OCR Text |
Show sulfate as the major compound in most deposits. The fuel is the major source of both the sulfur and sodium. In addition, in marine environments, sea salt aerosols in the intake air; and in the air transport the aerosols from volcanic activities may also contribute to the sodium and sulfur intake (Stringer, 1977). In combustion studies, sodium chloride is seldom detected in the deposits. Thermodynamic analysis of DeCrescente and Bornstein (1968) indicates that sodium chloride in the presence of sulfur and in an oxidizing environment is virtually completely converted to sodium sulfate at high temperatures around 1000 C (1832 F). It was initially thought that the residence time of combustion gases would not be adequate to achieve the thermodynamic equilibrium, however, more recent studies (Kohl et al., 1979) of NaCl seeded flames indicate that the reaction rates are fast enough for equilibrium to be achieved in engine combustors. Studies using heavy distillate residual fuels have also identified vanadium as a deposit forming element. Vanadium, which is known to exist in the heavy fuels as prophyrin type compounds, upon combustion, forms vanadium pentoxide and vanadates. These compounds have low melting points and deposit on turbine blades in molten form. In addition to sodium and vanadium other trace elements like potassium, calcium, lead, zinc and nickel have also been identified in deposits from heavy residual fuels. Reported elemental analysis for deposits formed from combustion of coal-derived liquids is very limited. Clark (1980, 1981) studied the desposition characteristics of SRC-II fuel oil. The deposits were rich in zinc, copper and iron. In combustion of SRC wash solvent, DeCorso 1.5.15 |