Grinding equipment and applications (4)

Other types of mills and superfine mills

(A) a disk mill disk mill is composed of several rotating rollers, urging the material in the grinding equipment for grinding. According to the structural form of the mill, it can be divided into two types: disc fixed type and rotary type; according to the way of applying the work rolls, it is divided into a suspension roll type and a spring roll type or a hydraulic roll type. At present, the disc mill mainly includes a Raymond mill, a roller disc mill and an E-type mill. This type of equipment is often used to process brittle or medium hardness materials.
A Raymond Raymond known as hanging roller mill, a medium speed is fine grinding apparatus for grinding coal, non-metallic mineral, glass, ceramic, cement, gypsum, fertilizer, and pesticides and other materials Its product fineness is in the range of 120~325 mesh. According to the number of rollers, there are three types of rollers (commonly known as 3R), four rollers (4R), and five rollers (5R); the three specifications of the Raymond mill work the same. Raymond mills are roller mills in which the disc is fixed and the rollers rotate (Fig. 16). The shaft of the roller 2 is mounted on a rapidly rotating plum blossom frame 1. The disc (ring) 3 is fixed, and 3~5 rollers are suspended on the frame, and revolved around the central axis of the machine body, and the roller itself rotates. Due to the centrifugal force during the revolution of the roller, the roller is flared outwardly and pressed against the grinding ring 3. The material fed from the ore portion 5 falls to the bottom of the grinding ring, and the material is shoveled by the blade 6 between the roller and the grinding ring, and is ground by the grinding action of the rapidly rotating roller. The Raymond mill usually forms a closed circuit system with dry classification; the material is discharged from the mine discharge section 7 with the airflow, and then is classified into an Impeller type wind classifier disposed in the upper part of the body.

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The impeller of the classifier consists of a turntable and a number of radial blades. The higher the rotational speed of the impeller, the finer the particle size of the graded material. In order to improve the classification efficiency and adjust the classification granularity, a double-row impeller classifier can be fabricated. The single-row impeller classifier has a graded particle size of between 60% and 0.147 mm and between 95% and 0.074 mm; the double-row impeller has a graded particle size of between 60% and 0.147 mm to between 99.9% and 0.043 mm. Another single-cone or double-cone type classifier has a simple structure, but the adjustment of the classification granularity is not as accurate as that of the impeller type classifier; the single-cone type can only be used for classifying large dry 0.14 mm materials.
There are many operational parameters affecting Raymond mill, including: the type of wind classifier and working parameters, the speed of the roller, the number of rollers and the working characteristics of the blower.
Compared with tube mill, Raymond mill has the main advantages: it can grind and dry materials at the same time; the moisture content of the milled material before drying can reach 15~20%; the energy consumption is low, the unit power consumption is reduced by 20~30 %; the ore size is generally 5~10 mm, the large mill can reach 30~50 mm; the floor space is small, only 50% of the tube mill; the investment of the whole system is lower, the equipment price is 70 of the tube mill %; high grinding efficiency, large processing capacity, and the output of Taiwan is as high as 50 tons. The main disadvantage of this type of grinder is that the roller sleeve has a short service life (about 4500 to 8000 hours). Therefore, the sleeve needs to be made of a material having high hardness and good wear resistance.
Since the unit energy consumption and grinding efficiency of this mill are superior to that of the tube mill, various types and specifications of Raymond mill are produced at home and abroad.
B Roller Disc Mill This disc mill has a different structure than the Raymond mill. It is a disc-type disc mill. The main types are: Loe sche type or Lopu-lco type and MPS type. This type of disc grinder has 2 to 4 tapered rollers, and the shaft of the roller is mounted at an inclination (inclination angle of about 15°); the roller is pressed tightly against the disc of the mill by a spring or hydraulic system. The material is fed into the grinding disc through a sealed feeding device. Due to the rotary motion of the grinding disc, the material is crushed by crushing and grinding of the tapered roller. The crushed material enters the wind classifier along with the airflow; after the material is classified, the coarse fraction returns to the grinding zone for regrind, and the fine fraction is discharged into the dust collecting and dust removing device, and is separated from the airflow to become the final product.
Fig. 17 is a schematic view showing the structure of a VX type rotary roll type disc mill manufactured in Japan. The material is fed from the screw feeder 1 to the mill 2, where the material is pulverized by the rotating disc 4 and the roller 5; the pulverized material is lifted by the air flow for classification. 6 is a high-speed rotating rotor, which is located at the head of the classification zone; in the rotor 6, fine particles are taken out by the wind flow into finished products, and the coarse particles are returned to be ground. Figure 18 shows a different application system for a VX mill. The mill can be used to treat medium and hard materials such as manganese dioxide, limestone , Пlite, talc , coke, etc., and its product size can be coarse and fine (fine to a few microns). Figure 19 shows the product particle size distribution of different materials. [next]

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The roller disc mill is mainly used for grinding materials with medium hardness below. The remarkable features are: high output, a roller mill with a diameter of 5 meters, the output reaches 550 tons/hour, the liner has a long service life, and the disc and the roller The life of the lining board is generally up to two years, the wear cost of the lining board only accounts for 2~5% of the production cost; the unit power consumption is low, about 10~20% lower than the conventional mill; the size of the ore is larger, generally 50~ 100mm, large roller mill can reach 150~300mm, eliminating the need for two-stage crusher ; at the same time, material grinding and drying operations, the moisture content of the treated material can reach 15~20%; It is 50% of the ordinary tube mill; the equipment price is low, only 70% of the tube mill; the mill production process can be automatically controlled or controlled by an electronic computer. [next]
C steel ball type disc mill This type of grinding machine is also called E type (a row of steel balls) disc grinding machine. Other series and types of mills have two or three rows of steel balls. The E-type disc mill consists of upper and lower grinding discs (or races) and a row of steel balls. Generally 8 to 10 cast steel balls are used as grinding media. The steel ball is located between the two grinding discs, and the upper seat ring is fixed, and the steel ball is applied by means of a spring or a hydraulic device, so that the material between the steel ball and the grinding disc is ground. The ground product enters the wind classifier mounted on the mill for classification, the qualified product is discharged, and the coarse material is returned and then ground. The disc cast iron, high-manganese cast iron wear resistant material is made of hard nickel.
China's Huainan Power Plant and other units have adopted this type of mill to grind coal.
(2) Vibration mill The vibration mill combines mechanical vibration, material fracture, mixed transmission and physical and chemical reaction. It is a grinding equipment with strong grinding ability and fine particle size (several micrometers). . The vibration mill was developed by Germany in the 1930s. In the 1960s, it was widely used in building materials, chemicals, medicine and other departments, and formed a series of products. The general mill works with a vibration acceleration of 9.8 m / s ² (gravity acceleration), while the vibrating mill works with a vibration acceleration of (3~10) × 9.8 m / s ² , so The person has a strong crushing effect. The vibration frequency of the vibration mill can reach 1000~1500 times/min, which greatly increases the number of impacts of the grinding medium on the material per unit time. This high-frequency impact prevents re-polymerization of the surface cracks of the material being ground, so it is well suited for ultra-fine grinding of materials.
According to research by Batal et al. in the 1950s, the vibration grinding efficiency increases with the increase of vibration intensity and increases with the increase of amplitude. Under the guidance of this theory, vibration grinding has achieved rapid development. For example, in the 1970s, the palla-type vibrating mill in Germany was later developed in Japan, similar to the CHA type and RSM type. The research on vibration mill in China started late, but it has made great progress. Wenzhou Mining Machinery Factory has a series of products; the vibration strength of MGZ-1 vibration mill developed by Xi'an Metallurgical and Architectural College is 15g, and its performance is better than similar foreign products. The planetary vibration mill developed by South China University of Technology combines the principles of planetary grinding and vibration grinding to achieve better grinding results.
According to the vibration characteristics, the vibrating mill is divided into two categories: inertial type (Fig. 20) and rotary type (Fig. 21). According to the number of cylinders, it is divided into two types: single cylinder and multi cylinder (Fig. 22).

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