Study On The Process Of Copper Slag Reduced By Pyrolyzed Natural Gas And Analysis Of The Inclusions

Our country’s copper resources are depleting. Currently copper ore whose copper content ranging from 0.2% to 0.3% has been exploitation. Large quantities of copper concentrate need to be imported. Meanwhile, huge copper slag is piled up from copper melting. Its copper content is usually over 0.5%, and iron content is often more than 40%. Therefore, comprehensive recovery of valuble elements such as iron and copper of copper slag is of great significance.Currently, the methods of industrial’s impoverishment processes of copper slag include pyrometallurgical depletion and slag beneficiation. Beneficiation method uses magnetic separation and flotation separation to enrich valuable metals. However, it has high requirement on copper slag and generally it can only deal with curing state copper slag or ore. Mostly used in industry is pyrometallurgical depletion. It mostly extracts copper of the slag and the iron is often discarded as impurities or inhibited to enter the residue. It has many disadvantages, such as low copper recovery, high energy consumption and gas pollution. For this reason, the research topic group puts forward a new technology using valuable metal reduced from copper slag by pyrolyzed natural gas to melt copper antibacterial stainless steel. The advantages of this method are:make full use of hot copper slag chemical latent heat. the reducing agent has high chemical reactivity, and efficient extraction of copper, iron and other valuable metals from copper slag smelting high added value of copper antimicrobial stainless steel directly.The thermodynamics of copper slag and gas reaction system is analysed in this paper firstly. The composition and mineral phase of copper slag, orthogonal experiment of copper slag reduced by pyrolyzed nature gas and 2kg amplification experiments of medium frequency induction furnace are analysed. Analysis and characterization of the result is conducted by using XRD, SEM, ICP, chemical analysis, and metallographic microscope analysis methods. The following conclusions can be obtained:(1) The thermodynamic calculations shows that:between 1300℃～1500℃, Fe2SiO4、 Fe3O4、CuO、ZnO、MoO etc oxides of copper slag can be reduced. During Oxygen steelmaking process, [Si]、[B]、[Ti]、[Al]、[Mg]、[Ce] etc of hot metal can be oxidized into the slag; [Cu]、[Ni]、[Mo]、[W]、[As]、[Sb]、[Co] etc can’t be oxidized into the liquid steel. Draw the gas phase equilibrium composition diagram of iron oxide reduction process and predominance diagrams of Fe-Cu-C-0 system using HSC thermodynamic software. Iron and copper have a co-existenc stability region.(2) Making model of CaO-MgO-FeO-Fe2O3-Al2O3-SiO3-Cu2O slag system based on the coexistence theory. The action concentrations of FeO increases with the rising of temperature, increases first and then decreases with the increase of CaO content, decreases with the increase of Al2O3 content, decreases when CaO content is over 15%.(3) The optimal reaction condition is aobtained from orthogonal experiment of copper slag reduced by pyrolyzed natural gas reaction:temperature is 1425℃, the alkalinity is 1.0, oxygenation time is 30min, here reduction rate of metal is 91.74%, The reaction temperature has a significant effect on reduction rate. The inclusions of As in hot iron distributed uniformly, mainly combinates with Fe as form of FeAs. The small amount of C forming cementite with Fe uniformly. S combinates primarily with Fe and Cu to form metal sulfides in hot iron.(4) Amplification experiments of induction furnace, reduction rate of metal increases as the reaction temperature increases. While As, S impurities in hot iron decrease with rising temperature. Metal reduction rate increases first and then decreases with increasing alkalinity. When the basicity is 1.2, the reduction rate was 85.03%. While As and S impurities in hot iron decrease with rising alkalinity.(5) Separation of slag and gold is good. Fe and Cu of the slag enrich to metallic phase during reduction. Part of the As and S is removed, the remaining into molten iron. Zn and Pb get into dust as their oxide. SiO2、CaO、Al2O3 etc get into final slag.