Yuan Lei tells you | one article to understand the fine processing technology of kaolin

Release time:

2024-01-29 09:35


Yuan Lei tells you | one article to understand the fine processing technology of kaolin


The processing technology of kaolin varies with the nature of the raw ore, the use of the product and the quality requirements of the product.In general, the processing technology of kaolin includes:Purification whitening, ultrafine processing, modification, etc.
1. Purification and whitening of kaolin


The main minerals of kaolin are kaolinite and halloysite. In addition to kaolinite group minerals, clay minerals such as montmorillonite, illite and pyrophyllite are also often accompanied by non-clay minerals such as quartz, feldspar, iron minerals and titanium minerals and organic matter.To generate energyKaolin products that meet the needs of various industrial fields are often purified by physical methods, chemical methods and high-temperature calcination methods.


(1)physical purification methodThe main use of different mineral particle size, density, magnetic and surface adsorption and other physical properties of the differences in the separation of some non-clay minerals, including hand selection, water separation, flotation, magnetic separation and so on.


(2)Chemical purification and bleachingIt is mainly used to remove iron-containing minerals in kaolin. The main methods are acid leaching, chlorination, alkali treatment, reduction, oxidation and redox combination.


(3)high temperature calcination methodIt is the best method to remove carbon and whiten, and it is also a necessary processing method for kaolin in coal strata. Usually calcined at 650~1050 ℃, the kaolin phase completely changed, while some impurities volatile, to improve the whiteness and insulation effect. Sometimes chlorination roasting, oxidation roasting and other high-temperature treatment methods can be used to remove the iron and titanium elements in kaolin.
2, Kaolin ultrafine processing
The main methods of ultrafine processing of kaolin are: mechanical crushing, classification, intercalation-peeling and chemical synthesis.


(1)mechanical crushing methodThe main use of the characteristics of mineral layered structure, under the action of external force, the destruction of the force between the layer and the layer, so as to achieve the purpose of ultra-fine, but the energy consumption is large.


(2)grading methodThe ultra-fine kaolin is obtained by settling kaolin in liquid mainly according to Stokes's law, but the cost is high and the output rate is low.


(3)Intercalation-peeling methodThe main use of intercalation to make kaolin in the mineral interlayer expansion, the bonding force is greatly weakened, after the removal of the intercalation object, the original stacked sheet kaolinite will naturally decompose into small sheet kaolinite, to achieve the purpose of natural stripping.


(4)chemical synthesis methodGenerally using rock minerals or aluminum silica gel as raw materials by hydrothermal method to obtain ultra fine synthetic kaolinite. It has high purity, good suspension stability, good light scattering, and other properties.


Particle size is one of the important indicators to measure the quality of kaolin products.At the same time, the particle size and distribution of kaolin are also important factors affecting its viscosity. At present, the research on ultra-fine kaolin mainly focuses on the intercalation-peeling method. Liu Qin-fu and others used high-purity soft kaolin as raw material and the preparation process of intercalation-peeling method. The average diameter of the nano-scale kaolinite wafers is 300 ~ 500nm, and the average thickness reaches 20 ~ 50nm.


Although the particle size of kaolin has been processed to nano-scale,Immature viscosity reduction technology is still the main reason for the lack of kaolin for paper coating in ChinaLiu Pan et al. found that a relatively concentrated particle size distribution can effectively reduce the viscosity of the slurry.


Kaolin mineral nanomaterials can not only reduce the viscosity of the slurry, but also have good surface effect and small-scale effect, which is an important research direction to expand the application range of kaolin.
3, Kaolin modified


Modification is one of the most important deep processing technologies for non-metallic minerals today. Due to the differences in mineral formation conditions and mining and processing methods of kaolin, its physical and chemical properties are very different, so that its application range is limited. Therefore,Research and development of different modification methods is an important means to expand the scope of application and effect of kaolin. The modification methods of kaolin mainly include acid-base modification, surface modification and intercalation modification.


(1)acid-base modificationMainly for calcined kaolin, according to the different chemical environment of Al and Si in the phase change process, the kaolin is calcined and activated at a certain temperature, so that the Al and Si can react with acid or alkali to change its acidity, pore size and specific surface area.


(2)surface modificationThe surface of kaolin powder is treated by physical, chemical or mechanical methods to change the physical and chemical properties of its surface, which can effectively improve its whiteness, brightness, surface chemical activity and compatibility with polymers.


(3)intercalation modificationIt mainly refers to the direct or indirect insertion of some organic molecules between kaolinite layers without destroying the original layered structure of kaolinite.
4, Kaolin processing process


At present, the common processing technology of kaolin in industry is dry and wet.


(1)dry processIt generally includes several processes such as crushing, drying (usually in a rotary dryer), fine grinding and air flotation. The process can remove most of the sand and gravel, and is suitable for processing those ores with high whiteness, low sand and gravel content and suitable particle size distribution. Dry processing has low production cost and is generally suitable for dry areas. The products are usually used for low-cost fillers in rubber, plastics and paper industries.


(2)wet processIt includes several stages of slurry dispersion, classification, impurity sorting and product treatment. The general process is: raw ore → crushing → ramming → desanding → cyclone classification → flaking → centrifuge classification → magnetic separation (or bleaching) → concentration → pressure filtration → drying → packaging.


(3)Coal (hard) kaolinIt is a unique kaolin resource in China. At present, the production basically adopts the first superfine and then calcined or the first superfine processing technology. The process flow of ultrafine first and then calcination is generally as follows: raw ore → crushing → crushing → ramming → wet ultrafine grinding or flaking → drying → calcination → depolymerization → classification → packaging. The process flow of first calcination and then ultrafine is generally as follows: raw ore → crushing → crushing → calcining → wet ultrafine → drying → packaging.
Taking China Kaolin Company as an example, the kaolin production process is divided into two parts: mining and mineral processing. Mining process flow: rock drilling in the working face → blasting → loading and unloading transportation → lifting → ground transportation → hand selection → kaolinite raw ore. Beneficiation process: kaolin ore → crushing → pulping → cyclone classification → concentration → pressure filtration → natural drying → block kaolin. To produce powdered kaolin with low water content and high grade, it needs to go through grinding and drying process.

China is rich in kaolin resources, but there are not many natural flake kaolin resources that are really suitable for paper pigments. It is particularly important to strengthen the processing technology of raw ore. Although the deep processing technology and products of China's kaolin industry have developed rapidly in recent years, there is still a big gap between the overall technical level and developed countries, mainly in the backward mining and mineral processing methods, low degree of mechanization, backward processing technology, low added value of products, and insufficient in-depth research on the physical and chemical properties of kaolin. Therefore,In the future, China will strengthen research and development of new mining, mineral processing technology and technical technology to improve the quality of kaolin concentrate and improve market competitiveness.; Strengthen applied basic research, develop new products with high added value, and broaden the scope of application in high-tech fields.

Technology, kaolin, processing, mineral, modification, calcination, main, method, kaolinite, raw ore

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