Thickening of tailings using hydrocyclones operating under vacuum conditions

摘要

Many tailings storage facilities (TSFs) on the African continent are constructed by utilising the proven cyclone deposition method. The plant tailings is separated to deliver a coarse sandy underflow to the wall zone of the TSF and the overflow is discharged into the basin. The average percentage of dry gold tailings solids that is available for the wall zone is generally between 20 and 35%. The product is stable and high rates of rise (RoR) can be achieved. The TSF impoundment wall is normally constructed to one vertical and three horizontal (approximately 18°).A vacuum cyclone system has been developed for a mineral sands operation located close to the sea shore on the South African west coast, to flatten the side slopes to one vertical and five horizontal. The reason for the flat slopes is for rehabilitation of the TSF in this very arid part of the country, which is distressed by high velocity northwesterly and southeasterly winds. The tailings density of the TSF averages 1.17 t/m~3 and the conventional approach to cycloning is not feasible. With the vacuum system an average underflow of 1.9t/m3 is achieved with the overflow density averaging 1.01 t/m~3. The solids recovery achieved for wall flattening is approximately 88.5%.A gold mine in West Africa is utilising this technology in placing approximately 40-50% of the solids pumped to their TSF on the outer wall in the downstream fashion, delaying the need for a new greenfields facility. The existing TSF will have adequate capacity to accommodate the slimes from the plant for Life of Mine (LoM), thus minimising the risk of overloading the facility.This paper describes the process of utilising hydrocyclones operated under vacuum conditions to:? flatten wall slopes for rehabilitation? increase the capacity of a TSF by placing solids downstream of an existing wall? buttress a TSF wall, increasing the overall stability.