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High-temperature Corrosion Resistance of Alumina Refractories to Lignite Ash Slags.
Pahlman-JE; Anderson-CF; Khalafalla-SE
MISSING :20 pages
The Bureau of Mines is conducting research to determine the resistance of alumina refractories to corrosion by alkali-containing slags that could result from burning of the abundant western lignites in metallurgical operations. Static corrosion tests were performed at 1,000 deg. to 1,350 deg. C and dynamic tests were performed at 1,400 deg. to 1,600 deg. C to investigate the stability of refractory specimens in slag environments. In general, the degree of refractory attack increased with decreasing alumina content in the refractory and with increasing alkali content of the lignite ash. The parabolic kinetics observed in static tests suggested that a reaction product layer is formed through which ionic diffusion must occur to sustain the reaction with the refractory material. The linear kinetics observed in dynamic tests in high-viscosity slags indicated a shearing of the reaction product layer by viscous slags. Two 99-percent-alumina refractories and two 90-percent alumina refractories formed an expanded protective layer with the more viscous slags but not with the less viscous slags. Corrosion of 90-percent-alumina refractories increased exponentially with temperature. In refractories with the same nominal alumina content, those that contain a combination of a-al2o3 and mullite (3al2o3.2Sio2) have better corrosion resistance than those containing a combination of a-al2o3 cristobalite (sio2 mineral), and mullite. In alkali environments (1,300 deg to 1,400 deg c), 90- to 99-percent-alumina refractories are recommended for use as furnace linings.
IH; Report of Investigation;
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division