2011-09-27_REVISION - M1990057 (10)

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Reagents Lime PAX Water Rate Ore feed Amount used (2) Amount used (3) 12.51b /ton (1) 56,000 tons /yr 350 tons /yr - 1.91b /ton 56,000 tons /yr 5.4 tons /yr - 0.8st H 56,000 tons /yr 45,700st/y Future Crushing Circuit The planned additional crushing facility and storage silo, allows RoM ( -6 ") to be dumped directly from the OTR trucks into a 1000 ton capacity coarse ore bin prior to feeding the crusher circuit. Utilizing a similar grizzly, screening, primary and secondary crusher system, the material flow will be in the range of 50% screened and sent to the silo and 50% sent to the primary and secondary crushers, recombined with the screened material and sent to the silo. The storage silo feeds an enclosed overhead belt, conveying the crushed material directly to the grinding/flotation building fine ore bin, by- passing the existing crushing facility. The future crushing circuit also has a truck scale, which allows the mill facility in -house weighing capability. Grinding Circuit Material from the fine ore bin is transported to the grinding circuit via a belt feeder. Lime, Ca(OH)2, is also added to this stream to bring the pH level to 10, as needed, to increase metal recovery. This is a wet grinding circuit. This grinding circuit is comprised of one, 5 ft diameter x 4 ft long Marcy ball mill. The ball mill, as it is configured at present, has a 40 hp motor. This mill is capable of processing a maximum of 8 ton/hr. The grinding system operates in closed circuit with a classifier to produce a final flotation feed. The oversize reports back to the ball mill with a 180% circulating load for 8 tons/hr feed. The underflow will be fed to the rougher flotation circuit. Water is added at the ball mill discharge trough. Reagents are added at the ball mill and the conditioning tank through reagent feeders. As shown in Table C -1, lime is added at the grinding mill to control pH. Potassium amyl xanthate (PAX) is added as a promoter at the grinding mill for increased reagent reaction time. The lime is added through a dry reagent feeder and the PAX is a 1% solution, mixed on site from pellets. Reagent usage added at the grinding circuit is presented in Table C -1. Emissions are generated when the dry chemicals are added to the reagent mixers. Negative pressure ventilation collects fugitive pm emissions from the reagent mixing area. The same dust collector in the crushing and conveying circuit captures the emissions. Table C -1: Chemical Usage, Ball Mill (56,000 ton /yr "' Reagent rate based on dry ore feed tonnage (2) Dry US tons of reagents — annual quantity (3) Liquid US tons of reagents — annual quantity Flotation Circuit The comminution product reports to the rougher floatation circuit where it is mixed with water to achieve a density of 35% solids by weight, which is carried through to the scavenger and cleaner circuits. The rougher flotation cell bank consists of six, 25" x24" x29" (60.4ft tank cells. Tails from rougher flotation will report to the scavenger flotation circuit which consists of six, 25" x24" x29" (60.4ft tank cells. Tails from the scavenger flotation circuit report to the tails thickener. M1990 -057 September 27, 2011