Colloid mills are rotor-stator mixers that are commonly used to make emulsions and dispersions. It can also be used to make solids in suspension smaller. A high-speed rotor inside the colloid mill forces the fluid through small holes in a stationary stator, resulting in significant mechanical shear. The user can manage the level of shear by changing the size of these holes or gaps. The smaller the final particle size, the stronger the shear is.
Colloid mills are utilized in a variety of industries, including pharmaceutical, food, and chemical processing. It’s ideal for creating small to medium batches of products, which could range from toothpaste to peanut butter.
When equipped with a rough-surfaced rotor and stator, colloid mills perform well with highly viscous goods, and some can even be used to grind fibrous materials. The main drawbacks of a colloid mill are that it is not appropriate for continuous usage, that it needs a lot of energy to run, and that product contamination is a possibility.
Colloidal Mill Operation
The input hopper is used to feed the material into the mill. The fine particle size is lowered by passing it through the tight space between the rotor and stator. A piece of hydraulic shear-producing equipment is a colloid mill.
The purpose of the colloid mill is to minimize the size of suspended droplets. The mill makes it possible for solid particles to be so tiny.
Colloid milling is accomplished by pouring a heavier liquid into the mill’s shearing chamber. After the heavier liquid has been introduced, the lighter material, whether a solid mass or a liquid of varying viscosity, is added to the material to begin the mill.
Homogenizers with a High Pressure
A high-pressure homogenizer works in a slightly different way and employs many forces. The fluid is driven at extremely high pressure via a tiny nozzle, creating cavitation, by exclusive homogenizing cell technology. The fluid passes through an absorption cell as a high-velocity jet stream. The alternating tiny and large orifices of this absorption cell induce turbulence and fluid-on-fluid collision and shear, causing turbulence. All of these forces are programmable, allowing the user to fine-tune them to get the desired outcome.
One of the most popular setups involves applying high pressure to a tank to drive the liquid sample stored therein through a valve or membrane with very fine openings. This creates a lot of shears, a lot of pressure loss, and a lot of cavitation, which all help to homogenize the sample. To aid with homogenization, the high-pressure stream is sometimes directed at a blade, ring, or plate, with which the sample collides at a high speed.
Useful Suggestions for High-Pressure Homogenizers
If the sample contains too many particles or solid materials, high-pressure homogenizers should be avoided since the valves’ openings may become clogged. After each usage, carefully clean the unit to avoid cross-contamination and to clear any debris from the valves.
If one pass of the homogenizer does not give acceptable homogeneity, repeat the process. Some homogenizers feature setups that allow for easy effluent recycling.
The structure of a colloid mill is basic, and it has a tiny footprint compared to a huge area of a homogenizer. The cost of a homogenizer machine is also significantly more than that of a colloid mill. A colloid mill is better for pharma processing, whereas a homogenizer is better for chemical and cosmetic processing.