Boiler tube failures in municipal waste-to-energy plants

Abstract

Waste-to-energy plants experienced increased boiler tube failures when the design changed from waste-heat boilers to radiant furnace waterwalls using superheat. Fireside attack by chlorine and sulfur compounds in refuse combustion products caused many forced outages in early European plants operating at high steam temperatures and pressures. Despite conservative steam conditions in the first US plants, failures occurred. As steam temperatures increased, corrosion problems multiplied. The problems have been alleviated by covering the waterwalls with either refractory or weld overlays of nickel-based alloys and using high nickel-chromium alloys for superheater tubes. Changes in furnace design to provide uniform combustion and avoid reducing conditions in the waterwall zone and to lower the gas temperature in the superheater also have helped minimize corrosion.