Testing Requirements & Insight for Gravity Gold Circuit Design
A.R. Laplante; McGill University, Montreal
Presented at Randol Gold & Silver Forum 2000
April 21st, 2000
Gold gravity recovery has evolved significantly over the past twenty years, largely because of the advent of the Knelson Concentrator. A number of graduate students at McGill University have completed largely applied research on ore characterization (Woodcock, 1994), evaluation gravity circuit of gravity circuit performance (Putz, 1994; Vincent, 1997, Zhang, 1998), or the fundamentals of semi- batch centrifuge operation (Buonvino, 1993; Ling, J., 1998; Xiao, 1998; Huang, 1996).
For characterizing gravity recoverable gold (GRG) in ores, the McGill University test was developed in the early 90s and used for over 70 ore samples. The test uses a representative feed as small as 30 kg for high-grade, finer gold, and as large as 150 kg for low grade, coarser gold. The feed samples are composited from drill core of primary (rod, Sag) mill discharge, or screen or screw classifier undersize when primary mills are operated in closed circuit. When plant samples are used (for retrofit or optimization studies), they are usually composited over a full month, to average out day-to-day variations.
The test itself consists of a sequential liberation and recovery with a 3-in Knelson, first at 100% finer than 850 um (stage 1). A second stage follows, at 45 to 60% passing 75 um, with part of the tailing of stage 1 as feed, typically 27 kg. A third stage follows, at final grind (typically 80%-75 um), using most of stage 2 tailing as feed, typically 24 kg. Details are presented elsewhere (Woodcock, 1994; Woodcock and Laplante, 1993). Of interest here are “simplified” tests that were completed by grinding to final size and processing with a 3-in Knelson, either once or three times (since the original GRG test has three recovery stages). The following findings emerged....
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