A static mixer is a precision engineered device for the continuous mixing of fluid materials, without moving components. Normally the fluids to be mixed are liquid, but static mixers can also be used to mix gas streams, disperse gas into liquid or blend immiscible liquids. The energy needed for mixing comes from a loss in pressure as fluids flow through the static mixer. One design of static mixer is the plate-type mixer and another common device type consists of mixer elements contained in a cylindrical (tube) or squared housing. Mixer size can vary from about 6 mm to 6 meters diameter. Typical construction materials for static mixer components include

stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...

polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins and ...

Teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemou ...

PVDF Polyvinylidene fluoride or polyvinylidene difluoride (PVDF) is a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride. PVDF is a specialty plastic used in applications requiring the highest pur ...

, PVC,

CPVC Chlorinated polyvinyl chloride (CPVC) is a thermoplastic produced by chlorination of polyvinyl chloride (PVC) resin. CPVC is significantly more flexible than PVC, and can also withstand higher temperatures. Uses include hot and cold water deli ...

and

polyacetal Polyoxymethylene (POM), also known as acetal, polyacetal, and polyformaldehyde, is an engineering thermoplastic used in precision parts requiring high stiffness, low friction, and excellent dimensional stability. As with many other synthetic pol ...

. The latest designs involve static mixing elements made of glass-lined steel.

Design

Plate type

Westfall 2800 Static Mixer with multiple injection ports

In the plate type design mixing is accomplished through intense

turbulence In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...

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 Plastics are a wide range of synthetic polymers, synthetic or semi-synthetic materials that use polymers as a main ingredient. Their Plasticity (physics), plasticity makes it possible for plastics to be Injection moulding, moulded, Extrusion, e ...

. 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

helical Helical may refer to: * Helix, the mathematical concept for the shape * Helical engine, a proposed spacecraft propulsion drive * Helical spring, a coilspring * Helical plc, a British property company, once a maker of steel bar stock * Helicoil A t ...

elements can simultaneously produce patterns of flow division and radial mixing: * Flow division: In

laminar flow In fluid dynamics, laminar flow is characterized by fluid particles following smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral mi ...

, 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 Striations means a series of ridges, furrows or linear marks, and is used in several ways: * Glacial striation * Striation (fatigue), in material * Striation (geology), a ''striation'' as a result of a geological fault * Striation Valley, in Anta ...

s 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 Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also coll ...

) and sealants (see

Resin casting Resin casting is a method of plastic casting where a mold is filled with a liquid synthetic resin, which then hardens. It is primarily used for small-scale production like industrial prototypes and dentistry. It can be done by amateur hobbyists wit ...

). Other applications include

wastewater treatment Wastewater treatment is a process used to remove contaminants from wastewater and convert it into an effluent that can be returned to the water cycle. Once returned to the water cycle, the effluent creates an acceptable impact on the environme ...

and chemical processing. Static mixers can be used in the refinery and oil and gas markets as well, for example in

bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...

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. 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 NOV Inc., formerly National Oilwell Varco, is an American multinational corporation based in Houston, Texas. It is a worldwide provider of equipment and components used in oil and gas drilling and production operations, oilfield services, and ...

. The plate type static mixer patent was issued on November 24, 1998, to Robert W. Glanville of Westfall Manufacturing.

References