Mineral Resources

Business Processes Operation phase

Mining

Open pit mining

After an economically optimal mining plan is drawn up for the target copper deposit, ores are mined. Open pit mining, by which ores are extracted from stepped walls near the earth surface, is the mainstream method for large-scale mines currently in operation.

Ore processing

Different methods are applied to process the extracted ores, depending on their type (copper sulfide ores or oxide ores).

Copper sulfide ores

Before processing

Copper sulfide ores

Copper grade around 1%

Processing method

Crushing and Grinding
Grinding Mill (semi-autogenous grinding mill)

Extracted ores (a few tens of centimeters in diameter) are crushed and then ground to a size of a few micrometers.

Flotation

Taking advantage of the hydrophobicity of sulfide ores to repel water, the target ores are separated into copper-rich portions and the remaining portions. The ground ore is mixed with water to form slurry which chemical reagents are added, and then aerated to produce bubbles. Using the principle that the hydrophobic ore particles attach to the bubbles, the target ores are recovered. From this process, copper concentrates with 20-40 %-Cu is produced, which is sent to a smelting and refining plant (our metal business).

After processing

Copper concentrates

Copper grade 20-40%

Oxide ores

Before processing

Oxide ores

Copper grade around 1%

Processing method

Leaching
Leaching pad (dumping site)

A feature of the copper in oxide ores is that it dissolves readily in a weak acid solution. Piled up ores at the leaching pad are directly added an acid solution via drip system, and then leach solution containing copper is collected with several months of leaching period.

SX-EW (Solvent Extraction-Electrowinning)
Electrorefining process

An organic solvent is added to the leach solution containing copper recovered in the leaching process, copper ions are selectively extracted, and then electrorefining is performed to obtain refined copper with a purity of 99.99%.

After processing

Refined copper

Purity 99.99%