Corrosion resistant coating for ammonia decomposition, method of making, and ammonia decomposition reactor

Abstract

This application discloses a corrosion-resistant coating for ammonia decomposition, a preparation method, and an ammonia decomposition reactor. The corrosion-resistant coating for ammonia decomposition comprises, by weight, 15-25 parts zirconium oxide, 15-25 parts niobium disilicide, 45-60 parts elemental metal, and 5-10 parts binder; the binder is polyvinyl alcohol or polyethylene glycol; the corrosion-resistant coating for ammonia decomposition has a particulate structure with a particle size range of 15-45 micrometers. This corrosion-resistant coating for ammonia decomposition possesses both corrosion resistance and high-temperature resistance, meeting the high-temperature and highly corrosive preparation environment required for ammonia decomposition. It also exhibits good thermal conductivity, which is beneficial for the thermal decomposition of ammonia. Furthermore, the denser coating structure improves the mechanical strength of the coating, thereby increasing its service life and enhancing its protective effect on the reactor.

Description

Technical Field

[0001] This invention relates to the field of ammonia decomposition technology, and more specifically to a corrosion-resistant coating for ammonia decomposition, a preparation method thereof, and an ammonia decomposition reactor containing the corrosion-resistant coating for ammonia decomposition. Background Technology

[0002] Ammonia is not only an important inorganic chemical product, but it also has unique advantages as a hydrogen carrier. Ammonia is easily liquefied, has a pungent odor, is non-flammable and non-toxic at low concentrations, has high hydrogen storage density, and its production, storage, and transportation technologies are mature. Furthermore, hydrogen production is carbon-free, making it a highly efficient, clean, and safe hydrogen carrier. Producing hydrogen by decomposing ammonia is also a feasible and effective hydrogen production technology. However, ammonia is also highly corrosive. It reacts with oxygen and water vapor in the air to produce corrosive substances such as nitric acid and nitrous acid, further exacerbating equipment corrosion. In the application of ammonia decomposition, ammonia is widely used as a raw material for hydrogen production, but due to its corrosiveness, the selection, maintenance, and repair of equipment become particularly important. Therefore, taking effective anti-corrosion measures is crucial to ensuring production safety and extending equipment lifespan. In the prior art, composite materials such as single ceramic coatings or metal-based ceramic composite coatings are used to spray or clad the coating material onto the substrate surface by methods such as thermal spraying or laser cladding to enhance the substrate's resistance to ammonia corrosion. However, existing composite corrosion-resistant coatings have defects such as a large number of pores, a large difference between the coating's thermal conductivity and the substrate's thermal conductivity, and poor bonding strength between the coating and the substrate.

[0003] Chinese patent CN116988025A discloses a high-hardness TiZrNbHfNi amorphous high-entropy alloy thin film. The film incorporates Ni into the TiZrNbHf alloy, and the microstructure is controlled by varying the Ni content, resulting in a high-strength / hardness TiZrNbHfNi high-entropy alloy thin film with an amorphous microstructure. This film is characterized by its dense structure, good adhesion to the substrate, and high hardness, making it suitable for corrosion-resistant coatings. However, this corrosion-resistant coating is composed of a mixture of single elements. Due to the strong corrosiveness of ammonia and the significant variations in operating conditions during actual production, this corrosion-resistant coating cannot simultaneously adapt to the high-temperature environment of ammonia decomposition and the corrosive environment. Summary of the Invention

[0004] To address the shortcomings of existing composite corrosion-resistant coatings, such as numerous pores, significant differences in thermal conductivity between the coating and the substrate, low mechanical strength, and poor bonding strength, which prevent them from simultaneously meeting the environmental requirements for high-temperature resistance and corrosion resistance in ammonia decomposition, this paper provides a composite corrosion-resistant coating suitable for ammonia decomposition, its preparation method, and an ammonia decomposition reactor.

[0005] The technical solution adopted by the present invention to solve its technical problem is: a corrosion-resistant coating for ammonia decomposition, wherein, according to the mass parts of the corrosion-resistant coating for ammonia decomposition, the corrosion-resistant coating for ammonia decomposition comprises 15 parts to 25 parts of zirconium oxide, 15 parts to 25 parts of niobium disilicide, 45 parts to 60 parts of elemental metal, and 5 parts to 10 parts of binder; the binder is polyvinyl alcohol or polyethylene glycol; the corrosion-resistant coating for ammonia decomposition has a particulate structure, and the particle size range of the corrosion-resistant coating for ammonia decomposition is 15 to 45 micrometers.

[0006] Furthermore, the metallic element is any one or more of nickel, tungsten, cobalt, manganese, titanium, or vanadium.

[0007] A method for preparing a corrosion-resistant coating for ammonia decomposition includes the following steps:

[0008] Step 1: Mix solid zirconium oxide with elemental metal, deionized water and binder to obtain a first mixed slurry; mix solid niobium disilicide with elemental metal, deionized water and binder to obtain a second mixed slurry;

[0009] Step 2: Ball mill the first and second mixed slurries from Step 1 respectively; the ball milling time is 10-14 hours for both, and the ball-to-material ratio is 10:1.

[0010] Step 3: The first and second mixed slurries after ball milling are respectively subjected to centrifugal spray drying to obtain the first agglomerated particle group and the second agglomerated particle group after drying.

[0011] Step 4: Heat and calcine the first and second agglomerated particle groups in a vacuum environment for at least 3.5 hours respectively;

[0012] Step 5: Cool the heated first and second agglomerated particle groups to below 90°C, and then ball mill them for 8-10 hours with a ball-to-particle ratio of 8:1 to obtain zirconium oxide composite material and niobium disilicide composite material.

[0013] Step 6: Mix the zirconium oxide composite material, niobium disilicide composite material, binder, and deionized water to obtain a composite slurry;

[0014] Step 7: Ball mill the composite slurry from Step 6 for 10-14 hours; the ball-to-material ratio is 5:1.

[0015] Step 8: The ball-milled composite slurry is centrifuged and spray-dried to obtain composite agglomerated particle groups after drying;

[0016] Step 9: Calcine the composite agglomerated particle group in a vacuum environment for at least 3.5 hours;

[0017] Step 10: Cool the heated composite agglomerated particle group to below 90°C, and then ball mill for 8-10 hours; the ball milling ratio is 8:1; to obtain a corrosion-resistant coating for ammonia decomposition containing zirconium oxide, niobium disilicide and elemental metals.

[0018] Furthermore, in step one, the elemental solid is tungsten or nickel, the binder is polyvinyl alcohol or polyethylene glycol, and the elemental solid, solid zirconium oxide, and solid niobium disilicide are all in powder form. The particle diameter of the elemental solid is larger than that of the solid zirconium oxide and solid niobium disilicide.

[0019] Furthermore, the metallic elemental solid also includes any one or more of cobalt, manganese, titanium, or vanadium; in step two, additives are added during the ball milling process of the first mixed slurry and the ball milling process of the second mixed slurry, respectively, and the additives are ethylene glycol, propylene glycol, or polyacrylic acid.

[0020] Furthermore, in step four, the first agglomerated particle group is heated and calcined through the following steps: first, the temperature is increased from room temperature to 800°C at a heating rate of 10–20°C / min, and then held at 800°C for 20–30 minutes; then, under a pressure of 80–100 MPa, the temperature is increased from 800°C to 1200–1500°C at a heating rate of 20–40°C / min, and then held for 2–3 hours; the second agglomerated particle group is heated and calcined through the following steps: first, the temperature is increased from room temperature to 800°C at a heating rate of 10–20°C / min, and then held at 800°C for 20–30 minutes; then, under a pressure of 80–100 MPa, the temperature is increased from 800°C to 1200–1500°C at a heating rate of 20–40°C / min, and then held for 2–3 hours.

[0021] Furthermore, in step six, the particle sizes of the zirconium oxide composite material and the niobium disilicide composite material are different; in step seven, an additive is added to the mixed zirconium oxide composite material and the niobium disilicide composite material, the additive being ethylene glycol, propylene glycol, or polyacrylic acid.

[0022] Furthermore, in step nine, the composite agglomerated particles are sintered through the following steps: first, the temperature is increased from room temperature to 750°C at a heating rate of 20°C / min, and then held for 15–25 minutes; then, under a pressure of 80–100 MPa, the temperature is increased from 750°C to 1000–1500°C at a heating rate of 10°C / min, and then held for 2–3 hours.

[0023] An ammonia decomposition reactor including a corrosion-resistant coating for ammonia decomposition, comprising a first cover plate, a second cover plate, a spirally arranged ammonia decomposition pipe, and an annular cover plate.

[0024] The first cover plate and the second cover plate are fixed on the upper and lower surfaces of the ammonia decomposition pipeline, respectively. The area of ​​the first cover plate is greater than or equal to the area of ​​the upper surface of the ammonia decomposition pipeline, and the area of ​​the second cover plate is greater than or equal to the area of ​​the lower surface of the ammonia decomposition pipeline. The edges of the first cover plate and the second cover plate are fixedly connected to the annular cover plate. The first cover plate, the second cover plate and the annular cover plate together form a sealed space.

[0025] One end of the ammonia decomposition pipeline is the ammonia decomposition inlet. Starting from the ammonia decomposition inlet, the ammonia decomposition pipeline spirals towards the center of the first cover plate or the center of the second cover plate. The other end of the ammonia decomposition pipeline is the ammonia decomposition outlet. The ammonia decomposition outlet passes through the second cover plate. There are gaps between the adjacent pipe walls of the spirally arranged ammonia decomposition pipeline.

[0026] Furthermore, the first cover plate and the second cover plate are symmetrically arranged. A heating gas inlet is vertically arranged at the center of the first cover plate. The gap between the heating gas inlet and the adjacent pipe wall of the ammonia decomposition pipeline is connected. The heating gas inlet is used to introduce gas with a temperature of above 500°C into the ammonia decomposition reactor. A heating gas outlet is vertically arranged on the part of the first cover plate near the ammonia decomposition inlet. The gap between the heating gas outlet and the adjacent pipe wall of the ammonia decomposition pipeline is connected. The ammonia decomposition pipeline is filled with an ammonia decomposition catalyst.

[0027] Furthermore, the corrosion-resistant coating for ammonia decomposition is located on the inner wall surface of the ammonia decomposition pipeline, and the roughness of the inner wall of the ammonia decomposition pipeline ranges from 45 to 80 μm; the corrosion-resistant coating for ammonia decomposition located on the inner wall of the ammonia decomposition pipeline is a sheet or laminate structure, and the thickness of the corrosion-resistant coating for ammonia decomposition ranges from 0.2 to 0.3 mm.

[0028] Furthermore, the outer wall of the ammonia decomposition pipeline is also coated with a corrosion-resistant coating for ammonia decomposition. The corrosion-resistant coating for ammonia decomposition on the outer wall of the ammonia decomposition pipeline has a sheet or stacked structure, and the thickness of the corrosion-resistant coating for ammonia decomposition on the outer wall of the ammonia decomposition pipeline ranges from 0.2 to 0.3 mm. The corrosion-resistant coating for ammonia decomposition on the outer wall of the ammonia decomposition pipeline contains alumina.

[0029] Furthermore, the corrosion-resistant coating for ammonia decomposition is prepared by a method for preparing a corrosion-resistant coating for ammonia decomposition.

[0030] This invention discloses a corrosion-resistant coating for ammonia decomposition. The process involves mixing a metallic element, such as tungsten, nickel, cobalt, or vanadium, with solid zirconium oxide and niobium disilicide, followed by ball milling, centrifugal atomization drying, sintering, and cooling. This yields a zirconium oxide composite material and a niobium disilicide composite material. These two composite materials are then mixed, followed by ball milling, centrifugal atomization drying, sintering, and cooling. The result is a composite corrosion-resistant coating containing both cermet and metallic elements. This coating exhibits both corrosion resistance and high-temperature resistance, meeting the high-temperature and highly corrosive conditions required for ammonia decomposition. It also possesses good thermal conductivity, facilitating the thermal decomposition of ammonia. During preparation, the mixture of different particle sizes fills the gaps between each other, resulting in a denser coating structure, increased mechanical strength, and consequently, improved service life and reactor protection. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the ammonia decomposition reactor described in this invention;

[0033] Figure 2 This is a schematic diagram of the internal structure assembly of the ammonia decomposition reactor described in this invention;

[0034] Figure 3 This is a schematic diagram of the ammonia decomposition reactor described in this invention from another angle. Detailed Implementation

[0035] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] like Figure 1 As shown, the corrosion-resistant coating for ammonia decomposition according to the present invention, based on the mass parts of the corrosion-resistant coating for ammonia decomposition,

[0037] The corrosion-resistant coating for ammonia decomposition comprises 15 to 25 parts zirconium oxide, 15 to 25 parts niobium disilicide, 45 to 60 parts elemental metal, and 5 to 10 parts binder.

[0038] The adhesive is polyvinyl alcohol or polyethylene glycol;

[0039] The corrosion-resistant coating for ammonia decomposition has a granular structure, and the particle size range of the corrosion-resistant coating for ammonia decomposition is 15 to 45 micrometers.

[0040] The metallic element is any one or more of nickel, tungsten, cobalt, manganese, titanium, or vanadium. The selection of the metallic element depends on the intended use of the corrosion-resistant coating for ammonia decomposition. To adapt to the corrosive and high-temperature environment during ammonia decomposition, preferably, the metallic element is nickel and tungsten, with equal mass fractions of nickel and tungsten. By selecting tungsten and nickel as the metallic elements and mixing them with zirconium oxide and niobium disilicide, the corresponding metallic properties of tungsten and nickel are utilized to create a coating that simultaneously possesses high-temperature resistance and corrosion resistance, thus better adapting to the high-temperature and highly corrosive decomposition environment of ammonia. To further improve the performance of the coating... More preferably, the metallic element further includes cobalt, titanium, manganese, and vanadium to improve the performance and strength of the corrosion-resistant coating against ammonia decomposition. By adding cobalt, titanium, manganese, and vanadium elements and mixing them with zirconium oxide and niobium disilicide, the coating grain structure can be refined, resulting in a denser internal structure and improved coating strength and service life. Specifically, when the metallic element contains cobalt, titanium, manganese, and vanadium, the total mass of cobalt, titanium, manganese, and vanadium is less than the mass of nickel or tungsten. The specific mass of each element (cobalt, titanium, manganese, and vanadium) is adjusted according to the actual ammonia decomposition environment to better adapt to ammonia decomposition. Preferably, the mass fractions of cobalt, titanium, manganese, and vanadium are equal.

[0041] To improve the high-temperature oxidation resistance and high-temperature corrosion resistance of the corrosion-resistant coating for ammonia decomposition, more preferably, the corrosion-resistant coating for ammonia decomposition further includes alumina; when the corrosion-resistant coating for ammonia decomposition includes alumina, its composition is: 15 parts to 25 parts zirconium oxide, 15 parts to 25 parts niobium disilicide, 35 parts to 50 parts elemental metal, 5 parts to 10 parts binder, and the remainder is alumina.

[0042] This application also discloses a method for preparing the corrosion-resistant coating for ammonia decomposition, comprising the following steps;

[0043] Step 1: Mix solid zirconium oxide with elemental metal, deionized water and binder to obtain a first mixed slurry; mix solid niobium disilicide with elemental metal, deionized water and binder to obtain a second mixed slurry;

[0044] Step 2: Ball mill the first and second mixed slurries separately; the ball milling time for both is 10-14 hours, and the ball-to-material ratio for both is 10:1;

[0045] Step 3: The first and second mixed slurries after ball milling are centrifuged and spray-dried respectively to obtain the first agglomerated particle group and the second agglomerated particle group respectively.

[0046] Step 4: Heat and calcine the first and second agglomerated particle groups in a vacuum environment for at least 3.5 hours respectively;

[0047] Step 5: Cool the heated first and second agglomerated particle groups to below 90°C, and then ball mill them for 8-10 hours with a ball-to-particle ratio of 8:1 to obtain zirconium oxide composite material and niobium disilicide composite material.

[0048] Step 6: Mix the zirconium oxide composite material, niobium disilicide composite material, binder, and deionized water to obtain a composite slurry;

[0049] Step 7: Ball mill the composite slurry from Step 6 for 10-14 hours at a ball-to-material ratio of 5:1.

[0050] Step 8: The ball-milled composite slurry is centrifuged and spray-dried to obtain composite agglomerated particle groups after drying;

[0051] Step 9: Calcine the composite agglomerated particle group in a vacuum environment for at least 3.5 hours;

[0052] Step 10: Cool the heated composite agglomerated particle group to below 90°C, and then ball mill for 8-10 hours; the ball-to-material ratio is 8:1 to obtain a corrosion-resistant coating for ammonia decomposition containing zirconium oxide, niobium disilicide and elemental metals.

[0053] In step one, solid zirconium oxide is mixed with a solid metallic element, such as tungsten or nickel, deionized water, and a binder, wherein the binder is polyvinyl alcohol or polyethylene glycol; specifically, the mass ratio of solid zirconium oxide to the solid metallic element is 1:1 to 3:7. Solid niobium disilicide is also mixed with a solid metallic element, such as tungsten or nickel, deionized water, and a binder, wherein the binder is polyvinyl alcohol or polyethylene glycol, and the mass ratio of solid niobium disilicide to the solid metallic element is 1:1 to 3:7. To improve the overall versatility of the prepared corrosion-resistant coating for ammonia decomposition, enabling the coating to possess corrosion resistance and high-temperature resistance while promoting ammonia decomposition efficiency, preferably, the metallic element bonded to the solid zirconium oxide and the metallic element bonded to the solid niobium disilicide are different. Simultaneously, to improve the preparation efficiency of the corrosion-resistant coating for ammonia decomposition and promote more complete and thorough mixing of zirconium oxide and niobium disilicide with the corresponding metallic element, specifically, the solid zirconium oxide has a powdered granular structure, and the niobium disilicide has a powdered granular structure. The coating has a granular structure; the metallic element, such as tungsten or nickel, mixed with solid zirconium oxide and niobium disilicide has a powdery granular structure; wherein the particle diameter of the metallic element is larger than that of zirconium oxide and niobium disilicide, with the particle diameter of the metallic element ranging from 25 to 35 μm, the diameter of zirconium oxide ranging from 15 to 25 μm, and the particle diameter of niobium disilicide ranging from 15 to 25 μm; by adding deionized water to zirconium oxide and metallic elements, and to niobium disilicide and metallic elements, the bonding effect between the binder and the solid particles can be promoted, allowing the solid particles to be more tightly bonded; in step one, zirconium oxide and niobium disilicide are mixed with metallic elements, such as tungsten or nickel, to prepare a corrosion-resistant coating. Since zirconium oxide and niobium disilicide are both metal-ceramic materials, the resulting corrosion-resistant coating has the characteristics of both metal and ceramic materials. Combined with the mixed metallic element, the thermal conductivity and strength of the coating can also be improved, allowing ammonia to be heated better while reducing the damage to the equipment caused by ammonia decomposition.

[0054] To enhance the functional versatility of the coating and enable it to better adapt to complex ammonia decomposition environments, preferably, the metallic element also includes one or more of cobalt, manganese, titanium, or vanadium. By mixing the aforementioned metallic element, such as cobalt, manganese, titanium, or vanadium, with solid zirconium oxide or solid niobium disilicide, and combining the individual metallic properties of cobalt, manganese, titanium, or vanadium, the grain size can be refined and the overheating sensitivity of the coating can be reduced, resulting in a denser internal structure and thus improving the mechanical strength, toughness, and service life of the coating. When the metallic element includes one or more of cobalt, manganese, titanium, or vanadium, the sum of the mass fractions of nickel and tungsten is greater than the sum of the mass fractions of cobalt, manganese, titanium, and vanadium, making it suitable for use in ammonia decomposition. The decomposed corrosion-resistant coating possesses sufficient corrosion resistance and high-temperature resistance, while also exhibiting good mechanical strength. More preferably, when the metallic element includes any one or more of cobalt, manganese, titanium, or vanadium, the mass fractions of cobalt, manganese, titanium, and vanadium are adjusted according to actual production conditions. To further improve the coating's resistance to high-temperature oxidation and corrosion, in step one, alumina is mixed with solid zirconium oxide, the solid metallic element, deionized water, and a binder; alumina is also mixed with solid niobium disilicide, the solid metallic element, deionized water, and a binder. By adding alumina to the first and second mixed slurries, the coating's high-temperature oxidation resistance and high-temperature corrosion resistance can be further improved.

[0055] In step two, the first and second mixed slurries obtained in step one are ball-milled respectively, with a ball milling speed of 300-320 r / min and a ball milling time of 10-14 hours; and a ball-to-material ratio of 10:1; so that the first and second mixed slurries can be fully and uniformly ground. In order to improve the ball milling efficiency and effect, preferably, an additive, such as ethylene glycol, propylene glycol or polyacrylic acid, is added to the first and second mixed slurries respectively during the grinding process to improve the mixing effect between solid zirconium oxide and solid niobium disilicide and the corresponding metal elements in the first and second mixed slurries, so that solid zirconium oxide and solid niobium disilicide and the corresponding metal elements can be fully and uniformly mixed and ground during the grinding process.

[0056] In step three, the first and second mixed slurries after ball milling are respectively subjected to centrifugal spray drying. The temperature range of the centrifugal spray drying is controlled between 220 and 260°C, and the centrifugal speed range is between 5000 and 20000 r / min. The centrifugal spray drying process converts the first and second mixed slurries into first and second agglomerated particles, respectively. Both the first and second agglomerated particles have good sphericity, for example, 0.7 to 0.9, and there are gaps between the individual particles of both types, resulting in a low bulk density. Therefore... The final coating exhibits good fluidity during application, allowing the overall functions of the prepared coating, such as corrosion resistance and high-temperature resistance, to be uniformly distributed with the thickness distribution. This reduces the defects of uneven coating effect after coating and improves the overall quality and effect of the coating. Similarly, by using centrifugal spray to dry the mixed slurry, compared with ordinary drying methods, the sphericity of the prepared agglomerated particles can reach 0.7-0.9. Moreover, there are uniform gaps between the particles, resulting in good fluidity. This allows the components of the coating to be uniformly distributed during the spraying process, improving the overall function of the coating.

[0057] In step four, the first and second agglomerated particle groups are sintered in a vacuum environment filled with protective gas. The sintering process for the first agglomerated particle group is divided into a first heating stage and a second heating stage with different heating parameters. In the first heating stage, the temperature is increased from room temperature to 800°C at a rate of 10–20°C / min, and then held at 800°C for 20–30 minutes. By gradually increasing the temperature in a vacuum environment at a stable heating rate during the first heating stage, a fixed temperature is achieved. Holding the sintering temperature at 800℃ for 20–30 minutes allows migration and diffusion between the agglomerated particles in the initial heating stage, increasing the bonding surface between particles and making the agglomerated particles more tightly bound, thus improving the stability of the agglomerated particles and enhancing their bonding strength. Simultaneously, gradually and steadily increasing the sintering temperature at a certain rate, such as 10–20℃ / min, ensures uniform heating and sintering of the agglomerated particles, reducing size and shape inhomogeneities caused by localized sintering and inhibiting grain growth between the agglomerated particles. This process improves the density of agglomerated particles. Furthermore, holding the particles at a certain temperature, such as 800℃, after sintering promotes particle transport and diffusion, increases the contact area between agglomerated particles, and further promotes particle fusion, resulting in more regular and uniform shapes. In the second heating stage, the temperature is gradually increased from 800℃ to 1200-1500℃ at a rate of 20-40℃ / min under a pressure of 80-100 MPa, followed by holding for 2-3 hours. By adding pressure, such as 80-100 MPa, and heating the agglomerated particles at a rate greater than that of the first heating stage, the migration and diffusion between agglomerated particles can be further promoted, increasing particle compactness. Applying pressure also allows for uniform adjustment of the shape and size of the agglomerated coating, further improving the uniformity of the sintered agglomerated particles' appearance. This is beneficial for improving the density, hardness, and toughness of subsequent coating materials, while also reducing defects in the subsequent coating preparation process and ensuring a more uniform and stable distribution of the coating on the carrier surface during spraying.

[0058] In the heating and sintering of the second agglomerated particle group, the heating and sintering process is also divided into a first heating stage and a second heating stage. In the first heating stage, the temperature is raised from room temperature to 500℃ at a constant heating rate of 20℃ / min, and then held at 500℃ for 20 to 25 minutes. In the second heating stage, under a pressure environment of 80 to 100 MPa, the temperature is gradually raised from 500℃ to 700 to 1000℃ at a constant heating rate of 10℃ / min, and then held at 500℃ for 2 to 3 hours.

[0059] By performing segmented heat preservation and sintering on the first and second agglomerated particle groups in combination with the material's performance characteristics, temperature gradients during sintering can be prevented, and stress generated inside the agglomerated particles during sintering can be removed, reducing problems such as cracks or deformation caused by stress during sintering. Furthermore, by preheating and sintering the agglomerated particles first, the porosity between the particles inside the agglomerated particles is reduced, and then the shape of the agglomerated particles is further adjusted by combining pressure and temperature, thereby improving the uniformity and compactness of the agglomerated particle structure.

[0060] In step five, the first and second agglomerated particle groups, after being heated and calcined, are cooled to below 90°C. After cooling, they are ball-milled for 8–10 hours at a ball-to-particle ratio of 8:1 to further increase the particle size range and reduce the porosity of the agglomerated particles. Zirconia composite material and niobium disilicide composite material are obtained respectively. The particle size range of the zirconia composite material is 15–45 μm, and the porosity is 2–5%. The particle size range of the niobium disilicide composite material is 15–45 μm, and the porosity is 2–5%.

[0061] In step six, the zirconia composite material and niobium disilicide composite material obtained in step five are mixed with a binder, such as polyvinyl alcohol or polyethylene glycol, and deionized water to obtain a composite slurry. The mass ratio of the zirconia composite material to the niobium disilicide composite material is adjusted according to the actual production conditions to meet the requirements of high temperature resistance, corrosion resistance, and coating mechanical strength under different ammonia decomposition conditions. Preferably, the mass ratio of the zirconia composite material to the niobium disilicide composite material is 1:1.

[0062] In step seven, the mixed zirconia composite material and niobium disilicide composite material are ball-milled at a speed of 300–320 r / min for 10–14 hours with a ball-to-material ratio of 5:1. To improve the ball-milling efficiency and effect, preferably, an additive, such as ethylene glycol, propylene glycol, or polyacrylic acid, is added to the mixed zirconia composite material and niobium disilicide composite material during the grinding process. This allows the zirconia composite material and niobium disilicide composite material to be fully and uniformly mixed and ground during the grinding process, promoting the fusion between the two composite materials.

[0063] Because the first agglomerated particle group, composed of solid zirconium oxide and metallic elements, and the second agglomerated particle group, composed of solid niobium disilicide and metallic elements, are ball-milled, calcined, and cooled and dried separately, and because zirconium oxide, niobium disilicide, and the mixed metallic elements are different from each other and have different physical properties, especially different toughness and hardness, the zirconium oxide composite material and niobium disilicide composite material obtained in step six have different particle sizes; therefore, after mixing and ball-milling the zirconium oxide composite material and niobium disilicide composite material with different particle sizes, the zirconium oxide composite material and niobium disilicide composite material can fill the gaps between each other, reducing the gaps between the materials after ball milling, so that the final coating has better mechanical strength and density.

[0064] In step eight, the ball-milled zirconia composite material and niobium disilicide composite material are subjected to centrifugal spray drying. The temperature range of the centrifugal spray drying is controlled within 220–260°C, and the centrifugal speed range is 5000–20000 r / min. The mixture composed of zirconia composite material and niobium disilicide composite material is dried by centrifugal spray drying to obtain a composite agglomerated particle group. After centrifugal spray drying, the composite agglomerated particle group has better sphericity, for example, greater than 0.9, and there are smaller gaps between the particles of the mixed material composed of zirconia composite material and niobium disilicide composite material, resulting in a smaller looseness. The density of the coating increases, resulting in better fluidity during application. This allows the overall functionality of the coating, such as corrosion resistance and high-temperature resistance, to be evenly distributed with the thickness distribution, improving the overall quality and effect of the coating. Similarly, by using centrifugal spraying to dry the composite agglomerates, the sphericity of the agglomerates can reach over 0.9 compared to ordinary drying methods. Furthermore, the gaps between the particles are more uniform, resulting in better fluidity. This allows the components of the coating to be evenly distributed during the spraying process, improving the overall functionality of the coating and reducing the defects of uneven functional distribution.

[0065] In step nine, the composite agglomerated particle group is heated and sintered in a vacuum environment filled with protective gas. Similarly, the heating and sintering process is divided into a first sintering stage and a second sintering stage. In the first sintering stage, the temperature is increased from room temperature to 750°C at a heating rate of 20°C / min, and then held for 15–25 minutes, for example, 20 minutes. This allows migration and diffusion between the particles in the composite agglomerated particle group to continue in the initial heating stage, further tightening the bond between the agglomerated particles, improving the stability of the agglomerated particles, and enhancing their bonding strength. In the second sintering stage, under a pressure of 80–100 MPa, the temperature is gradually increased from 750°C to 1000–1500°C at a heating rate of 10°C / min, and then held for 2–3 hours. By adding pressure in the second sintering stage, the migration and diffusion between the particles in the agglomerated particles are further enhanced, while the final shape and size of the composite agglomerated coating are uniformly adjusted, further improving the appearance uniformity of the sintered agglomerated particles and the density, hardness, and toughness of the subsequent coating material.

[0066] In step ten, the heated and calcined composite agglomerated particle group is cooled to below 90°C, and then ball-milled for 8-10 hours at a ball-to-particle ratio of 8:1 to further increase the particle size range and reduce the porosity of the composite agglomerated particle group; a corrosion-resistant coating for ammonia decomposition containing zirconium oxide and niobium disilicide is obtained, wherein the particle size range of the corrosion-resistant coating for ammonia decomposition containing zirconium oxide and niobium disilicide is 15-45 μm.

[0067] The preparation method of the corrosion-resistant coating for ammonia decomposition will be further explained below with reference to the embodiments.

[0068] Example 1

[0069] Step 1: Mix solid zirconium oxide with solid nickel metal, deionized water, and polyvinyl alcohol to obtain a first mixed slurry, with a mass ratio of solid zirconium oxide to solid nickel metal of 1:1; mix solid niobium disilicide with solid tungsten metal, deionized water, and polyvinyl alcohol to obtain a second mixed slurry, with a mass ratio of solid niobium disilicide to solid tungsten metal of 1:1. The particle diameter of the solid tungsten metal is 25 μm, the particle diameter of the solid nickel metal is 25 μm, the particle diameter of the solid zirconium oxide is 15 μm, and the particle diameter of the solid niobium disilicide is 15 μm.

[0070] Step 2: Ball mill the first and second mixed slurries from Step 1 respectively, and add ethylene glycol to the first mixed slurry and propylene glycol to the second mixed slurry; the ball milling time is 10 hours for both, the ball-to-material ratio is 10:1, and the ball milling speed is 300 r / min.

[0071] Step 3: The first and second mixed slurries after ball milling are respectively subjected to centrifugal spray drying at a temperature of 220℃ and a centrifugal speed of 5000r / min. After drying, the first agglomerated particle group and the second agglomerated particle group are obtained respectively.

[0072] Step 4: Place the first agglomerated particles in a vacuum environment filled with protective gas, and first heat them from room temperature to 800°C at a heating rate of 10°C / min, and hold them at 800°C for 20 minutes; then, under a pressure of 80 MPa, gradually heat them from 800°C to 1200°C at a heating rate of 20°C / min, and then hold them at 1200°C for 2 hours.

[0073] The second agglomerated particles were placed in a vacuum environment filled with protective gas. The temperature was first increased from room temperature to 500°C at a constant heating rate of 20°C / min, and then held at 500°C for 20 minutes. Then, under a pressure of 80 MPa, the temperature was gradually increased from 500°C to 700°C at a constant heating rate of 10°C / min, and then held at 700°C for 2 hours.

[0074] Step 5: Cool the heated first and second agglomerated particle groups to below 90°C. After cooling, ball mill the first agglomerated particle group at a ball-to-particle ratio of 8:1 for 8 hours to obtain zirconia composite material; ball mill the second agglomerated particle group at a ball-to-particle ratio of 8:1 for 8 hours to obtain niobium disilicide composite material.

[0075] Step 6: Mix the zirconia composite material, niobium disilicide composite material, polyvinyl alcohol, and deionized water to obtain a composite slurry; the mass ratio of the zirconia composite material to the niobium disilicide composite material is 1:1.

[0076] Step 7: Add propylene glycol additive to the composite slurry, then ball mill at 300 r / min for 10 hours with a ball-to-material ratio of 5:1.

[0077] Step 8: The ball-milled composite slurry is centrifugally spray-dried at 220℃ with a centrifugation speed of 5000 r / min to obtain composite agglomerated particle groups;

[0078] Step 9: In a vacuum environment filled with protective gas, the composite agglomerated particles are heated from room temperature to 750°C at a heating rate of 20°C / min, and then held at that temperature for 15 minutes; then, under a pressure of 80 MPa, the temperature is gradually increased from 750°C to 1000°C at a heating rate of 10°C / min, and then held at that temperature for 2 hours.

[0079] Step 10: Cool the heated composite agglomerated particle group to below 90°C, and then ball mill it for 8 hours at a ball-to-particle ratio of 8:1; to obtain a corrosion-resistant coating for ammonia decomposition containing zirconium oxide, niobium disilicide, tungsten metal and nickel metal, wherein the porosity of the corrosion-resistant coating for ammonia decomposition containing zirconium oxide, niobium disilicide, tungsten metal and nickel metal is 3%.

[0080] Example 2

[0081] Step 1: Mix solid zirconium oxide with solid tungsten metal, deionized water, and polyethylene glycol to obtain a first mixed slurry, with a mass ratio of solid zirconium oxide to solid tungsten metal of 1:1; mix solid niobium disilicide with solid nickel metal, deionized water, and polyethylene glycol to obtain a second mixed slurry, with a mass ratio of solid niobium disilicide to solid nickel metal of 1:1. The particle diameters of the solid tungsten metal, solid nickel metal, solid zirconium oxide, and solid niobium disilicide are all 35 μm and 35 μm respectively.

[0082] Step 2: Ball mill the first and second mixed slurries from Step 1 respectively, and add propylene glycol to the first mixed slurry and polyacrylic acid to the second mixed slurry; the ball milling time is 14 hours for both, the ball-to-material ratio is 10:1, and the ball milling speed is 320 r / min.

[0083] Step 3: The first and second mixed slurries after ball milling are respectively subjected to centrifugal spray drying at a temperature of 260℃ and a centrifugal speed of 20000r / min. After drying, the first agglomerated particle group and the second agglomerated particle group are obtained respectively.

[0084] Step 4: Place the first agglomerated particles in a vacuum environment filled with protective gas, and first heat the temperature from room temperature to 800°C at a heating rate of 20°C / min, and hold it at 800°C for 30 minutes; then, under a pressure of 100 MPa, gradually heat the temperature from 800°C to 1200°C at a heating rate of 40°C / min, and then hold it at 1200°C for 3 hours.

[0085] The second agglomerated particles were placed in a vacuum environment filled with protective gas. The temperature was first increased from room temperature to 500°C at a constant heating rate of 20°C / min, and then held at 500°C for 25 minutes. Then, under a pressure of 100 MPa, the temperature was gradually increased from 500°C to 1000°C at a constant heating rate of 10°C / min, and then held at 1000°C for 3 hours.

[0086] Step 5: Cool the heated first and second agglomerated particle groups to below 90°C. After cooling, ball mill the first agglomerated particle group at a ball-to-particle ratio of 8:1 for 10 hours to obtain zirconia composite material; ball mill the second agglomerated particle group at a ball-to-particle ratio of 8:1 for 10 hours to obtain niobium disilicide composite material.

[0087] Step 6: Mix the zirconia composite material, niobium disilicide composite material, polyethylene glycol, and deionized water to obtain a composite slurry; the mass ratio of the zirconia composite material to the niobium disilicide composite material is 1:1.

[0088] Step 7: Add ethylene glycol additive to the composite slurry, and then ball mill at 320 r / min for 10 hours with a ball-to-material ratio of 5:1.

[0089] Step 8: The ball-milled composite slurry is centrifugally spray-dried at 260℃ with a centrifugal speed of 20000 r / min to obtain composite agglomerated particle groups;

[0090] Step 9: In a vacuum environment filled with protective gas, the composite agglomerated particles are heated from room temperature to 750°C at a heating rate of 20°C / min, and then held at that temperature for 25 minutes; then, under a pressure of 100 MPa, the temperature is gradually increased from 750°C to 1500°C at a heating rate of 10°C / min, and then held at that temperature for 3 hours.

[0091] Step 10: Cool the heated composite agglomerated particle group to below 90°C, and then ball mill it for 10 hours at a ball-to-particle ratio of 8:1; to obtain a corrosion-resistant coating for ammonia decomposition containing zirconium oxide, niobium disilicide, tungsten metal and nickel metal; the porosity of the corrosion-resistant coating for ammonia decomposition containing zirconium oxide, niobium disilicide, tungsten metal and nickel metal is 3%.

[0092] Example 3

[0093] Step 1: Mix solid zirconium oxide with solid tungsten metal, solid cobalt metal, deionized water, and polyethylene glycol to obtain a first mixed slurry. The mass ratio of solid zirconium oxide to solid tungsten metal and solid cobalt metal is 1:0.5:0.5. Mix solid niobium disilicide with solid nickel metal, solid titanium metal, deionized water, and polyvinyl alcohol to obtain a second mixed slurry. The mass ratio of solid niobium disilicide to solid nickel metal and solid titanium metal is 1:0.5:0.5. The particle diameters of the solid tungsten metal, solid nickel metal, solid cobalt metal, and solid titanium metal are all 30 μm, while the particle diameters of the solid zirconium oxide and solid niobium disilicide are all 20 μm.

[0094] Step 2: The first and second mixed slurries from Step 1 are ball-milled separately, and ethylene glycol is added to the first mixed slurry and propylene glycol is added to the second mixed slurry; the ball milling time is 12 hours for both, the ball-to-material ratio is 10:1, and the ball milling speed is 310 r / min.

[0095] Step 3: The first and second mixed slurries after ball milling are respectively subjected to centrifugal spray drying at a temperature of 240℃ and a centrifugal speed of 10000r / min. After drying, the first agglomerated particle group and the second agglomerated particle group are obtained respectively.

[0096] Step 4: Place the first agglomerated particles in a vacuum environment filled with protective gas, and first heat the temperature from room temperature to 800°C at a heating rate of 15°C / min, and hold it at 800°C for 25 minutes; then, under a pressure of 90 MPa, gradually heat the temperature from 800°C to 1400°C at a heating rate of 35°C / min, and then hold it at 1400°C for 2.5 hours.

[0097] The second agglomerated particles were placed in a vacuum environment filled with protective gas. The temperature was first increased from room temperature to 500°C at a constant heating rate of 20°C / min, and then held at 500°C for 25 minutes. Then, under a pressure of 100 MPa, the temperature was gradually increased from 500°C to 1000°C at a constant heating rate of 10°C / min, and then held at 1000°C for 3 hours.

[0098] Step 5: Cool the heated first and second agglomerated particle groups to below 90°C. After cooling, ball mill the first agglomerated particle group at a ball-to-particle ratio of 8:1 for 9 hours to obtain zirconia composite material; ball mill the second agglomerated particle group at a ball-to-particle ratio of 8:1 for 9 hours to obtain niobium disilicide composite material.

[0099] Step 6: Mix the zirconia composite material, niobium disilicide composite material, polyvinyl alcohol, and deionized water to obtain a composite slurry; the mass ratio of the zirconia composite material to the niobium disilicide composite material is 1:1.

[0100] Step 7: Add propylene glycol additive to the composite slurry, and then ball mill at 310 r / min for 12 hours with a ball-to-material ratio of 5:1.

[0101] Step 8: The ball-milled composite slurry is centrifugally spray-dried at 240℃ with a centrifugal speed of 10000 r / min to obtain composite agglomerated particle groups;

[0102] Step 9: In a vacuum environment filled with protective gas, the composite agglomerated particles are heated from room temperature to 750°C at a heating rate of 20°C / min, and then held at that temperature for 20 minutes; then, under a pressure of 90 MPa, the temperature is gradually increased from 750°C to 1200°C at a heating rate of 10°C / min, and then held at that temperature for 2.5 hours.

[0103] Step 10: Cool the heated composite agglomerated particle group to below 90°C, and then ball mill it for 9 hours at a ball-to-particle ratio of 8:1; to obtain a corrosion-resistant coating for ammonia decomposition containing zirconium oxide, niobium disilicide, tungsten metal, nickel metal, cobalt metal, and titanium metal; the porosity of the corrosion-resistant coating for ammonia decomposition containing zirconium oxide, niobium disilicide, tungsten metal, nickel metal, cobalt metal, and titanium metal is 1%.

[0104] like Figures 1-3 As shown, this application also discloses an ammonia decomposition reactor including the aforementioned corrosion-resistant coating for ammonia decomposition, comprising a first cover plate 1, a second cover plate 2, a spirally arranged ammonia decomposition pipe 3, and an annular cover plate 4.

[0105] The first cover plate 1 and the second cover plate 2 are respectively fixed to the upper and lower surfaces of the ammonia decomposition pipe 3. The area of ​​the first cover plate 1 is greater than or equal to the area of ​​the upper surface of the ammonia decomposition pipe 3, and the area of ​​the second cover plate 2 is greater than or equal to the area of ​​the lower surface of the ammonia decomposition pipe 3. The edges of the first cover plate 1 and the second cover plate 2 are fixedly connected to the annular cover plate 4. The first cover plate 1, the second cover plate 2 and the annular cover plate 4 together form a sealed space.

[0106] One end of the ammonia decomposition pipe 3 is the ammonia decomposition inlet 31. The ammonia decomposition pipe 3 extends spirally from the ammonia decomposition inlet 31 toward the center of the first cover plate 1 or the center of the second cover plate 2. The other end of the ammonia decomposition pipe 3 is the ammonia decomposition outlet 32. The ammonia decomposition outlet 32 ​​passes through the second cover plate 2. There are gaps between adjacent pipe walls of the spirally arranged ammonia decomposition pipe 3.

[0107] In this design, the gaps between adjacent pipe walls of the ammonia decomposition pipe 3 are used for gas flow. The first cover plate 1 and the second cover plate 2 are symmetrically arranged. A heating gas inlet 5 is vertically positioned at the center of the first cover plate 1, communicating with the gaps between adjacent pipe walls of the ammonia decomposition pipe 3. The heating gas inlet 5 is used to introduce gas at temperatures above 500°C, such as air, into the ammonia decomposition reactor, which contains a corrosion-resistant coating for ammonia decomposition. Because the ammonia decomposition pipe 3 is spirally arranged, when gas at temperatures above 500°C enters the gaps between adjacent pipe walls of the ammonia decomposition pipe 3 through the heating gas inlet 5, the gas can flow along the gaps between the adjacent pipe walls of the ammonia decomposition pipe 3. The gas flows spirally within the gap between adjacent pipe walls of the ammonia decomposition pipe 3 in the extending direction. During the spiral flow, the heat of the gas at a temperature above 500°C is transferred through the pipe wall of the ammonia decomposition pipe 3 to the ammonia gas located inside the ammonia decomposition pipe 3, thereby heating the ammonia gas and promoting its thermal decomposition. Furthermore, a heating gas outlet 6 is vertically arranged on the first cover plate 1 near the ammonia decomposition inlet 31. The heating gas outlet 6 communicates with the gap between the adjacent pipe wall of the ammonia decomposition pipe 3 and the gas after heating the ammonia gas is discharged through the heating gas outlet 6, thus completing the heating of the ammonia gas. The ammonia decomposition pipe 3 is filled with an ammonia decomposition catalyst, such as a ruthenium-based catalyst or a nickel-based catalyst.

[0108] To improve the corrosion resistance to ammonia during ammonia decomposition and extend the service life of the equipment, the inner wall surface of the ammonia decomposition pipe 3 is uniformly coated with the corrosion-resistant coating for ammonia decomposition. To enhance the bonding strength between the coating and the inner wall of the ammonia decomposition pipe 3 and better reduce the corrosive effect of ammonia on the pipe 3, specifically, the inner wall of the ammonia decomposition pipe 3 is roughened by sandblasting, resulting in a roughness of 45–80 μm. The corrosion-resistant coating for ammonia decomposition is applied to the inner wall of the ammonia decomposition pipe 3 by plasma spraying. During the spraying process, the distance between the spraying equipment and the inner wall of the ammonia decomposition pipe 3 is 90-110 mm, and the corrosion-resistant coating for ammonia decomposition is sprayed onto the inner wall of the ammonia decomposition pipe 3 at a spraying speed of 150-500 m / s. The corrosion-resistant coating for ammonia decomposition is in a molten or semi-molten state. After spraying, the corrosion-resistant coating for ammonia decomposition on the inner wall of the ammonia decomposition pipe 3 is a sheet or laminate structure, and the thickness of the corrosion-resistant coating for ammonia decomposition is 0.2-0.3 mm.

[0109] Preferably, in order to improve the heat exchange effect between the heating gas and ammonia, the outer wall of the ammonia decomposition pipe 3 is also coated with the corrosion-resistant coating for ammonia decomposition. The corrosion-resistant coating for ammonia decomposition on the outer wall of the ammonia decomposition pipe 3 has a sheet or stacked structure, and the thickness of the corrosion-resistant coating for ammonia decomposition on the outer wall of the ammonia decomposition pipe 3 ranges from 0.2 to 0.3 mm. Since the gaps between the spirally arranged ammonia decomposition pipes 3 are used for the flow of gas above 500°C, the corrosion-resistant coating for ammonia decomposition sprayed on the outer wall of the ammonia decomposition pipe 3 contains alumina to improve the high-temperature oxidation resistance of the coating.

[0110] Furthermore, the corrosion-resistant coatings for ammonia decomposition prepared through Examples 1-3 were applied to the inner and outer walls of the ammonia decomposition pipes 3 of three different ammonia decomposition reactors, respectively, and cured at room temperature. After curing, ammonia gas was introduced through the ammonia decomposition inlet 31, and air at 500°C was introduced through the heating gas inlet 5; wherein the ammonia gas flow rate was 120-140 m / s; the air flow rate was 120-140 m / s; the ammonia decomposition outlet 32 ​​was connected to a chromatograph to detect the ammonia decomposition efficiency; after a fixed reaction time, for example 1-2 hours, the corrosion condition of the inner surface of the ammonia decomposition pipe 3 and the coating adhesion condition of the inner and outer walls of the ammonia decomposition pipe 3 were observed; the test results are as follows:

[0111]

[0112]

[0113] Therefore, it can be seen that, after reactors 3, 4, and 5, coated with the corrosion-resistant coatings for ammonia decomposition prepared in Examples 1-3, were purged with ammonia gas at a flow rate of 120-140 m / s and air at a temperature above 500°C, no rust caused by ammonia gas was observed on the inner side of the ammonia decomposition pipe compared to reactor 1 without a coating and reactor 2 with only a single metal corrosion-resistant coating. Furthermore, no coating peeling was observed on the inner and outer walls of the ammonia decomposition pipe after purging with ammonia gas and air. This indicates that the corrosion-resistant coatings for ammonia decomposition prepared in Examples 1-3 not only have good corrosion resistance but also good adhesion strength to the ammonia decomposition pipe. Similarly, since the coatings prepared in Examples 1-3 fuse elemental metals, especially catalytically active nickel metal, with cermet, heat transfer is facilitated, thus promoting the heating and decomposition of ammonia gas in the ammonia decomposition environment, thereby effectively improving the ammonia decomposition efficiency.

[0114] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A corrosion-resistant coating for ammonia decomposition, characterized in that, Based on the mass fraction of the corrosion-resistant coating used for ammonia decomposition, The corrosion-resistant coating for ammonia decomposition comprises 15 to 25 parts zirconium oxide, 15 to 25 parts niobium disilicide, 45 to 60 parts elemental metal, and 5 to 10 parts binder. The adhesive is polyvinyl alcohol or polyethylene glycol; The corrosion-resistant coating for ammonia decomposition has a particulate structure, and the particle size range of the corrosion-resistant coating for ammonia decomposition is 15 to 45 micrometers. The method for preparing the corrosion-resistant coating for ammonia decomposition includes the following steps: Step 1: Mix solid zirconium oxide with elemental metal, deionized water and binder to obtain a first mixed slurry; mix solid niobium disilicide with elemental metal, deionized water and binder to obtain a second mixed slurry; Step 2: Ball mill the first and second mixed slurries from Step 1 respectively; the ball milling time is 10-14 hours for both, and the ball-to-material ratio is 10:

1. Step 3: The first and second mixed slurries after ball milling are respectively subjected to centrifugal spray drying to obtain the first agglomerated particle group and the second agglomerated particle group after drying. Step 4: Heat and calcine the first and second agglomerated particle groups in a vacuum environment for at least 3.5 hours respectively; Step 5: Cool the heated first and second agglomerated particle groups to below 90°C, and then ball mill them for 8-10 hours with a ball-to-particle ratio of 8:1 to obtain zirconium oxide composite material and niobium disilicide composite material. Step 6: Mix the zirconium oxide composite material, niobium disilicide composite material, binder, and deionized water to obtain a composite slurry; Step 7: Ball mill the composite slurry from Step 6 for 10-14 hours; the ball-to-material ratio is 5:

1. Step 8: The ball-milled composite slurry is centrifuged and spray-dried to obtain composite agglomerated particle groups after drying; Step 9: Calcine the composite agglomerated particle group in a vacuum environment for at least 3.5 hours; Step 10: Cool the heated composite agglomerated particle group to below 90°C, and then ball mill for 8-10 hours; the ball milling ratio is 8:1; to obtain a corrosion-resistant coating for ammonia decomposition containing zirconium oxide, niobium disilicide and elemental metals.

2. The corrosion-resistant coating for ammonia decomposition according to claim 1, characterized in that: In step one, the elemental solid metal is tungsten or nickel, the binder is polyvinyl alcohol or polyethylene glycol, and the elemental solid metal, the solid zirconium oxide, and the solid niobium disilicide are all in powder form. The particle diameter of the elemental solid metal is larger than that of the solid zirconium oxide and the solid niobium disilicide.

3. The corrosion-resistant coating for ammonia decomposition according to claim 2, characterized in that: The metallic elemental solid also includes any one or more of cobalt, manganese, titanium, or vanadium; in step two, an additive is added during the ball milling process of the first mixed slurry and the ball milling process of the second mixed slurry, and the additive is ethylene glycol, propylene glycol, or polyacrylic acid.

4. The corrosion-resistant coating for ammonia decomposition according to claim 1, characterized in that: In step four, The first agglomerated particle group is heated and calcined through the following steps: first, the temperature is increased from room temperature to 800°C at a heating rate of 10-20°C / min, and then held at 800°C for 20-30 minutes; then, under a pressure of 80-100 MPa, the temperature is increased from 800°C to 1200-1500°C at a heating rate of 20-40°C / min, and then held at 800°C for 2-3 hours. The second agglomerated particle group is heated and calcined through the following steps: first, the temperature is increased from room temperature to 800°C at a heating rate of 10-20°C / min, and then held at 800°C for 20-30 minutes; then, under a pressure of 80-100 MPa, the temperature is increased from 800°C to 1200-1500°C at a heating rate of 20-40°C / min, and then held at 800°C for 2-3 hours.

5. The corrosion-resistant coating for ammonia decomposition according to claim 1, characterized in that: In step six, the zirconium oxide composite material and the niobium disilicide composite material have different particle sizes; in step seven, an additive is added to the mixed zirconium oxide composite material and niobium disilicide composite material, wherein the additive is ethylene glycol, propylene glycol or polyacrylic acid.

6. The corrosion-resistant coating for ammonia decomposition according to claim 1, characterized in that: In step nine, the composite agglomerated particles are sintered through the following steps: first, the temperature is increased from room temperature to 750°C at a heating rate of 20°C / min, and then held for 15 to 25 minutes; then, under a pressure of 80 to 100 MPa, the temperature is increased from 750°C to 1000 to 1500°C at a heating rate of 10°C / min, and then held for 2 to 3 hours.

7. An ammonia decomposition reactor comprising the corrosion-resistant coating for ammonia decomposition as described in any one of claims 1 to 6, comprising a first cover plate, a second cover plate, a spirally arranged ammonia decomposition pipe, and an annular cover plate, characterized in that: The first cover plate and the second cover plate are respectively fixed to the upper and lower surfaces of the ammonia decomposition pipeline. The area of ​​the first cover plate is greater than or equal to the area of ​​the upper surface of the ammonia decomposition pipeline, and the area of ​​the second cover plate is greater than or equal to the area of ​​the lower surface of the ammonia decomposition pipeline. The edges of the first cover plate and the second cover plate are fixedly connected to the annular cover plate. The first cover plate, the second cover plate and the annular cover plate together form a sealed space. One end of the ammonia decomposition pipe is the ammonia decomposition inlet. The ammonia decomposition pipe extends spirally from the ammonia decomposition inlet toward the center of the first cover plate or the center of the second cover plate. The other end of the ammonia decomposition pipe is the ammonia decomposition outlet. The ammonia decomposition outlet passes through the second cover plate. There are gaps between adjacent pipe walls of the spirally arranged ammonia decomposition pipe.

8. An ammonia decomposition reactor according to claim 7, characterized in that: The first cover plate and the second cover plate are symmetrically arranged. A heating gas inlet is vertically arranged at the center of the first cover plate. The heating gas inlet is connected to the gap between the gap between the heating gas inlet and the adjacent pipe wall of the ammonia decomposition pipeline. The heating gas inlet is used to introduce gas with a temperature of above 500°C into the ammonia decomposition reactor. A heating gas outlet is vertically arranged on the part of the first cover plate near the ammonia decomposition inlet. The heating gas outlet is connected to the gap between the gap between the heating gas outlet and the adjacent pipe wall of the ammonia decomposition pipeline. The ammonia decomposition pipeline is filled with an ammonia decomposition catalyst.

9. An ammonia decomposition reactor according to claim 8, characterized in that: The corrosion-resistant coating for ammonia decomposition is located on the inner wall surface of the ammonia decomposition pipeline, and the roughness of the inner wall of the ammonia decomposition pipeline ranges from 45 to 80 μm; the corrosion-resistant coating for ammonia decomposition located on the inner wall of the ammonia decomposition pipeline is a sheet or laminate structure, and the thickness of the corrosion-resistant coating for ammonia decomposition ranges from 0.2 to 0.3 mm.

10. An ammonia decomposition reactor according to claim 9, characterized in that: The outer wall of the ammonia decomposition pipeline is also coated with the corrosion-resistant coating for ammonia decomposition. The corrosion-resistant coating for ammonia decomposition on the outer wall of the ammonia decomposition pipeline has a sheet or stacked structure. The thickness of the corrosion-resistant coating for ammonia decomposition on the outer wall of the ammonia decomposition pipeline ranges from 0.2 to 0.3 mm. The corrosion-resistant coating for ammonia decomposition on the outer wall of the ammonia decomposition pipeline contains aluminum oxide.

Images