Abstract
Background: The problems with water wall corrosion have been accelerating over the last years. There are a number of reasons for this. Originally mild steels were successfully used in power plant water walls. The magnetite layer that forms at the fire side of the tubes when the boiler is taken into operation protected from corrosion attack. The fuels at that time (oil, coal, gas) were not able to break down the magnetite by corrosion. In addition, there were no restrictions for pollutions and for the combustion itself that could contribute to corrosion attack. The usage of fossil fuels has decreased substantially over the last 25 years, not least by environmental reasons. As a replacement a number of different kinds of bio mass fuels are used. These are typically more or less corrosive and the magnetite layers are attacked. The corrosion is often supported by reducing conditions as a result of the restrictions of the NO{sub x}-pollution. Also the waste fuelled boilers have huge corrosion problems. This has been the case for the last 25 years but nowadays the number of such plants is so much higher and the service data have been turned up. Corrosion protection of the water wall
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Citation Formats
Storesund, Jan, Elger, Ragna, Nordling, Magnus, and Viklund, Peter.
Countermeasures to corrosion on water walls. Part 2; Aatgaerder mot eldstadskorrosion paa panntuber. Etapp 2.
Sweden: N. p.,
2011.
Web.
Storesund, Jan, Elger, Ragna, Nordling, Magnus, & Viklund, Peter.
Countermeasures to corrosion on water walls. Part 2; Aatgaerder mot eldstadskorrosion paa panntuber. Etapp 2.
Sweden.
Storesund, Jan, Elger, Ragna, Nordling, Magnus, and Viklund, Peter.
2011.
"Countermeasures to corrosion on water walls. Part 2; Aatgaerder mot eldstadskorrosion paa panntuber. Etapp 2."
Sweden.
@misc{etde_1010824,
title = {Countermeasures to corrosion on water walls. Part 2; Aatgaerder mot eldstadskorrosion paa panntuber. Etapp 2}
author = {Storesund, Jan, Elger, Ragna, Nordling, Magnus, and Viklund, Peter}
abstractNote = {Background: The problems with water wall corrosion have been accelerating over the last years. There are a number of reasons for this. Originally mild steels were successfully used in power plant water walls. The magnetite layer that forms at the fire side of the tubes when the boiler is taken into operation protected from corrosion attack. The fuels at that time (oil, coal, gas) were not able to break down the magnetite by corrosion. In addition, there were no restrictions for pollutions and for the combustion itself that could contribute to corrosion attack. The usage of fossil fuels has decreased substantially over the last 25 years, not least by environmental reasons. As a replacement a number of different kinds of bio mass fuels are used. These are typically more or less corrosive and the magnetite layers are attacked. The corrosion is often supported by reducing conditions as a result of the restrictions of the NO{sub x}-pollution. Also the waste fuelled boilers have huge corrosion problems. This has been the case for the last 25 years but nowadays the number of such plants is so much higher and the service data have been turned up. Corrosion protection of the water wall tubes started to be successful in the beginning of the seventies by the introduction of the composite tube. Such tubes are fabricated by mild steel or a low alloy core and corrosion resistant austenite steel or nickel base as an about 2 mm thick corrosion protective coating. Weld cladding of the water wall tubes was introduced in the 1980's as a significantly cheaper alternative to the composite tubes. Thermal spraying and refractory protection are other methods. These corrosion protection methods have not always been effective. For example, depending on incorrect materials selection, incorrect performance and incorrect method selection for the current corrosion or erosion attack. Therefore, there is a need for increased knowledge of which protection method and material that will work economically for a given situation. In the first phase of the present project a literature survey concerning water wall corrosion protection methods was carried out [1]. Advantages, disadvantages and possibilities by the use of refractories, composite tubes, thermal spraying, hybrid coatings and weld cladding were investigated. An experience survey of problems with and protection of, water wall corrosion in Swedish plants was conducted as well. In an experimental part of the project six different weld clad materials were tested in water walls of five different boilers, representing different types of operation and fuel data. The test materials consisted of some conventional and newly developed weld clads for high temperature corrosion. These trials gave many interesting results but the exposure time was only one year of operation. A second phase of the project has now been carried out. In this study the test materials has been service exposed for another year. In addition, the literature and the experience surveys have been updated. Literature survey: There are some recent developments of water wall corrosion protection methods. One way is to flame spray relatively thick layers onto water wall sections. Then these sections were heat treated by induction heating such as the spray layers sintered see Figure 0.1 below. The sinter material consisted of 15 % Cr, 4,3 % Si, 3.1 % B and 2,5% Mo which gave very high hardness, HV 815. Three years service exposure of test panels gave no significant corrosion at all whereas carbon steel tubes exposed at the same time corroded 1.5 mm. In addition, the output of the boiler increased as a result of flame spray + sintering method. The reason is that refractory, with lower heat transfer properties, otherwise should be the solution for the water wall corrosion}
place = {Sweden}
year = {2011}
month = {Jan}
}
title = {Countermeasures to corrosion on water walls. Part 2; Aatgaerder mot eldstadskorrosion paa panntuber. Etapp 2}
author = {Storesund, Jan, Elger, Ragna, Nordling, Magnus, and Viklund, Peter}
abstractNote = {Background: The problems with water wall corrosion have been accelerating over the last years. There are a number of reasons for this. Originally mild steels were successfully used in power plant water walls. The magnetite layer that forms at the fire side of the tubes when the boiler is taken into operation protected from corrosion attack. The fuels at that time (oil, coal, gas) were not able to break down the magnetite by corrosion. In addition, there were no restrictions for pollutions and for the combustion itself that could contribute to corrosion attack. The usage of fossil fuels has decreased substantially over the last 25 years, not least by environmental reasons. As a replacement a number of different kinds of bio mass fuels are used. These are typically more or less corrosive and the magnetite layers are attacked. The corrosion is often supported by reducing conditions as a result of the restrictions of the NO{sub x}-pollution. Also the waste fuelled boilers have huge corrosion problems. This has been the case for the last 25 years but nowadays the number of such plants is so much higher and the service data have been turned up. Corrosion protection of the water wall tubes started to be successful in the beginning of the seventies by the introduction of the composite tube. Such tubes are fabricated by mild steel or a low alloy core and corrosion resistant austenite steel or nickel base as an about 2 mm thick corrosion protective coating. Weld cladding of the water wall tubes was introduced in the 1980's as a significantly cheaper alternative to the composite tubes. Thermal spraying and refractory protection are other methods. These corrosion protection methods have not always been effective. For example, depending on incorrect materials selection, incorrect performance and incorrect method selection for the current corrosion or erosion attack. Therefore, there is a need for increased knowledge of which protection method and material that will work economically for a given situation. In the first phase of the present project a literature survey concerning water wall corrosion protection methods was carried out [1]. Advantages, disadvantages and possibilities by the use of refractories, composite tubes, thermal spraying, hybrid coatings and weld cladding were investigated. An experience survey of problems with and protection of, water wall corrosion in Swedish plants was conducted as well. In an experimental part of the project six different weld clad materials were tested in water walls of five different boilers, representing different types of operation and fuel data. The test materials consisted of some conventional and newly developed weld clads for high temperature corrosion. These trials gave many interesting results but the exposure time was only one year of operation. A second phase of the project has now been carried out. In this study the test materials has been service exposed for another year. In addition, the literature and the experience surveys have been updated. Literature survey: There are some recent developments of water wall corrosion protection methods. One way is to flame spray relatively thick layers onto water wall sections. Then these sections were heat treated by induction heating such as the spray layers sintered see Figure 0.1 below. The sinter material consisted of 15 % Cr, 4,3 % Si, 3.1 % B and 2,5% Mo which gave very high hardness, HV 815. Three years service exposure of test panels gave no significant corrosion at all whereas carbon steel tubes exposed at the same time corroded 1.5 mm. In addition, the output of the boiler increased as a result of flame spray + sintering method. The reason is that refractory, with lower heat transfer properties, otherwise should be the solution for the water wall corrosion}
place = {Sweden}
year = {2011}
month = {Jan}
}