Mixer static

In chemical engineering, a number of unit processes are normally involved in the design of a system. These include distillation, filtration, recrystallization, mixing, etc. In industrial mixing, two or more materials are blended together to yield a homogeneous product. Mixers that employ propellers or turbines are quite common. Such dynamic mixers involve power driven elements that tend to make them expensive. 

The central element (C) may be easily produced from a flat sheet by punching followed by a forming operation. The mean pressure will be approximately the same for the upper and lower compartments requiring support of member C only at its ends. A welded support at the entrance end and a spider (multiple radial wires) support at the exit should suffice. 

Application of the Bernoulli and continuity equations will enable the ratio of transverse area to total longitudinal area and number of sections required for any degree of mixing to be determined. 

1 Briefly describe a new application for the principles involved in one of the following areas discussed in this chapter  

2 A weir (described in Problem 5.25) is being designed for use in sea water (5% denser than fresh water). Perform a dimensional analysis for the rate of flow and explain how the calibration for the same weir designed for fresh water should be altered for use with sea water. 

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Statexan ITA Static control agents Static decay Static decay times Static dissipation Static drying Static electricity Static eliminating devices Static mixers Static phenomena... 

Fig. 16. Static mixers which provide a contiauous mixing and processing unit with a nonmoving part. These static mixers can be easily installed in new and...

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. 

Air is compressed to modest pressures, typically 100 to 200 kPa ( 15-30 psig) with either a centrifugal or radial compressor, and mixed with superheated vaporized butane. Static mixers are normally employed to ensure good mixing. Butane concentrations are often limited to less than 1.7 mol 1 to stay below the lower flammable limit of butane (144). Operation of the reactor at butane concentrations below the flammable limit does not eliminate the requirement for combustion venting, and consequendy most processes use mpture disks on both the inlet and exit reactor heads. A dow diagram of the Huntsman fixed-bed maleic anhydride process is shown in Figure 1. 

Inline motionless mixers derive the fluid motion or energy dissipation needed for mixing from the flowing fluid itself. These mixers iaclude orifice mixing columns, mixing valves, and static mixers. 

Static mixers are used ia the chemical iadustries for plastics and synthetic fibers, eg, continuous polymeri2ation, homogeni2ation of melts, and blending of additives ia extmders food manufacture, eg, oils, juices, beverages, milk, sauces, emulsifications, and heat transfer cosmetics, eg, shampoos, hquid soaps, cleaning Hquids, and creams petrochemicals, eg, fuels and greases environmental control, eg, effluent aeration, flue gas/air mixing, and pH control and paints, etc. 

Fig. 30. Mechanism for laminar blending in Kenics static mixer (a) after one element, (b) two elements, (c) three elements, (d) four elements, and (e) five...

The energy consumed by a static mixer is given by P =. This energy is supplied by the pump used to create flow of the fluid through the... 

Fig. 31. Comparison of mixing rates with different static mixers A, Lightnin B, Komax C, Etoflo HV D, Kenics E, SMXL E, Hi-Mixer and G, SMX.

Pressure drop in static mixers depends very strongly on geometric arrangement of the inserts. It is simply defined in relation to the pressure drop AP in an empty tube given by Darcy s equation ... 

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). 

Under turbulent flow conditions, the Sauter mean diameter from two static mixers can be obtained from the following ... 

The constant depends on the hydraulic diameter of the static mixer. The mass-transfer coefficient expressed as a Sherwood number Sh = df /D is related to the pipe Reynolds number Re = D vp/p and Schmidt number Sc = p/pD by Sh = 0.0062Re Sc R. ... 

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. 

In the adiabatic process, the reactants are mixed rapidly ia a smaH-volume, high throughput static mixer without cooling (65). The hot product is used direcdy. A 250-mL reactor of this type can produce 8 t/d of peroxomonosulfuric acid. 

Minor ingredients include excess fatty acids, preservatives, and potentially other synthetic surfactants. Alternatively, mixing can be achieved through the use of in-line static mixers, with the accurate addition of the minors into a flowing stream of the wet soap. 

The Albright Wilson continuous SO loop sulfonation system claims use of a static mixer or mechanical mixer system under conditions of... 

Reaction Conditions. Typical iadustrial practice of this reaction involves mixing vapor-phase propylene and vapor-phase chlorine in a static mixer, foEowed immediately by passing the admixed reactants into a reactor vessel that operates at 69—240 kPa (10—35 psig) and permits virtual complete chlorine conversion, which requires 1—4 s residence time. The overaE reactions are aE highly exothermic and as the reaction proceeds, usuaEy adiabaticaEy, the temperature rises. OptimaEy, the reaction temperature should not exceed 510°C since, above this temperature, pyrolysis of the chlorinated hydrocarbons results in decreased yield and excessive coke formation (27). 

When it is deleterious, laminar flow can be avoided by mixing over the cross section. For this purpose static mixers in line can be provided. For very viscous materi s and pastes, screws of the type used for pumping and extrusion are used as reactors. 

Static mixer (bubble flow) 0.1-2 Up to 10 1-20 -1000 0.5 -Plug Plug 10-500... 

Bubble Reactors In bubble columns the gas is dispersed by nozzles or spargers without mechanical agitation. In order to improve the operation, redispersion at intei vals may be effected by static mixers, such as perforated plates. The liquid may be clear or be a slurry. 

Figure 20. Example of an in-line static mixer for polyelectolyte additions.

Application of static mixers in the chemical process industry... 

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