The following is an overview of the tailings re-treatment process:
High pressure water pumped from the adjacent evaporation dam is used to convert the tailings into a slurry, which is channelled and pumped to the Century Processing Plant for processing, prior to being pumped to the existing open pit for final deposition.
Hydro Mining Ops Centre
Century Processing Plant & Supporting Infrastructure
The 7.0Mtpa capacity processing plant, in excellent condition after 16 years of use, was put on care and maintenance following cessation of processing operations. In January 2018, the plant was refurbished in order to re-process tailings. In August 2018, operations commenced to process an initial capacity of 8.0Mtpa tailings through one half of the plant with the aim of increase capacity to 12.5Mtpa in Phase II, with the option to add on additional infrastructure to increase to an ultimate throughput rate of 15.0Mtpa.
Key Equipment Includes:
- Primary crushing facilities, which reduce ROM feed to approximately 100mm;
- Grinding facilities consisting of one SAG mill (12MW gearless drive) and two balls mills (8MW gearless drive & 6.7MW single pinion drive);
- Milling facilities consisting of fifteen ultrafine sand mills (355kW);
- A conventional froth flotation circuit, comprising 21 stirred mills and 79 flotation cells;
- Remnant mobile fleet (reduced from original full scale operations) including 6 × Komatsu 630E dump trucks, 5 × Caterpillar D10/D11 dozers and 4 × Komatsu PC excavators;
- Five exploration and grade control drilling rigs;
- Full site laboratory capable of handling all exploration and plant samples; and
- Equipment workshops and stores for all mobile and fixed plant maintenance.
Century Processing Infrastructure
The 304km buried slurry pipeline was commissioned in November 1999 and is a unique and leading edge design for a pipeline in Australia. Providing unmatched access to the coast for the region, the pipeline is buried over most of its length to a depth of approximately 1m.
The host steel pipe is high tensile 12 inch pipe, lined with high density polyethylene pipe. The liner was included to eliminate wear/corrosion of the host pipe.
Since re-commencement of operations, zinc concentrate has been pumped from concentrate storage tanks at the Lawn Hill site to the Karumba Port. Slurry batch transit time for the 304km journey is ~72 hours and the overall elevation difference is -155m from the site to the port. The pipeline is capable of transporting zinc concentrate at a maximum rate of 155t/h at 37% solids and lead concentrate at a maximum rate of 161t/h at 37% solids.
Century Mine underground slurry pipeline infrastructure
Karumba Port Facility
Built as part of mine development in the late 1990s, Century’s Karumba Port Facility includes dewatering and drying circuits, maintenance workshop, a concentrate storage shed and administration buildings.
During former operations the Karumba Port Facility received 3,000t of slurry each day into one of four balance tanks. The slurry was dewatered by five pressure filters, with concentrate then passed through a rotary dryer to remove excess water before being stockpiled in the concentrate storage shed in preparation for shipping.
In late 2012, a three-year A$32M project to refurbish the concentrate storage shed and other facilities was also completed, ensuring the port area remains in operational condition.
With operations re-commenced, at nameplate capacity, 1,500t of slurry each day will be sent to the Port for processing.
Equipment at Karumba includes:
- Dewatering/filter/drying plant and fully mechanised concentrate storage shed;
- Jetty and bulk ship loading facilities; and
- Administration buildings & workshops.
Electricity consumed at Karumba was supplied by the on-site diesel power station with a nameplate capacity of 5.8MW.
Karumba Port Facility
M.V. Wunma Transhipment Vessel
Century’s transfer vessel, the M.V. Wunma, is custom-built for the shallow waters of the Norman River channel and is used to transfer concentrate to export ships anchored in the Gulf of Carpentaria.
It takes approximately 12 hours for the vessel to load, transport and discharge concentrates and return to the Karumba Port. The vessel operates day and night, depending on tides and weather conditions.
M.V. Wunma Transhipment Vessel
All mine site accommodation is at the Darimah village, located approximately 3km from the mine, which has a capacity of 400 people per night.
Accommodation comprises mostly en-suite rooms in accommodation blocks (four rooms each). Facilities include a wet and dry mess, a gymnasium, pool, football and rugby ovals and various other sport facilities. The accommodation precinct also includes a sewage treatment plant, water treatment plant and communication towers.
Century Mine Accommodation Camp
Mine Site Airport
The mine is serviced by a private airport located on the mining lease. The airport has a sealed runway equipped for night landings, and has an office building and semi-enclosed passenger waiting area.
Medium sized jet aircraft (Fokker F100) transport staff and contractors to and from Cairns.
Karumba Property Ownership & Pelicans Inn Lease
New Century also owns a portfolio of thirteen houses in Karumba. The houses are either used to accommodate employees or as rental properties. A lease over the Pelicans Inn in Karumba is also in place and is used for staff and contractors operating the Port facility.