Anti-fouling coating for a boiler coal burner nozzle, a coating layer and preparation thereof

Abstract

The application discloses a kind of anti-fouling coating for boiler coal burner nozzle, coating and preparation method thereof, and the coating includes the following mass percentages of components:65~75wt% ceramic aggregate, 2~4wt% silicon dioxide, 1~3wt% chromium green, 0.5~2wt% magnesium oxide, 4~6wt% curing agent, 9~10wt% adhesive and 8~12wt% diluent;Ceramic aggregate includes zirconium silicate and hexagonal boron nitride;Silicon dioxide includes hydrophobic fumed silica and conventional scale silicon dioxide;Adhesive is aluminum dihydrogen phosphate.The coating is thermally cured into shape by using the temperature rise after boiler operation, which has low surface energy, smooth ceramic glaze and excellent performance of high temperature corrosion resistance, can effectively prevent the coking and plugging of burner nozzle, prolong the service life of burner, and has good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of special functional coatings, and relates to an anti-fouling coating for a boiler coal burner nozzle, a coating layer and a preparation method thereof, in particular to an anti-fouling coating for a boiler coal burner nozzle, an anti-fouling coating layer for a boiler coal burner nozzle and a method for obtaining an anti-fouling coating suitable for a boiler coal burner nozzle by adding an anti-adhesion filler component, optimizing a ceramic aggregate formula and constructing a low-surface-energy coating surface. BACKGROUND

[0002] A boiler coal burner is a device for spraying coal powder into a furnace for combustion. During operation, due to unreasonable boiler combustion mode, low primary air speed or too fine coal powder, the ignition point of the coal powder entering the furnace is too close to the burner, which can cause the outlet of the running burner to be coked, and in severe cases, the outlet of the burner can be completely blocked. This can cause the primary air pressure of the coal pulverizing system to rise, and also increase the coal powder concentration and primary air volume of the primary air of another group of burners, which increases the thermal load of the group of burners, and the thermal load and flow field distribution in the furnace are uneven, further causing the water-cooled wall of the heating surface to coke and the platen superheater to coke. Therefore, the coking and blocking of the outlet of the burner not only reduces the efficiency of the boiler, but also affects the stability and safety of the system, and has an important influence on safety production.

[0003] For the problem of coking and blocking of the burner, the commonly used solutions are to optimize the design of the burner and to manually clean and maintain it regularly. Optimizing the design of the burner mainly controls the temperature of the coal powder outlet by adjusting the temperature control and the design of the nozzle, thereby reducing the risk of coking, but current experience shows that due to interference factors such as air volume, coal powder quality and load fluctuation during equipment operation, this method has limited effect on alleviating coking. Manual regular cleaning and maintenance is an effective method for removing coke, which can well control the thickness of the coke layer, but this method can only be used during the shutdown and maintenance period, and the coke layer is usually very thick during the shutdown and maintenance period, so this method cannot effectively alleviate the coking problem during system operation.

[0004] CN 101067052A discloses a manufacturing method of a hot-melt refractory heat-insulating coating and a utilization method thereof, which realizes ceramization through hot melting by utilizing the heat generation of the base material, which can meet the effect of refractory heat insulation, but there is still a large space for improvement in the anti-fouling effect.

[0005] Therefore, it is of great practical significance to develop an anti-fouling protective coating for a boiler coal burner nozzle. SUMMARY

[0006] In view of the above defects in the prior art, the present application provides an anti-fouling protective coating for a boiler coal powder burner nozzle to improve the overall energy efficiency of the boiler system, in particular, an anti-fouling coating for a boiler coal powder burner nozzle, an anti-fouling coating for a boiler coal powder burner nozzle, and a method for obtaining an anti-fouling coating for a boiler coal powder burner nozzle by adding an anti-adhesion filler component, optimizing the ceramic aggregate formula, and constructing a low surface energy coating surface, which can obtain a coating with excellent high temperature molten coal ash adhesion resistance function, overcoming the defects of the existing boiler coal powder burner nozzle anti-adhesion means, which has poor effect and still has a large improvement space.

[0007] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0008] An anti-fouling coating for a boiler coal powder burner nozzle comprises the following components by mass percentage:

[0009] 65-75wt% ceramic aggregate, 2-4wt% silicon dioxide, 1-3wt% chromium green, 0.5-2wt% magnesium oxide, 4-6wt% curing agent, 9-10wt% adhesive and 8-12wt% diluent;

[0010] The ceramic aggregate comprises zirconium silicate and hexagonal boron nitride;

[0011] The silicon dioxide comprises hydrophobic fumed silica and conventional size silica;

[0012] The adhesive is aluminum dihydrogen phosphate.

[0013] The present application uses hexagonal boron nitride and zirconium silicate as the main ceramic aggregate, which has stable chemical properties and is chemically inert to all molten metals, can greatly improve the anti-adhesion ability of the coating, has good high temperature resistance and corrosion resistance, and has good bonding force and anti-adhesion, so it has good anti-coking properties for high temperature molten coal ash at the burner nozzle; aluminum dihydrogen phosphate is used as an inorganic adhesive component, which can make the coating and the substrate more firmly bonded; magnesium oxide and curing agent can improve the hardening and forming quality and speed of the coating, also reduce the forming temperature of the material, and play the role of sintering aid; mixing two sizes and physical properties of silica can improve the high temperature resistance and corrosion resistance of the coating; the anti-adhesion effect of the anti-fouling coating for a boiler coal powder burner nozzle prepared by the above components is good, and the application prospect is good.

[0014] As a preferred technical solution:

[0015] The anti-fouling coating for a boiler coal powder burner nozzle as described above comprises the following components by mass percentage: 69wt% ceramic aggregate, 4wt% silicon dioxide, 2wt% chromium green, 1wt% magnesium oxide, 6wt% curing agent, 10wt% adhesive and 8wt% diluent.

[0016] The anti-fouling coating for a boiler coal burner nozzle as described above, the mass ratio of zirconium silicate and hexagonal boron nitride in the ceramic aggregate is 4:3.

[0017] The mass ratio of the hydrophobic fumed silica and the conventional size silica is 1:1.

[0018] The particle size of the hydrophobic fumed silica is 7-40 nm, and the particle size of the conventional size silica is 1-3 microns.

[0019] The curing agent includes gypsum and alum, and the chemical compositions of gypsum and alum are calcium sulfate and potassium aluminum sulfate respectively, which are added simultaneously when mixed with the ceramic aggregate, and the curing agent can effectively improve the strength of the coating and enhance the erosion resistance to high-speed pulverized coal.

[0020] The diluent is water. The diluent can be increased according to the viscosity of the filler dispersion, the use time after the slurry is prepared, and the site adaptation of cold spraying construction.

[0021] The anti-fouling coating for a boiler coal burner nozzle as described above, the curing agent is a mixture of gypsum and alum with a mass ratio of 1:1.

[0022] The anti-fouling coating for a boiler coal burner nozzle as described above, the preparation method of the ceramic aggregate is as follows:

[0023] After the zirconium silicate, hexagonal boron nitride powder and high-temperature binder are fully mixed according to a mass ratio of 4:3:3, they are placed in a muffle furnace at 900 DEG C and sintered for 6-8 hours, then crushed and ground by a planetary ball mill for 2 hours, then the obtained grinding material is mixed with the high-temperature binder according to a mass ratio of 8:2, and then heated to 750 DEG C in a muffle furnace for 2-3 hours, and then ground by a ball mill for 4-5 hours, and then filtered and dried after adding water to obtain the ceramic aggregate. In the preparation process, the sintering and crushing are carried out twice, and the temperature of each sintering is gradually reduced, and repeated sintering can uniformly wrap the filler particles with multiple layers of binder.

[0024] The anti-fouling coating for a boiler coal burner nozzle as described above, the high-temperature binder is a sodium silicate solution.

[0025] The filtering refers to filtering with a 200-mesh sieve.

[0026] The application also provides a preparation method of the anti-fouling coating for a boiler coal burner nozzle as described above, the ceramic aggregate, silica, chrome green, magnesium oxide, curing agent, adhesive and diluent are dispersed and mixed according to the mass percentage, and are sequentially added according to the above-mentioned order during mixing, so as to prepare the anti-fouling coating for a boiler coal burner nozzle.

[0027] Furthermore, the application also provides an anti-fouling coating for a boiler coal burner nozzle, which is prepared by coating the anti-fouling coating for a boiler coal burner nozzle as described above on the nozzle of the boiler coal burner by cold spraying and then curing and forming by in-furnace heat curing.

[0028] As a preferred technical solution:

[0029] The preparation method of the anti-fouling coating for a boiler coal burner nozzle as described above is to perform shadow drying at 5-45 DEG C for 48 hours after cold spraying; and the in-furnace heat curing forming refers to keeping at an environment greater than 200 DEG C for more than 2 hours.

[0030] The above technical solution is only one possible technical solution of the application, and the protection scope of the application is not limited to this, and those skilled in the art can reasonably adjust the specific design according to actual needs.

[0031] The above application has the following advantages or beneficial effects:

[0032] (1) The anti-corrosion and anti-fouling protective coating for a boiler coal burner nozzle of the application uses hexagonal boron nitride and zirconium silicate as main ceramic aggregates, which are chemically stable and chemically inert to all molten metals, can greatly improve the anti-adhesion ability of the coating, and naturally have good high-temperature corrosion resistance and good adhesion, so the coating has good anti-coking properties for high-temperature molten coal ash at the nozzle of the burner;

[0033] (2) The anti-corrosion and anti-fouling protective coating for a boiler coal burner nozzle of the application uses aluminum dihydrogen phosphate as an inorganic adhesive component, which can make the coating and the substrate more firmly combined;

[0034] (3) The anti-corrosion and anti-fouling protective coating for a boiler coal burner nozzle of the application uses magnesium oxide and a curing agent to improve the hardening and forming quality and speed of the coating, and also reduces the forming temperature of the material and plays the role of a sintering aid;

[0035] (4) The anti-corrosion and anti-fouling protective coating for a boiler coal burner nozzle of the application uses two sizes and physical properties of silicon dioxide to improve the high-temperature resistance and corrosion resistance of the coating;

[0036] (5) The anti-corrosion and anti-fouling protective coating for a boiler coal burner nozzle of the application has good anti-adhesion effect after the coating for a boiler coal burner nozzle prepared by the above components is formed;

[0037] (6) The anti-corrosion and anti-fouling protective coating for a boiler coal burner nozzle of the application can be completed by in-furnace heat curing after cold spraying, and the construction method is convenient and has good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0038] The present application, its features, shapes and advantages will become more apparent from the following detailed description of non-limiting embodiments, with reference to the accompanying drawings. The same reference numbers in all the drawings indicate the same parts. The drawings are not necessarily drawn to scale, the emphasis being on illustrating the principles of the application.

[0039] Figure 1 Preparation process route map of the anti-corrosion and anti-fouling protective coating for the boiler coal burner nozzle of the present application;

[0040] Figure 2 Contact angle characterization diagram of the anti-corrosion and anti-fouling protective coating for the boiler coal burner nozzle prepared in Example 1 and the surface without coating. DETAILED DESCRIPTION

[0041] The present application will be further described below in conjunction with the accompanying drawings and specific examples, but not as a limitation of the present application.

[0042] Example 1

[0043] A preparation method of an anti-corrosion and anti-fouling protective coating for a boiler coal burner nozzle, comprising the following steps (preparation process route map as shown in Figure 1 .

[0044] (1) Preparation of ceramic aggregate:

[0045] Take 40g of hexagonal boron nitride, 30g of zirconium silicate and 30g of sodium silicate solution, uniformly mix, place in a 900℃ muffle furnace for high temperature sintering for 6 hours, take out, crush and grind for 2 hours, then uniformly mix 80g of the ground material with 20g of sodium silicate solution, place in a 750℃ muffle furnace for high temperature sintering for 2 hours, take out, crush and grind for 4 hours, add pure water to a 200 mesh sieve, filter and dry to obtain the ceramic aggregate;

[0046] (2) Take 69g of the ceramic aggregate, 4g of silicon dioxide (2g of hydrophobic fumed silica with a particle size of 7-40nm and 2g of conventional scale silicon dioxide with a particle size of 1-3μm), 2g of chrome green, 1g of magnesium oxide, 6g of curing agent (3g of gypsum and 3g of alum), 10g of aluminum dihydrogen phosphate and 8g of water, uniformly mix, and the anti-corrosion and anti-fouling protective coating for the boiler coal burner nozzle is obtained.

[0047] Test the anti-bonding performance of the anti-corrosion and anti-fouling protective coating for the boiler coal burner nozzle prepared in Example 1, the operation process is as follows:

[0048] First, the nickel-chromium alloy steel material substrate (same as the commonly used material of the coal burner nozzle) of 50x50x3mm is sandblasted for cleaning treatment, the boiler coal burner nozzle corrosion and scale resistant protective coating in Example 1 is sprayed on the surface of the substrate, the thickness is about 0.8mm, after room temperature air drying for 48 hours, the thickness is thinned to 0.4mm, then the sample is placed in a muffle furnace, the temperature is raised from room temperature to 200℃ at a rate of 3℃ / min, kept constant for 4 hours, then raised from 200℃ to 600℃ at a rate of 5℃ / min, kept constant for 2 hours, and then cooled to room temperature with the furnace, the preparation of the boiler coal burner nozzle corrosion and scale resistant protective coating is completed.

[0049] The contact angle can represent the surface energy of the material, and the surface energy is one of the main factors affecting wall scaling. The larger the contact angle, the smaller the surface energy of the material, and the better the anti-scaling performance. Accordingly, the contact angle test method is used to characterize the anti-sticking performance of the surface.

[0050] The contact angle test sets the surface of the boiler coal burner nozzle corrosion and scale resistant protective coating and the surface of the uncoated steel as a comparison, 2g of coal ash pressed into a block is placed on the surface of each to simulate the coking phenomenon of the nozzle when the coal powder is converted into a molten state at high temperature. Then the two samples are placed in a muffle furnace and heated to 750℃, the change in the shape of the coal ash on the different surfaces is observed, and the change in the contact angle is recorded, as shown in the experimental graph. Figure 2

[0051] As can be seen from Figure 2 at 750℃, the coal ash shows a molten state, the contact angle on the surface of the boiler coal burner nozzle corrosion and scale resistant protective coating is larger, while the contact angle on the surface of the uncoated steel is smaller, indicating that the anti-sticking performance of the coating is much better than that of the uncoated steel surface.

[0052] Example 2

[0053] A method for preparing a boiler coal burner nozzle corrosion and scale resistant protective coating, which is basically the same as Example 1, except that 68g of ceramic aggregate, 2g of silicon dioxide, 2g of chrome green, 2g of magnesium oxide, 6g of curing agent (3g of gypsum and 3g of alum), 10g of aluminum dihydrogen phosphate and 12g of water are uniformly mixed, after preparation, the sample is sprayed and air dried, then the sample is placed in a muffle furnace and heated from room temperature to 200℃ at a rate of 2℃ / min, kept constant for 4 hours, then raised from 200℃ to 540℃ at a rate of 4℃ / min, kept constant for 2 hours, and then cooled to room temperature with the furnace, the preparation of the boiler coal burner nozzle corrosion and scale resistant protective coating is completed. Increasing the ratio of magnesium oxide and water can reduce the sintering temperature of the coating.

[0054] Example 3

[0055] ​A preparation method of the anti-corrosion and anti-fouling protective coating for the boiler coal burner nozzle is basically the same as that in Embodiment 1, except that 73g of ceramic aggregate, 2g of silicon dioxide, 3g of chromium green, 1g of magnesium oxide, 4g of curing agent (2g of gypsum and 2g of alum), 9g of aluminum dihydrogen phosphate and 8g of water are uniformly mixed, and after preparation, the sample is sprayed and dried, then placed in a muffle furnace, and heated from room temperature to 200℃ at a rate of 2℃ / min, kept at 200℃ for 4 hours, then heated from 200℃ to 600℃ at a rate of 5℃ / min, kept at 600℃ for 4 hours, and then cooled to room temperature in the furnace, and the preparation of the anti-corrosion and anti-fouling protective coating for the boiler coal burner nozzle is completed. The ceramic aggregate and chromium green components are added, the corrosion resistance of the coating is improved, and the high-temperature sintering time is increased.

[0056] Embodiment 4

[0057] A preparation method of the anti-corrosion and anti-fouling protective coating for the boiler coal burner nozzle is basically the same as that in Embodiment 1, except that 73g of ceramic aggregate, 2g of silicon dioxide, 3g of chromium green, 1g of magnesium oxide, 4g of curing agent (2g of gypsum and 2g of alum), 9g of aluminum dihydrogen phosphate and 8g of water are uniformly mixed, and after preparation, the sample is sprayed and dried, then placed in a muffle furnace, and heated from room temperature to 200℃ at a rate of 2℃ / min, kept at 200℃ for 4 hours, then heated from 200℃ to 600℃ at a rate of 5℃ / min, kept at 600℃ for 4 hours, and then cooled to room temperature in the furnace, and the preparation of the anti-corrosion and anti-fouling protective coating for the boiler coal burner nozzle is completed. The ceramic aggregate and chromium green components are added, the corrosion resistance of the coating is improved, and the high-temperature sintering time is increased.

[0058] It has been verified that the anti-corrosion and anti-fouling protective coating for the boiler coal burner nozzle has the following advantages: hexagonal boron nitride and zirconium silicate are used as the main ceramic aggregate, which has stable chemical properties and is chemically inert to all molten metals, can greatly improve the anti-bonding ability of the coating, and has good high-temperature corrosion resistance and good bonding force and anti-bonding property, so it has good anti-coking properties for high-temperature molten coal ash at the burner nozzle; aluminum dihydrogen phosphate is used as the inorganic adhesive component, which can make the coating and the substrate more firmly combined; magnesium oxide and the curing agent can improve the hardening and forming quality and speed of the coating, reduce the forming temperature of the material, and also play the role of sintering aid; the two sizes and physical properties of silicon dioxide can improve the high-temperature and corrosion resistance of the coating; the anti-fouling coating for the boiler coal burner nozzle prepared by the above components has good anti-bonding effect after forming; the forming can be completed by cold spraying and then heat curing in the furnace, the construction method is convenient, and the application prospect is good.

[0059] Those skilled in the art should understand that those skilled in the art can make changes in combination with the prior art and the above embodiments, which will not be described here. Such changes do not affect the essential content of the present application, and will not be described here.

[0060] The preferred embodiments of the present application have been described. It is to be understood that the application is not limited to the above specific embodiments, and that devices and structures not described in detail should be understood to be implemented in the ordinary way in the art; any person skilled in the art can make many possible changes and modifications to the technical solutions of the present application, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of the present application, which does not affect the essential content of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, without departing from the content of the technical solutions of the present application, still belongs to the scope of protection of the technical solutions of the present application.

Claims

1. An anti-fouling coating for a boiler coal burner nozzle, characterized by: Comprise the following components by mass percentage: 65~75wt% ceramic aggregate, 2~4wt% silicon dioxide, 1~3wt% chromium green, 0.5~2wt% magnesium oxide, 4~6wt% curing agent, 9~10wt% adhesive and 8~12wt% diluent; The ceramic aggregate comprises zirconium silicate and hexagonal boron nitride; The silicon dioxide comprises hydrophobic fumed silica and conventional scale silica, the particle size of the conventional scale silica is 1~3μm; The adhesive is aluminum dihydrogen phosphate; The curing agent comprises gypsum and alum.

2. The anti-fouling coating for a boiler coal burner nozzle according to claim 1, characterized by, Comprise the following components by mass percentage: 69wt% ceramic aggregate, 4wt% silicon dioxide, 2wt% chromium green, 1wt% magnesium oxide, 6wt% curing agent, 10wt% adhesive and 8wt% diluent.

3. A boiler coal burner nozzle anti-fouling coating according to claim 2, characterized in that, The mass ratio of zirconium silicate and hexagonal boron nitride in the ceramic aggregate is 4:3; The mass ratio of hydrophobic fumed silica and conventional scale silica is 1:1; The particle size of the hydrophobic fumed silica is 7~40nm; The diluent is water.

4. A boiler coal burner nozzle anti-fouling coating according to claim 3, characterized in that, The curing agent is a mixture of gypsum and alum in a mass ratio of 1:

1.

5. A boiler coal burner nozzle anti-fouling coating according to claim 2, characterized in that, The preparation method of the ceramic aggregate is as follows: After the zirconium silicate, hexagonal boron nitride powder and high-temperature binder are mixed in a mass ratio of 4:3:3, they are placed in a muffle furnace at 900℃ and sintered for 6~8 hours. After sintering into blocks, they are broken and ground by a planetary ball mill for 2 hours. Then the obtained grinding material is mixed with the high-temperature binder in a mass ratio of 8:2, and heated to 750℃ in a muffle furnace for 2~3 hours. After sintering, they are ground by a ball mill for 4~5 hours. After adding water, they are filtered and dried to obtain the ceramic aggregate.

6. A boiler coal burner nozzle anti-fouling coating according to claim 5, characterized in that, The high-temperature binder is sodium silicate solution; The filtering refers to filtering with a 200-mesh sieve.

7. A method of preparing an anti-fouling coating for a boiler coal burner nozzle according to any one of claims 1 to 6, characterized in that, The ceramic aggregate, silicon dioxide, chromium green, magnesium oxide, curing agent, adhesive and diluent are dispersed and mixed according to the mass percentage. During mixing, they are added in the above-mentioned order one by one to prepare an anti-fouling coating for a boiler coal burner nozzle.

8. A scale-resistant coating for a boiler coal-burner nozzle, characterized by, The anti-fouling coating for a boiler coal burner nozzle as claimed in any one of claims 1~6 is coated on the nozzle of a boiler coal burner by cold spraying, and then solidified and formed by in-furnace heat curing.

9. A method of preparing an anti-fouling coating for a boiler coal combustor nozzle as claimed in claim 8, wherein, After cold spraying, it is dried in the shade at 5~45℃ for 48 hours. The in-furnace heat curing refers to keeping in an environment of greater than 200℃ for more than 2 hours.

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