Static mixer, efficiency

Wetox uses a single-reactor vessel that is baffled to simulate multiple stages. The design allows for higher destmction efficiency at lower power input and reduced temperature. Its commercial use has been limited to one faciHty in Canada for treatment of a complex industrial waste stream. Kenox Corp. (North York, Ontario, Canada) has developed a wet oxidation reactor design (28). The system operates at 4.1—4.7 MPa (600 to 680 psi) with air, using a static mixer to achieve good dispersion of Hquid and air bubbles. 

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. 

In some multiphase reactors, stirring with an impeller or the flow pattern caused by gravity will control the interfacial area. By suitably designing and positioning propellers and reactant injection orifices or by using static mixers, it is possible to provide very efficient breakup of hquids into drops and bubbles. A factor of two decrease in drop or bubble size means a factor of four increase in interfacial area. 

Construction of a plexiglass scale model for cold flow studies typically occurs after completion of the CFD analysis. Smoke entrained in an air stream is used to empirically confirm the SCR design. Tuning efficiencies of the guide vanes and mixing ability of the static mixers are some of the design qualities confirmed by the cold low model. Figure 17.15 is a picture of an actual model used for commercial scale-up. 

To address these problems, Phoenix has manufactured bromonitromethane using continuous processing technology in a plant that was engineered to fit the chemistry. The bromination was carried out in low-volume static mixer tubes, allowing efficient heat transfer and accurate process control. 

The fact that dissolved ozone is produced brings a very important advantage to subsequent ozone applications mass transfer from the gas to liquid phase is not required. Efficient mixing (e. g. with static mixers) of the ozone-rich pure water stream with the (waste-)water stream to be treated, though, is required. During this in-situ ozone production, the liquid ozone concentration (cL) can easily reach the solubility level (cr ), depending on the pressure (P) and temperature (T) in the cell. Oversaturation of the feed-water will immediately occur, when the pressure drops. Due to this potential degassing, vent ozone gas destruction is also required for this system. 

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). 

The extruder is used since it mixes, melts, and degases the polymer. However, as said in the previous paragraph, from an exergetic point of view, it is not an efficient apparatus, since it dissipates mechanical work into heat by frictional forces. A possible alternative to the extruder could therefore be a separate degasser, a static mixer, or a gear pump to push the polymer melt through the mixer and perforated plate (Figure 11.6). 

From an efficiency point of view, the new setup is advantageous. As the pressure drop across the static mixer is approximately 25 MPa (for diameter 0.5 m ... 

It was shown that the efficiency for radial mixing depends on the gas phase as well (O. Eichstadt, Continuous Mixing of Fine Particles within Fluid Dynamic Vertical Tube Mixers, Dissertation, in German, ETH-Zurich, 1997). At best they operate with low volume concentration and for particles between 20 and 200 pm. Static mixers have been used for very abrasive free-flow materials such as silicon carbide. Since any rotating equipment is avoided inside static mixers, abrasion is limited. As will be shown below, mixture quality is dependent on feed consistency and residence time within the static mixer. Since the latter is very short in static mixers (seconds or fractions of a second), short-time feeding precision has to be very high to achieve high-quality mix. 

Cost for reactor 50,000 (50-gal reactor) and of reactants and products is critical reverse quenches tight temperature controls efficient mixing of heterogeneous streams localization of catalysts and physical effects Under 1000 for static mixer for pilot... 

Static in-line mixers were developed for the intimate mixing of many mixtures, from solutions to heterogeneous mixtures (such as two immiscible liquids or gases in liquids) to viscous fluids, such as peanut butter [19], Commercial in-line mixers are tubes as small as 0.8 in. outside diameter by 6 in. long. Inside the tubes stationary elements are positioned to blend the components of the mixture in primarily a radial manner. By providing a reactor with a high surface-area-to-volume ratio, efficient heat transfer is allowed. Static mixers are used for reactions where good... 

Endothermic reactions, such as steam reforming, are usually carried out in long narrow tubes filled with catalysts and externally heated by flames. The heat could be provided more uniformly and more accurately at the necessary level by a combustion catalyst coated on the outside of the tubes, and heat transfer rates could be further improved by coating the endothermic reaction catalyst on the inner wall of the tube. In this way, the heat of combustion is transferred to the heat sink (the endothermic reaction) through the solid wall, avoiding solid-gas heat transfer resistances. However, the tubular geometry is not most efficient for this application because of the difficulty to coat the inside of the tubes and the need to include static mixers to facilitate mass transfer to the catalytic surfaces. 

Measured Laminar Mixing Efficiency for Selected Static Mixers... 

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