The objective during TSF beach development is to still maintain a slurry that is pumpable and self-distributing at the tailings storage facility (TSF), rather than having to rely on trucks or on conveyors and stacking systems to manage a cake, but one that will deposit at a steeper beach slope than can be achieved by thickening alone. The use of ultra paste has the potential to broaden the range of topographic conditions that will suit thickened tailings discharge. This paper presents a case study for a large copper mine in which underflow from a series of paste thickeners with a nominal tonnage of 3,660 tph at 59% solids concentration would be mixed with 1,363 tph of filter cake at 80% solids concentration. The combined tailings (ultra paste) would be discharged equally into two open channels (flumes) at the combined solids concentration of 63.5%. The ultimate goal of adopting an ultra paste scheme is to produce homogenous consistency tailings, hence proper mixing of the paste and filter cake has to occur. In this study based on a series of tests, the mixing requirement has been assessed. The study also covers a conceptual investigation of natural turbulent mixing (NTM) of the filtered tailings with paste thickened tailings and issues associated with the deposition of the combined tailings, the ultra paste, into the existing TSF. In the conclusion, the study indicates that NTM can possibly occur only for the case in which the total tailings are discharged into one channel, which is not practical due to limitations with regards to tailings management. Hence, mechanical mixing has been recommended in this case.
The most commonly used dewatering technologies for the filtration of tailings from ore processing are pressure filters, filter presses, belt filters and rotary vacuum disc filters. The vacuum disc filter type in around 80% of all applications is the most economical of these technologies in terms of capital and operating cost, especially when modern high performance disc filters are used. The Boozer disc filter is a big diameter high performance vacuum disc filter that has set the pattern in a multitude of applications including the alumina industry and in dewatering coal slurries. In the past decade, this type of disc filter has established itself in applications of tailings dewatering, such as tailings from gold/copper, zinc and gold/silver mines. The reasons for its successful operation in tailings dewatering are: (a) high throughput and dewatering performance, (b) operational reliability even in the case of varying feed conditions, (c) simple and robust design, (d) ease of maintenance, (e) a small footprint. To achieve higher solids throughput rates, or to achieve the lowest possible filter cake moisture, HiBar filtration and HiBar steam pressure filtration offer new solutions in tailings dewatering. HiBar filtration and the HiBar steam pressure filtration are advanced continuous pressure filtration processes realised on rotary disc filters that are installed in a pressure vessel. The application of hyperbaric pressure of up to 6 bar (instead of a vacuum) ensures a high filtration rate and dewatering capability even with filter cakes of fine particles where high cake resistance and capillary forces in the cake must be overcome. With HiBar steam pressure filtration, the use of steam under special conditions improves demoisturing to the furthest extent, leading to the lowest values of moisture content. The drier HiBar filter cake improves the cake handling and disposal with steeper dumping slopes, resulting in reduced disposal area and improved safety of the disposal site.