Review of factors affecting steam oxidation testing

Abstract

Thermal efficiency of current 600°C plant is typically around 45 –46%, this can be raised to over 50% by increasing the operating temperature to 650°C with future goals of 700 and 750°C Advanced Super Critical plant. This increase in operating conditions places increasingly higher demands on conventional materials both in terms of creep strength and corrosion. Recent experience within a five-year programme of collaborative work carried out under the auspices of the UK–US Memorandum of Understanding (MOU) and the associated Implementing Agreement for Fossil Energy Research and Technology Development, has shown that the generation of such data is not as straight forward as one might expect. It has been shown through extensive test programmes on the same materials that different results and alloy behaviour can be found, which are caused by relatively small differences in the test procedure.

In this paper, steam oxidation will be considered, with examples presented and discussed showing the variation in oxidation rates that can be found between different laboratories and even within controlled intercomparisons. The main experimental factors that are believed to affect the alloy behaviour will be introduced and examples presented to illustrate the effect on the oxidation rate and scale morphology.

Keywords:

• steam oxidation testing
• Advanced Super Critical plant
• alloy behaviour
• oxidation rate
• scale morphology