他元素との関わりを考慮した日本における亜鉛の動的物質フロー分析モデルの構築

Abstract

In this paper, a dynamic substance flow model of zinc in Japan was conducted. Currently, 60% of zinc is consumed for galvanized steels (galvanized steel sheets and other galvanized steels), followed by brass in Japan. To analyze the substance flow of zinc in a dynamic way, the linkages of zinc with other substances were considered in this model. Furthermore, the dissipated zinc during the use phase was taken into account using the existing results of atmospheric exposure tests. At the end-of-products, most of zinc is recovered as steel scraps or copper alloy scraps. In the re-melting process in electric arc furnace (EAF) of steel, zinc is vaporized, separated from steel, and generated as EAF dust. So, zinc can come back into the zinc cycle again. On the other hand, when zinc is used in copper alloys, zinc is not recycled as zinc but mixed into copper cycle. The mass balances of zinc in the substance flow analysis were verified by comparing estimated values of the model with statistics and other estimation at the recovering processes of zinc. Using this model, in-use stock of zinc in Japan was estimated as approximately 330 kt in 2005, which was about five times as much as recovered zinc. The amounts of unrecovered zinc in 2005 were estimated as around 190 kt. Of these losses, 70% were unrecovered in the steel cycle, e.g. dissipated into environment as sacrificial materials or with uncollected steels. Finally, complete zinc flows in Japan were determined with the results of this model.