Mixing static

Static mixing of immiscible Hquids can provide exceUent enhancement of the interphase area for increasing mass-transfer rate. The drop size distribution is relatively narrow compared to agitated tanks. Three forces are known to influence the formation of drops in a static mixer shear stress, surface tension, and viscous stress in the dispersed phase. Dimensional analysis shows that the drop size of the dispersed phase is controUed by the Weber number. The average drop size, in a Kenics mixer is a function of Weber number We = df /a, and the ratio of dispersed to continuous-phase viscosities (Eig. 32). 

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 ... 

Other Flow Straightening Deviees Other devices designed to produce uniform velocity or reduce swirl, sometimes with reduced pressure drop, are available. These include both commercial devices of proprietaiy design and devices discussed in the hterature. For pipeline flows, see the references under flow inverters and static mixing elements previously discussed in the Tncompressible Flow in Pipes and Channels subsection. For large area changes, as at the... 

Figure 5-42. Several types of static mixing elements usually adapted into pipe or fabricated casings. By permission, Koch Engineering Co.

Bulletin KSM-5, Static Mixing Technology, Koch Engineering Co., Inc., p. 3-9. 

KOCH Makes Static Mixing Elements For Every Application... 

Mixing performance, 306 Blending, 324 Emulsions, 324 Extraction, 324 Gas-liquid contacting, 324 Gas-liquid dispersion, 325 Liquid-liquid dispersion, 325, 326 Mixing vortex, 311 Motionless mixing, see static mixing National Fire Protection Association, 399 Net positive suction head, 160-194 Available from system, 160, 188, 189,... 

Rupture disk, 455 Safety relief valves, 454, 467, 481 Specifications, centrifugal pumps, 209 Spray nozzle particle size, 225 Standards and Codes, 31, 32, 33 Static electricity, 536 Static mixing, 332 Applications, 336 Calculations, 337, 338 Materials of construction, 337 Principles of operation, 335 Type of equipment 334-338... 

Static mixing catalysts Operation Monolithic reactors Microreactors Heat exchange reactors Supersonic gas/liquid reactor Jet-impingement reactor Rotating packed-bed reactor... 

In stirred vessels and static mixers the flow domain is bounded by complex boundaries due to the curvature of containing walls, the revolving impeller axis and/or static mixing elements. 

RATAPAR Not a process but a range of catalysts and catalyst supports using the principle of static mixing. Developed by Sulzer Chemtech since 1991. Used in catalytic distillation processes. 

Immiscible liquids, static mixing of, 16 715 Immiscible polymer blends, 20 318-319 barrier polymers, 3 396-398 heterogeneous, 20 357-358 Immiscible polymers, compatibilization of, 20 324-325... 

The manufacturer, whose main concern is to maintain a prevalence of the coupling reaction over the two others, i.e., a sufficiently fast coupling rate, achieves his end by combining the reactants at the exact moment of interaction (turbulence). Suitable equipment, such as a mixing nozzle or a static mixing tube, is therefore indispensable for a continuous operation but it is on the other hand quite successful in helping to avoid side reactions. 

Continuous operation In flow-type reactors, e.g., loop reactors, the space velocity of the reaction is determined through the installed static mixing device that is used to generate the dispersion, together with the velocity of the circiflating medium (catalyst- and substrate/product phase). Knowledge of these parameters allows one to set up a kinetic model for the investigated reaction. 

Beside these statical mixings just considered, the vibronic effects must be analyzed. Van Vleck (25) has shown that the vibronically induced noncentrosymmetric field Khem is related to the centrosymmetric static field hol by the approximate formula... 

S. Muerza, H. Berthiaux, S. Massol-Chaudeur, G. Thomas, A dynamic study of static mixing using on-line image analysis, Powder Technol. 128 (2002) 195-204. 

Cross-injection Mixing with Square Static Mixing Elements... 

The insertion of small static mixing elements (SME) is common to achieve swirls and eddies in pipe flow, albeit usually not being turbulent [71]. The flow obstacles are fairly small compared with the pipe diameter, unlike typical packings of static mixers which fully cover the diameter of the channel. Such mixing elements provide abrupt changes in surface orientation to result in flow separation and subsequent eddy production. 

The channel structure of the mixer is a simple cross, i.e. four channels which all merge at one junction [71]. A cross was preferred over a T-channel mixer since two interfaces instead of only one are initially created when the fluids are contacted. The top channel feeds one fluid, while the other fluid is injected via the left and right channels. The last, bottom channel functions as mixing and outlet zone. Squares, much smaller than the channel width, are positioned at the walls of this mixing channel and function as static mixing elements. The squares are positioned on alternate sides of the channels and at a distance corresponding to multiple square widths. 

Mixer type Cross-shaped micro mixer with static mixing elements Outlet channel width, depth 30 pm, 40 pm... 

Comparison of cross-injection mixing without and with static mixing elements... 

M 31] [P 28] The time evolution of the flow patterns in the cross-shaped micro mixer with two static mixing elements was monitored by simulation at time intervals of 50,150, 500 ps and 1 ms after application of pressure [71]. In addition to seeing the evolution of the swirling patterns, it was concluded from this analysis that at 500 ps a nearly homogeneous distribution of the mass fractions is given and at 1 ms this is indeed completed. Hence the theoretical mixing time of the mixer may be below 1 ms. 

Figure 1.65 CFD simulations giving 3-D mass contour plots in the cross-channel structure for a design without and one with two static mixing elements. The completeness of mixing can be judged from the cross-sectional mass distribution at the outlet [71] (by courtesy of Elsevier Ltd.).

M 31] [P 28] The flow patterns simulated by the ConventorWare and FLUENT 5 software concerning the flow in the cross-shaped micro mixer with two static mixing elements the same hence the predictability of the ConventorWare software was demonstrated [71]. 

M 31] [P 28] Velocity vector plots show the separation of the boundary layer before and after approaching the static mixing element [71]. Backflow occurs in the separation region. By this unsteady reattachment of the flow, new interfaces are constantly generated, when the flow has to pass a series of such mixing elements. 

The velocity contour plots show a higher velocity, a higher velocity gradient and rapid change of the direchon of the velocity components in the proximity of the static mixing elements compared with the rest of the flow in the channel (see Figure 1.66) [71]. 

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