Mining and minerals project house TWP, a subsidiary of the Basil Read group, reports that the erection of the Sishen expansion project (SEP) 1B beneficiation pilot plant at iron-ore producer Kumba Iron Ore’s Sishen mine, in the Northern Cape, is progressing well.

Civil, mechanical and piping work are near completion and electrical and instrumentation installation is in progress.

The pilot plant was scheduled to be commissioned in mid-January this year.

TWP was appointed to undertake the engineering procurement and construction management of the plant in October 2010.

The beneficiation plant will make use of jig technology, comprising eight jig modules operating in parallel to produce three separate product sizes, namely coarse, medium and fine products between 1 mm and 25 mm.

Laboratory-scale testing established the possibility of two upgrading technologies, the Allflux up-current classifier (UCC) and the SLon vertical pulsed high-gradient magnetic separator.

The Allflux UCC is a fluidised-bed separator, which employs autogenous heavy-media technology classification. Unlike conventional fluidised-bed separators, classifying with the Afflux does not require large-scale dense- medium preparation through a cyclone.

The less-than-800-μ material is fed through a single feed into the fine products section through a distributing cone.

Upstream water is added and an autogenous heavy media originating from the fine ore is produced. The less-than-45-μ fine particles are then discharged into the overflow section.

This is achieved by adjusting the upstream water.

The unit is fully automatic with dis- charges from the fine-products section supervised and controlled by continuously measuring the level in the fluidised bed and the slurry’s density. This is achieved by using an electro-hydraulic control unit.

The homogenous constitution of the auto- genous heavy media is guaranteed, owing to the coarse particles being separated from the fines section and because of the extremely small perforation of the Conidur pierced screen, which is a fine whole screen.

The SEP 1B was conceived to investigate the benefication of fine material of less than 1 mm, which could potentially increase Kumba’s product portfolio by about 0.75-million tons a year. Currently, the Sishen plant discards fine material of less than 1 mm at a plant waste dump.

The SLon uses an electromagnetic field, which is generated within the separating zone. A carousel, rotating on its horizontal axis, houses a matrix of paralleled rods. From the feed box, slurry is introduced into the matrix as it passes through the separating zone.

The magnetic particles in the slurry are attracted to the surface of the rods in the matrix and are carried out of the separation zone to the top of the carousel once they are outside the separation zone.

While the matrix is still in the separation zone, gravity and the force of hydrodynamic pulsing of the slurry drag the nonmagnetic particles through the matrix pile onto the tailings box.

“Given that both technologies are highly capable of performing the task, both will be evaluated on a full-scale pilot plant, receiving less than 1 mm feed from jig modules one and two, from the SEP jig plant, which until now had been discarded,” says TWP senior project manager Leonardo Kleiman.

The pilot plant module will operate at full throughput, with the aim of the SEP 1B pilot plant being to generate a product of adequate quality and moisture content to be blended into the current less-than-8-mm products, produced by the SEP jig plant, he adds.

Kumba and its subsidiary company, the Sishen Iron Ore Company, will undertake a series of testwork campaigns to trial the two technologies to confirm the way forward for the second phase of SEP 1B.

The pilot plant operation will compare, evaluate and recommend one of the two competing technologies. This will require installation of three new modules to treat the fine material, which is less than 1 mm in size.

TWP’s projects division has also been appointed to start the preliminary design for this second phase. While waiting for the technology selection results, the company will start implementing the design of the areas where sufficient information is available to decrease lead design times.