Dewatering technology in cycloned tailings for water recovery and immediate compaction of sands in tailings wall construction *H. Gorvenia1, E. Ku1 1Metso Peru (*Presenting author: hilario.gorvenia@metso.com) ABSTRACT The use of sands classified by hydrocyclones is a widely used and effective technique in tailings dam construction. However, it faces significant challenges related to the presence of ultrafines (especially clays) and the high-water consumption required for hydraulic transport. During the classification process, the tailings are separated into fine and coarse fractions. The hydrocyclones underflow, which contains the sand used as structural material, can still retain a significant proportion of ultrafines, negatively impacting its drainage and compaction capacity for the structural portion of the tailings dam. To mitigate these effects, treating the underflow in a dewatering screen allows for the efficient removal of these residual ultrafines. This substantially improves the sand's permeability, facilitates its dry handling via conveyor belts, and significantly reduces the initial saturation of the material. The presence of clays in the construction material is critical, as they decrease permeability, hinder drainage, and reduce compaction capacity, compromising the dam's structural stability. It is essential to use sand with low saturation and good mechanical properties, as well as actively monitoring piezometric levels to maintain adequate safety conditions in the tailing’s storage facility. From an economic point of view, the traditional hydraulic transport process requires large volumes of water, an increasingly scarce and expensive resource. The incorporation of dewatering screens not only improves material quality but also allows for significant water recovery, reduces operational risks, and optimizes the costs associated with tailings construction. The proposed solution focuses on maximizing water recovery and immediately improving the compaction of cycloned sands through the controlled removal of ultrafines in the underflow. By reducing the fine fraction (especially <75 µm and <20 µm), the permeability of the sand material is increased, drainage is accelerated, and a more stable and operable wall condition is promoted, decreasing risks associated with saturation and improving the efficiency of the water management system. Dewatering technology (dewatering screen) also allows for short-term water recovery and delivers a product with improved geotechnical performance, enabling more robust operation of the TSF (Tailing Storage Facility) and greater resilience to feed variability and precipitation events. The results of this application of a dewatering screen showed significant improvements, recovering up to 86% of the water from the material, eliminating 66% of the material smaller than
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