Carbothermal Reduction-Slag Fractal Method For Enrichment And Separation Of Iron And Rare Earth From NdFeB Scrap

NdFeB scrap contain many valuable metallic elements such as rare earth neodymium,terbium,dysprosium,cerium,praseodymium and iron which have a high comprehensive recycling value.At present,NdFeB scrap recycling technology is commonly used as "rotary kiln roasting-acid leaching-extraction separation-precipitation-burning",which have disadvantages of long process flow,low recovery,iron slag difficult to handle,scrap of iron resources and others urgently needed to be innovated.Thesis studies on "Carbothermal Reduction-Slag Fractal" technology to recycle rare earth from NdFeB scrap,which is the innovation of the existing technology,and has theoretical and practical value to enhance the technical level of NdFeB scrap recycling industry.Based on the NdFeB scrap chemical and physical phases characteristics,also the difference in the reducibility of iron oxides and rare earth oxides,carried out the theoretical and technological research on the carbothermal reduction of “calcined sand” which is the oxidation of NdFeB scrap,obtained the carbonthermal reduction thermodynamics and conditions of “calcined sand”,also studied the effects of the type of reducing media,material particle size,reaction time,reaction temperature,material carbon ratio and material thickness on the reduction status.The results show that the carbothermal reduction can reduce the iron oxides in the “calcined sand” to sponge iron,and the same time rare earth oxides are not reduced.When the type of reducing media is coke,the reaction time is 4h,and the reaction temperature is 1200°C.the carbon ratio of material to is 30% and the thickness of material is 22 mm,the reduction rate of iron oxide in “calcined sand” is 88.08%,which provides a useful separate separation and enrichment recovery way for rare earth and iron in the NdFeB scrap.Based on the carbothermal reduction,systematically studied the slag fractal technology of NdFeB scrap reduction products,investigated the reaction thermodynamics of slag fractal,analyzed the effects of the reaction temperature,reaction time,material carbon ratio and material thickness to the slag fractal,carried out the sources and distribution of impurities in iron slag and rare-earth-rich slag.The results show that thermodynamic conditions can be created to separate iron and rare earth oxides as much as possible at high temperature.When the reaction temperature is 1500°C,the reaction time is 3h,the carbon ratio is 50%,and the material thickness is 26 mm,the iron and the rare earth enrichment rate was 93.05% and 97.52%,respectively,the separation effects of rare earth and iron was good.Pr,Ce,Nd,C,S,O,etc.are the impurity elements in the iron block,the impurity elements in the rare-earth-rich slag mainly include Al,Si,Fe,C,S,and Ca,and there are both mainly derived from coke ash.