Study On Recovery Of Iron During Coal Based Direct Reduction Of Copper Slag

The copper slag is rich in iron resources,which are mainly composed of olivine(Fe Si O),magnetite(Fe 0),and glass phase composed of gangue that is no fixed form.Therefore,the composition of copper slag is complex and the grain size is small,It is difficult to recover iron effectively by traditional ore dressing method.The key to recovering iron from the copper slag is to break down its olivine structure so that the iron is separated from the oxide of the silicon,transforming the iron in the olivine(Fe Si O)into Fe 0 or metallic iron(Fe),which is then recovered by grinding and magnetic separation.The direct reduction process was used to recover iron from copper smelting slag in this research.The range of reaction temperature was determined by thermodynamic calculation.By means of SEM analysis of roasted ore at different temperatures and XRD test and SEMEDS analysis of iron concentrate,the transformation rule and microstructure change of iron phase in direct reduction were obtained,and the growth rule of metal iron particles in direct reduction of coal base was analyzed.By fitting and analyzing the reduction degree data and stage dynamics,the activation energy required for the reduction reaction under different reduction degrees was calculated.Under the optimal roasting system: roasting temperature: 1300?,roasting time: 30 min,reducing coal ratio: 35%,alkalinity: 0.75.Under this condition,iron and silicon can be separated effectively by grinding-weak magnetic separation,TFe,metallization rate and recovery rate are 91.55%,92.99%,82.99%,respectively.The phase transition rule of iron is as follows,Metal iron was generated at 1050?,1100? and 1150?,but the reduction degree and TFe were lower.At 1200?,it was found that Fe C and Si C phases were generated,and the formation of Ca Si O · Fe Si O liquid phase affected the reduction process.Fe C is formed at 1250?,and Fe Si O forms a low melting point mineral with Ca O.At 1300?,the concentrate contains a large amount of metal iron,but it also forms a compound with low melting point,which increases the difficulty of treatment.The growth behavior of metallic iron particles is that the metallic iron particles first appear at the edge of cracks and holes caused by oxygen loss of mineral particles,the small metallic iron particles are absorbed by the large particles and coalesce and grow up,and the metallic iron finally forms a dense metallic iron layer after the transformation from spotty to worm-cactus.The kinetic analysis shows that the gas phase diffusion is the single speed limiting link in the process of direct reduction of copper slag coal base,and the activation energy value is 139.126 kj /mol.Periodic kinetic analysis was conducted for the direct reduction process.As the reduction degree changed,the activation energy value was within the range of 50.416 ? 275.962 k J/mol.