High temperature corrosion leads especially in waste-to-energy-plants to massive problems. At prevalent temperatures around 400°C-600°C, corrosion in these plants is mainly chlorine induced. A local release of chlorine through sulfation reaction of solid alkali chlorides is mainly responsible for the supply of chlorine at metallic components like superheaters or boiler walls. This reaction requires an atmosphere containing SO2, H2O, O2 and releases HCl/Cl2.
Parameters relevant for the sulfation kinetics of chlorine containing particle deposits are the reaction temperatures, catalytic acting species and the gas atmosphere composition. The conversion rate is strongly dependent on the transformation of SO2 to SO3 and can be catalyzed by the presence of iron oxides, which are formed during the corrosion process.
In addition to the study of the sulfation reaction it is significant to characterize the metal loss due to corrosion reactions. The corrosive attack is influenced by various parameters like reaction temperature and amount of delivered chlorine. Even more important is the proportion of HCl to Cl2, which depends on the thermodynamic equilibrium and the presence of water in the gas atmosphere. In humid atmosphere HCl is favored, whereas water free gas composition will lead to Cl2 formation. The latter reveals a much higher corrosion potential to metallic components.
Principles of the reaction conditions in waste-to-energy-plants, especially at the superheater tubes, are investigated and laboratory experiments regarding the kinetics of sulfation reactions and the corresponding chlorine attack are evaluated.