Taca Taca Project — NI 43-101 Technical Report

This article outlines the proposed processing route for the Taca Taca copper-molybdenum project, based on the NI 43-101 technical report, covering comminution, flotation, and concentrate handling.

Report context

The Taca Taca Project, as described in the NI 43-101 Technical Report, involves a conventional porphyry copper-molybdenum concentrator design. The report presents a processing flowsheet intended for an ultimate throughput of 60 Mtpa, with a phased approach to accommodate an initial 40 Mtpa. The processing strategy is designed to treat both supergene (plus mixed) and hypogene (sulphide) primary ores, where primary ores contain more than 50% of copper as chalcopyrite. The report also addresses site-specific considerations for plant location due to prevailing winds and the use of saline water in flotation circuits.

Processing route

Ore feed and flotation approach

The processing feed at Taca Taca is proposed to be a blend of supergene (plus mixed) and hypogene (sulphide) primary ores. Primary ores are defined as containing more than 50% of the copper present as chalcopyrite, meaning significant amounts of secondary sulphides and tarnished minerals could be present. The preferred process route follows conventional porphyry copper-molybdenum concentrators common in South America, but includes a sulphidising flotation circuit using sodium hydrosulphide (NaHS) for oxidised and tarnished minerals. When treating primary ores with low acid soluble copper, the same circuit will be used, but NaHS addition would be switched off.

A gold recovery circuit is not proposed for the auriferous oxide cap during the pre-strip phase of mine development. This material would be stockpiled separately and subjected to future testwork to determine processing options. Flowsheet design and equipment selection are based on experience at recent concentrator installations in Zambia (Sentinel at 55 Mtpa) and Panamá (Cobre Panamá at 100 Mtpa). Rougher flotation can be operated in brine, but testwork indicates that acceptable recoveries and concentrate grades in the cleaner circuit require good quality water.

Plant location

The processing plant site is shielded from prevailing winds from the north west, which can reach speeds up to 23.2 m/s (83.5 km/h). From the east, the plant would be partially shielded by topography and the waste dump on the salar. Milling and flotation areas would be shielded with sheeting on two sides and roofs, or wind barriers on the north and west sides. Wind barriers are also required on thickeners to reduce wave action. The crushed ore stockpile would be covered, and conveyors would have removable covers and dust suppression sprays. Administration offices and other infrastructure are proposed upwind of the pit and plant area.

Comminution circuit

The processing plant would be designed for an annual throughput up to 180,000 tpd (60 Mtpa). The comminution circuit would be a conventional SABC (SAG, ball, crusher) configuration, with secondary crushing of SAG mill feed required to increase throughput from 40 to 60 Mtpa. The grinding circuit would consist of two trains, each of 30 Mtpa capacity, designed to treat 3,750 tph from a feed size of 80% passing 130 mm to a product size of 80% passing about 180 µm.

Each train would comprise a 28 MW SAG mill and two 22 MW ball mills. Key comminution criteria include a crusher work index of 8.0 kWh/t, a JK parameter A*b of 44.9, a rod mill work index of 14.0 kWh/t, a Bond ball mill work index of 15.6 kWh/t, and an abrasion index of 0.18 g. A gravity recovery circuit would be installed on ball mill cyclone underflow for coarse gold recovery, and pebble crushing would handle scats from the SAG mills using two MP 1250 crushers.

Flotation circuit

Rougher and scavenger flotation would treat cyclone overflow slurry with controlled sulphidisation flotation using NaHS for oxidised and tarnished supergene ores. For 60 Mtpa, two parallel circuits would be installed, each with a single train of seven 600 m³ flotation cells, providing approximately 25 minutes residence time. For the initial 40 Mtpa, one circuit with nine cells would provide sufficient residence time. Rougher concentrates would be thickened prior to regrind and diluted with fresh water for cleaning to produce a bulk Cu-Mo concentrate. Copper-molybdenum separation would be achieved in a molybdenum flotation circuit with five to seven stages of cleaning.

Concentrate handling

Flotation concentrates would be dewatered prior to off-site processing. Copper concentrates would be thickened and filtered, then shipped in bulk by rail to a coastal port in Chile. Molybdenum concentrates would be filtered, dried, and bagged for transport. Thickening of rougher flotation tails would occur in three 50 m diameter thickeners, with thickened underflow pumped to a tailings storage facility (TSF) and decant water reclaimed for process use, though climatic conditions may limit decant return.

Key reported parameters

Technical qualifications

The design criteria and grades/recoveries represent average figures for mine life; year-on-year recoveries and grades will vary. The report notes that options for staging plant construction from 40 to 60 Mtpa have not been evaluated in detail. The gold oxide cap material is not included in the processing circuit and requires further testwork. Climatic conditions, including very dry, constant winds and high solar radiation, may limit the amount of decant water returned from the TSF. The process design is based on testwork data for grindability and flotation, with acceptable cleaner performance dependent on good quality water.

Source: Taca Taca Project , NI 43-101 Technical Report, Item 17 Recovery Methods.