SEPARATION
“ Taking ferrochrome samples from a number of mines over a period of two to three years , we conducted extensive test work on these at our well-equipped testing facility in Spartan near Johannesburg ,” he says . “ Leveraging this data with our in-house engineering design capacity , we were able to develop the optimal solution and locally manufacture the new spiral concentrator .”
The institutional knowledge within Multotec has been developed over more than four decades , including valuable expertise in fluid dynamics . Hands-on experience in test work and design allows the development of prototypes that solve customers ’ specific challenges – followed by scaled-up local production of equipment to match market demand .
The economic benefits of the Multotec SC25 spiral for ferrochrome producers are substantial , as some plants were losing the value of their 1 to 3 mm material to the tailings storage facility . Many of those who used jigs to treat this fraction were also finding that their efficiencies were low .
“ Ferrochrome is not the only commodity that we have successfully tested ,” says Refentse Molehe , Process Engineer at Multotec . “ We have even seen improved recovery in heavy minerals below 1 mm size , alluvial chrome , manganese slag and there is potential in industrial recycling .”
The recycling application opens up options for ‘ urban mining ’ – the recovery of metal particles from associated waste . Multotec has received a number of requests and conducted tests to recover metals from recycled electronic goods and from customers who intend to recover metal from industrial scrap .
FLSmidth launches GX Concentrating Cone
Moving on to advanced gravity separation , and the latest innovation in semi-continuous gravity separation from FLSmidth is delivering a key breakthrough in performance that increases recovery and cuts maintenance downtime , according to the OEM . For decades , Knelson gravity concentrators have been recognised for their recoveries of gold and precious metals , but the development of the new Knelson GX Concentrating Cone is set to take this performance a step further .
The new patented GX Cone delivers impressive recovery enhancements due to enhanced water distribution within each ring , according to the company . FLSmidth explains : “ As water enters from the base , it flows through zone separator nozzles for a customisable fluidisation profile . This allows for even distribution of water in each ring ; the new design also significantly increases the active recovery surface area . The result is a step change in overall coarse and fine gold recovery .”
AKW A + V enables ultrafine sand recovery with cyclones
Looking again at industrial minerals , since most of the existing silica sand processing plants are not designed for ultra-fine sand recovery , a significant amount of product is lost in the 0-150 μm range . In order to reduce this loss of product and maximise the recovery of fine sand , as well as reduce the load on sludge sedimentation ponds and ensure a better water circle management , the R & D department of AKW Equipment + Process Design has been intensively involved in the designing of a new process . This was followed by the development of a customised technical solution combining ultrafine hydrocyclone classification with dewatering of critical sand material , the so-called AKA-SILT System . From an existing treatment plant , approximately 200 m ³/ h of solids-laden process water is fed to a pump sump via a pump . With an additional wear resistant slurry pump , the suspension is fed to the first hydrocyclone stage , the AKA-SPIDER annular distributor . An installed antiblocking filter , AKA-STRAINER , retains any larger particles that may be present and thus avoids blockages in the distributor , which could lead to variances in the classification . The material is classified at 10 μm by using small polyurethane hydrocyclones AKA- VORTEX . The hydrocyclone overflow with the fines 0-10 μm is discharged into the sedimentation pond , whereas the hydrocyclone underflow fraction 10-150 μm is directed by a pump to the second hydrocyclone stage . The AKA-SPIDER annular distributor , also equipped with polyurethane hydrocyclones AKA-VORTEX , is used to thicken the fraction 10-150 μm . The hydrocyclone overflow from this second hydrocyclone stage is returned to the first stage circuit . The discharged hydrocyclone underflow 10-150 μm is fed onto the dewatering screen , dewatered and then stockpiled by a conveyor belt . The underflow of the screen is returned to the pump sump of the second stage . Both products , the ultrafine sand ( 10-150 μm ) and the pure clay ( 0-10 μm ) are marketable as products for further processing industries . The significant reduction of the fines content in the suspension leads to a high economic , ecological and efficient water treatment and also to a relief from any downstream installed sedimentation ponds or thickeners .
The AKA-SILT system can be installed as an additional unit in existing plants and achieves the highest environmental standards as a 100 % chemicalfree process . With this new system , it is possible to benefit from an environmentally friendly process unit that can process fine material which normally is discharged in ponds .
Test data shows that gold recovery in all size fractions , from coarse to fine , improved significantly with the FLSmidth Knelson GX Cone
The AKA-SILT system can be installed as an additional unit in existing plants and achieves the highest environmental standards as a 100 % chemical-free process
Test data shows that gold recovery in all size fractions , from course to fine , improved significantly with the GX Cone , according to the company . By incorporating an advanced distribution of fluidisation water across the entire concentrating cone , the Knelson GX facilitates the highest possible recovery of coarse and fine gold . At the same time , balanced water distribution across the concentrating cone allows for a significant reduction in fluidisation water requirements while improving recovery .
The third major benefit of the Knelson GX is easier maintenance . Because it is made of a customised , abrasion-resistant and durable polyurethane compound , maintenance frequency and operational costs are significantly reduced , FLSmidth says . Mike Lefler , Head of Global Product Line Manager for Precious Metal
50 International Mining | APRIL 2021