Research Status and Development of Kaolin Stripping Technology in China

The deepening technology of kaolin mainly includes beneficiation and purification, ultrafine pulverization and surface modification, etc., and the peeling is a technique of ultrafine pulverization and nanocrystallization, which belongs to the category of ultrafine pulverization for producing nano-Gaoling, but it is super Fine crushing has different requirements.

Stripping is defined as a mechanical or chemical method in which a laminated or book-like kaolin is peeled off into a single piece to reduce the particle size and reach the nanometer scale. The kaolinite unit layer and the unit layer are Weak hydrogen bonding, the hydrogen bond is broken, and the kaolin has a rupture along the axial direction between the layers to form a single sheet body. The difference between the stripping and the ultrafine pulverization is that by selecting the appropriate force and the combination of different forces, it is ensured that the Kaolin is not damaged during the stripping process, but the equipment and the art used in the two are the same.

High pressure extrusion
The principle of the high-pressure extrusion method is to use a piston pump to give a certain pressure to the slurry in the container, so that the high-pressure slurry passes through the treated narrow gap through the treated nozzle surface, and is swept out at a certain speed, high speed. The sprayed slurry hits the impeller in the normal pressure zone and suddenly changes the direction of motion, resulting in a strong cavitation effect. When the high-pressure slurry is sprayed from the nozzle, the kaolinite deposit in the slurry is broken along the layer and the layer due to the sharp drop in pressure, forming a thin kaolinite sheet.

Chemical immersion
The chemical immersion method is to soak kaolin in a chemical reagent, and by chemical action of the chemical reagent and kaolin, the immersion agent is inserted between the layers of the kaolinite, so that the interlayer spacing of the kaolinite is increased. After the spacing of the kaolinite layer is enlarged, the hydrogen bonding force existing between the layers becomes weak, and the sheet of kaolinite is peeled off.

Grinding and stripping
The principle of ultra-fine kaolin by grinding and stripping method is to use the relative motion of the grinding medium in water to produce shearing, pressing, impacting and grinding and stripping, so that the lamination of large-grain kaolin is peeled off and tends to The layers are separated individually. The main equipment used in the grinding and stripping method is a medium agitating mill, a ball mill and a sand mill.

The grinding and stripping method is a kaolin stripping method commonly used at home and abroad, and the main equipment used thereof includes a medium agitating mill, a ball mill and a sand mill. After the grinding and stripping equipment is connected with the computer, the function of the grinding and stripping equipment is fully exerted, and the labor intensity of the workers is also reduced, the degree of automation of the mechanical information is improved, and the safety of the production is also improved, and the product processing is ensured. Stability of yield and quality.

Liang Zonggang still other BMP-500 type grinding stripping machines and automatic control system is applied to the coal pulverization ultrafine kaolin-based, simple structure, less equipment needed, low energy consumption, high yield, a reasonable size distribution may be larger Scale production.

So far, there are many types of grinding and stripping machines, and the production capacity range is relatively simple, but generally requires a long grinding time and a high energy consumption of the grinding and stripping operation. At the same time, a large amount of special grinding and stripping medium is needed during the grinding and stripping, and some impurities are brought to the kaolin during the grinding and stripping process, so the production cost of the method is high, and the quality of the final product is not very high.

The most typical grinding and stripping equipment for kaolin is the ball mill and the medium-type agitating mill. The two devices have the same principle. They use the structural characteristics of kaolin to peel off the kaolinite sheet by shearing force, thereby making the kaolin grain size. Reduce, to achieve the purpose of ultra-fine. In recent years, there has been no major development in grinding and stripping equipment. In addition to crushing machinery, developers and producers are paying more attention to the development of equipment for classification, filtration, drying and granulation to further nano-calcite kaolin.

Shao Yaping introduced the application of the rod mill in the refinement of kaolin. First, the kaolin is calcined in the GDL granulated calcining furnace, and then the equipment is used to break up, which can get more than 1250 mesh. Fine kaolin. This kaolin production plus process is simple, efficient and reliable.

Li Sanhua other "of using a vertical stirred mill Kaolin wet ultra-fine grinding, the use of sodium hexametaphosphate as a grinding aid during grinding, the disposable kaolin having a particle diameter of less than 2μm powder of Using The ultra-fine kaolin can also be obtained by the classification technology. Li Qicheng et al. used a centrifugal classifier to carry out ultra-fine experiments on kaolin. The effects of slurry concentration and separation factor were analyzed. The particle size of 2 μm was obtained by optimization at 85%. Ultra-fine kaolin products.

Chemical immersion
The chemical immersion-peeling method is a technique in which the above two technologies are combined to super-fine Kaolin 10, that is, the kaolin is soaked with a chemical agent, and the immersion agent is immersed in the kaolin layer to make the kaolin As the interlayer spacing becomes larger, the bonding force of the hydrogen bonds between the layers becomes weaker, and the bonding force between the layers becomes weaker, thereby separating the kaolin stack.

Intercalation-ultrasonic method
The composition of the ore in kaolin is kaolinite in the form of hexagonal scales, and the single crystal is hexagonal plate-like. The aggregates are often book-like structures, so the kaolinite is easily split in a direction parallel to the plane. Dissociating the crystals of kaolinite from the layers to achieve their application at the nanometer scale will result in a qualitative improvement in the existing use and double the value of the kaolin ore.

In the development and utilization of current kaolinite, it is used as a filler and coating material for paper, a ceramic raw material, a rubber filler, an additive for paints and coatings, and the like, and the particle size is generally about 2 μm. As we all know, 0.1μm is the bottom line that can be achieved by mechanical superfine pulverization technology. Some characteristic parameters of kaolinite, including specific surface area, whiteness, particle size and shape, directly determine its technical applicability. If the kaolinite is successfully stripped to a nanometer level in a short period of time, it will bring about industrial innovation and good benefits.

Because the intercalation can weaken the interaction between the kaolinite layers, it is beneficial to the stripping process and the ultrasonic technology contributes to the intercalation reaction. Therefore, the combination of ultrasonic treatment and chemical intercalation not only hopes to achieve better stripping effect in a short time, but also maintains the crystal structure of kaolinite to the maximum extent.

Yan Linlin and others combined the intercalation method with the ultrasonic method to strip the kaolin. The kaolin was first intercalated with three different intercalating agents, urea, potassium acetate and dimethylarylene. The intercalation complex of kaolin was first prepared by saturated solution soaking method, moisture absorption method and microwave intercalation method, and then ultrasonically treated. Ultrasonic method was used to decompose the kaolinite intercalation composite, and the effect of intercalation and stripping was studied to explore the feasibility of ultrasonic stripping. Through its experimental research, the use of potassium acetate as an intercalant has a significant effect and is expected to be used in the production, and the feasibility of the method is analyzed.

Valaskova et al first intercalated kaolinite with urea, then used mechanical equipment to grind it in time, and characterized the final product by means of XRD and FT-IR. The results show that the kaolin soil treated by the intercalation-ultrasound method has a specific surface area and a median diameter which are about doubled.