Reprocessing and tailings reduction.qxp_proof 29/04/2020 09:50 Page 1 REPROCESSING AND TAILINGS REDUCTION In Colombia, AuVert's technology is being combined with CDE's experience in dewatering Profits from the past and tailings management to extract the remaining precious metals existing in the ground, while removing up to 93% of residual mercury which has to date prevented this land from being used by the local population reasons why mining companies may be cautious about using tailings as backfill material or relocating current day ‘waste’ to an inaccessible area of the mine, according to Gerritsen. “As technology improves, the opportunity to recover more of the metals/minerals increases,” he said. “There are elements where that may not be the case – coal ash, for example, cannot be reprocessed but can be used to produce cement. While tailings dam liabilities and falling water resources are There are certainly opportunities with gold, affecting the ability of miners to start new mines, or expand copper and even coal, for instance.” The strategies companies ultimately pursue for existing ones, these issues are strengthening the case for these ‘waste streams’ depend on the technology reprocessing and retreating ‘waste’ sites or streams. Dan available and the safety of the facilities, Gerritsen Gleeson explores an increasingly diverse market focused on remarked. revenue generation and risk reduction “For instance, it may not be economically viable to reprocess the material currently in a ith improved transparency around recycling and thickening, or SART, plant from BQE tailings storage facility and, therefore, the owner tailings dams and waste stockpiles now Water will only bolster cash reserves through the may decide to close it or put it into a non-active Wpart and parcel of being a responsible recovery of a high-grade saleable copper sulphide state,” he said. mining company, investors and the wider mining product, the re-generation of cyanide (a major One company looking to address the world are becoming aware of the opportunities to operating cost at Parral) and an improvement in availability and cost of specialised technology for clean up legacy operations, while, at the same the leaching efficiency of the heap. reprocessing tailings and other ‘waste’ is CDE. time, generate extra revenue. In Africa, the likes of Goldplat and Jubilee An industry-leading manufacturer of wet These opportunities are growing in value and Metals Group have been profitably processing processing equipment for materials processors, quantity as water scarcity in many major mining gold and platinum group and base metals from CDE has seen a significant rise in proposal hubs accelerates and the ability to expand waste streams for many years. requests for dewatering and dry stacking existing tailings impoundment areas diminishes. Central Asia Metals built its name on the equipment over the previous 12 months, The trend is further aided by the fact costs and Kounrad asset, a copper dump leach operation in according to Kate McCormick, Mining Sector liabilities associated with these facilities continue Kazakhstan, which, through reprocessing and SX- Executive at CDE Meta. to increase. EW, has produced more than 100,000 t of copper Most requests have focused on re-processing At the same time as this, these opportunities cathode since operations began in April 2012. existing tailings, recovering the valuable are becoming more feasible as the cost of The list goes on. fractions, and dewatering and dry stacking the specialised equipment drops – making the upfront waste products, she explained. capital expense more manageable – and the number Removing the ant heaps “We are increasingly approached by clients of large mining companies looking at removing “Reprocessing is one strategy, if it’s worthwhile seeking to recover value from their waste these ‘liabilities’ from their portfolios expands. from an economic standpoint,” Theo Gerritsen, stockpiles, which have accumulated in times This has seen a new generation of ‘miners’ Stantec’s Global Tailings Practice Lead, said in where high-grade ore was abundant and lower spring up intent on profiting from processing response to a question about what strategies grades were set aside as waste, or processing material previously categorised as ‘waste’. miners were evaluating for legacy tailings technologies were not sophisticated enough to New Century Resources, for instance, emerged dams/waste stockpiles within their portfolios. capture fines fractions or suitably upgrade the in 2016 to restart the Century mine in Speaking from his home office in Brisbane, ore deposit,” she told IM. Queensland, Australia, through an initial tailings Australia, in April, he reflected on his time McCormick said CDE was receiving these reprocessing operation after the much larger working in South Africa to provide some requests from smaller mining companies looking MMG had decided the asset had reached the end evidence: “For example, at one point, in the to specialise in reprocessing brownfield sites. of its profitable life earlier that year. The middle of Johannesburg, there were these giant “Increasingly we are seeing junior miners Australia-based base metal producer is now ‘ant heaps’, old tailings which were processed adopting a strategy of purchasing waste dumps aiming to become one of the world’s top 10 zinc 100 years ago by gold mining companies. or historic tails for re-processing as an economic producers through a ramp up of operations at “These ‘ant heaps’ had more gold in them than source of commodities,” she said. “This value is Century to 12 Mt/y. most current day gold mines. Because the easy to recover as the material has already been GoGold Resources, in Mexico, is using the technology at the time was not very sophisticated, mined and avoids the substantial extraction costs proceeds from heap leaching the Parral tailings they could not recover as much as they can now. of virgin mining, yet these tailings deposits operation, in Chihuahua, to progress with its Most of those historic tailings have now been contain high recovery rates with existing projects, exploration projects in the country. The recent reprocessed.” for example, recovering 2 g/t Au and achieving addition of a sulphidisation, acidification, This reprocessing opportunity is one of the 63% Fe grade at 50% yield.” 10 International Mining | MAY 2020 There’s nothing worse than an unknown variable and there’s nothing more variable than water. Floods, torrential downpours, moving water from A to B – it can very quickly get out of control. That’s why the Weir Minerals team works tirelessly with sites to design tailored dewatering solutions. We use our expertise in both process and products to maximise efficiency and help you take control of your water. DEWATERING Learn more at dewateringsolutions.weir SOLUTIONS Minerals Copyright © 2019, Weir Minerals Australia Limited. All rights reserved. www.global.weir Reprocessing and tailings reduction.qxp_proof 29/04/2020 09:50 Page 2 REPROCESSING AND TAILINGS REDUCTION It is the junior and mid-tier miners – not the Tier SIMEC installation is the company’s largest valuable materials for the construction market and 1 outfits – able to more easily incorporate the new processing facility for low-grade beneficiation. incorporates patented Infinity Screen technology technologies CDE and others offer to carry out The project will see almost 18 Mt of low grade, for optimal dewatering results, Holland added. such processing, according to McCormick. extremely abrasive hematite iron ore turned into a The CDE AquaCycle water management system “Contrary to the assumption, I think the saleable product for SIMEC in South Australia. provides the required high rate thickening to transition to dry stacked/filtered tailings is more The two plants on site remove silica and recover up to 90% of the process water for re- accessible to junior and mid-tier miners who have alumina from the feed material, gravity separating circulation around the washing plant while increased flexibility to incorporate new low-grade from high-grade ore in the process. thickening a tailings sludge. technologies into their plant design,” she said. Silica levels, which range from 14% to 20% in the “The AquaCycle M offers a fully modular skid “For Tier 1 miners, the scale of dewatering existing barren ore, have reduced to 6.4% after processing; mounted option for customers who want to avoid and historical dams presents significant while alumina levels, which range from 5.9% to civils work,” Holland added. commercial risk due to the expense involved.” 8.8%, have reduced to 2.8% after processing. CDE’s Plate Press filtration system is designed The company has a few case studies to back The iron ore wash plant also removes clays from and built to deliver maximum plant efficiency, this opinion up. the feed material, with the combined effect eliminating the need for tailings dams, or settling moving the iron content from between 43.4-52.7% ponds and significantly reducing waste handling, Zero-waste initiative Fe in the feed to 63-64% Fe at a yield of 50%, according to Holland. “The market-leading In working with junior miners from prefeasibility according to McCormick. automated cloth wash system delivers maximum through to development stage, CDE offers cost- The plant consists of an initial washing and dewatering performance, recycling up to 95% effective modular equipment design to achieve screening stage using CDE’s M-Series™ modular process water,” he said. minimal