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A new report from Eriez® reveals how a set of Magnetic Mill Liners (MML) are significantly improving safety standards, energy efficiency, and operational longevity at the Nexa Resources N.A. installation in the Central Andes of Peru. This is the latest international success story featuring the MML, a wear-resistant steel-encased magnet that combines the best qualities of steel and magnetic liners.
The report highlights the superiority of MMLs over conventional liners by describing the numerous benefits these advanced liners offer. Each MML is composed of individual sections that are much lighter than traditional liners, facilitating safer and easier installation procedures. Weighing only 20 to 40 Kg per section, the MML eliminates the requirement for specialized cranes within the mill, streamlining operations and enhancing safety protocols. Nexa even credits the MMLs installation with contributing to the company’s achievement of a major Peruvian safety award.
There are considerable environmental advantages associated with the implementation of MMLs. Heavier steel liners require enormous fuel consumption for transportation and material handling while lightweight MMLs can be installed by hand. Additionally, Nexa reports a significant reduction in noise levels with the MML, creating a more favourable work environment overall. The case study also highlights the energy-efficient aspects of MMLs. In traditional ball mills, small ball chips do not contribute to the grinding process, leading to wasted energy. However, MMLs effectively eliminate the presence of small ball chips, resulting in energy savings of up to 11% during the grinding process.
The exceptional durability of MMLs is another standout feature discussed in the report. Unlike conventional liners that necessitate frequent replacement, the Eriez MML has garnered a track record of success through many installations in diverse mining operations worldwide, including iron ore, copper, nickel, and gold mines, as well as other nonferrous mines. These installations provide evidence that MMLs outlast rubber or metallic liners by two to three times. The magnet holds the metal magnetic liner to the shell and retains ball chips and magnetic minerals to form a solid protection layer which serve as the wear liner. The ball chips and magnetic minerals are retained continuously and therefore the liner may last for years without any maintenance. The metal magnetic mill liner with the longest service life has been in service for over 10 years. Installations show that magnetic mill liners are safe and easy to install and drastically reduce maintenance costs. They also increase mill availability, prevent back washing of mill shell, can lower medium consumption, reduce noise levels, reduce/eliminate mill leakage as well as improve the working environment. Magnetic Mill Liner applications include secondary ball mills and regrind ball mills.
The metal magnetic mill liner has been in use for years and has provided higher grinding efficiencies. The thickness of the metal magnetic liner with the protection layer is less than that of a conventional liner, resulting in a greater working volume. The metal magnetic mill liner also creates a wave form that is generated by the magnetic force and provides optimal attrition by lifting the material being ground. The higher attrition results in less abrasion and impact, which promotes a higher charge pressure and grinding efficiency. Grinding ball chips and other debris discharged from a ball mill can cause extreme wear to downstream processing equipment. These ball chips and debris can circulate in the milling circuit and can cause excessive damage to pumps, cyclones and piping. Energy is unnecessarily consumed as these ball chips and debris must eventually be ground to a particle size small enough to allow for its discharge from the mill circuit through a cyclone overflow. Instead, the metal magnetic mill liner will adsorb the ball chips and debris to its surface and prevent its discharge from the mill while the solid protection layer is formed. The smaller sized ball chips are sorted out and separated from the primary ball charge. These ball chips and other debris work as the liner and no excess energy is required.