Coal Ash Corrosion in a Reheater of an Ultra-supercritical Power Plant

摘要

Thirty-one thousand feet of HR3C were exposed for 45,004 hours in the reheater of TVA's Gallatin unit 2 without any forced outages being caused by corrosion-induced wastage. Additionally, samples of 304, 347, 800H, NF709, HR3C, CR30A, and chromized T22 were exposed for the same 45,004 hours at temperatures from 521 to 685°C (970 to 1265℉), which covers the expected tube-metal temperatures for an ultra-supercritical steam plant. The active corrosion mechanism was found to be erosion corrosion with the corrosion component from potassium-iron-trisulfate. Additionally, the location in the boiler was found to be very important, and in some areas, this variable overshadowed the effect of temperature and alloy content. The results of this program provide corrosion data to select superheater and reheater alloys for ultra-supercritical power plants.