MechChem Africa September-October 2024

⎪ Minerals processing and materials handling ⎪

tracting attention is the Decanter Centrifuge for the dry disposal of tailings. “Due to en vironmental concerns and/or critical water shortages, some mine sites cannot get a license to build slimes dams to dewater their tailings. Now these plants have a dewatered tailings disposal option. Our tailings decanter centrifuge enables these tailings to be contin uously dewatered to allow for safe stacking,” Hoffmann reveals. At the heart of what Wilna Hoffmann does is help mining clients to enhance the efficiency of their extraction processes. She has been do ing this for most of her 28-year career to date, with nearly half of that time with Multotec. “I continue to find this work inspirational and fulfilling, every day,” she passionately adds. Wilna's philosophy of life is that discipline is the bridge between dreams and accom plishments. She advises other women leaders in South Africa to focus on hard work and self-care, emphasising the importance of perseverance and having a positive outlook. Her management style focuses on leading and mentoring engineers to achieve high standards while enhancing overall team output. She values dedication, hard work and integrity, while striving to lead by example. Her work in a traditionally male-domi nated field has been both challenging and rewarding. Starting as a bursar in 1992, she was the first female student to work in a plant position at her assigned mine. Experiences such as these have shaped her perspective and resilience, and she is encouraged by the posi tive changes in the workplace over the years. Advocating for more young women to take up technical careers, she says that the mining engineering, minerals processing and extractive metallurgy fields are now far more comfortable places for women to work and are more accepted as the norm. “Dedication and tenacity are important in these some times difficult but often unbelievably exciting fields. But women can really do it and become extremely successful,” she advises. www.multotec.com

Left: Multotec’s decanter centrifuge enables tailings to be continuously dewatered to allow for safe stacking. Right: Multotec has developed a range of self-extinguishing flame-resistant rubber screen panels to mitigate the risk of fire.

ing and energy costs are significantly reduced and smaller, less expensive total solutions can be used. This makes bulk reduction a very cost-effective addition,” Hoffmann tells MCA. “In some cases, the concentrated mineral from a physical separation stage can be a sell able product. In these cases, we focus on the specification of the off-take agreement to produce an optimal yield final product that is in specification. “At Multotec, I find out from clients what they best need to feed into their downstream pipeline; I try to determine what the separa tion opportunities are; and the best technol ogy to use to deliver on this need. Because we have various technical solutions, we can iden tify a very wide variety of separation solutions to suit almost any ore body and requirement. Once done, I can hand a concept to our pro cess engineers to do the sizing and throughput calculations before recommending a holistic solution to the client,” she explains. While Hoffmann says that new Greenfield’s projects in South Africa are currently scarce, Brownfield expansion projects and efficiency initiatives to improve the yield from existing operations or to reprocess previously dis carded fines, are on the rise. “Over the years, we have been making steady incremental improvements to our processing equipment. Combined, these offer substantial gain op portunities on older plants seeking improved recoveries,” she notes. “We are involved in using spiral-based

reprocessing of tailings, because it is a low cost option. The expensive mining and milling are already done, so extracting the remaining percentages of value from historical tailings proves to be very cost effective. And latest-generation spiral technology can be used to concentrate and reprocess chrome, gold and many other minerals’ tail ings,” she says. She notes, in particular, the recent devel opment of the new Multotec UX7 ultra-fine chrome spirals, which have been purpose designed to improve the recovery efficiency in the fraction between -75 and -38 μm. “With traditional spirals, the recovery effi ciency falls drastically for the fraction smaller than 75 μm. Adding a UX7 spiral to recover this ultra-fine chromium from old tailings is proving to be a simple and cost-effective way of adding a value stream to an operating mine,” she explains, before reinforcing the need to fully understand the minerology of the tailings for best results. “We always strive to de-risk projects as soon as they come in, not just for the client but also for us, no matter how familiar we might think we are with the scenario. After looking into the size fraction, the composition of the tailings and the volumes, we will size and model equipment, and do efficiency and yield calculations. Then we will often do full scale verification tests based on the plant’s typical or best practices,” she adds. Another Multotec innovation currently at

September-October 2024 • MechChem Africa ¦ 17