Study On Eddy Current Reduction Of Copper Slag For Smelting Copper-bearing Wear Resistant Cast Iron

With the rapid development of the copper smelting industry,global refined copper output has also increased significantly.China is a major producer of refined copper and a major producer of copper slag.In 2018,the domestic output of refined copper has reached 9.929 million tons,and the amount of new domestic copper slag will reach 20 million tons each year.Effectively consuming and processing copper smelting slag has become an important measure to solve resource and environmental problems.At present,most enterprises adopt copper beneficiation or electric furnace depletion to treat copper slag to achieve a certain level of copper resource recovery,but a large amount of iron-containing tailing slag is still difficult to reasonably arrange.Due to the limitation of processing capacity,process economy,and practical application performance,iron-containing tailings are still treated by storage or sale.The problem of copper slag severely restricts the sustainable development of the copper smelting industry.The comprehensive utilization of copper slag and the high value of end products are an inevitable choice for achieving sustainable development of copper smelting slag utilization.Northeastern University proposes a slag-free utilization technology based on high-end copper slag endurance,that is,to moderately deplete copper slag with high copper and iron content.The depleted slag is mixed with coking coal to perform eddy current depth reduction to obtain copper-containing molten iron.Casting and heat treatment to smelt copper-containing wear-resistant cast iron.In this paper,thermodynamic analysis,XRD,SEM,ICP,metallographic observation and other methods are used to study the copper slag mineralogy,moderate depletion,eddy current depth reduction,smelting of wear-resistant cast iron,and economic benefits,and draw the following conclusions:(1)Through copper slag mineralogy research,copper slag contains 12.5%copper,39.62%iron,and also contains valent metal lead 0.94%,zinc 3.88%,gold 14.1 g/t,and silver 129.6 g/t,which has high Recycling value.Judging from the microscopic morphology of copper slag,the copper inlay has a complex form and is heavily wrapped by olivine.The material phase is mainly composed of magnetite phase,olivine phase,porphyrite phase,and sphalerite phase.(2)After the copper slag is remelted,the copper matte will settle freely,but the copper content is still as high as 1.68%after 60 min of dilution,which cannot meet the requirements of subsequent reduction.Using eddy current dilution process,the optimum conditions are:temperature 1250?,adding amount of vulcanizing agent is 3%,ratio of iron to silicon is 1.4,adding into CaF2 0.6%,CaO 4%,stirring 250 rpm,1 min,settling stirring 63 rpm,60 min,can reduce the content of copper in the slag to 0.611%.Under the same temperature and additive conditions,without stirring dilution for 60 min in industry,the copper content could only be reduced to 1.53%,with a significant difference.In the process of eddy current moderate dilution,the elements were redistributed,93.14%Cu,67.95%Sb,94.03%Ag,99.44%Au and 55.36%S entered the copper mattes;93.97%Fe remains into the depleted slag;81.90%Zn,75.55%Pb and 67.27%As went into the flue gas.(3)the reduced copper slag adopts the eddy current deep reduction process,the optimal conditions are:temperature 1450?,alkalinicity 1.0,reducing agent addition is 1.5 times the theoretical value,according to CaF2/CaO=10%and mixed into CaF2,stirring 250 rpm,5 min,settling and stirring 63 rpm,30 min,the recovery rate of reducing copper and iron is 91.76%.During the deep eddy current reduction process,75.26%Cu,92.13%Fe,82.11%Pb,94.11%Ag and 88.66%Au went into the reduction metal.97.90%of the Zn went into the flue gas.(4)The reduced metal obtained by eddy current reduction is tempered by adding alloying elements and then cast.After cooling,a wear-resistant cast ball is obtained.Its composition is:C content 3.29%,Si content 0.52%,Mn content 0.83%,and P content 0.08%,S content of 0.02%,Cr content of 11.32%,Ni content of 0.96%,Mo content of 0.63%,Cu content of 1.17%,in line with the national standard of HBW555Cr13 wear-resistant cast iron.Through the"quenching and tempering" heat treatment,the cast ball matrix was transformed from austenite to martensite,and the volume fraction of(Fe,Cr)7C3 carbide increased by 0.95%to 16.11%,which improved the wear resistance of the material.(5)According to the copper slag smelting process of copper-bearing wear-resistant cast iron,there will be a direct benefit of 1185.45 yuan for each ton of copper slag processed,and there is a potential economic benefit of 6616.8 yuan for the enriched valuable metals Cu,Pb,Zn,Au and Ag.Copper slag smelting copper-containing abrasion resistance is a new type of solid waste high-value application process,which can achieve large-scale,slag-free production goals,and has huge economic benefits and market prospects.