When do you need to use a disperser instead of a mixer? Difference between disperser and mixer

What is the difference between a disperser and a mixer?

Both dispersers and mixers will mix. Mixers are sometimes compared to pumps. Pump performance is usually measured in horsepower required for its gallon-per-minute discharge capacity.

A disperser is a high-power, low-capacity pump. A disperser is an inefficient mixer given the much higher horsepower it requires per gallon. A mixer is a low power, high capacity pump.

It is an effective mixer. Typical dispersing applications (such as dispersing pigments to make paint) require approximately 1 horsepower per 10 gallons, while mixer applications (such as diluting pigment dispersions with solvents) require approximately 1 horsepower per 100 gallons. While a mixer is a more efficient pump, it cannot generate enough shear to disperse most solids into a liquid. The operating speed of the medium shear disperser is about one-half of the normal blade speed of the high shear disperser, and when some shear force is required, the medium shear disperser is sometimes used instead of the mixer. Typically, the discs have larger teeth to facilitate better pumping and require about one-third the horsepower of a high-shear disperser, but still three times as much as a mixer (Fig. 46.2).

When should I use a disperser instead of a mixer?

The disperser will generate the shear force needed to quickly break down the powder in the liquid. This chunking process is called scatter. A blender is an effective mixer, but it usually cannot generate enough shear to disperse powders, no matter how long they are mixed. This is because the forces holding the clumps (lumps) together are stronger than the mixer is trying to pull them apart. Mixers do a good job of keeping dispersed (shear) mixtures in suspension, but they generally do not disperse (shear) mixtures.