Experimental Study On Recovery Of Metal Iron By Chlorination-smelting Reduction Of Depleted Copper Slag

The waste residue generated in the process of copper smelting,most of the copper slag in the disposal yard not only occupies much land,but also leads environmental problems.There are many kinds of valuable metals in copper slag,such as Cu,Fe,Zn,Pb,etc.Among them,the grade of metal iron is as high as 40%,so it has high recovery value.Although the metal iron can be reduced from copper slag by direct smelting reduction process,but the reduction of copper content in pig iron have significantly higher than the lowest copper content of 0.2%in iron and steel industry.The resulting metal iron can't be used for the smelting of ordinary steel,so it is necessary to find a suitable method for removing copperIn this paper,the predominance area diagram of Cu-Fe-Cl-O system was plotted.As is known to all,the low valent CuCl is the best target product for removing copper by chlorination in Cu-Fe-Cl-O system.If the appropriate temperature and chemical potential conditions are controlled in the process of copper slag chlorination,the copper can form CuCl at high temperature,and then react with chloride to form Cu3Cl3,and finally evaporate in the form of vapor.The idea of "first reduction and chlorination" was applied.Using copper slag as raw materials and coke as reducing agent,after obtained the metal iron by direct smelting reduction,the copper removal effect of "molten iron and chloride slag" system was studied by adding different solid chlorinating agents,such as NH4Cl,FeCl2,FeCl3,NaCl,KCl,MgCl2 and CaCl2.It is concluded that it can't reduce the copper content in metal iron by using "molten iron and chloride slag" system.The idea of "first chlorination and reduction" was applied.Using copper slag as raw materials and solid calcium chloride as chlorinating agent,the copper removal effect of solid calcium chloride was studied by molten chlorination experiment on copper removal from copper slag.It is concluded that the addition of solid calcium chloride can help to reduce the copper content in the copper slag,but the copper removal rate is not high,the maximum copper removal rate is only 42.03%.Meanwhile,the content of metal iron loss in copper slag after chlorination is serious,the volatilization rate of metal iron is as high as 44.49%,which is not conducive to the recovery of metal iron.The two stage process of "low-temperature chlorination and high-temperature reduction" was applied.Using copper slag as raw materials,solid sodium chloride as chlorinating agent and coke as reducing agent,the copper removal effect of reaction product cast iron was studied.During the experiment,the temperature of chlorination was controlled at low temperature for removing copper(850??1250?),the temperature of reduction is controlled at high temperature for recovering metal iron(1500??1550?).It is concluded that with the addition of sodium chloride,the effect of copper removal is obvious,and the maximum copper removal rate can reach 57.65%.Meanwhile,the content of iron in the reaction product was higher,which was about 90%,However,the reduced cast iron contains harmful impurities,such as C,S,P,As,etc,especially containing inclusion element As.