黒鉱製錬煙灰の湿式処理法の確立

抄録

Kosaka smelter, located at Akita prefecture in Japan, has treated the copper concentrates which come from “Black ore” mines with the flash smelting furnace since 1967.
The copper concentrates contain various impurities such as lead, zinc, arsenic, antimony, bismuth and cadmium which are concentrated in the dusts of flash smelting system.
These impurities had been recycled to the system and caused some problems on the practical operation, the quality of final products and the environmental control.
In 1975, new hydrometallurgical dust treatment plant started up its operation and made it possible to solve these problems and to increase profit by recovering valuable metals from the dusts and the zinc residues which were stored at the smelter.
The basic steps of this hydrometallurgical process are as follows:
1) Leaching of the dusts by waste sulfuric acid from acid plant and next by ferric solution which is prepared by hot acid leaching of zinc residues.
2) Filtration and drying of lead sulfate which contains bismuth, antimony and precious metals followed by the lead smelting with one short rotary furnace.
3) Copper precipitation by hydrogen sulfide gas and iron powder.
4) Coprecipitation of arsenic with iron as ferric arsenate.
5) Zinc and cadmium precipitation by ammonia and hydrogen sulfide gas, respectively.