Mechanically pulsed column

Mechanically Pulsed Column. The Karr column (Fig. 23) consists of perforated plates ganged on a common shaft which is oscillated by an external drive. The perforated area and hole size are much larger than in typical sieve plate operation. At high amplitude x frequency product in larger columns, the tendency for excessive backmixing can be curtailed by installation of some fixed baffles. 

In many types of contactors, such as stirred tanks, rotary agitated columns, and pulsed columns, mechanical energy is appHed externally in order to reduce the drop si2e far below the values estimated from equations 36 and 37 and thereby increase the rate of mass transfer. The theory of local isotropic turbulence can be appHed to the breakup of a large drop into smaller ones (66), resulting in an expression of the form... 

In many lypes of contactors, such as stirred tanks, rotary agitated columns, and pulsed columns, mechanical energy is applied externally in order to reduce the drop size and thereby increase the rate of mass transfer. 

Pulsed columns are generally not used for column diameters greater than 180 cm because of problems with mechanical support and pulse generation. The great amount of backmixing also causes uncertainties in column performance. Small pulsed columns have been successfully used for the extraction of metals from slurries (Warwick, 1973). 

Extraction columns can be further sub-divided according to the method used to promote contact between the phases packed, plate, mechanically agitated, or pulsed columns. Various types of proprietary centrifugal extractors are also used. 

In the case of mechanically aided or pulsed columns, the choice of the continuous diase is a key consid-entkm since the columns can be operated with the interface either at the top or the botmm of the column. For spray columns, it is usually more efficient to erate the column with mass transfer from the continuous to the disperse phase and the avsulable HTU correlations are more reliable on that basis. To some degree, the same arguments apply to mechanically aided and pulsed columns. In any event, the contimious phase is often cht so as to maximize the interfacial area per unit length of column. If the solvent4o-raffinate flow ratio is greater than 1, this will occur when the raffinate phase is continuous. 

It is envisaged that this process could be operated with the simple type of mechanically stirred mixer-settler which is satisfactory in the Springfields uranium purification process. The Femald type of sieve-plate pulse column is another alternative. 

The Sonic Sifter has been designed to combine two motions to provide a precise particle separation. A vertical oscillating column of air and a repetitive mechanical pulse is used to move the material to be sifted through a single sieve or set of sieves. The name Sonic Sifter appears to come... 

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