Pipeline Mixers

Figure 10.34. Dimensionless drop size correlation for a Kenics HEM pipeline mixer.

For a conservative pipeline mixer scale-up, use the following procedure ... 

The procedure outlined above is conservative because it is thought to be one that will always give equal or higher yield of the desired reaction(s) in the plant pipeline mixer reactors than in the laboratory pipeline mixer reactors. 

There are other less stringent scale-up procedures mentioned in the literature (Baldyga and Bourne, 1999 Hearn, 1995) however, their validity have not been determined for practical applications in scaling from a typical laboratory size pipeline mixer reactor (perhaps 1/8in. 0.3cm to 3/16in. 0.5cm ) to plant size reactors (perhaps 1/2 1.25 cm in. to 2 in. 5 cm ). 

Pipeline Mixers used as Reactors for Fast C/C Reactions. Taylor (1996) and colleagues (1998) conducted a study to determine scale-up procedures for fast C/C reactions in pipeline mixers. They used the fourth Bourne reaction, which is the acid catalyzed hydrolysis of dimethoxypropane (DMP) to acetone and methanol. This is an extremely rapid reaction when catalyzed by HCl. The competitive reaction scheme, which is a unique one, is one in which NaOH reacts practically instantaneously with the HCl to remove the catalyst for the hydrolysis reaction. A water/ethanol solution of NaOH and DMP was fed as a main stream to a Kenics helical element mixer and an aqueous side stream containing slightly greater (abour 5% greater) than equimolar amount of NaOH was fed as the side stream. The product was analyzed by GC for methanol and acetone. For extremely rapid mixing, essentially no hydrolysis occurred however, for slow mixing, essentially all the DMP is hydrolyzed because acidic conditions cause very rapid hydrolysis of the DMP. 

R.A. Taylor, Scale-Up Methods for Fast Competitive Chemical Reactions in Pipeline Mixers, MS Thesis, University of Arkansas, Fayetteville, 1998. 

FIG. 14.12 (a) Greerco A" two-stage sanitary tandem shear pipeline mixer, (b) Exploded... 

Pipeline mixers narrow residence times and drop size distributions, low holdup. 

Pipeline mixers 1.2 kW s/L. Upstream use at least 3 pipe diameters of straight pipe. 

Figure 11.8 Sketches of some common liquid-liquid contactor reactor designs. HP, heavy phase LP, light phase, (a) Mixer-settler, (b) horizontal pipeline mixer (static mixer), and (c) air agitated contactor.

Chemineer Greerco offers a different rotor-stator geometry. In this case, as shown in Figure S-4a and b, the rotor is an axial impeller that pushes the fluid axially through holes bored into the stator. The rotating action of the impeller, however, creates some tangential shear flow inside the stator. There is a two-stage version called the tandem shear pipeline mixer. This consists of a primary disperser... 

Mixing equipment vessels, rotor-stators, and pipeline mixers... 

Design requirements robust and flexible (typically stirred tanks) versus tight and specific (pipeline mixers and other speciahzed equipment)... 

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