The use of thermodynamic modeling to examine alkali recirculation in the iron blast furnace

It is widely recognized that alkali metals, such as, potassium and sodium can cause operational problems in the iron blast furnace. These elements can influence properties, such as, the softening and melting of ores, formation of scaffolds, coke properties, and refractory life. It has been established that recirculation of these elements occurs within the furnace. In the lower furnace vaporization occurs in the high temperature hearth and bosch regions, and condensation occurs in the upper furnace below or in the cohesive zone. For these reasons the input of alkalis into the furnace is strictly controlled. Optimized thermodynamic databases describing slags in the system Al2O3-CaO-FeO-Fe2O3-Na2O-K2O-MgO-SiO2 have been developed and, combined with the computer software FactSage; these databases have been used to predict the possible behaviour of alkalis in the blast furnace and to examine the effects of changing process variables on reactor performance. To demonstrate this approach to process modeling the furnace is considered as a two-stage equilibrium reaction system and the results of initial analysis are reported

High-temperature experimental and thermodynamic modelling research on the pyrometallurgical processing of copper

Uncertainty in the metal price and competition between producers mean that the daily operation of a smelter needs to target high recovery of valuable elements at low operating cost. Options for the improvement of the plant operation can be examined and decision making can be informed based on accurate information from laboratory experimentation coupled with predictions using advanced thermodynamic models. Integrated high-temperature experimental and thermodynamic modelling research on phase equilibria and thermodynamics of copper-containing systems have been undertaken at the Pyrometallurgy Innovation Centre (PYROSEARCH). The experimental phase equilibria studies involve high-temperature equilibration, rapid quenching and direct measurement of phase compositions using electron probe X-ray microanalysis (EPMA). The thermodynamic modelling deals with the development of accurate thermodynamic database built through critical evaluation of experimental data, selection of solution models, and optimization of models parameters. The database covers the Al-Ca-Cu-Fe-Mg-O-S-Si chemical system. The gas, slag, matte, liquid and solid metal phases, spinel solid solution as well as numerous solid oxide and sulphide phases are included. The database works within the FactSage software environment. Examples of phase equilibria data and thermodynamic models of selected systems, as well as possible implementation of the research outcomes to selected copper making processes are presented

Integrated experimental and modelling research methodology for phase equilibria, thermodynamics and viscosities of metallurgical slags

Coupled experimental and modelling studies are combined into an integrated research program on phase equilibria, thermodynamics and viscosities of the metallurgical slag systems. Key issues derived from experiences in continuing development and application of both experimental and thermodynamic modelling research are outlined. Particular emphasis is given to the details of the research methodologies, analysis of reasons for uncertainties and the ways to continuously improve the accuracy of both studies. The ways how the advanced research tools can be implemented into industrial operations are presented

Thermodynamic modelling of the "cu2O"-SiO2, "cu2O"-CaO, and "cu2O"-CaO-SiO 2 systems in equilibrium with metallic copper

Phase equilibrium and thermodynamic experimental data in the Cu 2O - SiO2, Cu2O - CaO, and Cu2O - CaO - SiO2 systems in equilibrium with metallic copper have been critically reviewed. The Modified Quasichemical and Bragg-Williams models in the FactSage computer package were used to describe the Gibbs energy of the molten slag phase as a function of composition and temperature. The available data have been used to optimize simultaneously a set of parameters in thermodynamic model equations for the Gibbs energy of liquid slag. The present thermodynamic optimization was carried out as part of the development of a thermodynamic database of copper-containing slag systems

Experimental phase equilibria studies of the PbO–SiO2 system

Phase equilibria of the PbO–SiO system have been established for a wide range of compositions: (i) liquid in equilibrium with silica polymorphs (quartz, tridymite, and cristobalite) between 740°C and 1580°C, at 60-90 mol% SiO; (ii) with lead silicates (PbSiO, PbSiO, and PbSiO) and lead oxide (PbO) between 700°C and 810°C. A high-temperature equilibration/quenching/electron probe X-ray microanalysis (EPMA) technique has been used to accurately determine the compositions of the phases in equilibrium in the system. Significantly, no liquid immiscibility has been found in the high-silica range, and the liquidus in this high-silica region has been accurately measured. The phase equilibria information in the PbO–SiO system is of practical importance for the improvement of the existing thermodynamic database of lead-containing slag systems (Pb–Zn–Fe–Cu–Si–Ca–Al–Mg–O)

Critical assessment and thermodynamic modeling of the Cu-As system

Thermodynamic assessment and modeling of the Cu-As system are presented. The experimental dataset includes phase equilibrium data, activity measurements, heat contents, enthalpies of formation and mixing. The liquid phase and two non-stoichiometric copper arsenide solid solutions are developed within the framework of the Modified Quasichemical Model (MQM) in pair approximation. It is demonstrated that the unconventional choice of model for solid solution phases is beneficial for this particular system. The resulting set of model parameters will be a part of a large multicomponent thermodynamic database. It is aimed for predictions of phase equilibria, heat balance and distribution of elements in arsenic-containing chemical systems in pyrometallurgical copper and lead industrial operations

Predicting coal ash slag flow characteristics (viscosity model for the Al2O3-CaO-'FeO'-SiO2 system)

A model has been developed which enables the viscosities of coal ash slags to be predicted as a function of composition and temperature under reducing conditions. The model describes both completely liquid and heterogeneous, i.e. partly crystallised, slags in the Al2O3-CaO-'FeO'-SiO2 system in equilibrium with metallic iron. The Urbain formalism has been modified to describe the viscosities of the liquid slag phase over the complete range of compositions and a wide range of temperatures. The computer package F * A * C * T was used to predict the proportions of solids and the compositions of the remaining liquid phases. The Roscoe equation has been used to describe the effect of presence of solid suspension (slurry effect) on the viscosity of partly crystallised slag systems. The model provides a good description of the experimental data of fully liquid, and liquid + solids mixtures, over the complete range of compositions and a wide range of temperatures. This model can now be used for viscosity predictions in industrial slag systems. Examples of the application of the new model to coal ash fluxing and blending are given in the paper. (C) 2001 Elsevier Science Ltd. All rights reserved