November 21, 2017

Kumba Sishen Mine

Proactive Upgrade Saves Costs at Kumba Iron Ore Mine – Sishen

Sishen mine, Kumba’s flagship operation and one of the largest open-pit mines opened in 1947, and is located in South Africa’ s Northern Cape Province near the mining town of Kathu.

Geology
High grade haematite iron ore (laminated, massive, conglomeratic and breccia types) is found in the upper parts of a Lake Superior-type, BIF succession of the Griqualand West Supergroup as the Transvaal Supergroup is known where it occurs in the Northern Cape.

Due to the long geological time interval between the deposition of the oldest rocks of the Griqualand West Supergroup, the Campbellrand Group dolomites, and the youngest deposits in the area, the Kalahari Group sands, a number of uplift and erosion cycles and deformational events are recorded in the rock record.

The deposits are located on the western flank of the Maremane Anticline, which strikes north-south and dips about 11o west. Local structures in the mine area are, however, very complicated and the interplay between the various tectonic events and associated geological structures was critical to the formation and preservation of ore in the region.

In general, the high-grade laminated and massive ore is preserved in synclinal and pseudo-graben structures, which are the result of multiple deformation events. Medium and lower grade conglomeratic and brecciated ores are preserved with deep palaeo-sinkhole structures in the southern portions of the deposit, where these structures are the result of karsificatiopn of the underlying dolomites during the periods of uplift and erosion.

Mining method and processing
Ore is extracted through open-cast mining methods and the current mining process entails the topsoil removal and stockpiling, followed by drilling and then blasting of waste lithologies and ore. Overburden is backfilled in or hauled to waste rock dumps on the edge of the pit. The iron ore is loaded according to blend requirements and transported to the beneficiation plants where it is crushed, washed and screened.

Each size fraction is separated and beneficiated using a ferrosilicon medium or jigging process before being stockpiled on the product beds. Plant slimes are pumped to evaporation dams and the plant discard material is stacked on a separate waste dump. Seven iron ore products are produced and they are reclaimed from the product beds and loaded into trains to be transported to local steel mills and Saldanha Bay for export to international markets.

Proactive Upgrade Saves Costs at Kumba Iron Ore Mine – Sishen
A change in its market for its Coarse Sinter Product (CSP) produced at its open cast Sishen mine led to an innovative upgrade to Kumba Iron Ore’s processing plant.
Says Ric Fry, Project Manager at DRA-MP, a local process engineering, construction and project management group, “Previously the client marketed its Coarse Sinter (CS) product as a premium fine ore. However, demand for the product disappeared when the client’s main customer changed its requirements. As a result, the CS required crushing to fines which added considerable additional operating costs for the fine ore crushers as well as a loss of revenue due to the lower price of the fines product.”

“A decision was then taken to upgrade its processing plant to produce a saleable product using the existing infrastructure. The 10mm Lump Project, as the upgrade became known as, would see the CS separated into a coarse and fine fraction. The coarse fraction would then be blended into the existing DMS and Jig lump product in order to change the lump undersize from 8mm to 6,3mm. At the same time the fines fraction would feed into the DMS fine product beds, changing the DMS fines product top size to 6,3mm. Sishen’s lump product is highly valued by the steel industry as it can be fed directly into a blast furnace without the need for pelletising.”

DRA undertook the design and engineering of the R159 million brownfields project on an EPCM basis which would include a conveying system comprising four units with a combined length of 680m together with transfer towers, chutes, take-up structures, Geoscan support structures, electrical, control and instrumentation systems for co-stacking and distributing the Modified Coarse Sinter (MCS) product to both Jig and DMS lump product beds.

“Cognisance was taken of the fact that the plant operates on a 24/7 basis so design, construction and commissioning were planned so as to avoid impacting negatively on the client’s other product streams. The upgrade came online on 24 December 2012, 15 months after commencement. One of the important factors that led to the success of this project was the synergy among all of the teams involved from DRA, the contractors and the client, ensuring a smooth operation from start to finish.”

“By taking a proactive approach to an unforeseen event, Kumba, with the help of DRA, was able to ensure the profitability of its product by simply modifying its processes, maintaining its reputation as a low cost producer. This is of particular importance at a time when budgets are tight and commodity markets are volatile.”

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