Research On The Application Of MIVM In The Phase Equilibrium Of Tin Metallurgy

In the process of tin smelting,the thermodynamic properties of all components involved in the reaction are the theoretical basis for guiding actual production.However,the production environment at high temperature makes it unrealistic to predict all the thermodynamic data through experiments.Therefore,it can be a feasible way for predicting the thermodynamic properties by combining some accurate experimental data with a theoretical model.The activities of components in Sn-Pb-Bi,Sn-Sb-Bi,Sn-In-Bi and Sn-Fe-Pb ternary liquid alloys were predicted by the molecular interaction volume model-MIVM.The predicted values were in good agreement with the experimental data,for example,the standard deviation and the average relative error of activity of Bi were 0.0440 and 7.45%of comparing the predicted values with the experimental data in Sn-Pb-Bi at 1100℃.On this basis,the activity of all components in Sn-Fe-Pb-Bi quaternary system which were still lacking thermodynamic data have been predicted.The activity coefficients of components in Zn-Ag-Cu,Zn-Au-Cu,Zn-Ni-Cu ternary solid alloys were predicted by molecular interaction vacancy model-MIVM with three methods（the method of fitting experimental data of activity,the method based on liquid-solid equilibrium and the method based on infinite dilution activity coefficient）of obtaining the pair potential energy interaction parameters.The results showed that:the predicted values obtained by the method based on infinite dilution activity coefficient were in the best agreement with the experimental data,such as the average relative error of activity of Zn was 7.13%of comparing the predicted values with the experimental data in Zn-Ag-Cu at 1000K,while the average relative error were 35.54%and 18.60%by the method of fitting experimental data of activity and the method based on liquid-solid equilibrium.On this basis,the activities of components in the tin-based solid ternary systems Sn-Ag-Cu and Sn-Au-Cu which were still lacking thermodynamic data have been predicted and drawn by the isoactivity curves.The activities of components in CaO-FeO-SiO₂,SnO-FeO-SiO₂,SnO-CaO-SiO₂ternary systems and SnO-CaO-FeO-SiO₂ quaternary system were predicted by MIVM with its pseudo-multicomponent approach.The results showed that the predicted values were in good agreement with the experimental data,such as the standard deviation and the average relative error of activity of FeO were 0.0442 and 11.95%of comparing the predicted values with the experimental data in CaO-FeO-SiO₂ at 1450℃.On this basis,the activity of FeO in CaO-FeO-SiO₂ system was predicted and drawn by the isoactivity curves at the melting point of CaO.The liquid-solid equilibrium was established by the combination of MIVM and MIVM（vacancy model）.The equilibrium distribution of Pb in liquid and solid phases in the continuous crystallizer of crude tin refining process was calculated.It was found that the distribution coefficient of Pb between solid and liquid phase_Pb was less than 1,and gradually increased with the increase of temperature,such as from 460K to 495K,_Pb from 0.0759 to 0.1675.This indicated that separation of Pb and Sn can be carried out by mechanical crystallization,but the efficiency of removing Pb decreased with the increased of temperature.The equilibrium concentration of Fe and Sn in slag and metal phases during the reduction smelting was calculated by the combination of MIVM and its pseudo-multicomponent approach.The relationship between distribution coefficient and temperature and composition between slag and metal phase was obtained:ln L=7.462-2797.69?-1368000?³_[Fe]+43550?²_[Fe]-605.6?_[Fe]+ln（（FeO）?（SnO））The above research results will play a guiding role in tin smelting and the manufacture and development of corresponding alloys.