Efficiency of mixing

A qualitative picture of the flow field created by an impeller in a mixing vessel in a single-phase liquid is useful in establishing whether there are stagnant or dead regions in the vessel, and whether or not particles are likely to be suspended. In addition, the efficiency of mixing equipment, as well as product quality, are influenced by the flow patterns prevailing in the vessel. 

Corexit 9527 is a water-and ethylene glycol monobutyl ether-dissolved dispersant. The nature of the surface-active agent has not been disclosed. Laboratory tests were conducted using 0.5-mm thick, fresh Alberta Sweet-Mixed Blend crude oil treated with Corexit 9527 dispersant applied from an overhead spray boom [165]. The effects on dispersion efficiency of mixing jet pressure, mixing jet flow rate, jet standoff distance, and vessel speed were evaluated. The system operates with a nozzle pressure of 7000 kPa, a flow rate of 55 liter/min per nozzle, and nozzles positioned approximately 0.6 m from the water surface. In laboratory tests, such a system was capable of dispersing 80% to 100% of the surface slick. 

With all mixers, however, it is necessary to establish that an acceptable degree of homogeneity has been reached. Quantitative methodologies for establishing an index of mixing or efficiency of mixing are reported in the literature [94]. 

Continuous flow stirred tank reactors are widely used in the chemical process industry. Although individual reactors may be used, it is usually preferable to employ a battery of such reactors connected in series. The effectiveness of such batteries depends on the number of reactors used, the sizes of the component reactors, and the efficiency of mixing within each stage. 

The previous conflicting investigations may now be rationalized. Red phosphorus is known to thermally convert to white phosphorus, which will burn in air. If white phosphorus is formed, a fire is expected and no flame retardant activity will be observed. On the other hand, if the phosphorus reacts with the polymer as in Scheme 1, then thermal stabilization is expected. The efficacy of red phosphorus seems to be closely related to the efficiency of mixing of the additive and the polymer, when they are well-mixed the phosphorus will react with the polymer and lead to flame retardant activity, if the mixing is poor then the phosphorus will be converted to the white allotrope and burning will result. Since all of the work reported herein was carried out in sealed tubes under vacuum, the phosphorus must react and lead to stabilization of the polymer against molecular weight loss and fuel production, i.e. thermal stabilization. 

Efficiency of mixing from data on fast reactions in multi-jet reactors and stirred tanks. AIChE Journal 27, 184-192. 

The proportions of the desired 2,6-isomer and the unwanted 2,2-isomer in the alkylated product will vary depending on the rate and efficiency of mixing of the benzyl bromide with the lithium enolate. If the alkylation of the initially formed enolate could be effected without any eiiolatci equilibration, less than 2% of the unwanted 2,2-isom( r would be e. )oct( d. ... 

The use of the tanks-in-series model for packed beds can be more strongly justified. The fluid can be visualized as moving from one void space to another through the restrictions between particles. If the fluid in each void space were perfectly mixed, the mixing could be represented by a series of stirred tanks each with a size the order of magnitude of the particle. This has been discussed in detail by Aris and Amundson (A14). The fluid in the void spaces is not perfectly mixed, and so an efficiency of mixing in the void spaces has to be introduced (C6). This means that the analogy is somewhat spoiled and the model loses some of its attractiveness. In laminar flow the tanks-in-series model may be still less applicable. 

One would think that increased efficiency of mixing (standard efficiency is taken as 80%) could further improve water reduction. However, as can be proven by making variations in these calculations, that efficiency does not affect water use rate to a large degree. The two most Important variable for water use rate control are BS W effluent percentage and salt content of dilution water. 

From the early days of the industry it was appreciated that the dispersion of compounding ingredients, particularly carbon black, in the rubber can have a large effect on physical properties and that a measure of dispersion was important to judge the efficiency of mixing. The earliest methods were based on observing a freshly cut or tom surface with a lens when the smoother the surface the better the dispersion, and that basic principle remains to this day. 

A substantial excess of fluorine over the theoretical, equimolar amount is needed to complete the reaction because of the low solubility of fluorine. The amount of fluorine required can vary depending upon the scale of reaction, the flow rate, and the efficiency of mixing. 

With unidirectional shear, the efficiency of mixing, as expressed by instantaneous stretching starts with zero when the interfacial area element is perpendicular to the direction of shear, it reaches a maximum value at 45°, and from that point on it begins to diminish, making the mixing less and less efficient. Frequent reorientation is therefore desirable, as is the case with random chaotic mixing, which occurs in typical internal mixers and some continuous mixers. 

The shape of the nitrator bottom should also be carefully selected for a given stirring system. The efficiency of mixing with a propeller or turbine is higher when the nitrator has a conical or spherical bottom. 

The efficiency of mixing of powdered solids in a process stream is being investi ... 

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