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HomeBiowas, materials for increased performance in sustainable fuel combustion
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The aim of the project was to identify suitable material as well as weld overlays and thermal spray coatings for service in high temperature combustion plants, i.e. waste and biomass incineration and a cement kiln plant. The project combines investigation in the laboratory on fundamentals of oxide scale breakdown and the effect of preoxidation as well as laboratory exposures in simulated combustion environments and in-plant exposures in combustion plants.The fundamental investigations have shown that preoxidation of pure metals (Fe, Ni, Cr) and alloys is beneficial if the metal forms an oxide different from iron oxide. Iron oxide, formed on iron, is easily penetrated by chlorine, thereby initiating the mechanism of 'active oxidation'. Nickel, which is preoxidised in S02-containing gases, is also not protective, because NiS04 is formed, which is converted to NiCl2 upon exposure to HCl-containing gas. HCl-induced high temperature corrosion under thermal cycling conditions has been studied for iron/carbon steel, nickel and chromium together with two austenitic steels (304 and 310). Experiments were conducted with 14 cycles at 700 °C and with 49 cycles at 400 °C. The hot dwell time was 20 hours and cold dwell time approximately 4 hours. Both as-ground and materials preoxidised at either 400 °C or 700 °C were exposed. A large difference in growth rate kinetics was seen when experiments at 400 °C and 700 °C were compared. At 700 °C, iron and carbon steel had a gross mass change up to around 400 times higher than the austenitic 310 steel. However, at 400 °C the difference was only 5 to 10 times higher. With almost no exceptions, materials preoxidised at 400 °C exhibited the lowest corrosion rate and a better oxide adhesion. Preoxidation at 700 °C had a similar beneficial effect in testing at 400 °C, but no obvious positive impact at 700 °C.The plant exposures have shown that weld overlays of alloy 625 exhibit promising behaviour in a number of plants, i.e. under strong sufidising and chloridising conditions, and in the temperature ranges chosen. It is also immediately clear that all cast austenitic stainless steel grades exhibit intergranular attack by sulphur and/or chlorine. The behaviour of the thermal spray coating implies that the Ni-FeCrSiCe is the most promising solution. Preoxidation has some effect, as shown in the exposures of preoxidised tubes and rings in the Schweinfurt plant. It was shown by in-plant exposure that preoxidising of AC 66 reduces corrosion by a factor of about 20 %.
- Published:
- Corporate author(s): Directorate-General for Research and Innovation (European Commission)
- Personal author(s): Vodegel, S ; Asteman, H ; Spiegel, M
- Themes: Basic metals industry, steel industry , Industrial research and development
- Subject: biomass , chemical process , furnace , industrial research , materials technology , research method , resistance of materials , steel , testing
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| ISSN 1018-5593 | ISBN 978-92-79-11555-4 | DOI 10.2777/47060 | Catalogue number KI-NA-23868-EN-S |
- Released on EU publications website:
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