Geometrical Construction of Auxiliary Axes in an Ellingham Diagram

Abstract:

To facilitate the assessment of the oxide stability in H₂-H₂O or CO-CO₂ atmospheres, auxiliary axes are constructed in the Ellingham diagram. Based on A. Ghosh’s approach, the geometrical interpretation of the diagram is proposed for the reaction 2X + O₂ = 2Y, where X and Y could be originated from H₂ and H₂O or CO and CO₂. Two cases are considered when oxygen partial pressures are lower and higher than one bar. By a geometrical method, it is proved that with an appropriate set-up of values relating to the auxiliary axes, the axes representing the ratio between the equilibrium partial pressure of hydrogen and that of water vapour, as well as the ratio between the equilibrium partial pressure of carbon monoxide and that of carbon dioxide, can be constructed. The geometrical method on the construction of axes using thermodynamic derivation is explained in the paper.

• Periodical: Key Engineering Materials (Volume 856)
• Pages: 1-7
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.856.1
• Online since: August 2020
• Authors: Thamrongsin Siripongsakul*, Panya Wiman, Phichai Saranyachot, Somrerk Chandra-ambhorn
• Keywords: Carbon Dioxide, Ellingham Diagram, Patial Pressure, Water Vapour

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