Preparation method of anti-coking self-shedding ceramic coating for heating surface of garbage incinerator

Abstract

The present invention relates to a method for preparing an anti-coking self-shedding ceramic coating for the heating surface of a waste incinerator, belonging to the technical field of anti-slagging coating technology. The operation steps are as follows: 1. sandblasting the heating surface of the waste incinerator; 2. preparing a nickel-based alloy coating on the heating surface; 3. preparing a first ceramic coating on the nickel-based alloy coating; 4. laying graphite paper and evenly adhering a first circular graphite sheet on the first ceramic coating; 5. brushing a second ceramic coating in the gap between adjacent circular graphite sheets, and then laying graphite paper and a second layer of circular graphite sheets according to step (4); repeating the operation once to form a multilayer composite coating of three layers of ceramic coating and three layers of graphite paper; 6. brushing an edge ceramic coating on the edge of the multilayer composite coating to obtain an anti-coking self-shedding ceramic coating; when the waste incinerator is in operation, the coating reacts at a high temperature of 850°C in the furnace to form a dense protective layer. The corrosion rate of the anti-coking self-shedding ceramic coating is reduced to <0.05 mm / year.

Description

Technical Field

[0001] The invention belongs to the technical field of anti-slagging coating technology, and particularly relates to a method for preparing an anti-coking self-shedding ceramic coating for a heating surface of a garbage incinerator. Background Art

[0002] With the acceleration of urbanization, the amount of garbage continues to increase, and garbage disposal has become a very important task. At present, one of the commonly used methods of garbage disposal is garbage incineration, which converts garbage into energy or reduces its volume by burning it at high temperatures. In the garbage incineration process, the heating surface of the garbage incinerator operates in a high-temperature environment for a long time and is often corroded by the corrosive gases, solid particles and high-temperature ash produced by the combustion of garbage. It is very easy to cause coking and ash accumulation, which leads to coking. The coking problem will affect the stability of heat transfer, reduce the negative pressure, increase the flue gas temperature, cause abnormal temperature transmission problems and force the normal operation of the incinerator to stop. Severe cases will seriously affect the safe and stable operation of the boiler.

[0003] Existing anti-coking technologies for waste incinerators mainly include mechanical cleaning, traditional chemical protective coatings and soot blowing devices. Although these methods can improve the wear resistance and corrosion resistance of the equipment surface, facing the complex and harsh operating environment of waste incinerators, these methods still have defects such as frequent shutdowns, easy failure of coatings, incomplete cleaning and high maintenance costs.

[0004] In order to solve these problems, the present invention provides a ceramic coating technology that can prevent coking and self-shedding, by forming a composite coating on the surface of the furnace wall. Summary of the Invention

[0005] In order to achieve the goal of improving the anti-coking ability of the heating surface of the waste incinerator and making the coke fall off automatically, thereby improving the working efficiency and service life of the waste incinerator, the present invention provides a method for preparing an anti-coking self-falling ceramic coating for the heating surface of the waste incinerator.

[0006] A method for preparing a coking-proof self-shedding ceramic coating for the heating surface of a waste incinerator, the operating steps are as follows:

[0007] (1) Sandblasting

[0008] The heating surface of the waste incinerator is a metal surface; the metal surface is sandblasted using quartz sand to make the roughness Ra value of the metal surface 3.5 to 6.0 μm, thereby obtaining a sandblasted metal surface;

[0009] (2) Preparation of nickel-based alloy coating

[0010] Arc spraying a nickel-based alloy material on a sandblasted metal surface to obtain a nickel-based alloy coating having a thickness greater than 100 μm;

[0011] (3) Preparation of the first ceramic coating

[0012] Applying a first ceramic coating on the nickel-based alloy coating; the material of the first ceramic coating is a liquid mixture of 50% to 70% by mass of zirconium oxide and 30% to 50% by mass of aluminum oxide;

[0013] (4) Laying graphite paper

[0014] (4.1) Before the first ceramic coating is dry, lay a layer of graphite paper on the first ceramic coating;

[0015] (4.2) Evenly adhere a first layer of graphite sheets on the graphite paper. The graphite sheets are circular or square graphite sheets. The first layer of graphite sheets is arranged in a crisscross pattern.

[0016] (5) Preparation of multilayer composite coatings

[0017] After the graphite paper is dried, a second ceramic coating is applied by brushing in the gap area between adjacent graphite sheets of the first layer of graphite sheets;

[0018] Laying a second layer of graphite paper on the second ceramic coating; evenly adhering a second layer of graphite sheets on the second layer of graphite paper; and staggering the positions of adjacent layers of graphite sheets;

[0019] Repeat step (5) once to finally form a multilayer composite coating consisting of three ceramic coating layers and three graphite paper layers;

[0020] (6) Preparation of edge ceramic coating

[0021] After the multi-layer composite coating is dried, the edge of the multi-layer composite coating is sealed and a layer of edge ceramic coating is applied to ensure that the edge of the graphite paper is not exposed to high-temperature flue gas, thereby obtaining an anti-coking and self-shedding ceramic coating;

[0022] When the waste incinerator is in operation, the three-layer ceramic coating reacts with oxygen in the air at a high temperature of 850°C inside the furnace to form a dense protective layer;

[0023] The anti-coking self-shedding ceramic coating reduces its corrosion rate to <0.05mm / year in a continuous high-temperature environment of 850°C. After 1,000 hours of high-temperature operation testing, the coating's adhesion remains at ≥10 MPa, its protective performance retention rate exceeds 95%, and its friction coefficient changes by less than 5%.

[0024] Further technical solutions are as follows:

[0025] In step (1), the particle size of the quartz sand is 0.6 to 0.8 mm; the sandblasting pressure is 0.5 to 0.7 MPa, and the processing time is 15 to 18 minutes.

[0026] In step (2), the material of the nickel-based alloy coating is 80Ni-20Cr solid solution strengthened high temperature alloy, and the thickness of the nickel-based alloy coating is 100 to 150 μm.

[0027] The material of the first ceramic coating is a liquid mixture of zirconium oxide and aluminum oxide, and the thickness of the first ceramic coating is 200-300 μm; the materials and thicknesses of the three ceramic coatings are the same.

[0028] The preparation steps of the liquid mixture are as follows:

[0029] (3.1) Mix 50% to 70% by mass of zirconium oxide powder and 30% to 50% by mass of aluminum oxide powder in appropriate proportions to obtain a mixture;

[0030] (3.2) Add deionized water or an alcohol dispersant in an amount of 30% to 50% by mass of the mixture, and disperse by mechanical stirring or ultrasonic dispersion to obtain a suspension;

[0031] (3.3) The suspension is reacted in a high-temperature, high-pressure environment at a temperature of 200°C and a pressure of 2 MPa for 2 hours to obtain a liquid mixture with good stability.

[0032] In step (3.2), the alcohol dispersant is ethanol or isopropanol.

[0033] In step (3.2), the mechanical stirring dispersion conditions are: a rotation speed of 800-1000 rpm and a stirring time of 30 minutes; the ultrasonic dispersion treatment conditions are: an ultrasonic frequency of 20-40 kHz and an ultrasonic time of 30 minutes.

[0034] In step (4.1), the thickness of the graphite paper is 0.2 mm.

[0035] In step (4.2), the diameter of the circular graphite sheet is 8 mm, and the spacing between adjacent circular graphite sheets is 20 mm.

[0036] In step (6), the thickness of the edge ceramic coating is 150 μm.

[0037] The beneficial technical effects of the present invention are embodied in the following aspects:

[0038] 1. Anti-coking and self-shedding function: This invention incorporates graphite flakes into the coating material to create a micro-void structure. When the incinerator is operating, the heated surface temperature is high, and the coating expands unevenly in certain areas. The lubricity and thermal stability of the graphite flakes make the coating surface prone to cracking, causing coke to fall through the cracks. This design effectively prevents the long-term accumulation of coke.

[0039] 2. High Heat and Corrosion Resistance: The ceramic coating offers excellent high-temperature resistance, withstanding temperatures up to 1400°C and resisting chemical decomposition in high-temperature environments. Furthermore, the multilayered composite structure of the nickel (Ni)-based alloy coating and the ceramic coating provides excellent corrosion resistance, effectively resisting the corrosive gases and solid particles generated by waste combustion. The nickel (Ni)-based alloy coating exhibits excellent oxidation and corrosion resistance, effectively enhancing the adhesion between the ceramic coating and the metal substrate.

[0040] 3. Self-repairing ability: The present invention utilizes the thermal conductivity and lubricity of graphite paper to help prevent high-temperature coking. The alternating structure of graphite paper and ceramic coating in the coating can expose the undamaged underlying coating when the local coating peels off, achieving a certain self-repairing effect and extending the service life of the coating.

[0041] 4. Experimental data, including tests conducted in a high-temperature corrosive environment, confirmed that applying the coating technology to the heating surfaces of a waste incinerator reduced coking by over 60%, increased self-shedding efficiency by 40%, and improved corrosion resistance by approximately 40%. The coating maintained excellent adhesion and protective properties after 1,000 hours of high-temperature operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of a waste incinerator.

[0043] Figure 2 for Figure 1 Schematic diagram of composite coating on the middle furnace wall pipe.

[0044] Figure 3 for Figure 2 Schematic diagram of the arrangement of graphite discs on graphite paper. DETAILED DESCRIPTION

[0045] The present invention will be further described in detail below through embodiments with reference to the accompanying drawings. Example 1

[0046] The steps for preparing a coking-proof self-shedding ceramic coating for the heating surface of a waste incinerator are as follows:

[0047] (1) Sandblasting

[0048] See also Figure 1 The heating surface of the waste incinerator, i.e., the metal surface, was sandblasted using quartz sand with a particle size of 0.8 mm. The sandblasting pressure was 0.5 MPa and the treatment time was 15 minutes. The surface roughness Ra of the metal after sandblasting was measured to be 4.5 μm, thus obtaining a sandblasted metal surface.

[0049] (2) Preparation of nickel-based alloy coating

[0050] A nickel (Ni)-based alloy coating with a thickness of 120 μm is sprayed on a sandblasted metal surface using an arc spraying device. The material of the nickel-based alloy coating is an 80Ni-20Cr solid solution strengthened high-temperature alloy.

[0051] (3) Preparation of the first ceramic coating

[0052] A first ceramic coating with a thickness of 250 μm is brushed on the nickel-based alloy coating.

[0053] The material of the first ceramic coating is a liquid mixture of zirconium oxide and aluminum oxide. The steps for preparing the liquid mixture are as follows:

[0054] (3.1) 70% by mass of zirconium oxide powder and 30% by mass of aluminum oxide powder are mixed in appropriate proportions to obtain a mixture;

[0055] (3.2) Add deionized water or an alcohol dispersant in an amount equal to 50% by mass of the mixture and disperse under mechanical stirring at 1000 rpm for 30 minutes to obtain a suspension.

[0056] (3.3) The suspension is reacted in a high-temperature, high-pressure environment at a temperature of 200°C and a pressure of 2 MPa for 2 hours to obtain a liquid mixture with good stability.

[0057] (4) Laying graphite paper

[0058] (4.1) Before the first ceramic coating is dry, lay a layer of graphite paper with a thickness of 0.2 mm on the first ceramic coating;

[0059] (4.2) See Figure 3 , the first layer of circular graphite sheets is evenly pasted on the graphite paper. The diameter of the circular graphite sheets is 8 mm, the spacing between adjacent circular graphite sheets is 20 mm, and they are arranged in a criss-cross manner.

[0060] (5) Preparation of multilayer composite coatings

[0061] After the graphite paper is dried, a second ceramic coating with a thickness of 250 μm is applied to the gap area between adjacent circular graphite sheets of the first layer; when applying the second ceramic coating, the circular graphite sheets cannot be covered to ensure that the circular graphite sheets remain exposed.

[0062] A second layer of graphite paper is laid on the second ceramic coating; a second layer of circular graphite sheets is evenly adhered on the second layer of graphite paper; and the positions of the circular graphite sheets in adjacent layers are staggered.

[0063] Repeat step (5) once, see Figure 2 , and finally formed a multilayer composite coating of three layers of ceramic coating and three layers of graphite paper.

[0064] (6) Preparation of edge ceramic coating

[0065] After the multi-layer composite coating is dried, the edge of the multi-layer composite coating is sealed and a layer of 150 μm thick edge ceramic coating is applied to ensure that the edge of the graphite paper is not exposed to high-temperature flue gas, thereby obtaining an anti-coking and self-shedding ceramic coating.

[0066] When the waste incinerator operates at 850°C, the three-layer ceramic coating reacts with the oxygen in the air at the high temperature of 850°C in the furnace to form a dense protective layer.

[0067] The anti-coking self-shedding ceramic coating of Example 1 has a corrosion rate reduced to <0.05 mm / year in a high-temperature environment of 850°C. After 1000 hours of high-temperature operation testing, the adhesion of the coating remains at ≥10 MPa, the protective performance retention rate exceeds 95%, and the friction coefficient changes by less than 5%.

[0068] After 500 hours of high-temperature operation in the incinerator, the amount of coke deposited on the heating surface was reduced by 55%, and the self-shedding efficiency was increased by 35%. The anti-coking, self-shedding ceramic coating remained intact at a maximum temperature of 1250°C, without flaking or cracking. Its corrosion resistance was improved by 40%, effectively extending the equipment's operating time. Example 2

[0069] The steps for preparing a coking-proof self-shedding ceramic coating for the heating surface of a waste incinerator are as follows:

[0070] (1) Sandblasting

[0071] The heating surface of the waste incinerator (i.e., the metal surface) was sandblasted using quartz sand with a particle size of 0.6 mm at a pressure of 0.7 MPa for 18 minutes. The surface roughness Ra of the metal after sandblasting was measured to be 5.0 μm, thus obtaining a sandblasted metal surface.

[0072] (2) Preparation of nickel-based alloy coating

[0073] A nickel (Ni)-based alloy coating with a thickness of 140 μm is sprayed on a sandblasted metal surface using an arc spraying device. The material of the nickel-based alloy coating is an 80Ni-20Cr solid solution strengthened high temperature alloy.

[0074] (3) Preparation of the first ceramic coating

[0075] A first ceramic coating with a thickness of 220 μm is brushed on the nickel-based alloy coating.

[0076] The material of the first ceramic coating is a liquid mixture of zirconium oxide and aluminum oxide. The steps for preparing the liquid mixture are as follows:

[0077] (3.1) 50% by mass of zirconium oxide powder and 50% by mass of aluminum oxide powder are mixed in appropriate proportions to obtain a mixture;

[0078] (3.2) Add deionized water or an alcohol dispersant in an amount of 30% by mass to the mixture and disperse under ultrasonic waves at a frequency of 40 kHz for 30 minutes to obtain a suspension;

[0079] (3.3) The suspension is reacted in a high-temperature, high-pressure environment at a temperature of 200°C and a pressure of 2 MPa for 2 hours to obtain a liquid mixture with good stability.

[0080] (4) Laying graphite paper

[0081] (4.1) Before the first ceramic coating is dry, lay a layer of graphite paper with a thickness of 0.3 mm on the first ceramic coating;

[0082] (4.2) Evenly adhere the first layer of square graphite sheets on the graphite paper. The length and width of the square graphite sheets are both 10 mm, and the spacing between adjacent square graphite sheets is 25 mm. They are arranged in a crisscross pattern.

[0083] (5) Preparation of multilayer composite coatings

[0084] The operation of step (5) in this embodiment 2 is the same as the operation of step (5) in embodiment 1.

[0085] (6) Preparation of edge ceramic coating

[0086] The operation of step (6) in this embodiment 2 is the same as the operation of step (6) in embodiment 1.

[0087] When the waste incinerator operates at 850°C, the three-layer ceramic coating reacts with the oxygen in the air at the high temperature of 850°C in the furnace to form a dense protective layer.

[0088] The anti-coking self-shedding ceramic coating of Example 2 has a corrosion rate reduced to <0.05 mm / year in a high-temperature environment of 850°C. After 1000 hours of high-temperature operation testing, the adhesion of the coating remains at ≥10 MPa, the protective performance retention rate exceeds 95%, and the friction coefficient changes by less than 5%.

[0089] After 1,000 hours of high-temperature operation in the incinerator, the amount of coke deposited on the heating surface was reduced by 60%, and the self-shedding efficiency was increased by 40%. The anti-coking, self-shedding ceramic coating remained intact at a maximum temperature of 1,250°C, without flaking or cracking. Its corrosion resistance was improved by 45%, effectively extending the equipment's operating time.

[0090] It will be easily understood by those skilled in the art that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a coking-proof self-shedding ceramic coating for the heating surface of a waste incinerator, characterized in that: The steps are as follows: (1) Sandblasting The heating surface of the waste incinerator is a metal surface; the metal surface is sandblasted using quartz sand to make the roughness Ra value of the metal surface 3.5 to 6.0 μm, thereby obtaining a sandblasted metal surface; (2) Preparation of nickel-based alloy coating Arc spraying a nickel-based alloy material on a sandblasted metal surface to obtain a nickel-based alloy coating having a thickness greater than 100 μm; (3) Preparation of the first ceramic coating Applying a first ceramic coating on the nickel-based alloy coating; the material of the first ceramic coating is a liquid mixture of 50% to 70% by mass of zirconium oxide and 30% to 50% by mass of aluminum oxide; The preparation steps of the liquid mixture are as follows: (3.1) Mix 50% to 70% by mass of zirconium oxide powder and 30% to 50% by mass of aluminum oxide powder in appropriate proportions to obtain a mixture; (3.2) Add deionized water or an alcohol dispersant in an amount of 30% to 50% by mass of the mixture, and disperse by mechanical stirring or ultrasonic dispersion to obtain a suspension; (3.3) reacting the suspension in a high-temperature, high-pressure environment at 200°C and 2 MPa for 2 hours to obtain a liquid mixture having good stability; (4) Laying graphite paper (4.1) Before the first ceramic coating is dry, lay a layer of graphite paper on the first ceramic coating; (4.2) Evenly adhere a first layer of graphite sheets on the graphite paper. The graphite sheets are circular or square graphite sheets. The first layer of graphite sheets are arranged in a crisscross pattern. (5) Preparation of multilayer composite coatings After the graphite paper is dried, a second ceramic coating is applied by brushing in the gap area between adjacent graphite sheets of the first layer of graphite sheets; Laying a second layer of graphite paper on the second ceramic coating; evenly adhering a second layer of graphite sheets on the second layer of graphite paper; and staggering the positions of adjacent layers of graphite sheets; Repeat step (5) once to finally form a multilayer composite coating consisting of three ceramic coating layers and three graphite paper layers; (6) Preparation of edge ceramic coating After the multi-layer composite coating is dried, the edge of the multi-layer composite coating is sealed and a layer of edge ceramic coating is applied to ensure that the edge of the graphite paper is not exposed to high-temperature flue gas, thereby obtaining an anti-coking and self-shedding ceramic coating; When the waste incinerator is in operation, the three-layer ceramic coating reacts with oxygen in the air at a high temperature of 850°C inside the furnace to form a dense protective layer; The anti-coking, self-shedding ceramic coating reduces its corrosion rate to <0.05 mm / year in a continuous high-temperature environment of 850°C. After 1,000 hours of high-temperature operation testing, the coating's adhesion remains at ≥10 MPa, its protective performance retention rate exceeds 95%, and its friction coefficient changes by less than 5%. The thickness of the first ceramic coating is 200-300 μm; the materials and thicknesses of the three ceramic coatings are the same.

2. The preparation method according to claim 1, wherein: In step (1), the particle size of the quartz sand is 0.6 to 0.8 mm; the sandblasting pressure is 0.5 to 0.7 MPa, and the processing time is 15 to 18 minutes.

3. The preparation method according to claim 1, wherein: In step (2), the material of the nickel-based alloy coating is 80Ni-20Cr solid solution strengthened high temperature alloy, and the thickness of the nickel-based alloy coating is 100 to 150 μm.

4. The preparation method according to claim 1, wherein: In step (3.2), the alcohol dispersant is ethanol or isopropanol.

5. The preparation method according to claim 1, wherein: In step (3.2), the mechanical stirring dispersion conditions are: a rotation speed of 800-1000 rpm and a stirring time of 30 minutes; the ultrasonic dispersion treatment conditions are: an ultrasonic frequency of 20-40 kHz and an ultrasonic time of 30 minutes.

6. The preparation method according to claim 1, wherein: In step (4.1), the thickness of the graphite paper is 0.2 mm.

7. The preparation method according to claim 1, wherein: In step (4.2), the diameter of the circular graphite sheet is 8 mm, and the spacing between adjacent circular graphite sheets is 20 mm.

8. The preparation method according to claim 1, wherein: In step (6), the thickness of the edge ceramic coating is 150 μm.

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