Capital Equipment News January 2022

WET PROCESSING

“Optimised grinding with pump and cyclone performance is one example of ensuring we efficiently optimise both the energy efficiency and particle size cut to ameliorate metallurgical recovery while minimising fines generation,” says Douglas. “Flotation technologies such as MixedRow combine the unique performance of our nextSTEP forced-air with naturally aspirated WEMCO to ensure valuable minerals are not lost as tailings. Our array of advanced sensors such as LoadIQ, FrothVision and BulkExpert for Tailings provide the advanced sensing and process control needed to both minimise plant upsets and maximise performance,” adds Douglas. FLSmidth was recently chosen as the preferred provider for four large, bolted thickeners for a coal plant in Mozambique. Two of the thickeners are designed to reduce water load on the filters, allowing for a drier filter product, while the other two thickeners recover water from the plant tailings. The installation, which includes E-Volute feedwell technology, will contribute to achieving optimal water balance in the plant. Elsewhere in the African region, FLSmidth vacuum disc filters are playing a vital role at a new copper mine in the DRC in preparing tailings slurry for a backfill application. Four 3,8 m disc filters provide a cost-effective dewatering strategy, resulting in a cake dry enough to be mixed with cement and other additives before being transported underground to be placed in mined-out workings as backfill. Further afield, FLSmidth has completed an innovative project for Hindustan Zinc Ltd (HZL) at its Zawar location in India. The tailings dam at Zawar was reaching capacity for conventional wet deposition with no space nearby to expand. The company was looking for a tailings management system that offered significant benefits in terms of environmental sustainability, process water recovery and a reduced footprint for the tailings storage facility. “After evaluating several alternatives, HZL chose our dewatering concept, comprising a high-density thickener and E-disc filter technology. A key benefit of the system is the recirculation of more than 86% of the process water present in the tailings,” explains Douglas. Conserving water Dewatering of waste and concentrate streams as part of wet mineral processing is crucial to conserving water and to reducing mineral processing operational costs, says Multotec’s De Villiers. “Our filter press technology plays an important role here to recover maximum water and produce a dewatered product

“Our filter press technology plays an important role in recovering maximum water and producing a dewatered product suitable for economical conveying to the next process step or to discard the waste economically.”

Gerrit du Plessis, product specialist at Multotec

“An average size concentrator with a capacity of 100 000 tonnes/day can require 50 000 to 70 000 m³ of makeup water per day. Often our largest mineral resources are found and mined in highly water- stressed regions. To address this challenge, FLSmidth provides a full suite of technologies for water recovery, including thickened tailings, paste tailings as well as filtered tailings solutions that can recover up to 95% of the water used in the process.”

Wayne Douglas, head of R&D, Innovation and Minerals Testing & Research Center, Mining Industry, FLSmidth

“Although screening plays a minor role in the management of water in a plant, our view is that the ideal solution lies in reducing the amount of reject material processed by water. This can be achieved by eliminating the reject material in the upstream processes. For this reason, Kwatani is closely associated with world leaders in ore sorting technology.”

Kenny Mayhew-Ridgers, COO of Kwatani

TALKING POINTS

suitable for economical conveying to the next process step or to discard the waste economically,” he says. “Our filter presses can improve cake dryness, produce clean filtrate and reduce processing times by up to 10 minutes per cycle. Automated feed introduction, material discharge, pressing and filter cloth self-cleaning are features across this range.” Commenting on the benefits, De Villiers says waste streams generated in wet mineral and chemical processing streams result in increasing levels of contaminants and it becomes more difficult to separate the impurities from the water. Multotec supplies robust centrifuge technology to recover waste or product crystals after evaporation/crystallisation steps to provide a concentrated product or waste stream that is economically manageable by the end user. The water is recovered from the evaporation/crystallisation steps within specification and water can be re-used in the process again. Saleable products can also be produced by crystallisation, followed by dewatering, and product washing in the company’s pusher- type and Conturbex-type centrifuges. For high-purity product requirements the pusher-type centrifuge provides high washing efficiencies. Multotec centrifuges are used in many dewatering and classifying applications in the global minerals processing industry and are able to achieve accurate solid/liquid separation. Sourced from Siebtechnik Tema, they are of compact design, making them ideal for small operating areas. Commenting on some key case studies where this technology has been deployed, De

CAPITAL EQUIPMENT NEWS JANUARY 2022 20