Study of the compound water cyclone's concentrating efficiency of free gold from placer material*

CIM Bulletin, Vol. 81, No. 919, 1988

DANIEL E. WALSH and P.O. RAO,Mineral Industry Research Laboratory,University of Alaska-Fairbanks,Fairbanks, Alaska

A four-inch compound water cyclone (CWC) was tested to evaluate its gold recovery characteristics when processing -4.8 mm run-or-pit, placer material. Neutron activated placer gold particles (840 to 37 microns) were used as radiotracers (198Au) in a closed circuit CWC test loop to determine concentrator recovery; a procedure believed unique to this study. The effect on gold recovery of gold size and shape, feed pulp density, feed pressure, vortex finder clearance (VFC), CWC cone type, top-size of the feed solids, presence or absence of heavy minerals in the feed, and the quantity of-37 micron slimes in the feed was investigated in over 300 tests. CWC concentration ratio and the top-size of the underflow solids were both affected by cone type, VFC, and feed pressure. Gold recovery was significantly affected by gold size, gold shape, and concentration ratio. These effects are complex, because significant size-concentration ratio and size-shape interactions exist. Radiotracer techniques showed gold particles had a residence time within the CWC of approximately one second. This study suggests CWC gold recovery is a concentration. This work suggests CWC gold recovery is a function of particle size and shape, and the flow rate through the cyclone. CWC cone "bed density" is considered important only as a thin, protective layer, which shields coarser gold particles from the entraining currents and facilitates their movement through the CWC.

Mots Clés: Mineral processing, Compound water cyclone, Gold recovery, Placer gold, Concentrators, Beneficiation, Radiotracer.