Engineering & Mining Journal

APR 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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72 E&MJ • APRIL 2019 www.e-mj.com PROCESSING SOLUTIONS Separation technology specialist Eriez has published a white paper stating that performance metrics collected from in- stallations of its trunnion magnets world- wide indicate a six-month to one-year payback when compared with trommel screen installations. The report, titled Trunnion Magnet Technology Delivers Quick Payback and written by Eriez Director of Mining and Minerals Processing Jose Marin, explained how trunnion magnets function, high- lights their performance advantages, de- scribes retrofi tting options, and provides detailed economic justifi cation, including guidelines to assess savings potential. A graph illustrates how kilowatt usage can be reduced, with estimates for a typical 18-ft-diameter mill application resulting in savings of up to $100,000 per year. The trunnion magnet system for sepa- rating and removing balls, chips or scats in a typical ball/SAG mill operation en- ables an operation to replace the dead weight of ball magnets with fresh ore. The magnet is mounted at the ball-mill discharge point, replacing the convention- al trommel screen. It consists of a barrel or "blind trommel" that is mechanically attached to the trunnion or discharge of a ball mill. The barrel rotates around a fi xed assembly of ferrite and rare earth magnets positioned on the outside of the barrel. The stationary magnetic assembly attracts chips and scats to the inside diameter of the barrel. As the ball-mill slurry discharg- es through the barrel, eight strategically placed lifters inside the barrel carry the ball fragments to the top, where they fall on to a sloping discharge chute. According to the company, by effec- tively removing 80% or more of the worn or broken media, the magnet reduces power consumption from the mill drive and pre- vents expensive damage to other equip- ment, such as pumps and hydrocyclones. In addition to removing worn grinding me- dia from the ball mill discharge and saving energy, Eriez said trunnion magnets have other advantages that appeal to SAG mill operators. For example, they eliminate the need for a higher-cost trommel screen and its associated maintenance, they increase mill throughput up to 5%, and many in- stallations increase their mill work index through more effi cient grinding. Non-nuclear Slurry Meter Reads Percentage of Solids by Weight Rhosonics recently introduced its new Slurry Density Meter WT (SDM WT), de- scribed as a robust ultrasonic measuring instrument that provides slurry density value in wt% solids with an accuracy up to 0.005 wt%. The company said it has drawn upon its decade-plus experience in devising solutions for harsh applications to develop the SDM WT, which can measure the density of challenging water-based slurries. This type of meter, according to the company, is used mainly in mineral processing and dredging operations. Rhosonics explained that its fi rst SDM model, introduced in 2016, read density in S.G. x 1.000 or grams per liter; however, readings showing wt% solids output were preferred in the U.S. and Canada and Rho- sonics' earlier-generation Model 9690 has commonly been used to provide those re- sults. Now with the introduction of the SDM WT, Rhosonics can also offer a second-gen- eration non-nuclear density meter to U.S. and Canadian customers who demand wt% solids as the measurement value. Eriez Says Ball/SAG Mill Trunnion Magnets Offer Savings Eriez trunnion magnets available in several design variations allow matching with specifi c ball/SAG mill operations. Mill capacity, ball size and other parameters are used to select and specify the design features for each installation.

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