A Reaction Method for Estimating Gibbs Energy and Enthalpy of Formation of Complex Minerals
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INTRODUCTION
GIBBS free energy and enthalpy of formation are the basic information required to describe the thermodynamic behaviors of the reactions in metallurgical and chemical industries. For example, in the design of metallurgical engineering, Gibbs free energy is used to predict the direction of the chemical reactions of minerals, while enthalpy is used to identify the heat sink/source associated with chemical reactions. Experimental data for the standard enthalpy of formation, standard free energy of formation, and other thermodynamic properties are typically available for most of the simple minerals and common compounds.[1–3] However, this information is not available for many mineral compounds, in particular those with more complex structures. Due to the difficulty in direct calorimetric determination of such complex minerals, reliable thermodynamic data for most complex minerals are thus far not widely available in the literature. For example, hydrogarnet (3CaOÆAl2O3ÆxSiO2Æ2H2O) and sodium RUIBING LI is with the School of Materials & Metallurgy, Northeastern University, Shenyang 110819 China, and also with the Laboratory for Simulation and Modelling of Particulate Systems, School of Materials Science and Engineering, The University of New South Wales, Sydney, NSW 2052, Australia, and also with the Laboratory for Simulation and Modelling of Particulate Systems, Department of Chemical Engineering, Monash University, Clayton, Victoria, 3800, Australia. TINGAN ZHANG and YAN LIU are with the School of Materials & Metallurgy, Northeastern University Contact e-mails: [email protected], [email protected] SHIBO KUANG is with the Laboratory for Simulation and Modelling of Particulate Systems, School of Materials Science and Engineering, The University of New South Wales, and also with the Laboratory for Simulation and Modelling of Particulate Systems, Department of Chemical Engineering, Monash University. Contact e-mail: shibo. [email protected] Manuscript submitted July 14, 2016. Article published online January 19, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B
aluminosilicate hydrate (Na2OÆAl2O3ÆxSiO2Æ(6-2x)H2O) which are multi-oxide and series of minerals occurred in Bayer process,[4–7] and slags for pyrometallurgy which are of complex composition,[8–10] etc., some of the thermodynamic data of these minerals were not available. This situation can cause uncertainties in controlling reactions, heat transfer, and associated phenomena such as multiphase flows and mass transfer in the reactors involving complex minerals. Therefore, it is necessary to develop a viable method to estimate the thermodynamic properties of complex minerals, especially the widely used standard Gibbs free energy (DG0f ) and enthalpy (DH0f ) of formation. Various methods have been developed to estimate the free energy of formation of certain minerals. Among others, Tardy and Garrels in 1974 proposed a method of estimating the Gibbs energy of formation of layer silicates. In such an approach, the oxide and hydroxide components within the
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