Mixing dynamic/static mixers

Mixing operations can be performed in a number of static and dynamic devices, e. g., in static mixers, kneaders, or twin screw extruders [1]- Extruders belong to the group of continuous dynamic mixers. 

It was shown that the efficiency for radial mixing depends on the gas phase as well (O. Eichstadt, Continuous Mixing of Fine Particles within Fluid Dynamic Vertical Tube Mixers, Dissertation, in German, ETH-Zurich, 1997). At best they operate with low volume concentration and for particles between 20 and 200 pm. Static mixers have been used for very abrasive free-flow materials such as silicon carbide. Since any rotating equipment is avoided inside static mixers, abrasion is limited. As will be shown below, mixture quality is dependent on feed consistency and residence time within the static mixer. Since the latter is very short in static mixers (seconds or fractions of a second), short-time feeding precision has to be very high to achieve high-quality mix. 

Solvent Mixing. During gradient operation, the HPLC solvents that comprise the mobile phase must be mixed adequately, most commonly with either a static or dynamic mixer. Static mixers rely on laminar-flow dynamics, whereas dynamic mixers use magnetic stirrers. Solvent viscosity affects mixing characteristics inadequate mixing is detected by many UV detectors and may be expressed as an unstable baseline. 

In the continuous process, most mixing operations are achieved with static mixers only highly viscous or difficult materials are mixed with dynamic mixers. 

Add-on s — Barmag add-on torpedo, Staro-mix , Maddox, Cavity Transfer Mixer (CTM), Twente Mixing Ring (TMR), the Extensional Flow Mixer (EFM), Dynamic Melt Mixer (DMX), static or motionless mixers (SM) from Koch, Ross, or Kenics, etc. 

Preparation of a concentrated emulsion. This stage consisted in mixing the heavy crude oil and a fresh-water surfactant solution, first in static mixers, then in a dynamic in-line turbine-type blender. The oil/water proportion was quite high (about 85% of heavy erode oil). Consequently, mixing was carried out very near the inversion A /B" branch. Inversion to W/O was delayed by the use of a relatively high surfactant concentration (the new one from the surfactant solution plus the remaining one from the primary emulsion). 

In typical extrusion operations, mixing devices are used in the screws. Many dynamic mixers, such as those included in Fig. 3-7 and in Chapter 2, are used to improve screw performance. Static mixers are sometimes inserted at the screw end (Fig. 3-9) or at the end of the barrel. There are also mixing... 

One more use of a breaker plate is as a static mixer. Mixing is necessary to produce the homogeneity required in the melt. Several designs allow the breaker plate to serve its conventional functions while also creating flow dynamics that improve the level of mixing in the melt. These devices can be stacked in a series to create various flow fields for different mixing applications. 

Mixing devices are generally divided into two main categories static mixers and mixing elements (also known as dynamic mixers). The use of mixing elements on the screw is far more popular than the use of static mixers. 

Dynamic mixers may be used when the static mixers do not give good enough and fast mixing. The operator must be careful because the intensive mixing may raise the temperature of the mix, thus reducing the pot life. 

As the term implies, unlike dynamic mixers described in previous chapters which turn with the screw, static mixers have no moving parts. These mixers are not specific to plastics extrusion but are versatile chemical engineering devices used for pipeline fluid mixing over a wide viscosity range. They can also be used for chemical reactions at very high flow rates. 

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