What is bead mill
The bead mill is a modular mill specially used to grind fine particles to sub-micron size. The processing material of the bead mill includes three stages: wetting, grinding and dispersing.
Material of bead mill beads
The materials of the beads (grinding media) are generally divided into glass, ceramic and steel. Except for the ordinary 2-3/3-4 mm glass beads used by the vertical sand mill, other equipment uses zirconia beads with a size of 0.8-1.2 mm.
How does a bead mill work
The working principle of the bead mill is that the beads (grinding medium) and the material are placed together in the container, and the container is stirred by the high-speed rotating dispersing disc, so that the solid particles and beads (grinding medium) in the material produce strong shearing, scouring, Collision, to achieve the purpose of crushing, grinding and dispersion.
Bead mill types
There are two types of bead mills: horizontal and vertical.
Compared with other superfine crushing equipment, what are the advantages of sand mills?
Bead mill vs. ball mill
Many researchers have done a lot of experiments on the grinding efficiency of ball mills and bead mills, and the conclusion is that bead mills are much better than ball mills in terms of grinding efficiency and preparation cost. Moreover, the experiment also proved that the bead mill can produce powder with an average particle size of less than 0.5μm, which is much smaller than the particle size of the product ground by the ball mill.
Experiment: crushing and processing of piezoelectric ceramic materials
Researchers put 3 kg of piezoelectric ceramic composite material in the ball mill container, vibratory grinding hopper and bead mill barrel respectively for pulverization. All of them are processed by wet processing, and samples are taken at regular intervals to measure the particle size and distribution. Compare the processing time of the three types of equipment when the powder particle size D50 reaches about 0.5μm and the particle size distribution of the processed powder.
It can be seen from the experimental results that from the perspective of crushing efficiency and particle size distribution, the vibratory milling process is better than the ball milling process, and the bead milling process is significantly better than the ball milling and vibrating milling processes. This is related to the size of the grinding ball used for crushing and the speed and energy of the grinding ball. Generally, the smaller the grinding ball, the greater the grinding effect, the finer the pulverization, and the narrower the particle size distribution.
In the experiment, the diameter of the zirconia ball used in the bead mill is 1.5 mm (1.5 Kg), and the diameter of the zirconia ball used in the ball mill and vibratory mill is 20 mm, 15 mm and 8 mm (7.5 Kg). The grinding surface area of the sand mill is much larger. For ball milling and vibration milling. The running speed of the grinding ball during sanding is 1800 rpm, the vibration speed of the grinding ball during vibratory grinding is 600 times/min, and the running speed of the grinding ball during ball milling is 65 rpm. Therefore, the bead mill has the highest crushing efficiency, the finest powder particles, the narrowest particle size distribution, and the best crushing quality.
Based on the above pulverization test results, the researchers concluded that the piezoelectric ceramic composite material is pulverized by a bead mill, which is more conducive to improving the microstructure of piezoelectric ceramics, and improving the mechanical properties and piezoelectric dielectric properties of piezoelectric ceramic materials. For the ultrasonic atomization transducer element, it can reduce the performance attenuation rate by 50%, and obviously extend its service life from 5000h to 8000h.
Bead mill vs. jet mill
Compared with other grinding equipment (jet mill), the bead mill has the advantages of high fineness, strong continuity, and high efficiency. The fineness requirements can be adjusted by adding or subtracting grinding media or grinding with different media. The grinding medium of the bead mill runs at high speed, and the grinding action is mainly impact and shear force. The zirconia bead grinding media used in the experiment achieves zero pollution to the raw materials, and has a small particle size and many contact points, which can be ultra-fine grinding and dispersion.
The raw materials are grinded at a high speed in a grinder, the liquid phase is uniformly mixed and fully reacted to obtain a slurry, and then through a spray dryer, the slurry is atomized, and in contact with hot air, the moisture quickly vaporizes. In this process, the slurry The material is granulated and dried to obtain a lithium battery electrode material.
Disadvantages of bead mill
Although the bead mill has some advantages unmatched by other types of equipment in terms of dispersion and grinding, the bead mill also has its own application limitations. For example, the bead mill has requirements for the fineness of the raw materials to be ground, and the general requirement is less than 80 Mesh (<0.18 mm). In addition, the bead mills currently used in the coatings’ industry have relatively small specifications, and the output of a single device is not large, making it difficult to meet the output requirements of the ceramic industry.
In the processing of many materials, it is common to see the combined use of ball mills, jet mills, and bead mills. Some researchers have used a combination of ball mills and agitated bead mills to significantly shorten the grinding time. Improve the grinding efficiency, and also save the grinding power consumption. Some processes are first handed over to a ball mill to stir and mix, and then grind with a bead mill. In some processes, a bead mill is used to grind, and then the sintered material is pulverized with a jet mill. The three cooperate with each other to achieve the optimal processing and best performance of the material.