SEPARATION
Electro Overband Magnets at a Russian coal operation
Exploiting differences
Paul Moore homes in on developments & available solutions in some of the core technology areas used in mineral separation with a focus on magnetic and gravity methods
Separation in mining is a broad church and includes equipment using technologies based on magnetic , gravity and density methods , which have a vast range of applications from gold processing to iron ore , coal and other minerals such as tin ores and mineral sands but also non-metallic industrial minerals . It includes a lot of very specific solutions for very specific problems , with each niche often involving only a few potential suppliers and technology designs . As in the rest of the industry , a lot of current focus is on reduced use of water and energy but also recovering what was previously regarded as waste .
Starting with magnetic methods , whether protecting processing equipment or enhancing mineral purity , magnetic separation plays a key role in many mining and mineral processing operations . Bunting is one of the world ’ s leading designers and manufacturers of magnetic separators for the mining and mineral processing industries with European manufacturing facilities in the UK .
Magnetic separators utilise either permanent magnets or electromagnetic coils to generate magnetic fields and are used to either remove costly and damaging tramp iron or for mineral beneficiation . Tramp iron occurs in the form of steel nuts and bolts , pit props , and even blasting caps , damaging crushers , screens and conveyors . Removal commonly occurs early in the process , before the primary and secondary crushers and screens .
Bunting told IM : “ The three most commonly used tramp iron magnetic separators are Overband Magnets , Suspension Magnets and
Magnetic Head Pulleys . Overband and Suspension Magnets sit above transported ore , whilst Magnetic Head Pulleys replace standard head pulleys . In all three cases , tramp iron is attracted to the magnetic field and automatically extracted . Overband Magnets are the most commonly used magnetic separators and include a self-cleaning belt to transport captured iron away from the conveyed ore into a collection area . Suspension Magnets ( Overband Magnets without the self-clean gear ) hold the metal on the magnet face until manually-cleaned . Magnetic Head Pulleys attract metal to the conveyor surface , depositing underneath on leaving the magnetic field . Recent Overband Magnet installations include a gold mine in Bulgaria and coal processing plant in Russia , with a Swedish iron ore processing plant using a number of large diameter Magnetic Head Pulleys .”
High-intensity magnetic separation enables the recovery or extraction of para and ferro magnetic minerals . Such technology is widely used in the processing of non-metallic minerals , as well as specialist applications including coltan , beach sands and iron ore . Once again , the magnetic force is generated by either high strength rare earth permanent magnets or electromagnetic coils .
Bunting adds : “ High-intensity Drum Magnets and Rare Earth Roll Magnetic Separators utilise the extreme magnetic force of permanent neodymium rare earth magnets . In both technologies , a tightly-sized , dry mineral feed passes over the drum or roll surface , with magnetically-susceptible minerals attracted , deflected and separated using a strategically
placed splitter . The electromagnetic Induced Roll Magnetic Separator operates in a similar way with a magnetic field generated electromagnetically . Non-metallic minerals such as feldspar , silica sand , and zircon are purified using these high-intensity magnetic separators .”
The Magnetic Disc Separator features up to three electromagnetic discs spinning above a monolayer of dry tightly-sized minerals . Each disc is set to lift and separate minerals of differing magnetic susceptibility . Such technology is widely used in processing coltan and beach sands .
Finally , Electromagnetic Filters and Wet High Intensity Magnetic Separators ( WHIMS ) enable processing of mineral slurries . Single batch-fed or dual flip-flop Electromagnetic Filters remove weakly magnetic particles from non-metallic minerals , whilst the WHIMS commonly concentrates magnetic minerals .
The company adds : “ Controlled laboratory testing of diverse and often complex mineral deposits identifies the optimum high-intensity magnetic separator for any given application . Many mining operations , especially in Europe , are focused on developing reserves requiring higher levels of processing or reprocessing materials previously classed as waste . Both increase the need for magnetic separation , whether to protect or purify .”
Eriez on how magnetics are adapting in core markets
Jose Marin , Eriez Director , Minerals and Materials Processing gave IM some insights into magnetic solutions for higher purity industrial mineral separation for which demand continues to grow as new applications are released throughout the world . “ What does this mean to the producers of industrial minerals who proudly produce their products , but find that the production run from yesterday will no longer suffice ? Companies that do not want to get left behind must drive technological advances to produce newer , more state-of-the art equipment . Equipment advancements give companies the keys to unlock doors to new applications in changing markets . Magnetic separation is an important technology that can help make significant improvements in products and minerals by delivering increased recovery . Like most technologies , magnetic separation equipment manufacturers are constantly searching for improvements and efficiency gains in all possible processes to stay relevant and remain on the cutting edge .”
The dry vibrating magnetic filter is a unique piece of equipment for processing very dry fine industrial minerals and materials requiring an
44 International Mining | APRIL 2021