A Simple Phase Equilibrium Approach To the Problem of Oil-Ash Corrosion

Abstract Many recent investigations of residual fuel oil-ash corrosion have utilized simulated ashes based upon mixtures of Na2SO4 and V2O5. Results of these various studies have not always been easily correlated. It was reasoned that a knowledge of the phase equilibrium relationships in the system Na2O-SO3-V2O5 might provide a reliable basis for the comparison and evaluation of such studies. Accordingly, a compatibility diagram was deduced for the system. Volatilization experiments and phase identification by microscopic and x-ray methods confirmed the essential validity of the diagram. When used as a background for the consideration of previous and current oil-ash corrosion research, the diagram was found to be consistent with most of the recorded findings. It has been found that Na2SO4 and V2O5 are not compatible with each other in either the crystalline or molten state. They react upon heating with evolution of SO3 to form NaVO3, as well as several complex vanadates, but not Na3VO4 or Na4V2O7. The com...