A static mixer is a device for the continuous mixing of fluid materials, without moving components.
Design
Plate type
In the plate type design mixing is accomplished through intense
turbulence in the flow.
Housed-elements design
In the housed-elements design the static mixer elements consist of a series of baffles made of metal or a variety of
plastics. Similarly, the mixer housing can be made of metal or plastic. The housed-elements design incorporates a method for delivering two streams of fluids into the static mixer. As the streams move through the mixer, the non-moving elements continuously blend the materials. Complete mixing depends on many variables including the fluids' properties, tube inner diameter, number of elements and their design. The housed-elements mixer's fixed, typically
Helix elements can simultaneously produce patterns of flow division and radial mixing:
-
Flow division: In laminar flow, a processed material divides at the leading edge of each element of the mixer and follows the channels created by the element shape. At each succeeding element, the two channels are further divided, resulting in an exponential increase in stratification. The number of striation produced is 2n where 'n' is the number of elements in the mixer.
-
Radial mixing: In either turbulent flow or laminar flow, rotational circulation of a processed material around its own hydraulic center in each channel of the mixer causes radial mixing of the material. Processed material is intermixed to reduce or eliminate radial gradients in temperature, velocity and material composition.
Applications
A common application is mixing nozzles for two-component adhesives (e.g.,
epoxy) and sealants (see
Resin casting). Other applications include
Sewage treatment,
Flow chemistry and chemical processing.
[Bor, Thomas P., "The Static Mixer as a Chemical Reactor", British Chemical Engineering, Vol. 16, No. 7, 1971.] Static mixers can be used in the refinery and oil and gas markets as well, for example in
bitumen processing
or for desalting crude oil. In polymer production, static mixers can be used to facilitate polymerization reactions or for the admixing of liquid additives.
History
The static mixer traces its origins to an invention for a mixing device filed on Nov. 29, 1965 by the Arthur D. Little Company.
[C. D. Armeniades, et al., Mixing Device issued November 29, 1965] This device was the housed-elements type and was licensed to the Kenics Corporation and marketed as the Kenics Motionless Mixer.
Today, the Kenics brand is owned by National Oilwell Varco. The plate type static mixer patent was issued on November 24, 1998, to Robert W. Glanville of Westfall Manufacturing.
See also
