Akihiro Yoshimura1, Ichiro Daigo2 and Yasunari Matsuno2
1Department of Materials Engineering, Faculty of Engineering, The University of Tokyo, Tokyo 113-8656
Recently, recycling of rare metals has been of great interest because of the rapid growth in their demands and maldistribution of the natural resources. Substance flow analysis (SFA) is a useful tool to figure out the flow of substance in specific regions. However, few SFA has so far been conducted for rare metals. In this paper, we focused on indium and conducted SFA of indium in Japan and global scale. The most of indium is used as Indium Tin Oxide (ITO). The end use of ITO was categorized into 2 groups; Liquid Crystal Display modules and Plasma Display Panel modules, which were further assembled to final end-use products. Quantified was the flow of indium during its lifecycle; mining and smelting, manufacturing, use and waste management. In mining and smelting, the data about the indium content in ore and production of primary metal of indium during 1999-2008 were collected. In manufacturing, we estimated the content of indium of final end-use products, and estimated the input of indium for producing ITO in Japan. Then, we extrapolated the results to SFA in global scale. In-use stock and discard of indium were estimated by dynamic SFA, in which the time-series data about the input of indium in final end-use products and their lifetime distribution were used. In this study, we estimated the loss of indium in each process as recovery potential. It was found that the extraction rate of indium in mining and smelting process was 8-11%, and the loss of indium in the process was 4,826 t in 2004. The amount of loss in manufacturing process was 310 t, in-use stock of indium was 115 t, and the discarded indium in end-of-life products was 5 t in global scale in 2004. Therefore, it was concluded the biggest recovery potential of indium was in mining and smelting.
substance flow analysis, indium, liquid crystal display, plasma display panel, recycle potential, in-use stock
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