Standard mining centrifugal slurry pumps are used for pumping paste-like thickened tailings over short distances and for circulating the slurry in the thickener. Positive displacement coarse tailing slurry pumps are used in high-pressure applications where standard mining centrifugal slurry pumps can also be used to feed the high-pressure pumps. An overall comparison indicated that centrifugal pumps in series for 300 t/h and 4 MPa over a distance of 1,000 m would compete well with a positive displacement pump system.
With a tailings system of coarse tailing slurry pumps that includes a thickener that produces a highly concentrated underflow, the thickener can be placed at the concentrator or near the disposal area. It may be favourable to locate the thickener close to the disposal area when deposition takes place along a steep hill side or down a valley, where discharge from an artificial ramp or tower is not required, see Figure 1.
Figure 1 Schematic description of a thickened tailings system with the thickener located on hill close to the disposal area
In addition to site-specific conditions, the location of the thickener is mainly a balance of the cost of high pressure pumping and the disadvantage of having the thickening facility remote from the rest of the processing taking place in the concentrator.
Paterson presented a cost comparison between pumping 450 t/h of dry tailings as a dilute thickener feed at 14w% to a remote thickener located at the disposal area. The result indicated that the remote thickener location for a distance of less than 2.5 km may be cost effective compared to a location at the process plant which uses a high-pressure positive displacement pump transporting thickened tailings. The study considered pump and pipeline system capital and operating cost excluding costs associated with preparation and deposition as well as extra costs for operating a remotely located thickener and circulation of water back to the concentrator.