Stirrers vortex

A Exempt equipment, such as magnetic stirrer, vortex mixer, calculators, LCD timer. 

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). 

Weigh 6.0 g of tricresyl phosphate into a 150-ml beaker, add 75 ml of tet-rahydrofuran (THF), and stir the mixture on a magnetic stirrer. Weight 4.0 g of PVC powder onto a folded piece of smooth paper. Adjust the stirring rate so that the vortex of the liquid in the beaker just reaches the magnetic follower and add the PVC powder in a slow stream. Do not allow the solid to coagulate into lumps before it has dissolved. Pour the solution into a screw cap bottle and seal until required. 

The gaseous reagents were distilled and collected inside the enclosure. The 10 vol.% alkylaluminum and 1 vol.% f-butyl halide solutions were freshly prepared. The reaction mixtures were stored manually or by a vortex stirrer. Since PIB tended to precipitate out of solution in highly swollen form, relative rates could thus be established by visual observation. 

The specific surface area of an industrial-sized continuous stirred tank reactor (CSTR) can be calculated from the reactor dimensions. However, it is difficult to estimate the effect of the formation of bubbles and of the stirrer-induced vortex at low melt viscosity. The calculation of the characteristic length of diffusion in a high-viscosity finishing reactor with devices for the generation of thin films with respective high specific surface areas is more complex. 

Extrapolation of 3-ft-diameter vessel experience to 10-ft-diameter full-scale operation without having developed or demonstrated scaling parameters for high-shear vortex mixers and stirrers working together. 

The reaction vessel is filled with hydrocarbon, leaving only enough gas volume to allow formation of a vortex down to the stirrer, so that gas... 

A 5-qt. enamel pail or bain-marie jar is fitted with two mechanical stirrers (Note 1) placed off center, a thermometer for reading low temperatures, and a dropping funnel, the lower end of which is placed just over the vortex created by one of the stirrer blades, so that each drop of added liquid is immediately mixed with and diluted by the chilled reaction mixture. 

A stainless steel mixing vessel, fabricated from 316 grade stainless steel with some form of cover that allows access for ingredient addition, is an ideal unit for mixing dilutables. The vessel is normally fitted with a stirrer, the power and design of which take account of whether sugar is to be added as a crystalline solid (and thus dissolved) or added as a syrup. Either a top-mounted propeller stirrer or a side-entry unit will mix components adequately, especially if the inside surface of the vessel is fitted with fixed baffles. The use of a stirrer that creates a sufficient vortex to draw in air should be avoided. 

It is possible to break the bubbles by using baffles or redistributors. Stirrers are not recommended because of vortex formation. 

The power required for a given stirrer type and associated vessel configuration depends on the speed of rotation N, the stirrer diameter du the density p, and the kinematic viscosity v of the medium. In vessels without baffles, the liquid vortex, and therefore the acceleration due to gravity, g, is immaterial, as long as no gas is entrained in the liquid. Thus, P = f(N, dt,p, v), and in the dimensionless form, Ne = /(Re), a relationship generally known as the power characteristics of the stirrer. Here, Ne = P/(pN3df) is the Newton or Power number, and Re s Ndf/v the Reynolds number. This relationship was described in Sections II and III for gas-liquid and gas-liquid-solid systems. 

For liquid-liquid mixtures, the calculations of mixing time and power (or Newton) number outlined above are valid for unbaffled vessels only as long as the vortex created by the stirrer does not reach the stirrer head. Otherwise, gas entrainment occurs and the physical properties of the system change. The depth of the liquid-gas interface at the vessel axis with respect to static liquid surface level, HL, can be related to the Froude and Galileo numbers. Some of the reported relationships are summarized in Table XIV. The value of H, at which the vortex reaches the upper impeller blades level can be expressed as... 

The cold solution is poured immediately into a previously assembled apparatus, consisting of a 5-1. three-necked flask, immersed in a 20-in. tub of ice-salt mixture (Note 6), and provided with a stirrer, dropping funnel, and thermometer for reading low temperatures. The solution is neutralized by the addition of 600-700 cc. of concentrated ammonium hydroxide (sp. gr. 0.90) at such a rate that the temperature never exceeds —5° (Note 7) the tip of the dropping funnel should be placed directly over the vortex created by the stirrer. After 500 cc. of ammonium hydroxide has been added, the solution is tested with Congo red paper at intervals corresponding to the addition of 50 cc. of ammonium hydroxide three to four hours is required for the neutralization. An additional 100 cc. of ammonium hydroxide is then added. 

---