrosion-resistant layer, i.e., the alloy layer covers the entire surface of the corrosion-resistant layer. Of course, those skilled in the art can understand that in other embodiments, the alloy layer can also be formed on part of the surface of the corrosion-resistant layer (i.e., the alloy layer covers part of the surface of the corrosion-resistant layer) according to design needs, and the present application does not make specific limitations thereto. (2) For the case where the corrosion-resistant layer extends from the outer surface of the metal base pipe to the surface of the fin, the alloy layer is formed on the surface of the corrosion-resistant layer, where the corrosion-resistant layer includes not only the part on the outer surface of the metal base pipe but also the part extending to the surface of the fin. For example, for the case where the corrosion-resistant layer extends from the outer surface of the metal base pipe to the surface of the fin, if the alloy layer is formed on the entire surface of the corrosion-resistant layer, it means that the alloy layer covers the corrosion-resistant layer on the outer surface of the metal base pipe and the corrosion-resistant layer on the surface of the fin. (3) For the case where the surface of the fin has no corrosion-resistant layer, preferably, the alloy layer extends from the metal base pipe to the surface of the fin, so as to improve the wear resistance of the fin and further improve the wear resistance of the membrane wall.

[0066] The membrane wall provided by the present application has two protective layers, i.e., a corrosion-resistant layer and an alloy layer, formed on the surface of the metal base pipe in sequence. In the alloy layer, the mass percentage of iron is less than or equal to 10%, the mass percentage of chromium is greater than or equal to 12%, the mass percentage of molybdenum is greater than or equal to 5%, the mass percentage of tungsten is greater than or equal to 4%, and the total mass percentage of nickel and cobalt is greater than or equal to 50%, and the Vickers hardness of the alloy layer ranges from 350Hv to 650Hv. In this way, the alloy layer has excellent wear resistance and can well resist the wear caused by the coupled combustion of coal and biomass fuel. Moreover, even if the alloy layer cracks and produces a crack penetrating the thickness of the alloy layer due to thermal expansion difference during welding solidification, installation or service, since the surface of the metal base pipe also has the corrosion-resistant layer which is not easy to crack and has good toughness, the damage of crevice corrosion to the metal base pipe can be effectively avoided. In addition, the alloy layer on the surface of the corrosion-resistant layer also has a certain protective effect on the corrosion-resistant layer, so that the corrosion-resistant layer will not be worn and can maintain excellent corrosion resistance, thereby improving the corrosion resistance of the membrane wall. Therefore, the membrane wall provided by the present application can effectively resist the corrosion and wear caused by the coupled combustion process.

[0067] The membrane wall provided by the present application will be described below with specific embodiments.

[0068] As Figure 2As shown in the drawing, in this embodiment, the membrane wall includes metal base pipes 100, a corrosion resistant layer 101, an alloy layer 102, and fins 103. The fins 103 are made of a metal material with poor corrosion resistance, such as iron-based alloy. The metal base pipes 100 are connected by the fins 103 to form a first tube bank structure. The corrosion resistant layer 101 is formed on one side surface of the first tube bank structure in a metallurgical bond. Specifically, the corrosion resistant layer 101 is formed on the radially single-side outer surface of each metal base pipe 100 and extends to the surface of the fins 103. The alloy layer 102 is formed on the entire surface of the corrosion resistant layer 101 in a metallurgical bond.

[0069] As shown in the drawing, in this embodiment, the membrane wall includes metal base pipes 100, a corrosion resistant layer 101, an alloy layer 102, and fins 103. The fins 103 are made of a metal material with poor corrosion resistance, such as iron-based alloy. The metal base pipes 100 are connected by the fins 103 to form a first tube bank structure. The corrosion resistant layer 101 is formed on one side surface of the first tube bank structure in a metallurgical bond. Specifically, the corrosion resistant layer 101 is formed on the radially single-side outer surface of each metal base pipe 100 and extends to the surface of the fins 103. The alloy layer 102 is formed on the entire surface of the corrosion resistant layer 101 in a metallurgical bond. Figure 3 As shown in the drawing, in this embodiment, the membrane wall includes metal base pipes 100, a corrosion resistant layer 101, an alloy layer 102, and fins 103. The fins 103 are made of a metal material with poor corrosion resistance, such as iron-based alloy. The metal base pipes 100 are connected by the fins 103 to form a first tube bank structure. The corrosion resistant layer 101 is formed on one side surface of the first tube bank structure in a metallurgical bond. Specifically, the corrosion resistant layer 101 is formed on the radially single-side outer surface of each metal base pipe 100 and extends to the surface of the fins 103. The alloy layer 102 is formed on the entire surface of the corrosion resistant layer 101 in a metallurgical bond.

[0070] As shown in the drawing, in this embodiment, the membrane wall includes metal base pipes 100, a corrosion resistant layer 101, an alloy layer 102, and fins 103. The fins 103 are made of a metal material with poor corrosion resistance, such as iron-based alloy. The metal base pipes 100 are connected by the fins 103 to form a first tube bank structure. The corrosion resistant layer 101 is formed on one side surface of the first tube bank structure in a metallurgical bond. Specifically, the corrosion resistant layer 101 is formed on the radially single-side outer surface of each metal base pipe 100 and extends to the surface of the fins 103. The alloy layer 102 is formed on the entire surface of the corrosion resistant layer 101 in a metallurgical bond. Figure 4 As shown in the drawing, in this embodiment, the membrane wall includes metal base pipes 100, a corrosion resistant layer 101, an alloy layer 102, and fins 103. The fins 103 are made of a metal material with poor corrosion resistance, such as iron-based alloy. The metal base pipes 100 are connected by the fins 103 to form a first tube bank structure. The corrosion resistant layer 101 is formed on one side surface of the first tube bank structure in a metallurgical bond. Specifically, the corrosion resistant layer 101 is formed on the radially single-side outer surface of each metal base pipe 100 and extends to the surface of the fins 103. The alloy layer 102 is formed on the entire surface of the corrosion resistant layer 101 in a metallurgical bond.

[0071] Figure 5 As shown in the drawing, in this embodiment, the membrane wall includes metal base pipes 100, a corrosion resistant layer 101, an alloy layer 102, and fins 103. The fins 103 are made of a metal material with poor corrosion resistance, such as iron-based alloy. The metal base pipes 100 are connected by the fins 103 to form a first tube bank structure. The corrosion resistant layer 101 is formed on one side surface of the first tube bank structure in a metallurgical bond. Specifically, the corrosion resistant layer 101 is formed on the radially single-side outer surface of each metal base pipe 100 and extends to the surface of the fins 103. The alloy layer 102 is formed on the entire surface of the corrosion resistant layer 101 in a metallurgical bond.

[0072] ​The application further provides a circulating fluidized bed boiler, which comprises the aforementioned membrane wall, wherein the membrane wall is arranged around a furnace (i.e. a combustion chamber) of the circulating fluidized bed boiler, so as to realize efficient heat transfer. It should be noted that (1) the specific structure of the aforementioned membrane wall can refer to the content of the corresponding part in the foregoing description, and will not be described again here for the sake of simplicity; (2) a typical circulating fluidized bed boiler mainly comprises a combustion system, a steam-water system, a flue gas system and an auxiliary system. Further, the combustion system mainly comprises a wind distribution device, a furnace, a cyclone separator and a return valve, for realizing efficient combustion of fuel and particle circulation; the steam-water system mainly comprises a membrane wall, a superheater, an economizer and a steam drum, for being responsible for heat transfer and steam generation; the flue gas system mainly regulates airflow through a primary air fan, a secondary air fan, an induced draft fan and an air preheater, for guaranteeing combustion and heat transfer; and the auxiliary system mainly comprises a bed material adding device, a slag discharging device, a desulfurization device and a dust removal device, for ensuring stable and environmentally-friendly operation of the boiler. The circulating fluidized bed boiler provided by the application can realize the other components by using the existing conventional components, except for the membrane wall, and the other components of the circulating fluidized bed boiler will not be described one by one here for the sake of simplicity.

[0073] Since the membrane wall provided by the application can effectively resist corrosion and wear caused by coupled combustion, the circulating fluidized bed boiler formed based on the membrane wall has the advantages of long service life, stable operation and low maintenance cost.

[0074] It is apparent for those skilled in the art that the application is not limited to the details of the foregoing exemplary embodiments, and the application can be implemented in other specific forms without departing from the spirit or essential characteristics of the application. Therefore, the embodiments should be considered as exemplary and non-limiting, and the scope of the application is defined by the appended claims rather than the foregoing description, and all changes falling within the meaning and range of equivalent elements of the claims are intended to be embraced by the application. Any reference signs in the claims should not be considered as limiting the claims involved. In addition, it is clear that the word "comprise" does not exclude other components, units or steps, and the singular does not exclude the plural. The plurality of components, units or devices stated in the system claims can also be implemented by one component, unit or device through software or hardware.

[0075] The above disclosure is only some preferred embodiments of the application, and of course cannot limit the scope of the rights of the application, so equivalent changes made according to the claims of the application are still within the scope of the application.

Claims

1. A method for manufacturing a membrane wall, the method comprising: providing a plurality of metallic base tubes and a plurality of fins; joining the metallic base tubes with the fins and forming a corrosion resistant layer on the outer surface of the metallic base tubes that is metallurgically bonded to the outer surface; or forming a corrosion resistant layer on the outer surface of the metallic base tubes that is metallurgically bonded to the outer surface and joining the metallic base tubes with the fins on which the corrosion resistant layer is formed on the outer surface; forming an alloy layer on the surface of the corrosion resistant layer that is metallurgically bonded to the surface to obtain a membrane wall, wherein the alloy layer has a mass percentage of iron less than or equal to 10%, a mass percentage of chromium greater than or equal to 12%, a mass percentage of molybdenum greater than or equal to 5%, a mass percentage of tungsten greater than or equal to 4%, a mass percentage of nickel and cobalt combined greater than or equal to 50%, and a Vickers hardness of the alloy layer in a range of 350 Hv to 650 Hv.

2. The manufacturing method according to claim 1, wherein, the step of joining the metallic base tubes with the fins and forming a corrosion resistant layer on the outer surface of the metallic base tubes that is metallurgically bonded to the outer surface comprises: joining the fins with the metallic base tubes to form a first tube arrangement; forming a corrosion resistant layer on the entire outer surface of each of the metallic base tubes that is metallurgically bonded to the entire outer surface; or forming a corrosion resistant layer on a radially single-sided outer surface of each of the metallic base tubes that is metallurgically bonded to the radially single-sided outer surface, wherein the corrosion resistant layers on the outer surfaces of all of the metallic base tubes are on a same side of the first tube arrangement.

3. The manufacturing method according to claim 2, wherein, the corrosion resistant layer extends onto a surface of the fins.

4. The method of claim 3, wherein: the material of the metallic base tubes comprises one or any combination of carbon steel, low alloy steel, and martensitic steel; the material of the fins is implemented using an iron-based alloy.

5. The manufacturing method according to claim 1, wherein, the step of forming a corrosion resistant layer on the outer surface of the metallic base tubes that is metallurgically bonded to the outer surface and joining the metallic base tubes with the fins on which the corrosion resistant layer is formed on the outer surface comprises: forming a corrosion resistant layer on the entire outer surface of each of the metallic base tubes that is metallurgically bonded to the entire outer surface and joining the fins with the metallic base tubes on which the corrosion resistant layer is formed to form a second tube arrangement; or forming a corrosion resistant layer on a radially single-sided outer surface of each of the metallic base tubes that is metallurgically bonded to the radially single-sided outer surface and joining the fins with the metallic base tubes on which the corrosion resistant layer is formed to form a second tube arrangement, wherein the corrosion resistant layers on the outer surfaces of the metallic base tubes are on a same side of the second tube arrangement.

6. The manufacturing method according to claim 5, wherein, the alloy layer extends onto a surface of the fins.

7. The method of claim 5, wherein: the material of the metallic base tubes comprises one or any combination of carbon steel, low alloy steel, and martensitic steel; the material of the fins is implemented using a nickel-based alloy.

8. The method of claim 1, wherein: the material of the corrosion resistant layer is a nickel-based alloy; the thickness of the corrosion resistant layer is greater than or equal to 0.5 mm.

9. The production method according to claim 1, wherein the thickness of the alloy layer is greater than or equal to 0.9 mm.

10. A membrane wall, comprising: a plurality of metal base tubes, a plurality of fins, a corrosion resistant layer, and an alloy layer; the metal base tubes are connected by the fins; the corrosion resistant layer is formed on an outer surface of the metal base tubes and forms a metallurgical bond with the outer surface; the alloy layer is formed on a surface of the corrosion resistant layer and forms a metallurgical bond with the surface, wherein the alloy layer has a mass percentage of iron element less than or equal to 10%, a mass percentage of chromium element greater than or equal to 12%, a mass percentage of molybdenum element greater than or equal to 5%, a mass percentage of tungsten element greater than or equal to 4%, a mass percentage of nickel element and cobalt element in total greater than or equal to 50%, and a Vickers hardness of the alloy layer ranges from 350Hv to 650Hv.

11. The membrane wall of claim 10, wherein: the corrosion resistant layer is formed on the entire outer surface of the metal base tubes; or the corrosion resistant layer is formed on a radially single-side outer surface of the metal base tubes, and the corrosion resistant layers on all the outer surfaces of the metal base tubes are located on the same side of the membrane wall.

12. The membrane wall according to claim 10 or 11, wherein, the corrosion resistant layer extends to a surface of the fins.

13. The membrane wall of claim 12, wherein: a material of the metal base tubes comprises one or any combination of carbon steel, low alloy steel, and martensitic steel; a material of the fins is implemented by an iron-based alloy.

14. The membrane wall of claim 10 or 11, wherein, the alloy layer extends to a surface of the fins.

15. The membrane wall of claim 14, wherein: a material of the metal base tubes comprises one or any combination of carbon steel, low alloy steel, and martensitic steel; a material of the fins is implemented by a nickel-based alloy.

16. The membrane wall of claim 10, wherein: a material of the corrosion resistant layer is a nickel-based alloy; a thickness of the corrosion resistant layer is greater than or equal to 0.5mm.

17. The diaphragm wall of claim 10 wherein, a thickness of the alloy layer is greater than or equal to 0.9mm.

18. A circulating fluidized bed boiler, comprising the membrane wall of any one of claims 10 to 17.

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