7 Kaolin Beneficiation Methods You need to Know

The purpose of kaolin beneficiation is to improve the whiteness of kaolin by removing harmful dyeing impurities such as iron, titanium and other organic matter, or to improve the quality of kaolin by removing sandy minerals such as quartz and feldspar. The kaolin purification processes currently used mainly include gravity separation, magnetic separation, flotation, leaching, chemical bleaching and roasting, etc. Before we have talked about the kaolin mining process, this article will take you to learn 7 kinds of kaolin purification processes.

Gravity separation process mainly uses the density and particle size difference between kaolin and gangue to remove light organic matter and high-density impurities containing iron, titanium and manganese to achieve the purpose of kaolin purification.

Kaolin gravity separation is to replace washing and screening processes with small cone angle cyclone group or centrifuge, which can not only achieve the purpose of washing and classification, but also remove some impurities. However, it is difficult to obtain the qualified kaolin products by gravity separation process. After gravity separation, calcination, magnetic separation and leaching methods must be used to obtain qualified products.

Kaolin magnetic separation process is mainly used to remove the weakly magnetic dyeing impurities such as hematite, siderite, pyrite and rutile in kaolin. Magnetic separation doesn't use chemicals and doesn't pollute the environment, so it is widely used in the purification process of non-metallic minerals.

The magnetic separation process solves the problem of exploitation and utilization of low quality kaolin resources which have no commercial exploitation value due to high iron content. The superconducting magnetic separator can directly process the kaolin containing many impurities. However, it is difficult to obtain high-quality kaolin products through single magnetic separation process. At present, other processes such as chemical bleaching are needed to further reduce the iron content of kaolin products.

Flotation process can effectively remove iron, titanium and carbon impurities in kaolin, and realize the recycling and reuse of low-grade kaolin resources such as coal series kaolinite. Kaolin particles are finer and more difficult to float than gangue minerals. Therefore, kaolin flotation process mostly uses reverse flotation to achieve better removal of impurities, such as carbon removal, desulfurization and iron removal by reverse flotation.

Flotation can significantly increase the whiteness of kaolin. The disadvantage is that the added chemicals cause higher production costs and environment pollution.

Leaching is the method of dissolving and removing certain impurity components selectively in kaolin by adding leaching chemicals. Such as acid leaching (use of hydrochloric acid or sulfuric acid) and microbial leaching method.

Compared with other purification processes, the leaching process is simple, which can significantly reduce the production cost and effectively develop and utilize low grade kaolin. However, strict environmental assessment and economic benefit assessment must be carried out when microbial leaching is used.

Chemical bleaching process refers to the method of removing ferric ions and their oxides by adding chemicals. Kaolin chemical bleaching method includes oxidation, reduction and oxidation-reduction method. Chemical bleaching can greatly improve the whiteness of kaolin products. However, its production cost is high and it is mostly used for further purification of impurity removal kaolin concentrate.

The chemicals used in the process, such as sodium disulfite, will produce acidic waste gas and waste water, which has a great impact on environmental pollution. Therefore, environmental protection and economic rationality should be considered when using chemical bleaching process.

Roasting is also an important purification process to improve the whiteness of kaolin. The carbon impurities in kaolin can be removed by roasting process. For example, magnetic impurities can be removed by magnetic roasting and magnetic separation, and some metal impurities can be removed by chlorination roasting.

The roasting process can greatly improve the whiteness of kaolin to obtain high quality kaolin products, realize the utilization of low grade kaolin resources, and obtain high quality kaolin products However, this method consumes a lot of energy and will pollute the environment during the production process.

It is difficult to obtain high-quality kaolin products with a single beneficiation process, especially for low-grade coal series kaolin and kaolin with complex compositions. In the actual production of kaolin, the combination of multiple beneficiation processes is often used. The common purification process of kaolin is shown in Table 1.

Table 1 Common Kaolin Purification Process Flow

The above are the 7 methods for processing kaolin. In actual production, it is often necessary to combine multiple purification processes to obtain qualified kaolin concentrate. Before production, it is recommended to do the beneficiation test first, and develop the appropriate beneficiation process according to the test results.

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