Energy-efficient pulsators

To intensify mass transfer, pulsed packed columns are used, especially in cases where extremely high product purities must be achieved and energy-efficient pulsators can be used [7,18, 21]. 

The pulsed-plate column is typically fitted with hori2ontal perforated plates or sieve plates which occupy the entire cross section of the column. The total free area of the plate is about 20—25%. The columns ate generally operated at frequencies of 1.5 to 4 H2 with ampHtudes 0.63 to 2.5 cm. The energy dissipated by the pulsations increases both the turbulence and the interfacial areas and greatly improves the mass-transfer efficiency compared to that of an unpulsed column. Pulsed-plate columns in diameters of up to 1.0 m or mote ate widely used in the nuclear industry (139,140). 

The RE process proceeds in three major types of equipment mixer-settler systems, column extractors, and centrifugal extractors. Countercurrent column extractors can be further subdivided into nonagitated nonproprietary columns and agitated proprietary extractors. Agitating the liquid-liquid system breaks up droplets and increases the interfacial area to improve the mass transfer and column efficiency. Various forms of energy input are used, e.g., rotation of propellers, impellers, and discs pulsation, vibration, and ultrasonic devices and centrifugal devices. 

The unique properties of underwater explosions are due to the high velocity of sound in water meaning that the pressure-wave travels approximately four times faster in water than it does in air. Furthermore, due to the high density and low compressibility of water, the destructive energy (from the explosion) can be efficiently transferred over relatively large distances. The most important effects caused by an underwater explosion are the corresponding shock-wave and the gas bubble pulsations. 

As an example, for the purification of caprolactum, it has been shown that the effectiveness of such a pulsation of the melt is especially helpful in cases of a low impurity content. It is rather easy to add a pulsation pump to an existing static crystallization unit, which makes it more efficient. In many cases the pulsation should be applied only in the final stage when impurity content in the feed is lowest, because the pulsation unit is most effective at that time, and additional costs and additional energy input in the crystallizer can be avoided in the earlier stages. 

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