Diamond Micron Powder undergoes ball milling, shaping processing, and crude purification processes. After these procedures, there is another crucial step, which involves particle size classification of the product. The main objective is to ensure that the particle size distribution is as concentrated as possible and to completely eliminate oversized particles. Because diamond micron powder particles are very fine, traditional screen classification cannot achieve precise classification. Therefore, it is especially important to choose scientific, efficient, and precise classification methods.
As the application fields of diamond micron powder continue to expand and market demands for various quality aspects of diamond micron powder gradually increase, the commonly used classification methods at present for diamond micron powder include: natural sedimentation method, centrifugal method, overflow method, and hydrocyclone method.
Diamond particles of different diameters have different sedimentation rates in water under the same specific gravity. The natural sedimentation method utilizes this principle by controlling the sedimentation height and time to classify particle sizes.
Particles in a liquid are subjected to three forces: the inherent weight of the particles producing gravity, the buoyancy of the liquid, and the resistance from the medium to the particles. The sedimentation speed of particles is related to factors such as the contact area between the particles and the medium, the viscosity of the liquid, and the friction resistance encountered by the particles when moving in the medium.
The principle of centrifugal classification is the same as that of natural sedimentation. The difference is that the centrifugal method uses centrifugal force generated by a centrifuge instead of gravity to classify the diamond micron powder product.
For coarser particles, because the particles are heavier and the sedimentation time is short, using the natural sedimentation method can increase the sedimentation distance of particles with similar diameters, which is beneficial for the precise classification of diamond micron powder products with similar specifications.
However, for finer particles, because the particles have very small weights, the free sedimentation speed in a gravity field is very slow. Using the natural sedimentation method will greatly prolong the production cycle, and occupy a large amount of classification containers and space. Ultrafine particles may even be unable to achieve effective classification due to Brownian motion and interference sedimentation among particles. In a centrifugal force field, the centripetal acceleration far exceeds gravitational acceleration, greatly increasing the movement speed of micro-powder particles, thereby accelerating the classification speed.
Therefore, many diamond micron powder production enterprises adopt a combination of natural sedimentation and the centrifugal method to produce full-specification micro-powder from fine to coarse. Natural sedimentation classification is the most basic diamond micron powder production method, with a simple process and relatively stable product quality.
Overflow classification can be understood as a reverse sedimentation classification method. In an overflow classification container, water enters the lower part of the container from the bottom. As the cross-sectional area of the classification container gradually expands, the upward flow rate of the fluid gradually slows down and finally stabilizes in the upper cylindrical body.
Diamond particles settle against the upward water flow. When the flow rate stabilizes, particles of a certain size will be in a state of suspension, neither rising nor sinking, due to the balance of gravity and the upward buoyant force of the water flow. Fine particles will overflow from the classification container with the water flow, while coarse particles will suspend at different heights in the lower conical part, according to their size, due to the increased fluid speed. By adjusting the flow rate, products of corresponding sizes can be obtained.
Although the production cycle of overflow classification is relatively long and water consumption is high during the production process, it has the advantages of high classification accuracy and lower manual labor requirements compared to other classification methods.
Hydrocyclone classification utilizes the principle of centrifugal sedimentation. Through the high-speed rotation of slurry in a hydrocyclone, the separation of coarse and fine particles is accelerated. This process is widely used for coarse classification and product dewatering in various fields. Its main characteristics are fast speed, simple operation, good repeatability, and continuous feeding. Except for ultrafine particles finer than 2 microns, it is effective for classifying the full range of diamond micron powder, but it has the drawback of poor classification accuracy.
In summary, since each method has its inherent characteristics, in actual production, one can flexibly choose based on specific conditions. It's possible to use one method to classify diamond micron powder products or combine two or more methods for classification.
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