Pulsed Packed and Sieve Tray Towers

A rapid reciprocating motion imparted to the liquid in a tower results in improved mass transfer. This action can be accomplished without parts and bearings in contact with the process liquids and consequently has found favor for handling hazardous and conosive liquids as in nuclear energy applications. Most of the applications still are in that industry, but several other installations are listed by Lo et al. (1983, pp. 345, 366). Packed colunms up to 3mdia and 10 m high with throughputs in excess of 200 m /hr are in use. 

Both packed and perforated plate towers are in use. The most 

Extraction efficiency can be preserved over a wide range of throughputs by adjusting the product fAp. A comparison of several correlations of TfTU made by LogsdaU and Slater (in Lo et al., 1983, pp. 364) shows a four- to five-fold range, but a rough conservative rule can be deduced from these data, namely 

Flooding, holdup, and mass transfer rates are highly interdependent and are not simply related. Reissinger and Schrdter (1978) state that fray towers in comparison with other types have good efficiencies at 60 m m hr at frequencies of 60-90/min and amplitudes of 10 mm. Packed towers have about 2/3 the capacities of fray towers. Also in comparison with unagitated towers, which are limited to interfacial tensions below lOdyn/cm, pulsed towers are not limited by interfacial tension up to 30-40 dyn/cm. Some 

---

Pulsed packed and sieve tray towers may operate at frequencies of 90 cycles/min and amplitudes of 6-25 mm. In large diameter towers, NETS of about 1 m has been observed. Surface tensions as high as 30-40 dyn/cm have no adverse effect. 

---