Distributive mixers

Fig. 28. Flow patterns with (a) clustered and (b) distributed mixers.

Knob mixers work well to eliminate fine striations in color uniformity and thermal gradients. Since knob mixers are primarily distributive mixers, they are not suited for mitigating solid polymer fragments from an incomplete melting process. 

Figure 8.27 Schematic of a gear-type distributive mixer (courtesy of Jeff A. Myers of...

Figure4.n Image of visualized flow streams in a distributive mixer. The fluorescence of a buffered solution of quinidine hydrochloride (20 pM) in 2 M KCI (pH 9.4) quenched with Kl solution was investigated [70] (by courtesy of RSC).

There are no standard engineering classification methods for mixing equipment, and often, quite different types of mixers can fulfill the same mixing task. Nevertheless, we can subdivide mixers used in processing into three broad categories particulate solids mixers, laminar distributive mixers, and laminar dispersive mixers. This classification, on the basis of application, is supported by the nature of the primary mixing mechanism taking place in them. 

The modern technology often requires that TSE performs a series of different functions. Owing to limitation of L/D, even these universal machines may profit from additional, external, either dispersive or distributive mixers. These devices are discussed in the following parts. 

Measurement of the circulation time in the mixer was carried out to characterize the distributive mixing. The results indicated that void region shortens circulation time. The circulation time of R-R screw rotor is shorter than that of double-flighted rotor. The shorter circulation time represents a good distributive mixer. 

In starvation effects on the mixing, 0.5 fill factor makes the best distributive mixer. 

P. Gramann, C. Rauwendaal, B. Davis, and T. Osswald, A New Dispersive and Distributive Mixer for the Compounding of Highly Viscous Materiais, 57 SPE ANTEC, 162-166... 

Based on the important characteristics of mixers we can compile the various distributive mixers and list how they perform with respect to different criteria this is shown in Tabie 8.4. 

Splitting and reorientation is critical to achieving efficient distributive mixing, because mixing can improve exponentially by splitting and reorientation. Distributive mixers can be divided into some main groups cavity mixers, pin mixers, slotted flight mixers, variable channel depth mixers, and variable channel width mixers. 

Copredpitation Batch mode vs. continuous mode Flow rate Droplet size distribution Mixer design (shear and energy, e.g., stir bar, vortex, propeller, homogenizer, rotor-stator) Solvent to antisolvent ratio Temperature Processing times (scale dependent)... 

A further alternative is the cavity transfer distributive mixer, which comprises a rotor with hemispherical depressions located within a closefitting stator, also configured with hemispheres. Polymer melt continuously transfers between rotor and stator cavities, and experiences substantially increased shear strain, resulting in increased mixing. 

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