Development of thermal sprayed layers for high temperature areas in waste incineration plants

Abstract

Corrosion and wear in the hot gas area of thermal energy plants are severe problems, which often cause premature damage of components. In general, the most components of plants are made of materials, which are not stable under corrosive conditions. For corrosion protection (and also wear protection) and lifetime extension of these components, coatings with more resistant materials are applied. Because of the high concentration of corrosive species and the alternating composition of the atmosphere near to the components, the waste incineration plant is the ''worst case'' of high temperature corrosion. Nowadays, the most usual coating process to protect pipes in the waste incineration plants is cladding. In the last few years, alternative processes are under investigation because cladding is very cost-intensive. The specific costs of thermal spraying are much lower than those of cladding. In addition, the coating by thermal spraying reduces the risk of the dilution of substrate and coating material, different materials can be combined (e.g. metal alloys, ceramics) and the thickness of the layer for an acceptable resistance according to corrosion and wear can be drastically reduced. Thermal spraying has the potential to create cost-efficient coatings to protect components in the critical zones of incineration plants.Since many years, ATZ Entwicklungszentrum is involved in the development and/or advancement of materials, technologies and applications of thermal spraying for corrosion and/or wear protection in thermal energy plants. The main focuses of the investigations are layers for components in high temperature areas of waste incineration plants. On the basis of the present results, different coatings (metal alloys, ceramics) and different spray technologies (e.g. HVOF, APS) have been tested by different strategies (corrosion tests under laboratory scale, air cooled material probes inside the hot gas area of an incineration plant and coated pipes in operation as part of the superheater of incineration plants). This paper will give an overview about the current results of these corrosion tests, in which the focus are the investigations with material probes. First results showed that with the combination of different thermal sprayed layers a significant corrosion protection can be achieved.

High Temperature Corrosion Studies of a Zirconia Coating: Implications for Waste-to-Energy (WTE) Plants

“…An alternative approach is to use APS-applied multilayer coatings as durable corrosion inhibitor materials. Corrosion tests within a WTE plant with internally cooled test probes (450 • C) of a steel tube (St 37.8/1.0345) as substrate material, coated with Inconel 625 as the bond-coat and yttria-stabilized zirconia (YSZ) as the top-coat, showed an improved corrosion resistance [13]. This material combination was placed in a WTE plant in a flue gas temperature range between 680 and 740 • C for 500 h (~21 days).…”

Corrosion in biomass combustion: A materials selection analysis and its interaction with corrosion mechanisms and mitigation strategies

“…In light of this challenging scenario, several authors have pursued efficient coatings to prevent the high temperature corrosion of metallic materials in biomass fueled boilers and waste incinerators [114][115][116]. Hearley et al [117] showed that coatings produced by the high velocity oxygen fuel (HVOF) thermal spray process form effective barrier against high temperature corrosion.…”

Prediction of biomass corrosiveness over different coatings in fluidized bed combustion

“…A large number of coating processes are available to provide surface protection [24]. Several authors have pursued efficient coatings to prevent the high-temperature corrosion of metallic materials in biomass fuelled boilers and waste incinerators [25][26][27].…”