Ore processing
Ore processing is a term used to
describe the process of taking ore (mineralised rock from the
earth) and turning it into a metal. In the case of Northparkes we
are processing this ore into copper, gold and silver.
Crushed Ore
Handling
There are two coarse ore stockpiles receiving material
from the surface and underground crushers. The total capacity of
each stockpile is 150,000 tonnes. Crushed ore is reclaimed by four
vibrating feeders under each stockpile.
Grinding
The grinding circuit is comprised of two separate modules, each
incorporating a Semi Autogenous Grinding (SAG) mill, oversize
crushing technology, two stages of ball milling and flash
flotation.
Flotation
Flotation takes place in two parallel modules, each linked to its
own grinding circuit. The flotation process aims to float a
sulphide concentrate to recover the major copper and gold bearing
minerals. (The circuits consist of pre-float, rougher, scavenger,
cleaner, cleaner-scavenger and re-cleaner treatment).
The final concentrate produced for each module assays 34 - 36 per
cent copper and is pumped to a concentrate thickener. Final
tailings from each module are pumped to a tails thickener for
dewatering.
Concentrate Thickening and Filtration
Final concentrate from the flotation circuits is pumped to
thickeners where it is thickened to an average underflow density of
60 per cent solids. Thickened concentrate is then pumped to
concentrate storage tanks prior to treatment through the filtration
circuit, using ceramic disc filters.
The filtered concentrate is discharged onto slow moving conveyor
belts, each equipped with a weightometer to determine final
production of concentrate. The concentrate is conveyed into a
storage shed before loading and transporting to customers.
Concentrate Handling
Concentrate is removed from the storage bays using a front-end
loader, which loads concentrate into shipping containers carried on
a semi-trailer. The containers are sealed and trucked to the
Goonumbla rail siding 12km from the concentrator. The full
containers are loaded onto trains, with the carrying capacity of
each train up to 60 containers. Concentrate is railed to Port
Kembla for shipping to overseas customers.
Tailings Disposal
Three sets of slurry pumps, in parallel, pump the thickened
underflow tailings to either of the two tailings dams or E27
(in-pit tailings). Water is retrieved from a decant system and
returned to the plant.