GB800643A - Improvements in fluid bed roasting of zinc ores - Google Patents

Abstract

<PICT:0800643/III/1> Cadmium and/or lead components of zinc sulphide are concentrates, of particle size 4 to 65 mesh, are recovered by charging ore to a mildly agitated fluid bed 1 which is in direct contact with a more actively agitated bed 2 which is of substantially smaller cross-section (e.g. one-quarter of the size) and fluidizing with oxidizing gas through at least the single line 3 and optionally through lines 4 and 5 connected to the lower bed, the quantity of gas being such as substantially no oxygen remains in the SO2 gas rising to the upper bed. The zinc sulphide concentrate fines are premixed with a binder, e.g. bentonite, zinc sulphate, or sulphate liquor, agglomerated and formed into pellets. The roasted ore is discharged from the lower bed though part may be recycled to the lower bed while cadmium and/or lead as sulphides are recovered from the roasted gases of the upper bed at 6. A minor proportion of carbonaceous material may be added to the ore concentrate. The process also eliminates any antimony, arsenic or tin compounds present. Specification 661,560 is referred to.