Line-Blenders and Mixers

But above viscosities of 10 cP a body one size larger than the line size is recommended. 

When long residence time is not needed for chemical reaction or other purposes, small highly powered tank mixers may be suitable, with energy inputs measured in HP/gal rather than HP/1000 gal. They bring together several streams continuously for a short contact time (at most a second or two) and may be used whenever the effluent remains naturally blended for a sufficiently long time, that is, when a true solution is formed or a stable emulsion-like mixture. When it is essential that the mixing be immediate each stream will 

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Various types of mixers can be used in-line blenders, baffled continuous stined tanks with propellor iuqrellers, tanks with air spargers (pneumatic coagulators) and baffled tanks with flat blade slatted paddle mixers have all been used. The latter is commonly foimd in the water treatment industry and Peavy et al [1985] give some design rules for this version. 

Processing line, upstream Refers to material movement and auxiliary equipment (dryer, mixer/blender, storage bins, etc.) that exist prior to plastic entering the main fabricating machine such as the extruder. 

Figure 10.14. Some kinds of in-line mixers and blenders, (a) Mixing and blending with a recirculating pump, (b) Injector mixer with a helical baffle, (c) Several perforated plates (orifices) supported on a rod. (d) Several perforated plates flanged in. (e) Hellical mixing elements with alternating directions (Kenics Corp.). (f) Showing progressive striations of the flow channels with Kenics mixing elements.

Figure 10.15. Some mixers and blenders for powders and pastes, (a) Ribbon blender for powders, (b) Flow pattern in a double cone blender rotating on a horizontal axis, (c) Twin shell (Vee-type) agglomerate breaking and liquid injection are shown on the broken line, (d) Twin rotor available with jacket and hollow screws for heat transfer, (e) Batch muller. (f) Twin mullers operated continuously, (g) Double-arm mixer and kneader (Baker-Perkins Inc.), (h) Some types of blades for the double-arm kneader (Baker—Perkins Irtc.).

Mixing Mechanisms Consider a calendering process for manufacturing PVC floor covering. The line consists of a ribbon-type blender in which the PVC is dry-blended, and an internal mixer that feeds a SSE equipped with a static mixer, feeding the first nip of the calender. What types of mixing mechanisms does the polymer experience Specify the locations at which each mechanism occurs. 

Other low shear mixers use double or slanted cone and V-shaped vessels. Fig. 7.25 depicts schematically these always batch operating blenders which rotate about a horizontal axis. The lines and arrows in the sketches try to explain the particle paths that cause mixing. In Fig. 7.26 photographs of typical equipment are presented. 

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). 

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