|
The Havercroft Andalusite Mine process plant.
Andalusite crystals recovered at Havercroft and a specimen of host rock.
Three sizes of crystals smaller than 8 mm in size are recovered.
|
Andalusite process plant at Havercroft mine
A process plant to handle 88 000 tonne/month at Anglovaal Minerals
Limited’s (Avmin’s) newly re-opened Havercroft Andalusite
mine was commissioned following its upgrade and refurbishment by BATEMAN.
The mine is located near Burgersfort, Northern Province, RSA.
A reimbursable R37M (about US$7M) contract covered the project management,
engineering design and supply of the new processing plant together with
those parts of the plant which could be refurbished.
Primary crushing of 150 t/h of run-of-mine (ROM) ore is accomplished
using an innovative adaption of underground coal mining technology to
process the hard andalusite crystals in the relatively soft shale matrix.
Secondary crushing occurs in a refurbished Omni-cone crusher and tertiary
crushing is achieved using a novel wet flush crushing technique liberating
the andalusite crystals with a minimum of breakage.
The andalusite is then concentrated by gravity separation in a dense
media separation (DMS) plant consisting of two modular units. The modern
design of the plant results in enhanced separation efficiencies and
permits the recovery of smaller crystals than was possible in the past.
Final upgrading of the andalusite is accomplished by drying the concentrate
in a rotary dryer followed by the reduction of the iron content by passing
the crystals through Permroll high intensity magnetic separators.
Plant tailings comprise coarse discards and slimes. The coarse material
is conveyed up the existing dump which was stabilized by extensive re-grading.
The slimes are thickened in an Ultra Hi-rate thickener and pumped to
the existing slimes dam 1,5 km below the plant.
Process control is fully automated using a modern SCADA (supervisory
control and data acquisition) system allowing the whole plant to be
operated by one operator and four assistants, with a clear view of the
whole plant from a centralized control room above the motor control
centre (MCC). Two wet scrubber systems ensure that dust emissions from
the plant are well within legislated limits.
The original plant built in the 1950s consisted of a 150 t/h crushing
and screening plant followed by pre-concentration in pans and a DMS
plant. It was operated by VEREF (Vereeniging Refractories) until the
late 1980s when it was acquired by Amcoal. In turn, the mine was sold
to Avmin which closed it down in 1991.
Following a favourable increase in the price of andalusite, a test programme
was initiated at Mintek in early 1996 and BATEMAN was awarded a feasibility
study which examined a number of modern processing options. This study
rolled over into the plant modernization project.
The new plant was built within eight months and is now operating according
to specification, 24 hours a day, 6 days a week.
For further details please contact Mark Cresswell, Process Manager,
on +27-11-899-2856, or email markc@bmi.co.za
VIEW
PDF
|
