湿式法による高炉ダストからの亜鉛分離技術の開発

抄録

Blast furnace (BF) dust is recycled as iron source in sintering process. However, dust-recycling rate is limited due to the zinc in dust. Thus, it is necessary to remove zinc from dust in order to improve dust-recycling rate. In this study, zinc-separating process of BF dust using hydrometallurgical (wet-type) system is proposed with a zinc purification process. Laboratory-scale experiments using BF dust were conducted to investigate zinc and iron behavior. This process is composed of (1) acid leaching treatment, (2) leachate-purification process and (3) zinc-recovery process as alkali precipitation. By acid leaching treatment, 68 wt% of zinc was selectively leached into the solution under the pH value of 2.0 with sulfuric acid, while only 6.4 wt% of iron was leached. Leachate-purification process is the key process. The iron leached by acid leaching treatment was completely separated from leachate as iron hydroxide under the pH value of 5.0, added with hydrogen peroxide as oxidizing agent. On the other hand, zinc in leachate was maintained at the same level and well-purified successfully. Zinc was finally recovered as sludge of zinc hydroxide precipitation at alkali condition such as the pH value of 9.0. Zinc concentration in the sludge was concentrated to 42.6 wt%. With this new process, zinc in dust was successfully separated and the sludge containing high concentrations of zinc was obtained. Thus, dust can be potentially used as zinc source as well as iron source.