Corrosion Mechanisms and Failure Cases in Waste Incineration Plants

Abstract

The paper presents results of deposit and failure case analysis from boiler tubes of waste fired plants and also results of laboratory experiments on steels and nickel-based alloys. The analysis of the deposits and failure cases strongly indicates enhanced corrosion of boiler tubes in waste fired plants in the presence of deposits, containing significant amounts of Zn- and Pb-rich low melting eutectic mixtures of chlorides and sulfates. In order to study corrosion mechanisms thermogravimetric experiments were conducted on 2.25Cr-1Mo steel in the presence of a molten KCl-ZnCl 2 eutectic. The results confirm the observation that enhanced corrosion does occur even at low temperatures of 250 °C. Additionally exposure tests were carried out beneath a CaSO 4 -K 2 SO 4 -Na 2 SO 4 -PbSO 4 -ZnSO 4 -salt mixture at 600 °C in N 2 -5 vol.% O 2 and enhanced corrosion occurs in the presence of the molten salt. The corrosion process is,hot corrosion `by basic fluxing of the oxide scales. The analysis of the failure cases and also the results of the experiments emphazise the predominant role of molten chlorides and sulfates in the corrosion of boiler tubes from waste incineration plants.