Fireside corrosion of superheater alloys in ultra-supercritical coal-fired boilers

This book focuses on the influence the fireside environment poses on selected austenitic and nickel-based alloys dedicated i.a. for construction of superheaters and reheaters in high efficiency pulverized coal boilers. Within various studies six alloys were exposed in three power plants, one pilot scale combustion test rig and simultaneously tested in technical and laboratory conditions at metal temperatures in the range 580 - 750°C in order to determine their performance in different coal combustion conditions. The corrosion behaviour was estimated using various analytical techniques. Subsequently corrosion rate was calculated with respect to determined corrosion product and thereof deflected metal loss observed at varying exposure times and environments. Fireside corrosion was studied having in focus the synergy effect of combustion gas atmosphere, real fly ash deposits and the alloy itself. Influence of the deposit was studied carefully with respect to corrosion and finally the synergy effect of metal-gas and metal-gas-deposit was discussed supported by the outcomes of the high temperature corrosion tests performed under mono-deposits - selected mineral phases typical for coal combustion.