| 摘要 |
<p>ZnO and SO2 are obtained by passing 1/2 -inch pellets of a ZnS ore concentrate down through a furnace having an upper zone at 1150 DEG C. where impurities, e.g. Cd and Pb sulphides, are volatilized, and a lower zone at 900-1025 DEG C. to which excess O2 is supplied, and where the ZnS is roasted to ZnO, the SO2-containing roast gases passing to the upper zone to form the required non-oxidizing atmosphere there. The ZnO pellets are used as feed in an electrothermic reduction furnace. The ore concentrate is initially ground, e.g. in a ball-mill, optionally with recycled Zn materials, e.g. reduction furnace fines (screen analysis is given); binding agents, e.g. bentonite, and Zn sulphate liquor, may then be added, and the mixture is pelletized in a rotating drum and then dried with hot air. The pellets may have a residence time of 13 hours in the furnace, and moisture may be present in the first zone. The hot pellets may be cooled by heat-exchange with the feed air, and hardened at 1225 DEG C. The hot gases may be passed through waste heat boilers; Pb and Cd values are recovered by electrostatic precipitation and wet-scrubbing, and SO2 is converted to H2SO4.</p> |
