Vortex agitator

Vortex agitated vials Biphasic phase transfer catalysis carben addition to C-C double bondsd... 

Hydrate the lipid film by repeated vortex agitation. 

Add 100 pL of d.d. H O (if applying, this should be preheated above the lipid Tc) and rehydrate the mixture by vortex agitation, taking care to hydrate the full quantity of the lyophilized powder. 

Mix 1 mL of solution 3 with 1 mL of solution 1 by vortex agitation. Then mix (vortex for 15 s) the resulting water-in-chloroform emulsion with a similar mixture composed of solution 2 and solution 4 (2.5 ml). 

A range of reaction vessels are available to enable synthesis scales ranging from 0.005 to 1.0 mmol (3 ml reaction vessel for 0.005,0.010, and 0.025 mmol 10 ml reaction vessel for <0.1 mmol 40 ml reaction vessel for <0.25 mmol 55 ml reaction vessel for <1.0 mmol). Different sizes of reaction vessels are required to enable resin swelling and efficiency of washing steps. Mixing in the reaction vessel occurs by vortex agitation that allows for efficient resin-fluid interaction. 

Fig. 17. Mixing of floating soHds in agitated tanks (a) no surface movement, full baffles width = T/12 (b) deep vortex, no baffles need high energy which causes tank to sway (c) precessing vortex, partial baffles width = T/50 and (d) submerged partial baffles.

Preparation is accompHshed by simple blending of the diluent into the hot base asphalt. This is generally accompHshed in tanks equipped with coils for air agitation or with a mechanical stirrer or a vortex mixer. Line blending in a batch circulation system or in a continuous fashion (40) is used where the volume produced justifies the extra faciUties. A continuous, line-blending system is appHcable to the manufacture of cutback asphalts and asphalt cements (Fig. 8). 

The pump may have formed a vortex at high flow rates or low liquid level. Does the vessel have a vortex breaker Does the incoming flow cause the surface to swirl or be agitated ... 

FIG. 15-23 Power for agitation impellers immersed in single-phase liquids, baffled vessels with a gas-liquid surface [except curves (c) and (g)]. Curves correspond to (a) marine impellers, (h) flat-blade turbines, w = dj/5, (c) disk flat-blade turbines witb and without a gas-liquid surface, (d) curved-blade turbines, (e) pitcbed-blade turbines, (g) flat-blade turbines, no baffles, no gas-liquid interface, no vortex. 

Figure 7-9. Agitator flow patterns, (a) Axial or radial impellers without baffles produoe vortex, (b) Off-oenter looation reduoes the vortex, (o) Axial impeller with baffles, (d) Radial impeller with baffles. (Source Wales, S. M., Chemioal Prooess Equipment—Seleotion and Design, Butterworths Series in Chemical Engineering, 1988.)...

A vertical cylindrical, and mechanical agitated pressure vessel, equipped with baffles to prevent vortex formation is the most widely used fermenter configuration. The baffles are typically one-tenth of the fermenter diameter in widtli, and are welded to supports tliat extend from the sidewall. A small space between the sidewall and the baffle enables cleaning. Internal heat transfer tube bundles can also be used as baffles. The vessels must withstand a 45 psig internal pressure and full vacuum of -14.7 psig, and comply with the ASME code. 

Solid partieles in liquids generally tend to settle to the bottom of a vessel under gravity due to their exeess density. To maintain a suspension, some form of agitation is normally provided together with wall baffles to prevent vortex formation in the swirling flow (Figure 2.14). 

High turbulence is required for efficient mixing this is created by the vortex field which forms behind the blades. For all the gas to flow through this region it must enter the vessel close to and preferably underneath the disk hence it is recommended that spargers should always be nearer, about a distance of DJ2 below the agitator, where D( is the impeller diameter. 

In a mixed agitated vessel with high agitation rate, at the centre of the vessel a vortex often forms. To prevent a central vortex in tanks less than 3 m in diameter, four baffles each with a baffle width of 15-20 cm are necessary. A basic assumption is to select a ratio of liquid height to tank diameter from 2 1 to 6 1. 

In a forced vortex the angular velocity of the liquid is maintained constant by mechanical means, such as by an agitator rotating in the liquid or by rotation in the basket of a centrifuge. 

Thus, the energy per unit mass increases with radius r and is independent of depth In the absence of an agitator or mechanical means of rotation energy transfer will take place to equalise j/ between all elements of fluid. Thus the forced vortex tends to decay into a free vortex (where energy per unit mass is independent of radius). 

Figure 11. Flow patterns with an anchor agitator as in Figure 10 but at higher Reynolds numbers (above 10-20) where inertial effects become significant. Streamline schematic (12) shows stable trailing vortex.

For turbine agitators, impeller to tank diameter ratios of up to about 0.6 are used, with the depth of liquid equal to the tank diameter. Baffles are normally used, to improve the mixing and reduce problems from vortex formation. Anchor agitators are used with close clearance between the blades and vessel wall, anchor to tank diameter ratios of... 

Polymer solutions were prepared by dispersing the polymer powder in a saline solution prepared with distilled deionized water. Following complete dispersion in the vortex of the fluid the samples were agitated under mild conditions (< 100 RPM) until the solution was homogeneous. For some solutions the dissolution was so rapid that the agitation step could be eliminated. The polymer viscosities were then measured using a Ubbelohde viscometer. The pH of the polymer solutions was adjusted using dilute acetic acid and sodium hydroxide. Some polymers were supplied as liquids and were subsequently diluted with distilled deionized water to the appropriate concentration. 

If turbine or marine propeller agitators are used to mix relatively low viscosity liquids in unbaffled tanks, vortexing develops. In this case the liquid level falls in the immediate vicinity of the agitator shaft. Vortexing increases with rotational speed N until eventually the vortex passes through the agitator. As the liquid viscosity increases, the need for baffles to reduce vortexing decreases. 

Rushton, Costich, and Everett (1950) have listed values of a and fi for various vortexing systems. For a six-blade flat blade turbine agitator 0.1 m in diameter a = 1.0 and /3 = 40.0. 

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