Initial corrosion attack of 304L and T22 in 2 MW biomass gasifier: a microstructural investigation

Abstract

The work investigates the initial corrosion attack on a low alloyed steel and a stainless steel in a 2 MW test gasifier. The gasifier environment generates homogenous deposits that consist mainly of carbon containing species, potassium sulphate, potassium chloride and zinc sulphide. The stainless steel exhibits better corrosion resistance compared to the low alloyed steel and the analysis indicates a protective thin scale covering parts of the surface after 4 h exposure. However, in some areas the oxide scale has lost its protective properties and thicker oxide scales are seen. The thick oxide islands consist of an inward growing Fe,Cr,Ni oxide and an outward growing iron oxide. The low alloyed steel shows a more homogenous and faster initial corrosion attack. The thick scales exhibit a sharp straight line in the middle of the scale that separates the bottom spinel oxide from the outer iron rich parts of the scale. It is considered that this flat interface corresponds to the original sample surface.

Keywords:

• Biomass gasification
• Syngas coolers
• Corrosion
• Stainless steel

Acknowledgements

This project was financed by Chalmers Area of Advance Energy. The work was carried out within the High Temperature Corrosion Centre (HTC) together with Energy Conversion, both located at Chalmers University of Technology. The operation of the Chalmers gasifier from Akademiska Hus, Göteborg Energi AB, Metso Power AB, the Swedish Energy Agency, and the Swedish Gasification Center is acknowledged.