Supplier of materials processing techno- logy Humboldt Wedag South Africa (HWSA) has supplied a pilot batch jig to raw materials supplier Assmang’s Khumani mine laboratory for ongoing ore testing.
“This unit is identical to the pilot batch jig used at parent company KHD Humbolt Wedag’s research and development (R&D) facility in Cologne, Germany, for the Khumani ore testwork,” HWSA MD Johannes Kottman says.
Humboldt Wedag has over 160 installations of the Batac jigging systems worldwide, including eight plants in Southern Africa. Kottmann says that jig technology in iron-ore was introduced because it was proven to be comparatively more viable to separate or beneficiate iron-ore through jigging rather than using conventional separation technology when ores have a relative density greater than four.
This year also marks the tenth year since the first Batac jig was commissioned in an iron-ore application in Southern Africa.
“Humboldt Wedag’s association with Assmang, jointly managed by Assore and African Rainbow Minerals, dates back to July 1995 when KHD Humboldt Wedag received an order for the supply of a fines jig and a lumpy jig, each 1 m wide, for Assmang’s Machadadorp ferrochrome operation,” Kottmann says.
In 1998, extensive testwork was under- taken on contaminated iron-ore and discard at the Beeshoek operation, in conjunction with KHD Germany and a German iron-ore research institute, SGA. The outcome resulted in a jig-plant design and layout being undertaken at the mine.
Further, an order was received by HWSA from Assmang in December 1999 for a turnkey jig plant with two 3-m-wide Batac jigs. The jigs, with a combined nominal capacity of 465 t/h, treated fines and lumpy ore.
Following the commissioning of this plant, various optimisation initiatives were carried out by Beeshoek and KHD Humboldt Wedag, resulting in a sustainable combined jig capacity of about 570 t/h.
“This relationship extended to the Khumani iron-ore mine where extensive test work was again carried out at KHD’s R&D centre and at SGA to assist the mine in fingerprinting the orebody, and to develop and design the process flow diagram for a jig plant to treat lumpy and fines material. This off-grade beneficiation circuit included the recovery of a middlings fraction from the lumpy jig discard,” Kottmann says.
The testwork started in February 2004 and culminated in the award of an order in February 2006 for four complete jig lines, each about 4 m wide and 4 m in length, for treatment of lumpy and fines material with a total capacity of 1 280 t/h. The installation and cold commissioning of the jig plant was completed in mid-2008 and hot commissioning started in September 2008. In addition to the jigs, HWSA supplied vibrating screens to be used for dewatering on the jig overflow.
With the exception of some ancillary equipment, the balance of KHD’s proprietary machinery included jigs, screens and bucket elevators. About 75% of the contract value was manufactured in South Africa with the majority of the contractors being black economic-empowerment compliant, while technology support was supplied by HWSA’s parent company, in Germany.
“This contract was significant as the lumpy ore jigs have a middlings section, which means that in the lumpy ore process, two cuts will be taken: a product cut and a middlings cut, for retreatment to ensure optimum recovery,” Kottmann explains.
“In each of these installations, Batac jigs were selected. Part of the principles behind the decision to use these jigs at Khumani was the performance of the jigs at Beeshoek, which clearly indicated the viability of using these jigs for iron-ore beneficiation,” Kottmann explains.
Further, he adds that the prime advantage of the system is its accuracy, its relatively small size and low capital costs. The accu- racy is ensured through the electronic control of the air pulse generator, and the sensing of the thickness and densities of the material layers being separated.
The programmable logic controllers (PLCs) used on the Batac system allow the amount of air to be set individually for each jigging chamber and an identical pulse frequency can be maintained over the whole area of a large jigging bed. This allows uniform separation for large amounts of material simultaneously at pulse frequencies from anything between 40 strokes a minute and 120 strokes a minute. This technology also provides for jig compartments up to 7 m wide, which equates to a 600-t/h throughput in iron-ore.
An electronically equipped float senses the thickness of the material layers passing over the jigging bed and uses analogue displacement systems set to work at supersonic speeds.
The hydraulic system, which controls the discharge gates on the Batac jig, operates by means of controllers actuated by the main jig PLC, which contributes to a reliable production process. A high level of controllability ensures high accuracies in separation, even if the materials being processed are typically considered difficult to separate.
“The success of this project has contributed to a trend, which has seen the rejuvenation of jigging in ores and, in particular, in iron-ore. The Batac pneumatic jigging system has repeatedly proven to be a cost-effective alternative for coal, ferrochrome, manganese and iron-ore recovery,” Kottmann concludes.