For the alternative disposal method of dry disposal of tailings, two aspects of the process have to be evaluated, namely the maximum dryness of the separated solids and the maximum liquid recovery. For most mining operation, dry disposal is a new concept. Presenting these companies with examples of operations where this processing option has been successfully applied and proven, will help them to adapt to the changing requirements in the future. Focus has been placed on adapting decanter centrifuges to the mining environment. Modern decanters stand out in terms of their small footprint, low water demand, high availability and their high degree of automation, combined with the excellent cost / performance ratio. Decanter centrifuges have started to play a key role in applications such as tailing dewatering, drilling and tunneling muds processing, hydrometallurgical processes of gold, nickel or zinc and separating SX crud in copper refineries. This paper will present advantages of decanter centrifuges compared to the traditional technology and corroborate these advantages by case studies, especially from South America.
The diamond industry has been disposing of its coarse tailings using conveyor and stacker systems for many years. The process plant typically generates two tailings products, a grit fraction (sand) and a coarse fraction (gravel), which are often combined on one dump. In some cases, the dump is stable with a single steep slope angle. However, in other situations a composite slope forms with settlement and intermittent slumping behaviour, this impacts on both design and operation. The thermal coal industry has also been disposing of dry ash for many years using either conveyor/stacking systems or haul trucks. Both systems work well, but the costs, deposition plans and stability aspects differ. Management of water and dust are also key factors. There are a number of key design and operational aspects that are similar between these diamond tailings and ash facilities, and would apply equally to filtered and dry stacked tailings. This paper aims to examine these similarities and show how these learnings could be built into new filtered tailings designs and operations to make them more efficient and stable.
At present, most tailings are dewatered by static settling in tailings dams. The environmental impact of these large settlings ponds is very dramatic, not to mention the space requirements and the potential risk of dam failure. This method of disposal also results in the loss of process water due to evaporation. This can be significant in areas where the supply of fresh water is limited. The high centrifugal force in a decanter centrifuge drastically increases dewatering efficiency, as centrifugal separation happens at up to 29,430 m/s² (3,000 × gravitational acceleration or g). Depending on the material, more than 90% of the process water can be recovered using centrifuge technology. It can be reused in the mineral processing operation and will increase the water efficiency of the whole mining community. This paper presents the results of actual projects in Brazil and Peru.