Water-cooled wall self-cleaning infrared energy-saving coating, preparation method and application

Abstract

The application provides a water-cooled wall self-cleaning infrared energy-saving coating, a preparation method and application, and belongs to the field of inorganic refractory materials. A bottom coating of the application takes silicon carbide as a heat conduction network main body, matches with cordierite and boron nitride to form a multi-stage buffer network, accurately matches the thermal expansion coefficient of a metal base, inhibits thermal cycle cracking, enhances corrosion resistance and anti-peeling ability through alumina and zirconia, guarantees adhesion through a water glass-polyacrylamide-sodium tripolyphosphate composite bonding system, loads a catalyst in the heat conduction network, is beneficial to catalysis in an optimal temperature zone, realizes self-cleaning, a surface coating takes high-proportion silicon carbide combined with zirconia and brown corundum to form a super-hard wear-resistant system, resists erosion, a second bonding agent ensures high-temperature stability, the whole passes through heat conduction network optimization, infrared radiation performance improvement and heat efficiency improvement, simultaneously relies on catalytic self-cleaning, wear-resistant and corrosion-resistant structure design, realizes the technical effects of reducing ash deposition, prolonging the service life of the coating and reducing maintenance costs.

Description

Technical Field

[0001] This invention belongs to the field of inorganic refractory materials, specifically relating to a self-cleaning infrared energy-saving coating for water-cooled walls, its preparation method, and its application. Background Technology

[0002] As a key heat transfer component of coal-fired boilers, the water-cooled wall system plays a crucial role in absorbing radiant heat from the furnace, protecting the furnace walls, and maintaining steam temperature. However, under long-term high-temperature and high-pressure operation, water-cooled wall tubes face multiple complex problems:

[0003] Coking and ash accumulation: Fuel ash melts and adheres to the pipe wall surface to form a dense coking layer (especially when the flue gas temperature is higher than the ash melting point). Since its thermal resistance coefficient can be 300 to 500 times that of metal pipes, it will significantly reduce the heat transfer efficiency, resulting in an increase in flue gas temperature and increased coal consumption.

[0004] High-temperature corrosion: SO3, HCl and molten ash produced by the combustion of high-sulfur and high-chlorine fuels corrode the pipe wall metal, causing pipe wall thinning or even pipe rupture accidents. The typical corrosion rate can reach 2~5mm / year.

[0005] Pipe wall overheating: The heat insulation effect of the coking layer can easily cause the local pipe wall temperature to exceed the design value by 50~150℃, which will increase the risk of material creep failure.

[0006] High carbon content in fly ash: Unburned carbon particles are captured by the coke layer, hindering the final combustion of the carbon particles, resulting in an increase in the carbon content of fly ash and a reduction in combustion efficiency.

[0007] Studies have shown that heat transfer loss caused by coking and ash accumulation on water-cooled walls accounts for 12-18% of the total heat loss of boilers, while the ash layer reduces the infrared emissivity of the tube wall from 0.85 to 0.35, significantly weakening the radiative heat transfer efficiency.

[0008] Existing technologies mainly employ three methods to improve coking and ash accumulation on water-cooled walls:

[0009] I. Physical Intervention

[0010] Mechanical ash removal mainly uses steam blowing, infrasound ash removal and steel ball decoking. Its removal rate is low, it is ineffective against sticky ash, it has high energy consumption, and it will also accelerate pipe wall wear.

[0011] Thermodynamic control, by lowering the furnace temperature below the ash melting point to prevent coking and ash accumulation, will reduce combustion efficiency and significantly increase NOx generation.

[0012] II. Fuel Pretreatment

[0013] Additive modification: adding kaolin can increase the ash melting point, but it will increase the amount of ash and slag and aggravate pipe wall wear; adding limestone can absorb SO3 and thus reduce the generation of sticky sulfate, but it will lead to low-temperature scaling; adding magnesium oxide can form high-melting-point magnesium olivine with silicates, but it will lead to a significant increase in cost.

[0014] Strictly controlling the fineness of pulverized coal (R90 < 6%) can promote the complete combustion of ash, but its processing cost accounts for 18-25% of the total fuel cost.

[0015] III. Water-cooled wall coating modification

[0016] Existing technologies primarily employ metal diffusion coating, thermal spray ceramics, and enamel coating techniques. Metal diffusion coatings improve surface hardness and prevent dust accumulation through a Cr-Al diffusion layer; however, when the temperature reaches 1100℃, the volatilization of Cr2O3 leads to functional failure. Thermal spray ceramics prevent dust accumulation by forming a dense Al2O3-TiO2 barrier, but the large difference in thermal expansion coefficients between the materials easily leads to cracking. Enamel coatings isolate ash through a vitreous layer, but they are extremely prone to peeling.

[0017] Existing technologies also utilize low surface energy coatings (such as modified polytetrafluoroethylene) to reduce ash adhesion.

[0018] However, it is not temperature resistant and fails in the high-temperature zone of the furnace. There are also photocatalytic coating technology and conductive coating technology, but they are difficult to implement due to the difficulty in deploying ultraviolet light and high-voltage electrodes inside the furnace. Summary of the Invention

[0019] To address the aforementioned technical problems in the prior art, this invention aims to provide a self-cleaning infrared energy-saving coating for water-cooled walls, its preparation method, and its application.

[0020] One of the objectives of this invention is to provide a self-cleaning infrared energy-saving coating for water-cooled walls, the coating comprising a base coating and a surface coating;

[0021] The base coat comprises the following raw materials in parts by weight:

[0022] Thermally conductive aggregate, comprising 18-22 parts silicon carbide, 4-6 parts cordierite, 4-6 parts boron nitride, 5-7 parts alumina and 5-7 parts zirconium oxide;

[0023] 4-6 parts of catalyst, including copper oxide and / or iron oxide;

[0024] The first binder comprises 20-30 parts water glass, 0.1-1 parts polyacrylamide, and 0.1-1 parts sodium tripolyphosphate;

[0025] The first surfactant is 0.1 to 0.5 parts;

[0026] First defoamer, 0.1~0.3 parts;

[0027] The first adjuvant consists of 0.5-2 parts bentonite, 0.05-0.2 parts hydroxymethyl cellulose, and 2-4 parts Texanol ester alcohol;

[0028] 5-30 parts water;

[0029] The surface coating comprises the following raw materials in parts by weight:

[0030] Wear-resistant aggregate, comprising 25-35 parts silicon carbide, 5-7 parts zirconium oxide and 4-6 parts brown corundum;

[0031] The second adhesive includes 25-35 parts of SJ-8050 high-temperature adhesive;

[0032] The second surfactant is 0.1 to 0.5 parts;

[0033] Second defoamer, 0.1~0.3 parts;

[0034] The second adjuvant includes 0.5-2 parts bentonite, 0.05-0.2 parts hydroxymethyl cellulose, and 2-4 parts Texanol ester alcohol;

[0035] 5-30 parts water.

[0036] Preferably, the silicon carbide particle size D50 in the bottom coating is 7~9μm, the catalyst particle size is 150~250nm, and the silicon carbide particle size D50 in the top coating is 5~7μm.

[0037] Preferably, the mass ratio of catalyst to silicon carbide in the undercoat is 1:3.5~4.5.

[0038] Preferably, the mass ratio of cordierite to boron nitride in the base coat is 1:(0.9~1.1).

[0039] A second objective of this invention is to provide a method for preparing the infrared energy-saving coating as described above, wherein the method for preparing the underlying coating includes:

[0040] First, a water glass precursor was prepared using water glass, sodium tripolyphosphate, and polyacrylamide; a 5% bentonite solution was prepared using bentonite and water; and a 2% hydroxymethyl cellulose solution was prepared using hydroxymethyl cellulose and water.

[0041] Then, add water glass precursor, bentonite liquid, hydroxymethyl cellulose liquid, first surfactant and first defoamer in sequence, and stir at 300~600 rpm for 30 minutes. Then add thermally conductive aggregate, stir at low speed of 40~60 rpm for 30 minutes, then stir at high speed of 1000 rpm for 2 hours. Then add the remaining water and stir at 300~600 rpm for 45 minutes.

[0042] The method for preparing the surface coating includes:

[0043] First, prepare the bentonite solution and hydroxymethyl cellulose solution using the same method as the base coat;

[0044] Then, add component A of SJ-8050 high-temperature binder and add component B while stirring at 300-500 rpm. Continue stirring for 3 hours. Then, add bentonite liquid, hydroxymethyl cellulose liquid, second surfactant, and second defoamer in sequence. After stirring evenly, add wear-resistant aggregate. First, stir at a low speed of 40-60 rpm for 30 minutes, then stir at a high speed of 1000 rpm for 1 hour. Add the remaining water and stir at 300-600 rpm for 45 minutes.

[0045] The third objective of this invention is to provide an application of the infrared energy-saving coating described above in a water-cooled wall coating, wherein the water-cooled wall coating includes a bottom layer and a top layer, the bottom layer being located between the water-cooled wall and the top layer, the thickness of the bottom layer being 50~150μm, and the thickness of the top layer being 40~100μm.

[0046] Preferably, the method for treating the water-cooled wall coating includes:

[0047] First, the roughness of the water-cooled wall was treated by sandblasting to Rz=40~80μm, and the viscosity of the base coating and the top coating was adjusted to 1.35~1.45Pa·s;

[0048] Then, a base coat is sprayed onto the water-cooled wall and dried at 20~30℃ for 24 hours. The thickness of the base coat after drying is 20~150μm.

[0049] Then, a topcoat is sprayed onto the base layer and dried at 20-30°C for 24 hours. The thickness of the surface layer after drying is 40-100 μm.

[0050] Preferably, the coating treatment method further includes a curing step after the surface coating has dried;

[0051] The curing process includes: first, heating to 80°C at a rate of 2°C / min and holding for 60 min; then heating to 150°C at a rate of 1.5°C / min and holding for 30 min; then heating to 250°C at a rate of 3°C / min and holding for 45 min; and then cooling to 80°C at a rate of 1°C / min, followed by natural cooling.

[0052] Preferably, the coefficient of thermal expansion (CTE) of the bottom layer is (9.2~9.8) × 10⁻⁶. -6 / K.

[0053] Preferably, the wetting angle of the surface layer is >90°.

[0054] The beneficial effects of this invention include:

[0055] The water-cooled wall self-cleaning infrared energy-saving coating of this invention achieves multiple functions through the synergistic design of the bottom and surface layers: the bottom layer coating uses silicon carbide as the main heat-conducting network, combined with cordierite and boron nitride to form a multi-level buffer network, precisely matching the thermal expansion coefficient of the metal substrate to inhibit thermal cycling cracking; alumina and zirconium oxide enhance corrosion resistance and anti-stripping ability; the water glass-polyacrylamide-sodium tripolyphosphate composite bonding system ensures adhesion; and the catalyst is loaded in the heat-conducting network, which is conducive to its catalysis in the optimal temperature range to achieve self-cleaning; the surface coating uses a high proportion of silicon carbide combined with zirconium oxide and brown corundum to form an ultra-hard wear-resistant system to resist erosion; and SJ-8050 high-temperature binder ensures high-temperature stability. Overall, the thermal efficiency is improved through the optimization of the heat-conducting network and infrared radiation performance. At the same time, with its catalytic self-cleaning and wear-resistant and corrosion-resistant structural design, it achieves the technical effects of reducing dust accumulation, extending coating life, and reducing maintenance costs. Furthermore, the surface coating and the base coating have good wettability, and the surface coating can penetrate into the micropores of the base coating, which is beneficial for secondary sealing of the micropores of the base coating, thereby isolating the furnace gas from contact with the water-cooled wall and preventing chemical corrosion of the water-cooled wall by the chemical gases in the furnace gas. Detailed Implementation

[0056] The following description includes certain specific details to provide a comprehensive understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments can be implemented without employing one or more of these specific details, but using other methods, components, materials, etc.

[0057] Unless otherwise required by the present invention, throughout the specification and the following claims, the words “comprising” and “including” shall be interpreted in an open-ended, inclusive sense, meaning “including but not limited to”.

[0058] Throughout this specification, the terms "an embodiment," "an embodiment," "a preferred embodiment," or "some embodiments" refer to including, in at least one embodiment, a specific reference element, structure, or feature associated with that embodiment. Therefore, the phrases "in an embodiment," "in a preferred embodiment," or "in some embodiments" appearing in different places throughout the specification do not necessarily all refer to the same embodiment. Furthermore, specific elements, structures, or features may be combined in one or more embodiments in any suitable manner.

[0059] According to a first aspect of the present invention, a self-cleaning infrared energy-saving coating for water-cooled walls is provided, the coating comprising an undercoat and a topcoat;

[0060] The base coat comprises the following raw materials in parts by weight:

[0061] Thermally conductive aggregate, comprising 18-22 parts silicon carbide, 4-6 parts cordierite, 4-6 parts boron nitride, 5-7 parts alumina and 5-7 parts zirconium oxide;

[0062] 4-6 parts of catalyst, including copper oxide and / or iron oxide;

[0063] The first binder comprises 20-30 parts water glass, 0.1-1 parts polyacrylamide, and 0.1-1 parts sodium tripolyphosphate;

[0064] The first surfactant is 0.1 to 0.5 parts;

[0065] First defoamer, 0.1~0.3 parts;

[0066] The first adjuvant consists of 0.5-2 parts bentonite, 0.05-0.2 parts hydroxymethyl cellulose, and 2-4 parts Texanol ester alcohol;

[0067] 5-30 parts water;

[0068] In this invention, the undercoat is used to form the undercoat of the water-cooled wall coating.

[0069] In the components of the base coating, the thermally conductive aggregate includes 18-22 parts of silicon carbide, 4-6 parts of cordierite, 4-6 parts of boron nitride, 5-7 parts of alumina, and 5-7 parts of zirconium oxide.

[0070] Silicon carbide is used to form the main body of the heat-conducting network, and the amount of silicon carbide used is, for example, 18 parts, 18.5 parts, 19 parts, 19.5 parts, 20 parts, 20.5 parts, 21 parts, 21.5 parts or 22 parts.

[0071] Cordierite has a low coefficient of thermal expansion and good thermal shock resistance, which helps to match the expansion and contraction of the metal substrate and reduce the risk of stress cracking in the coating caused by thermal cycling. The dosage of cordierite is, for example, 4 parts, 4.2 parts, 4.4 parts, 4.6 parts, 4.8 parts, 5 parts, 5.2 parts, 5.4 parts, 5.6 parts, 5.8 parts, or 6 parts.

[0072] Cordierite exhibits anisotropic thermal expansion along the a, b, and c axes. In composite materials, the random distribution of grains in different directions can create an internal micro-strain cancellation effect.

[0073] Boron nitride possesses high in-plane thermal conductivity, which can eliminate hot spots through rapid heat conduction, reducing localized thermal stress. The lamellar structure of boron nitride can also absorb strain energy through slip, dissipating stress, preventing crack propagation, and improving coating toughness. Simultaneously, boron nitride is a low-modulus material, which can absorb impact energy under stress, reducing the risk of brittle fracture. The dosage of boron nitride is, for example, 4 parts, 4.2 parts, 4.4 parts, 4.6 parts, 4.8 parts, 5 parts, 5.2 parts, 5.4 parts, 5.6 parts, 5.8 parts, or 6 parts.

[0074] Cordierite and boron nitride work together to precisely control the coefficient of thermal expansion of the coating substrate, enabling the coating to form a gradient match with the steel substrate and suppressing thermal cycling cracking.

[0075] Cordierite disperses stress through lattice anisotropy and microcracks, while boron nitride dissipates stress through interlayer slip; together, they form a multi-level buffer network. The lamellar structure of boron nitride deflects crack paths, while the microcracks in cordierite prevent the extension of the main crack; together, they resist crack propagation. In conjunction with other components, they make the coating more compatible with the metal substrate and maintain the stability of the coating structure.

[0076] Alumina possesses high hardness, high melting point, wear resistance, and chemical inertness, providing structural strength, high-temperature resistance, corrosion resistance, and protection of the underlying substrate. The amount of alumina used is, for example, 5 parts, 5.2 parts, 5.4 parts, 5.6 parts, 5.8 parts, 6 parts, 6.2 parts, 6.4 parts, 6.6 parts, 6.8 parts, or 7 parts.

[0077] Zirconia possesses high toughness and a high melting point, primarily used to improve the impact and spalling resistance of coatings and compensate for the brittleness of high-hardness materials. Furthermore, its low thermal conductivity creates a certain thermal resistance gradient within the underlying layer, facilitating more uniform heat diffusion to the surface and preventing localized overheating. The dosage of zirconium oxide is, for example, 5 parts, 5.2 parts, 5.4 parts, 5.6 parts, 5.8 parts, 6 parts, 6.2 parts, 6.4 parts, 6.6 parts, 6.8 parts, or 7 parts.

[0078] In the base coat, silicon carbide forms the main body of a highly efficient heat transfer network, while cordierite and boron nitride synergistically form a multi-level buffer network. Together with other components, these components enhance the coating's compatibility with the metal substrate and maintain its structural stability. Alumina and zirconium oxide synergistically improve the coating's corrosion resistance.

[0079] In this invention, the first binder comprises 20-30 parts of water glass, 0.1-1 parts of polyacrylamide, and 0.1-1 parts of sodium tripolyphosphate.

[0080] Water glass, with a modulus of 2.5 to 3.5, can dehydrate and solidify at high temperatures to form a silica-oxygen network, providing high-strength inorganic adhesion, high-temperature resistance, and non-flammability. It is crucial for the bonding between the coating and the metal substrate and aggregate.

[0081] Polyacrylamide is used to improve the rheological properties of coatings during application. It has thickening and anti-sagging functions, enhances the wet adhesion of coatings, and improves the flexibility and crack resistance of coatings in the early stages of drying and curing.

[0082] Sodium tripolyphosphate helps disperse aggregate particles, prevents agglomeration and sedimentation, and improves the uniformity and stability of coatings.

[0083] Water glass, polyacrylamide, and sodium tripolyphosphate form an organic-inorganic composite bonding system. Water glass provides the final high-temperature strength and inorganic bonding, polyacrylamide improves workability and initial performance, and sodium tripolyphosphate ensures system stability. Together, these three components guarantee the integrity and adhesion of the coating during application, curing, and operation.

[0084] The catalyst is used in amounts of, for example, 4 parts, 4.2 parts, 4.4 parts, 4.6 parts, 4.8 parts, 5 parts, 5.2 parts, 5.4 parts, 5.6 parts, 5.8 parts, or 6 parts, and includes copper oxide and / or iron oxide. Under the high-temperature environment of boiler operation, copper oxide and iron oxide can catalyze the oxidation reaction of carbon deposits produced by incomplete combustion of fuel and organic pollutants adhering to the coating surface. The catalyst is, for example, copper oxide, iron oxide, or a combination of copper oxide and iron oxide, preferably copper oxide.

[0085] In this invention, the catalyst is placed at the bottom layer of the water-cooled wall coating. Since the temperature of the bottom layer is lower than that of the surface layer, it can ensure that the catalytic reaction of the catalyst is in the optimal temperature range, such as the optimal temperature range of CuO, which is 500~800℃. On the other hand, it can avoid high-temperature sintering of the surface layer, because when the temperature exceeds 1000℃, the catalyst grains grow, which will greatly reduce the catalyst activity.

[0086] In this invention, the catalyst at the bottom layer activates oxygen, converting lattice oxygen into reactive oxygen free radicals. These reactive oxygens then diffuse to the coating surface to oxidize the surface fly ash. Because the catalyst is supported in a silicon carbide thermally conductive network, high-temperature heat can be rapidly transferred to the catalytic sites. Furthermore, silicon carbide, acting as a "conductive bridge," can accelerate electron transfer, promote the formation of reactive oxygen free radicals, and thus facilitate the efficient catalytic reaction.

[0087] The first surfactant reduces the surface tension of the coating, improves its wettability to metal substrates and aggregate particles, makes the coating easier to spread and penetrate into the micropores of the substrate, enhances adhesion, and also helps with dispersion stability. The amount of the first surfactant used is, for example, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, or 0.5 parts.

[0088] Specifically, the first surfactant is a nonionic surfactant, including JFC surfactants.

[0089] The first defoamer is used to eliminate or inhibit the generation of bubbles during the preparation and application of the coating, thereby preventing a reduction in the density, strength, adhesion, and protective performance of the coating due to pinholes, defects, etc. The dosage of the first defoamer is, for example, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, or 0.3 parts.

[0090] Specifically, the first defoamer includes an organosilicone surfactant.

[0091] The first adjuvant comprises 0.5 to 2 parts of bentonite, 0.05 to 0.2 parts of hydroxymethyl cellulose, and 2 to 4 parts of Texanol ester alcohol.

[0092] Bentonite imparts thixotropic properties to coatings, preventing aggregate settling during storage and application, and improving workability. The amount of bentonite used is, for example, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, or 2 parts.

[0093] Hydroxymethyl cellulose is used to increase viscosity, improve leveling properties, slow down the rate of moisture evaporation, prolong open time, and reduce drying cracks. The amount of hydroxymethyl cellulose used is, for example, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, 0.11 parts, 0.12 parts, 0.13 parts, 0.14 parts, 0.15 parts, 0.16 parts, 0.17 parts, 0.18 parts, 0.19 parts, or 0.2 parts.

[0094] Texanol ester alcohol is used to promote better film formation in coatings and improve the continuity and density of the paint film. The amount of Texanol ester alcohol used is, for example, 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts, or 4 parts.

[0095] These three elements work together to optimize the rheological properties, storage stability, application performance, and film quality of the coating.

[0096] The surface coating comprises the following raw materials in parts by weight:

[0097] Wear-resistant aggregate, comprising 25-35 parts silicon carbide, 5-7 parts zirconium oxide and 4-6 parts brown corundum;

[0098] The second adhesive includes 25-35 parts of SJ-8050 high-temperature adhesive;

[0099] The second surfactant is 0.1 to 0.5 parts;

[0100] Second defoamer, 0.1~0.3 parts;

[0101] The second adjuvant includes 0.5-2 parts bentonite, 0.05-0.2 parts hydroxymethyl cellulose, and 2-4 parts Texanol ester alcohol;

[0102] 5-30 parts water.

[0103] In this invention, the surface coating is used to form the surface layer of the water-cooled wall coating.

[0104] In the components of the surface coating, the wear-resistant aggregate includes 25-35 parts of silicon carbide, 5-7 parts of zirconium oxide, and 4-6 parts of brown corundum.

[0105] Silicon carbide is used to form the main body of the heat-conducting network, and the amount of silicon carbide used is, for example, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, or 35 parts. In the surface coating, the proportion of silicon carbide is relatively large, which is beneficial to improving the basic wear resistance of the surface layer.

[0106] Zirconia is used in surface coatings to improve the surface's resistance to mechanical shock and thermal shock, preventing cracking and spalling. Its low thermal conductivity also helps maintain surface temperature, which is beneficial for infrared radiation. The amount of zirconium oxide used is, for example, 5 parts, 5.2 parts, 5.4 parts, 5.6 parts, 5.8 parts, 6 parts, 6.2 parts, 6.4 parts, 6.6 parts, 6.8 parts, or 7 parts.

[0107] Brown fused alumina is the core wear-resistant component, which can directly withstand the scouring and abrasion of high-speed ash particles and coal dust in the furnace, protecting the bottom layer and substrate. It also has high temperature resistance and chemical stability. The dosage of brown fused alumina is, for example, 4 parts, 4.2 parts, 4.4 parts, 4.6 parts, 4.8 parts, 5 parts, 5.2 parts, 5.4 parts, 5.6 parts, 5.8 parts, or 6 parts.

[0108] In this invention, brown fused alumina, zirconium oxide, and silicon carbide work synergistically to form an ultra-hard composite wear-resistant system. Brown fused alumina resists wear, zirconium oxide absorbs impact energy to prevent brittle fracture, and silicon carbide maintains the heat conduction path. Overall, this ensures the surface layer remains effective for a long time under harsh erosion conditions.

[0109] The second adhesive is SJ-8050 high-temperature adhesive, and the amount of the second adhesive is, for example, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts or 35 parts.

[0110] Specifically, the second adhesive is Sanjin Company's SJ-8050 high-temperature adhesive, which includes component A and component B. It has high-strength adhesion, is particularly suitable for the wear-resistant aggregate system described in this invention, and has excellent high-temperature stability, which can remain stable for a long time at high boiler temperatures.

[0111] The second surfactant reduces the surface tension of the coating, improves its wettability to metal substrates and aggregate particles, makes the coating easier to spread, penetrates into the micropores of the substrate, and improves adhesion, while also contributing to dispersion stability. The amount of the second surfactant used is, for example, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, or 0.5 parts.

[0112] Specifically, the second surfactant is a nonionic surfactant, including JFC surfactants.

[0113] The second defoamer is used to eliminate or inhibit the generation of bubbles during the preparation and application of the coating, thereby preventing a reduction in the density, strength, adhesion, and protective performance of the coating due to pinholes, defects, etc. The dosage of the second defoamer is, for example, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, or 0.3 parts.

[0114] Specifically, the second defoamer includes an organosilicone defoamer.

[0115] The second auxiliary agent includes 0.5 to 2 parts of bentonite, 0.05 to 0.2 parts of hydroxymethyl cellulose, and 2 to 4 parts of Texanol ester alcohol.

[0116] Bentonite imparts thixotropic properties to coatings, preventing sedimentation during storage and application and improving workability. The amount of bentonite used is, for example, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, or 2 parts.

[0117] Hydroxymethyl cellulose is used to increase viscosity, improve leveling properties, slow down the rate of moisture evaporation, prolong open time, and reduce drying cracks. The amount of hydroxymethyl cellulose used is, for example, 0.05 parts, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, 0.11 parts, 0.12 parts, 0.13 parts, 0.14 parts, 0.15 parts, 0.16 parts, 0.17 parts, 0.18 parts, 0.19 parts, or 0.2 parts.

[0118] Texanol ester alcohol is used to promote better film formation in coatings and improve the continuity and density of the paint film. The amount of Texanol ester alcohol used is, for example, 2 parts, 2.2 parts, 2.4 parts, 2.6 parts, 2.8 parts, 3 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts, or 4 parts.

[0119] These three elements work together to optimize the rheological properties, storage stability, application performance, and film quality of the coating.

[0120] In a preferred embodiment of the present invention, the silicon carbide particle size D50 in the undercoat is 7~9μm, and the catalyst particle size is 150~250nm.

[0121] In this invention, silicon carbide with a particle size of 7~9μm can increase the packing density and form a continuous interpenetrating thermal conductive network in the bottom layer, thereby reducing interfacial thermal resistance and optimizing the thermal conductive network.

[0122] The catalyst particle size is controlled within the range of 150-250 nm, which provides sufficient active sites and also avoids high-temperature migration and aggregation of nanoparticles while ensuring low-temperature reaction activity.

[0123] The synergistic effect of silicon carbide and catalyst particle size can form a "pebble-sand" filling model, with silicon carbide forming the framework and the catalyst filling the gaps, which is beneficial to improving catalytic efficiency.

[0124] In a preferred embodiment of the present invention, the silicon carbide particle size D50 in the surface coating is 5~7μm.

[0125] In this invention, firstly, 5-7 μm silicon carbide and brown fused alumina form a dual-scale wear-resistant system, with the brown fused alumina having a particle size of 10-20 μm. The fine silicon carbide particles fill the gaps between the brown fused alumina particles, which can reduce stress concentration points. Secondly, 5-7 μm silicon carbide is beneficial for forming a smooth surface and reducing ash adhesion points. Thirdly, fine particles are more likely to form a continuous infrared radiation surface in high-temperature binders, thereby improving infrared emissivity.

[0126] In a preferred embodiment of the present invention, the mass ratio of catalyst to silicon carbide in the undercoat is 1:3.5~4.5.

[0127] In this invention, when the mass ratio of catalyst to silicon carbide is 1:3.5~4.5, the catalyst is uniformly dispersed on the surface of the silicon carbide particles, forming a core-shell-like composite structure, which optimizes the active sites. Simultaneously, due to rapid heat transfer, the catalytic reaction rate is significantly increased; and the heat of reaction can be quickly dissipated, further preventing catalyst sintering. When the mass ratio of catalyst to silicon carbide is 1:3.5~4.5, the volume fraction of silicon carbide reaches 65~70%, forming a continuous rigid framework, which is beneficial for improving the mechanical strength of the coating. When the mass ratio of catalyst to silicon carbide is less than 1:3.5, thermal channels are easily blocked, potentially leading to accelerated sintering and increased costs. When the mass ratio of catalyst to silicon carbide is greater than 1:4.5, there are insufficient catalytic active sites, which may result in a decrease in self-cleaning effect.

[0128] In this invention, the mass ratio of catalyst to silicon carbide is, for example, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9, 1:4, 1:4.1, 1:4.2, 1:4.3, 1:4.4 or 1:4.5.

[0129] In a preferred embodiment of the present invention, the mass ratio of cordierite to boron nitride in the undercoat is 1:(0.9~1.1).

[0130] In this invention, when the mass ratio of cordierite to boron nitride is 1:0.9 to 1.1, cordierite forms a rigid framework as equiaxed particles, while boron nitride fills the gaps as a lamellar structure, forming an interpenetrating thermally conductive and toughening network. This also facilitates precise control of the coating's coefficient of thermal expansion to match the steel substrate. Examples of cordierite to boron nitride mass ratios include 1:0.9, 1:0.92, 1:0.94, 1:0.96, 1:0.98, 1:1, 1:1.02, 1:1.04, 1:1.06, 1:1.08, or 1:1.1.

[0131] According to a second aspect of the present invention, a method for preparing the infrared energy-saving coating as described above is provided, characterized in that the method for preparing the underlying coating includes:

[0132] First, a water glass precursor was prepared using water glass, sodium tripolyphosphate, and polyacrylamide; a 5% bentonite solution was prepared using bentonite and water; and a 2% hydroxymethyl cellulose solution was prepared using hydroxymethyl cellulose and water.

[0133] Then, add water glass precursor, bentonite liquid, hydroxymethyl cellulose liquid, first surfactant and first defoamer in sequence, and stir at 300~600 rpm for 30 minutes. Then add thermally conductive aggregate, stir at low speed of 40~60 rpm for 30 minutes, then stir at high speed of 1000 rpm for 2 hours. Then add the remaining water and stir at 300~600 rpm for 45 minutes.

[0134] The method for preparing the surface coating includes:

[0135] First, prepare the bentonite solution and hydroxymethyl cellulose solution using the same method as the base coat;

[0136] Then, add component A of SJ-8050 high-temperature binder and add component B while stirring at 300-500 rpm. Continue stirring for 3 hours. Then, add bentonite liquid, hydroxymethyl cellulose liquid, second surfactant, and second defoamer in sequence. After stirring evenly, add wear-resistant aggregate. First, stir at a low speed of 40-60 rpm for 30 minutes, then stir at a high speed of 1000 rpm for 1 hour. Add the remaining water and stir at 300-600 rpm for 45 minutes.

[0137] Specifically, when preparing the topcoat and the basecoat, the method for preparing the bentonite solution includes: adding 95 parts of water to a mixer, adding 5 parts of sodium-based bentonite while stirring at 200-400 rpm, continuing to stir at low speed for 30 minutes, then stirring at high speed for 60 minutes at 800-1200 rpm, and letting it stand for 24 hours before use.

[0138] The method for preparing hydroxymethyl cellulose solution includes: adding 98 parts of water to a stirrer, adding 2 parts of hydroxymethyl cellulose while stirring at a low speed of 200-400 rpm, continuing to stir at a low speed for 30 minutes, then stirring at a high speed of 800-1200 rpm for 60 minutes, and letting it stand for 24 hours before use.

[0139] The preparation method of water glass precursor includes: first, adding water glass into a reaction vessel and heating it to 40~80℃, then adding 0.2 parts of sodium tripolyphosphate while stirring at 300~500 rpm, stirring until dissolved, then adding polyacrylamide and stirring for 45 minutes.

[0140] According to a third aspect of the present invention, an application of the infrared energy-saving coating as described above in a water-cooled wall coating is provided, the water-cooled wall coating comprising a base layer and a surface layer, the base layer being located between the water-cooled wall and the surface layer, the base layer having a thickness of 50~150μm, and the surface layer having a thickness of 40~100μm.

[0141] In this invention, when the thickness of the bottom layer is less than 50 μm, it may be difficult for silicon carbide particles to form a continuous thermally conductive chain, causing the thermally conductive network to break. This can lead to heat accumulation at the metal interface, resulting in local overheating. It may also result in insufficient coverage of the nano-catalyst layer, expanding the blind zone of the carbon oxidation reaction, and potentially causing molten slag to penetrate the coating and accelerating corrosion. When the thickness of the bottom layer is greater than 150 μm, it may lead to increased thermal resistance, increased heat loss rate, delayed thermal response, and edge cracking due to thermal stress concentration.

[0142] When the surface layer thickness is less than 40μm, the brown fused alumina may be difficult to form an effective stacked layer, leading to failure of wear protection, resulting in the risk of exposure of the substrate and accelerated erosion. It may also cause cracking due to infrared radiation attenuation and thermal stress concentration.

[0143] When the surface layer thickness is greater than 100 μm, the effective infrared emissivity and thermal absorption efficiency may be reduced due to the infrared radiation shielding effect, which may also increase the risk of thermal stress cracking and increase the probability of edge peeling.

[0144] Preferably, the total thickness of the top and bottom layers is 130-180 μm, wherein the bottom layer thickness is 80-100 μm and the top layer thickness is 50-80 μm. At this thickness, thermal conductivity, mechanical properties, and self-cleaning ability are all good. The bottom layer thickness is preferably 90 μm, and the top layer thickness is preferably 60 μm.

[0145] In a preferred embodiment of the present invention, the method for treating the water-cooled wall coating includes:

[0146] First, the roughness of the water-cooled wall was treated by sandblasting to Rz=40~80μm, and the viscosity of the base coating and the top coating was adjusted to 1.35~1.45Pa·s;

[0147] Then, a base coat is sprayed onto the water-cooled wall and dried at 20~30℃ for 24 hours. The thickness of the base coat after drying is 20~150μm.

[0148] Then, a topcoat is sprayed onto the base layer and dried at 20-30°C for 24 hours. The thickness of the surface layer after drying is 40-100 μm.

[0149] In this invention, the roughness of the water-cooled wall is first treated to Rz=40~80μm through sandblasting, which effectively increases the contact area between the coating and the water-cooled wall and improves adhesion. The viscosity of the base coat and the top coat is precisely controlled at 1.35~1.45Pa·s to ensure uniform coating and avoid defects such as sagging and dripping. The base coat and the top coat are sprayed in layers and dried at a suitable temperature, resulting in a dense and layered coating structure. The thickness of the base coat is controlled at 50~150μm and the thickness of the top coat is controlled at 40~100μm. This fully utilizes the thermal conductivity and catalytic properties of the base coat and the wear resistance of the top coat, significantly improving the overall performance of the water-cooled wall coating, extending the service life of the water-cooled wall, and reducing operation and maintenance costs.

[0150] Because of the good wettability between the topcoat and the basecoat, when the topcoat is sprayed on the basecoat, the topcoat can penetrate into the micropores of the basecoat, which helps to seal the micropores of the basecoat a second time, thereby isolating the furnace gas from contact with the water-cooled wall and preventing the chemical gases in the furnace gas from causing chemical corrosion to the water-cooled wall.

[0151] In this invention, the bottom layer is first dried for 24 hours, and the water glass is fully dehydrated to form a ≡Si-O-Si≡ network. This also avoids the swelling of the bottom layer caused by the subsequent penetration of the surface solvent.

[0152] After drying the surface for 24 hours, a high-strength and hard ceramic-like layer is formed on the surface of the water-cooled wall tubes through high-temperature sintering in the boiler. The heating rate of natural sintering in the boiler is generally 5℃~10℃ / min, the furnace temperature is usually between 1300℃~1600℃, the flue gas temperature is about 800℃~1200℃, and the surface temperature of the water-cooled wall is about 300℃~500℃.

[0153] After high-temperature sintering in the boiler, the alumina, zirconium oxide, and other raw materials in the bottom coating undergo a solid-phase reaction at high temperatures, crystallizing together with thermally conductive aggregates such as silicon carbide to form a stable ceramic phase framework. The brown corundum and zirconium oxide in the surface coating further densify at high temperatures, interpenetrating with the cross-linking products of the SJ-8050 high-temperature binder to form a composite structure with ceramic properties. The synergistic effect of these two materials constructs a continuous, uniform, and dense ceramic-like layer on the surface of the water-cooled wall tubes.

[0154] In a preferred embodiment of the present invention, the coating treatment method further includes a step of curing the surface coating after it has dried;

[0155] The curing process includes: first, heating to 80°C at a rate of 2°C / min and holding for 60 min; then heating to 150°C at a rate of 1.5°C / min and holding for 30 min; then heating to 250°C at a rate of 3°C / min and holding for 45 min; and then cooling to 80°C at a rate of 1°C / min, followed by natural cooling.

[0156] In this invention, the temperature is raised to 80°C at a rate of 2°C / min and held for 60 minutes to allow residual solvent in the coating to fully evaporate and reduce internal porosity. Subsequently, the temperature is raised to 150°C at a rate of 1.5°C / min and held for 30 minutes, during which the SJ-8050 high-temperature binder undergoes deep cross-linking, enhancing the intermolecular forces. The temperature is then raised to 250°C at a rate of 3°C / min and held for 45 minutes to promote chemical bonding between various inorganic components in the coating, making the ceramic-like layer structure more stable. Finally, the temperature is lowered to 80°C at a rate of 1°C / min and allowed to cool naturally. This slow cooling process avoids coating cracking caused by thermal stress concentration, ensuring the integrity of the coating. Through this series of curing processes, the coating's hardness, wear resistance, and thermal shock resistance are significantly improved, further extending the service life of the water-cooled wall and helping to maintain good infrared radiation performance, continuously ensuring efficient heat exchange of the water-cooled wall and improving energy-saving effects.

[0157] In a preferred embodiment of the present invention, the coefficient of thermal expansion of the bottom layer, CTE, is (9.2~9.8) × 10⁻¹⁰. -6 / K.

[0158] In this invention, the coefficient of thermal expansion of the bottom layer is (9.2~9.8)×10⁻¹⁰.-6 At / K, it can effectively reduce the interfacial stress caused by the difference in thermal expansion between the coating and the water-cooled wall during high-temperature operation, thus preventing coating peeling. Meanwhile, the coefficient of thermal expansion of the bottom layer is slightly lower than that of the surface ceramic-like layer, which has a coefficient of thermal expansion of approximately (10~12)×10. -6 The / K gradient allows the coating to develop a compressive stress state during cooling, improving its resistance to crack propagation. This gradient thermal expansion design, combined with the dense structure formed by the curing process, significantly enhances the coating's thermal shock resistance, enabling it to withstand drastic temperature changes during boiler start-up and shutdown without cracking or peeling, thus greatly extending the coating's service life.

[0159] In a preferred embodiment of the present invention, the wetting angle of the surface layer is >90°.

[0160] In this invention, the surface layer is hydrophobic. This hydrophobic surface effectively reduces the contact area between the coating and molten ash, corrosive gases, and the coating in high-temperature flue gas, thus reducing the slagging rate and fouling degree. When fly ash particles impact the coating surface, the repulsive force generated by the high wetting angle makes it difficult for them to adhere or only forms a loose accumulation, which is easily detached under airflow scouring or mechanical vibration, achieving a self-cleaning function. At the same time, the hydrophobicity also prevents water vapor from condensing on the coating surface, reducing the risk of sulfuric acid dew point corrosion and stress corrosion cracking, further protecting the water-cooled wall substrate material. Through this hydrophobic design, combined with the high thermal conductivity of the underlying layer and the high wear resistance of the surface layer, the coating system of this invention comprehensively improves the anti-slagging, anti-corrosion, and self-cleaning capabilities of the water-cooled wall, significantly reducing maintenance costs and energy consumption during boiler operation.

[0161] Example

[0162] The present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0163] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0164] The preparation methods of the base coat and top coat in each embodiment and comparative example include:

[0165] I. Preparation of the base coat

[0166] First, add water glass to the reactor and heat it to 40~80℃. Add 0.2 parts of sodium tripolyphosphate while stirring at 300~500 rpm. After stirring and dissolving, add polyacrylamide and stir for 45 minutes.

[0167] Add 95 parts water to a mixer, add 5 parts sodium bentonite while stirring at 200-400 rpm, continue stirring at low speed for 30 minutes, then stir at high speed for 60 minutes at 800-1200 rpm, and let stand for 24 hours before use.

[0168] Add 98 parts water to a mixer, add 2 parts hydroxymethyl cellulose while mixing at a low speed of 200-400 rpm, continue mixing at a low speed for 30 minutes, then mix at a high speed of 800-1200 rpm for 60 minutes, and let stand for 24 hours before use.

[0169] Then, water glass precursor, bentonite liquid, hydroxymethyl cellulose liquid, first surfactant and first defoamer are added in sequence, and stirred at 300~600 rpm for 30 minutes. Then, thermally conductive aggregate is added, and stirred at a low speed of 40~60 rpm for 30 minutes, and then stirred at a high speed of 1000 rpm for 2 hours. Then, the remaining water is added, and stirred at 300~600 rpm for 45 minutes. The viscosity of the base coating is adjusted to 1.35~1.45 Pa·s.

[0170] II. Preparation of Surface Coating

[0171] First, add 95 parts water to a mixer, add 5 parts sodium bentonite while stirring at 200-400 rpm, continue stirring at low speed for 30 minutes, then stir at high speed for 60 minutes at 800-1200 rpm, and let stand for 24 hours before use.

[0172] Add 98 parts water to a mixer, add 2 parts hydroxymethyl cellulose while mixing at a low speed of 200-400 rpm, continue mixing at a low speed for 30 minutes, then mix at a high speed of 800-1200 rpm for 60 minutes, and let stand for 24 hours before use.

[0173] Then, add component A of SJ-8050 high-temperature binder and add component B while stirring at 300-500 rpm. Continue stirring for 3 hours. Then, add bentonite liquid, hydroxymethyl cellulose liquid, second surfactant, and second defoamer in sequence. After stirring evenly, add wear-resistant aggregate. First, stir at a low speed of 40-60 rpm for 30 minutes, then stir at a high speed of 1000 rpm for 1 hour. Add the remaining water and stir at 300-600 rpm for 45 minutes. Adjust the viscosity of the base coat to 1.35-1.45 Pa·s.

[0174] The raw material composition of each embodiment is as follows:

[0175] Example 1

[0176] The base coat comprises the following raw materials in parts by weight: 20 parts silicon carbide, 5 parts cordierite, 5 parts boron nitride, 6 parts alumina, 6 parts zirconium oxide, 5 parts copper oxide, 25 parts water glass, 0.2 parts polyacrylamide, 0.2 parts sodium tripolyphosphate, 0.2 parts JFC surfactant, 0.15 parts silicone defoamer, 1 part bentonite, 0.1 part hydroxymethyl cellulose, 3 parts Texanol ester alcohol, and 23.15 parts water.

[0177] In the base coating, the silicon carbide particle size D50 is 8 μm, and the copper oxide particle size is 200 nm. The mass ratio of catalyst to silicon carbide is 1:4, and the mass ratio of cordierite to boron nitride is 1:1.

[0178] The surface coating comprises the following raw materials in parts by weight: 30 parts silicon carbide, 6 parts zirconium oxide, 5 parts brown corundum, 30 parts SJ-8050 high-temperature binder, 0.2 parts JFC surfactant, 0.15 parts silicone defoamer, 1 part bentonite, 0.1 part hydroxymethyl cellulose, 3 parts Texanol ester alcohol, and 24.55 parts water.

[0179] In the surface coating, the particle size D50 of silicon carbide is 6 μm.

[0180] Then, coating / steel substrate composite samples were prepared:

[0181] First, after cleaning the steel substrate surface, the roughness of the steel substrate is treated by sandblasting to Rz=40~80μm. Then, a base coat with a viscosity of 1.35~1.45Pa·s is loaded into a spray can and sprayed. It is dried at 20~30℃ for 24h, and the thickness of the base coat after drying is 90μm. Then, a top coat with a viscosity of 1.35~1.45Pa·s is loaded into a spray can and sprayed on the base coat. It is dried at 20~30℃ for 24h, and the thickness of the top coat after drying is 60μm.

[0182] Then, the combustion inside the boiler was simulated for solidification treatment. The heating rate was controlled at about 70℃ / min, the surface temperature of the steel substrate was controlled at about 400℃, and sintering was carried out for 3.5 hours, followed by natural cooling.

[0183] Example 2

[0184] The difference from Example 1 is that the silicon carbide particle size D50 in the base coating is 6 μm.

[0185] The rest is the same as in Example 1.

[0186] Example 3

[0187] The difference from Example 1 is that the silicon carbide particle size D50 in the base coating is 10 μm.

[0188] The rest is the same as in Example 1.

[0189] Example 4

[0190] The difference from Example 1 is that the silicon carbide particle size D50 in the surface coating is 8 μm.

[0191] The rest is the same as in Example 1.

[0192] Example 5

[0193] The difference from Example 1 is that the base coating contains 6 parts of copper oxide, and the mass ratio of copper oxide to silicon carbide is 1:3.33.

[0194] The rest is the same as in Example 1.

[0195] Example 6

[0196] The difference from Example 1 is that the base coating contains 4.5 parts of copper oxide, and the mass ratio of copper oxide to silicon carbide is 1:4.44.

[0197] The rest is the same as in Example 1.

[0198] Example 7

[0199] Compared with Example 1, the difference is that the base coating contains 4 parts boron nitride and 6 parts cordierite, with the rest being the same as in Example 1.

[0200] Example 8

[0201] Compared with Example 1, the difference is that the base coating contains 6 parts boron nitride and 4 parts cordierite, with the rest being the same as in Example 1.

[0202] Example 9

[0203] Compared with Example 1, the difference is that the thickness of the bottom layer is 70 μm and the thickness of the top layer is 40 μm, while the rest is the same as Example 1.

[0204] Example 10

[0205] Compared with Example 1, the difference is that the thickness of the bottom layer is 130 μm and the thickness of the top layer is 90 μm, while the rest is the same as Example 1.

[0206] Example 11

[0207] Compared with Example 1, the difference is that the thickness of the bottom layer is 80 μm and the thickness of the top layer is 50 μm, while the rest is the same as Example 1.

[0208] Example 12

[0209] Compared with Example 1, the difference is that the thickness of the bottom layer is 100μm and the thickness of the top layer is 80μm, while the rest is the same as Example 1.

[0210] Example 13

[0211] Compared with Example 1, the difference lies in the curing process during the preparation of the coating / steel substrate composite sample: first, the temperature is raised to 80°C at a rate of 2°C / min and held for 60 min; then, the temperature is raised to 150°C at a rate of 1.5°C / min and held for 30 min; then, the temperature is raised to 250°C at a rate of 3°C / min and held for 45 min; then, the temperature is lowered to 80°C at a rate of 1°C / min and allowed to cool naturally.

[0212] Comparative Example 1

[0213] Compared with Example 1, the difference is that copper oxide is not used in the base coat, otherwise it is the same as Example 1.

[0214] Comparative Example 2

[0215] Compared with Example 1, the difference is that copper oxide is not used in the base coating, but 5 parts of copper oxide are added to the surface layer, otherwise the same as in Example 1.

[0216] Comparative Example 3

[0217] Compared with Example 1, the difference is that the thickness of the bottom layer is 40μm, and the rest is the same as Example 1.

[0218] Comparative Example 4

[0219] Compared with Example 1, the difference is that the surface layer thickness is 30 μm, otherwise it is the same as Example 1.

[0220] The following tests were conducted on Examples 1-13 and Comparative Examples 1-4:

[0221] 1. Coefficient of thermal expansion

[0222] Thermal expansion testers were used to conduct tests according to GB / T 7320-2018 "Coating Thermal Expansion Coefficient". The test samples were coated with the primer and dried for 24 hours, then cured directly according to the curing treatment methods of each embodiment and comparative example before measurement.

[0223] 2. Thermal conductivity

[0224] The cured coating was tested according to GB / T 22588-2008 "Measuring thermal diffusivity or thermal conductivity by flash method".

[0225] 3. Infrared emissivity

[0226] The cured coating was sampled and measured in accordance with GB / T 13488-2015 "Method for Testing Infrared Emissivity of Materials".

[0227] 4. Thermal shock performance test

[0228] The sample was heated to 500°C in a high-temperature muffle furnace, held at that temperature for 30 minutes, quenched in cold water, and then heated again. This process was repeated 45 times, and the peeling rate was observed.

[0229] 5. Adhesion

[0230] After thermal shock cycling, the peeling condition was tested according to GB / T 9286 using the cross-cut test with a spacing of 1 mm.

[0231] 6. Coating hardness test

[0232] Surface hardness was tested using a micro Vickers hardness tester with a load of 500g, in accordance with standard GB / T 4340.1.

[0233] 7. High temperature corrosion resistance

[0234] According to GB / T 25928-2010 "Test Method for High Temperature Corrosion Resistance of Metallic and Other Inorganic Coatings", a corrosion test was conducted using simulated flue gas (volume content: SO32%, HCl1%, O215%, H2O12%, with nitrogen as the balance gas) at a temperature of 500℃±5℃ for 200h. The corrosion rate was calculated by weighing.

[0235] 8. Catalytic activity

[0236] First, a carbon deposit mixture (volume content of CO 10%, CH 45%, O 23%, N 282%) was introduced and run at 700℃ for 20 h; then, the mixture was switched to a CO / O 2 mixture (CO 5%, O 22.5%, N 292.5%), and the temperature was maintained at 500℃, with CO conversion rate monitored by GC.

[0237] 9. Wetting angle

[0238] Use a contact angle meter to measure the wetting angle.

[0239] The test results are shown in Table 1.

[0240] Table 1 Test results of Examples 1-13 and Comparative Examples 1-4

[0241] .

[0242] The coating from Example 1 was applied to the water-cooled wall of a 600MW boiler in a power plant. After 12 months of continuous operation,

[0243] The coking rate was reduced by 68%, thermal efficiency was improved, flue gas temperature decreased by 18°C, coal consumption was reduced by 1.8g / kWh, maintenance costs were reduced, and the frequency of soot blowing was reduced from 2 times / day to 1 time / week.

[0244] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A water-cooled wall self-cleaning infrared energy-saving coating, characterized in that, The coating includes a base layer coating and a surface layer coating; The base layer coating includes the following weight parts of each raw material: Thermal conductive aggregate, including 18-22 parts of silicon carbide, 4-6 parts of cordierite, 4-6 parts of boron nitride, 5-7 parts of aluminum oxide, and 5-7 parts of zirconium oxide; Catalyst 4-6 parts, including copper oxide; First binder, including water glass 20-30 parts, polyacrylamide 0.1-1 part, and sodium tripolyphosphate 0.1-1 part; First surfactant 0.1-0.5 parts; First defoaming agent, 0.1-0.3 parts; First aid, including bentonite 0.5-2 parts, hydroxymethyl cellulose 0.05-0.2 parts, and Texanol ester alcohol 2-4 parts; Water 5-30 parts; The surface layer coating includes the following weight parts of each raw material: Wear-resistant aggregate, including 25-35 parts of silicon carbide, 5-7 parts of zirconium oxide, and 4-6 parts of brown corundum; Second binder, including sj-8050 high-temperature binder 25-35 parts; Second surfactant 0.1-0.5 parts; Second defoaming agent, 0.1-0.3 parts; Second aid, including bentonite 0.5-2 parts, hydroxymethyl cellulose 0.05-0.2 parts, and Texanol ester alcohol 2-4 parts; Water 5-30 parts.

2. The infrared energy saving coating as claimed in claim 1, wherein, The particle size D50 of silicon carbide in the base layer coating is 7-9 μm, and the particle size of the catalyst is 150-250 nm. The particle size D50 of silicon carbide in the surface layer coating is 5-7 μm.

3. The infrared energy saving coating as claimed in claim 1, wherein, The mass ratio of catalyst to silicon carbide in the base layer coating is 1:3.5-4.

5.

4. The infrared energy-saving coating according to any one of claims 1 to 3, wherein The mass ratio of cordierite to boron nitride in the base layer coating is 1:(0.9-1.1).

5. The method for preparing the infrared energy-saving coating according to any one of claims 1-4, characterized in that, The preparation method of the base layer coating includes: First, use water glass, sodium tripolyphosphate, and polyacrylamide to prepare water glass precursor; use bentonite and water to prepare bentonite solution with a concentration of 5%; use hydroxymethyl cellulose and water to prepare hydroxymethyl cellulose solution with a concentration of 2%; Then, add the water glass precursor, bentonite solution, hydroxymethyl cellulose solution, first surfactant, and first defoaming agent in sequence, stir at 300-600 rpm for 30 minutes, then add the thermal conductive aggregate, first stir at 40-60 rpm for 30 minutes, then stir at 1000 rpm for 2 hours, then add the remaining water and stir at 300-600 rpm for 45 minutes; The preparation method of the surface layer coating includes: First, prepare the bentonite solution and hydroxymethyl cellulose solution in the same way as the base layer coating; Then, add the sj-8050 high-temperature binder A component, stir at 300-500 rpm, then add the B component, continue stirring for 3h, then add the bentonite solution, hydroxymethyl cellulose solution, second surfactant, and second defoaming agent in sequence, stir until uniform, then add the wear-resistant aggregate, first stir at 40-60 rpm for 30 minutes, then stir at 1000 rpm for 1h, and finally add the remaining water and stir at 300-600 rpm for 45 minutes.

6. Use of the infrared energy-saving paint according to any one of claims 1 to 4 in a water-cooled wall coating, characterized in that, The water-cooled wall coating comprises a bottom layer and a surface layer, the surface layer is prepared by surface layer coating, the bottom layer is prepared by bottom layer coating, the bottom layer is between the water-cooled wall and the surface layer, the thickness of the bottom layer is 50-150 μm, and the thickness of the surface layer is 40-100 μm.

7. The infrared energy-saving coating in the water-cooled wall coating according to claim 6, wherein the processing method of the water-cooled wall coating comprises the following steps: firstly, the roughness of the water-cooled wall is treated by sand blasting process, the roughness is Rz=40-80 μm, the viscosity of the bottom layer coating and the surface layer coating is adjusted to 1.35-1.45 Pa·s; then, the bottom layer coating is sprayed on the water-cooled wall, and dried at 20-30 ℃ for 24 h, the thickness of the dried bottom layer is 20-150 μm; then, the surface layer coating is sprayed on the bottom layer, and dried at 20-30 ℃ for 24 h, the thickness of the dried surface layer is 40-100 μm. The processing method of the coating further comprises the step of curing treatment after the surface layer coating is dried; The curing treatment comprises the following steps: firstly, the temperature is raised to 80 ℃ at a rate of 2 ℃ / min, and kept for 60 min; then, the temperature is raised to 150 ℃ at a rate of 1.5 ℃ / min, and kept for 30 min; then, the temperature is raised to 250 ℃ at a rate of 3 ℃ / min, and kept for 45 min; then, the temperature is reduced to 80 ℃ at a rate of 1 ℃ / min, and naturally cooled. The wetting angle of the surface layer is >90°.

8. Use of the infrared energy saving coating according to claim 7 in a water cooled wall coating, characterized in that, ​ ​ 9. Use of the infrared energy saving coating according to claim 6 in a water cooled wall coating, characterized in that, The bottom layer has a coefficient of thermal expansion CTE = (9.2~9.8) x 10 -6 / K.

10. Use of an infrared energy saving coating according to any one of claims 6 to 9 in a water cooled wall coating, characterized in that, ​