Pulacayo Project Feasibility Study - Apogee Silver

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Pulacayo 1 000 t/d Phase I Feasibility Study - NI 43-101 Technical Report 090644-3-0000-20-IFI-100 Sample Cycloning (Desliming) (-) Classification 149 µm (100#) Underflow (+) Pb-Ag Conditioning (Collector/Frother/Depresor /pH Regulator) Milling Pb-Ag Rougher Flotation Tails Conc Pb-Ag Cln N 2 Tails Pb-Ag Cleaner N 1 Flotation Conc Pb-Ag Cleaner N 2 Flotation Zn-Ag Conditioning (Collector/Frother/Activator/ pH Regulator Conc Zn-Ag Rougher Flotation Pb-Ag Cln N 1 Tails Zn-Ag Ro.Tails To Quarter Particle Size Analyses (PSD) Sedimentation Test Zn-Ag Cln N 2 Tails Conc Zn-Ag Cleaner N 1 Flotation Conc Zn-Ag Cln N 1 Tails To Cycloning Zn-Ag Cleaner N 2 Flotation Zn-Ag Conc Pb-Ag Conc. Overflow (Clays) Figure 13.2 Locked Cycle Test (LCT) Flowchart – Desliming Step The locked cycle flotation (LCT) test results, corresponding to the High Grade (LA) sample (grind size of d80 150 µm), indicate that conventional selective lead-silver and zinc-silver flotation techniques are able to recover almost 56% of silver in the lead concentrate (with a mass pull of 2.39%) and 26.7% of silver in the zinc concentrate (with a mass pull of 3.76%). The lead and zinc concentrate grades are 52.4% and 57%, respectively. Also, the lead and zinc recoveries are estimated as 78.8% and 81.1%, respectively (Test no 1). The silver grades in the lead and zinc concentrates were reported as 6,620 g/t and 2,010 g/t, respectively. These results are further improved by proceeding with a cyclone desliming step ahead rougher flotation (see Figure 13.) to reduce the amount of slimes in the feed (Test N° 2). However, around 8.5% Ag is lost in the slimes fraction or discarded overflow (18.7% in weight). Native silver occurs as fine particles of size smaller than 20 µm. Lime consumption is reported to be as high as 19.3 kg/t. Similarly, the locked cycle flotation (LCT) tests results corresponding to the Medium Grade (LM) sample (grind size of 150 µm), indicated that it is possible to recover almost 33.6% of silver in the lead concentrate (with a mass pull of 1.2%) and 49.8% of silver in the zinc concentrate (with a mass pull of 3.7%). The lead and zinc concentrate grades are 51% and 58.3%, respectively. Also, the lead and zinc recoveries are estimated as 74.3% and 82.6%, respectively (Test no 3). The silver grades in the lead and zinc concentrates were reported as 6,220 g/t and 2,990 g/t, respectively. TWP Sudamérica S.A. Av. Encalada 1257 Of. 801, Santiago de Surco Lima 33, Perú (51-1) 4377473 Page 103
Pulacayo 1 000 t/d Phase I Feasibility Study - NI 43-101 Technical Report 090644-3-0000-20-IFI-100 These results are further improved by proceeding with a cyclone desliming step ahead rougher flotation (see Figure 13.2) to reduce the amount of slimes in the feed (Test N° 2). However, around 9.9% Ag is lost in the slimes fraction or discarded overflow (20% in weight). Native silver occurs as fine particles of size smaller than 20 µm (see section 13.3.2). The Low Grade (LB) sample with a grind size of d80 150 µm, the LCT results shows that the differential flotation is able to recover almost 30% of silver in the lead concentrate (with a mass pull of 0.53%) and 20.9% of silver in the zinc concentrate (with a mass pull of 1.28%). The lead and zinc concentrate grades are 46.7% and 44.8%, respectively. Also, the lead and zinc recoveries are estimated as 34.6% and 50.9%, respectively. The silver grades in the lead and zinc concentrates were reported as 2,600 g/t and 749 g/t, respectively (Test N° 1). Lead recovery was low with a substantial amount of the zinc tied up in the lead circuit cleaner concentrate. These results are further improved by proceeding with cyclone desliming step ahead rougher flotation to reduce the amount of slimes in the feed (Test N°2 and Test N° 3). However, 5% to 11% Ag is lost in the slimes fraction or discarded overflow (27% and 26% in weight). Native silver occurs as fine particles of size smaller than 20 µm (see section 13.3.2). The lime consumption is reported to be as high as 14.3 kg/t. It is not clear from the test work data and reports the extent to which this closed circuit test approached the locked cycle test standards commonly used in the industry. There is no information on how many cycles were performed (usually six) and whether circuit stability was reached as the circulating loads of middlings approached a sort of equilibrium. The most likely consequence of not attaining equilibrium is that concentrate grades may be overestimated and recoveries under-estimated. However, the results seem to be reasonable and in accordance with expectations from the mineralogy of the ore. Further testing was undertaken by ED&ED and their findings are shown later. These results constitute the design basis for the flow sheet. Full open-circuit tests (OCT) of sulphide minerals flotation were conducted initially on each sample as a proof of concept of the overall circuit and to establish a workable set of flotation conditions and reagents. These test demonstrated that sulphide flotation to saleable lead and zinc concentrates at acceptable (for batch tests) recoveries was possible. OCT flotation flow sheet was developed incorporating a moderate grind size of 150 µm (P80). The pH in the lead rougher circuit was elevated to a value in the range of 9 to 10 using lime. The pH in the zinc rougher circuit was maintained in the range of 10 to 11. AF-242 and Z-11 were used as the lead and zinc collectors, respectively. A regrind step to produce high grade concentrate was not considered. In the lead flotation circuit, Sodium Cyanide (NaCN) and Zinc Sulphate (ZnSO 4 .7H 2 0) were used as pyrite and sphalerite depressors, respectively. The pH of the cleaning stages in the lead concentrate was maintained at the range of 9 to 10 using lime. The pH in the zinc circuit cleaning stages was elevated to activate spharelite and lime was used to raise the pH to above pH 10 to depress iron (pyrite). According to the mineralogy studies carried out by ED&ED (see section 13.3.2), galenasphalerite assemblage (intertwined specimens) is present at some extend. This may be reason for some not desired zinc content in the lead concentrates. In addition, unwanted TWP Sudamérica S.A. Av. Encalada 1257 Of. 801, Santiago de Surco Lima 33, Perú (51-1) 4377473 Page 104
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Pulacayo Project Feasibility Study - Apogee Silver

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