Pulacayo Project Feasibility Study - Apogee Silver

Pulacayo 1 000 t/d Phase I Feasibility Study - NI 43-101 Technical Report
090644-3-0000-20-IFI-100
17.1.1 Crushing Area
Run of mine ore will be delivered from the underground mine to the process plant via
Gramby self-dumping cars through a railway system. The crushing area is situated on
surface 1.43 km from the adit. The ore is moved from the adit to the crushing area and
dumped onto a fixed grizzly with 400 mm bar spacings and into the coarse ore bin. Oversize
rock is broken by a JCB backhoe with a rock breaker attachment. Since the ore comes from
relatively small stopes, most of the rock is expected to be smaller than 500 mm.
From the 40 t coarse ore bin, ore is moved by a 6,600 mm by 760 mm apron feeder directly
into the primary jaw crusher. The primary crusher, a 500 mm by 750 mm single toggle jaw
type with a close side setting gap of 50 mm and installed with a 75 kW de-rated motor. The
crushed ore is discharged to a belt conveyor. A self-cleaning moving belt magnet and
fixed/static magnet on this belt removes tramp iron and a metal detector trips the belts
protecting the secondary cone crusher from tramp metal such as rock bolts or steel balls.
The conveyor belt dumps directly onto a 4,800 mm by 1,800 mm double deck primary
vibrating screen. The primary screen is provided with an upper deck screen of 25 mm and a
lower deck screen of 12 mm. Both screens oversize fractions pass through a secondary
cone crusher with a close side setting of 12 mm and equipped with a 200 kW de-rated
motor. Both screen decks have polyurethane screen panels, polyurethane weir bars spaced
at 900 mm intervals and four bar pressure spray nozzles wash the clays off the rock
particles. The 1,300 mm diameter cone crusher discharges onto conveyor belt from where it
is combined with the jaw crusher discharge and is returned to the screen (i.e. the cone
crusher is in closed circuit with the vibrating screen). Another alternative has also been
considered in which the primary screen is being replaced by a scrubber with a trommel at
the discharge end. The scrubber discharge goes to the secondary double deck screen while
the oversize material goes to the cone crusher. This option will be studied further during the
detail engineering stage.
The primary screen undersize bypasses the second stage cone crusher and feeds directly
onto the 4,800 mm by 1,800 mm double deck vibrating screen. Both screen decks have
polyurethane screen panels, polyurethane weir bars spaced at 900 mm intervals and four
bar pressure spray nozzles wash the clays off the rock particles. The dewatering screen will
have an upper deck screen of 6.5 mm and a lower deck screen of 0.4 mm. Oversize
fractions from the screen are transported to the two 1,000 t fine ore storage bins by a belt
conveyor. This crushed product has a nominal top size of 12 mm, 85% +6.5 mm and 14.5%
+0.4 mm.
Undersize fraction is directed to an in-line strainer (Tekleen filter, 600 kPa in-line pressure)
to retain the clayish material to clarify the water that will be used again in the circuit (high
pressure spray water and hosing water). The clayish fraction is directed to the ball mill
discharge pump box (or back to the dewatering screen if required).
The design operating rate for the crushing plant is of 83.3 t/h. At 1,000 t/d, the crushing plant
requires 12 hours per day operating time. The crushing circuit feeds (2) parallel milling
circuits (1 and 2) of the same design capacity.
TWP Sudamérica S.A. Av. Encalada 1257 Of. 801, Santiago de Surco Lima 33, Perú (51-1) 4377473
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