Thermodynamic Phase Stability Diagrams for the Analysis of Corrosion Reactions in Coal Gasification/Combustion Atmospheres. Interim Report

摘要

An improved understanding of corrosion chemistry in complex environments is needed for the effective use of metals and alloys in coal gasification/combustion systems. High-temperature corrosion reactions can be analyzed effectively if considered first from a thermodynamic equilibrium point of view. The equilibriam pressure of sulfur, oxygen, nitrogen and carbon in the gas will determine which condensed phases can stand in equilibrium with the gas. Reaction paths can be charted to determine how other phases can exist beneath the surface scale. The use of thermodynamic phase-stability diagrams for this purpose is discussed. The diagrams show which phases can exist at a given temperature for a given element (Fe, Ni, Co, etc.) in a mixture of two different oxidants (C, O, S, and N). The derivation and use of these diagrams to interpret behavior in coal gasification/combustion atmospheres is discussed. Diagrams for Fe, Ni, Co, Cr, Al, and Mn in S--O, C--O, N--O, C--S, C--N, and S--N mixtures at 894, 1144, and 1366 K (1150, 1600, 2000 exp 0 F) are presented in the report. Thermodynamic data used to derive the diagrams are also given. (ERA citation 03:025626)