Emulsification is defined as the production of an apparently homogeneous liquid from two or more immiscible liquids. In an emulsion one of the liquids is generally dispersed in the other in the form of small droplets. Emulsions are relatively stable. That is the liquids will not separate on standing for a reasonable amount of time. What time is reasonable is determined by the nature and purpose of the emulsified product. Emulsions are often produced by high shear mixing device that impart a high level of turbulent energy to the system. The energy appears as turbulence which tears apart suspended drops to produce droplets small enough to remain entrained and to resist coalescence. However, emulsification operations can be aided by “emulsifying agents,” often surfactants, whose chemical properties enhance drop stability.
Vessel Design Considerations
These applications almost always require a vertical round vessel. Exceptions may be acceptable when the viscosity is relatively high, but these are unusual. The vessel should be selected so that the static height of the greater component is no higher than the vessel diameter. Angle offset mounting can be used, but we normally expect to see baffles installed in the vessel.
Many emulsions in particular are very viscous. These applications often require scraped wall agitation in conjunction with a second high speed disperser mixer in the same vessel. Needless to say, these vessels are always round.