Combustion Turbine Deposition Observations From Residual and Simulated Residual Oil Studies

Abstract

Burning residual oil in utility combustion turbines and the consequent deposition on blades and vanes may adversely affect reliability and operation. Corrosion and deposition data for combustion turbine materials have been obtained through dynamic testing in pressurized passages. The deposition produced by the 1900°F (1038°C) combustion gases from a simulated and a real residual oil on cooled Udimet 500 surfaces is described. Higher deposition rates for the doped fuel than for the real residual oil raised questions of whether true simulation with this approach can be achieved. Particles 4–8 μm in diameter predominated in the gas stream, with some fraction in the 0.1–12 μm range. Deposition rates seemed to be influenced by thermophoretic delivery of small molten particles, tentatively identified as magnesium pyro and metavanadates and free vanadium pentoxide, which may act to bond the larger solid particles arriving by inertial impaction to turbine surfaces. Estimated maintenance intervals for current utility turbines operating with washed and treated residual oil agreed well with field experience.