| The thermodynamics properties of CaO-SiO2-Al2O3-MgO-FetO system have significant effect on the quality of hot metal produced by smelting reduction process. The activity of FetO, sulphide capacity and phosphorus capacity of CaO-SiO2-Al2O3-MgO-FetO slags were investigated systematically, and the activity of each component was calculated by simulation method. The results can supply theory basis for the quality of hot metal of smelting reduction process.The FetO activity of the slag was measured by a Mo | Mo+MoO2 | ZxO2 (MgO) | Fe+(FeO)+Ag | Fe solid-electrolyte cell. The effects of slag compositions, reaction temperature, and gas conditions on the FetO activity were obtained. The results show that the above factors affect the FetO activity significantly. At the constant temperature and ternary basicity, the FetO activity increases with the MgO content increasing from 5% to 10%, and decreases when the MgO content is over than 10%. The FetO activity rises with the increase of FetO content at a fixed binary basicity, and it also rises when the binary basicity increases; the influence of temperature on the FetO activity varies with the change of gas. The temperature has insignificantly effect on the FetO activity at pure Ar atmosphere. When the oxygen partial pressure is raised at a fixed temperature, the FetO activity also increases. The FetO activity enhances with the increase of temperature at a constant ratio of CO, CO2 and Ar.The sulphide capacity CaO-SiO2-Al2O3-MgO-FetO slags were determined by gas-slag equilibrium method, and the effects of slag compositions, reaction temperature, and gas conditions on the sulphide capacity were studied. It can be seen from the results that at the constant condition of temperature and gas atmosphere, the sulphide capacity reduces with rising the MgO content of the slag, ant it enhances with increasing the FetO content or the binary basicity of the slag; when the temperature is increased, the sulphide capacity enhances at a fixed slag composition and a fixed flow of CO, CO2, SO2 and Ar; the sulphide capacity rises with the increase of the oxygen partial pressure of the system at the constant condition of temperature.The phosphorus capacity CaO-SiO2-Al2O3-MgO-FetO slags were determined by gas-slag-metal equilibrium method, and the effects of slag compositions, reaction temperature, and gas conditions on the phosphorus capacity were gained. The results show that when the reaction temperature, ternary basicity, Al2O3 and FetO content are constant, the phosphorus capacity reduces with enhancing the MgO content of the slag. With the increase of binary basicity or the FetO content, the phosphorus capacity raises at a fixed reaction temperature. When the temperature is increased, the phosphorus capacity decreases at a constant condition of slag composition and oxygen partial pressure. The phosphorus capacity enhances when the oxygen partial pressure is increased at a constant temperature and slag compositions.The component activity calculation model of CaO-SiO2-Al2O3-MgO-FetO slags was established by slag co-existence theory, and the relationship of slag composition and the activity of each component in this slag system were analyzed. The calculation results indicate that the activity of MgO, CaO and FeO enlarge respectively with the increase of MgO content of the slag, while the SiO2activity decreases significantly and the Al2O3 activity enhances slightly; when the FeO content of slag is increased, the activity of FeO and CaO rises, the SiO2 activity reduces, the Al2O3 activity increases slightly. While the MgO activity firstly raises and reduces later with the FeO content of slag increases; When the binary basicity rises, the MgO activity firstly increases and decreases later, while the activity of FeO and CaO enhance greatly and the Al2O3 activity increases slightly. The SiO2 activity decreases with increasing binary basicity to 1.3. Subsequently, it has weakly effect on the SiO2 activity when the binary basicity is increased continually. |
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