Study On Recovery Of Iron And Manganese From Black Tungsten Residue By Magnetization Roasting

Many tungsten slag are produced every year in our country.It’s composition is complex,toxic and particle size is small.It is endangering the surrounding environment and has become a major environmental problem.At present,the annual output of wolframite slag in China has exceeded 116000 tons.Due to the lack of efficient,economic and mature harmless treatment process for wolframite slag,most of China’s tungsten smelting enterprises choose to build their own hazardous waste dump for storage.Many land is occupied by the accumulated wolframite slag and wasted,and is polluted by wolframite slag.On the other hand,the wolframite slag contains about 22%Fe and 31%Mn,which can not be recycled reasonably,which causes a great waste of resources.The technology of recovering iron and manganese from wolframite slag calcined in CO/CO₂ atmosphere was studied.By means of XRD,SEM,EDS and element content analysis,the effects of various factors on the phase,microstructure,magnetic separation recovery of iron,manganese grade and recovery of iron and manganese of wolframite slag after roasting in CO/CO₂ atmosphere were studied.The optimum conditions for the roasting magnetic separation process of wolframite slag were determined by experiments:the roasting temperature was 1000℃,the flow rate ratio of CO/CO₂ was 20 ml/min:180 ml/min,and the roasting time was 60 min.Under this condition,the wolframite slag is milled to 74-38.5μm,i.e.200 mesh to 400 mesh,and the magnetic field strength is set to 170 mt.The iron concentrate with 47.81%grade and manganese concentrate with 35.32%grade are obtained.The Fe recovery rate is 63.32%,the Fe grade in tailings is 29.72%,the Mn recovery rate is 63.65%,and the manganese grade in tailings is 36.44%.By analyzing the XRD diffraction image of calcined wolframite slag,it is found that Fe₂O₃·MnO in the wolframite slag is decomposed into Fe₂O₃ and MnO during the calcination process.After that,Fe₂O₃ reacts with CO in the furnace and is gradually reduced to magnetite particles,and MnO will be magnetically separated along with magnetite.However,if the calcination temperature,CO/CO₂ flow rate ratio and calcination time exceed the appropriate value,the magnetite will continue to reduce.When the roasting temperature exceeds the melting point of wolframite slag,the enrichment of magnetite becomes difficult and the effect of magnetic separation is poor.