Introducing mechanistic kinetics to the Lagrangian Gibbs energy calculation

Pertti Koukkari (Corresponding Author), Risto Pajarre

    Research output: Contribution to journalArticleScientificpeer-review

    63 Citations (Scopus)


    The Gibbs free energy minimum is usually calculated with the method of Lagrangian multipliers with the mass balance conditions as the necessary subsidiary conditions. Solution of the partial derivatives of the Lagrangian function provides the equilibrium condition of zero affinity for all stoichiometric equilibrium reactions in the multi-phase system. By extension of the stoichiometric matrix, reaction rate constraints can be included in the Gibbsian calculation. Zero affinity remains as the condition for equilibrium reactions, while kinetic reactions receive a non-zero affinity value, defined by an additional Lagrange multiplier. This can be algorithmically connected to a known reaction rate for each kinetically constrained species in the system. The presented method allows for several kinetically controlled reactions in the multi-phase Gibbs energy calculation.
    Original languageEnglish
    Pages (from-to)1189-1196
    Number of pages8
    JournalComputers and Chemical Engineering
    Issue number6-7
    Publication statusPublished - 2006
    MoE publication typeA1 Journal article-refereed


    • Gibbs energy minimization
    • Lagrange multipliers
    • kinetic constraints
    • reaction rate
    • process modeling


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