MINING CHEMICALS
and operations have seen reduced treatment costs and improvement to molybdenum concentrate grades with no significant downstream impacts .”
Nitrating conditions in Latin America Depleting grades and higher consumer demand from electric vehicle manufacturers and the like are not the only challenges copper mines in Latin America face , with solvent extraction operations also battling with the added problem of nitration .
Most copper solvent extraction operations in Latin America are now working with Solvay to overcome this and many other issues , according to the chemical company .
Rodrigo Zambra , Regional Sales Director LATAM at Solvay , explained the challenge : “ Ores across Latin America have a higher concentration of nitrates than elsewhere in the world . Nitrates degrade metal extractants . Mines , therefore , need a nitrate-resistant product for their solvent extraction operations but many of the options that have been conventionally employed have failed to adequately address the situation .”
Changes in ore feeds , due to mining new ore deposits or toll treating ore , may introduce nitrate salts to solvent extraction operations that previously had not faced this phenomenon , according to Solvay . The presence of nitrate in acid solutions can lead to the formation of nitronium ions , which react with oxime , resulting in nitro-oxime . The nitrated oxime binds with copper to form a highly stable complex , leading to higher viscosity and related physical problems . In addition , this copper complex cannot be stripped under normal plant conditions , generating a recirculation of copper in the organic phase ( residual copper ) that decreases the recovery and , thereby , the transfer of copper .
To enable mining operations to overcome nitrating conditions , Solvay has introduced ACORGA ® NR series copper solvent extractants to help mines protect against degradation of their solvent extractant . This , the company says , reduces extractant replacement costs and improves operational reliability .
Solvay ’ s offer extends beyond nitrationresistant reagents , with the company ’ s Metal Extraction group having developed a proprietary TAP ( Tert-Amyl-Phenol ) test methodology . This is a unique indicator of nitration aggressiveness , Solvay said .
The company also supports customers through advanced gas chromatography ( GC ) and liquid chromatography ( LC ) analysis , both of which are critical to assessing initial nitration conditions across customer sites in Latin America and evaluating the benefits of the ACORGA NR in those conditions .
Last year , a large copper solvent extraction operation in northern Chile faced nitration issues related to its oxime-adopted ACORGA NR at commercial scale . The problem occurred after a year of industrial trials in which the drop of oxime nitration was confirmed through GC and LC analysis . Solvay designed and performed more than 64 TAP tests in the lab , followed by two months of data statistical analysis to generate a 3D diagram , plotting the pregnant leach solution ( PLS ) nitration potential as a function of nitrate concentration and acid concentration . This tool enabled the operation to predict the nitrate conditions of the PLS entering its solvent extraction plant and adjust parameters to minimise the risk of nitration of the organic phase , it said .
Another plant in the region recently switched to ACORGA NR following two pilot plants run side-by-side at its site and at Solvay . The operation had been experiencing highly aggressive nitration conditions resulting in deficiencies in the solvent extraction process . This included higher residual copper , higher viscosity , lower production and extremely high extractant consumption . Although the operation was using a nitration-resistant extractant formulation , the test work demonstrated an imbalance between the amount of protector present in the organic phase and speed of formation of nitronium ions . This resulted in a fast consumption of the protector and , therefore , an increased extractant consumption to replenish the protector and maintain production targets .
The two pilots also showed that ACORGA NR , which contains a different protector than the incumbent formulation , is more resilient and can significantly reduce the nitration potential .
Switching to ACORGA NR has saved the operation well over $ 1 million / y in reduced extractant consumption , in addition to maintaining a stable solvent extraction plant and achieving copper transfer targets , Solvay said .
To facilitate the conversion to ACORGA NR by operations running other formulations when they encounter nitration issues , Solvay has developed custom “ booster ” formulations to ensure a plant reaches the appropriate concentration of protector in its organic phase at a speed much faster than standard make-up replacement .
Such boosters have been successfully used at numerous plants throughout Latin America that , after a few months , were running fully on ACORGA NR , Solvay said .
ACORGA NR series nitration-resistant reagents also have the same tailored metallurgical advantages when compared with unmodified reagents , including a reagent strength matched to the PLS conditions , improved selectivity and enhanced copper transfer , according to the company .
Selective chemistry , optimised physics
Having perfected its Imhoflot™ pneumatic flotation technology over the past 25 years , Maelgwyn is now looking to match reagents with the specific conditions of high-energy pneumatic cells as part of a research collaboration with South Africa-based chemical solutions provider Axis House .
In the quarter century since Imhoflot was introduced to the mining industry , it has evolved with multiple flotation cell designs for different applications , including vertically fed ( V-Cell ), tangentially fed ( G-Cell ), hybrid ( H-Cell ) and VC- Cell as the latest design for coarse particles . This has led to over 180 installations in operations such as coal , potash , kaolin , magnesite , copper , gold , platinum group metals , copper-molybdenum , lead-zinc and reverse flotation of silica .
The unique selling point of the Imhoflot system , the company says , is the superior graderecovery curve and the increased range of mineral particle sizes that can be recovered ( both ultrafine ( -20 μm ) and coarse ( -250 + 106 um )). This is achieved through high energy dissipation for the bubble-particle attachment and superior froth draining , which reduces gangue entrainment .
Maelgwyn says the research collaboration with Axis House will combine the selective chemistry of Axis House reagents with the optimised physics of Maelgwyn ’ s Imhoflot system . With little industry research carried out into matching reagents with the specific conditions of high-energy pneumatic cells , the two think this area is ripe for further investigation .
The Imhoflot aerator is a fine bubble generator that has secondary benefits when it comes to improving the performance of flotation reagents , Maelgwyn says .
“ For example , high turbulence in the aerator cleans the surfaces of minerals of both oxidation layers and adhered slimes ,” it said . “ This increases reagent selectivity and reduces the dosing required .”
Maelgwyn ’ s work in the European Union ’ s Horizon 2020 FineFuture project has pushed forward its competitive edge in ultrafine mineral flotation with base metal recoveries down to only a few microns , while maintaining the graderecovery curve .
Maelgwyn ’ s Imhoflot G-cell is optimised for ultrafine mineral recovery and is widely acknowledged to have several advantages over mechanical and column flotation associated with an increased recovery of fine particles , fast
54 International Mining | MAY 2021