The filtering of sandy tailings from the reverse cationic flotation processes and the subsequent stacking of these tailings has shown to be a very strong trend in Brazilian iron ore mining, especially after accidents involving geotechnical structures known as tailings dams, but also due to concern of mining companies to develop a disposal technique that is more complacent with the environment and the surrounding society. In order to develop the sandy tailings filtration project, a fundamental requirement was the correct choice of filtration technology among the many existing ones. For the material object of this study, the filter with vertical discs presented itself as the most productive due to factors such as granulometry, specific surface of the material and the humidity required in the filtration product. Several exploratory and material characterization tests were carried out for this purpose. Disc filters have the principle of operation linked to the difference in atmospheric pressure and the vacuum pressure induced by pumps. The vacuum must act on the filtering screens next to the filter heads and, in order not to drop the yield, the system must be sealed hydraulically. As previously mentioned, there are basically two ways to hydraulic seal the system. The first and most common in Brazilian iron ore filtration is carried out through barometric columns and the other is using filtrate pumps installed directly in the vacuum receiver of the filtration facilities. The decision of which method to use has major implications for the design of the filtering installation and the comparison between the two conditions mentioned is the objective of the present work.
Over the last few years, there has been a substantial increase in the degree of complexity of requirements regarding the licensing of tailings dams in Brazil. The stacking of filtered tailings is currently proposed as an alternative solution for tailings storage facilities; however, there are numerous challenges to understand and manage these structures in regions of high rainfall and high disposal rates. In this context, the objective of this article is to evaluate the liquefaction susceptibility of filtered iron ore tailings, based on field (piezocone) and laboratory tests (characterization and triaxial compression), both performed at an experimental landfill, located in the Iron Quadrangle (Quadrilátero Ferrífero), Minas Gerais state, Brazil. Therefore, a few methodologies were used to evaluate liquefaction susceptibility by means of the critical state theory, furthermore the fragility index of the material were also evaluated. Results indicated that the constructive method used in the experimental landfill (i.e., compaction energy, moisture and layer thickness) resulted in variability in the in-situ void ratio, indicating susceptibility to liquefaction for materials on depths greater than 0.75 m from compaction surface. In addition, from laboratory tests it was possible to determine the critical state line of the filtered tailings.
?A new trend in Brazilian iron ore beneficiation processes is the concentration of ultrafine minerals. Such minerals are currently disposed in dams or similar structures despite having a high iron content. With the development of new reagents and new concentration methods, it was possible to concentrate this type of material, however, the tailings from the concentration of these materials must still be disposed. Another upward technique in iron mining in Brazil is the disposal of filtered tailings in the tailings pile (PDR). In order to be able to dispose of ultra-thin materials in the aforementioned manner, it is necessary to perform the filtration using the press filter technology, which is the most suitable to process this type of material. In press-type filters the dewatering is somehow accomplished through the pressurization offered by the pumping system responsible for feeding the filters. The present work aims to present a case study of filtering of ultrafine tailings essentially addressing the various ways studied for feeding and pressurizing filter presses through variations between available technologies. To evaluate the best feeding method, pilot scale tests were performed to determine the specific filtering conditions of ultrafine material. Parameters such as pumping time, filtering time and total cycle time were determined from which scale-up factors were applied to enable the sizing of pumping capacity on an industrial scale. Finally, data from similar systems were used to calibrate the resistance curve of the cake and the AFT Fathom software based on Wilson's theory for mineral slurry handling was used to evaluate possible feed forms. Items such as energy consumption, pumping pressure stability, dewatering efficiency and acquisition cost will be compared.
?There is an increasing trend in iron ore mining in Brazil regarding the disposal and treatment of sandy tailings from concentration processes by reverse cationic flotation techniques. Filtering and later disposal of sandy tailings in piles known as PDR (Tailings Disposal Pile) has been shown to be a rising method to the detriment of known tailings dams. In the case study in question, the tailings thickening operation is too far from the filtration and stacking point, so it was necessary to consider a material transport mode between the two operations (Thickening and Filtration), which was the tailings pipeline. The pipeline is 6.7 km long tail and 52.0 m static lift designed to operate with process variations especially in terms of percent solids and variations in the beneficiation plant rate. The drive consists of five centrifugal pumps with 600 HP motors and the piping follows the ANSI B36.10 dimensional standard and the API 5L Grade B material standard with 16 inch diameter. To support the pipeline sizing a fundamental step was to perform the characterization of the material to be transported. Several tests were performed of granulometry, rheology, abrasiveness, solids density, slurry corrosivity, inclination angle of the pipeline, among others. The results of the tests were used to calibrate the mathematical models. The pipeline was evaluated considering the steady-state and transient flow regime. The results of the steady-state analysis made it possible to specify the quantity and model of the pumps, as well as to evaluate the velocities and pressure losses. The transient analysis, however, was performed to identify the operating scenarios that lead to the highest pressures and thus confirm the characteristics of the pipelines and consider the necessary hydraulic protections.
?Turmalina Mine has been unsuccessful on mining a high-grade thick zone of its orebody using a sublevel stoping bottom-up sequence with rock fill by having high dilution and ore losses. Being one of few mines in Brazil with a paste fill plant, Turmalina Mine that used to paste fill only open stopes in old areas saw as an alternative using paste fill on a primary and secondary stoping sequence to reduce probability of ground falls and successfully extract ore from the high-grade thick zone without leaving rib pillars, increasing recovery Empirical formulas and Map3D boundary element numerical method - were used to define needed plug and mass fill strengths to reduce risk of liquefaction, to use paste filled areas as working platforms and for vertical exposure after secondary mining with low dilution. A binder created for Turmalina tailings considering its rheological characteristics to achieve good flowability and sufficient compressive strength made possible to reach an optimal cycle, combining low binder utilization and sufficient compressive strength for each step of the cycle confirmed by uniaxial compression tests done in specimens with different binder content and ages. Filling consists of a 5% plug fill and then a 3% mass fill after a two days wait for the plug fill to reach 100kPa. Filled stope is ready to serve as a working platform after 3 days, when it reaches 170kPa. Secondary stoping is sequenced after 28 days when mass fill finishes, as it is ready to have a vertical exposure with a strength of over 500kPa. Paste fill specimens collected are tested to confirm the strengths needed before each step. By implementing paste fill in the sublevel stoping sequence, the mine is planning to control operational dilution at a maximum of 15% and increase ore recovery to 95% in the high-grade thick zone.