Protective oxides in coal-fired combined cycle power systems

In most industrial processes operating at elevated temperatures, protective oxide layers perform a vital duty in protecting the underlying metallic alloys from process gases. Coal-fired combined cycle power generation systems present a number of process conditions in which the properties of the protective oxide layers are particularly important. This paper discusses two of these particular conditions: (i) 'erosion/corrosion' of in-bed heat exchanger tubing and (ii) thermal cycling of hot gas path components. For both these situations, the desirable properties of protective scales are outlined. The behaviour of scales in practice are highlighted.