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The expansion of Assmang’s Khumani iron ore mine in the Northern Cape adds another chapter to DRA Mineral Projects’ association with the mine.

This relationship goes back to the project’s first phase in 2005. An Inside Mining exclusive.

A long time player in such areas as coal, gold, platinum and diamonds, the project presented DRA with its first major iron ore execution project.

A brief history of Khumani and Phase 1

The opencast Khumani iron ore mine was formerly known as the Bruce, King and Mokaning (BKM) project, referring to the farms on which the iron ore resources are located. It is located near Kathu in the Kalahari Desert and was established to expand Assmang‘s existing iron ore business from its single operating Beeshoek iron ore mine.

Iron ore is transported for export via Transnet’s iron ore rail channel to Saldanha Bay, 860 km away.

Phase 1 of the Khumani mine project pipeline saw the construction of a new opencast iron ore mine on the Bruce farm (adjacent to Kumba Iron Ore’s Sishen mine) and a 10 Mtpa greenfield beneficiation plant on the Parson farm.

The Phase 1 detailed design and engineering of the processing plant began in September 2006 and was completed successfully by the end of 2008. Even though the project was DRA’s first iron-ore venture, it was delivered on time and within budget – notwithstanding the tight deadlines with tough and competitive market conditions in the construction industry at the time.

The original design of Phase 1 included scope for expansion to 16 Mtpa and, after the results of the Phase 2 feasibility studies proved positive, the green light was given for the Khumani Expansion Project (KEP) to go ahead.

KEP kicks off

A large project with a value of R6 billion, KEP involved a number of components:

  • run-of-mine (ROM) crushing and processing facilities for the new King opencast mine, including workshops and associated mine infrastructure
  • material handling, including an overland conveyor belt
  • additional ROM stockpiles, stacker and reclaimer machines
  • additional washing, screening and jigging capacity
  • new primary and secondary thickeners and extension to the dewatering circuit
  • extensions to the existing paste deposition facility
  • extensions to the product yard, including new stockpiles, stackers and reclaimer
  • a second railway balloon and a second rapid load out station
  • a new railway siding to access the local rail line and doubling of the export arrivals and departure rail line
  • a new robotics laboratory.
Early works on KEP commenced in October 2008 with full-scale construction of the King mine, ROM processing and infrastructure starting in January of 2009. This portion of the project was handed over four months ahead of schedule in November 2010.

Construction of the additional rail infrastructure and load-out station were completed by August 2011, followed by the brownfield Parson plant expansion commissioning in October of the same year, then the extension to the product yard in June 2012.

From mine to rail

Crushing

Khumani’s ore is transported from the open pits by truck to the mine’s crusher plant, consisting of a gyratory primary crushing unit, scalping station and a cone crushing unit for secondary crushing. The ROM plant also includes an 18 000 t buffer stockpile prior to the 3-km long, 3 500 tph overland conveyor feeding the ROM stockpiles at the Parson process plant.

Processing

The ore is stacked onto and reclaimed from the ROM stockpiles to feed the now 16 Mtpa Parson processing plant’s on and off grade streams. The KEP project scope for the off grade circuit consists of:

  • an on/off grade ROM stockpile
  • tertiary crusher
  • three washing and screening systems
  • two lumpy jigs and screening system
  • one additional fines jig
  • an additional HPGR screening system
The scope of the on grade product circuit consists of a number of conveyor upgrades so that the increased throughput of material is screened, washed and re-crushed in the tertiary crusher.

The processing plant’s water circuit required the construction of an extension to the existing dewatering plant and the addition of a 90 m primary thickener, an 18 m secondary thickener, 4 km of overland tailings pipe and a 5 m lift to the existing paste disposal dam wall. In addition, two 20 Mℓ potable water tanks were built.

Once contaminants are removed via the jigs and the product processed, it is transferred to the product stockyard. Separate stockpiles for lumpy, direct reduced iron and fines product were built to store and handle the product, ready to be loaded and railed.

Commissioning of the processing plant was undertaken by DRA with the assistance of Minopex, the group’s mineral plant contract operations and maintenance division.

Rail infrastructure

Khumani’s expansion required a second rail load-out station and the doubling of the existing rail balloon in order to accommodate the additional throughput. The rail infrastructure for the export product required a doubling of the arrivals line while the local product necessitated the construction of a local siding. Each of the two rail load-out stations is capable of loading up to 100 t of material per minute.

Beating schedules & safety records

Two particular milestones stand out on the KEP project for DRA – the fact that the project was completed ahead of schedule and, more importantly, an impeccable safety record during the entire construction process.

Safety has always played a critical role in DRA’s corporate culture both on and off site. By September 2012, when the last section of the project was completed, the project achieved a fatality-free record of more than 12 million man hours worked. The labour on-site peaked at 2 700 during the middle of 2011.

Contributing to the project coming in ahead of schedule was the fact that only three 14-day shutdowns were required with most of the pre-shutdown work taking place on scheduled maintenance days.

As a brownfield project, construction had to accommodate the mine’s existing operations. An excellent communications channel between the project team and mine operations ensured that the process remained smooth and trouble free. In addition, the project team maintained close supervision of site contractors to ensure quality of construction work, as well as ensuring that suppliers and contractors were kept on track with the programme milestones.

A few of the project’s milestones include the handing over of both the King mine and Parson plant four months ahead of schedule, while the ROM stockpile was handed over six months ahead of schedule. In addition, the product yard extension and second rail load-out station was on time as per the baseline programme.

Sidebar: KEP vital statistics

Key statistics for KEP include:

 

  • 7.5 million cubic metres of earthworks moved
  • 78 000 m3 of concrete cast
  • 7 500 t of steelwork erected
  • 39 conveyors installed and an additional 38 modified
  • 28 km of conveyor belting installed
  • 31 km of rail tracks installed
  • 52 km of piping installed
  • 430 km of electrical and 150 km of instrumentation cabling installed
As a result of the success that DRA has achieved with the KEP project, the company was awarded a further EPCM contract for a super fines recovery plant at Khumani. This plant makes use of wet, high intensity magnetic separation to process tailings for the extraction of saleable product.

Construction on the plant commenced in September 2011 and the engineering and procurement phases of the project are already complete. By the end of the first quarter this year material had been introduced to the plant and the first product produced. When going to print, it was expected that the plant would be handed over to the Khumani mine by the end of May 2013, two months ahead of schedule and under budget.

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