Margin-enhancing UHDMS tech advances positively at Kumba
In 2024, Kumba Iron Ore announced the implementation of ultra-high-dense-media-separation (UHDMS) technology at its Sishen iron ore mine in South Africa’s Northern Cape. The ZAR11.2 billion (about US$600 million) investment upgrades the existing dense-media-separation (DMS) plant and is expected to extend Sishen’s life of mine while materially improving product quality and yield.
Ultra-High-Dense-Media-Separation (UHDMS) is an evolution of conventional Dense-Media Separation (DMS), designed to significantly extend the density range at which separation can occur. In a standard DMS plant, separation typically takes place at media densities of up to around 3.6 g/cm³. UHDMS increases that operating density to above 4.0 g/cm³. That higher density window allows for much sharper separation between iron ore and gangue, particularly where the specific gravity differences are narrower at higher iron grades.
Like conventional DMS, UHDMS uses a ferrosilicon (FeSi) suspension as the separating medium. However, a key technical enabler is the use of nitrogen gas-atomised FeSi. The spherical nature of these particles helps maintain manageable viscosity even at elevated densities, which is critical for cyclone stability and efficient separation at UHDMS operating conditions.
Each UHDMS module consists of multiple high-capacity dense media cyclones – in the current configuration, there are six units rated at approximately 650 t/h each. These cyclones create a centrifugal field that separates material based on specific gravity – higher density iron ore particles report to the underflow, while lower-density waste exits via the overflow.
Beyond the separation circuit itself, implementation required modifications to upstream and downstream infrastructure, including upgraded washing and screening circuits, quaternary screens and additional conveyor capacity to integrate UHDMS modules into the existing plant and jig circuits.
Kumba told IM that the extended density range is not incremental; it is transformational for the Sishen orebody. Firstly, it allows the miner to process lower-grade feed that would previously have been uneconomic. By lowering the mining cut-off grade from approximately 48% Fe to around 40% Fe, it can recover additional value from material that historically would have been classified as waste.
Secondly, the sharper cut-point improves separation precision, which directly enhances product quality and yield. Once fully implemented, the proportion of premium product at Sishen is expected to increase from roughly 18% of production to approximately 55%.
Thirdly, the improved processing efficiency translates into lower overall mining intensity. The strip ratio improves from approximately 3.9 to around 3.3, equating to roughly 15 Mt/y less waste mining. This reduces operating costs and improves margin resilience. The modular cyclone-based design also allows phased implementation, reducing operational risk during conversion.
There are also broader operational and market benefits. At its core, UHDMS provides greater flexibility across a wider range of ore grades and densities. It effectively converts previously marginal material into economic feed, extends Sishen’s life of mine (currently projected to 2044) and structurally improves the mine’s cost position.
Importantly, the uplift in premium iron ore production also aligns with structural changes in the steel industry. Higher Fe content products support improved blast furnace efficiency and are increasingly attractive to steelmakers seeking to lower emissions intensity.
In short, Kumba told IM that UHDMS is not simply a plant upgrade. It is a step-change in separation capability that strengthens recovery, improves product quality, lowers mining intensity and enhances the long-term competitiveness of the asset.
The UHDMS project at Sishen is being implemented through a phased, modular conversion of the existing dense media separation plant. Over a multi-year period, six of the eight coarse modules and five of the seven fines modules will be converted to UHDMS configuration. This modular approach is designed to minimise operational disruption and manage risk. At any given time, modules not under construction remain in operation, alongside the existing jig circuits, allowing Sishen to maintain production continuity during the transition.
Following approval of the full capital investment package, construction commenced in the second half of 2024. Engineering and procurement activities have progressed in line with schedule, and site works have been sequenced to support the staged conversion plan.
The first UHDMS module is targeted for production in 2026, with the main plant tie-in scheduled for this year as well. Full conversion and ramp-up to steady-state operation are expected by the end of 2028. During the implementation phase, production will continue to be supported by operational modules as well as strategic use of finished product stock to smooth supply where required. Overall, the project remains aligned to its planned timeline and is structured to balance capital execution with operational stability.
With regard to the development and commercialisation of the UHDMS technology, in 2010 Kumba worked with a technology partner for specific UHDMS knowledge and high density characterisation technique that would assist Kumba with the technical development of a UHDMS pilot plant to demonstration and commercialise the technology. This was done successfully and concluded in 2013.
Kumba then built the first UHDMS modules for jig discard beneficiation followed by the study development and implementation, all of which was done inhouse as the technology was embedded in Kumba operations.
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