During the past 3 decades, all solution models that were used to predict thermodynamic properties of a multicomponent system from binaries improperly assumed that the selected binary compositions in a model are independent of the practical system to be treated. This assumption causes problems both in symmetrical and asymmetrical models. In this article, a new solution model has been suggested, which gets rid of this traditional way and assumes that the selected binary compositions should be closely related to the system considered. After introducing a new concept, the ''similarity coefficient,'' the relation between the selected binary compositions and the composition of the multicomponent system is established and a new model is generated. This new generation model is more reasonable in theoretical considerations, more reliable in practical use, and more realistic in computerization for estimating thermodynamic properties and calculating phase diagrams in a multicomponent system.

No abstract

The powder of hematite sample was isothermally reduced with hydrogen-water vapor gas mixture at 1023K-1273K. The results indicated that the overall reduction process of hematite could be separated into three stages (Fe2O3-Fe3O4-FeO-Fe) to respectively study. At 1023K, the average reaction rate dropped by 53.6% in the stage 1 when the water vapor content of gas reactant rose from 0% to 50%, and it decreased by about 77.2% in the stage 2. However, in the stage 3, when the water vapor content only increased from 0% to 20%, it decreased by about 78.1%. Besides, the average reaction rate had a roughly negative linear relationship with the water vapor content, and the results further shown that the effect of water vapor on the reduction reaction increased with increasing reaction temperature at all stages of the reduction reaction. The microstructure of reduction products showed that it still had some holes, which the channel for hydrogen diffusion was not seriously blocked. In order to further clarify the influence of water vapor in the reduction stage, different models were considered, and the range of apparent activation energy of different stages obtained by model fitting was about 20-70 kJ/mol, which also confirmed the absence of solid-state diffusion phenomenon.