Description of Operations
Surveying the mine.
A description of the process from mine to smelter.
(see also Diagram of operations)
From mine to mill
The Ok Tedi mine is an open-cut operation in which about 78,000 tonnes of ore and 80,000 tonnes of overburden (waste rock) are mined each day from a pit covering about 2.6 square kilometres. The mine and mill operate 24 hours per day, 365 days per year. The mine's equipment fleet includes:
- 23 Caterpillar 789 haul trucks (170 tonne capacity)
- 3 Caterpillar 777D haul trucks (100 tonne capacity)
- 3 RH 200 O&K hydraulic shovels
- 3 Hitachi hydraulic excavators
- 3 Atlas Copco Pit Viper drill rigs and 1 Tamrock drill rig
- 10 Caterpillar D11 dozers
- 2 Caterpillar 992 loaders
- 3 Caterpillar 16H graders
- 2 Caterpillar 834B rubber-tyred dozers.
The Mine Plan is used to formally document and control the overall mining operations. The planning involves detailed processes to ensure optimal ore recovery, as the Mt Fubilan ore body is very complex.
Rock is drilled, blasted and excavated along 15 metre-high "benches" around the pit. The blasted material is excavated and loaded onto haul trucks using large shovels. Waste rock is transported to one of two waste rock dumps and released.
Ore is transported to large gyratory crushers that reduce it to a size of less than 200 millimetres. This crushed ore is conveyed to a primary stockpile at the mill.
The mill
The purpose of the mill is to extract copper and gold from the ore. Crushed ore is fed from the stockpiles into the mill's grinding circuit, which consists of semi-autogenous grinding (SAG) mills and ball mills.
Ore is ground to sand so that 80 per cent of the particles are less than 180 microns in size. Following grinding, the ore enters flotation cells. Collector and frother reagents are added before flotation. The collector reagent coats copper and gold minerals to make them attach to air bubbles. The frother causes strong bubbles to form, which float to the surface, collecting the minerals as they ascend.
The froth is collected as a mineral concentrate. Several stages of flotation are used to increase the 
concentration of the froth.
The mill treats about 78,000 tonnes of ore each day, with an average grade of 0.8 to 0.85 per cent copper and 0.85 to 0.90 grams of gold per tonne. The product from the mill is a concentrate of 28-31 per cent copper and about 20 grams of gold per tonne.
A gold concentrate is also collected from a gravity circuit in the mill. In 2007, 218 dry metric tonnes of gold concentrate, containing an average of 0.83% gold was produced through this process.
The concentrate is thickened and transported as a slurry along a 157-kilometre, 150 mm diameter pipeline to the river port of Kiunga. This pipeline follows the main road linking Kiunga with the mine. It can carry 2,400 tonnes of concentrate per day at maximum capacity.
Loading and shipping
At Kiunga, the concentrate is filtered, dried and stockpiled awaiting transport. Dried concentrate is loaded onto barges and transported more than 800 kilometres down the Fly River to a silo vessel anchored at the entrance to the Fly River delta or at Port Moresby, depending on weather conditions.
The barges are purpose-built for the shallow conditions of the Fly River. The largest vessel has a capacity of 6,200 tonnes. Concentrate barges carry freight to Kiunga on their return trip.
The moored silo vessel, the 64,000 deadweight tonne MV Erawan, stores concentrate until it is loaded onto export ships that carry it to smelters around the world.
Markets
Ok Tedi's copper concentrate and gravity gold is shipped to its customers in Asia and Europe. It has contracts with copper producers in Japan, the Philippines, Germany and Korea.
In 2007, OTML exported 668,475 dry metric tonnes of copper concentrate. This contained 186,525 tonnes of copper, 16,281 kilograms of gold, and 50,169 kilograms of silver.
Power supply
Power for the mine, mill and township of Tabubil is supplied by hydroelectric and diesel generators installed at Ok Menga, south-east of Tabubil, specifically for the project.
The Ok Menga hydroelectric run-of-river scheme supplies about 75 per cent of the project's energy requirements. Maximum power output from Ok Menga is 57 megawatts. A 45 megawatt diesel power station and 2 diesel-fired gas turbine generator with a combined capacity of 16 megawatt at Tabubil, and a 2 megawatt hydroelectric power station at Yuk Creek, meet any additional power requirements.