Abstract
Conceptual designs of advanced combustion systems that utilize coal as a feedstock require high-temperature furnaces and heat transfer surfaces that can operate at temperatures much higher than those prevalent in current coed-fired power plants. The combination of elevated temperatures and hostile combustion environments requires the development and application of advanced ceramic materials in these designs. The objectives of the present program are to evaluate the (a) chemistry of gaseous and condensed products that arise during combustion of coal; (b) corrosion behavior of candidate materials in air, slag, and salt environments for application in the combustion environments; and (c) residual mechanical properties of the materials after corrosion. The program emphasizes temperatures in the range of 1000-1400°C for ceramic materials and 600-1000°C for metallic alloys. Coal/ash chemistries developed on the basis of thermodynamic/kinetic calculations, together with slags from actual combustors, are used in the program. The materials being evaluated include monolithic silicon carbide from several sources: silicon nitride, silicon carbide in alumina composites, silicon carbide fibers in a silicon carbide-matrix composite, and some advanced nickel-base alloys. The paper presents results from an ongoing program on corrosion performance of candidate ceramic materials exposed to air, salt, and slag environments and their effect on flexural strength and energy absorbed during fracture of these materials.
