Selection And Use of Grinding Medium for Sanding Mill

Grinding medium is also referred to as grinding beads, the earliest is the use of natural sand (so called sand mill), later developed to glass beads, zirconium silicate, and now basically use zirconia beads, alumina beads and so on. (So now the sand mill is also called the bead mill).

In order to achieve a good grinding effect, the selected grinding medium specifications and materials should be appropriate. The selection of grinding medium refers to three bases: pollution, medium material and diameter, and efficiency.

In the grinding production process, the medium transfers part of the energy by changing the speed to achieve the grinding effect. When the stirring speed is constant, the energy release is related to the amount of grinding medium. When the number of grinding media and stirring speed is certain, it is also related to the density of the medium. A large diameter grinding medium with the same mass can also achieve the same effect. However, there is a point that the number of grinding media of the same quality is reduced, and the efficiency is reduced. In the specific operation, the efficiency of the grinding medium must be considered, including three aspects: the demand of the grinding medium, the consumption of power and the grinding capacity.

The grinding medium has a great influence on the grinding effect and efficiency, in general, the finer the fineness requirement is to use fine beads, and the fineness can be large beads; Small beads can be used for low viscosity, and large beads can be used for high viscosity. In addition, the density of the bead grinding efficiency will be higher (but the grinding chamber wear will be larger, the power requirements will be higher).

The better the roundness, the brighter the surface of the bead on the grinding effect and efficiency will be better. The harder the bead, the more durable it is and the less likely it is to break.

In general, the diameter of the grinding medium should be about 20 times the fineness of the raw material or 1000 times the average fineness of the finished product.

Do not use grinding media in the following cases: it can discolor the product, react chemically with the product, and wear and break the medium will affect the product. Different industries and materials have different requirements for pollution prevention.

If the requirements of the product are very fine and the particles of the raw material are too large, sometimes media with different diameters have to be installed into several sanding machines for series step processing and grinding.

The filling rate of grinding medium is closely related to the grinding efficiency. Filling rate is too high, accelerate equipment wear, high temperature, too low efficiency is not high. The filling rate should be considered comprehensively with the temperature fineness of the slurry. Regarding the filling amount of grinding medium, the material and particle size of the grinding medium should be considered before selection, and the optimal filling amount is 70%-80%; If the material has more pigment, the fineness requirement is not high, and the material is easy to heat, the grinding medium should control the filling amount at 60%-70% in order to improve the energy input and product yield, and improve the grinding rate. The filling rate of the grinding medium is generally 50-80%. The principle is: white or low temperature requirements of the product to add about 55%, dark 70% gradually added.

Beads of the same material, the packing density of large beads and small beads is basically the same, and the difference is not large. Filling amount (kg) = effective grinding space of grinding barrel (L) × specific gravity of grinding medium × filling rate

Specific gravity of common grinding media (unit: Kg/L) : glass beads (1.5), zirconium silicate beads (2.3), 80 zirconium beads (3.2), 95 yttrium stabilized pure zirconium beads (3.6), 95 cerium stabilized pure zirconium beads (4.0)

Example: The total weight of zirconium balls G=3.6*400*0.8=1152 (kg), where 3.6 is the packing density of zirconium balls, 400 is the volume of the grinder, and 0.8 is the filling ratio.