What Are The Factors That Affect The Grinding Fineness Of The Sand Mill
Dec 15, 2022
There are many factors that affect the grinding fineness of the sand mill, mainly from two aspects: external reasons and internal reasons.
1. External reasons include the addition of dispersant, the particle size of raw materials, etc. Here we mainly talk about the influence of dispersant on the grinding fineness.
In the sand mill, the crushing of material particles mainly depends on the collision, extrusion and shearing between the high-speed moving grinding beads to realize the particle size reduction and specific surface area increase of the material particles. In the process of gradually refining the particle size, the particles will reunite under the influence of van der Waals force and electric double layer electrostatic interaction. Therefore, it can be considered that after the particles are ultra-finely crushed to a certain extent, a series of qualitative changes in the physical and chemical properties of the particles will occur, and a reversible process of "crushing⇌agglomeration" will appear. When the speeds of the positive and negative processes are equal, the dynamic balance in the crushing process is reached, and the particle size reaches the limit value. At this time, further prolonging the pulverization time is futile. Because the mechanical force at this time is not enough to deagglomerate the aggregates to further break the particles, it can only be used to maintain the balance of crushing, and may cause more small particle aggregates, so the so-called "reverse grinding" and "returning coarse" phenomenon will appear. To some extent, the proper choice of dispersant is the only effective way to solve the phenomenon of "reverse grinding" and "returning coarse". Dispersants can affect the van der Waals force between particles, the electrostatic force of the electric double layer, the steric repulsion of the solvation film and the adsorption layer.
Therefore, the selection of dispersant in the ultra-fine grinding process is a complex and difficult project. All factors must be considered comprehensively. Only when the dispersant has no effect on the product performance and system can the appropriate dispersant be selected. And its dosage can reduce the soft aggregates between the particles in the ultra-fine grinding slurry, make the particles dispersed and stable in the system, and the grinding fineness of the sand mill can be realized.
2. The internal reason, the structure and technical design of the sand mill itself.
As a kind of high-efficiency and energy-saving ultra-fine grinding equipment, the sand mill has developed rapidly in the past ten years. However, the equipment produced by different manufacturers is different, and the grinding fineness of different types of equipment produced by the same manufacturer is also different.
Let's start with the grinding media today.
Taking the grinding process of paint colorant as an example, the size of the grinding medium determines the number of contact points between the grinding medium and the colorant. The more contact points of the grinding medium with small particle size under the same volume, the higher the grinding efficiency in theory; But on the other hand, when the particle size of the pigment is large in the initial stage of grinding, the impact of the small particle size of the grinding medium is small, and a good grinding effect cannot be achieved; Insufficient, resulting in poorer particle size distribution than small-sized grinding media, and unsatisfactory fineness.
The nano-sand mill produced by Pengyi adopts a centrifugal separation device that can use grinding media above 0.1mm. The better design of the body can better realize the grinding of finer materials in terms of machine performance.
