General Principles Of Mixing


Mixing is perhaps the most universal of all processing operations. A glance at our list of applications will confirm this. It is of vital importance in a variety of industries such as food.

Mixing has been defined as the intermingling of two or more dissimilar portions of a material, resulting in the attainment of a desired level of uniformity, either physical or chemical, in the final product. Gases, confined in a container, mix rapidly by natural molecular diffusion. In liquids, however, natural diffusion is usually a slow process. To hasten molecular diffusion within liquids, the mechanical energy from a rotating agitator is utilized. Much of this mechanical energy may be wasted if the wrong kind of agitator is used to accomplish the desired process result.

Mixing applies to all the common states of matter or solids, liquids and gasses. Each form may mix with itself or the others, generating six basic theoretical mixing process versions and more, where all three states may be involved in the mixing process.

The five most common mixing categories by common state include solid to solid dispersion (e.g. pigmentation dispersions), solid-liquid mixing, liquid-gas, and two forms of liquid-liquid mixing, namely mixing of miscible liquids and mixing of immiscible liquids.

Solid-liquid mixing is commonly seen in suspension of solids or dissolving of solids. Dispersion is a key sub category of suspension of solids, where the dispersion of the solids is so fine that settling does not occur, or only after protracted periods of time. Dispersion is a key mixing capability of Jones Industrial Mixers.

The degree of mixing within a system is a function of two variables, namely the magnitude of eddy currents or turbulence formed and the forces tending to dampen this formation. The higher the ratio of applied to dampening forces, the higher is the degree of mixing.

Liquid viscosity affects the flow created by a rotating agitator. Viscosity is the property of a liquid to resist flow through internal forces and molecular attraction. The more viscous a liquid, the greater is the quantity of energy required to produce a desired state of flow. Low viscosity liquids show little resistance to flow and therefore require relatively small amounts of energy per unit volume for a condition of mixing to occur. High viscosity liquids dampen the mechanical energy transmitted from a rotating agitator and require relatively large quantities of power per unit volume to reach a state of flow great enough for adequate mixing to occur.

These guidelines and notes are presented as general guides only and no warranty is implied or provided.