The PSJ Cobre Mendocino Project updated its technical design during the pre-construction stage and submitted a series of optimizations related to ore processing, water recovery and tailings disposal to the relevant authority. According to the company, the modifications have already been evaluated and approved.
By Panorama Minero
The main addition is a high-capacity tailings filtration system that will allow ore processing to increase from 28,000 to 42,000 tonnes per day. The increase, equivalent to 50%, will be achieved while maintaining the approved fresh water flow rate of 141 liters per second and within the footprint and general layout of the facilities already assessed.
The update comes as PSJ completes technical studies, incorporates new geological information and defines the final engineering prior to the start of construction. As part of this process, the geological models, mine planning and operating conditions of the tailings storage facility were also reviewed.
A New Production Outlook
Under the updated design, PSJ projects annual production of approximately 75,000 tonnes of copper, 80,000 ounces of gold and 900,000 ounces of silver.
The company maintains that the increase in processing capacity will enhance the economic potential of the deposit and the associated benefits for Mendoza through increased economic activity, exports, royalties, taxes and fiscal contributions.
A Filtration System to Recover More Water
Following the flotation stage, the tailings will undergo a thickening process that will increase the solids concentration to approximately 60%. The slurry will then enter high-capacity filter presses that will remove an additional proportion of water and transform the material into a compact filter cake containing approximately 85% solids.
The filtered material will be transported and disposed of through dry stacking, an alternative that reduces the amount of water in the storage facility and eliminates the need for large conventional ponds or settling basins.
Water recovered during filtration will be returned to the plant’s internal circuit. According to the company, this recirculation will reduce losses and support greater processing capacity while maintaining the same approved fresh water flow rate.
The filtered tailings storage facility was designed by Knight Piésold, an international consulting firm specializing in tailings storage facility engineering, geotechnical stability, operational monitoring and mine facility closure. The higher density and compaction of the material will allow disposal to remain within the approved footprint.
The incorporation of this technology will require greater investment and will also increase operating costs due to the need to install additional equipment, specific filtration infrastructure and systems for the mechanical handling of materials. PSJ stated that the improvement is aimed at optimizing resource use and strengthening operational safety prior to the start of construction.
Increased Processing Based on the Geological Update
The increase in capacity is also related to information obtained through new in-fill drilling campaigns. This work makes it possible to update the deposit’s geological model and more precisely define the distribution of ore within the mine plan.
Based on this information and current conditions in the international copper market, PSJ updated the cut-off grade. This parameter establishes the minimum grade at which material can be considered economically viable.
Lowering this threshold will allow part of the lower-grade ore that, under the previous design, was planned to be sent to the low-grade waste dump to instead be incorporated into the flotation circuit. The decision is subject to the results of the geological, metallurgical, economic and operational studies supporting the updated mine plan.
The increased processing will not involve extracting ore from a new area or expanding the project’s physical or environmental footprint. The optimization is intended to make more efficient use of ore already identified within the mine plan while maintaining the general layout of the facilities and the assessed and approved footprint.
Progressive Closure of the Tailings Storage Facility
Filtration will also modify the management and closure conditions of the storage facility. Reducing the water content of the disposed material will improve stability conditions, operational control and progressive closure planning.
Under this approach, areas that reach their final configuration may receive soil covers and undergo revegetation during the mine life, in accordance with the detailed engineering specifications. Management of the storage facility would therefore not be concentrated exclusively at the end of operations, but could proceed gradually throughout the project’s estimated 16-year mine life.
