The Bushveld Igneous Complex (BIC) in South Africa holds approximately three
quarters of the world’s viable chromite ore deposits. Most chromite is used for the
production of ferrochromium (FeCr), which is a relatively crude alloy. Several chromite
seams exist in the BIC. The most economically viable seams are the lower group 6 (LG6),
the middle group 1 and 2 (MG1 and 2) and the upper group 2 (UG2) seams. The LG and MG
seams are exploited specifically for their chromium content, whereas the UG2 seam is mainly
exploited for platinum group minerals (PGM). However, the upgraded UG2 chromite in the
PGM tailing is increasingly being used as a feedstock for FeCr production. Many different
process variations exist for FeCr production. However, the process option applied in most
green and brown field FeCr expansion projects during the last two decades in South Africa
has been the oxidative sintered process (also referred to as the Outotec or Outokumpu
process). Notwithstanding the common application of the oxidative sintered pelletised feed
technology in the South African FeCr industry, and the increased utilisation of beneficiated
UG2 ore, a direct comparison of the physical properties of oxidative sintered pellets produced
from UG2 with the physical properties of that produced with conventional metallurgical
grade chromite ore is currently lacking in the peer-reviewed scientific literature. Therefore,
the physical properties of oxidative sintered pellets produced from a typical beneficiated
South African UG2 ore were compared with the physical properties of that produced with
conventional South African metallurgical grade chromite ore in this study.
The results indicated that the case study metallurgical grade chromite ore required
13 kWh/t more energy to mill than the case study UG2 ore prior to pelletisation, which can
lead to substantial cost savings. The compressive strength of the oxidative sintered pellets of
both case study ores statistically showed that oxidative sintered pellets made from UG2 ore
Abstract
were the same or better than those prepared from metallurgical grade chromite ore. A
comparison of the abrasion strengths of the oxidative sintered pellets of both case study ores
indicated that the pellets prepared from UG2 ore were superior compared to the metallurgical
grade pellets. The reasons for the superior UG2 pellet strength were investigated with
backscatter-, secondary electron- and elemental X-ray mapping scanning electron microscopy
(SEM), which indicated that differences in crystalline structures at least partially contributed
to the differences observed. Results presented here can be utilised by FeCr producers to
better quantify the advantages and disadvantages associated with the use of UG2 ore for FeCr
production. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2014
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/15245 |
| Date | January 2014 |
| Creators | Glastonbury, Ralph Ivor |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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