Our process design is based on successes achieved and lessons learned from the many plants built in the past. Utilising our vast process development, design and project engineering capability and extensive operating experience, our plants ensure optimum capital and operating costs for high recovery of on-specification ferroalloy from the slag.
Our recovery plants are designed to recover ferroalloy metal from the slag dump by means of a gravity separation process with the slag material submersed in the water chambers of the jig. Mining, crushing, screening, slimes handling and water reticulation form part of the process.
This recovery is achieved by:
• Mining the slag material directly from the dump.
• Breaking the slag into smaller pieces in a crushing and screening system, releasing the locked metal from slag separating the slag into three size fractions.
• Separating the liberated metal and slag by means of a gravity separation process, using two jigs (one for coarse, one for fine) and a classifier for ultra fines.
All products of the process are managed in an environmentally safe fashion.
The slag is mined from the dump with an excavator and loaded onto dump trucks to haul it to the crusher feed bin.
The slag is crushed and screened into three fractions. The 6x25 mm (coarse) and 1x6 mm (fines) fraction is fed into the coarse and fines jigs and the <1 mm fraction is fed to the Atoll classifier.
In the coarse jig, >98 % clean metal is separated from slag and extracted as a 98 % clean saleable 6x25 mm metal product. The fines jig is used to recover 95 % clean saleable 1x6 mm metal from slag. The type of jig selected is an underbed air-pulsed jig, in which the water pulsations are produced by means of air pressure. The strength and pattern of the pulsations is controlled electronically, allowing the machine to be optimized for each particular application. A unique discharge system removes the metal from the jig bed. The jigs are controlled by a PLC, enabling tight control of process variables to deliver a clean product and to obtain recoveries of up to 99 %.
The <1 mm material is fed into an Atoll classifier and 90 % clean metal is extracted from the classifier.
The residual slag is discarded as a clean metal-free material, which is inert and can be used as aggregate.
Water is pumped from the water treatment system to the screen, jigs and classifier. The dirty water and the material washed through the screens are pumped back to the water treatment system. Slimes that are washed out on the screens are removed by the desliming cyclone. At the water treatment system, the solids (slimes and grit) are de-watered and stockpiled with the discard. After thickening, the slimes are dewatered and the supernatant water is returned to the gravity separation circuit.
The clarified water is then re-cycled back into the plant. This is a zero effluent closed-circuit plant. The only water leaving the plant is that which is adsorbed on various products (±8 %). For these small losses, a small amount of make-up water is added to maintain constant water levels.
Optimisation of SiMn production at Transalloys by K. Bisaka1, J. Griesel2 and P.H.F Bouwer3. 1 Mintek, Randburg, South Africa; Kabwikab@mintek.co.z; 2 Atoll, Johannesburg, South Africa; Johang@tbateman.co.za; 3 Transalloys, Witbank, South Africa; Henk@hiveld.co.za.
The recovery of chrome and manganese alloy fines from slag by JH van Reenen, H Thiele, and C Bergman.
Techno economics of recovering ferroalloys from dust and slag by Dr P D Scott.
23rd International Mining Congress & Exhibition of Turkey • 16-19 April 2013 ANTALYA - IMCET technical Paper - Download