For this project P&C completed test work, basic and detailed engineering for a 940 t/h phosphate tailings dewatering facility and slurry pumping system. The dewatering section included cyclone classification with high-rate thickening of the slimes and vacuum filtration of the coarse tailings. The high pressure thickened slimes pumping system included piston diaphragm positive displacement pumps and a HDPE lined steel pipeline to transport the slimes to the tailings storage facility.

P &C designed and commissioned a dewatering preparation plant for Mineco’s Olovo mine that produces filtered tailings at less than 14% moisture content. Engineering studies identified a dry stack facility as the most appropriate solution considering the local topography, material properties and environmental requirements.

P &C provided detailed design and assistance for the commissioning and start-up of an 82 t/h tailings filter plant. The filter plant processes either the full tailings tonnage from the thickener underflow, or partial tonnage when the paste backfill plant is operational. The filter cake is discharged onto an overland conveyor for transport to a nearby mined-out pit.

P &C redesigned the 105,000 t/d thickened tailings deposition system to improve tailings beach slope for this project. The project involved equalising spigot flows while minimising spigot discharge energy over large deposition areas.

This project required P&C to carry out the design, engineering, and commissioning of five 15 m diameter paste thickeners and a positive displacement pumping system for a 12,000 t/d kimberlite fine tailings circuit. Paste tailings are transported 5.5 km with a maximum pump discharge pressure of 12 MPa.

The feasibility study for a 9,600 t/d filtered tailings system for a gold mine in Quebec was carried out by P&C. Extensive testing was done to ensure the optimum system was developed, and technical evaluations of commercial thickeners and filters was completed. This fast-track construction project required working closely with the Owners’ team and EPCM company during detailed engineering and procurement.

P &C conducted a pre-feasibility level study of a 15,000 t/d system for the La Coipa operation in Chile. The complete flowsheet was analysed including comminution, recovery, and tailings dewatering. The thickening and filtration test work on the tailings of two new ore bodies, one of high clay content, included clay behavioural analysis to determine the optimal water chemistry for the dewatering of the clay rich tailings. The study scope required the utilisation of the existing thickening and filtration equipment. Geotechnical and convey test work was performed to determine the optimum filter cake moisture for the transport and deposition of the material.

P &C performed dewatering and materials handling test work, process design, and test protocol development for an 8,000 t/d pilot demonstration filter plant. The facility will investigate the performance of a large pressure filter and ancillary equipment.

P &C provided subject matter expertise in process engineering consultation for the development of asset-specific tailings strategy roadmaps. This engagement included a technology landscape review of current and emerging dewatering technologies, coordination of partnership exploration workshops with original equipment manufacturers, participation in client opportunity framing workshops and delivery of medium to long-term tailings strategy roadmaps.

Background:
To treat high-grade ore Yanacocha implemented a milling process at the La Quinua operation. However, limited sites were available for the tailings storage facility. To best utilise the available area the tailings storage facility is fully contained within an active heap leach pad. Consequently, high-concentration thickened tailings are required to reduce the amount of water placed in the facility. The tailings are thickened at the mill in a high-rate thickener before being pumped to the storage facility by a train of centrifugal slurry pumps.
The design considered the following key issues:

• The optimum design concentration to increase the tailings concentration, while maintaining reasonable capital costs for the system
• Pipeline material selection to achieve the required pipeline life
• The risk of particle settling in laminar flow
• Pipeline emergency flushing and shutdown measures.

Services:
P&C provided laboratory test work, trade-off studies, detailed engineering, and start-up commissioning assistance and has since completed the design of the phase II pipeline expansion project.