Engineering & Mining Journal

JUN 2019

Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr

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102 E&MJ • JUNE 2019 www.e-mj.com PROCESSING SOLUTIONS FLSMidth developed its SAGwise total process control solution for semiautoge- nous (SAG) mills to provide effective mill optimization with lower energy consump- tion and wear part costs. Winston Mokoe- na, key account manager at FLSmidth, recently claimed that SAGWise can re- duce critical impacts inside the mill by up to 45% — prolonging service life of wear liners and grinding balls, helping to prolong liner life between maintenance and giving mills more uptime. "SAGwise can improve mill production by 6% and substantially reduce process variability," said Mokoena. "This ensures that the mill provides a constant and opti- mal feed to the next stage of the process, effectively facilitating better performance of downstream operations." Among the challenges that mill opti- mization addresses is too little material in the mill, or too much. Too little leads to critical impacts between the grinding media and the mill liners, damaging both elements without producing value. If the mill is overfi lled, on the other hand, this results in grinding ineffi ciencies. The SAGwise system uses four or eight unidirectional or bidirectional audio sensors located in close proximity to the mill, which detect analog sounds and convert them into digital signals for analysis by a processing unit. This unit uses the sound patterns and other process variables to determine the necessary adjustment to the mill's feed, speed and pulp density. According to the company, the improvements that can be achieved by this solution enable customers to pay back their investment in less than six months, depending on the commodity value and the specifi c mill environment. "The parameters that are monitored by SAGwise include the mill's power con- sumption, load impacts, mill load and pulp density," Mokoena explained. "The system then responds to these param- eters by controlling the mill speed, the feed rate and the water to achieve the 'sweet spot' where the mill runs at opti- mum effi ciency." New Paste Thickener Handles Tailings System Demands Tailings dewatering and disposal are challenges that almost every mining op- eration has to deal with, and Outotec recently reported its Second Generation Paste Thickener has been designed to maximize underfl ow density regardless of challenging mineralogy and tailings feed rate variation. Through consistent performance and high underfl ow density, the new thickener is claimed to maximize beaching angle in the tailings storage facility, leading to safer operations and maximized lifespan. "One such case was the deployment of Outotec paste thickener technolo- gy, including a full-scale paste tailings plant and ACT Thickener Optimizer sys- tem, at Yara's Siilinjärvi apatite mine in Finland," explained Simon Courtenay, product manager for the Outotec Second Generation Paste Thickener. "The plant generates around 10 million tons of tail- ings a year and thanks to the Outotec ACT Thickener Optimizer, the paste thicken- ers can consistently run with a high and stable underfl ow solids content of 66%- 68%, regardless of challenging mineral- ogy and tailings feed-rate variation. This results in average beach slope angles of 3.5° (6.1%) in the tailings disposal area, helping to extend its lifespan. The system has also enabled a 10%-20% reduction in fl occulant costs." According to the company, the new thickener provides ease of operation and reliability for applications requiring a high degree of dewatering, such as tailings, mine backfi ll, and pre-leach and CCD circuits. The technology can be custom- ized to address each operation's unique drivers, which can include environmental concerns, water recovery, regulatory re- quirements, tailings management or lim- itations on available land space. Outotec pointed out that it has a long history of designing paste thickeners and involvement in large-scale paste thicken- ing projects, providing deep understanding of the key aspects of high-density thicken- ers including effective fl occulation, dewa- SAG Mill Optimizer Listens in on Performance While operators often choose conservative mill parameters, FLSmidth's SAGwise system allows the equipment to run constantly as close as possible to its design limits.

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