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PROCESSING SOLUTIONS APRIL 2016 • E&MJ; 79 www.e-mj.com AUSTRALIAN CENTRE FOR GEOMECHANICS Register in gecamin.com/paste E X EC U TIV E C OMMI T T E E C h a i r Hubert González Tailings and Water Management Manager, SCM Minera Lumina Copper, Chile E x EC u t i v E D i r EC to r Carlos Barahona General Manager, Gecamin, Chile t EC h n i C a l C o o r D i n ato r Sergio Barrera Senior Tailings Consultant, Delfing, Chile July 5-8 Hotel Grand Hyatt Santiago, Chile 19 th International Seminar on Paste and Thickened Tailings A R E A S O F IN T E R E S T Paste • Thickening • Filtering • Rheology • Chemicals • Tailings slurry transport • Pumping • Tailings beach slope • Testing • Case studies O RG A N I Z E R FO U N D IN G B O DY IN S T I T U T I O N A L PA R T N E R S Early Bird Registration until May 6 is based on the well-established Zwieter- ing correlation 1 , which essentially is an empirical ratio of the strength of agitation over the degree of solids settling. Of interest are the sedimentation depth H B and the solids dispersion height H S as defi ned in Figure 1(a). Figure 1(b) presents H B (normalized by H, the liquid height) as a function of S, determined from measurement. This curve is agita- tor design specifi c, but is independent of tank size. Once determined from mea- surements, e.g., in laboratory small scale tests, this curve can be used to assess sedimentation depth in a large tank for assessing the effect of variables such as particle size, impeller speed and diame- ter as implied in eq. (1). In Figure 1(b), solids could be said to be fully suspended when S>3.90 (~); sedimentation could be considered extreme for S<3. In our approach, Figure 1(b) is used to assess the status of sedimentation ini- tially, followed by assessing the feasibility of changing the parameters in eq. (1) to increase S in order to solve a sedimenta- tion problem, e.g., by increasing agitator speed or diameter or other parameters 1 . However, agitator power capacity and cost can often be limiting factors, such that it may be impractical to increase the speed. This problem can be overcome by adopt- ing swirl fl ow design with removal of baf- fl es. In such a change, the curve of S is typically found not to be greatly changed, but power is dramatically reduced (e.g., by ~30-50%). This allows an increase in speed or diameter to operate at a higher S parameter at an identical power input. This usually leads to increased off-bottom suspension and improved solids mixing and dispersion. Figure 1(c) illustrates a typical labo- ratory test result demonstrating applica- tion of a swirl fl ow design by removing baffl es; it shows that a reduced sedimen- tation depth (H B /H) is achieved at the same power requirement, but at a higher speed. Enhanced off-bottom suspension tends to correlate with enhanced disper- sion of solids, as evident from increased H S /H when baffl es are removed. Increased slurry dispersion height (H S ) corresponds to reduced stratifi cation and improved blending of solids of different densities. Figure 1(d) shows a recent photo of the slurry mixing research test tank at CSIRO in Australia (Melbourne). Here are a few examples of how appli- cation of swirl fl ow agitation design has resulted in favorable results at commer- cial operations. A total of eight iron-ore slurry surge tanks (each ~4,000 m 3 capacity) are employed by LKAB at Kiruna, Sweden. Some of Figure 2—Magnetite ore storage tank at LKAB Kiruna, Sweden.