Static Mixers -process engineers need to know

For the past week or so I had been studying Static Mixers, which also made me think that I should be sharing what I have read and understood. The initial part which is a word description has been provided in the following text. However, the rough application guide for various commercial static mixer models and the pressure drop for the more popular static mixer models from manufacturers of repute such as Chemineer and Sulzer Chemtech could not be provided in the text. The Excel workbook provided as an attachment repeats the text description provided below in addition to providing the rough application guide as a table and the pressure drop ratios for the popular commercial static mixer models. The Excel workbook also lists the leading manufacturers of static mixers and provides direct hyperlinks to their catalogs.

Static or motionless mixers use stationary-shaped elements inside pipes or conduits to divide, divert, twist, and recombine flowing material. The dividing, stretching, and recombining processes lead to thinner and thinner striations in viscous materials to achieve uniformity. Molten polymers usually are in laminar flow and have no radial exchange when flowing. Thus temperature gradients can form and be propagated. Heating and cooling of these materials through the wall is very difficult because of the residence time distribution associated with the laminar velocity profile. The material at the center moves much faster than the material at the wall and has less contact time because of the poor conductive heat transfer at the center. These devices would reduce radial thermal gradients that occur in polymer processing.

One of the first commercial units was the Kenics device. In the Kenics mixer, a set of twisted elements with left- and right-hand twists caused the material to move from the wall to the center and from the center to the wall. After traveling through a number of these elements, the fluid is homogenized concerning age, composition, and temperature. These devices were called motionless mixers or static mixers because the mixer did not move, although the liquid did. The term static mixer was originally copyrighted by Kenics Corporation, but the term is now commonly used for all such in-line motionless mixers.

Over the years a large number of companies have produced static mixers all based on the principle of moving the streams radially by a series of metal baffles. These baffles may consist of twists of metal, corrugated sheets, parallel bars, small-diameter passages, or tabs sticking out from the wall. They are essentially plug-flow devices with some small degree of back mixing, depending on the exact design.

Today static mixers are established in many different market segments and are used for a wide range of different applications. A common application for static mixers includes mixing two component adhesives (e.g. epoxy) and sealants. Other applications include wastewater treatment and chemical processing. Static mixers can also be used in the refinery and oil & gas market for example for the desalting of crude oil. In polymer production, static mixers can be used for the homogenization of polymer melts or the uniform mixing of liquid additives to the molten polymer.

I would appreciate comments from the knowledgeable forum members for any further insight on static mixers, their applications, and any other information that could prove useful to the chemical engineering community.

The spreadsheet can be downloaded here:

http://www.cheresour…s-need-to-know/

Regards,
Ankur

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