Double-impeller agitator

The double-impeller agitator consists of two vertical shafts rotating in opposite directions, and each shaft has a series of horizontal arms attached. The lower blades have an upward thrust, whereas the upper ones repel the liquid downward. This conformation provides a reaction mix that is essentially homogeneous. 

Nitration vessels are usually equipped with one of three general types of agitating mechanism (1) single or double impeller, (2) propeller or turbine, with cooling sleeve, and (3) outside tunnel circulation. 

Effect of Agitation. Since the reduction process under consideration is a multiphase reaction, it is clear that the best results are obtainable only when the nitro compound, iron, and water-soluble catalyst are in intimate contact. A stirrer that merely pushes the iron around the bottom of the vessel and permits the charge to separate out into layers does not function efli-ciently. It is apparent, therefore, that, a sturdy sleeve-and-propelier or double-impeller type of stirrer will in some cases be superior to the slow-moving plow type, speeding up the reaction considerably. 

Solid—solid blending can be accomplished by a number of techniques. Some of the most common include mechanical agitation which includes devices such as ribbon blenders, impellers, paddle mixers, orbiting screws, etc a rotary fixed container which includes twin-shell (Vee) and double-cone blenders and fluidization, in which air is used to blend some fine powders. 

In a polymerisation reactor, a monomer/polymer solution is to be agitated in a baffled mixing vessel using a double turbine (6 fiat blades) impeller, with the configuration B-B in Table 8.1, at a rotational speed of 2Hz. The solution exhibits power-law behaviour with n = 0.6 and m = 12 Pa-s° . Estimate the power required for a 300 mm diameter impeller. The density of the solution is 950kg/m. ... 

Adhesive used in dip applications shonld be kept under continuous agitation. If a dip tank is used, double diaphragm type circulating pumps are recommended and impeller type agitators shonld be nsed. 

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