Materials degradation mechanisms in coal-fired boilers

The environmentally-induced degradation of materials operating at elevated temperatures in fossil-fired boilers may prove to be the most formidable obstacle standing in the path of the successful implementation of higher efficiency power generation systems. Corrosion and oxidation mechanisms are thermally activated processes, and the increased operating temperatures required to attain higher efficiencies in these power generation systems will limit the application of many materials that find extensive use in current equipment. Three of the major modes of materials degradation that are active in the existing fleet of coal-fired boilers in the US include: (1) accelerated sulfidation of waterwall tubing as a result of modified fuel combustion processes; (2) steam side oxidation; and (3) coal-ash corrosion. In this paper the current understanding of these corrosion phenomena will be reviewed and guidelines for future research approach will be outlined.