Fireside Corrosion of Superheater Materials in Coal/Biomass Co-fired Advanced Power Plants

A series of laboratory-based fireside corrosion exposures were conducted to assess the effect of such conditions on superheater/reheater materials at higher than conventional metal temperatures. Controlled atmosphere furnaces combined with the deposit recoat test method were used to generate the exposure conditions; the gaseous environment simulated that anticipated from air-firing 20 wt% cereal co-product mixed with a UK coal. The exposures were carried out at 600, 650 and 700 A degrees C with four candidate materials: T92, HR3C and 347HFG steels; nickel-based alloy 625. After the exposures, the samples were examined by SEM/EDX to characterize the damage. Pre- and post-exposure dimensional metrology were used to quantify the metal damage in terms of metal loss distributions. For the austenitic steels, the combined deposit/gas/temperature exposure conditions enabled quantification of the characteristic 'bell-shaped' curves (of damage as a function of temperature) for fireside corrosion.