This technical report describes the proposed Watut process plant as a compact copper concentrator with phased expansion to accommodate mine ramp-up and changing ore composition.
Report context
The Wafi–Golpu Project is located in the Morobe Province of Papua New Guinea. This NI 43-101 Technical Report for the project is dated 2018. The processing section presents the proposed recovery methods for the Watut process plant, describing a concentrator designed to be built progressively in line with the mine ramp-up profile.
Processing route
Proposed plant configuration and throughput
The proposed Watut process plant will treat 8.42 Mt/a of ore for the first three years of operation. In the fourth year of operation, an additional ball mill and flotation cells will be installed to support throughput ramp-up to 16.84 Mt/a. The plant will run intermittently (campaign treatment) and in 50% turndown mode for the first three years. During the mine ramp-up period, the total volume of the coarse ore stockpile and start-up stockpile will be used to maintain plant utilisation as high as practicable, minimising the number of plant stops. The plant is designed to cater for ore composition changes over the life of mine (LOM), and blending is not expected to be required.
Crushing and grinding
The process plant will include a crushed ore stockpile and reclaim, and a single semi-autogenous grind (SAG) and SAG/ball (SAB) milling circuit. The ball mill will operate in closed circuit with cyclones at the lower design throughput of 8.42 Mt/a. This will be expanded to include a second ball mill, operating in parallel with the original ball mill circuit when the plant is expanded to a design capacity of 16.84 Mt/a. The target grind size is 80% passing 106 μm.
A pebble crusher circuit will be included. Pebbles will be recirculated to the SAG mill during the 8.42 Mt/a LEAN flowsheet and early years of the 16.84 Mt/a Golpu flowsheet, with the pebble crusher included due to the expected increased ore hardness in the later years of mine life.
Copper flotation
Copper flotation will comprise rougher flotation, a copper rougher cleaner (single Jameson cell) that processes the first rougher concentrate, copper concentrate regrind followed by a three-stage copper cleaner, and a cleaner–scavenger stage.
Additional copper flotation cells forming part of the LEAN circuit will be commissioned approximately nine years post the Special Mining Lease grant to accommodate the ramping of the process plant to design capacity of 16.84 Mt/a.
Pyrite flotation and regrind
Installation of a pyrite flotation and regrind circuit will facilitate the processing of ore containing a higher metasediment content from year five onwards. A pyrite rougher flotation circuit, which further processes the copper rougher tailings, will be introduced 10 years post the Special Mining Lease grant to meet the requirements of the increased metasediment content of the ore, corresponding to a porphyry content of less than 75%. A pyrite concentrate regrind circuit followed by cleaner and cleaner–scavenger stages will be included.
Concentrate and tailings handling
The process plant will include concentrate dewatering and handling, tailings thickening, pumping and water recovery.
Ancillary systems
The plant will include reagent mixing and distribution (including lime slaking, flotation reagents, and flocculants), grinding media storage and addition, water services (including raw water, fire water, potable water, and process water), and air services (including high-pressure air and low-pressure process air).
Ore composition
The weighted average ore composition for the first four years of production is projected to be 84.3% porphyry, while from approximately the fifth year this reduces, corresponding to increased metasediment content in the ore.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Initial design throughput | 8.42 Mt/a | Proposed design (first three years) |
| Expanded design throughput | 16.84 Mt/a | Proposed design (from year four) |
| Target grind size | 80% passing 106 μm | Proposed design |
| Initial milling circuit | Single SAG and SAB, ball mill in closed circuit with cyclones | Proposed design |
| Expanded milling circuit | Second ball mill in parallel with original ball mill circuit | Proposed design |
| Pebble crusher | Recirculates pebbles to SAG mill | Proposed design (LEAN and early Golpu flowsheets) |
| Copper rougher cleaner | Single Jameson cell | Proposed design |
| Copper cleaner stages | Three-stage after regrind | Proposed design |
| Pyrite circuit introduction | Year five onwards | Proposed design (higher metasediment content) |
| Pyrite rougher flotation timing | 10 years post Special Mining Lease grant | Proposed design (porphyry content less than 75%) |
| Weighted average ore composition (first four years) | 84.3% porphyry | Projection |
Project website: https://www.wafigolpujv.com/
Technical qualifications
This processing description is based solely on the proposed design as presented in the 2018 technical report. No historical operating data or testwork results were provided in the original processing sections. The plant description relates to a proposed design that will be progressively built in line with the mine ramp-up profile, with specific circuit additions timed relative to the Special Mining Lease grant.
Source: Wafi–Golpu Project, Morobe Province, Papua New Guinea, NI 43-101 Technical Report, 2018, Section 1.15 Recovery Methods.
