Study On The Depletion Characteristics Of Copper And Iron During The Stepwise Depletion Of Copper Slag

Copper slag is a by-product produced in the copper smelting process,in 2016,the annual output of copper slag was nearly 20 million tons in China.At present,copper slag rich in a large number of valuable metals is stored for a long time due to lack of effective recovery,which occupies land and pollutes the environment,resulting in a huge waste of resources.It is a strategic goal for the development of nonferrous metallurgy to optimize the smelting method of copper slag and improve the effective recovery and utilization of copper and iron metal resources in the slag under the situation that copper and iron resources are increasingly exhausted.Copper slag is mainly produced by fire smelting process,which contains high content of valuable metals such as copper and iron,generally,Fe content is about 40%and Cu content is 0.5-8%.However,due to improper control of reduction degree,the traditional method for recovering depleted metal from copper slag often produces a large number of metal alloys or compound in the products,requiring separate treatment by different subsequent leaching processes,as a result,the overall recovery effect of valuable metals is not good,and the recovery rate of copper and iron in slag are less than 75%.The amount of disposable treatable slag is small and the process has not been industrialized on a large scale.At the same time,due to the need to add a larger dose of leaching test,it causes serious corrosion of equipment and environmental pollution.Therefore,in order to realize the selective and effective recovery of copper and iron resources in the slag and avoid the formation of a large number of metal alloys in the process,this study prioritized the copper phase in the slag over the iron oxide dilution separation.It proposes to adopt the method of steps dilution method of molten copper slag（settlement of copper matte-reduction of copper-reduction of iron）to effectively separate the copper and iron in copper slag.The slag from a copper smelting enterprise in China is taken as an example.Study the effect of different dilution temperature,time,flux CaO and reducing agent carbon powder adding quantity on copper and iron separate depleted effect in slag and determine the optimal dilution condition.The experimental results indicated that:Copper matte sedimentation is a physical process,a number of Cu₂S in the slag gathered to form large size matte phase by collisions occurring due to mutual attraction between particles,large size matte is separated from the slag for the physical properties such as gravity and density difference,and the copper in the slag is preliminarily depleted.Copper content decreases with increasing dilution temperature and time,when the temperature and the dilution time increases to a certain extent,content variation is not significant,ultimately determine the optimal dilution temperature and time at 1350℃and 25 min respectively,copper slag reduced from 6.1%to 3.23%,and Cu₂S content reduced to 0.76%.In the process of reducing depleted copper oxide,a proper amount of reducing agent carbon powder is added to reduce copper oxide in the slag,and Fe₃O₄ phase was converted to FeO at high temperature,reducing the viscosity of slag,promoting the generation of copper phase and separating from slag phase.In addition,the added flux CaO combined with SiO₂ solid in slag can reduce the viscosity value of slag and optimize the dilution effect.Within a certain range,the dilution separation effect of copper phase in slag increases with the increase of temperature,reducing agent and flux addition.comprehensive consideration from energy consumption and cost etc.,the optimum temperature,reductant and flux addition amount are 1350℃,2.5%and 22%respectively,copper content in slag decreased from 6.1%to 0.51%,and the dilution rate reached91.64%.For further recovery restore depleted the valuable metallic iron in copper tailings,according to the results,the temperature,reducing agent carbon powder and flux CaO additives under the condition of 1350℃,8%and 24%respectively,slag iron dilution effect is optimal.The iron content decreased from 44.71%to 11.94%,and the reduction rate and dilution rate of iron phase reached 86.12%and 83.56%,respectively.The system was transformed into SiO₂-CaO-Al₂O₃ slag phase with simple structure,which provided stable slag type for the subsequent resource utilization of copper slag.