Roasting of arsenopyrite gold-bearing ores

摘要

Arseno-pyrite gold-bearing ore solids are roasted by fluidized-solids technique firstly in a bed in which the amount of oxygen in the fluidizing gas is sufficient to oxidize the ore to yield volatile arsenic compounds (arsenious sulphide and oxide), but insufficient to yield non-volatile arsenic compounds (arsenic pentoxide), and then in a bed in which the oxygen-bearing fluidizing gas is sufficient for complete oxidation. The solids are thus rendered particularly amenable to cyaniding. As shown, finely divided ore is fed into a refractory-lined vessel to form a bed 17 and after the preliminary roasting therein, at a temperature above 450 DEG C, but below that causing fusion, passes through pipe 19 to the second bed 18 whence after being roasted, suitably at 625 DEG C, but below fusion, it is discharged through pipe 29. In starting the process, air is supplied through conduit 40 together with natural gas, &c., or liquid fuel may PICT:0677050/III/1 be supplied through pipe 70, and inert material is fed to the beds. When a temperature of 800 DEG C is reached, the inert material is replaced by ore, and the auxiliary fuel is shut down. The oxidizing gas passes from the lower to the upper bed via a cyclone 51, and from the upper bed to cyclone 36, whence dust is passed via pipe 57 to the lower bed. The temperature may be controlled by water sprays 72.