A protective coating for an IGCC unit gasifier and a preparation method thereof

Abstract

The present invention relates to the field of gasifier protective coatings, and provides a protective coating for an IGCC gasifier and a preparation method thereof. The protective coating comprises the following raw materials, by weight: 40-50 parts aluminum oxide; 15-20 parts zirconium oxide; 8-12 parts silicon carbide; 4-6 parts chromium oxide; 3-5 parts yttrium oxide; 6-10 parts aluminum phosphate; 5-7 parts titanium oxide; 2-3 parts cerium oxide; 2-4 parts magnesium oxide; and 3-5 parts calcium aluminate. The protective coating has excellent high-temperature resistance, corrosion resistance, and wear resistance, as well as good thermal conductivity, good production economy and efficiency, and a longer service life.

Description

Technical Field

[0001] The present invention relates to the technical field of gasifier protective coatings, and in particular to a protective coating for an IGCC unit gasifier and a preparation method thereof. Background Art

[0002] The Integrated Gasification Combined Cycle (IGCC) power generation system is an advanced power system that combines coal gasification technology with an efficient combined cycle. It consists of two major components: the coal gasification and purification section and the gas-steam combined cycle power generation section. The gasifier is a crucial component of the entire cycle. Gasifiers operate in harsh conditions. High-temperature flue gas and hard particle corrosion and erosion cause significant corrosion, wear, and coking on the heating surface boiler tubes. However, there is currently no suitable protective coating for IGCC gasifiers, creating an urgent challenge in this field. Summary of the Invention

[0003] The present invention aims to solve at least one of the problems existing in the prior art and provides a protective coating for an IGCC unit gasifier and a preparation method thereof.

[0004] In one aspect of the present invention, a protective coating for a gasifier of an IGCC unit is provided. The protective coating comprises raw materials and their weight proportions are as follows: aluminum oxide: 40-50 parts; zirconium oxide: 15-20 parts; silicon carbide: 8-12 parts; chromium oxide: 4-6 parts; yttrium oxide: 3-5 parts; aluminum phosphate: 6-10 parts; titanium oxide: 5-7 parts; cerium oxide: 2-3 parts; magnesium oxide: 2-4 parts; and calcium aluminate: 3-5 parts.

[0005] Optionally, the alumina is obtained by high-purity alumina by the Bayer process or by calcining aluminum hydroxide at 500° C.-600° C., and is ball-milled to a particle size of D50≤1 μm and then spray-dried.

[0006] Optionally, the preparation method of the zirconium oxide comprises: synthesizing by coprecipitation method Nano powder is calcined at 600-800℃ and then spray granulated to obtain spray-grade powder.

[0007] Optionally, the silicon carbide is prepared by synthesizing crude SiC at high temperature through an Acheson method, and then air flow pulverizing the raw SiC to a D50 of ≤2 μm after acid washing and purification.

[0008] Optionally, the chromium oxide is prepared by thermally decomposing potassium dichromate at 800° C.-900° C. and then ball-milling to a D50 of ≤1 μm.

[0009] Optionally, the yttrium oxide is prepared by calcining at 800° C. by an oxalate precipitation method and high-energy ball milling to a D50 of ≤100 nm; and / or,

[0010] The cerium oxide is prepared by thermally decomposing cerium carbonate at 600° C. and then homogenizing under high pressure until D50 is less than or equal to 100 nm; and / or,

[0011] The preparation method of magnesium oxide comprises: lightly burning magnesite at 800° C. and then hydrating and dehydrating the magnesite to obtain nano-active magnesium oxide.

[0012] Another aspect of the present invention provides a method for preparing a protective coating for an IGCC unit gasifier, the method comprising:

[0013] S1. Weigh according to the formula ratio: aluminum oxide: 40-50 parts, zirconium oxide: 15-20 parts, silicon carbide: 8-12 parts, chromium oxide: 4-6 parts, yttrium oxide: 3-5 parts, aluminum phosphate: 6-10 parts, titanium oxide: 5-7 parts, cerium oxide: 2-3 parts, magnesium oxide: 2-4 parts, calcium aluminate: 3-5 parts; Pour the weighed powder into the mixer, dry mix at a set speed under nitrogen protection for a preset time, and randomly sample for XRF composition analysis to ensure uniform distribution of each component. If the error of each component meets the preset error requirement, execute S2 for spraying;

[0014] S2. After premixing is completed, spraying is performed on the heating surface of the gasifier boiler tube substrate to sandblast its surface roughness to meet the preset roughness requirements and clean it with acetone to remove oil and impurities. Kerosene 0.3L / min and oxygen 800L / min are controlled as fuel, the flame speed is greater than 2000m / s, and the spraying distance is 200mm-300mm to quickly deposit the silicon carbide hard material. After spraying, the substrate is immediately air-cooled to prevent thermal deformation. The coating porosity is less than 5% and the bonding strength is greater than 50MPa using a metallographic microscope;

[0015] S3. After spraying, post-processing is performed. The sprayed coating is placed in a box-type resistance furnace and heated to 600°C at a rate of 5°C / min. The temperature is maintained for 1 hour to activate the bonding between aluminum phosphate and calcium aluminate and eliminate residual stress. The coating is cooled to 200°C in the furnace and then air-cooled to prevent embrittlement of the coating. Finally, it is lightly polished with a diamond grinding wheel to a surface roughness Ra of less than 1μm. The coating area is laser remelted to increase the infrared emissivity and enhance the heat dissipation performance.

[0016] Optionally, after S3, it also includes:

[0017] S4. Perform a final quality test on the protective coating, wherein the final quality test includes a porosity test, a bonding strength test, and a coking rate test.

[0018] Another aspect of the present invention provides a gasifier heating surface, which includes the protective coating for the IGCC unit gasifier as described above; or, the gasifier heating surface includes a protective coating prepared according to the preparation method of the protective coating for the IGCC unit gasifier as described above.

[0019] Another aspect of the present invention provides a gasifier, which includes the gasifier heating surface described above.

[0020] Compared with the prior art, the present invention is that alumina and zirconia can form a dense ceramic layer to isolate the molten ash from contacting the tube wall, titanium dioxide as a black body material can improve the thermal radiation efficiency and reduce the temperature of the heated surface, chromium oxide can resist the corrosion of sodium and potassium in high-alkali coal, cerium dioxide can inhibit oxidation reactions, yttrium oxide can stabilize the zirconia lattice, silicon carbide and alumina can provide ultra-high thermal conductivity to avoid local overheating and coating failure, and magnesium oxide can adjust the thermal expansion coefficient to avoid thermal stress cracking. At the same time, the main materials alumina and zirconia are cost-controlled, and the aluminum phosphate binder does not require high-temperature sintering, which is suitable for rapid on-site construction. In summary, the protective coating for the gasifier of an IGCC unit provided by the present invention and the protective coating prepared by the preparation method of the protective coating for the gasifier of an IGCC unit provided by the present invention both have excellent high temperature resistance, corrosion resistance, and wear resistance, and good thermal conductivity, good preparation economy, preparation efficiency, and longer service life. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, each embodiment of the present invention is described in detail below. However, it will be understood by those skilled in the art that in each embodiment of the present invention, many technical details are provided to enable the reader to better understand the present invention. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present invention can be implemented. The division of the following embodiments is for convenience of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined and referenced with each other under the premise that there is no contradiction.

[0022] One embodiment of the present invention relates to a protective coating for an IGCC gasifier. The coating comprises the following raw materials, in parts by weight: aluminum oxide: 40-50 parts; zirconium oxide: 15-20 parts; silicon carbide: 8-12 parts; chromium oxide: 4-6 parts; yttrium oxide: 3-5 parts; aluminum phosphate: 6-10 parts; titanium oxide: 5-7 parts; cerium oxide: 2-3 parts; magnesium oxide: 2-4 parts; and calcium aluminate: 3-5 parts. All of the above raw materials can be purchased commercially.

[0023] Exemplarily, the alumina is prepared by high-purity alumina obtained by the Bayer process or by calcining aluminum hydroxide at 500° C.-600° C., and then ball-milling to a particle size of D50 ≤ 1 μm and spray-drying the resulting alumina.

[0024] Specifically, D50 refers to the median particle size in the particle size distribution. D50 ≤ 1 μm means that 50% of the particles in the sample have a particle size of less than or equal to 1 micron. In this embodiment, the sample is aluminum oxide. By limiting the particle size of aluminum oxide to D50 ≤ 1 μm, the uniformity and adhesion of the coating can be effectively improved.

[0025] Exemplary, the preparation method of zirconium oxide includes: synthesizing by coprecipitation method Nano powder is calcined at 600-800℃ and then spray granulated to obtain spray-grade powder.

[0026] Specifically, in the synthesis by coprecipitation method When the nanopowder is formed, an appropriate precipitant is added to a solution containing zirconium ions and yttrium ions to precipitate the two ions together to form a mixed hydroxide or carbonate precursor, which is then converted into the desired precursor through subsequent washing, drying and calcination steps. Nanopowder.

[0027] For example, silicon carbide is prepared by synthesizing crude SiC at high temperature through the Acheson method, and then air flow pulverizing the raw SiC to a D50 of ≤2 μm after purification by acid washing.

[0028] By controlling the particle size of silicon carbide to D50≤2μm, the performance of the protective coating can be significantly improved.

[0029] For example, chromium oxide is prepared by thermally decomposing potassium dichromate at 800° C.-900° C. and then ball-milling the resulting product to a D50 of ≤1 μm.

[0030] By controlling the particle size of chromium oxide to D50≤1μm, the performance of the protective coating can be further improved.

[0031] Exemplarily, yttrium oxide is prepared by calcining at 800° C. through an oxalate precipitation method and high-energy ball milling until D50 is ≤ 100 nm.

[0032] Specifically, the oxalate precipitation method involves reacting a soluble yttrium salt with oxalate ions to form a water-insoluble yttrium oxalate precipitate. This yttrium oxalate is then converted into pure yttrium oxide through calcination. By controlling the particle size of the yttrium oxide to a value of D50 ≤ 100 nm, the protective coating's high-temperature resistance, wear resistance, oxidation resistance, and corrosion resistance can be further enhanced. It also strengthens the coating's adhesion and thermal conductivity.

[0033] Exemplarily, cerium oxide is prepared by thermally decomposing cerium carbonate at 600° C. and then homogenizing under high pressure until D50 is ≤ 100 nm.

[0034] By controlling the particle size of cerium oxide to D50≤100nm, the high temperature resistance, wear resistance, oxidation resistance and other properties of the protective coating can be further improved.

[0035] Exemplarily, the preparation method of magnesium oxide includes: lightly burning magnesite at 800° C. and then hydrating and dehydrating it to obtain nano-active magnesium oxide.

[0036] Compared with the prior art, the present invention is that alumina and zirconia can form a dense ceramic layer to isolate the molten ash from contacting the tube wall, titanium dioxide as a black body material can improve the thermal radiation efficiency and reduce the temperature of the heated surface, chromium oxide can resist the corrosion of sodium and potassium in high-alkali coal, cerium dioxide can inhibit oxidation reactions, yttrium oxide can stabilize the zirconia lattice, silicon carbide and alumina can provide ultra-high thermal conductivity to avoid local overheating and coating failure, and magnesium oxide can adjust the thermal expansion coefficient to avoid thermal stress cracking. At the same time, the main materials alumina and zirconia are cost-controlled, and the aluminum phosphate binder does not require high-temperature sintering, which is suitable for rapid on-site construction. In summary, the protective coating for the gasification furnace of the IGCC unit provided by the present invention has excellent high-temperature resistance, corrosion resistance, and wear resistance, and has good thermal conductivity, good preparation economy, preparation efficiency, and longer service life.

[0037] Another embodiment of the present invention relates to a method for preparing a protective coating for an IGCC unit gasifier, including S1 to S3.

[0038] S1. Weigh according to the formula ratio: aluminum oxide: 40-50 parts, zirconium oxide: 15-20 parts, silicon carbide: 8-12 parts, chromium oxide: 4-6 parts, yttrium oxide: 3-5 parts, aluminum phosphate: 6-10 parts, titanium oxide: 5-7 parts, cerium oxide: 2-3 parts, magnesium oxide: 2-4 parts, calcium aluminate: 3-5 parts; pour the weighed powder into the mixer, dry mix at a set speed under nitrogen protection for a preset time, and randomly sample for XRF component analysis to ensure that the components are evenly distributed. If the error of each component meets the preset error requirement, execute S2 for spraying. Among them, the mixer can use a V-type mixer with a volume of 50L-100L to improve the mixing efficiency. The set speed of the mixer can be 30±2rpm. At this time, the preset time can be set to 2 hours to further improve the mixing efficiency. The preset flowability requirement can be set based on actual needs. For example, the preset flowability requirement can be set to greater than or equal to 25 seconds per 50 grams. XRF, short for X-ray Fluorescence, is widely used in non-destructive testing for material composition analysis. In this embodiment, XRF is used to analyze the components and their contents in powders. The preset tolerance can be set based on actual accuracy requirements. For example, the preset tolerance requirement can be set to ±1%.

[0039] S2. After premixing is completed, spraying is performed. The base of the boiler tube on the heating surface of the gasifier is sandblasted to ensure that its surface roughness meets the preset roughness requirements. It is then cleaned with acetone to remove oil stains and impurities. Kerosene is controlled at 0.3L / min and oxygen at 800L / min as fuel, with a flame speed greater than 2000m / s and a spraying distance of 200mm-300mm to ensure rapid deposition of the silicon carbide hard material. After spraying, the base is immediately air-cooled to prevent thermal deformation. The coating porosity is checked by metallographic microscope to ensure that it is less than 5% and the bonding strength is greater than 50MPa.

[0040] S3. After spraying, post-processing is performed. The sprayed coating is placed in a box-type resistance furnace and heated to 600°C at a rate of 5°C / min. The temperature is maintained for 1 hour to activate the bonding between aluminum phosphate and calcium aluminate and eliminate residual stress. The coating is cooled to 200°C in the furnace and then air-cooled to prevent embrittlement of the coating. Finally, it is lightly polished with a diamond grinding wheel to a surface roughness Ra of less than 1μm. The coating area is laser remelted to increase the infrared emissivity and enhance the heat dissipation performance.

[0041] Exemplarily, after S3, the method for preparing a protective coating for an IGCC gasifier further includes: S4. performing a final quality inspection on the protective coating. The final quality inspection includes a porosity inspection, a bonding strength inspection, and a coking rate inspection.

[0042] The protective coating prepared by the method for preparing a protective coating for an IGCC unit gasifier provided in an embodiment of the present invention has excellent comprehensive properties of high temperature resistance, corrosion resistance, and wear resistance, as well as good thermal conductivity, good preparation economy and efficiency, and a longer service life.

[0043] In order to enable those skilled in the art to better understand the above implementation, specific embodiments are used as examples for description below.

[0044] Example 1: A method for preparing a protective coating for an IGCC unit gasifier, wherein the protective coating is prepared according to the material components and weight fractions of Example 1 shown in Table 1 below.

[0045] Table 1 Material components and their weight fractions of the coatings in Examples 1 to 4

[0046]

[0047] In this embodiment, the method for preparing the protective coating for the gasifier of an IGCC unit includes the following steps S11 to S13.

[0048] S11. Weigh according to the formula ratio: Weigh and proportion the material components as shown in Table 1 above. Then, pour the weighed powder into a 100L V-type mixer, set the speed to 30rpm, and dry mix under nitrogen protection for 2 hours. Use a Hall effect flow meter to check whether the powder flowability is greater than or equal to 25s / 50g. Randomly sample for XRF composition analysis to ensure that the components are evenly distributed and the error of each component is within ±1% before spraying.

[0049] S12. After premixing is completed, spraying is performed. The boiler tube substrate of the heating surface of the gasifier is sandblasted to make its surface roughness Ra greater than 5μm, and is cleaned with acetone to remove oil stains and impurities. Kerosene is controlled to be 0.3L / min and oxygen is controlled to be 800L / min as fuel. The flame speed is greater than 2000m / s and the spraying distance is 200mm to quickly deposit the silicon carbide hard material. After spraying, the substrate is immediately air-cooled to prevent thermal deformation. The coating porosity is checked by metallographic microscope to see whether it is less than 5% and whether the bonding strength is greater than 50MPa.

[0050] S13. After spraying, post-processing is performed. The sprayed coating is placed in a box-type resistance furnace and heated to 600°C at a rate of 5°C / min. The temperature is kept at this temperature for 1 hour to activate the bonding between aluminum phosphate and calcium aluminate and eliminate residual stress. The coating is cooled to 200°C in the furnace and then air-cooled to avoid embrittlement of the coating. Finally, it is lightly polished with a diamond grinding wheel to a surface roughness Ra of less than 1μm. The coating area is laser remelted to increase the infrared emissivity and enhance the heat dissipation performance.

[0051] Example 2: As shown in Table 1 above, aluminum oxide ( ) is changed to 50 parts by mass, and the other material components and their mass parts, and the steps included in the preparation method of the protective coating are consistent with those in Example 1.

[0052] Example 3: As shown in Table 1 above, zirconium oxide ( ) is changed to 20 parts by mass, and the other material components and their mass parts, and the steps included in the preparation method of the protective coating are consistent with those in Example 1.

[0053] Example 4: As shown in Table 1 above, aluminum phosphate ( ) is changed to 10 parts by mass, and the other material components and their mass parts, and the steps included in the preparation method of the protective coating are consistent with those in Example 1.

[0054] In order to verify the rationality of the component intervals in the embodiments of the present invention and compare the effects of excessive or insufficient addition of protective coating material components on the protective coating, the following comparative examples 1 to 4 are set.

[0055] Comparative Example 1: As shown in Table 2 below, aluminum oxide ( ) is set to 55 parts by mass, and the other material components and their mass parts, and the steps included in the preparation method of the protective coating are consistent with those in Example 1.

[0056] Comparative Example 2: As shown in Table 2 below, zirconium oxide ( ) is set to 25 parts by mass, and the other material components and their mass parts, and the steps included in the preparation method of the protective coating are consistent with those in Example 1.

[0057] Comparative Example 3: As shown in Table 2 below, aluminum phosphate ( ) is set to 12 parts by mass, and the other material components and their mass parts, and the steps included in the preparation method of the protective coating are consistent with those in Example 1.

[0058] Comparative Example 4: As shown in Table 2 below, titanium oxide ( ) is set to 8 parts by mass, and the other material components and their mass parts, and the steps included in the preparation method of the protective coating are consistent with those in Example 1.

[0059] Table 2 Material components and weight percentages of the protective coatings in Comparative Examples 1 to 4

[0060]

[0061] The protective coatings prepared from the components of Examples 1 to 4 and Comparative Examples 1 to 4 were tested for porosity, bonding strength and coking rate, and the steps included (1) to (3).

[0062] (1) Porosity detection steps:

[0063] a. Sampling: Cut the coating specimen (10×10 mm), embed it with resin and polish it to a mirror finish;

[0064] b. Microscopic observation: Use a metallographic microscope (200× magnification) to photograph the coating cross section and randomly select five fields of view;

[0065] c. Image analysis: Calculate the pore area ratio using ImageJ software and take the average value.

[0066] Testing standard: Porosity = total pore area / total field area × 100%.

[0067] (2) Binding strength detection steps:

[0068] a. Sample preparation: Spray the coating onto a standard cylindrical substrate (Φ25mm) with a thickness of 200μm-300μm;

[0069] b. Adhesion test: Use epoxy resin to bond the coating sample to the substrate (ASTM C633 standard);

[0070] c. Tensile test: Use a universal material testing machine to stretch at a rate of 1 mm / min until the coating falls off. Record the maximum load: Bond strength = maximum load (N) / bonding area (mm²).

[0071] (3) Coking rate detection steps:

[0072] a. Simulated combustion: Burn Zhundong high-sodium coal (ash melting point 1200°C) in a one-dimensional flame furnace for 24 hours;

[0073] b. Coke layer measurement: After cooling, peel off the coke blocks and weigh the coke layer mass (coke layer mass / initial fly ash mass × 100%).

[0074] c. Surface analysis: SEM was used to observe the interface between the focal layer and the coating and evaluate the adhesion strength.

[0075] The performance data of each group in Examples 1 to 4 are shown in Table 3 below.

[0076] Table 3 Performance data of each group in Examples 1 to 4

[0077]

[0078] The performance data of each group in Comparative Examples 1 to 4 are shown in Table 4 below.

[0079] Table 4 Performance data of each group in Comparative Examples 1 to 4

[0080]

[0081] It can be seen from Table 3 and Table 4 that in the protective coatings of Examples 1 to 4, aluminum oxide ( ) (40-50 parts) and zirconium oxide ( ) (15-20 parts) synergistically construct a dense ceramic layer with stable porosity (less than 5%), strong high temperature resistance, yttrium oxide ( ) (3-5 parts) stabilized zirconium oxide ( ) lattice, titanium oxide ( ) (5-7 parts) Radiative heat dissipation suppresses local overheating, has high thermal stability, controllable main material costs, and the process is suitable for on-site construction, without the need for high-temperature sintering.

[0082] In Comparative Example 1, aluminum oxide ( ) is set to 55 parts by mass, resulting in poor fluidity, resulting in a porosity of 6.8% and a coking rate of 12%. In Comparative Example 2, zirconium oxide ( ) is set to 25 parts by mass, resulting in lattice instability, a bonding strength of 42 MPa, and a coking rate of 18%. In Comparative Example 3, aluminum phosphate ( ) is set to 12 parts by mass. Excessive binder leads to brittleness and the bonding strength is 38 Mpa. In comparative example 4, excessive addition of titanium oxide ( ), resulting in increased brittleness of the coating and a coking rate of 15%.

[0083] In Example 1, 45 parts of , 18 servings , achieving the comprehensive performance of low porosity, high bonding strength and low coking rate, and is suitable for long-term protection of the heating surface of high-alkali coal boilers. Therefore, Example 1 is the best embodiment.

[0084] To verify the synergistic effect of titanium oxide and aluminum oxide in the best embodiment, Example 1, a synergistic group 2, as well as control groups 2a and 2b, were designed. The weight percentages of titanium oxide and aluminum oxide in synergistic group 2 were the same as those in Example 1. Control group 2a lacked aluminum oxide, but the weight percentages of titanium oxide were the same as those in Example 1. Control group 2b lacked titanium oxide, but the weight percentages of aluminum oxide were the same as those in Example 1.

[0085] For collaborative group 2 and control groups 2a and 2b, coatings were prepared according to the process in the embodiment and performance tests were performed. The test data are shown in Table 5 below.

[0086] Table 5 - Performance test data

[0087]

[0088] As can be seen from Table 5 above, the radiation rate of collaborative group 2 (0.92) is close to Single group (0.88), but the tube wall temperature of collaborative group 2 (680℃) was significantly lower than Single group (750℃), indicating High temperature resistance ensures The stability of the radiation layer. The coking rate of synergistic group 2 (8%) is lower than that of the single component (12%-18%), demonstrating the synergistic cooling effect. In summary, Example 1 is the best example.

[0089] In summary, the alumina and zirconia of the present invention form a dense ceramic layer that isolates molten ash from contact with the tube wall. Titanium dioxide acts as a blackbody material to improve thermal radiation efficiency and reduce the temperature of the heated surface. Chromium oxide resists corrosion from sodium and potassium in high-alkali coal. Cerium dioxide inhibits oxidation reactions. Yttrium oxide stabilizes the zirconia lattice. Silicon carbide and aluminum oxide provide ultra-high thermal conductivity, preventing local overheating that can lead to coating failure. Magnesium oxide is added to adjust the thermal expansion coefficient and prevent thermal stress cracking. Furthermore, the cost of the main materials, alumina and zirconia, is manageable.

[0090] Another embodiment of the present invention relates to a gasifier heating surface, which includes the protective coating for an IGCC unit gasifier as described in the above embodiment; or, the gasifier heating surface includes the protective coating prepared according to the method for preparing the protective coating for an IGCC unit gasifier as described in the above embodiment.

[0091] Another embodiment of the present invention relates to a gasifier, which includes the gasifier heating surface described in the above embodiment.

[0092] Those skilled in the art will appreciate that the above embodiments are specific embodiments for implementing the present invention, and that in actual applications, various changes may be made in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A method for preparing a protective coating for an IGCC unit gasifier, characterized in that: The preparation method of the protective coating comprises: S1. Weigh according to the formula ratio: aluminum oxide: 40-50 parts, zirconium oxide: 15-20 parts, silicon carbide: 8-12 parts, chromium oxide: 4-6 parts, yttrium oxide: 3-5 parts, aluminum phosphate: 6-10 parts, titanium oxide: 5-7 parts, cerium oxide: 2-3 parts, magnesium oxide: 2-4 parts, calcium aluminate: 3-5 parts; Pour the weighed powder into the mixer, dry mix at a set speed under nitrogen protection for a preset time, and randomly sample for XRF composition analysis to ensure uniform distribution of each component. If the error of each component meets the preset error requirement, execute S2 for spraying; S2. After premixing is completed, spraying is performed on the heating surface of the gasifier boiler tube substrate to sandblast its surface roughness to meet the preset roughness requirements and clean it with acetone to remove oil and impurities. Kerosene 0.3L / min and oxygen 800L / min are controlled as fuel, the flame speed is greater than 2000m / s, and the spraying distance is 200mm-300mm to quickly deposit the silicon carbide hard material. After spraying, the substrate is immediately air-cooled to prevent thermal deformation. The coating porosity is less than 5% and the bonding strength is greater than 50MPa using a metallographic microscope; S3. After spraying, post-processing is performed. The sprayed coating is placed in a box-type resistance furnace and heated to 600°C at a rate of 5°C / min. The temperature is maintained for 1 hour to activate the bonding between aluminum phosphate and calcium aluminate and eliminate residual stress. The coating is cooled to 200°C in the furnace and then air-cooled to prevent embrittlement of the coating. Finally, it is lightly polished with a diamond grinding wheel to a surface roughness Ra of less than 1μm. The coating area is laser remelted to increase the infrared emissivity and enhance the heat dissipation performance.

2. The method for preparing a protective coating for an IGCC unit gasifier according to claim 1, characterized in that: After S3, it also includes: S4. Perform a final quality test on the protective coating, wherein the final quality test includes a porosity test, a bonding strength test, and a coking rate test.

3. A protective coating for an IGCC unit gasifier, characterized in that: The protective coating is prepared by the method for preparing the protective coating for the gasifier of an IGCC unit according to claim 1 or 2.

4. A gasifier heating surface, characterized in that: The heating surface of the gasifier includes the protective coating for an IGCC unit gasifier according to claim 3; or, the heating surface of the gasifier includes the protective coating prepared by the preparation method of the protective coating for an IGCC unit gasifier according to claim 1 or 2.

5. A gasifier, characterized in that: The gasifier comprises the gasifier heating surface according to claim 4.

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