A Mass Spectrometric Study of the Thermodynamic Properties of Oxide Melts

Information about vaporization processes and the thermodynamic properties of oxide melts is of importance for various fields of high-temperature technologies. The available data on the thermodynamic properties of binary borate, silicate, germanate, and phosphate melts studied by mass spectrometry have been compared in the framework of the acid–base concept. The reliability of experimental data is analyzed on the basis of a comparison between the results obtained by different mass spectrometric techniques and those determined by various methods of high-temperature chemistry, such as the electromotive force (emf) technique, high-temperature dissolution calorimetry, and the method of exchange equilibria in slags. Deviations of the chemical potentials for P₂O₅, B₂O₃, SiO₂, and GeO₂ from the ideal behavior as a function of the oxide modifier content in series of binary systems reflect the diversity of processes (dissociation, association, and polymerization) accompanying the vaporization of their components.     

Phase equilibria of mixtures containing CO2 and organic acids using the UMR-PRU model

The UMR-PRU model, which has been successfully tested in the past to the predictions of different type of phase equilibrium and thermodynamic properties in binary and multicomponent systems, is applied in this work to phase equilibria in mixtures containing CO₂ and organic acids. New interaction parameters are determined by fitting only binary vapor–liquid equilibrium data and then they are used to predict the vapor–liquid, solid–gas and solid–liquid–gas equilibria in CO₂/organic acid systems. Furthermore, the UMR-PRU model with the newly derived interaction parameters is applied to the prediction of the phase equilibrium in ternary mixtures consisting of CO₂, organic acids and water. Satisfactory results are obtained in all cases.     

Slag-resistant products made from stabilized ZrO2

Conclusions The resistance of zirconia refractories to the action of acid slags is determined by the interaction between the added stabilizer and the silica component of the slag and by the rate of formation of the corresponding silicates. Of those materials studied, the most resistant of the action of the more acid slags is ZrO₂ stabilized by Y₂O₃.The rate of wear of the articles made from stabilized zirconia under the action of the more basic of the melts we studied is determined by the diffusion of Ca²⁺ into the structure of ZrO₂ forming CaZrO₃ which leads to the articles becoming less dense. The interaction between the stabilized ZrO₂ and the basic industrial slag, moreover, is accompanied by the intense dissolution of the refractory in the slag as a result of the formation of low-melting melts at the slag-refractory interface.Thus, zirconia refractories have an excellent resistance to the action of an acid multicomponent slag and are intensively damaged by basic slags.Translated from Ogneupory, No. 3, pp. 54–57, March, 1979.     

Intrinsic differences in atomic ordering of calcium (alumino)silicate hydrates in conventional and alkali-activated cements

The atomic structures of calcium silicate hydrate (C–S–H) and calcium (–sodium) aluminosilicate hydrate (C–(N)–A–S–H) gels, and their presence in conventional and blended cement systems, have been the topic of significant debate over recent decades. Previous investigations have revealed that synthetic C–S–H gel is nanocrystalline and due to the chemical similarities between ordinary Portland cement (OPC)-based systems and low-CO₂ alkali-activated slags, researchers have inferred that the atomic ordering in alkali-activated slag is the same as in OPC–slag cements. Here, X-ray total scattering is used to determine the local bonding environment and nanostructure of C(–A)–S–H gels present in hydrated tricalcium silicate (C₃S), blended C₃S–slag and alkali-activated slag, revealing the large intrinsic differences in the extent of nanoscale ordering between C–S–H derived from C₃S and alkali-activated slag systems, which may have a significant influence on thermodynamic stability, and material properties at higher length scales, including long term durability of alkali-activated cements.     

Modeling aspirin and naproxen ternary solubility in supercritical CO2/alcohol with a new Peng–Robinson EOS plus association model

A new version of the Peng–Robinson equation of state (PR EOS) is developed through the use of Wertheim's thermodynamic perturbation theory of associating fluids and statistical associating fluid theory (SAFT). The new equation is characterized by two temperature-independent parameters, namely, association strength and association volume, which account for the association interactions between associating molecules. In this work, we employed the equation to model aspirin and naproxen solubility enhancement obtained in the ternary supercritical CO₂/alcohol systems, where the original PR EOS has resulted in large and negative binary interaction parameters between the polar solute and polar cosolvent. Calculated results show that the Peng–Robinson EOS plus association model gives better performance to correlate these ternary solubility data over the ranges of temperature, pressure and cosolvent concentration investigated than its conventional form that uses temperature-dependent parameters.     

A Study of the Acid–Base Properties of Melts in the Na2O–B2O3–SiO2System: I. Composition Joins with a Na2O Content of Less Than 20 mol %

Three composition joins in the Na₂O–B₂O₃–SiO₂system at constant Na₂O contents of 5, 10, and 15 mol % are studied by the high-temperature method of determining oxygen ion exponents pO for oxide melts. It is found that the basicity of melts increases in going from the binary sodium borate system to the sodium silicate system. The acid–base properties of ternary melts are simulated under the assumption that their basicity is determined by the interaction in pseudobinary systems. It is shown that the basicity of the studied melts is governed, to a large extent, by the formation of the Na₂O · B₂O₃· 2SiO₂ternary compound.     

Thermodynamic modeling and phase diagram prediction of salt lake brine systems. I. Aqueous Mg2+–Ca2+–Cl− binary and ternary systems

Salt lake brine is a complex salt-water system under natural environment. Although many models can express the thermodynamic properties and phase equilibrium of electrolyte aqueous solution, the multi-temperature characteristics and predictability are still the goals of model development. In this study, a comprehensive thermodynamic model system is re-established based on the eNRTL model and some improvements: (1) new expression of long-range electrostatic term with symmetrical reference state is proposed to handle the electrolyte solution covering entire concentration range; (2) the temperature dependence of the binary interaction parameters is formulated with a Gibbs Helmholtz expression containing three temperature coefficients, the liquid parameters, which associated with Gibbs energy, enthalpy, and heat capacity contribution; and (3) liquid parameters and solid species data are regressed from properties and solubility data at full temperature range. Together the activity coefficient model, property models and parameters of liquid and solid offer a comprehensive thermodynamic model system for the typical bittern of MgCl₂–CaCl₂–H₂O binary and ternary systems, and it shows excellent agreement with the literature data for the ternary and binary systems. The successful prediction of complete phase diagram of ternary system shows that the model has the ability to deal with high concentration and high non-ideality system, and the ability to extrapolate the temperature.     

Thermodynamic modeling of the BaO-SiO<Subscript>2</Subscript> and SrO-SiO<Subscript>2</Subscript> binary melts

The evaluation of the thermodynamic properties and the phase diagrams for the binary BaO-SiO₂ and SrO-SiO₂ systems is carried out using a structural model for silicate melts and glasses. This thermodynamic model is based on the assumption that an addition of metal oxides to silica results in the depolymerization of the silicon-oxygen network, with a characteristic free energy change. A least squares optimization program permits all available thermodynamic and phase diagram data to be optimized simultaneously. In this manner, data for the above binary systems have been analysed and represented with a small number of parameters. The resulting equations represent the thermodynamic and phase diagram data for the alkaline-earth oxide-silica systems within error limits for most of the experimental data. In particular, the measured limiting liquidus slope, at X _{SiO 2} = 1, is well reproduced.     

Estimating the density and molar volume of ferrite-based ternary molten slags by geometrical model

Ferrite-based slags are the basic systems in the pyrometallurgical production of copper, and the density and molar volume of these systems are of vital importance for optimizing the metallurgical process. However, due to the high melting points of melts and the expensive trial costs, experimental methods are inefficient to obtain all the data needed. As a result, a geometrical model has been applied to the estimation of density and molar volume of ferrite-based ternary slags. The calculated results agree well with experimental data in three ferrite-based ternary systems of Fe₂O₃–CaO–FeO, Fe₂O₃–BaO–FeO and Fe₂O₃–CaO–Cu₂O. The mean deviation of the predicted results by the present model is lower than those by various empirical models for corresponding systems. The application of the present will enrich the data of density and molar volume for more ternary melts.     

Viscosity of the binary systems containing trifluoroethanol,water and tetraethylene glycol dimethyl ether. Prediction of the ternary viscosity from binary data

Kinematic viscosities were measured over the entire range of composition and at atmospheric pressure for the binary systems trifluoroethanol (TFE)-H₂O, TFE-tetraethylene glycol dimethyl ether (TEGDME), and TEGDME-H₂O from 293.15 to 333.15 K. The data were fitted by the Stephan and Heckenbergber (1989) correlation, which accounts for the dependence on temperature and mixture composition. Methods for predicting ternary excess viscosities from excess viscosity data for the three binary mixtures involved are examined and tested for the system TFE-H₂O-TEGDME at 303.15 K by comparing predicted and experimental data. The empirical correlation of Colinet (1967) is shown to be the best for this system.     

Solid-liquid equilibria in concentrated aqueous salt solutions—systems with a common ion

A thermodynamic correlation is presented for solid-liquid equilibria in concentrated aqueous salt systems containing a common ion. It is assumed that no solid solutions are formed, although the solid phase can be a pure salt, a multiple salt or a hydrate. Predictions of solid-liquid equilibria in multicomponent systems are made using parameters calculated from solid-liquid equilibrium data for the constituent binary and ternary systems.Parameters are given for the prediction of solid-liquid equilibria in the aqueous system containing Na⁺, K⁺, Mg⁺⁺, NO^?₃, Cl^?, SO^--₄ from 0–50°C. These parameters correlate the available solid-liquid equilibrium data for ternary systems with an error in liquid-phase composition of less than 2 grams salt/100 grams H₂O. Errors are similar in the estimation of solid-liquid equilibria in four-component systems such as NaNO₃-NaC1-Na₂SO₄-H₂O.     

In Situ Observation of the Dissolution of SiO2 Particles in CaO–Al2O3–SiO2 Slags and Mathematical Analysis of its Dissolution Pattern

The dissolution of amorphous SiO₂ particles in CaO–Al₂O₃–SiO₂ slags was investigated at 1450°C by high‐temperature confocal scanning laser microscopy (HT‐CSLM) and thermodynamic/kinetic analyses. The SiO₂ particles used in this experimental study had a spherical form so that any rotation of the particle did not cause errors in the determination of the particle size during the dissolution. Moreover, a wide composition range of the slag could be chosen without forming any solid reaction layer which could distort the evaluation of the dissolution mechanism. The evolution of the diameter of the spherical SiO₂ particle was measured by image analysis of pictures obtained from the HT‐CSLM. It was found that the dissolution curve of the SiO₂ particle (size as a function of time) exhibited either a parabolic‐like curve or an S‐shaped curve depending on the slag composition. The patterns were compared with a well‐known shrinking core model (SCM), and it was shown that the SCM could not represent the dissolution behavior of the SiO₂ particle observed in this study. It was experimentally found that the shape of the dissolution curves varies as a function of the slag composition. The curve exhibited a parabolic‐like shape for low SiO₂‐containing slags and changed to an S‐type shape with increasing SiO₂ concentration in the slag. To elucidate the dissolution mechanism, a model based on approximations for the diffusion near the particle was proposed by modifying the previously available model [M. J. Whelan, Met. Sci. J., 3, 95–97 (1969)]. From the experimental data and the model calculations, the viscosity of the slag was shown to be the major factor affecting both dissolution rate and mechanism. Effective binary diffusion coefficients were estimated using the model and experimental data. Those were shown to be in the range of literature data.     

A local composition model for multicomponent liquid mixture shear viscosity

A local composition model for multicomponent, nonaqueous, liquid mixture shear viscosity has been developed and tested. Only binary equilibrium thermodynamic information is used in the model in addition to pure component data. No mixture shear viscosities and no adjustable parameters are required. Predictions based on this model were compared to experimental data obtained from the literature and in this laboratory, yielding an average absolute deviation of 1.1% for ln(ηV) for 47 binary and 0.8% for seven ternary systems.     

Resistance of blast furnace refractories to the action of aggressive reactants under conditions of an oxidizing gaseous atmosphere

Conclusions Investigations have been made of the resistance of ShPD-41, ShPD-39, and ShUD-37 chamotte refractories to the action of K₂CO₃, Fe₂O₃, blast furnace dust, and initial and final blast furnace slags under conditions of an oxidizing atmosphere. The investigation results showed that iron oxides and slag break down these refractories at 1400–1500°C. Dense ShPD-41 refractory is more resistant to the action of the reactants.The most resistant to the action of slags and iron oxides at 1400–1500°C are silicon carbide refractories with binders of silicon nitride and oxynitride.Translated from Ogneupory, No. 7/8, pp. 24–27, July–August, 1992.     

Investigation of slag-refractory interactions for the Ruhrstahl Heraeus (RH) vacuum degassing process in steelmaking

In order to determine the effect of slag composition during the RH process on refractory wear, magnesia–carbon and magnesia–chromite refractories were immersed for 10 min at 1600 °C in a ladle slag, two FeO-rich slags (20 and 40 wt% FeO) and two CaO–Al₂O₃ slags. Corrosion of magnesia–carbon refractory by the ladle and CaO–Al₂O₃ slags was limited as the refractory carbon phase efficiently prevented slag infiltration. Severe degradation was observed in contact with FeO-rich slags. FeO oxidized the carbon phase with formation of Fe droplets at the hot face. Regarding magnesia–chromite refractory, the corrosion mechanism consisted of severe slag infiltration, high temperature inactivation of the secondary chromite and primary chromite dissolution in the infiltrating slag. The FeO-rich slags seem to have generated more severe conditions as the infiltrating slag pushed apart the periclase grains, leading to severe refractory erosion. The degradation mechanisms are discussed by combining experimental results and thermodynamic calculations.     

Thermodynamics of supersaturated solutions: From ternary electrolyte+solute+H2O to binary solute+H2O systems

In our previous paper, a new experimental technique based on the potentiometric method was developed to obtain thermodynamic activity data (in form of activity ratio) particularly for ternary electrolyte+nonelectrolyte+H₂O solutions supersaturated with the nonelectrolyte. In this paper, a rigorous thermodynamic approach is proposed to derive activity data for binary nonelectrolyte+H₂O solutions in the supersaturated region, via cell potentials of an electrolyte tracer and solubility data of the nonelectrolyte. An analysis of thermodynamic consistency is presented to evaluate the reliability and accuracy of the measured data. A systematic experimental investigation of three ternary electrolyte+nonelectrolyte+H₂O and two binary nonelectrolyte+H₂O systems is reported in both under-saturated and supersaturated regions (up to a supersaturation level of approximately 27%). Interesting thermodynamic behaviors are observed and their significance is discussed, with the role of thermodynamics in exploration of crystallization phenomena highlighted.     

Multicomponent adsorption equilibria of highly non-ideal mixtures: The case of chloroaromatic mixtures on zeolite

The adsorption equilibrium behaviour of binary, ternary and quaternary vapour mixtures involving ortho- and para-chlorotoluene, toluene and chlorobenzene on zeolite Ca-X at atmospheric pressure and 230°C has been investigated. Since under these operating conditions the adsorbent surface is saturated and the adsorbed molecules interact strongly with each other, these systems exhibit significant deviations from ideal behaviour. A thermodynamic non-ideal adsorption equilibrium model is presented, which, based only on binary interaction parameters, allows for the prediction of multicomponent equilibrium data. The role of such a model in the simulation of the dynamic behaviour of fixed-bed separation columns is investigated. A surprisingly strong effect of the desorbent on the selectivity of the two isomers is found.