Copper Ore Extraction Processes: Efficient Transformation from Mines to Concentrates

Copper ore is an important mineral resource, primarily composed of copper sulfides or oxides mixed with other minerals. When reacting with sulfuric acid, it forms blue-green copper sulfate. Industrial copper minerals include native copper, chalcopyrite, bornite, and malachite, among others. Based on the copper oxidation rate, copper ores are categorized into sulfide ores (with less than 10% oxidized copper), oxide ores (with more than 30% oxidized copper), and mixed ores (with 10%-30% oxidized copper). The main extraction process for copper ores is flotation, while hydrometallurgical processes are commonly used for difficult-to-select mixed copper ores and oxide ores.

Copper Ore Extraction and Processing

1. Copper Flotation Process

Flotation is a commonly used process in copper ore beneficiation, suitable for the separation of copper sulfides and oxides. The main process flow is as follows:

1. Crushing and Screening: The ore is first fed into a primary jaw crusher via a feeder, then sent to a secondary jaw crusher for further crushing.

2. Stage Grinding: The crushed ore enters a ball mill for grinding, followed by classification in a spiral classifier. Coarse particles separated by the classifier are returned to the ball mill for re-grinding.

3. Mixing and Flotation: Fine particles from the spiral classifier are mixed thoroughly in a mixing tank before being sent to the flotation machine for flotation.

4. Thicken and Dewater: The flotation concentrate, once reaching a certain concentration and grade, is sent to a filter for dewatering to produce copper concentrate.

The flotation process for copper oxide ores and sulfide ores is essentially the same, although oxide ores can also be processed using leaching methods.

2. Copper Leaching Processes

Common leaching methods for copper oxide ores include heap leaching, vat leaching, in-situ leaching, and agitated leaching.

Heap Leaching Process

Heap leaching is suitable for ores that do not require extremely fine particle sizes. The mined ore is crushed to a certain size and directly placed on a leaching pad. Strong acid solutions are sprayed to permeate the crushed ore. Over time, copper is leached from the broken ore into the solution as a pregnant leach solution, which is then pumped into a solvent extraction unit for further purification.

Vat Leaching Process

Vat leaching was a commonly used leaching method in early hydrometallurgical copper production. It uses concentrated sulfuric acid to leach copper oxide ores with 1-2% copper content (particle size <1cm). The resulting leachate, with a higher copper concentration, can be directly used for copper electrowinning.

In-Situ Leaching Process

In in-situ leaching, wells are typically spaced at 30x30cm (or 15x7.5m), with drilling diameters of 15-25cm. Plastic pipes are installed in the holes to penetrate the ore body, through which leaching agents flow into the ore. The leachate is pumped back to the surface from the bottom of the ore body. This process is suitable for residual or unmined oxide copper ores and low-grade copper ores in old mines. For abandoned mines or copper ores that are not economically viable using other extraction methods, in-situ leaching holds more potential.

Agitated Leaching Process

Agitated leaching is conducted in leaching tanks equipped with agitation devices, using high-concentration sulfuric acid to leach fine-grained (-75um particles accounting for 90%) copper oxide ores or calcined sulfide ores. Leaching methods include air agitation and mechanical agitation. Due to the small particle size and thorough agitation, agitated leaching is faster and has a higher recovery rate than vat leaching. It is suitable for processing high-grade ores or low-grade tailings with copper content less than 1%.

Environmental and Economic Considerations

The choice of copper ore extraction process depends not only on the nature of the ore but also on environmental and economic factors. Flotation is widely used for its efficiency and flexibility, while leaching processes offer advantages in environmental friendliness and cost-effectiveness, especially for low-grade ores.

Conclusion

Copper ore extraction processes are diverse, with flotation and leaching being the two main methods. Flotation is suitable for processing copper sulfide and oxide ores, while leaching processes excel in handling low-grade and difficult-to-select ores. The selection of an appropriate extraction process requires a comprehensive consideration of ore characteristics, environmental requirements, and economic benefits. With continuous technological advancements, copper ore extraction processes will become more efficient and environmentally friendly, supporting the sustainable development of the copper industry.