Line mixers

The natural process of bringing particles and polyelectrolytes together by Brownian motion, ie, perikinetic flocculation, often is assisted by orthokinetic flocculation which increases particle coUisions through the motion of the fluid and velocity gradients in the flow. This is the idea behind the use of in-line mixers or paddle-type flocculators in front of some separation equipment like gravity clarifiers. The rate of flocculation in clarifiers is also increased by recycling the floes to increase the rate of particle—particle coUisions through the increase in soUds concentration. 

Line mixer Cocurrent Differential Liquid or gas Absorption, stripping... 

Agitated Line Mixer See Fig. 18-32. This device, which combines the features of orifice mixers and agitators, is used extensively in treating petroleum and vegetable oils. It is available in sizes to fit V2- to 10-in pipe. The device of Fig. 18-33, with two impellers in separate stages, is available in sizes to fit 4- to 20-in pipe. 

FIG. 23-25 Typ es of industrial gas/Hqiiid reactors, (a) Tray tower, (h) Packed, counter current, (c) Packed, parallel current, (d) Falling liquid film, (e) Spray tower, if) Bubble tower, (g) Venturi mixer, h) Static in line mixer, ( ) Tubular flow, (j) Stirred tank, (A,) Centrifugal pump, (/) Two-phase flow in horizontal tubes. 

Wiped film stills in place of continuous still pots —Centrifugal extractors in place of extraction columns —Flash dryers in place of tray dryers —Continuous reactors in place of batch —Plug flow reactors in place of CFSTRs —Continuous in-line mixers in place of mixing vessels... 

Finally, mixing can be induced by physically splicing the fluid into smaller units and re-distributing them. In-line mixers rely primarily on this mechanism, which is shown in Figure 7.4. 

Sulfuric acid, formaldehyde, and hydrogen cyanide are pumped into a glass-lined mixer (mixer 1, Ml, of Fig. 13). Particular care is exercised so that the three charge operations are carried out in the order indicated above, to ensure the stability of the mixture at all times. In a separate segment of the plant, ethylenediamine (EDA) and dilute sodium hydroxide are charged and mixed in mixer 3 (M3 in Fig. 13). The solutions from mixer 1 and mixer 3 are pumped to the reactor (REACTOR, Rl, in Fig. 13). When the reaction is complete, the reaction mixture is tested for traces of hydrogen cyanide. Dilute solution of formaldehyde is prepared in mixture 2 and is added to the reaction mbrture, if there is any HCN present. 

Continuous in-line mixers in place of mixing vessels... 

Soluble liquids Mixing Agitated vessel, in-line mixer... 

In-line mixers manufactured by, for example, Kenics, Lightning, and Sulzer are also applicable for continuous small-scale testing of a solvent extraction process, and 1 inch diameter models are available. This mixer system can be used either horizontally or vertically. However, few data are available for this type of contactor, although they would appear to offer many possibilities, not only for liquid-liquid systems, but also for use in... 

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.

Capacities of line mixers such as those of Figure 10.13 and of static mixers such as those of Figure 10.14 are stated in manufacturers catalogs. A procedure for estimating mixing efficiencies from basic correlations is illustrated by Laddha and Degaleesan (1978, p. 424). 

Experts predict a trend from stirred-vessel mixing to the use of continuous mixing, e.g. by in-line mixers [1]. This again provides a chance for many microstructured mixers. 

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