Manufacturer and distributor of mineral processing, magnetic and
vibratory equipment Eriez Magnetics, of Johannesburg, supplies
magnetic separation equipment which improves grinding-circuit
efficiency in all ball and semi-autogenous (Sag) milling
applications.
Its trommel and trunnion magnets have been applied in both Sag and
ball-milling circuits, and have improved the grinding circuit’s
efficiency by removing useless grinding-ball fragments from the
circulating load.
Sales and marketing director Michael Lawrenson says that
grinding-ball fragdesigner crusher jaw platesments discharged from Sag and ball mills cause
extreme wear to downstream processing equipment such as sumps,
pumps, hydrocyclones and interconnecting piping.
These fragments contribute little to the grinding process and their
removal results in several bcrushing manganese ore test resultsenefits in the milling circuit, which
include extending the pump and hydrocyclone life by about 250%,
increasing the throughput of the mills by 5% and reducing power
consumption in the mills by 10%.
„A typical ball-mill circuit will circulateportable gold track rock crusher more than a hundred
tons of grinding-ball fragments. This not only consumes power, but
causes extreme wear to process equipment in the milling circuit
and, in severe cases, can result in unscheduled maintenance and
downtime,“ Lawrenson says.
The comparock crushing equipments priceny has an extensive manufacturing facility in
Johannesburg, and has manufactured trunnion magnets which have been
successfully installed at Rosh Pinah in Namibia and the Freda
Rebecca mine in Zimbabwe.
Another trunnion magnet is on its way to the Morila gold-mithe advantages of roll crusherne in
Mali.
Eriez Magnetics‘ separation system, removing grinding-ball
fragments from the mill discharge, were first applied at the
Escondida copper concentrator in Chile in 1996. Called a trommel
magnet, this magnetic separator consists of an arc of permanent
magnets mounted at the discharge end of the trommel screen.
The magnetic arc of the trommel magnet attracts and removes the
grinding-ball fragments from oversized ore in the trommel screen,
allowing the oversized ore to return to the circuits for
processing. The first trommel magnet tested at Escondida removed
126 tons of grinding-ball fragments from the circulating load in
the initial 24 hour period.
After several days, the mill stabilised, and the magnetic separator
currently removes ball fragments roughly equal to the new charge
addition a day.
The design of the trommel magnet separator was further developed to
remove grinding-ball fragments directly from the entire mill
discharge, without the prior trommel screen. This led to the
development of the trunnion magnet, which also consists of an arc
of permanent magnets, but is mounted directly at the discharge
trunnion of the ball mill.
„The trunnion magnet has proved to be effective for removing all
the different sizes of grinding-ball fragments,“ Lawrenson says.