Cominco's Trail zinc pressure leach operation

CIM Bulletin, Vol. 78, No. 876, 1985

M.T. MARTIN Superintendent, Zinc Pressure Leach, W.A. JANKOLA, Development Engineer, Cominco Ltd., Trail, B.C.

The world's first zinc pressure leaching plant at Cominco's Trail operations started production in 1981. Sullivan zinc concentrate is leached at the rate of 190 tpd in a four-compartment autoclave at elevated temperatures and oxygen pressures to produce a zinc sulphate solution and elemental sulphur. Zinc extraction exceeds 98% and sulphide to elemental sulphur conversion exceeds 95%. The sulphur is recovered from the discharged slurry in the underflow of a hydrocyclone, and is upgraded as a flotation concentrate. The concentrate is dewatered, melted and filtered to produce a polished sulphur product of better than 99% purity. An alternative sulphur recovery process employs an unique sulphur separation method that recovers over 90% of the sulphur in the molten state. The remaining sulphur is recovered by flotation following flash discharge of the slurry. The product slurry containing the zinc sulphate solution and the iron-lead residue joins the existing roast-leach zinc plant for purification and zinc electrowinning.

Keywords: Extractive metallurgy, Zinc pressure leaching plant, Zinc, Pressure leaching, Sulphur recovery, Flotation.