Osipov A.A., Ivanov K.D., Askhadullin R.Sh.
A.I. Leypunsky Institute for Physics and Power Engineering, Obninsk, Russia
This paper deals with the problem of dissociation of compounds in multicomponent systems. The theory of dissociation of compounds underlies all physicochemical processes, since the degree of dissociation of compounds is a measure of their strength or thermodynamic stability. In the theory of thermal dissociation of compounds, the transition of the components of a condensed compound to the gas phase is considered. The question arises of the applicability of such an approach to the consideration of processes occurring during the interaction of condensed compounds with other condensed phases. In particular, with regard to promising nuclear power plants (NPP) with a heavy liquid metal coolant (HLMC), the question of the interaction of oxide films with a liquid metal is relevant. In this paper, we have identified some of the difficulties of applying the classical theory to the problem of dissociation of compounds in multicomponent systems consisting of condensed phases, and outlines ways to overcome them. It is shown that the use of existing approaches is limited by the lack of data on the relationship of the isobaric-isothermal potential of the formation of compounds with their composition. A method for taking into account the influence of the composition of compounds on this parameter is proposed, based on an analysis of the available experimental data on stoichiometric compounds. Using the example of a three-component compound, we consider a system of basic and additional equations for the coupling of thermodynamic parameters describing the equilibrium state of the thermodynamic system during thermal dissociation of the compound. The conditions for obtaining solutions of this system are given. For the iron-oxygen two-component system, numerical calculations of the oxygen partial pressures as a function of temperature are performed and the model can be improved by using the assumption that the dissociation process of the compound is congruent. The main result of the work is a model of the equilibrium dissociation of compounds, built on the basis of solving a system of equations of conservation of mass, the laws of effective masses and the Gibbs-Duhem equations.
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