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FLSmidth USA,Inc. <br /> 7158 S FLSmidth Drive • Midvale • UT 84047-5559 • USA L% M ' D T H <br /> 7.0 Conclusions and Recommendations <br /> Ouray contracted FLSmidth USA Inc. (FLS) to conduct thickening, rheology, and pressure <br /> filtration tests on zinc rougher tailings sample for their Revenue Mine project. FLS <br /> completed testing in their Separations Laboratory located in Midvale, Utah during April <br /> 2017. <br /> 7.1 Thickening Results <br /> Thickening objectives were accomplished by determining feed well design criteria related to <br /> effective feed conditioning for flocculation, conducting settling tests to determine sizing and <br /> design criteria, and by measuring thickened mud rheology to determine the required rake <br /> torque and predict underflow manageability. <br /> The results of the thickening tests show that an anionic polyacrylamide flocculent with a <br /> very high molecular weight and medium charge produce the best overflow clarity and <br /> settling velocities. FLSmidth used SNF AN-926VHM at 20 to 25-g/t dosage during the testing <br /> campaign. <br /> Flux testing showed the optimum feed well suspended solids concentration for flocculation <br /> to be 10 to 12-wt%. Dilution to the target feed solids concentrations can be achieved using <br /> the FLSmidth E-DUC° feedwell system and would not require additional water to the <br /> system. <br /> Thickening test results produced an underflow solids concentration of 60-wt% for a <br /> High-Rate thickener technology. Table 8 shows a summary of the thickening tests and <br /> recommended sizing. <br /> Table 8: Summary of Thickener Test Results & Recommended Sizing <br /> TEST CONDITIONS Tailings <br /> Recommended Feed Solids Conc. wt% 10-12 <br /> UNDERFLOW CHARACTERISTICS <br /> Design Underflow Solids wt% 60 <br /> Min. mud residence time required, hrs 0.5 <br /> Recommended Yield Stress for Rake Design, Pa <30 <br /> OVERFLOW <br /> Overflow clarity, m <200 <br /> FLOCCULANT <br /> Recommended Flocculent AN-926VHM <br /> Recommended Total Floc Dose, /t 20-25 <br /> THICKENER SIZING <br /> Minimum Recommended Unit Area mz/t d 0.04 <br /> Maximum Recommended Rise Rate m/h 16 <br /> 7.2 Filter Press Results <br /> Filtration objectives were accomplished by evaluating bench-scale filter press testing. The <br /> testing offered sufficient data to determine full-scale filter sizing for zinc rougher tailings <br /> stream. <br /> Filtration testing used a feed solids concentration of approximately 60-wt% as prescribed by <br /> thickening and rheology test work. <br /> Page 1 21 <br />