In May this year Dowding, Reynard & Associates (DRA) undertook
a R40-million contract for Durban Deep’s Blyvooruitzicht
gold-mine, located 5 km south of Carletonville, and 75 km
south-west of Johannesburg, as part of a project to reclaim the
mine’s number four and five tailings dams. DRA process
consultant Bruce Ebell says the tailings deposits, which date back
to the 1940s, consist of around 25-million tons of ore, at a grade
of 0,587 g/t gold. “The plant to process these will be on
stream in October, with full operational capacity to be achieved by
the end of the year, after a build-up period of about two
months,” notes Ebell.
Feasibility work on this fast-track project began in April, and the
decision to begin implementation was taken in May, which will see
the removal of the mine dump closest to Carletonville. The tailings
will be transported using a pipeline of about 5 km to the plant
and, after processing, another 7,5 km to the current tailings dam.
“The project has been fast-tracked, as rock dumps at the mine
are being depleted at a rate faster than initially planned.
“The ore from these tailings will provide a new source of
feed for the mine’s plant to compensate for this.
“Fraser Alexander, which acquired the build, own and operate
contract for the mining of the tailings, will supply the
high-pressure water for the required monitoring equipment, as well
as screens and pumps to enable the transfer of the tailings to the
processing plant,” adds Ebell.
He says that the project will use existing equipment at
Blyvooruitzicht, including the old transfer pumpstation. New
transfer pumps will be installed at the reclamation site, which
will be upgraded to handle a higher tonnage. The existing residue
pumps will be released for deployment at the reclamation site and
DRA will install a new pipeline. When the project is complete, the
reclamation of the tailings will take place at a rate of 240 000
t/m.
“Eight tanks in a hybrid two-stage carousel or
carbon-in-leach (CIL) plant will process the re- cycled tailings
material.
“One of the eight tanks will be converted into a
preconditioning tank, where lime and oxygen will be added, and the
other seven will be converted to CIL tanks through the installation
of interstage screens and agitators,” states Ebell.
He notes that high-shear reactors are being used for the addition
of lime, oxygen and cyanide, to improve the kinetics of the
dissolution of the gold, and reduce the consumption of reagents.
Loaded carbon will be sent to the existing elution plant for gold
recovery.
The residue from these tanks will be pumped to the existing gold
plant, and will be joined by the run-of-mine material of 120 000
t/m, to take the total material processed to 360 000 t/m, compared
with the current 210 000 t/m, reports Ebell.
The reagents will use the existing cyanide storage and dosing
facility.
“The project will also see modifications made to the tailings
dam, and the dam wall will be changed from a clay wall to a cyclone
system. “Return water from the tailings dam will be pumped
back to the reclamation site over a distance of 6 km for reuse as
high-pressure water,” notes Ebell.