Pulse sieve tray column

Pulsed sieve tray columns differ significantly from static sieve tray colunms as they do not have any down comers. The light and the heavy phase pass periodically through the same holes. Furthermore, pulsed tray columns have a much larger relative free area of up to 0.25 with hole diameters of 2-A mm. 

Fig. 6.3-4 Typical performance data of ten different extractor designs for the system tolulene/acetone/water. MS mixer-settler, SE static sieve tray column, PC static packed packed column, RDC rotating disc contactor, PSE pulsed sieve tray column, PPC pulsed packed column, RZE agitated cell extractors...

The Graesser contactor takes an extreme position in the diagram. It has the highest separation efficiency (10 stages per meter) but the lowest capacity (1-2 m/h). The other extremum takes the static sieve tray extractor with only one equilibrium stage per meter and up to 50 m/h capacity. The capacity of a pulsed sieve tray column is as high as 30 m/h with a separation efficiency of 5 to 6 stages per meter. 

Fig. 6.4-9 Flooding in pulsed sieve tray columns according to Mersmann (1980). The experimental data show a significant dependency on the pulsation intensity a f...

FIG. 23-38 Efficiency and capacity range of small-diameter extractors, 50 to 150 mm diameter. Acetone extracted from water with toluene as the disperse phase, V /V = 1.5. Code AC = agitated cell PPC = pulsed packed column PST = pulsed sieve tray RDC = rotating disk contactor PC = packed column MS = mixer-settler ST = sieve tray. (Stichlmair, Chem. Ing. Tech. 52(3), 253-255 [1980]). 

Pulsing means that either the whole liquid content of a sieve tray column is continually pushed up and down by a piston that moves to and fro, or the whole plate package is moved up and down [3]. Figure 9.5 illustrates the two extractor constructions schematically. They show about the same efficiency... 

Fig. 9.5 Sieve tray columns with pulsing of the whole hquid content (left side) or of the whole plate package (right side, Karr column). The trays are meant to equalize the phase flows across the column cross section and to disperse the droplets as uniformly as possible.

The method of calculation introduced in this chapter not only allows an exact determination of the column diameter for nonpulsed sieve tray columns, but also allows a good estimation of the diameters of pulsed and stirred extractors. For the latter, however, more exact specific equations exist for the flooding point, see for example [1,4]. 

Code AC (Agitated CeU) - PTC (Pulsed Packed Cdumn) - PST (Pulsed Sieve Tray) - RDC (Rotating-Disc Contactor - PC (Pecked Column) - MS (Mixer Settler) - ST (Sieve Tray)... 

Pulsed columns Packed column Sieve tray column No internal moving parts, can deliver moderate to high efficiency, can handle moderate production rates, well suited to highly corrosive or toxic feeds requiring a hermetically sealed system Nuclear Petrochemical Metallurgical... 

FIG. 15-52 Pulsed-liquid columns, (a) Sieve tray column with pump-type pulse generator, (b) Packed column with air pulser. 

Pulsed sieve plate column HETS increases exponentially with diameter 0.4 m at 1 m dia. max. diameter 3 m superficial velocity about 5.5 L/s m sieve holes 3 to 8 mm velocities through the holes <0.2 m/s to minimize the formation of small drops. Tray efficiencies about 20 to 30%. 

A decisive parameter is the time of contact. In pulsed sieve tray colunms the time of instationary mass transfer is equal to the residence time of the dispersed phase in the space between two trays. In agitated colunms, the residence time in an agitation cell has to be taken. However, the application of the above equations to packed columns is difficult. Often recommended is the correlation of Handlos and Baron (1957) which has been developed and verified for oscillating drops ... 

There are two different types of energy input in sieve tray or perforated tray columns (Fig. 6-39) in a pulsed sieve tray extractor (PSE) the liquid column is pulsed in a swing tray extractor (STE) fixed sieve trays are mounted on a swinging axis which is driven by an infinitely variable, directly coupled geared motor, including crank shaft and connecting rod. The top and bottom section are expanded to allow the phases to rest and then separate. 

Fig. 9.6 Behavior of droplets near the sieve tray in a hquid-pulsed column during downstroke and upstroke of the hquid content.

Figure 14.13. Towers with reciprocating trays or with pulsing action, (a) Assembly of a 36 in. Karr reciprocating tray column (Chem. Pro. Co.), (b) Sieve trays used in reciprocating trays columns (left) large opening trays for the Karr column (middle) countermotion trays with cutouts (right) countermotion trays with downpipes for heavy phase, (c) Rotary valve pulsator, consisting of a variable speed pump and a rotary valve that alternately links the column with pairs of suction and discharge vessels, (d) Sieve tray tower with a pneumatic pulser [Proc. Int. Solv. Extr. Conf. 2, 1571 (1974)]. (e) A pulser with a cam-operated bellows.

Liquid-liquid extraction can take place in a column with various internals to foster contact between the dispersed and continuous liquid phases. Internals can include sieve trays, baffle trays and packing, as well as mechanical agitation and pulsing of the liquid. 

---