Experimental Study On Separation Of Tin And Copper By One-step Vacuum Sulfidation Volatilization Of Tin Refining Sulphur Sla

Tin is one of important strategic metals.China is the largest country of tin reserves,production and con sumption in the world.However,tin ore has low grade and many kinds of impurities.The tin refining process will inevitabl y produce a large amount of refining slag,among which sulfur slag is produced by adding sulfur to remove copper.It mainl y becomes m etal tin,cuprous sulfide and stannous sulfide,and contains impurities such as arsenic,antimony and lead,which is classified as hazardous solid waste.The traditional comprehensive utilization method of sulfur slag has the problems of low separation eff iciency of tin and copper,long process flow and poor economy.It is urgent to develop new technologies for the treatment and utilization of sulfur slag to achieve clean and efficient separation of tin and copper.In this paper,a new idea of one-step vacuum sulfidation and volatilization separation of tin and copper from tin refining sulfur slag was proposed.The phase composition of each substance in sulfur slag and vulcanizing agent was studied.The thermodynamic data such as saturated vapor pressure,de composition of vulcanizing agent and Gibbs free energy of sulfidation and volatilization of tin were calculated.The theoretical feasibility of one-step vacuum sulfidation and volatilization treatment of sulfur slag was anal yzed.The results show that tin can react with vulcanizing agent to form stannous sulfide,and the remaining products are mixed phases of copper,iron and sulfide.According to the difference of vapor pressure,stannous sulfide is easy to volatilize into the gas phase at low pressure and separate from the residual copper-rich phase.On the basis of theoretical anal ysis,the thermogravimetric experiments of vulcanizing agents such as pyrite and chalcopyrite and stannous sulfide,the vacuum thermal decomposition of vulcanizing agents and th e vacuum vulcanizing volatilization experiments of metal tin and vulcanizing agents were carried out.The results show that under high temperature and vacuum conditions,pyrite will decompose into ferrous sulfide,and chalcopyrite will decompose into ferro us sulfide and cuprous sulfide.Tin can react with the vulcanizing agent to form stannous sulfide and volatilize into the gas phase.The residue is a mixed phase of copper,iron and its sulfide.The vacuum vulcanization volatilization experiment of sulfur slag and vulcanizing agent was carried out.The effects of vulcanizing agent t ype,vulcanizing agent ratio,reaction temperature,system pressure and holding time on the separation of tin and copper were investigated.The results show that:(1)When the selected vulcanizing agent is pyrite,the best reaction conditions are as follows:reaction temperature 1273 K,pyrite addition ratio 40%,system pressure 10 Pa,holding time 3 h;the volatiles are tin sulfide and sulfur,and the residues are cuprous sulfide and ferrous sulfide.The purit y of stannous sulfide in the volatile is more than94%,the direct recovery of tin is 99.95%,and the direct recovery of copper and iron in the residue is 99.77% and 99.57%,respectivel y.(2)When the selected vulcanizing agent is chalcopyrite,the best reaction conditions are as follows:reaction temperature 1373 K,chalcopyrite addition ratio 70 %,system pressure 10 Pa,holding time 3 h;the volatiles are tin sulfide and sulfur,and the residues are cuprous sulfide and ferrous sulfide.The purit y of stannous sulfide in the volatile was more than 93%,the direct recovery of tin was 99.87%,and the direct recovery of copper and iron in the residue was 99.64% and 99.44%,respectivel y.The research results provide important theore tical and practical reference for the development of new technologies for efficient utilization of sulfur slag.