Materials
handling at Zisco
The materials
handling facilities designed and supplied by BATEMAN at the restructured
complex of Zimbabwe Iron and Steel Company (Zisco)near KweKwe, Zimbabwe,
have been working as per specification since commissioning at the
start of 1997. They include stackers, reclaimers, conveyors, and
dust control systems.
Restructuring
of the complex was necessitated by the depletion of iron ore supplies
from Buchwa Mine and the need to augment supplies from the mine
at Ripple Creek. BATEMAN handled the project management and overall
design and also sourced the required funding from South Africa,
he United Kingdom and Zimbabwe.
The Zisco complex
comprises the blast furnaces, coke ovens, steel mills ands inter
and limestone plants near the town of Redcliff. The iron ore from
the new Ripple Creek Mine, about 20 km south of the main plant at
Redcliff, is transported to the steel complex by overland conveyor
and, while the iron ore supplies at Buchwa last, these will continue
to be brought in by rail. Coal is supplied by train to the site,
stockpiled at the complex and converted in coking ovens to coke
as required . Electrical power is obtained from the national grid.
The limestone is obtained from a quarry adjacent to the main plant
at Redcliff.
THE RIPPLE
CREEK PLANT
The Ripple Creek plant processes material from Zisco’s new
open castmine. It has facilities for rushing, screening, sampling
and blending. The run-of-mine ore consists of material up to 900
mm in size. Primary crushing and screening at a rate of 1 000 t/hr
reduces this to minus 150 mm. Secondary crushing, screening and
sampling follow to produce a minus 31,5 mm product.
Blending to
a constant grade is achieved n a stockyard with two 60 000 tonne
blending stockpiles in tandem. A 1 000 t/hr BATEMAN/SCHADE slewing
luffing stacker layers the ore onto the stockpiles in a form suitable
for lending and this is recovered using a500 t/hr BATEMAN/SCHADE
double harrow bridge reclaimer.
The blended
ore is then conveyed at a rate of 500 t/hr on a 15,6 km, single
flight curved overland conveyor to the plant at Redcliff. This conveyor,
which will be discussed in more detail in the next issue of BATEMAN
lobe, is the longest of its kind in the world.
THE REDCLIFF FACILITIES
At Redcliff the minus 31,5 mm ore from Ripple Creek is transferred
to a conveyor taking it to the top of covered conical stockpiles.
Here it is discharged and stored for the time being, together with
ore from Buchwa. The stockpiled ore is reclaimed by variable speed
BATEMAN belt feeders and fed to a tertiary crushing, screening and
sampling facility to produce minus 8 mm material. This is fed to
two parallel 60 000 tonne blending stockpiles.
Limestone is
extracted from an existing stockpile and crushed and screened. The
limestone is sized to minus 3 mm, conveyed ver he KweKwe River and
stored in a concrete silo before being conveyed to the blending
stockpiles. Batches of limestone, coke and reverts (the undersized
fraction from previous processing) are transported from the irrespective
storage areas by means of the same conveyor to the sinter plant.
The iron ore
and limestone are blended to a consistency of grade required for
the sinter plant using 700 t/hr BATEMAN/SCHADE luffing stacker and
a 500 t/hr BATEMAN/SCHADE single arrow bridge reclaimer. A transfer
car is used to transfer the reclaimer to an adjacent stockpile.
He blended material is then transported to the sinter plant. The
sintered product is conveyed to a final screening facility from
where only the oversized fraction is fed to the blast furnaces.
The reverts are stockpiled and fed back to the sinter plant for
reprocessing via feed arrangement comprising a feed bin and vibrating
feeder. The feed bin is fed using a front-end loader.
CONVEYOR
NETWORK
Besides the 15,6 km overland conveyor, 46 conveyors with a total
length of 6 km have been provided to convey the limonite, coarse
and crushed iron ore, dolomitic limestone, sinter and coke. heir
lengths range from 11 m to525 m with belt widths from 750 mm to
1 800 mm. The maximum capacities are between 128 t/hr and 1 760
t/hr.
ENVIRONMENTAL CONTROL
A BATEMAN-Brandt reverse pulse bag filter controls emissions from
the limestone impactors. This filter system is particularly cost
effective for this type of application. It handles gas flow rates
up to 11,8 m3/sec and controls emissions at less than 50 mg/m3.
The filters require little maintenance and are simple and reliable
to operate.
