Static mixers or motionless mixers are fins, obstructions, or channels mounted in pipes, designed to promote mixing as fluid flows through the mixer. Most static mixers use some method of first dividing the flow, then rotating, channeling, or diverting the flow, before recombining it. Other static mixers create additional turbulence to enhance mixing. The power input to the mixing process is a result of pressure loss through the mixer. 

Static mixers serve to put liquid in motion in order to achieve homogeneity of composition and avoid the sedimentation process. They are driven by auxiliary equipment, such as a shaft, speed reducer or electric motor, to sluice the product over the static mixer elements, to provide mixing action. Static mixers function by forcing sediment to flow in one direction and overcome the resistance during a liquid circulation flow in open reservoirs, ditches and canals.  They are also used to intensify physical and chemical processing in liquids, particularly the processes of gas and solid dissolution. Gas dissolution is usually used in sediment / waste water / anaerobic process. The intensified mixing operation is applied in order to lengthen the distance covered by gas bubbles and to prevent smaller bubbles from joining into bigger ones. Direct drive, fast rotating mixers may also be used to prevent surface scum from coming into existence and to destroy any surface scum that has already appeared.

Types of Static Mixers

Static mixers can be classed into one of two wide categories: industrial or laboratory.  Industrial mixers have two modes - batch and continuous - and are designed for regular, heavy duty, production use.  A laboratory static mixer is used to mix, emulsify, homogenize, disintegrate and dissolve samples.

Important Factors in Static Mixer Selection

When determining which of the many available static mixers would be best for a given application, there are two main factors to consider; the material to be processed and the rate at which it must be processed.  If the media is acidic or corrosive, it is best to select a lined or coated static mixer.  Such devices should also be selected in situations the media is a high-purity chemical, being developed for pharmaceutical use, of a specific polymer type, or if the motionless mixer itself will have multi-use applications.  Sanitary static mixers are also available for high purity processing or laboratory work.

The speed at which a mixer can process materials, also known as its flow rate or feed rate, is a rated measurement based on the volume of product inline static mixers can process during given period of time.  If the needed flow rate is known, it is easy to find a static mixer that may operate at the given rate.  When in doubt, contact one of the many static mixer manufacturers for specifics about their product lines.