Definition
The high-shear sand mill is a mechanical process equipment for wet ultra-fine grinding and dispersion. It crushes, grinds and disperses solid particles in the liquid phase medium through mechanical force, and finally obtains a slurry or suspension with uniform particle size distribution and fineness of micron or even nano levels. The equipment has a wide range of applications in many non-medical fields such as coatings, inks, new energy, ceramic glazes and chemicals.
Principle
The core working principle of a high-shear sander is based on the combination of energy input and media movement. The equipment is mainly composed of a grinding chamber, a high-speed rotating dispersion disc or rotor, and a filled grinding medium (such as zirconia beads, glass beads). When working, the pre-mixed slurry is pumped into the grinding chamber, and the high-speed rotating rotor generates strong shear force and turbulence, driving the grinding medium to move violently. The particulate material is effectively crushed and dispersed by collision, extrusion and shear between the grinding medium and between the medium and the inner wall of the chamber. The whole process can be regarded as the process of converting mechanical energy into surface energy, and its core energy transfer relationship can be simplified as follows:
E = k ∫ τ γ̇ dt
where E represents the mechanical energy of the input system, k is the coefficient related to the system, τ is the shear stress, γ̇ is the shear rate, and t is the grinding time. This formula qualitatively describes the association between energy input and dispersion effects.
Measurement and evaluation methods
The measurement of the process effect of the high-shear sand mill mainly revolves around the performance index of the final slurry. Particle size distribution is the core evaluation parameter, which is usually measured by laser diffraction or dynamic light scattering method, and the fineness and distribution width are characterized by characteristic particle sizes such as D50 and D90. The stability of the slurry can be assessed by measuring the zeta potential or by observing the resting delamination time. In addition, viscosity changes, solids content, and color or gloss (for pigment applications) are also common auxiliary indicators. These measurements are performed under specified conditions according to relevant industry standards or international standards (e.g., ISO 1524, ASTM D1210) to ensure comparability of results.
Influencing factors
The grinding effect of a high-shear sand mill is affected by a combination of factors. In terms of process parameters, the linear speed of the rotor directly determines the size of the shear force; The residence time or cycle number of the material affects the cumulative grinding energy input. The material, particle size and filling rate of the grinding medium are related to the collision frequency and energy transfer efficiency. In terms of material characteristics, the hardness of the original particles, the initial viscosity and solids content of the slurry, and the selection and dosage of dispersants can significantly affect the grinding kinetics and final fineness. Equipment structural factors such as the geometry of the grinding chamber, the efficiency of the cooling system (for controlling the process temperature), and the design of the gap between the rotor and the stator also have a direct impact on grinding efficiency and product stability.
Applications
High-shear sanders are suitable for many industrial applications where the fine dispersion of solid particles in liquids is required. In the coatings and inks industry, it is used to grind pigment particles to the desired fineness to improve the coloration, gloss, and stability of products. In the field of new energy, such as the preparation of lithium-ion battery slurry, it is used to uniformly disperse active substances, conductive agents and binders. In the ceramic industry, it is used to grind glazes to achieve a smooth finish. In addition, it also plays a key role in chemical fields such as dyes, pesticide preparations, nanomaterial synthesis and high-end filler treatment.
Equipment selection considerations
Choosing the right high-shear sand mill is a systematic project that takes into account both process goals and equipment characteristics. First, it is necessary to clarify the target particle size, capacity requirements and material characteristics (such as corrosiveness and viscosity) of the product. Based on these requirements, approximate specifications of the equipment, such as the volume of the grinding chamber and the power range of the motor, can be determined. The choice of abrasive media material (e.g., zirconia, steel, ceramic) should take into account hardness, density, and chemical compatibility. The structural design of the equipment, especially the ease of cleaning, sealing reliability and temperature control capabilities, is crucial to ensure stable product quality and production continuity. In addition, the scalability of the equipment (from pilot to mass production), energy consumption levels, and ease of maintenance are also factors to consider in long-term operation.