Chambishi cobalt - purification plant
BATEMAN was involved in the expansion of the cobalt- purification
plant for Chambishi Metals PLC, a division of AngloVaal Mining (AVMIN),
at the Chambishi site, 30 km north west of Kitwe, Zambia. Two process
plants, a belt-filter and a zinc solvent-extraction (SX) plant, as well
as new utilities and reagents sections, were added to the existing facilities.
The existing purification areas were upgraded with the installation
of extra tanks and improved agitation in existing tanks.
The Chambishi plant processes copper concentrate from mines on Zambia’s
Copperbelt. The contract commenced in April 2000 as a brown-fields project
to expand the capacities of the cobalt purification and associated utilities
and reagents sections from 2600 to 7000 t/yr of cobalt cathode. This
increased capacity was required to handle the additional feed of cobalt-sulphate
solution from AVMIN’s nearby COSAC project.
After roasting and leaching the concentrate, the copper is recovered
by electrowinning (EW). The stripped solution from copper EW, containing
cobalt, is then purified before cobalt is electrowon, crushed and degassed.
Initial designs focused on the method of precipitating the cobalt as
either a hydroxide or carbonate, and the latter was selected as the
route to bring the plant up to its new capacity. The precipitated cobalt
carbonate is recovered using the new belt filter. The resulting cake
is then re-dissolved in spent electrolyte and sent to the EW circuit
for recovery of the cobalt metal (LMB-Grade A).
Reagent handling facilities, including rock lime, quick lime, soda
ash and caustic soda, were installed and steam- and air-reticulation
utilities were provided. Major mechanical items supplied to the plant
were a 65m² belt filter, tanks and vessels
made from stainless and mild steel, rubber-lined mild steel and glass-reinforced
plastic (GRP). Pumps, of both the horizontal and vertical- spindle types,
made from stainless steel and plastics, filter presses, agitators and
electrode boilers were also supplied.
The cobalt-purification plant was commissioned without any major problems,
but the zinc-SX plant started six weeks later than envisaged due to
the unseasonably high rainfall in the period December to March, which
measured 1528 mm at the site office. Only minor rectifications were
required during commissioning of the SX plant.
The project was completed with no labour unrest and no lost time injuries
during the more than 585 000 man-hours worked on site. On site, the
labour force peaked at 420 persons in March 2001. A good working relationship
was established between the project team and the senior management of
both Avmin and Chambishi Metals during the execution of the project
and this relationship has been maintained. The man-hour cost for the
project was less than 10% of the total cost of the project. This remarkably
low proportion was achieved by the multi-skilling abilities of the project
personnel. On average the site management team totalled only three members
for the duration of the project.
The plants have been designed for a 20-year life span. The project
was conducted on a fast-track basis with very tight time and capital
constraints. This reimbursable contract for engineering services, for
a plant with a value of nearly US$20M was completed in July 2001.
More information may be obtained from:
Steve Burks, Managing Director, Bateman Metals,
on +27-11-899-2756 or email base@batemanengineering.com
or
Gordon Sneddon, Leading Mechanical Engineer,
on +27-11-899-2217 or email base@batemanengineering.com
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