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Kumba to relocate VIU facility to Joburg

24th July 2015

By: Dylan Stewart

Creamer Media Reporter

  

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Iron-ore major Kumba Iron Ore, a business unit of Anglo American, will start moving its value-in-use (VIU) facility, in the west of Pretoria, to the Anglo American technical solutions facility, near Crown Mines, in the south of Johannesburg, by the end of the year, with commissioning at the new location scheduled to begin in the first quarter of next year.

The relocation is intended to group all Anglo’s technical services together, and is part of Kumba’s streamlining of its operations, which began in December last year in response to the depressed iron-ore market, explains VIU manager Kobus Vreugdenburg.

The VIU facility is a test facility that is geared to give Kumba a better understanding of its ore and its value, he states. This information is used during price negotiations and project planning.

The facility typically receives samples from Kumba’s mines and sometimes from Kumba clients, Vreugdenburg says. The ore is tested for qualities such as hardness, lump size, reduction disintegration and reducibility, and the data is logged, with a specialist interpreting the data to give it value.

To test the hardness of the ore, samples are placed in a rotating drum, called a tumbler, in which the ore sample is dropped 200 times from a height of about 100 cm, with the reduction in size subsequently measured. Vreugdenburg explains that Kumba’s ore is typically very strong and, therefore, does not break down during transportation.

Lump size distribution is determined by passing the ore through sieves of particular sizes and, to establish the reducibility index, ore is exposed to reducing gasses, for example carbon monoxide, at 950 °C . During this process, the rate at which the ore releases oxygen is measured through the rate at which the mass of the ore decreases.

The test results are incorporated into models, whereby a specialist who understands the iron-making process assigns a final value to the product, says Vreugdenburg.

“The product has to be understood in terms of the customer’s process,” he explains.

Sintering
Vreugdenburg notes that a customer will have to process fine ore before feeding it into a blast furnace. One of the processes to treat fine ore – typically below 5 mm in size – to make it suitable for feeding into blast furnaces is called sintering.

It entails exposing the fine ore to a high temperature to agglomerate it into bigger lumps. Typically, this process will take place along a continuous industrial sintering belt. The sinter pot test at VIU simulates the sinter process using a stationary sinter pot filled with a granulated mixture of fine ore, lime and coke, and ignited at 1 050 °C using an ignition burner from above. The ore concentrate is initially granulated into small balls in a rotating drum to create permeability in the sinter pot.

Permeability is important because this enables a fan to drag air in the pot so that the material below the heated surface is also sintered, “like a tobacco pipe”, states Vreugdenburg.

At the VIU facility, the sinter process is closely controlled using a programmable logic controller; the fuel rate, production rate and metallurgical property data are also generated during this process.

The normal sinter process has a limit of between 5% and 15% in terms of the amount of concentrate or pellet feed that it can absorb, he adds. Concentrate and pellet feed are very fine; typically 80% of pellet feed is smaller than 75 µm.

“Owing to a surplus of fine ore in the world, we are trying to increase the amount of fines that can be used in the sinter pot during the sinter process,” states Vreugdenburg.

Kumba is doing this through two methods – adding burnt lime, or calcined limestone, which acts as a binder to improve the granules during the agglomeration process; and using a pelletising disk to make micropellets of between 2 mm and 5 mm out of the fines to perform preagglomeration.

Edited by Leandi Kolver
Creamer Media Deputy Editor

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