Agitation efficiency

Some of the important parameters in the Bnchamp process are the physical state of the iron, the amount of water used, the amount and type of acid used, agitation efficiency, reaction temperature, and the use of various catalysts or additives. When these variables are properly controlled, the amine can be obtained in high yields while controlling the color and physical characteristics of the iron oxide pigment which is produced. 

Finally, the stirring system previously described was selected and was able to agitate efficiently 11 of PVA aqueous solution producing an axial flow accompanied by marked turbulence in the immediate vicinity of the impeller. 

Heat dissipation in bulk fat is considerably slower than in milk or cream this is related to the lower thermal conductivity of bulk fat and, in particular, the fact that bulk fat cannot be agitated efficiently. 

If the rate is then independent on the agitation efficiency at sufficiently high stirring speed (Figure 9.27), then it is conventionally assumed, that mass trasnport effects are minimized. 

Some viscosity may be expected to develop during the solution polymer stage of the polymerization. While the extent and duration of the viscosity that can be tolerated is a fimction of the agitation efficiency and heat removal capability of the reactor, the salt concentration is the primary parameter to be adjusted in order to obtain the optimum in-process viscosity. If the salt concentration has been properly adjusted, then at the onset of the precipitation event the viscosity of the system ops markedly and the polymerization is finished as a dispersion. If the salt concentration is too low during the polymerization, the precipitation event and transition to a heterogeneous system never occurs, and effective mixing and heat transfer will eventually be lost. If, on the other hand, the salt concentration is too high, the dispersion will have little thermodynamic stability in the absence of mechanical shear. 

If the rate is independent of the agitation efficiency at sufficiendy high stirring speed (Fig. 10.29), it is conventionally assumed that mass transport effects are minimized. 

A useful stirrer—sometimes termed a Hershberg stirrer— Fig. 11,7,5. for efficient agitation in round-bottomed vessels, even of... 

In the simplest case, the feed solution consists of a solvent A containing a consolute component C, which is brought into contact with a second solvent B. Eor efficient contact there must be a large interfacial area across which component C can transfer until equiHbrium is reached or closely approached. On the laboratory scale this can be achieved in a few minutes simply by hand agitation of the two Hquid phases in a stoppered flask or separatory fuimel. Under continuous flow conditions it is usually necessary to use mechanical agitation to promote coalescence of the phases. After sufficient time and agitation, the system approaches equiHbrium which can be expressed in terms of the extraction factor S for component C ... 

Many industrial processes involve a chemical reaction between two Hquid phases, for example nitration (qv), sulfonation (see Sulfonation and sulfation), alkylation (qv), and saponification. These processes are not always considered to be extractions because the main objective is a new chemical product, rather than separation (30). However these processes have many features in common with extraction, for example the need to maintain a high interfacial area with the aid of agitation and the importance of efficient phase separation after the reaction is completed. 

Mixing. Because of the heterogeneous nature of this system, efficient mixing is essential to ensure the intimate contact of the iron, nitro compound, and water soluble catalyst. An agitator which allows the iron to settie to the bottom and the other materials to separate into layers does not function efficientiy. On the other hand, a reaction whose rate is limited by the quaUty of the iron will not be significantly improved by better mixing. 

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