Study On Recovery Of Valuable Metals From Slag Of Tin Refining Furnace By Pyroetallurgical Smelting

With the depletion of raw tin resources,in order to achieve sustainable development of the tin metallurgical industry,it is increasingly important to effectively recover and utilize large amounts of tin-containing slag in the tin smelting process.There are mainly two kinds of slag in crude tin refining process.Aluminum slag produced by adding aluminium to remove arsenic and antimony and sulphur slag produced by adding sulphur to remove copper.The harmful elements such as sulphur and arsenic in tin-smelting slag pollute the environment greatly in the stacking process,and the tin and copper in the slag have higher recovery value.In this experiment,the sulphur slag produced in tin smelting process was used as raw material,and the valuable metal elements Sn and Cu were mainly recovered.Physical separation-oxidation roasting-sulfuric acid leaching process was used to treat tin-smelting sulphur slag.Firstly,metal particles in sulphur slag were separated by grinding and sieving,which reduced the treatment of sulphur slag under sieve.By means of XRD,XRF,SEM,ICP-AES and atomic absorption spectrometry,the effects of roasting time and temperature on the roasting process of sulphur slag were studied,and the optimum roasting conditions were determined.The effects of leaching time,leaching temperature,liquid-solid mass ratio,stirring rate and H₂SO₄ concentration on the leaching process were also determined.Finally,the CuSO₄.5H₂O and SnO₂ products are obtained by treating the leachate and the leaching slag,so as to effectively recover valuable elements Sn and Cu and remove harmful elements S.The main research conclusions are as follows:The sulphur slag was grinded by a grinder for 20 minutes and sieved by a 60 mesh sieve.The separated metals accounted for 23.66%of the sulphur slag.Sn accounted for 85.79%and Cu 9.90%.The sulfur slag under sieve is mainly the sulfide of tin and copper.The Sn and Cu elements are recovered by oxidation roasting and sulfuric acid leaching.The oxidation roasting of sulfur slag under sieve can be divided into two stages.In the first stage,the roasting temperature is controlled at about 500?,and in the second stage,the aim is to oxidize Sn and Cu into the highest valence stable oxides and desulfurization.The optimum roasting temperature is 800? and the optimum roasting time is 60 min at this temperature.SnO₂ and CuO are the main components of calcine after calcination.The roasted sulphur slag is leached with sulphuric acid.The optimum conditions of leaching were determined by orthogonal experiments and single factor experiments:leaching time 50 min,leaching temperature 70?,liquid-solid ratio 3:1,stirring rate 400 r/min,H₂SO₄ concentration 20%.The leaching process of calcine was analyzed by kinetics.Kinetic analysis shows that the leaching process of sulphur slag calcine conforms to the internal diffusion control model.The apparent activation energy E of leaching process is 23.608 kJ·mol^-1.The leaching solution is crystallized and concentrated to obtain CuSO₄·5H₂O,and the leaching residue is washed to obtain SnO₂.Under the optimum conditions of the process,the recovery of copper and tin is 90.38%and 93.13%,respectively.The purity of CuSO₄·5H₂O and SnO₂ is 97.66%and 98.78%,respectively.