Properties and Beneficiation Technology of Nickel Ore

According to the different compositions of nickel ores, the selected process methods are also different. Fodamon engineers will share the following nickel ores based on years of experience.

Beneficiation of copper nickel sulfide ore

This type of ore is mostly magmatic molten copper nickel ore, in which the rich ore containing more than 3% nickel can be directly smelted; Ore containing less than 3% nickel shall be beneficiated.

(1) Mineral Composition and Beneficiation Method of Copper Nickel Sulfide Ore

The common metal minerals in this type of ore are: pyrrhotite, pentlandite and chalcopyrite, as well as magnetite, pyrite, ilmenite, chromite, chalcopyrite, copper blue, chalcocite, bornite and platinum group minerals; Gangue minerals include olivine, pyroxene, plagioclase, talc, serpentine, chlorite, actinolite, mica, and sometimes quartz and carbonate.

Copper in copper nickel ore mainly exists in the form of chalcopyrite; Nickel mainly exists in the form of free nickel sulfide, such as pentlandite, goethite and violarite. A considerable part of nickel occurs in pyrrhotite in isomorphism, and there is a small amount of nickel silicate.

The main beneficiation method of copper nickel sulfide ore is flotation, while magnetic separation and gravity separation are usually auxiliary beneficiation methods.

(2) Floatability of main nickel minerals and flotation characteristics of copper nickel ores

Pyrrhotite, goethite and nickel bearing pyrrhotite can be effectively floated with butyl or amyl and other high-grade xanthates. The floatability of pentlandite and goethite is between chalcopyrite and pyrrhotite. Pyrrhotite can be flotation well in weak acidic, weak alkaline or neutral media; Nickel goethite can also be better flotation with butyl xanthate in weak acidic, neutral or weak alkaline medium; Nickel bearing pyrrhotite is suitable for flotation in acidic or weak acidic medium, but the flotation speed is slow.

Pyrrhotite, goethite and nickel bearing pyrrhotite can all be inhibited by lime, but their degree is different. Pyrrhotite is easier to inhibit, while pentlandite and goethite require excessive lime. Unlike pyrrhotite and pyrite, other alkalis do not inhibit pentlandite and goethite. The effect of separating pentlandite and chalcopyrite with lime alone is not good enough, and a small amount of cyanide is usually added to inhibit pentlandite. Pyrrhotite can be quickly oxidized by oxygen in the air, forming an iron hydroxide film on its surface, which reduces its floatability. Pyrrhotite is oxidized faster in the air than pentlandite. Copper sulfate is the activator of pentlandite, especially pyrrhotite. Nickel minerals can be reactivated with copper sulfate after being inhibited by lime (rather than oxide). In order to improve the activation of nickel minerals by copper sulfate, it is sometimes necessary to add a small amount of sodium sulfide in advance.

At present, nickel silicate minerals cannot be separated by industrial flotation, so the nickel silicate content in ores is an important factor affecting the nickel recovery.

Based on the properties of copper nickel ore, its flotation process has the following characteristics: simple flotation process, long flotation time, less times of concentration, multiple points of decentralized concentration, and early recovery of nickel mineral; The grade of nickel concentrate is generally 4~8%, and the higher one can reach 13~15%. Removal of pyrrhotite, talc, chlorite, actinolite, serpentine, mica and other easy floating gangue is the key to improve the quality of nickel concentrate; In order to strengthen nickel mineral flotation, mixed collectors are often used; The combined flowsheet of flotation and magnetic separation is often used to remove pyrrhotite.

(3) Flotation process of copper nickel ore

When flotation copper nickel sulfide ore, the collector and frother of flotation copper sulfide ore are often used. A basic principle for determining the flotation process is that it is better to let copper enter the nickel concentrate than to avoid nickel entering the copper concentrate as much as possible. Because the nickel in the copper concentrate loses a lot in the smelting process, the copper in the nickel concentrate can be completely recovered. Copper nickel ore flotation has the following four basic processes:

(4) Direct preferential flotation or partial preferential flotation process

When the copper content in the ore is much higher than the nickel content, this process can be used to separate the copper into a separate concentrate. The advantage of this process is that copper concentrate with low nickel content can be obtained directly.

(5) Mixed flotation process

It is used to separate ores with copper content lower than nickel, and the obtained copper nickel mixed concentrate is directly smelted into high nickel matte.

(6) Copper and nickel are mixed flotation from ores, and then copper concentrate containing low nickel and copper nickel concentrate are separated from mixed concentrate. After smelting the nickel concentrate, high nickel matte is obtained, and then the high nickel matte is separated by flotation.

(7) Mixed preferential flotation and partial nickel recovery from mixed flotation tailings

When the floatability of various nickel minerals in ore is greatly different, nickel containing minerals with poor floatability can be further recovered from its tailings after copper nickel mixed flotation.

(8) Cu Ni separation

Copper is a harmful impurity in nickel smelting, and copper grade in copper nickel ore has industrial recovery value, so copper nickel separation technology is an important subject in copper nickel ore dressing. Copper nickel separation technology includes copper nickel mixed concentrate separation and high nickel matte separation. Generally, the mixed concentrate separation method is adopted for the ores with coarse grain size of copper nickel minerals and not closely embedded with each other; However, for copper nickel minerals with fine particle size and very dense distribution, high nickel matte separation process is often used.

(9) Separation process of copper nickel mixed concentrate

At present, the most commonly used separation methods of this process are lime cyanide method and lime sodium sulfide method. Sometimes, slurry heating measures can improve the separation effect. In addition, there is bisulfite method.

(10) Separation process of high nickel matte mixed concentrate

This process has better technical and economic effects than separation smelting and hydrometallurgy, so it is widely used.

High nickel matte mainly consists of copper sulfide (Cu2S) and nickel sulfide (Ni3S2), followed by Cu Ni alloy, cobalt, platinum group metals and some iron impurities. The composition of high nickel matte can be controlled artificially during smelting. Iron content and cooling rate are two main factors for high nickel matte flotation separation. They not only affect the material composition of high nickel matte, but also affect its crystal structure.

Iron is a harmful impurity in the separation and flotation of high nickel matte, which can lead to the complexity of the composition of high nickel matte. When the iron content is less than 1%, there will be compounds similar to bornite and pentlandite, which is not conducive to flotation and affects the recovery of cobalt; When the iron content is more than 4%, not only the composition of high nickel matte becomes more complex, but also the crystal structure becomes finer, which is not conducive to flotation. The production experience shows that the iron content in high nickel matte should be controlled within the range of 2~4%.

The high cooling rate of nickel matte also has a great influence on its separation. When it is slowly cooled from 800 ℃ to 200 ℃, the crystal grain size of copper and nickel minerals becomes coarser. Especially when the slow cooling temperature drops to 510~520 ℃, nickel sulfide undergoes crystal transformation, and changes from NiS2 to a-Ni3S2, which makes copper sulfide dissolved in nickel sulfide separate out, thus helping to reduce the copper content in nickel sulfide ore. Therefore, ensuring the slow cooling rate of high nickel matte can improve the separation effect of high nickel matte flotation.

Nickel oxide ore treatment

Nickel laterite in nickel oxide ore has high iron content, low silicon and magnesium content, and nickel content is 1-2%; However, nickel silicate ore has low iron content and high silicon magnesium content, with nickel content of 1.6~4.0%. At present, nickel oxide ore is mainly exploited by nickel laterite. Because nickel in nickel oxide ore is often dispersed in gangue minerals in the same way as the other minerals, and the particle size is very fine, it is difficult to obtain good results by directly treating it with mechanical beneficiation method. After the ore is calcined to change the mineral structure, although better technical indicators can be obtained, the cost is high and it has not been used in industrial production.

At present, crushing, screening and other processes are often used for nickel oxide ore treatment to remove large bedrock ore blocks with weak weathering degree and low nickel content in advance, so the enrichment is relatively low.

In recent years, due to the continuous development of nickel smelting technology, the increase of nickel consumption and the continuous reduction of nickel sulfide rich ore resources, the development and utilization of nickel oxide ore has been paid more and more attention. Nickel oxide deposits are generally shallow, suitable for large-scale open-pit mining, but also for selective mining. Due to the low mining cost, it has certain competitiveness compared with nickel sulfide ore.

The smelting and enrichment methods of nickel oxide ores can be divided into two categories: pyrometallurgy and hydrometallurgy. Pyro smelting can also be divided into matte smelting, ferronickel process and granular iron process. Hydrometallurgy also includes reduction roasting atmospheric ammonia leaching and high pressure acid leaching.

The rotary kiln grain milling method in pyrometallurgy belongs to an ancient method. Its disadvantages are that the process is complex, the nickel content of grain iron is low, the nickel recovery rate is low, and cobalt cannot be recovered; Electric furnace smelting is characterized by high nickel recovery rate. Part of the nickel is drilled into ferronickel, which can be recovered in the refining process. This method is suitable for the treatment of silicon magnesium nickel ore. When it is used in laterite ore with high iron content, the iron recovery rate is low and the power consumption is large.

The atmospheric ammonia leaching method in hydrometallurgy has the disadvantage of low cobalt recovery; The high-pressure acid leaching method is suitable for treating nickel oxide ores with low magnesium silicate content.

At present, nickel oxide is mostly treated by smelting ice nickel in electric furnace; However, the rotary kiln granulation iron process is rare. Hydrometallurgical methods, such as ammonia leaching and acid leaching, have been applied in industry. Other new nickel oxide smelting methods, such as high-temperature chlorination, sulfuric acid roasting and other extraction processes, are still in the research stage and have made some progress.

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