Method for evaluating anti-coking performance of coating

Abstract

The application provides a coating anti-coking performance evaluation method, and belongs to the technical field of coking prevention and treatment of the heating surface of a thermal power unit boiler. The coating anti-coking performance evaluation method is based on the coking mechanism of the heating surface in the operation process of a coal-fired boiler. The coking medium is prepared and coated on the surface of the coating sample. The atmosphere temperature of the coating in different actual service environments is flexibly simulated by means of the heat treatment furnace. The coking condition of the coating in the actual service environment is accurately simulated. Then, the quantitative evaluation of the anti-coking performance of the coating is realized by comparing the changes of the mass and the reflection characteristic parameters of the coating sample before and after the test. The evaluation method can be completed under laboratory conditions, and is good in economy, convenient in operation and reliable in result.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coking prevention and treatment of the heating surface of a thermal power unit boiler, and particularly relates to a method for evaluating the coking resistance of a coating. BACKGROUND

[0002] In order to improve the economy of a coal-fired thermal power unit, some thermal power units burn Xinjiang high-alkali coal, represented by Zhundong coal. The burning of high-alkali coal causes serious coking problems of the heating surface of the boiler, such as the superheater and reheater, which seriously affect the safe, stable and economic operation of the unit. Conventional coking prevention measures include controlling the quality of the coal and adjusting the operating parameters of the boiler. In addition, the preparation of a coking-resistant coating on the surface of the heating surface of the boiler is also an effective measure to achieve coking control.

[0003] However, there is no uniform method for evaluating the coking resistance of the coating in the development process of the coking-resistant coating. At present, the coking resistance of the coating is generally evaluated by means of a one-dimensional flame test furnace under the premise of improving the probe. For example, patent application document CN 106289137 A discloses a method for measuring the coking resistance of a boiler heating surface tube coating, which comprises the following steps: 5) coking and slagging test in the test platform: a test boiler platform is used, the test conditions are as follows: the coal used for combustion is high-sodium coal, the operating condition is the actual operating condition, the operation is performed for 70-100 hours, and coking and slagging are not allowed on the surface of the coating.

[0004] The coking and slagging test in the test platform uses a test boiler platform, which is a one-dimensional flame test furnace, equivalent to a small-sized coal-fired thermal power boiler, and the test is performed under the actual operating condition for 70-100 hours. It can be seen that the coking and slagging test in the test platform has the following problems: (1) the test boiler platform itself is expensive; (2) the test needs to be performed once for each test, which leads to high test cost; (3) the operation of the test boiler platform is complex; and (4) the temperature of the atmosphere in the test boiler platform is difficult to adjust, and the temperature of the atmosphere in the test boiler platform cannot simulate the temperature of the atmosphere in different actual service environments of the coating.

[0005] It can be seen that the research on the method for evaluating the coking resistance of the coating in the related art is not sufficient enough, and it is necessary to further research and develop an economical, convenient and reliable method for evaluating the coking resistance of the coating under experimental conditions. SUMMARY

[0006] The present application is based on the discovery and understanding of the inventors of the following facts and problems: in the related art, the coking resistance of the coating is evaluated by means of a one-dimensional flame test furnace, which has high test cost, complex operation, high cost of the test furnace and difficult adjustment of the temperature of the atmosphere in the test furnace, and is not suitable for being performed under experimental conditions, and therefore, it is necessary to further improve and develop an economical, convenient and reliable method for evaluating the coking resistance of the coating under experimental conditions.

[0007] The present application aims to solve at least one of the technical problems in the related art. To this end, an embodiment of the present application proposes a coating anti-coking performance evaluation method, which can be performed under experimental conditions, is economical, convenient to operate, and reliable in results.

[0008] An embodiment of the present application provides a coating anti-coking performance evaluation method, comprising the following steps:

[0009] Step S1: measuring the initial mass and reflection characteristic parameters of the coating sample; at the same time, preparing a coking medium, which comprises Na2O2, Na2SO4, K2SO4, SiO2, Fe2O3, Al2O3 and CaO;

[0010] Step S2: coating the coking medium on the coating sample;

[0011] Step S3: placing the coating sample in a heat treatment furnace and placing it at a simulated temperature for 24-48 hours, wherein the simulated temperature is the atmosphere temperature in the actual service environment of the coating;

[0012] Step S4: taking the coating sample out of the heat treatment furnace, and after the coating sample cools down, removing the coking medium that is not firmly adhered to the surface of the coating sample;

[0013] Step S5: repeating steps S2-S4 at least twice, then observing the final surface coking condition of the coating sample, and measuring the final mass and reflection characteristic parameters of the coating sample;

[0014] Step S6: comparing the final mass and reflection characteristic parameters of the coating sample with the initial mass and reflection characteristic parameters, and quantitatively evaluating the anti-coking performance of the coating.

[0015] The coating anti-coking performance evaluation method of the embodiment of the present application has the following advantages and technical effects:

[0016] (1) The evaluation method of the embodiment of the present application is based on the coking mechanism of the heating surface in the operation process of a coal-fired boiler, the coking medium is prepared and coated on the surface of the coating sample, and the atmosphere temperature in the actual service environment of the coating is simulated by means of the heat treatment furnace, so that the coking condition of the coating in the actual service environment is relatively accurately simulated;

[0017] (2) The evaluation method of the embodiment of the present application uses the heat treatment furnace to complete the test, the temperature adjustment of the heat treatment furnace is relatively convenient, the atmosphere temperature in different service environments can be flexibly simulated, and the evaluation of the anti-coking performance of the coating in different service environments can be conveniently realized;

[0018] (3) The evaluation method of the embodiment of the present application introduces the two evaluation indexes of the quality and the reflection characteristic parameter of the coating sample, and the anti-coking performance of the coating can be quantitatively evaluated by comparing the changes of the two evaluation indexes of the quality and the reflection characteristic parameter of the coating sample before and after the comparison test, which is more accurate than the qualitative evaluation by macroscopic observation with naked eyes;

[0019] (4) The evaluation method of the embodiment of the present application is cyclically processed for 3-5 times in steps S2-S4, so that the total coating amount and the total heat treatment time of the coking medium are sufficient, and the accuracy of the evaluation result can be ensured.

[0020] (5) The total heat treatment time of the evaluation method of the embodiment of the present application is 72-240 hours, so that the evaluation method can be completed in a relatively short time and has high efficiency.

[0021] (6) The evaluation method of the embodiment of the present application can be completed under laboratory conditions, has low cost, and the test equipment used is relatively inexpensive;

[0022] (7) The evaluation method of the embodiment of the present application is convenient to operate.

[0023] (8) The evaluation method of the embodiment of the present application can economically, conveniently and reliably realize quantitative evaluation of the anti-coking performance of the coating under laboratory conditions, effectively accelerates the development process of the anti-coking coating, is conducive to solving the coking problem of the heating surface of the coal-fired boiler unit, and has important theoretical and economic value.

[0024] In some embodiments, in step S1, the mass ratio of Na2O2, Na2SO4, K2SO4, SiO2, Fe2O3, Al2O3 and CaO is (5-10):(15-20):1:(10-20):(5-10):(5-10):(5-10).

[0025] In some embodiments, in steps S1 and S5, the reflection characteristic parameter is the reflection coefficient and / or the reflectivity.

[0026] In some embodiments, in step S2, the coating amount of the coking medium is 3-10 mg / cm 2 .

[0027] In some embodiments, in step S3, the heat treatment furnace is a muffle furnace or an atmosphere furnace.

[0028] In some embodiments, the heat treatment furnace is an atmosphere furnace, and a reducing atmosphere is provided in the atmosphere furnace.

[0029] In some embodiments, in step S3, the simulation temperature is 450-1200℃.

[0030] In some embodiments, the simulated temperature is 600-1200℃.

[0031] In some embodiments, step S6 specifically comprises: calculating the change rate y1 of the final mass of the coating sample relative to the initial mass, calculating the change rate y2 of the final reflection characteristic parameter of the coating sample relative to the initial reflection characteristic parameter, if the maximum of y1 and y2 is less than or equal to 1.5%, the anti-coking performance of the coating is determined to be level 1; if the maximum of y1 and y2 is greater than 1.5% and less than or equal to 2%, the anti-coking performance of the coating is determined to be level 2; if the maximum of y1 and y2 is greater than 2%, the anti-coking performance of the coating is determined to be level 3.

[0032] In some embodiments, after removing the coking medium not firmly adhered to the surface of the coating sample in step S4, the method further comprises: observing the surface coking of the coating sample at the intermediate stage, and measuring the mass and reflection characteristic parameter of the coating sample at the intermediate stage.

[0033] In some embodiments, in step S6, the method further comprises: comparing the mass and reflection characteristic parameter of the coating sample at the intermediate stage with the initial mass and reflection characteristic parameter, and dynamically evaluating the development and change of the surface coking of the coating. DETAILED DESCRIPTION

[0034] The embodiments of the present application are described in detail below, which are exemplary and intended to explain the present application, and cannot be understood as a limitation of the present application.

[0035] The embodiments of the present application provide a coating anti-coking performance evaluation method, which comprises the following steps:

[0036] Step S1: measuring the initial mass and reflection characteristic parameter of the coating sample; meanwhile, preparing a coking medium, which comprises Na2O2, Na2SO4, K2SO4, SiO2, Fe2O3, Al2O3 and CaO;

[0037] Step S2: coating the coking medium on the coating sample;

[0038] Step S3: placing the coating sample in a heat treatment furnace, and keeping the temperature constant at a simulated temperature for 24-48h, wherein the simulated temperature is the atmosphere temperature in the actual service environment of the coating;

[0039] Step S4: taking the coating sample out of the heat treatment furnace, and removing the coking medium not firmly adhered to the surface of the coating sample after the coating sample is cooled;

[0040] Step S5: repeating steps S2-S4 for 2-4 times, then observing the final surface coking condition of the coating sample, and measuring the final mass and reflection characteristic parameters of the coating sample;

[0041] Step S6: comparing the final mass and reflection characteristic parameters of the coating sample with the initial mass and reflection characteristic parameters, and quantitatively evaluating the anti-coking performance of the coating.

[0042] Working principle: the evaluation method of the embodiment of the present application is based on the coking mechanism of the heating surface in the operation process of the coal-fired boiler, and the composition of the coking medium is designed by fully considering the composition of the coking substance and the coking formation mechanism. The coking medium is coated and placed in a heat treatment furnace for a certain period of time to simulate the formation of coking in the actual service process of the coating. The composition of the finally formed coking substance is basically consistent with the composition of the coking substance formed in the actual service environment of the coating. In addition, the evaluation method of the embodiment of the present application flexibly simulates the atmosphere temperature of the coating in different actual service environments by means of the heat treatment furnace, and further simulates the coking condition of the coating in the actual service environment. Furthermore, the evaluation method of the embodiment of the present application realizes quantitative evaluation of the anti-coking performance of the coating by comparing the changes of the mass and reflection characteristic parameters of the coating sample before and after the test. The above processes are all completed under laboratory conditions, which is economical, convenient to operate, and reliable in results.

[0043] The evaluation method of the embodiment of the present application is divided into 3-5 times of cyclic processing of steps S2-S4, because of the following two reasons: on the one hand, by repeating steps S2-S4, the changes of the mass and reflection characteristic parameters of the coating sample in the intermediate state relative to the last cycle can be compared correspondingly, and the development and change of the surface coking of the coating sample can be dynamically evaluated, so that the evaluation result is more reliable; on the other hand, through multiple cycles, the coking thickness can be increased, and the macroscopic size of the coking product can be increased, which provides convenience for further evaluation or analysis of the composition, phase, structure, etc. of the coking product under this test method.

[0044] Specifically, in some embodiments, after removing the coking medium not firmly adhered to the surface of the coating sample in step S4, the following steps can be further included: observing the surface coking condition of the coating sample in the intermediate stage, and measuring the mass and reflection characteristic parameters of the coating sample in the intermediate stage. Correspondingly, in step S6, the following steps can be further included: comparing the mass and reflection characteristic parameters of the coating sample in the intermediate stage with the initial mass and reflection characteristic parameters, and dynamically evaluating the development and change of the surface coking of the coating.

[0045] Since the object to be evaluated in the embodiment of the present application is a coating, the coating cannot exist alone and needs to be formed with the help of a certain substrate, and therefore the coating sample in the embodiment of the present application comprises a substrate and a coating covering the surface of the substrate. The embodiment of the present application does not have special requirements for the shape of the substrate. For example, the shape of the substrate comprises a tubular shape, a sheet shape, a strip shape, a rod shape, a spherical shape, and the like. In addition, the embodiment of the present application does not have special limitations for the material of the substrate, as long as it can withstand the high temperature set by the simulation temperature, for example, it can be a ceramic substrate or a metal substrate, and the like.

[0046] In some embodiments, the substrate is a ceramic substrate. The heating surface tubes in the superheater, reheater or economizer of a coal-fired boiler are all metal tubes, and the anti-coking coating is made on the surface of these metal tubes. However, due to the existence of the cooling device such as the water wall, the wall temperature of the heating surface tubes in the superheater and reheater of the boiler will not exceed the heat-resistant range of the metal tubes. The evaluation method of the embodiment of the present application uses the heat treatment furnace, and in order to simulate the formation of coking, the heat treatment temperature is the atmosphere temperature of the actual service environment of the coating, which can be higher than the heat-resistant range of the metal substrate. Therefore, considering the heat resistance of the substrate, the substrate of the coating sample selected in the evaluation method of the embodiment of the present application is preferably a ceramic substrate. In addition, it should be noted that although the ceramic substrate is selected for the coating sample, which is different from the metal substrate in the actual service environment of the coating, this does not affect the accuracy of the evaluation of the anti-coking performance of the coating itself.

[0047] Regarding the coking medium, the phase, composition and coking formation mechanism of the coking product should be fully considered in the design process to ensure that the composition of the coking product obtained after heat treatment of the coking medium is basically consistent with the composition of the coking product in the actual service environment of the coating. At present, it is generally believed that Na, K alkali metal oxides, alkali metal peroxides and alkali metal sulfates play an especially important role in the formation of coking in the process of coal combustion. Alkali metal oxides, alkali metal peroxides and alkali metal sulfates form low-melting-point complex aluminates with Fe2O3, Al2O3 and other metal oxides at high temperatures, which promotes the formation and development of coking. Therefore, by preparing alkali metal oxides, alkali metal peroxides, alkali metal sulfates and Fe2O3, Al2O3 and other metal oxides in the coking medium, the formation of coking can be better simulated.

[0048] Exemplarily, if the coating is used in the actual service environment of Xinjiang Zhundong high-alkali coal, the coking medium can include Na2O2, Na2SO4, K2SO4, SiO2, Fe2O3, Al2O3 and CaO, and the mass ratio of Na2O2, Na2SO4, K2SO4, SiO2, Fe2O3, Al2O3 and CaO is (5-10):(15-20):1:(10-20):(5-10):(5-10):(5-10). If the coating is used in the actual service environment of Baishihu coal, the coking medium can include Na2O, K2O, SiO2, Fe2O3, Al2O3, CaO and MgO, and the mass ratio of Na2O, K2O, SiO2, Fe2O3, Al2O3, CaO and MgO is (2-3):(0.2-0.3):(18-20):(14-16):(7-9):(36-40):(1.5-2). If the coating is used in the actual service environment of other coal, the composition of the coking medium can be designed according to the characteristics of the corresponding coal.

[0049] As to the coating amount of the coking medium, the embodiments of the present application are not particularly limited, as long as the coating surface is covered with the coking medium during the test time in step S3. In some embodiments, the coating amount of the coking medium in step S2 is 3-10 mg / cm2. 2 If the coking medium is too little, the coking at the later stage of the test time in step S3 will be affected due to the lack of the coking medium, which is not conducive to accurately simulating the coking condition in the actual service environment of the coating, and thus the accurate evaluation of the anti-coking performance of the coating cannot be obtained. If the coking medium is too much, the coking condition on the coating surface under the test condition is more serious than that in the actual service environment of the coating, which will lead to the deviation of the evaluation result and is not conducive to objectively evaluating the anti-coking performance of the coating.

[0050] The specific type of the heat treatment furnace used in the embodiments of the present application is also not particularly limited, as long as it has the function of high-temperature heating and can flexibly adjust the temperature. For example, a conventional muffle furnace can be used, or an atmosphere furnace can be selected. Some actual coal-fired boilers have a reducing atmosphere (H2 or CO), such as a gasification furnace. Therefore, in order to better simulate the coking condition in the gasification furnace, preferably, in some embodiments, an atmosphere furnace is used and the atmosphere furnace is set to a reducing atmosphere (H2 or CO). By setting the reducing atmosphere (H2 or CO), the actual atmosphere environment in the furnace, such as the gasification furnace, can be simulated, and the formation and development of coking can be promoted.

[0051] Although the current academic research does not fully reveal the complete mechanism of the formation and development of the coking, the related technology generally considers that the slag is first formed on the surface of the coating during the coking, and then the high-temperature fly ash is captured, and the surface temperature increases with the increase of the thickness of the ash. Specifically, in the actual coal-fired boiler, the furnace temperature can reach more than 1000℃. Due to the presence of water-cooled walls and other heat exchange devices, the temperature of the tube wall of the superheater, reheater and other heating surfaces is relatively low, generally not more than 600℃. But the superheater and reheater are arranged in the flue whose smoke temperature is higher than 800℃, and the fuel ash contains fusible alkali metal oxides, which sublimate or form fusible eutectic at high temperature, and condense to form an inner ash layer when meeting the relatively cold tube wall of the heating surface, and the surface temperature of the outer layer of the ash increases with the increase of the thickness of the ash, so that the ash layer reaches the melting state, covers the tube wall and has viscosity, further captures the fly ash to generate high-temperature fly ash and continuously thickens, and the temperature of the outer layer of the ash can reach 1000℃ or even higher.

[0052] Therefore, the simulation temperature in step S3 of the embodiment of the present application can be set with reference to the atmosphere temperature in the actual service environment of the coating, and can be generally set to 450-1200℃. When the simulation temperature is too low, the melting point of the low-melting ash and medium-melting ash in the high-temperature fly ash cannot be reached, and the coking severity under the test conditions of step S3 is lower than that in the actual service environment of the coating, which can lead to insufficient simulation of the coking process in step S3, and further lead to the evaluation result being biased. In order to improve the accuracy of the evaluation result, preferably, in some embodiments, the simulation temperature is set to 600-1200℃.

[0053] The evaluation method of the embodiment of the present application introduces two evaluation indexes of the mass and the reflection characteristic parameter of the coating sample, and quantitatively evaluates the anti-coking performance of the coating sample by comparing the changes of the mass and the reflection characteristic parameter of the coating sample before and after the test. Specifically, the reflection characteristic parameter includes the reflection coefficient and / or the reflectivity.

[0054] The anti-coking performance of the coating is evaluated by testing the changes of the mass and the reflection characteristic parameter of the coating before and after the test. Specifically, after the coating surface is coked, the mass of the coating increases, and the greater the change of the mass, the more serious the coking of the coating surface, and the worse the anti-coking performance of the coating. At the same time, after the coating surface is coked, the reflection characteristic parameter of the coating decreases, and the greater the change of the reflection characteristic parameter before and after the test, the more serious the coking of the coating surface, and the worse the anti-coking performance of the coating.

[0055] In some embodiments, step S6 is specifically: calculating the change rate y1 of the final mass of the coating sample relative to the initial mass, calculating the change rate y2 of the final reflection characteristic parameter of the coating sample relative to the initial reflection characteristic parameter, if the maximum of y1 and y2 is less than or equal to 1.5%, the anti-coking performance of the coating is determined to be level 1; if the maximum of y1 and y2 is greater than 1.5% and less than or equal to 2%, the anti-coking performance of the coating is determined to be level 2; if the maximum of y1 and y2 is greater than 2%, the anti-coking performance of the coating is determined to be level 3.

[0056] The application will be described in detail below with reference to the embodiments.

[0057] The coating sample used in the following embodiments is a ceramic substrate and an anti-coking coating with a thickness of 200 μm prepared on the surface of the ceramic substrate, and the anti-coking coating is prepared from a commercialized nano-ceramic coating material.

[0058] Embodiment 1

[0059] Step S100: measuring the initial mass m0 and the initial reflection coefficient Γ0 of the coating sample; preparing the coking medium, and the specific components are: Na2O2: Na2SO4: K2SO4: SiO2: Fe2O3: Al2O3: CaO with a mass ratio of 5:15:1:10:5:5:5;

[0060] Step S200: quantitatively coating 3 mg / cm 2 of the coking medium on the coating sample;

[0061] Step S300: placing the coating sample coated with the coking medium in step S200 in a common muffle furnace, and placing it at 600℃ for 48 h;

[0062] Step S400: taking out the coating sample treated in step S300 from the muffle furnace, and after the coating sample is cooled, removing the coking medium not firmly adhered on the surface of the coating sample, observing the surface coking of the coating sample after the first heat treatment, and measuring the mass m1 and the reflection coefficient Γ1 of the coating sample after the first heat treatment;

[0063] Step S500: coating 3 mg / cm 2 of the coking medium again on the coating sample from which the coking medium not firmly adhered on the surface is removed in step S400;

[0064] Step S600: placing the coating sample coated with the coking medium again in step S500 in the muffle furnace, and placing it at 600℃ for 48 h;

[0065] Step S700: The coating sample after the heat treatment in step S600 is taken out of the muffle furnace, and after the coating sample is cooled, the non-firmly adhered coking medium on the surface of the coating sample is removed, the surface coking condition of the coating sample after the second heat treatment is observed, and the mass m2 and the reflection coefficient Γ2 of the coating sample after the second heat treatment are measured;

[0066] Step S800: The coating sample on which the non-firmly adhered coking medium on the surface is removed in step S700 is coated with 3 mg / cm 2 of coking medium again;

[0067] Step S900: The coating sample on which the coking medium is coated again in step S800 is placed in the muffle furnace, and is kept at 600℃ for 48 h;

[0068] Step S1000: The coating sample after the heat treatment in step S900 is taken out of the muffle furnace, and after the coating sample is cooled, the non-firmly adhered coking medium on the surface of the coating sample is removed, the surface coking condition of the coating sample after the third heat treatment is observed, and the mass m3 and the reflection coefficient Γ3 of the coating sample after the third heat treatment are measured;

[0069] Step S1100: The final mass m3 and the initial mass m0 of the coating sample, and the final reflection coefficient Γ3 and the initial reflection coefficient Γ0 of the coating sample are compared, the change rate y1 of the final mass m3 of the coating sample relative to the initial mass m0 is calculated, and the change rate y2 of the final reflection coefficient Γ3 of the coating sample relative to the initial reflection coefficient Γ0 is calculated.

[0070] The anti-coking performance of the coating is evaluated according to the following evaluation criteria:

[0071] If the maximum of y1 and y2 is less than or equal to 1.5%, it is determined that the anti-coking performance of the coating is level 1; if the maximum of y1 and y2 is greater than 1.5% and less than or equal to 2%, it is determined that the anti-coking performance of the coating is level 2; if the maximum of y1 and y2 is greater than 2%, it is determined that the anti-coking performance of the coating is level 3.

[0072] Comparative Example 1

[0073] The metal substrate without the prepared anti-coking coating is used instead of the coating sample in Example 1, and other steps are the same as those in Example 1.

[0074] Comparative Example 2

[0075] The reflection coefficient Γ 始 of the original metal pipe material before the test of the superheater of the coal-fired power plant is measured, and the reflection coefficient Γ 末 of the metal pipe material after the surface coking after the test of the superheater for 4 months is measured, and the change rate y2 of the reflection coefficient is calculated.

[0076] Table 1. Quality and reflectance change of Example 1 and Comparative Examples 1-2

[0077]

[0078] Comparative Example 2, the reflectance change rate of Comparative Example 2 is about 20%, which is basically the same as that of Comparative Example 1, proving that the evaluation method of the example can effectively simulate the coking condition of the surface of the superheater of the coal-fired boiler after running for 4 months. By comparing Example 1 and Comparative Example 1, the change rate of the reflectance of the coating surface of the coating sample in Example 1 before and after the test is less than 1%, and the change rate of the quality is less than 1.5%, while the change rate of the reflectance of the surface of the metal substrate without the anti-coking coating in Comparative Example 1 before and after the test is close to 20%, and the change rate of the quality is close to 15%, which fully shows that the anti-coking coating used in Example 1 has good anti-coking performance, and it can be expected that the anti-coking coating also has good anti-coking performance if it is used in actual working conditions. Therefore, by comparing Example 1 and Comparative Examples 1-2, it is shown that the evaluation method of Example 1 has high reliability.

[0079] In addition, although Table 1 only shows the change rates of the quality and the reflectance of the coating sample in the final state relative to the initial state, the applicant finds that the change rates of the quality and the reflectance of the coating sample in the intermediate stage are large at the beginning, and then tend to be stable by comparing the change rates in the cycle of coating-heat treatment-measuring change rate multiple times.

[0080] Example 2

[0081] The specific components of the coking medium are: the mass ratio of Na2O2: Na2SO4: K2SO4: SiO2: Fe2O3: Al2O3: CaO is 10: 15: 1: 20: 5: 10: 5; the amount of the coking medium is 10 mg / cm 2 ; the temperature of the atmosphere furnace is set to 1000℃, the constant temperature time is 24h; the reflectance R is used instead of the reflectance Γ, the change rate of the reflectance R is y2; and the other steps are the same as those in Example 1.

[0082] Table 2. Quality and reflectance change of Example 2

[0083]

[0084] Although Table 2 only shows the change rates of the quality and the reflectance of the coating sample in the final state relative to the initial state, the applicant finds that the change rates of the quality and the reflectance of the coating sample in the intermediate stage are large at the beginning, and then tend to be stable by comparing the change rates in the cycle of coating-heat treatment-measuring change rate multiple times.

[0085] Example 3

[0086] Step S100: measure the initial mass m0 and initial reflection coefficient Γ0 of the coating sample; prepare the coking medium, and the specific components are: Na2O2: Na2SO4: K2SO4: SiO2: Fe2O3: Al2O3: CaO with a mass ratio of 10:20:1:15:10:10:10;

[0087] Step S200: quantitatively coat 5 mg / cm 2 of the coking medium on the coating sample;

[0088] Step S300: place the coating sample coated with the coking medium in step S200 in the atmosphere furnace, and keep it at 700°C for 48h, while maintaining CO atmosphere in the atmosphere furnace;

[0089] Step S400: take out the coating sample after heat treatment in step S300 from the atmosphere furnace, and after the coating sample cools down, remove the coking medium that is not firmly adhered on the surface of the coating sample, observe the surface coking of the coating sample after the first heat treatment, and measure the mass m1 and reflection coefficient Γ1 of the coating sample after the first heat treatment;

[0090] Step S500: coat 5 mg / cm 2 of the coking medium again on the coating sample from which the coking medium that is not firmly adhered on the surface is removed in step S400;

[0091] Step S600: place the coating sample coated with the coking medium again in step S500 in the atmosphere furnace, and keep it at 700°C for 48h;

[0092] Step S700: take out the coating sample after heat treatment in step S600 from the atmosphere furnace, and after the coating sample cools down, remove the coking medium that is not firmly adhered on the surface of the coating sample, observe the surface coking of the coating sample after the second heat treatment, and measure the mass m2 and reflection coefficient Γ2 of the coating sample after the second heat treatment;

[0093] Step S800: coat 5 mg / cm 2 of the coking medium again on the coating sample from which the coking medium that is not firmly adhered on the surface is removed in step S700;

[0094] Step S900: place the coating sample coated with the coking medium again in step S800 in the atmosphere furnace, and keep it at 700°C for 48h;

[0095] Step S1000: The coating sample after the third heat treatment in step S900 is taken out of the atmosphere furnace, and after the coating sample is cooled, the non-firmly adhered coking medium on the surface of the coating sample is removed, the surface coking condition of the coating sample after the third heat treatment is observed, and the mass m3 and the reflection coefficient Γ3 of the coating sample after the third heat treatment are measured;

[0096] Step S1100: 5 mg / cm 2 of the coking medium is coated on the coating sample after the non-firmly adhered coking medium on the surface is removed in step S1000 again;

[0097] Step S1200: The coating sample to which the coking medium is coated again in step S1100 is placed in the atmosphere furnace, and is kept at 700°C for 48 h;

[0098] Step S1300: The coating sample after the fourth heat treatment in step S900 is taken out of the atmosphere furnace, and after the coating sample is cooled, the non-firmly adhered coking medium on the surface of the coating sample is removed, the surface coking condition of the coating sample after the fourth heat treatment is observed, and the mass m4 and the reflection coefficient Γ4 of the coating sample after the fourth heat treatment are measured;

[0099] Step S1400: 5 mg / cm 2 of the coking medium is coated on the coating sample after the non-firmly adhered coking medium on the surface is removed in step S1300 again;

[0100] Step S1500: The coating sample to which the coking medium is coated again in step S1400 is placed in the atmosphere furnace, and is kept at 700°C for 48 h;

[0101] Step S1600: The coating sample after the fifth heat treatment in step S1500 is taken out of the atmosphere furnace, and after the coating sample is cooled, the non-firmly adhered coking medium on the surface of the coating sample is removed, the surface coking condition of the coating sample after the fifth heat treatment is observed, and the mass m5 and the reflection coefficient Γ5 of the coating sample after the fifth heat treatment are measured;

[0102] Step S1700: The final mass m5 and the initial mass m0 of the coating sample, and the final reflection coefficient Γ5 and the initial reflection coefficient Γ0 of the coating sample are compared, the change rate y1 of the final mass m5 of the coating sample relative to the initial mass m0 is calculated, and the change rate y2 of the final reflection coefficient Γ5 of the coating sample relative to the initial reflection coefficient Γ0 is calculated.

[0103] The anti-coking performance of the coating is evaluated according to the following evaluation criteria:

[0104] If the maximum of y1 and y2 is less than or equal to 1.5%, the anti-coking performance of the coating is determined to be level 1; if the maximum of y1 and y2 is greater than 1.5% and less than or equal to 2%, the anti-coking performance of the coating is determined to be level 2; if the maximum of y1 and y2 is greater than 2%, the anti-coking performance of the coating is determined to be level 3.

[0105] Example 4

[0106] In this embodiment, the specific components of the coking medium are: Na2O2: Na2SO4: K2SO4: SiO2: Fe2O3: Al2O3: CaO, with a mass ratio of 5:20:1:15:10:8:5; the amount of the coking medium is 7 mg / cm 2 ; the temperature of the atmosphere furnace is set to 800°C, and the constant temperature time is 24 h; the other steps are the same as in Example 3.

[0107] Example 5

[0108] Step S100: measure the initial mass m0 and initial reflection coefficient Γ0 of the coating sample; prepare the coking medium, with specific components being: Na2O2: Na2SO4: K2SO4: SiO2: Fe2O3: Al2O3: CaO, with a mass ratio of 10:18:1:13:8:10:5;

[0109] Step S200: quantitatively coat 10 mg / cm 2 of the coking medium on the coating sample;

[0110] Step S300: place the coating sample coated with the coking medium in Step S200 in a common muffle furnace, and keep it at a constant temperature of 900°C for 24 h;

[0111] Step S400: take out the coating sample after heat treatment in Step S300 from the muffle furnace, and after the coating sample cools down, remove the coking medium that is not firmly adhered on the surface of the coating sample, observe the surface coking of the coating sample after the first heat treatment, and measure the mass m1 and reflection coefficient Γ1 of the coating sample after the first heat treatment;

[0112] Step S500: coat 10 mg / cm 2 of the coking medium again on the coating sample from which the coking medium that is not firmly adhered on the surface is removed in Step S400;

[0113] Step S600: place the coating sample coated with the coking medium again in Step S500 in a muffle furnace, and keep it at a constant temperature of 900°C for 24 h;

[0114] Step S700: The coating sample after heat treatment in step S600 is taken out of the muffle furnace, and after the coating sample is cooled, the non-firmly adhered coking medium on the surface of the coating sample is removed, the surface coking condition of the coating sample after the second heat treatment is observed, and the mass m2 and the reflection coefficient Γ2 of the coating sample after the second heat treatment are measured;

[0115] Step S800: The coating sample on which the non-firmly adhered coking medium on the surface is removed in step S700 is coated with 10 mg / cm 2 of coking medium again;

[0116] Step S900: The coating sample on which the coking medium is coated again in step S800 is placed in the muffle furnace, and is kept at 900°C for 24 h;

[0117] Step S1000: The coating sample after heat treatment in step S900 is taken out of the muffle furnace, and after the coating sample is cooled, the non-firmly adhered coking medium on the surface of the coating sample is removed, the surface coking condition of the coating sample after the third heat treatment is observed, and the mass m3 and the reflection coefficient Γ3 of the coating sample after the third heat treatment are measured;

[0118] Step S1100: The coating sample on which the non-firmly adhered coking medium on the surface is removed in step S1000 is coated with 10 mg / cm 2 of coking medium again;

[0119] Step S1200: The coating sample on which the coking medium is coated again in step S1100 is placed in the muffle furnace, and is kept at 900°C for 24 h;

[0120] Step S1300: The coating sample after heat treatment in step S900 is taken out of the muffle furnace, and after the coating sample is cooled, the non-firmly adhered coking medium on the surface of the coating sample is removed, the surface coking condition of the coating sample after the fourth heat treatment is observed, and the mass m4 and the reflection coefficient Γ4 of the coating sample after the fourth heat treatment are measured;

[0121] Step S1400: The final mass m4 and the initial mass m0 of the coating sample, and the final reflection coefficient Γ4 and the initial reflection coefficient Γ0 of the coating sample are compared, the change rate y1 of the final mass m4 of the coating sample relative to the initial mass m0 is calculated, and the change rate y2 of the final reflection coefficient Γ4 of the coating sample relative to the initial reflection coefficient Γ0 is calculated.

[0122] The anti-coking performance of the coating is evaluated according to the following evaluation criteria:

[0123] If the maximum of y1 and y2 is less than or equal to 1.5%, the anti-coking performance of the coating is determined to be level 1; if the maximum of y1 and y2 is greater than 1.5% and less than or equal to 2%, the anti-coking performance of the coating is determined to be level 2; if the maximum of y1 and y2 is greater than 2%, the anti-coking performance of the coating is determined to be level 3.

[0124] Table 3. Quality and change in reflection coefficient of Examples 3-5

[0125]

[0126] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present application. In the present specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific feature, structure, material or characteristic described can be combined in any appropriate manner in any one or more embodiments or examples. Furthermore, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples, without contradiction.

[0127] Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and are not to be construed as limiting the present application, and the person skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method for evaluating the anti-coking performance of a coating, characterized in that, The method comprises the following steps: Step S1: measuring the initial mass and reflection characteristic parameters of the coating sample, wherein the reflection characteristic parameters are reflection coefficient and / or reflectivity; meanwhile, preparing a coking medium, wherein the coking medium comprises Na2O2, Na2SO4, K2SO4, SiO2, Fe2O3, Al2O3 and CaO; Step S2: coating the coking medium on the coating sample; Step S3: placing the coating sample in a heat treatment furnace and keeping constant temperature for 24-48 hours at a simulated temperature, wherein the simulated temperature is the atmosphere temperature in the actual service environment of the coating; Step S4: taking out the coating sample from the heat treatment furnace, and removing the coking medium which is not firmly adhered to the surface of the coating sample after the coating sample is cooled; Step S5: repeating steps S2-S4 for 2-4 times, then observing the final surface coking condition of the coating sample, and measuring the final mass and reflection characteristic parameters of the coating sample, wherein the reflection characteristic parameters are reflection coefficient and / or reflectivity; Step S6: comparing the final mass and reflection characteristic parameters of the coating sample with the initial mass and reflection characteristic parameters, and quantitatively evaluating the anti-coking performance of the coating.

2. The method for evaluating the anti-coking performance of a coating according to claim 1, characterized in that, In step S1, the mass ratio of Na2O2, Na2SO4, K2SO4, SiO2, Fe2O3, Al2O3 and CaO is (5-10):(15-20):1:(10-20):(5-10):(5-10):(5-10).

3. The method for evaluating the anti-coking performance of a coating according to claim 1, characterized in that, In step S2, the coking medium is applied in an amount of 3-10 mg / cm 2 .

4. The method for evaluating the anti-coking performance of a coating according to claim 1, characterized by, In step S3, the heat treatment furnace is a muffle furnace or an atmosphere furnace.

5. The method for evaluating the anti-coking performance of a coating according to claim 4, characterized in that, The atmosphere furnace is provided with a reducing atmosphere.

6. The method for evaluating the anti-coking performance of a coating according to claim 1, characterized in that, In step S3, the simulated temperature is 450-1200°C.

7. The method for evaluating the anti-coking performance of a coating according to claim 6, characterized in that, The simulated temperature is 600-1200°C.

8. The method for evaluating the anti-coking performance of a coating according to claim 1, characterized by, In step S6, the change rate y1 of the final mass of the coating sample relative to the initial mass is calculated, the change rate y2 of the final reflection characteristic parameters of the coating sample relative to the initial reflection characteristic parameters is calculated, if the maximum of y1 and y2 is less than or equal to 1.5%, the anti-coking performance of the coating is determined as level 1; if the maximum of y1 and y2 is greater than 1.5% and less than or equal to 2%, the anti-coking performance of the coating is determined as level 2; if the maximum of y1 and y2 is greater than 2%, the anti-coking performance of the coating is determined as level 3.

9. The method for evaluating the anti-coking performance of a coating according to claim 1, characterized by, In step S4, after removing the coking medium which is not firmly adhered to the surface of the coating sample, the surface coking condition of the coating sample at the intermediate stage is observed, and the mass and reflection characteristic parameters of the coating sample at the intermediate stage are measured.

10. The method for evaluating the anti-coking performance of a coating according to claim 9, characterized in that, In step S6, the mass and reflection characteristic parameters of the coating sample at the intermediate stage are compared with the initial mass and reflection characteristic parameters, and the development and change of the surface coking of the coating are dynamically evaluated.

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