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' ~ + • II I' II I I I I II I III'll • <br />To: Ron Zumwalt <br />From: Richard Neu <br />Subject: March Metallurgical Report <br />Date: April 10, 1992 <br />Grinding <br />Monthly mill tonnage was 138,355 tons or 4,463 tons/day. Mill <br />availability was 89.1$. Operating tonnage averaged 209 tons/hr. <br />The 80$ passing size (p80) of the sag mill product was finer at <br />536 microns. The p80 of the ball mill product remained the same <br />at 123 microns. Bond work index of the ore slightly increased to <br />19.90 kw-hr/ton. Ball mill motor temperatures have been increasing <br />due to warmer ambient temperatures. Additional motor cooling is <br />being investigated. Until then, the ball charge may have to be <br />slightly reduced to keep motor temperatures down. Cyclone u'flow <br />return to the Sag Mill remains under investigation. Minproc has <br />recommended increasing Sag Mill density to 75 - 80$ to improve <br />throughput and grinds. The current setpoint is 70 - 75$. Ball <br />mill ball make-up has been changed to 20$ - 4", 32$ - 3", and <br />48$ - 2" balls. Anew polyurethane screen panel has been developed <br />with significantly shorter slots. This type of screen may <br />significantly reduce wood fibre passage through the trash screen <br />and should be tested. <br />Thickening <br />Flocculent consumption remained about the same at 0.18 #/ton. <br />Flocculent feed points remain to be optimized. Thickener underflow <br />density continues to increase with an improvement in steady state <br />operation. <br />Leaching and Carbon-in-Leaching <br />All grades listed below are expressed in oz/ton solids. <br />Au Aq <br />Mill Report Grade .042 .121 <br />Production Grade .044 .090 <br />Mill Report Solid Tail .007 .069 <br />Mill Report Solid Recovery 82.6 43.0 <br />Production Solid Recovery 83.4 23.3 <br />Mill Report Solution Grade .0022 .010 <br />Mill Report Total Recovery 78.5 37.7 <br />Production Total Recovery 79.5 17,6 <br />