Thermal Analysis Kinetics Of A Tin-lead Slag Base System

Slag is the inevitable product of pyrometallurgical process.Its properties and control play a greatly important role in the smooth smelting process,reducing raw material consumption and producing qualified smelting products.In the process of lead and tin smelting,a large amount of copper dross and tin-containing dross are produced,and their physical and chemical properties have an important effect on the smelting effect.Therefore,the study on the physical and chemical properties of copper dross and tin-containing dross and their formation process is helpful to provide a theoretical basis for improving the smelting efficiency.Thermal analysis method has the advantages of high temperature measurement,high precision and diversified data.It can be used to study the formation process of copper scum and the volatilization characteristics of tin-containing slag under high temperature conditions.In this paper,several methods commonly used in thermal analysis kinetics are studied,such as Kissinger method,Ozawa method,Starink method,Achar-Brindley-Sharp-Wendworth method,Coats-Redfern method,etc.The derivation process of several equations and the method of calculating activation energy are analyzed in detail.The effects of molar ratio and heating rate on copper removal in crude lead refining were studied by differential thermal analysis.The results show that the reaction peak temperature and activation energy are lower when the reaction ratio of lead sulfide and copper is 1:1 than 1:2.The heating rate has a great influence on the copper removal reaction.When the heating rate is larger,the peak temperature of the reaction is higher,and the reaction moves to the high temperature direction.By means of Kissinger equation,Ozawa equation,Boswell equation and Starink equation,the activation energies of Pb S and Cu at 1:1 and 1:2 under non-isothermal conditions were calculated.The activation energy range of the reaction is 230?275 k J/mol.The volatilization characteristics of tin furnace slag at high temperature were studied by synchronous thermal analysis.Binary systems of SnO-SiO₂ and SnO-FeO and ternary systems of SnO-SiO₂-CaO and SnO-SiO₂-FeO were carried out thermal analysis experiment.It mainly analyzes the high-temperature volatilization behavior of SnO-SiO₂ and SnO-SiO₂-CaO.The Coats-Redfern method and ABS method are used to calculate the activation energy of the volatilization reaction.It is determined that the volatilization process is controlled by three-dimensional diffusion and satisfies the G-B(Ginstling-Brounshtein)equation.The results show that the activation energy of the ternary volatilization reaction of SnO-SiO₂-CaO is lower than that of the binary volatilization reaction of SnO-SiO₂.When FeO is added,the melting point of slag increases,which inhibits the volatilization of SnO and reduces the volatilization rate of slag.The addition of CaO improves the activity of SnO,which is beneficial to the reduction melting of slag,but increases the volatility of slag.The research results have a guiding significance for the formation mechanism and comprehensive treatment of tin slag.