Waterwall Corrosion in Coal-Fired Boilers a New Culprit: FeS

Abstract

Abstract Most laboratory corrosion tests simulating waterwall corrosion in coal-fired boilers indicate corrosion rates of carbon and low alloy steels well below those recently found in boilers retrofitted with staged low NOx burner systems, especially those found in supercritical boilers. In this paper we studied the effect of boiler deposits on waterwall corrosion. It was found that FeS rich deposits can increase corrosion rates up to tenfold, under conditions in which iron sulfide can decompose to corrosive gas species. This generally occurs under oxidizing, mildly reducing or alternately oxidizing and reducing conditions. The actual presence of reduced sulfur species was confirmed in separate tests.