Application of Coatings to Alleviate Fireside Corrosion on Heat Transfer Tubes during the Combustion of Low-Grade Solid Fuels: A Review

Abstract

To address the energy and environmental issues related to the use of traditional fossil fuels, the thermal utilization of low-grade solid fuels such as low-rank coal, biomass, and municipal solid waste has gradually attracted much attention. During the combustion of the low-grade solid fuels, one of the major operation problems is the fireside corrosion on heat transfer tubes, which easily causes the frequent replacement of tubes and shutdown of boilers, largely reducing the energy and economic performances. In this review, the causes and mechanisms of corrosion were first clarified to provide a basis for mitigating the losses induced by the fireside corrosion, followed by the introduction of the preparation and properties of coatings, which show great potential to resist the invasion of corrosive species by attaching the reinforced surface to the tubes. To demonstrate the feasibility of the coating for hightemperature corrosion resistance, 94 kinds of coatings in more than 60 literature contributions were statistically analyzed. It was found that over 90% of anticorrosion coatings were prepared from thermal spraying techniques, and approximately three-quarters of the anticorrosion coatings were made of NiCr-based alloys. Many methods were reported to evaluate the corrosion resistance of coatings in literature, including mass gain/loss method, ash deposition method, contact angle method, and ash adhesion method. As for exploring the anticorrosion mechanisms of coatings, it was found that the protection was achieved by the formation of dense oxide scale, such as Cr 2 O 3 , NiO, MoO 2 , and so on. Furthermore, the application status of coatings in power plants was also summarized. According to the pilot-scale tests listed in literature, the obvious similarity is that the adopted technologies were mainly High velocity oxy-fuel (HVOF) spraying or cold spraying techniques, with almost all of the coated materials being NiCr-based alloys as well as a small portion of Fe/Co-based alloys. This indicates that the NiCr-based coatings prepared by HVOF spraying technique have been widely applied in power plants. In order to promote the large-scale application of anticorrosion coatings, it is prospective to focus on several key research aspects: (1) predicting the corrosion conditions from fuel compositions, (2) developing costeffective coatings, (3) establishing the systematic evaluation methods by laboratory tests, (4) achieving in-depth understanding of the anticorrosion mechanisms, and (5) conducting a comprehensive economic analysis.

Research hotspots and future trends of hot corrosion research: a bibliometric analysis

“…One recommendation was to use a coating that may increase the corrosion resistance of the materials. Accordingly, Zhang X. et al 87 work has compiled some coating materials that have been studied to combat the hot corrosion in power plants with low-grade solid fuels. According to Zhang, high velocity oxy-fuel (HVOF) was the most preferred depositing method for researchers to study the hot corrosion behavior of coatings.…”

Virtual Special Issue of Recent Research Advances in China: Thermochemical Processing of Biomass and Solid Wastes

“…Leng et al 6 present a review on the mechanisms governing the cold flow properties (CFPs) of biodiesel and provide a critical discussion on the potential methods for improving the CFPs of biodiesel. Zhang et al 7 systematically summarize the causes and mechanisms of corrosion on heat transfer tubes during the combustion of low-grade solid fuels and present the status and prospectives of the application of coatings to alleviate fireside corrosion. Peng et al 8 provide a comprehensive review of the formation, measurement, and control of dioxins during the incineration of municipal solid wastes.…”

High-Efficiency Preparation of Reduced Graphene Oxide by a Two-Step Reduction Method and Its Synergistic Enhancement of Thermally Conductive and Anticorrosive Performance for Epoxy Coatings

“…The main problems with the anticorrosive coating of industrial heat exchange equipment are that the coating with a good anticorrosion property has a poor heat transfer property and the coating with a desirable heat transfer property has a poor anticorrosion property. Corrosion of heat exchange equipment is a main reason for its failure, and the working efficiency of the equipment is dependent on its heat transfer property. , Epoxy or modified epoxy resin are used extensively for anticorrosive coatings due to their low cost, good barrier property, and chemical stability. , But, the low thermal conductivity of epoxy (∼0.20 W/(m·K)) limits their applications as a corrosion protective coating for industrial heat exchange equipment . And the existence of microdefects and pinholes of epoxy coating may result in the deterioration of corrosion protection performance.…”

“…Corrosion of heat exchange equipment is a main reason for its failure, and the working efficiency of the equipment is dependent on its heat transfer property. 1,2 Epoxy or modified epoxy resin are used extensively for anticorrosive coatings due to their low cost, good barrier property, and chemical stability. 3,4 But, the low thermal conductivity of epoxy (∼0.20 W/(m•K)) limits their applications as a corrosion protective coating for industrial heat exchange equipment.…”