Feasibility Study and Technical Report - Pretivm

17.1.4 PLANT DESIGNMAJOR DESIGN CRITERIAThe process plant is designed to process 2,700 t/d, equivalent to 985,500 t/a. Themajor criteria used in the design are outlined in Table 17.1.Table 17.1Major Design CriteriaCriteria Unit ValueDaily Processing Rate t/d 2,700Operating Days per Year d/a 365Operating Schedule - two shifts/day; 12 hours/shiftMill Feed Grades – Average g/t Au 10 to 15g/t Ag 40 to 100% S 3Metal Recovery – Doré % Au 30 to 50% Ag 1 to 20Metal Recovery – Flotation Concentrate % Au 50 to 70Primary Crushing (Underground)% Ag 70 to 92Crushing Availability % 65Crushing Product Particle Size, 80% passing mm 120 to 150Grinding/Flotation/ Gravity ConcentrationAvailability % 92Milling and Flotation Process Rate t/h 122SAG Mill Feed Size, 80% passing mm 120 to 150SAG Mill Grinding Particle Size, 80% passing µm 1,070Drop Weight Breakage Parameter Axb 41.4Ball Mill Grinding Particle Size, 80% passing µm 74Ball Mill Circulating Load % 300Bond Ball Mill Work Index kWh/t 16.0Nugget Gold Recovery from Primary Grinding Circuit - Centrifugal and Tabling Gravity ConcentrationRougher Flotation Concentrate Regrinding ParticleSize, 80% passingµm 35 to 40Nugget Gold Recovery from Reground Concentrate - Centrifugal and Tabling Gravity ConcentrationUpgrading of Gravity Separation Concentrates - Direct SmeltingOPERATING SCHEDULE AND AVAILABILITYThe process plant is designed to operate on the basis of two 12-hour shifts per day,365 d/a. The overall availability for the underground primary crusher circuit will be 65%.The grinding, flotation, and gravity concentration availability will be 92%. The gold roomwill be operated during the day shift only. These availabilities will allow for a potentialincrease in crushing rate, downtime for scheduled and unscheduled maintenance of thecrushing and process plant equipment, and potential weather interruptions.Pretium Resources Inc. 17-5 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC