How to Process Copper Ore？

All available copper-bearing natural mineral aggregates are called copper mines. The high-grade copper concentrate can be obtained by the coarse grinding, roughing, and scavenging of copper ore, then grinding and concentrating of coarse concentrate.

1. Classification of copper ore

Due to the different types of ore, the nature of the ore is also different, so the beneficiation process needs to be customized.

The specific process for selecting copper ore depends mainly on the material composition, structure, and copper occurrence state of the original copper ore.

Generally speaking, copper ore can be divided into three categories: copper sulfide ore, copper oxide ore, and natural copper.

2. Copper ore beneficiation methods

Before the beneficiation of copper ores, crushing and grinding are required. The bulk ores are crushed to about 12 cm by a jaw crusher or a cone crusher. Then the crushed materials are sent to the grinding equipment, and the final particle size of the copper ore is reduced to 0.15-0.2 mm.

2.1 Beneficiation methods of copper sulfide ore

Copper sulfide can be divided into single copper ore, copper sulfur ore, copper-molybdenum deposit, copper-nickel, carrollite, and so on. Only flotation can be considered in its separation.

Almost all copper sulfide ores contain iron-bearing sulfides, so in a sense, the flotation of copper sulfide is essentially the separation of copper sulfide from iron sulfide. The common iron sulfide minerals in copper ore are pyrite and pyrrhotite.

The main factors affecting the flotation of copper-bearing pyrite:

• a. Disseminated grain size and symbiotic relationship of copper and iron sulfide. Generally, pyrite has a coarse grain size, while copper ore, especially secondary copper sulfide, is closely associated with pyrite. Only when the copper ore is finely ground can it be dissociated from pyrite. This characteristic can be used to select copper-sulfur mixed concentrates, discard the tailings, and then grind and separate the mixed concentrate.
• b. The influence of secondary copper sulfide minerals. When the secondary copper sulfide mineral content is high, the copper ions in the slurry will increase, which will activate the pyrite and increase the difficulty of Cu-S separation.
• c. The influence of pyrrhotite. The high content of pyrrhotite will affect the flotation of copper sulfide. Pyrrhotite oxidation will consume the consumption of oxygen in the pulp. In severe cases, the copper minerals do not float at the beginning of flotation. This can be improved by increasing inflation.

There are three common flotation processes:

A. Preferential flotation

Generally, copper is floated first and then sulfur. The content of pyrite in dense massive copper-bearing pyrite is quite high and high alkalinity (free CaO content> 600～800g/m3) and a high dosage of xanthine are often used to suppress the pyrite. There is mainly pyrite in its tailings with few gangues, so the tailings are sulfur concentrates.

For the disseminated copper-sulfur ore, the preferential flotation process is adopted, and the sulfur in the tailings must be re-floated. To reduce the consumption of sulfuric acid during the floatation and ensure safe operation, the process condition of low alkalinity should be adopted as far as possible.

B. Bulk-separating flotation

It is more advantageous for copper sulfur ore to contain less sulfur with copper easy to be floated. Carry out the bulk flotation firstly in the weakly alkaline pulp and then add lime to the mixed concentrate to separate the copper and sulfur in the highly alkaline pulp.

C. Semi-preferential bulk-separation flotation

In semi-preferential bulk-separation flotation, Z-200, OSN-43, or ester-105 with good selectivity are used as collectors to float copper minerals firstly. The copper concentrate is then subjected to copper-sulfur bulk flotation and the obtained copper-sulfur mixed concentrate is subjected to separation flotation of floating copper and suppressing sulfur.

It avoids the inhibition of the easily floating copper under high lime consumption and does not require a large amount of sulfuric acid-activated pyrite. It has the characteristics of reasonable structure, stable operation, a good index, and early recovery of target minerals.

The floatability of copper sulfide minerals :

• a. All minerals that do not contain iron, such as chalcopyrite and covellite, have similar floatability and the inhibitory effect of cyanide and lime on them is weak.
• All iron-bearing copper minerals, such as chalcopyrite and porphyry, are easily inhibited by cyanide and lime in alkaline media.
• b. The xanthate collector mainly plays the role of chemisorption together with the cation Cu (2 +), so minerals whose surface contains more Cu (2 +) minerals have a strong effect on the xanthate. The order of the effect is: chalcocite> covellite> porphyrite> chalcopyrite.
• c. The floatability of copper sulfide minerals is also affected by factors such as crystal size, mosaic size, and being original or secondary. The minerals with fine crystal and mosaic size are difficult to float. Secondary copper sulfide ore is easy to oxidize and more difficult to float than original copper ore.

As for the grinding and floating process, it is more advantageous to adopt the stage grinding and floating process for refractory copper ore, such as the re-grinding and re-separation of coarse concentrate, re-grinding and re-separation of bulk concentrate, and separate treatment of medium ore.

2.2 Flotation methods of copper oxide ore

Copper oxide (CuO) is insoluble in water, ethanol, soluble acid, ammonium chloride, and potassium cyanide solutions. It can react with alkali when slowly dissolving in an ammonia solution.

The beneficiation method of oxidized copper ore is the flotation separation method.

Flotation is one of the commonly used mineral processing techniques for copper oxide ores. According to the different properties of copper oxide ores, there are sulphidizing flotation, fatty acid flotation, amine flotation, emulsion flotation, and chelating agent-neutral oil flotation methods.

A. Sulphidizing flotation

The oxidized ore is vulcanized by adding vulcanizing agent and then the flotation is carried out with the ordinary reagents of copper sulfide flotation.

Scope of application: mainly malachite, azurite and atacamite.

Process flow: The dosage of sodium sulfide can reach 1~2kg/t during vulcanization. Because the film produced by vulcanization is not stable and is easy to fall off after vigorous stirring, and sodium sulfide itself is easily oxidized, sodium sulfide should be added in batches.

Besides, the vulcanization speed of malachite and azurite is relatively fast, so the vulcanizing agent can be directly added to the first flotation cell with no need to stir in advance during vulcanization and adjust the amount of vulcanizing agent according to the foam state.

Use of reagents:

• a. When there is much mud in the sludge: water glass must be added.
• Collector: butyl xanthine, or butyl xanthine mixed with Aeroflot.
• b. The PH value of flotation pulp: is around 9.
• c. Improve the flotation index: ammonium sulfate, sulfuric acid, etc.

B. Fatty acid flotation

Fatty acids and their soaps are mainly used as collectors of fatty acid floatation, also known as direct flotation. During flotation, water glass (gangue inhibitor), phosphate, and sodium carbonate (slurry regulator) are also usually added.

Scope of application: copper oxide mineral whose gangue is not carbonated.

There is a practice of mixing vulcanization and fatty acid methods. Firstly float the copper sulfide and part of the copper oxide with sodium sulfide and xanthate, and then float the residual copper oxide with fatty acid.

For example, the ore in the Nchanga processing plant in Zambia contains 4.7% copper. The copper content was achieved to 50%-55% through flotation by adding 500 g/t of lime (pH 9-9.5), 10g/t of cresol (foaming agent), 60 g/t of ethylxanthate, 35 g/t of amyl xanthate, 1kg/t of sodium sulfide, 40g/t of palmitic acid and 75 g/t of fuel oil.

C. Amine flotation

Amines are mainly used as collectors in this method. It can be used not only for the separation of copper oxide, but also for the beneficiation of copper oxide, lead, and zinc minerals.

Scope of application: malachite, azurite and chlorchlorite, etc.

The premise of the amine flotation method is to first find effective inhibitors of gangue, such as seaweed powder, polyacrylic acid, etc.

D. Emulsion flotation

It is mainly to sulfurize the copper oxide mineral first and then add the copper accessory ingredient to create a stable oil-wet surface. Then, the neutral oil emulsion is used to cover the mineral surface, resulting in a strong hydrophobic floating state. In this way, the mineral can be attached to the foams firmly to complete the separation.

Emulsion flotation includes three aspects:

1. a. Use the selective copper accessory ingredients, including benzotriazole, mercaptobenzothiazole, diphenyl guanidine, etc.
2. b. Add non-polar oil emulsion to improve the adhesion of minerals and foams.
3. c. Use selective inhibitors such as acrylic polymers and sodium silicate.

E. Chelating agent-neutral oil flotation

It completes the flotation by using the mixture of the chelating agent and neutral oil as a collector.

Scope of application: refractory copper oxide (such as silicon malachite)

It not only has high selectivity and collecting effect but also can guarantee a high sorting index and reduce the consumption of reagents. Chelating agents also have a selective inhibition effect.

However, the cost of chelating agents is relatively high. Currently, the chelating agents used include polyamine and condensation of organic halides, etc.

Problems should be noticed in the flotation of copper ore:

a. Many problems should be paid attention to in the flotation of copper ore, such as the length of the vulcanization time, whether to add sodium sulfide in batches, and the proportion of chemicals. Here is a brief introduction.

• b. The vulcanization time. Different ores require different vulcanization times. Generally speaking, it should be short rather than longer. The suitable vulcanization time is 1 to 3 minutes. After 6 minutes, the recovery rate and concentrate grade will decrease.
• c. Add sodium sulfide in batches. The roughing time for processing the ore in the concentrator is about ten minutes, while the ore contains a large amount of carbonaceous gangue and the divalent sulfur ions disappear quickly in the slurry. So the effect of adding sodium sulfide in batches is better than that of adding it once.
• d. Add sodium sulfide proportionally. Generally, copper oxide floats in the liquid at a slower speed, and reducing the number of cycles of the mineral in the flotation process can obtain a higher recovery rate. It is of great significance to study the distribution ratio of sodium sulfide among different operations to catch the mineral at the right time.

Jordan is the writer of the blog with a broad knowledge of this industry. He hopes to help you in your projects sincerely. Here is the website: https://www.ftmmachinery.com/