Kumba Iron Ore is looking to grow its
production from the current 44 M/ta to
70 M/ta by 2019. Of this planned growth,
approximately 6 Mt/a is scheduled to come
from projects in South Africa’s Limpopo
Province. The Zandrivierspoort (ZRP) project
aims to mine and beneficiate a magnetite
resource with low contaminant levels to
produce from 1 Mt/a up to 2.5 Mt/a product in
the form of either a concentrate, micro-pellets
for direct reduction, or blast furnace pellets.
Anglo American Technical Solutions Research
conducted piloting campaigns with a bulk
sample obtained from the ZRP site. Kumba
Iron Ore is currently designing a plant that will
process the ZRP magnetite-haematite ore-
body. Anglo American Technical Solutions
Research conducted these piloting campaigns
to validate the process design flow sheet,
demonstrate process performance, and to
generate data for use as design basis.
Secondary to this, the pilot plant was to
produce approximately 7 t of magnetite-
haematite concentrate with low enough SiO2 to
be used as feedstock for pelletizing studies at
Kumba’s Value in Use Laboratory and
elsewhere. The piloting campaign entailed
crushing the run-of-mine to -1 mm prior to
low-intensity magnetic separation (LIMS) and
rare earth drum separation (REDS) for
haematite scavenging, ball milling in closed
circuit with a vibrating screen, cleaning of the
ball mill circuit product through three stages of
LIMS, IsaMilling the ball mill LIMS
concentrate, and further re-cleaning of the
IsaMill product through three LIMS stages. A
combination of LIMS and REDS in different
parts of the circuit was chosen to recover
magnetite and liberated haematite respectively.
Magnetite is ferromagnetic, thus it can be
effectively recovered using LIMS (800–2000 G)
while haematite is paramagnetic, thus requires
high magnetic field intensities (>6000 G)
(Wills and Napier Munn, 2006). This paper
presents interpretations of the feed sample
characterization, pilot plant mass balance
results, and the implications for the proposed
ZRP plant flow sheet.
ZRP geological outline
The Zandrivierspoort prospecting right is
located approximately 25 km northeast of
Polokwane on the farm Zandrivierspoort 851
LS, in South Africa’s Limpopo Province, as
shown in Figure 1 (Kumba Iron Ore, 2013).
The low-grade magnetite project mineral
resource base is estimated at 476.1 Mt with
34.5% Fe (Kumba Iron Ore, 2013).
Zandrivierspoort is a banded iron formation
Production of pelletizing concentrates from
Zandrivierspoort magnetite/haematite ore by
by P. Muthaphuli*
Kumba Iron Ore’s Zandrivierspoort (ZRP) magnetite-haematite project aims
to mine and beneficiate a magnetite resource with low contaminant levels
to produce from 1 Mt/a to 2.5 Mt/a product, which will be either a
concentrate, micro-pellets for direct reduction, or blast furnace pellets.
Anglo American Technical Solutions Research conducted a number of
piloting campaigns to validate the process design flow sheet, demonstrate
process performance, and to generate data for use as a design basis.
Secondary to this, the pilot plant was to produce approximately 7 t of
magnetite-haematite concentrate with low enough SiO2 to be used as
feedstock for pelletizing studies.
The pilot plant achieved 34.2% mass yield, at 69.0% Fe, 2.2% SiO2,
from an IsaMill grind of 80% -45 µm. This product quality will compare
favourably to other leading direct reduction (DR) pelletizing concentrates.
However, two-stage comminution to 80% -75 µm and beneficiation of ZRP
ore will produce a blast furnace (BF) quality pelletizing concentrate,
indicative quality being 67.6% Fe and 4% SiO2, at higher mass yields. An
economic evaluation between producing a DR and a BF pelletizing
concentrate will have to be conducted prior to finalizing the concentrate
production flow sheet..
Magnetic separation, iron ore, magnetite, haematite.
* Anglo American Mining and Technology,
Technical Solutions Research.
© The Southern African Institute of Mining and
Metallurgy, 2014. ISSN 2225-6253. This paper
was first presented at the, Physical Beneficiation
2013 Conference, 19–21 November 2013, Misty
Hills Country Hotel and Conference Centre
Cradle of Humankind, Muldersdrift.
505The Journal of The Southern African Institute of Mining and Metallurgy VOLUME 114 JULY 2014 ▲
Production of pelletizing concentrates from Zandrivierspoort magnetite/haematite ore
(BIF) magnetite deposit in the palaeoproterozoic
Rhenosterkoppies greenstone belt or Rhenosterkoppies
fragment, which occurs to the northwest of the main,
northeast-trending Pietersburg greenstone belt. Figure 2
represents a vertical profile (slice) intersecting the three-
dimensional model of the Zandrivierspoort deposit (A-A1 red
line in Figure 1), demonstrating the company’s interpretation
of the relationship between the orebodies, waste material,
and local geology (Kumba Iron Ore, 2013).
BBulk sample preparation and characteristics
Kumba Iron Ore delivered approximately 38 t of run-of-mine
(ROM) bulk sample at a 150 mm top size. This was reduced
using a jaw crusher to 100% passing 70 mm. The jaw crusher
product was further crushed to 100% passing 40 mm prior to
comminution by high-pressure grinding roll (HPGR). The
HPGR crushing was conducted at Mintek using a Koppern
HPGR unit to produce 100% passing 1 mm product, which
yyields more than 60% liberation of the magnetite and
haematite combined. On average, the bulk sample received
contained 35.7% Fe with a 40:60 magnetite to haematite
ratio. Figure 3 shows the bulk mineralogical composition of
the bulk sample processed through the pilot plant.
Previous company internal data indicated that the average
ZRP orebody contains approximately 40.8% magnetite with a
70:30 magnetite to haematite ratio (Kumba Iron Ore, 2013).
The implications of the lower magnetite to haematite ratio of
this bulk sample on the pilot plant mass yield will be
highlighted and discussed under the mass balance results.
The Bond Ball Mill Work Index (BWI) was determined
at a limiting screen of 75 µm. The BWI test was carried out
in accordance with the modified Warren Spring Laboratory
method. The BWI of this ZRP ore was measured at
17.6 kWh/t, which is in line with previous values obtained
from other hardness testing carried out on ZRP drill cores at
Anglo Research (van Drunick, 2007). A grind of 80% passing
(P80PP ) 75 µm was chosen targeting a blast furnace pelletizing
concentrate with 67% Fe and less than 5% SiO2, while a
45 µm grind was targeting a direct reduction pelletizing
concentrate with a much cleaner product containing 69% Fe
and less than 2% SiO2. Batch grinding and Davis tube tests at
1000 G (Murariu and Svoboda, 2003) had shown that these
qualities were achievable at P80PP of 75 µm and 45 µm.
Piloted flow sheets
High-SiO2 concentrate production (blast furnace
Figure 4 illustrates the first phase of the piloting campaign, in
which the circuit was operated with a cobbing and a REDS
scavenger magnetic separator, the ball mill in closed circuit
with a 75 µm screen, and the product of the ball mill circuit
reporting to three stages of LIMS cleaning. The ZRP ore
consists of magnetite and haematite, a significant amount of
506 JULY 2014 VOLUME 114 The Journal of The Southern African Institute of Mining and Metallurgy
in Limpopo Province (Kumba Iron Ore, 2013)
Figure 2—Southeast-northwest profile depicting the local geology
through the Zandrivierspoort magnetite deposit (Kumba Iron Ore, 2013)
Figure 3—Bulk mineral composition of the ZRP bulk sample used for
Figure 4—Flow sheet for production of a BF pelletizing concentrate
wwhich has been shown to be intimately associated with the
magnetite. The product of the REDS scavenger was combined
wwith the cobbing product to feed the ball mill circuit.
The addition of a REDS scavenger improves yield due to
the recovery of additional mass of fully liberated haematite
wwhich is not recovered across the cobbing LIMS because of its
lower magnetic susceptibility.
Low-SiO2 concentrate production (direct reduction
The blast furnace pelletizing concentrate was sent to the
AAnglo American Platinum Division Metallurgical Laboratory
(DML) for IsaMilling using a 100 litre (M100 IsaMill) pilot
plant unit with 75 kW installed power. Davis tube test work
data showed that it was possible to reduce the SiO2 content in
the concentrate to around 2% from a grind of 80% -45 µm.
The IsaMill product was re-pulped using a ball mill to
break lumps and allow for dilution prior to the three LIMS
cleaning stages as illustrated in Figure 5. This circuit was run
at very low feed densities as its primary objective was to
produce a high-quality concentrate that is low in SiO2. Thus
it was critical to avoid SiO2 entrainment, which would have
been worsened by high feed densities.
Ball mill and screen
Table I and Table II summarize the ball mill and screen
specifications respectively. The ball mill had rubber liners.
The screen was a retro-fit of a linear screen that was
modified and fitted with a 75 µm woven wire cloth due to the
lack of pilot Derrick screens in the country at the time of the
test work. The screen deck was re-designed and fitted in-
Magnetic separator specifications
The four LIMS units were salvaged from an old magnetic
separation plant and refurbished in-house with assistance
from Eriez Magnetics. The REDS was hired from Multotec.
Table III summarizes the magnetic separator specifications
and operational settings empl