Application of inorganic salt particles in inhibiting corrosion of incinerators during solid waste incineration

Abstract

The present invention provides an application of inorganic salt particles in inhibiting the corrosion of an incinerator during solid waste incineration. The inorganic salt particles of the present invention can inhibit the corrosion of the incinerator by the products of solid waste incineration during the solid waste incineration process. The inorganic salt particles include at least one of kaolin, CaCO3, and TiO2. Before the solid waste is incinerated, the solid waste is first mixed with the inorganic salt particles to obtain a mixture, and then the mixture is placed in an incinerator for incineration. After the inorganic salt particles are mixed with the solid waste, the inorganic mineral composition or particle size distribution of the particles in the solid waste incineration process is changed, which will result in changes in the high-temperature corrosion characteristics of the particles on the heating surface materials inside the boiler, thereby inhibiting the high-temperature corrosion of the incinerator by the products of solid waste incineration.

Description

Technical Field

[0001] The present invention relates to the technical field of solid waste incineration, and in particular to the application of inorganic salt particles in inhibiting the corrosion of an incinerator during solid waste incineration. Background Art

[0002] The high-temperature corrosion problem of the metal materials on the heating surface of the heat exchange area is one of the main challenges faced by waste incineration boilers. As the main cause of failure of superheater pipes, high-temperature corrosion is closely related to the inorganic mineral components inside the municipal solid waste. High-temperature corrosion accelerates the oxidation of the heating surface material and metal loss, which greatly reduces the service life of the heat exchange tubes. At present, the removal of acidic gases and fine particulate matter in the flue gas of waste incineration mostly adopts the tail flue gas treatment method, which does not play a role in slowing down the high-temperature corrosion inside the furnace and superheater pipes. The high-temperature corrosion occurring on the surface of the boiler heating surface material is a complex process, which is caused by HCl, SO x It is the result of the combined action of gases such as Cl2, O2 and H2S or substances such as alkali metal chlorides (NaCl, KCl) and alkali metal sulfates (NaSO4, K2SO4) on the surface of metal or alloy materials. Generally, in the early stages of solid fuel boiler operation, before the ash and slag layer is formed on the surface of the heating surface material inside the boiler, the corrosion behavior is mainly gas phase corrosion. After the boiler has been running for a period of time, the ash and slag layer on the surface of the heating surface gradually stabilizes, and solid phase corrosion becomes an important reason for the continued corrosion process. Existing studies have shown that when high-temperature superheater pipe materials are exposed to chloride salt deposits, the corrosion phenomenon is more serious than when exposed to HCl gas without deposits. Even if the HCl gas concentration reaches 1000ppm, the former is more corrosive. Literature research also shows that the HCl gas concentration in waste incinerators is usually between 770-1300ppm. Slagging and corrosion often occur simultaneously in waste incinerators. Ash particles in the slagging layer come into close contact with superheater piping materials. At high local temperatures, the alkali chloride or sulfate mixture in this slagging layer can even exist in a molten state. During long-term operation of a waste incineration boiler, the corrosiveness of the alkali chloride slagging layer, which forms after local condensation on the high-temperature heating surface material, can be even more damaging than the corrosive effects of the HCl gas within the furnace.

[0003] Due to the high temperature corrosion of the furnace interior and superheater pipes in the process of solid waste incineration boilers, it is necessary to provide an inhibitor to slow down the high temperature corrosion. Summary of the Invention

[0004] In view of this, the present invention proposes an application of inorganic salt particles in inhibiting the corrosion of an incinerator during solid waste incineration, so as to solve the defects of the prior art.

[0005] In a first aspect, the present invention provides an application of inorganic salt particles as high-temperature inhibitors during solid waste incineration to inhibit the corrosion of the incinerator by the products of solid waste incineration, wherein the inorganic salt particles include at least one of kaolin, CaCO3, and TiO2.

[0006] Preferably, in the above application, the added amount of the inorganic salt particles is 3-7% of the mass of the solid waste.

[0007] In a second aspect, the present invention further provides a method for simulating and inhibiting the corrosion of an incinerator by products during the incineration of solid waste, comprising the following steps:

[0008] Cover the stainless steel surface with ash particles, then heat the stainless steel in a muffle furnace at 500-1200°C and test its corrosion condition;

[0009] The ash particles are products obtained by mixing solid waste with the inorganic salt particles and then incinerating them.

[0010] Preferably, in the method of simulating the inhibition of corrosion of the incinerator by products during the solid waste incineration process, in the step of mixing the solid waste with the inorganic salt particles and then incinerating them, the incineration temperature is 900-1200°C.

[0011] Preferably, in the method of simulating the inhibition of corrosion of the incinerator by products during the solid waste incineration process, in the step of mixing the solid waste with the inorganic salt particles and then incinerating them, the amount of inorganic salt particles added is 3-7% of the mass of the solid waste.

[0012] The application of the inorganic salt particles of the present invention in inhibiting the corrosion of the incinerator during solid waste incineration has the following beneficial effects compared to the prior art:

[0013] 1. The inorganic salt particles of the present invention can inhibit the corrosion of the incinerator by the products of solid waste incineration during the solid waste incineration process. The inorganic salt particles include at least one of kaolin, CaCO3, and TiO2. Before the solid waste is incinerated, the solid waste is first mixed with the inorganic salt particles to obtain a mixture, and the mixture is then placed in an incinerator for incineration. After the inorganic salt particles are mixed with the solid waste, the inorganic mineral composition or particle size distribution of the particles during the solid waste incineration process is changed. As a result, the high-temperature corrosion characteristics of the particles on the heating surface materials inside the boiler are changed, thereby inhibiting the high-temperature corrosion of the incinerator by the products of solid waste incineration;

[0014] 2. The method of simulating and inhibiting the corrosion of the incinerator by the products in the process of solid waste incineration of the present invention is as follows:

[0015] Solid waste is mixed with inorganic salt particles and then incinerated to obtain ash particles with different particle size distributions. The ash particles are then covered on the surface of stainless steel, and the stainless steel is placed in a muffle furnace and heated at 500-1200°C. Since the material of the incinerator is usually also stainless steel, the corrosion of the stainless steel after high-temperature heating in the muffle furnace can be tested to simulate the corrosion of the incinerator by the products during the solid waste incineration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0017] Figure 1 This is the weight gain curve of 304 stainless steel after being corroded by particles generated by MSW combustion;

[0018] Figure 2 This is the weight gain curve of 304 stainless steel after being corroded by particles generated by WW combustion;

[0019] Figure 3 This is the weight gain curve of 304 stainless steel after being corroded by waste paper, yard waste, and food waste particles;

[0020] Figure 4 is the average corrosion rate of 304 stainless steel after being corroded by particles generated by the combustion of MSW and WW;

[0021] Figures 5-6 The weight gain curve of alkali metal and alkaline earth metal salts on 304 stainless steel;

[0022] Figures 7-8 The average corrosion weight gain rate curve of alkali metal and alkaline earth metal salts on 304 stainless steel;

[0023] Figure 9 This is the corrosion weight gain curve of 304 stainless steel caused by particles generated by MSW combustion after the addition of kaolin, CaCO3, and TiO2.

[0024] Figure 10 is the average corrosion weight gain rate of 304 stainless steel caused by particles generated by MSW combustion after the addition of kaolin, CaCO3, and TiO2;

[0025] Figure 11 is the linear fitting curve of Cl+S mass percentage and average corrosion weight gain rate;

[0026] Figure 12is the linear fitting curve of Na+K mass percentage and average corrosion weight gain rate;

[0027] Figure 13 The surface morphology of 304 stainless steel after corrosion by particles of different sizes;

[0028] Figure 14 This is the microscopic morphology of the 304 stainless steel surface after corrosion by submicron particles;

[0029] Figure 15 PM1 and PM generated by MSW combustion 1-2.5 SEM-EDS analysis results of the corrosion layer formed by particles on the surface of 304 stainless steel;

[0030] Figure 16 PM generated by MSW combustion 2.5-10 and PM 10 + SEM-EDS analysis results of the corrosion layer formed by particles on the surface of 304 stainless steel;

[0031] Figures 17-18 This is the XRD pattern of the corrosion layer of 304 stainless steel after corrosion by particles and alkali metal salts. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0033] An embodiment of the present application provides an application of inorganic salt particles as a high-temperature inhibitor during solid waste incineration to inhibit the corrosion of the solid waste incineration products on the incinerator. The inorganic salt particles include at least one of kaolin, CaCO3, and TiO2.

[0034] It should be noted that the inorganic salt particles of the present application can play a role in inhibiting the corrosion of the incinerator by the products of solid waste incineration during the solid waste incineration process. Specifically, before the solid waste is incinerated, the solid waste is first mixed with the inorganic salt particles to obtain a mixture, and then the mixture is placed in the incinerator for incineration. After the inorganic salt particles are mixed with the solid waste, the inorganic mineral composition or particle size distribution of the particles in the solid waste incineration process is changed. As a result, the high-temperature corrosion characteristics of the particles to the heating surface materials inside the boiler will be changed, thereby playing a role in inhibiting the high-temperature corrosion of the incinerator by the products of solid waste incineration.

[0035] In some embodiments, the amount of inorganic salt particles added is 3-7% of the mass of the solid waste.

[0036] Based on the same inventive concept, the present invention also provides a method for simulating and inhibiting the corrosion of an incinerator by products during the incineration of solid waste, comprising the following steps:

[0037] Cover the stainless steel surface with ash particles, then heat the stainless steel in a muffle furnace at 500-1200°C and test its corrosion condition;

[0038] Among them, ash particles are the products obtained by mixing solid waste with inorganic salt particles and then incinerating them.

[0039] In some embodiments, in the step of mixing the solid waste with the inorganic salt particles and then incinerating them, the incineration temperature is 900-1200°C.

[0040] In some embodiments, in the step of mixing the solid waste with the inorganic salt particles and then incinerating them, the amount of the inorganic salt particles added is 3-7% of the mass of the solid waste.

[0041] Specifically, the stainless steel is 304 stainless steel.

[0042] In the above embodiment, solid waste is mixed with inorganic salt particles and then incinerated to obtain ash particles with different particle size distributions. The ash particles are then covered on the surface of stainless steel, and the stainless steel is placed in a muffle furnace and heated at 500-1200°C. Since the material of the incinerator is usually also stainless steel, by detecting the corrosion of the stainless steel after high-temperature heating in the muffle furnace, the corrosion of the incinerator by the products during the solid waste incineration process can be simulated.

[0043] In some embodiments, the stainless steel is placed in a muffle furnace and heated at 500-1200° C. for 0-84 hours.

[0044] The following further illustrates the use of the inorganic salt particles of the present application as a high-temperature inhibitor to inhibit the corrosion of the products of solid waste incineration to the incinerator during the solid waste incineration process, as well as a method for simulating the inhibition of the corrosion of the products of solid waste incineration to the incinerator. This section further illustrates the content of the present invention in conjunction with specific examples, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the examples are conventional means familiar to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0045] Example 1

[0046] The present invention provides a method for simulating and inhibiting the corrosion of an incinerator by products during the incineration of solid waste, comprising the following steps:

[0047] S1. 304 stainless steel (SUS304) was used as the material for the high-temperature corrosion experiment. Before the experiment began, two 1mm thick 304 stainless steel samples were cut into 10mm long and 10mm wide sizes. They were then polished with 400-mesh water-resistant sandpaper to remove surface oil stains and rust. Finally, they were washed with clean water and dried in a 105°C oven.

[0048] S2. Place the polished 304 stainless steel into an alumina crucible with a size of 30mm*20mm*17mm. The surface of the 304 stainless steel is evenly covered with a mixture of solid waste and inorganic salt particles with a thickness of 1mm, and then incinerated to obtain ash particles (as a corrosion medium). The crucible containing the corrosion medium and the steel sample is then placed together in a muffle furnace at a heating temperature of 600°C. The experimental atmosphere is air to simulate the corrosion conditions of the heat exchange material in the waste incinerator. After the experiment is completed, the corrosion of the steel is tested.

[0049] Comparative test: According to the same method as in Example 1 above, volatile alkali metal salts (NaCl, KCl, Na2SO4, Na2CO3) and calcium salts (CaCl2 and CaSO4) were evenly covered on the surface of 304 stainless steel as corrosion media, and the corrosion of the steel was tested. A blank control group was also set up.

[0050] Specifically, the corrosive media in Example 1 and the comparative test are shown in Table 1 below.

[0051]

[0052]

[0053] In Table 1, solid wastes include municipal solid waste (MSW), refuse-derived fuel (RDF), waste wood (WW), waste paper, yard waste, and food waste. All samples were collected from the waste treatment plant of Enerkem Inc. in Edmonton (Alberta, Canada). Particulate matter with a diameter of less than or equal to 1 μm is referred to as PM1, and particulate matter with a diameter of 1 to 2.5 μm is referred to as PM2. 1-2.5 , particles with a diameter of 2.5 to 10 μm are called PM 2.5-10 , particles with a diameter greater than 10 μm are called PM 10 + In Table 1, MSW-1100℃-PM1 indicates that the particles with a diameter less than or equal to 1 μm formed after MSW is burned at 1100℃ are called PM1 (the other WW, waste paper waste, yard waste, and food waste have similar meanings); MSW-1100℃-PM 10 + PM refers to the particulate matter with a diameter greater than 10 μm formed after MSW is burned at 1100°C.10 + MSW-1100°C + Kaolin (5%) - PM1: PM1 is formed when a mixture of MSW and kaolin (5% by mass of MSW) is burned at 1100°C. (CaCO3 (5%) and TiO2 (5%) have the same meaning.) NaCl:Na2SO4=1:1: The mass ratio of NaCl to Na2SO4 is 1:1 (NaCl:Na2SO4=1:2 and NaCl:Na2SO4=2:1: The mass ratios are 1:2 and 2:1, respectively). For details on the combustion mechanism, see the published paper: Particulate matter emission during municipal solid waste combustion: Submicron particulates formation mechanism, Fuel.2022.310.122271.

[0054] Performance Testing

[0055] 1. High-temperature corrosion characteristics of MSW and WW particles

[0056] The weight gain curve and average corrosion rate of 304 stainless steel after being corroded by particles generated by MSW and WW combustion are as follows: Figures 1 to 4 Specifically, Figure 3 No ash refers to the blank control group without any corrosive medium, Paper waste, Food waste, and Yard waste refer to waste paper, yard waste, and food waste, respectively.

[0057] from Figures 1 to 3 It can be seen that the high-temperature corrosion weight gain curve of the particles shows two stages with different rates. Within 24 hours, the corrosion curve grows rapidly and the corrosion rate is relatively high. Between 24 and 84 hours, the slope of the corrosion weight gain curve slows down relatively, but the corrosion mass continues to grow. The atmosphere sampled in the corrosion experiment in this application is air. Figure 3 It can be seen that except for WW and waste paper PM 10 + In the particle corrosion experimental group, the corrosion rates of other particles were higher than those of the air corrosion control group without ash particle coverage. This indicates that at 600°C, the corrosion rate of the 304 stainless steel surface covered with particles generated by solid waste combustion is usually higher than the corrosion rate under the action of air alone.

[0058] like Figure 4 As shown in Figure 2, the average corrosion weight gain rate of submicron particles PM1 generated by MSW combustion is 368 μg / (cm2 h) and 161 μg / (cm 2 The average corrosion weight gain rate of submicron particles PM1 generated by WW combustion was 177 μg / (cm2) within 24 hours and 84 hours. 2 h) and 87 μg / (cm 2 ·h), were significantly higher than PM 1-2.5 、PM 2.5-10 、PM 10 + Corrosion rate of particles. Comparative analysis shows that the corrosiveness of submicron particles PM1 is about 10 + When the source of the particles is the same, the smaller the particle size, the higher the average corrosion weight gain rate, that is, the more corrosive the particles are. Figures 1 to 4 It was also found that when the particle size is the same, the particles generated by MSW combustion are more corrosive than those generated by WW combustion. The PM generated by the combustion of waste paper waste, food waste and yard waste, which are typical components of MSW, is 10 + The order of corrosiveness of particulate matter is: food waste > yard waste > waste paper. The inorganic mineral composition of particulate matter produced by combustion of different solid waste fuels varies significantly, and this difference also increases with particle size. Therefore, the impact of particle size and solid waste fuel differences on the high-temperature corrosiveness of particulate matter may be related to the mineral composition and content of the ash particles.

[0059] 2. High temperature corrosion characteristics of alkali metal salts and alkaline earth metal salts

[0060] The inorganic mineral components of particulate matter generated by the combustion of municipal solid waste contain high levels of alkali metal salts and alkaline earth metal salts. 0.2 (indicates particulate matter with a diameter less than or equal to 0.2 μm) and PM 0.2-1 In PM2.5 (expressed as particulate matter of 0.2 to 1 μm), the total amount of alkali metal chlorides and sulfates accounted for 84.9% and 73.8% respectively. 2.5-10 and PM 10 + There are a large number of alkaline earth metal sulfates and chlorides such as CaSO4 and CaCl2 in the particulate matter. In order to study the corrosion strength of alkali metal and alkaline earth metal salts, typical components of particulate matter, at high temperatures, this chapter also conducts corrosion experiments on alkali metal carbonates. Due to the low melting point, alkali metal hydroxides begin to melt and evaporate between 300-400°C. It is difficult to exist stably in a solid state within the temperature range of this application. Therefore, no corrosion experiments were conducted on them in this study. The corrosion weight gain curve and average corrosion rate are shown in Figure 2. Figures 5 to 8 shown.

[0061] from Figures 5 to 8 It can be seen that the corrosion curves of alkali metal and alkaline earth metal salts on 304 stainless steel are similar to the change pattern of particle corrosion curves. Within 24 hours, high-speed corrosion weight gain also occurs. After more than 24 hours, the corrosion weight gain rate of 304 stainless steel slows down significantly. The average corrosion weight gain rates of NaCl, KCl, Na2SO4, K2SO4, Na2CO3, CaCl2 and Ca2SO4 over 84 hours are 135μg / (cm 2 h)、158μg / (cm 2 ·h)、40μg / (cm 2 ·h)、63μg / (cm 2 ·h)、48μg / (cm 2 ·h)、95μg / (cm 2 h) and 29 μg / (cm 2 h). Therefore, at 600°C in air, the order of corrosivity of alkali and alkaline earth metal salts is: KCl > NaCl > CaCl2 > K2SO4 > Na2SO4 > Ca2SO4. Alkali and alkaline earth metal chloride salts are generally more corrosive than sulfate salts, and Na2CO3 is more corrosive than Na2SO4. Among chloride and sulfate salts composed of K, Na, and Ca, K salts are relatively the most corrosive, followed by Na salts, and Ca salts are the least corrosive.

[0062] Generally, the melting point of minerals composed of a mixture of different types of alkali metal salts is lower than that of alkali metal salt minerals composed of a single component. Taking NaCl and Na2SO4 as an example, the melting points of NaCl and Na2SO4 are 801°C and 884°C respectively, but when the two are mixed, the melting point of the mixed salt formed can be as low as 628°C. The corrosion behavior of potassium chloride and sodium chloride on the surface of metal or alloy materials at high temperatures is basically similar. Therefore, in order to study the high-temperature corrosion behavior of 304 stainless steel when alkali metal chlorides and sulfates coexist, this application only selects the mixture of Na chloride and sulfate for experiments. The high-temperature corrosion weight gain curves of 304 stainless steel caused by the mixture of NaCl and Na2SO4 at a mass ratio of 1:1, 1:2 and 2:1 are shown as follows. Figure 6 The average corrosion weight gain rates for 24 hours and 84 hours are summarized in Figure 8 Comparative analysis shows that under the same corrosion conditions, the corrosiveness of the mixture of NaCl and Na2SO4 gradually increases with the increase of the proportion of NaCl. When the mass ratio of NaCl to Na2SO4 is 2:1, the corrosiveness of alkali metal salts is the strongest, and the average corrosion rates of alkali metal salts for 24 hours and 84 hours are 324μg / (cm 2 h) and 167 μg / (cm 2·h), the corrosion rate is even higher than that of the single-component NaCl experimental group. Comparing the experimental and theoretical calculation values of the corrosion rate of NaCl and Na2SO4 mixed salts at different mixing ratios, it is found that the corrosiveness of the mixed alkali metal salts is enhanced to varying degrees. When the NaCl ratio is high, such as when the mass ratio of NaCl to Na2SO4 is 2:1, the mixed salt of NaCl and Na2SO4 has the strongest promoting effect on corrosion. Figure 4 It can be seen that the average corrosion weight gain rate of submicron particles generated by MSW combustion is higher than Figures 5 to 8 It can be inferred that the high-temperature corrosion characteristics of submicron particles are the result of the mutual promotion of multiple alkali metal and alkaline earth metal salt components, and the final corrosion rate is stronger than the corrosion rate of any inorganic salt component.

[0063] 3. High-temperature corrosion rate of particles under the action of kaolin, CaCO3, and TiO2

[0064] After the addition of kaolin, CaCO3 and TiO2, the high temperature corrosion characteristics of the particles generated by MSW combustion are as follows: Figures 9-10 shown. Figures 9-10 Kaolin in Chinese refers to kaolin.

[0065] from Figures 9-10 It can be seen from the figure that the corrosiveness of the particles generated by the combustion of MSW mixed with kaolin additives to 304 stainless steel increases with decreasing particle size, which is consistent with the corrosiveness of the particles generated when MSW is burned without additives. Figure 10 It can be seen that the PM1 and PM2.5 generated by the combustion of MSW+kaolin (5%) 1-2.5 The average corrosion weight gain rate after 84 hours of corrosion test was 129 μg / (cm 2 h) and 68 μg / (cm 2 ·h), which are lower than the corrosive capacity of submicron particles generated by burning MSW alone. PM generated by burning 5% kaolin, CaCO3, TiO2 additives with MSW 2.5-10 / PM 10 + The average corrosion weight gain rate of the particles over 84 hours was 50 μg / (cm 2 h) / 42μg / (cm 2 ·h)、56μg / (cm 2 h) / 29μg / (cm 2 h) and 43 μg / (cm 2 h) / 29μg / (cm 2h). Calculation and analysis show that after MSW is mixed with 5% kaolin, the PM1 and PM2.5 generated by combustion are 1-2.5 、PM 2.5-10 and PM 10 + The corrosiveness of MSW decreased by 20%, 17%, 23% and 2% respectively compared with that without kaolin. 2.5-10 and PM 10 + The corrosiveness of MSW decreased by 14% and 33% respectively compared with that without additives. 2.5-10 and PM 10 + The corrosion of MSW decreased by 34% and 33% respectively compared with that without additives. This shows that Si / Al-based (i.e. kaolin), Ca-based and Ti-based additives can reduce the high-temperature corrosion of particulate matter generated by MSW combustion to 304 stainless steel. In addition, the experimental data also show that compared with the other two additives, the PM generated by MSW combustion after 5% CaCO3 additive is less than 10% of that of MSW. 2.5-10 The corrosion rate of the particles is relatively high. This may be because the proportion of CaCl2 in the particles generated after the co-combustion of CaCO3 and MSW is relatively high. Although the corrosiveness of CaCl2 is lower than that of NaCl and KCl, it is higher than that of other alkali metal and alkaline earth metal salts.

[0066] 4. Effect of inorganic element composition of particulate matter on corrosion rate

[0067] In order to explore the reasons for the difference in corrosiveness of particulate matter generated by the combustion of municipal solid waste before and after mixing and without additives, this application is based on the 24-hour and 84-hour average corrosion weight gain rate of 304 stainless steel and the mass proportion of Na, K, Cl, and S elements in the particulate matter. Figure 11 and 12 The linear fitting curves of the mass percentage of Na+K and Cl+S and the average corrosion weight gain rate were drawn respectively.

[0068] from Figures 11-12It can be clearly seen that the high-temperature corrosion rate of particulate matter on 304 stainless steel increases with the increase of Cl, S content or Na, K content in the particulate matter. The slope of the function equation fitted with the 24-hour average corrosion weight gain rate as the vertical coordinate is higher than that of the 84-hour corrosion case, indicating that the corrosion rate of the particulate matter in the early stage within 24 hours is faster than that in the later stage. This shows that Na and K in the particulate matter generated by solid waste combustion mainly exist in the form of alkali metal chlorides and sulfates. Both Na+K and Cl+S show a good linear correlation with the corrosion rate, which indirectly proves that the corrosion of the particulate matter is caused by its alkali metal chloride and sulfate components. The blending of Ca-based, Ti-based and Si / Al-based additives leads to a decrease in the proportion of corrosive media formed by Cl, S and alkali metals in particulate matter of different particle sizes generated by MSW combustion, that is, the content of alkali metal chlorides and sulfates is reduced, and thus the corrosiveness of the particulate matter is weakened.

[0069] 5. The efficiency of additives in controlling high-temperature corrosion of particulate matter

[0070] The high-temperature corrosion rate of particles generated by MSW combustion has changed significantly after the addition of kaolin, CaCO3, and TiO2 additives. The high-temperature corrosion rate of particles generated by the combustion of 5% kaolin, CaCO3, and TiO2 additives mixed with MSW has decreased to varying degrees. In order to quantify the corrosion mitigation effect of particles after the addition of additives, this study defines the high-temperature corrosion rate and corrosion control efficiency of particles. The average high-temperature corrosion rate V of ash particles generated by the combustion of MSW alone or mixed with additives is ash ;in,

[0071]

[0072]

[0073] Where: PM n Indicates PM1, PM 1-2.5 、PM 2.5-10 and PM 10 + Particulate matter, V PMn Indicates PM n High temperature corrosion rate of particles, m yieldPMn W represents the mass yield of particles with a particle size of n (n = 1 μm, 1-2.5 μm, 2.5-10 μm or >10 μm). PMn Indicates PM n The mass percentage of particle yield in the total particle yield. PMn Obtained from the 84-hour average corrosion rate experimental data of this application.

[0074] The calculation formula for the comprehensive corrosion control efficiency η of the additive on particulate matter generated by MSW combustion is defined as follows: Note: V ash V′ represents the average high-temperature corrosion rate of particles generated when MSW is burned alone. ash It represents the average high-temperature corrosion rate of particles generated by burning MSW with additives.

[0075] The V values of MSW in the combustion group alone and the MSW + 5% kaolin group were significantly different. PMn 、W PMn The experimental values are shown in Table 2. From this, the corrosion rate V of particles on 304 stainless steel at 600 ° C can be calculated respectively. ash and V′ ash 49.32 μg / (cm 2 h) and 43.36 μg / (cm 2 h). In other words, during the MSW combustion process, when the heating surface material is 304 stainless steel and the surface temperature is 600°C, the comprehensive corrosion control efficiency of adding 5% kaolin on particulate matter in high-temperature flue gas is 12%.

[0076] Table 2 - Particle yield ratio and corrosion rate

[0077]

[0078] 6. Corrosion morphology and microstructure

[0079] 304 stainless steel material after corrosion by particles of different sizes Figure 13 shown. Figure 13 304 stainless steel after 84 hours of medium corrosion: (a) Steel sample after MSW-1100℃-PM corrosion, (b) Steel sample after MSW+kaolin (5%)-1100℃-PM corrosion, (c) Cross-sectional morphology of 304 stainless steel after MSW-1100℃-PM1 corrosion.

[0080] from Figure 13 It can be seen that the corrosion caused by particles with smaller particle size is more serious than that caused by coarse particles with larger particle size, while the particles generated after kaolin additive burning are less corrosive than MSW ash particles without kaolin additive burning. This phenomenon is consistent with Figures 1 to 4 and Figures 9-10 The conclusion drawn from the corrosion weight gain rate is consistent with the conclusion drawn from the corrosion weight gain rate. The cross-sectional SEM analysis of the steel slice after high temperature corrosion of particles is as follows: Figure 13As shown in Figure (c), the cross-section of the corroded steel can be divided into three layers: the inner layer is a dense metallic steel matrix; the outer layer is a deposited layer formed by ash particles generated by the combustion of solid waste; and the middle layer is a porous and loose corrosion layer formed by ash particles or gases such as oxygen in the flue gas corroding the steel matrix surface. The presence of ash particle deposits leads to the formation of a rough and porous surface on the 304 stainless steel matrix material, causing serious defects and cracks within the steel, which reduces the service life of the 304 stainless steel.

[0081] Particle corrosion can easily cause holes and cracks on the surface and interior of the heating surface material, resulting in a decrease in the pressure resistance of the superheater pipes, and eventually causing pipe bursts and steam leaks. Figure 14 As shown in the figure (microscopic morphology of the surface of 304 stainless steel after corrosion by submicron particles), from the SEM microstructure, the surface of 304 stainless steel showed large-scale corrosion cracking and pitting corrosion after high-temperature corrosion by submicron particles. Corrosion cracking is caused by the fracture of the corrosion layer due to stress changes during heating and cooling after the brittle corrosion layer is formed on the surface of the steel. Pitting corrosion may be caused by the chemical reaction between corrosive components such as chlorine-alkali metal salts in the particles and the metal matrix. From the locally enlarged microstructure of the pitting holes in the figure, it can be seen that the larger pitting holes are convex outward on all sides and concave inward on the inside, while the smaller pitting holes are in the shape of a hill with a convex middle part. This shows that the pitting holes are hollow inside, and the surface is formed by the accumulation of multiple granular substances that are connected to each other but not dense. When the hole size inside the pitting holes gradually grows, the loose granular corrosion material on the top gradually collapses inward, thus forming Figure 14 The pitting structure in the. A large number of studies have shown that pitting holes are formed by the reaction of Cl2 or O2 with metal elements and their metal oxide films. Chlorine elements directly enter the metal / oxide film interface through the pitting holes in the form of Cl2 molecules, providing raw materials for the occurrence of metal chlorine corrosion. Under high temperatures, metal chlorides continue to evaporate and diffuse outward, and are rapidly oxidized in areas rich in O2 concentration, regenerating loose metal oxides and Cl2. In this process, once Cl2 is generated, it acts like a catalyst to promote the corrosion reaction in a cyclical manner. This application uses an air atmosphere, and Cl2 cannot come from external gases, so it can only come from alkali metal chloride salts in particulate matter.

[0082] 7. Analysis of inorganic mineral components in the corrosion layer

[0083] Figure 15 It represents PM1 and PM2.5 generated by MSW combustion. 1-2.5 SEM-EDS analysis results of the corrosion layer formed by particles on the surface of 304 stainless steel. Figure 15(a) Microscopic morphology shows that after size enlargement, the submicron particle deposition layer on the corrosion layer surface is loose and porous. Its structure is conducive to the diffusion of gases in the external environment inside the ash particles and on the surface of the corroded steel, and is also conducive to the overflow of gaseous corrosion products. Figure 15 (b) The Cl, S and K element contents at point 1 account for 37.56%, 10.49% and 25.67% respectively, indicating that the particles may be KCl or K2SO4 particles adhering to the metal surface. EDS detection also found that there are a variety of corrosion products on the surface of the corrosion layer of submicron particles. The loose and porous mineral salt particles at point 2 may be iron oxide or chromium oxide. In addition to containing a high proportion of Si, Al, O and K elements, the inorganic salt particles at point 3 also contain a high proportion of Cr and Fe elements (the mass proportions are 5.02% and 6.8% respectively), so this area may be a mixture of alkali metal aluminosilicates and alkali metal chromates or ferrites. Compared with submicron particles, although fine particles PM 1-2.5 The melting point of inorganic mineral components is higher, but Figure 15 The presence of molten material was also observed in the SEM morphology of the corrosion product in (c), which indicates that some inorganic mineral components in the particles reacted with the metal on the heated surface to form new low-melting-point minerals.

[0084] Figure 16 PM generated by MSW combustion 2.5-10 and PM 10 + SEM-EDS analysis results of the corrosion layer formed by particles on the surface of 304 stainless steel. Figure 16 It can be seen that, unlike the surface morphology after corrosion of fine particles, the surface of coarse particles has fewer molten particles, more raised structures appear on the surface of the corrosion layer, and the corrosion layer has cracked. Combined with EDS analysis, it can be seen that the inorganic minerals on the surface of the corrosion layer after corrosion of coarse particles are mainly metal oxides Fe2O3 and Cr2O3, and the Cr2O3 content at point 1 is higher than that at the other two points. Comparing the relative contents of Cl, S, Na and K elements in the outer corrosion layer (point 2) and the inner corrosion layer (point 3), it can be seen that the content of alkali metals Na, K and S in the outer corrosion layer is higher than that in the inner corrosion layer, but the Cl element is completely opposite. In addition, the law of the proportion of Fe and Cr elements in the inner and outer corrosion layers is consistent with that of Cl, and opposite to that of S. It is speculated that the reason for this phenomenon may be due to the different corrosion rates and corrosion mechanisms of chloride and sulfate.

[0085] In order to further study the inorganic mineral composition of the corrosion layer on the surface of 304 stainless steel after particle corrosion, the corrosion layer on the surface of the steel after different types of particle corrosion was scraped off, ground into powder particles, and then XRD was performed on them respectively. Figures 17-18As shown. Figures 17-18 It can be seen that a large amount of Fe2O3 and Cr2O3 were detected in the corrosion layers of almost all the particle experimental groups, which shows that metal oxides are the main products of corrosion under the conditions of the presence of particles and oxygen. Figures 17-18 Substances such as NaCl, KCl, K3Na(SO4)2, and SiO2 were detected in some experimental groups. These substances mainly come from particulate matter. After being heated during the corrosion test, they adhere to the surface of the 304 stainless steel material and cannot be removed. In addition, XRD also detected the presence of inorganic mineral components such as K2CrO4, NaFeO2, Na2CrO4, and FeCr2O4 in the corrosion layer of the particulate matter, but due to their low content, the diffraction peaks were not very obvious. After comparison, it was found that these ferrite and chromate substances were more likely to be detected in the corrosion layer of the experimental group with smaller submicron particles and the experimental group with food waste particles, but were less likely to be detected in the other particle experimental groups. From the XRD test results after NaCl, KCl, Na2SO4 and Na2CO3 corrosion, it can be found that in addition to the main corrosion products Fe2O3 and Cr2O3, K2CrO4 was detected in the corrosion products of KCl, NaFeO2 and Na2CrO4 were detected in the corrosion products of NaCl, and the characteristic peaks of the corrosion products of Na2SO4 and Na2CO3 were not obvious, but a small amount of Na2CrO4, NaFeO2 and FeCr2O4 components were also detected. In addition, in the corrosion products of the mixed salt of NaCl and Na2SO4, in addition to the above-mentioned sodium ferrite and sodium chromate, the characteristic peak of NaCr2O7 was also detected.

[0086] In summary, this application used 304 stainless steel, a typical superheater piping material, and conducted high-temperature corrosion experiments using particulate matter derived from solid waste combustion and its typical inorganic salt components. The high-temperature corrosion rates of particles of varying sizes generated by MSW combustion were investigated before and after the addition of additives. The effectiveness of Si / Al additives in controlling high-temperature corrosion of the particles was also calculated. Combined with the micromorphology and corrosion product analysis of the particle corrosion layer, the high-temperature corrosion mechanism of the particles was explored. The following conclusions were drawn:

[0087] (1) The smaller the particle size of the MSW combustion particles, the stronger the high-temperature corrosion of 304 stainless steel. The average corrosion rate of submicron particles PM1 on 304 stainless steel at 600℃ for 84 hours is 161μg / (cm 2 ·h), whose corrosiveness is about PM 10 + When the particle size is the same, the corrosiveness of the particles generated by MSW combustion is stronger than that of WW combustion. 10 +The order of corrosiveness of particulate matter is: food waste > yard waste > waste paper waste.

[0088] (2) At 600°C and in an air atmosphere, the chloride salts of alkali metals and alkaline earth metals are generally more corrosive to 304 stainless steel than sulfate salts, and Na2CO3 is more corrosive than Na2SO4. Among the chloride salts and sulfate salts composed of K, Na, and Ca, K salts are the most corrosive, followed by Na salts, and Ca salts are the least corrosive. The corrosiveness of NaCl and Na2SO4 mixed is significantly enhanced, and the corrosiveness of the mixed salt is stronger than that of any of its component alkali metal salts. As the proportion of NaCl in the mixed salt of NaCl and Na2SO4 increases, the corrosiveness of the mixed salt gradually increases. When the mixing ratio of NaCl in the mixed salt is increased to 66.6%, the actual corrosion capacity is 62% higher than the theoretical value.

[0089] (3) During MSW combustion, when the heating surface material is 304 stainless steel and the surface temperature is 600°C, the addition of 5% by mass of kaolin can reduce the comprehensive corrosion capacity of particulate matter in the high-temperature flue gas by 12%. After the slag and ash layers on the surface of the heating surface material in the high-temperature flue gas are stabilized, the addition of 5% by mass of kaolin can reduce the corrosion rate of 304 stainless steel by 71%.

[0090] (4) The high-temperature corrosion products between particles and 304 stainless steel are mainly Fe2O3, Cr2O3, K2CrO4, NaFeO2, Na2CrO4 and FeCr2O4. Among them, Fe2O3 is more likely to form in the outer corrosion layer, and Cr2O3 is more likely to form in the inner corrosion layer. The high-temperature chlorine corrosion process of particles starts with the reaction of alkali metal chloride salts with metal elements or their oxides. During the entire corrosion process, Cl2 acts as an active intermediate substance and can self-sustain the entire high-temperature chlorine corrosion process in a molten system without further consumption of additional alkali metal chloride salts. The pitting structure can provide a channel for the transfer of corrosion intermediate products (Cl2, FeCl2, CrCl2) during the entire corrosion process, accelerating the chlorine corrosion process.

[0091] (5) The high-temperature corrosion rate of submicron particles produced by MSW combustion on 304 stainless steel is higher than that of any alkali metal salt component. The high-temperature corrosion process of particles is mainly dominated by the mineral components NaCl, KCl, CaCl2, Na2SO4, and K2SO4. The relative content of these mineral components determines the corrosion ability of particles of different particle sizes. When alkali metal chlorides and sulfates coexist, they can promote the entire corrosion reaction process by accelerating the dissolution of the oxide layer on the metal / alloy surface or lowering the melting point of the mixed molten salt.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. 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 simulating and inhibiting the corrosion of solid waste incineration products on an incinerator, characterized in that: The following steps are involved: The stainless steel surface was covered with ash particles, and then the stainless steel was placed in a muffle furnace and heated at 600°C, and its corrosion condition was tested; Among them, ash particles are the products obtained by mixing solid waste with inorganic salt particles and then incinerating them; In the step of mixing the solid waste with the inorganic salt particles and then incinerating, the incineration temperature is 1100°C; In the step of mixing the solid waste with the inorganic salt particles and then incinerating them, the amount of the inorganic salt particles added is 5% of the mass of the solid waste; The inorganic salt particles are TiO2; Solid waste is municipal solid waste; Ash particles are particles with a diameter greater than 10 μm formed by mixing solid waste with inorganic salt particles and burning them at 1100°C.

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