Study On MIVM Pseudo - Multivariate Approximation Of Slag - Iron Liquid Equilibrium In Titanium - Bearing Blast Furnace

In this thesis, based on the molecular interaction volume model (MIVM) and its pseudo-multicomponent approach, the equilibrium distribution of titanium between blast furnace-type slags and carbon-saturated iron in blast furnace are investigated. The research will takes basic data with comprehensive utilization of the vanadium and titanium resources.Based on the Kuo-chih Chou formulae of calculating activities from binary phase diagrams, two methods are proposed to improve numerical integration for the formulae. The component activity data of CaO-SiO2and MgO-SiO2melts are calculated by the methods under the condition of regular solution’s assumption. The calculation results are in reasonable agreement with experimental data, and the total average relative errors between calculated values of the two methods and experimental data are20%and8%respectively. The results show that the new methods are feasible in the practical application. Accordingly, the component activity data of CaO-TiO2, Al2O3-TiO2, SiO2-TiO2and MgO-TiO2melts at a given temperature and concentration are calculated by the proposed methods. The relative errors for these systems are comparable to the results of CaO-SiO2and MgO-SiO2systems. So the activity data obtained can be used as reference data for thermodynamic study of titanium-bearing blast furnace slag.Some activity calculation models for calculating activity of the conventional blast furnace hot metal and the hot metal bearing vanadium and titanium are determined based on MIVM. The activity data of Si, Mn in Fe-C-Si, Fe-C-Mn and Fe-C-Si-Mn melts, as well as the activity data of Ti in Fe-C-Ti melt are predicted by these models, and the predicted results are compared with the Wagner formalism and literature data. The results indicate that in the Fe-C-Si and Fe-C-Mn systems, the average relative errors between predicted values of MIVM and experimental data are18%and6%respectively, while the average relative errors between calculated values of Wagner formalism and experimental data are55%and11%respectively. Therefore the predicted values of MIVM are in good agreement with the experimental data, and the predictive effect of MIVM is better than the Wagner formalism, In the Fe-C-Ti systems, the predicted activity of Ti by MIVM is in reasonable agreement with a calculated data of literature, and the values of both are0.0025and0.0013respectively (Activities are referred to pure solid Ti). The predicted activities of above every system by MIVM at1873K are in the same order of magnitude with the Wagner formulism, and the total average relative error between the predicted values of MIVM and the calculated values of Wagner formulism is9%. In summary, these models established are feasible. The activities of Ti in Fe-C-Ti-Si-Mn-V melt and its influencing factors (temperature and component of hot metal) are predicted by using the established model.Based on the MIVM and its pseudo-multicomponent approach, a activity calculation model for calculating activity of every component in BF slag bearing titania system consisting of Al2O3-CaO-MgO-SiO2-TiO2is determined. The activities of TiO2in this system are predicted by using the established model, and the predicted results are compared with some published values. Some related laws are summed. The results indicate that the predicted activities of model are slightly higher than the experimental data, and the average relative error between predicted values of the model and the experimental data is44%. But both are in the same order of magnitude. Some laws obtained by this model are consistent with the experimental laws. For the BF slag bearing titania system, the present model is more reasonable and applicable than the coexist theory model. In summary, thes model established is feasible.The equilibrium contents of Ti to form titanium carbide or carbonitride from the Fe-Csat-Ti melt are predicted by using the established model, and the predicted results are compared with some experimental values. The results indicate that the predicted values of model are in reasonable agreement with experimental data. That proves that the methods of this work are feasible. The equilibrium contents of Ti to form titanium carbonitride from the Fe-Csat-Ti-Si-Mn-V melt and its influencing factors (temperature and partial pressure of burner gas) are predicted by present model. The results indicate that increasing the temperature or reducing the nitrogen partial pressure can make the equilibrium contents of Ti to form titanium carbonitride increase. Thus these measures can inhibit the formation of titanium carbonitride from the hot metal.The equilibrium contents of TiO2to form titanium carbonitride from the BF slag bearing titania consisting of Al2O3-CaO-MgO-SiO2-TiO2and its influencing factors (temperature, basicity of slag and partial pressure of burner gas) are predicted by using the established models, and the predicted values are compared with published values. The results indicate that the predicted value of model is in reasonable agreement with a calculated data of literature, and the values of both are4.337%and5.3%respectively (mass percent). And reducing the temperature, increasing the basicity of slag, increasing the total pressure of burner gas and reducing the values of PN2/P∞can make the equilibrium contents of T1O2to form titanium carbonitride increase. Thus these measures can inhibit the formation of titanium carbonitride from the the slag. Finally, the equilibrium distribution coefficients of Ti between blast furnace-type slags and carbon-saturated iron in blast furnace are estimated by using present model. The results indicate that reducing the temperature, increasing the basicity of slag and increasing the partial pressure of carbon monoxide can reduce the reduction values of TiO2, and these measures can inhibit the reduction of TiO2. The effect of the TiO2content in the slag on its theoretical reduction value is relatively small.For the vanadium titano-magnetite’s smelting in blast furnace, the effect of the temperature and the basicity on the reduction of TiO2and the formation of titanium carbonitride is relatively big, while the furnace gas condition is relatively small. Some measures of relative low temperature and higher basicity are adopted usually in smelting to prevent the reduction of a great of TiO2, as well as the formation of titanium carbonitride from the slag. The furnace gas conditions of the higher total pressure and lower PN2/P∞can also inhibit the reduction of TiO2and the formation of titanium carbonitride from the slag. This work well be reference value for improving the vanadium titano-magnetite’s smelting theory in blast furnace and guiding blast furnace protection operating practices.