複雑硫化鉱酸化焼鉱の選択還元焙焼

複雑硫化鉱の製錬に関する研究 (第7報)

抄録

Studies were made on the reduction roastings of dead-roasted complex sulfide are and the dilute sulfuric acid (0.4N) leaching of the reduction-roasted calcine for a purpose of separation of metallic copper from zinc oxide, both of which were contained in the calcine.
In case that the extent of the reduction was so insufficient that iron oxide was not entirely reduced to FeO and Fe₃O₄ remained in the calcine, the separation was not attained on account of dissolution of the metallic copper. The copper dissolution is caused by an oxidizing effect of Fe³⁺-ion which forms when the magnetite dissolves into the leaching solution in the presence of metallic copper.
Copper dissolution and zinc extraction were 20% and 95% respectively, when calcine, which was roasted by means of a batch-type rotary kiln of a laboratory scale for 2 hours at 850°C in an atmosphere composed of 10% CO, 10% CO₂ and 80% N₂, was treated with 0.4N H₂SO₄.
Coke was inadequate as a reducing agent for this purpose, because it could not reduce Fe₃O₄ to FeO at 850°C
It was also ascertained that a considerable amount of zinc oxide vaporized in a weakly reducing atmosphere even at 750°C. This unexpected fact was resulted from formation of zinc vapour as a reduction product of ZnO by CO.