Powder Mixing in Planetary Mixer
Source: internal company
Planetary mixer is a kind of fixed container batch spiral mixer. It relies on the spiral rotation and revolution in the inverted conical container to make the powder in the container undergo three-dimensional convection, shear and diffusion mixing.
This type of mixer is not only suitable for mixing micro-powders that are easy to aggregate, but also can mix powders with large differences in particle size or bulk density, and can also be used for stirring and mixing high viscosity liquids. There have been many researches on the mixing characteristics of horizontal batch spiral mixers, but there are few researches on planetary mixers.
Figure 1: Planetary Mixer Experimental Device
1.Revolving motor 2. Transmission 3. Cycle 4. Rotating motor 5. Transformer 6. Pulley
1. Mixing Uniformity of Planetary Mixer
Ferrous oxide, a coloring tracer with a bulk density of 400 kg/m and a particle size of 5, was added to calcium carbonate to study the mixing process of planetary mixer. In this experiment, 45 kg calcium carbonate and 2.55 kg ferrous oxide were added, and the spiral stirrer of the mixer mixed at the self-rotation and revolution speeds of 100 rpm and 3 rpm respectively. Mixing until the specified total number of revolutions. Samples are taken in six layers in the mixer.
Due to the rotation of the spiral, the powder rises along the wall surface of the mixer, and at the same time some powder flows out from the center of the mixer. At this time, a gap is generated at the bottom of the mixer, and the upper powder falls due to the action of gravity. On the other hand, due to the revolution of the spiral stirrer, the powder moves in a horizontal circle. This composite movement not only makes the powder convective mixing, but also makes the powder near the spiral blade shear and diffuse mixing.
2. Automatic classification of powder
When the powder moves under the action of external force, it will not only produce mixing effect, but also produce automatic classification. Therefore, when several powders with different particle sizes or bulk densities are mixed, some mixing opportunities cannot be fully mixed due to automatic classification. Due to the revolution and rotation of the spiral stirrer, the planetary mixer makes the powder make forced convection in the mixer, which is not easy to generate automatic classification between the powders. If other types of mixers are used to mix powders with different physical properties, once the powders are fully mixed, if they continue to operate, they cannot continue to maintain this good mixing state, and automatic classification will often occur.