製鋼ダストからの製品亜鉛華の製造とその事業化について
1996 年 112 巻 10 号 p. 670-674
詳細
1996 年 112 巻 10 号 p. 670-674
Recovery of such valuable metals as zinc, lead and iron from steelmaking dust is, in other words, treatment of industrial wastes. The basic requirement in its implementaion is, therefore, not to generate another type of wastes from this operation.
1. Using the St. Joe process, Toho Zinc Co., Ltd. had established the technology to recover zinc, in the from of zinc oxide, contained in leaching residues generated from electrolytic zinc refining. In this process, zinc is vaporized in the strong reduction atmosphere in the vertical electro-thermic furnace. The remarkable feature of this technology is that most of iron content in the clinker, which is generated from the process as final waste, is metallic and thus can be recycled as iron raw meterial.
2. In the meantime, to manufacture chemical grade zinc oxide from steelmaking dust, it was necessary to combine the St. Joe process with an additional technology aimed to remove impurities.
3. Theory of selective choridizing vaporization during the roasting process had been established as such additional technology, however, this theory had never been applied to manufacturing in any industrial scale. To implement the theory in the industrial scale, we conducted a fundamental test using a boat as well as two feasibility tests using rotary kilns with the dimensions of 0.43m.I.D.×10.8mL and 1.8m.I.D.×25mL, respectively. As a result of a series of tests, we concluded that the technolgy of selective chrolidizing roasting of lead, cadmium, etc. is feasible, and implemented the commercial production.
4. Favorable results are being obtained in the oxidzing atmosphere at the temperature of 1100-1150°C in the rotary kiln with the dimension of 2.5m.I.D.×38mL. More than 95% of lead is vaporized and quality of zinc oxide produced is found satisfactorily stable.
5. The chemical grade zinc oxide plant was installed in 1974 in the Onahama factory to treat steelmaking dust. The plant is currently treating approximately 50, 000-60, 000 tons of dust annually to produce 16, 000 tons of chemical grade zinc oxide per year.
6. The above achievement is the result of renovation in our technology and rationalization at our plant over the past 22 years. We are committed to continuing steady efforts to make further progress in such areas as recovery and utilization of heat energy, the rate of recovery of valuable metals, and quality of the product.
