Abstract
Based on the premise that liquid fuel-ash components are associated with the “catastrophic” attack on refractory alloys, a theoretical study has been made of mixtures of vanadium pentoxide and sodium sulfate with various metallic oxides and sulfates. The thermal stabilities of the sulfates were then investigated. It was concluded that the oxides of calcium, magnesium, and aluminum should be effective if they could be preserved in the oxide form. However, it was shown that the sulfate would in general be the stable form, particularly at gas turbine operating pressures. Such sulfates are not effective additives and may, in fact, be deposit forming. The additive with the most promise was found to be an aluminum compound. Its sulfate, even if initially formed, should revert almost entirely to the oxide at 800 C for atmospheric conditions and 920 C at five atmospheres. Some of these conclusions have been confirmed by full scale tests on turbines, but additional laboratory testing and actual operation are necessary to verify them completely. More extensive and accurate ther-mochemical data would contribute to the validity of the calculated results. 3.5.9
