Using the HSC 6.1 Chemistry (Outokumpu) software package in combination with simplex-lattice planning, we performed thermodynamic modeling of the equilibrium cerium content in a metal containing 0.06% C, 0.25 Si, 0.05% Al (in this expression and further on the text indicates mass%), under the slag of the CaO – SiO2 – Ce2O3 – 15% Al2O3 – 8% MgO system in a wide range of chemical composition at temperatures of 1550 °C and 1650 °C. For each temperature, adequate mathematical models have been obtained in the form of a reduced polynomial of degree III, describing the equilibrium content of cerium in the metal depending on the composition of the slag. The results of mathematical modeling are presented graphically in the form of diagrams of the composition – the equilibrium content of cerium. A marked effect of slag basicity on the distribution of cerium is noted. An increase in slag basicity from 2 to 5 at a temperature of 1550 °C leads to an increase in the equilibrium cerium content in the metal from 0.1 to 7 ppm, i.e. the increase in slag basicity favorably affects the development of cerium recovery process. An increase in metal temperature has a positive effect on cerium recovery. As the temperature rises to 1650 °C, the equilibrium cerium content in the metal increases on average from 0.3 to 10 ppm. In the diagrams of the chemical composition of slags containing 56-61% CaO, 12-14% SiO2 and 15% Al2O3 in the temperature range of 1550 and 1650 °C, we can expect a concentration of cerium in the metal at a level of 7-10 ppm at a content of 4% to 7% Ce2O3 in the original slag. The positive effect of the basicity of the formed slag in the studied range of chemical composition on the cerium reduction process is explained from the standpoint of the phase composition of the slag and the thermodynamics of cerium reduction reactions.
Thermodynamic modeling of cerium reduction from slags of the CaO – SiO2 – Ce2O3 system containing 15% Al2O3 and 8% MgO by dissolved aluminum in the metal at temperatures of 1550 and 1650 °C was performed using the HSC 6.1 Chemistry software package (Outokumpu), based on minimizing Gibbs energy and variational principles of thermodynamics using the method of simplex planning lattices (mass% is indicated in this expression and hereinafter). When constructing the planning matrix, the following restrictions were imposed on the variable components of the CaO-SiO2-Ce2O3-Al2O3-MgO system: CaO/SiO2 = 2-5; 15% Al2O3; 8% MgO and 1-7% Ce2O3. As a result of imposing restrictions on the change of components in the system, the studied region is represented by a local simplex in the form of two concentration triangles whose vertices are the pseudo-components Y1, Y2, Y3 and Y4. It was found that depending on the temperature of the metal, the basicity of the slag and the cerium oxide content in the steel, containing 0.06% carbon, 0.25% silicon and 0.05% aluminum, goes from 0.055 to 16 ppm cerium. The positive influence of the temperature factor, slag basicity and cerium oxide content in the studied range of chemical composition on the cerium reduction process is explained from the standpoint of the phase composition of the formed slags and the thermodynamics of cerium reduction reactions. When the metal is kept under slag with a basicity of 2.0, containing 1.0% cerium oxide, it passes into the metal at a temperature of 1550 °C to 0.055 ppm cerium. An increase in the temperature of the system to 1650 °C is accompanied by a slight increase in the concentration of cerium, reaching no more than 0.085 ppm. The most noticeable increase in the cerium content in the metal is observed with an increase in the slag basicity. It is noted that the shift of slags containing 7.0% cerium oxide to the region increased to 5.0 basicity provides, in the temperature range 1550-1650 °C, the equilibrium cerium content in the metal at the level of 12-16 ppm.
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