Substance flow analysis of neodymium based on the generalized entropy in China

Rare earth plays an important role in fields of aerospace, electronic products, catalyst, agriculture and others. China is the largest producer and consumer of rare earth materials in the world. Neodymium is widely used in rare earth industry. Substance flow analysis (SFA) is an established method to analyze the structure and characterization of substance flows. This paper provided SFA and generalized entropy analysis for neodymium in China in 2002 and 2011. System boundary included exploitation, concentration, smelting, manufacture, use and disposal. Neodymium flow amounts and generalized entropy value were calculated, respectively. Mining utilization efficiency, smelting ratio, export rate were comparatively analyzed in 2002 and 2011. The results demonstrated that the utilization efficiency of neodymium in the rare earth concentrates production stage increased more than 69%, while the utilization efficiency of neodymium in the manufacture stage increased more than 28% in 2011 compared to 2002. The generalized entropy results indicated that congregated degree of neodymium was larger in 2011 compared to 2002 after concentrate production stage and manufacture stage, the congregated degree increased 45.5% and 12.5%, respectively. Based on the results, some advices were proposed, which provided available reference information for resource conservation and environmental friendly development of the Chinese rare earth industry.