Reactor Kenics mixers

To improve the mixing quality in the tubular reactor, Kenics type in-line static mixer reactor was employed. The in-line static mixers were designed to mix two or more fluids efficiently since an improved treinsport process such as flow division, radial eddying, flow constriction, and shear reversal eliminated the gradients in concentration, velocity and temperature. However, only 70 % conversion was achieved with one Kenics mixer unit. As shown in Table 2, five mixer units were required to achieve the maximum conversion. 

VL = 1 Wj), partial inversion. In the first case, N = 0 corresponds to a CSTR and N to a plug-flow reactor. It is shown that the best chemical conversion is obtained with complete flow inversion. The RTD in a Kenics mixer comprising 8 elements could be represented by this model with N = 3 and complete mixing. Static mixers could be used as chemical reactors for specific applications (reactants having large viscosity differences, polymerizations) but the published data are still very scarce and additional information is required for assessing these possibilities. 

A slit-type interdigital micromixer was used for fast mixing [30] and compared to a tubular reactor and five Kenics mixers connected in series. Details on further components of the micromixer rig were not given, but most likely a capillary reactor was added for efficient heat exchange. 

Fig. 8.11 Yield Yq of desired mono-azo dye from 2-naphthol upon conducting the reaction in a tubular reactor with Kenics mixers for two different viscosities and declining rs. Throughput ratios of A B = 1 3.000. Comparison between measurement and calculation from (16]...

Different types of reactors - a tubular reactor, five combinations of Kenics mixers connected in series, and the microstructured reactor - were compared for the t-Boc protection step [34]. 

Table 2. Production of B0C2-AMP with Kenics in-line static mixer reactor...

The high pressure continuous reactor consists of five Kenics type in-line static mixers, that were connected in series [3]. Each reactor unit has 27 Kenics elements and dimensions of 19 cm tube length and 3.3 mm inner diameter. Acetonylacetone and 1 % NaOH aqueous solution were pumped into the in-line static mixer reactor using two independent HPLC pumps. The in-line static mixer reactors were immersed in a constant temperature controlled oil bath at 200 °C so that the reaction mixture was heated to the reaction temperature. When the reaction was completed, the fluid was cooled down rapidly in a constant temperature cold bath at 0 °C. At the end of the cooling line, a backpressure regulator was placed to allow experiments to be run at 34 bar. 

With this low COV it may be possible to couple the HEV mixer directly to the reactor and not use 3 pipe diameters downstream of the mixer. To shorten the mixing system in this manner and maintain uniformity exceeding 99%, Kenics must guarantee the uniformity because the blending performance has only been published for L/D = 3 downstream of the mixer. 

Figure 10.47. Yield data vs initial molar feed ratio for 3 Bourne Reaction occurring in a 1/4 inch (0.64 cm) Kenics Helical Element Mixer used on a recycle loop on 20 liter semi-batch reactor agitated with a 6BD impeller.

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. 

For the tube reactor only 27% conversion was achieved [34]. A fast flow rate was required due to phase separation and thus, at Re > 2000, about 2 km of tube is needed to have a 5 min residence time, which is impractical. With five Kenics static mixers connected in series a conversion of 97% is achieved. In the microreactor. 

Kenics-type static mixers have been used as inserts in tubular reactors. Compared to an open tube operated at the same pressure drop, the static mixer gives about 40% more heat transfer. Stand-alone mixer reactors of the Koch or Sultzer SMR type have been used as post-reactors and devolatilization preheaters. The polymer flows through the shell side of the SMR and the heat transfer fluid flows inside tubes that have been strategically placed to promote radial mixing of the polymer. One bulk polystyrene process used the SMR as in a recycle loop as the first reactor, but the capital cost is high compared to alternatives such as a boiling CSTR or a proprietary stirred-tube reactor. 

Example 7-3 Liquid-Liquid Contacting—Turbulent Dispersion. A stream from a reactor is be contacted with an immiscible solvent to extract the product. A motionless mixer is planed. After the mixer the two streams will enter a decanter (Table 7-9). The cut size of the decanter is 125 pm, so a goal drop size for the mixer is 500 pm. Choose a Kenics KMS mixer based on past experience. No line size is given. 

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