This bulletin describes various methods of tailings transport (slurries vs. dry tailings), tailings placement (cyclone, spigot, paddock, mechanical placement), and decant systems. The bulletin is intended to provide advice for design of these elements based on project-specific characteristics. The bulletin also provides guidance for assessing the water balance of a tailings impoundment.
This bulletin provides references to publications written up until 1989 on tailings dams. It divides the references into the following categories: Tailings Sources; Deposition and Disposal Techniques; Safety and Failures; Stability of Tailings Embankments including Seismic Aspects; Material Properties and Evaluation; Legal Aspects; Site Selection and Investigation; Tailings Transportation; Drainage, Seepage and Groundwater; Decants, Water Management; Pollution Control and Environmental Aspects; Closure and Rehabilitation:Monitoring; Instrumentation; Vegetation; Reworking Existing Deposits; General.
?Luossavaara-Kiirunavaara AB (LKAB), an iron ore company with mines in northern Sweden is continuously considering new technologies for handling, transportation and disposal of waste rock and tailings. The mines and concentration facilities are located north of the Arctic Circle which in Scandinavia means an average temperature of about 0° C. Snow from mid-October to mid-May. In winter the temperature may reach -35 to -40° C during weeklong cold spells. At the Svappavaara mine early technical-economical feasibility considerations together with expected space limitations in the concentrator area favored location of two thickened tailings thickeners on a hill close to the disposal area about 1600 m away from the concentrating plant. In this way only short distance pumping of thickened slurry is required and warm process water is recovered directly by gravity from the thickener to the concentrating plant. A thickener of a high-density type with 18 m diameter was first installed. Four years later an additional thickener of paste type with diameter 24 m was put into operation. The design (maximum) capacities were 115 and 275 tph (tons per hour) for the 18 m and 24 m thickeners, respectively, with solids flux rates of 0.45 and 0.6 ton/m2h. Both are planned for common use for 390 tph within a few years. The tailings product is characterized by an average particle size of about 30 µm with a maximum of about 500 µm and about 40 % passing 20 µm. Solids density about 3000 kg/m3. A solids concentration by mass of 70 % was considered sufficient for deposition at a slope of up to 3 %. The objective is to present and discuss the performance of the thickening, transportation and deposition systems during the commission stages and first years of operation. The aim is also to describe how initial conditions related to changes in the tailings production rate together with climatic conditions called for robust by-pass arrangements. Furthermore, complicating factors related to the choice of auxiliary equipment and instrumentation for central functions are discussed.
Friction losses is a key parameter in the design of pipeline transportation in paste backfill. A full-scale pipeloop test was conducted in the JCHX Paste Backfilling laboratory to investigate the friction losses of cemented unclassified iron tailings slurry. Friction losses in upward sloping pipe, vertical downward pipe, vertical upward pipe, 90° long radius elbow, horizontal straight pipe and downward sloping pipe were tested simultaneously under different solid fractions. The results indicated that friction losses always increase with flow rate and solid fraction. Friction losses in the elbows are about 1.552.16 times that in the horizontal straight pipe, which is about 2.710.0 kPa·m-1. The pipe-loop test data can be used to analyse the rheological priorities of cemented unclassified tailings slurry. Based on the Buckingham rheological equation, an empirical formula for friction losses was established and applied to a pipe with the optimal diameter of DN 150 mm. It can be concluded that the full-scale pipe-loop test is an effective way to investigate friction losses and the economics of design pipeline transportation.
?It has been determined, after a technical feasibility study, that ultrasonic is the best alternative to characterize slurry flows in tailings flumes, by using the Ultrasonic Velocity Profile (UVP) technique, which among its many advantages it has shown not to be invasive, to have a high sample frequency, to have the ability to make measurements in opaque means, to have portability, and also that its implementation in existing structures is not complex, nor that it requires special permissions like other technologies do (based on radiation). In the Investigation Centre JRI (CI-JRI), two measurement UVPs prototypes have been designed, built and set up in transport systems of flumes on a laboratory scale. These prototypes have also been able to perform ultrasonic measurements that have got to a correct estimation of the velocity profile, together with an ad hoc post-processing methodology, outcomes that allow projecting applications at an industrial level and that would generate meaningful benefits in the operation. The future challenges aim to higher scale tests and the development of a given post-processing methodology that would let determine inline, and with a precision over 1%, associated values to the concentration of solids in the fluid, the velocity profile of the fluid in the flume and rheological parameters, all essential to a correct controlling of stages in the transportation of tailing slurries with high concentration.
?Tailings transport is an integrated element in any wet tailings storage facility (TSF). Tailings from the process plant are often thickened to a moderate or relatively high (but still pumpable) solids concentration, depending on several parameters mainly the TSF deposition requirements and strategies, process plant water security status and the dewatering technology utilised. This paper overviews the transportation of paste and thickened tailings and discusses various aspects and considerations in the hydraulic design of the system. Material characteristics, flow behaviour assessment (rheological behaviour measurement and interpretation) and the basis of design definition are discussed. The recent developments in environmental authorities regulations associated with the tailings pipeline burst and leakage management are also reviewed in this paper. The tailings leakage and spillage to the environment is one the main concerns for any tailings hydraulic transportation system, therefore as part of the tailings pipeline design, the pipeline integrity failure (due to pipe wear, overpressure bursting etc.) should be thoroughly analysed to propose proper mitigation measures. The paper discusses a methodology to assess the potential tailings volume release to the environment in an event of the pipeline integrity failure which would be of interest to the operators and designers.
?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.