Hot Corrosion and its Prevention in High Temperature Heavy Oil Firing Gas Turbines

摘要

Severe hot corrosion cases have been investigated for blades and vanes of heavy oil firing gas turbine applied with CoNiCrAlY coating and its preventive methods has been established through examination for corrosion contaminant sources as well as actual plant testing for new protective coatings. (1) The corrosion was a typical high temperature sulfidation caused by alkali sulfates and vanadium compounds such as Na_2SO_4, Na_2O-V_2O_5. (2) The source of alkali sulfates and vanadium compounds was impurities contained in fuel and combustion air, especially the combustion air had involved large quantities of alkaline metals in it. (3) The prevention method has been achieved by an installation of high efficiency air filter, control for impurities in fuel and application for new protective coatings such as CoCrAlYRe and CoCrAlY + Al (AlSi).