Mixers Sulzer

Static mixing of gas—Hquid systems can provide good interphase contacting for mass transfer and heat transfer. Specific interfacial area for the SMV (Koch/Sulzer) mixer is related to gas velocity and gas holdup ( ) by the following ... 

Heat transfer in static mixers is intensified by turbulence causing inserts. For the Kenics mixer, the heat-transfer coefficient b is two to three times greater, whereas for Sulzer mixers it is five times greater, and for polymer appHcations it is 15 times greater than the coefficient for low viscosity flow in an open pipe. The heat-transfer coefficient is expressed in the form of Nusselt number Nu = hD /k as a function of system properties and flow conditions. 

Despite the wide use of the striation thickness concept in the early commercial literature, the CoV is now the most widely used mixing index. The following correlations are valid for viscosity ratios 0.01 < nBlnA < 100, feeding into the center of the pipe and with CoV measured 2dp downstream for Sulzer mixers, 3dp downstream for Kenics mixer. 

For instance, with the Hi-Mixer (161), 6Q/6 = 4n. A factor of 5 is easy to obtain for m with respect to an empty tube, at the expense of a corresponding increase in pressure-drop. A comparison between the existing types of static mixers (162) shows that most of them have an equivalent effectiveness. The case of Sulzer-Mixers has been especially studied (163), including use with gases (164). 

The evaluation of diazotization reactions [41], which were carried out in Kenics and Sulzer SMXL mixers, provide a possible access to this parameter determination. For small throughputs and high viscosities the yield of the desired product was determined by micro-mixing. The power dissipation of 85-90% in both mixers indicated, that the engulfment model for micro-mixing prevailed. Faster micro- and meso-mixing was achieved in the Sulzer mixers, because larger pressure drops were also present in them, see Fig. 8.11 and 8.12. 

Fig. 8.12 Yield Yq of desired mono-azo dye from 2-naphthol upon conducting the reaction in a tubular reactor with Sulzer mixers SMXL for two different viscosities and constant rs. Throughput ratios of A B = 1 3000. Comparison between measurement and calculation from [16]...

Limiting ourselves to Sulzer technology, two interesting mixer types emerge. The Sulzer Mixer Reactor (SMR) is ideal for exothermal reactions, but is, however, only applicable for viscous fluids, e.g. polymers. The Sulzer SMV mixer on the other hand can be applied for mixtures in which gas is the continuous phase. For this reason jacketed cooling is of no use because the heat transfer coefficient for a gas is rather limited. An important remark must be made on this point only gas-liquid mixtures with a G/L ratio up to 10 can be handled with the SMV mixer.14 Therefore, when dealing with the model system, solutions must be found to decrease this ratio within the reaction system. 

Van der Meer and Hoogendoorn [175] used Sulzer mixers for the heating of silicon oil (curves g and h). Each mixer element consists of several layers of corrugated sheet. An increase in heat transfer coefficient of about 400 percent is reported. 

In the case of uniformly heated tubes, very high heat transfer coefficients have been obtained with the SMV Sulzer mixer (Fig. 11.27, curves i and j). Comparable heat transfer enhancement is also obtained with Kenics static mixers. 

The relationship between the variation coeflicient and mixer length is flow ratio dependent, as illustrated by data published for Sulzer mixers this apparently not being the case for the other two indices There is also the disadvantage, shared by most other variance based indices, of a dependence on sample size which can lead to difficulty in comparing data from different sources. 

Figure 12.7 Mixing rate chart for Sulzer mixers in terms of variation coefficient (a/C) and dimensionless mixer iength (LJDJi ...

Sulzer mixers in terms of the Newton number and other dimensionless groups defined in terms of hydraulic diameter (for the SMV element D,/D, %4.2)... 

The turbulent flow characteristics of the static mixer are less well documented than those for laminar flow, probably because of the more recent emphasis on turbulent applications and the background of development for laminar flow applications. Turbulent mixing has been modelled in terms of eddy size for the Sulzer mixer. Measurements of mass transfer have been made and data are available for drop size in liquid-liquid dispersions for Kenics - ", Sulzer and Lightnin mixers. 

For the Sulzer mixer a correlation in terms of the Weber number has been developed ... 

In the precipitation process, the API/polymer solution and the antisolvent need to be mixed efficiently to ensure an instantaneous supersaturation/precipitation of MBP maintaining the homogeneous distribution of API and polymer from the solution. The mixing of the two phases can be performed by several techniques. The key features of different mixing techniques are summarized in Table 11.2. Techniques other than those listed here, i.e., continuous in-line mixer (Sulzer Mixer), could also be applied but are considered outside the scope of this discussion. 

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