The Debswana Diamond Company's water and residue strategy is aimed at reducing mine water consumption by 50% by 2008. Paste thickening of the tailings has contributed significantly to this goal, however, recent studies have indicated that a novel flocculant product (CIBA™ Rheomax™ ETD) may release significant amounts for water from the thickened tailings.The use of Rheomax™ ETD in two applications i.e. dosing prior to deposition at the disposal site and prior to a filtration step were assessed and the water savings and cost implications were compared to that achieved by conventional; high rate and paste thickening systems.
Different water qualities are found at each of the Debswana operations. Tests with water from three different operations were done, on the same ore samples, to study the influence of water quality on the dewatering characteristics of the resultant slurries. Using the same methodology and water, the different ore types produced slurries with different percentage solids and particle size distributions. For the same ore type, a change in water quality resulted in a change in slurry characteristics.The dewatering behaviour of the slurries, as expressed in terms of thickener underflow density, was related to ore type and water quality. Some ores from the different operations had similar dewatering characteristics. The ore type as well as water quality influenced the water demand of the process. It was concluded that the water quality plays an important role in the water recovery at the Debswana operations. This work showed that the water recovery can be improved if the water quality is controlled.
This work presents the experience with the application of a flocculent pipe reactor for flocculant evaluation and selection at Langer Heinrich Mine. Other processes could give different results. Parameters considered in determining the conditions that generate the optimum solids settling rate and overflow clarity are: slurry density, reaction time, turbulent shear rate (slurry flow rate), flocculent make-up concentration, flocculant dosing rate and type of flocculant. Two polyacrylamide flocculants used in the process were tested: Alclar 665 and Magna 333. The data was generated and processed in accordance with the response surface methodology. This methodology renders a mathematical model from which the optimum for each parameter in combination with the other parameters can be determined. The distinctive feature of this method of conducting settling tests is the ability to verify the interaction between parameters and higher order effects of parameters.
Langer Heinrich Mine (LHM) reports on the operational experiences of thickeners supplied by several vendors. Modifications that were made to mitigate challenges presented by the thickener operation are discussed. The in-house modifications to the Lightnin® thickener improved capacity, reliability and performance, and the modifications of which, are ongoing. The ANDRITZ Delkor (Pty) Ltd thickener modifications were successful and the thickeners are performing to specification. Indications are that the Roymec Technologies (Pty) Ltd thickeners will perform to specification. The Magra Ultrasep 2000 High Performance Thickener is still in the commissioning phase at the time of writing. The project is being developed in stages. Stage 1 was commissioned in 2006, Stage 2 followed in 2009, and Stage 3 is currently in the commissioning and ramp-up phase. Nine 25 m Lightnin thickeners and clarifiers were installed as part of Stage 1. The thickener functions were the following: one pre-leach thickener, six CCD thickeners, one clarifier, and one 'vanadium' thickener. The 'vanadium' thickener was converted to a clarifier during the ramp-up of Stage 1. Stage 2 development required an additional four 35 m thickeners. The 25 m Lightnin pre-leach thickener was replaced by a 35 m thickener, a 35 m thickener was installed as the CCD 1 thickener and two 35 m thickeners were installed as CCD 5 and CCD 6. These 35 m thickeners were supplied by ANDRITZ Delkor (Pty) Ltd. The Lightnin thickener configuration was changed to run as three sets of two parallel thickeners and performed duty as CCD 2 A & B, CCD 3 A & B and CCD 4 A & B. The 25 m Lightnin pre-leach thickener functioned as a standby pre-leach unit. Stage 3 upgrade required an additional two 35 m CCD thickeners; CCD 4 and CCD 7. These 35 m units were supplied by Roymec Technologies (Pty) Ltd. This necessitated a change in configuration of the Lightnin CCD thickeners. The Stage 3 configuration is comprised of two sets of three parallel thickeners; CCD 2 A, B & C and CCD 3 A, B & C. The chosen tailings deposition for the Stage 3 upgrade is a paste system comprising of a 12 m Magra Ultrasep 2000 High Performance Thickener, supplied by Magra Process Engineering (MPE), as the paste thickener, the pumping system designed by Paterson & Cooke (P&C) and a tailings storage facility (TSF) designed by Metago Environmental Engineers. A fourth stage expansion is currently in the bankable feasibility study (BFS) stage. https://papers.acg.uwa.edu.au/p/1263_13_Cooks/ Thickener experiences at Langer Heinrich Mine M. Cooks et al.
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