OCR Text |
Show calcium. Finally, another study (Sims 1978) found that potassium, in combination with sodium, was more corrosive than sodium alone. In a parallel study, Clark (1980) used the burner rig to investigate the deposition of SRC-II fuel oil. The deposits observed were rich in zinc, copper, and iron. In the combustion of SRC wash solvent, DeCorso, et al. (1981) noted the predominance of calcium-rich sulfates and phosphates in the deposits. They further noted that Na2S04 could be a condensed species but that the deposit morphology was suggestive of particulate accretion with no evidence of a frozen liquid phase. Particle Size Effects: The behavior of inorganic contaminants in the combustion gases and their deposition process have been described as a function of particle size. Rosner et al., (1981, 1982) and Srivastaria and Rosner (1979) have considered both vapor and particle deposition in their Chemically Frozen Boundary Layer theory. They state that in vapor deposition, the temperature is high enough to thermodynamically preclude the existence of any condensed inorganic compunds, thus condensates may form only below the dew point. The mechanism of mass transport at surface temperatures below the dew point temperature will be vapor diffusion across the combustion product boundar layer. In particle deposition, however, the uncooled gases may already be below the dew point, thus condensates are present as particulates at the combustor exit. The formation of a condensate aerosol, either in the mainstream or within the thermal boundary layer near cooler surfaces, influences the deposition rate due to the alteration of diffusivities from their vapor values and inertial 1.5.19 |