Research Progress on Corrosion Influencing Factors and Protective Coatings of Superheater in Waste Incineration Power Plants

High-temperature corrosion of superheater tubes has been a critical problem restricting incineration temperature. Therefore, research and development of crucial service materials with high-temperature corrosion resistance and long life is the key to ensure regular operation and safe production of waste incinerators. To effectively improve waste incineration temperature and operational safety, and improve power generation efficiency, the preparation of protective coatings on the surface of superheater pipes has become a key measure to solve high-temperature corrosion. In this work, the research status of the hot corrosion in waste incineration boilers in recent years was reviewed, and the research results of corrosion and protection of superheater in waste incineration boilers were summarized. Firstly, from the perspective of the factors affecting the corrosion of the superheater, the corrosion characteristics under the influence of many factors such as chlorine, sulfur, temperature, water vapor, etc., were summarized, and the corrosion mechanism under each influencing factor was analyzed. Cl and S were the critical problems affecting corrosion. Several main high-temperature chlorine corrosion mechanisms of waste incineration were focused on the analysis, including chloride ion induced active corrosion and electrochemical corrosion. The dual effect of sulfur on corrosion, its corrosion mechanism, and sulfur can lead to the transformation from the more corrosive chloride into less corrosive sulfate under certain circumstances. Secondly, the development of coating preparation technology applied on the superheater surface was discussed, including thermal spraying, thermal diffusion, surfacing, laser cladding, etc. Specific reasons for improving alloys' corrosion resistance by various technologies were elucidated. In terms of the existing high-temperature anti-corrosion coating technology, the arc spraying technology had huge advantages in the protection of superheater tubes of the waste incinerator due to its simple equipment, low cost, high deposition efficiency and flexible operation. The continuous development of powder core wire composition design showed great potential and was expected to further improve the high-temperature corrosion resistance of arc sprayed coatings. This technology may become an effective technology for on-site preparation of protective coatings. Ultra-high-speed laser cladding technology will also be the key development direction for the preparation of superheater tube protective coatings in the future due to its unique advantages and extremely high cladding efficiency for rotary parts. The relationship between the addition of material components (such as Ni, Mo, Cr, Al, Si, Pt and other elements) and the corrosion resistance of the coating was analyzed. The harmless disposal of flue gas was also a vital issue in the research of key service materials for waste incineration. From the perspective of incineration of garbage pretreatment, the early dewatering of garbage was discussed further. Combustion additives were added to achieve the purpose of desulfurization, dechlorination, to reduce the sulfur and chlorine content in flue gas and reduce the impact of corrosion. Because Cl, S, water vapor, and other factors in garbage are almost impossible to eliminate, when the garbage incineration temperature is too high, the corrosion of the critical heating surface still cannot be avoided entirely. The existing problems and the future development trends of typical key materials and coatings on the superheater pipe of waste incinerators were also summarized and proposed, respectively, which would provide a valuable reference for further popularization and application of typical essential service materials of waste incinerators. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.