Feasibility Study and Technical Report - Pretivm

13.3.10 SOLIDS LIQUID SEPARATION TESTS WORKIn 2012, Pocock Industrial conducted solids liquid separation (SLS) tests on the flotationconcentrate and flotation tailings samples. The test program included sample particlesize analysis, flocculants screening and evaluation, static and dynamic thickening tests,pulp rheology, and filtration studies.The results of the thickening tests are summarized in Table 13.32, Table 13.33, andFigure 13.29. To enable the best performance for both flotation concentrate andflotation tailings, Hychem AF 304 was selected as the flocculant, which is a medium tohigh molecular weight anionic polyacrylamide, with a 15% charge density.A concentration of approximately 20% is recommended for the flotation concentratethickener feed solids. Using a conventional thickener under the recommendedconditions, the unit area for the concentrate is in the range of 0.19 to 0.24 m 2 /t/d, whilethe underflow solids concentration is from 68 to 72%.Pocock recommended a concentration of approximately 10% for the tailings thickenerfeed solids. Using a conventional thickener under the recommended conditions, the unitarea for tailings is within the range of 0.43 to 0.48 m 2 /t/d, while the underflow solidsconcentration is in the range of 61 to 65%.The recommended hydraulic rate is 5.2 to 6 m 3 /m 2 /h for a high rate concentratethickener, and 4.2 to 5.0 m 3 /m 2 /h for a high rate tailings thickener.The maximum design thickener underflow density is suggested to 72% for theconcentrate and 65% for the tailings.Table 13.32Conventional Thickening Test Results for Flotation ConcentrateFeedSolids(%)CCDStageSimulatedDose(g/t)FlocculantConcentration(g/L)RiseRate(m 3 /m 2 /h)Maximum TestDensity(%)Time(min)SolidsDensity(%)Unit Area(m 2 /t/d)20 Stage 1 30.0 0.1 6.31 75.7 120 68 70 72 0.21 0.22 0.2420 Stage 1 35.0 0.1 6.83 76.3 120 68 70 72 0.19 0.20 0.2120 Stage 2 30.0 0.1 6.49 75.1 120 68 70 72 0.19 0.21 0.2220 Stage 3 25.0 0.1 6.35 74.4 120 68 70 72 0.19 0.20 0.2120 Stage 1 40.0 0.1 5.26 75.7 150 68 70 72 0.18 0.20 0.2125 Stage 1 35.0 0.1 2.28 76.9 120 68 70 72 0.20 0.21 0.2325 Stage 2 30.0 0.1 2.10 76.4 120 68 70 72 0.21 0.23 0.2425 Stage 3 25.0 0.1 2.27 74.4 120 68 70 72 0.20 0.22 0.2330 Stage 1 35.0 0.1 1.37 77.3 180 68 70 72 0.32 0.35 0.3830 Stage 2 30.0 0.1 1.26 75.7 180 68 70 72 0.31 0.34 0.3730 Stage 3 25.0 0.1 1.20 76.5 180 68 70 72 0.32 0.35 0.38Notes:Flocculant (Hychem AF 304) is a medium to high molecular weight anionic polyacrylamide, with15% charge density.CCD = counter current decantation.Pretium Resources Inc. 13-50 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC