Baffle towers

One of the most widely used spray-drying techniques for coffee extract involves spraying percolated coffee extract at 40°F into the top of a baffled tower of hot air at 480°F initially. The cooler wet air is removed toward the bottom of the tower and finally a powder of the coffee extract solids leaves the tower at about 90°F. These solids are in the form of hollow beads and contain 3% moisture. 

FIG. 15-41 Baffle towers, (a) Side-to-side flow at each tray, b) Center-to-center flow fdisk-and-doughnut style), fc) Center-to-side flow. [Reprinted frcm Treybai, Liquid Extraction (McGraw-HtU, 1963), with permisswn. Cepyright 1963 McGraw-Hill, Inc.]... 

BAFFLE TOWERS. These extraction towers contain sets of horizontal baffle plates. Heavy liquid flows over the top of each baffle and cascades to the one beneath light liquid flows under each baffle and sprays upward from the edge through the heavy phase. The most common arrangements are disk-and-doughnut baffles and segmental, or side-to-side, baffles. In both types the spacing between baffles is 1(K) to 150 mm (4 to 6 in.). 

Baffle towers contain no small holes to clog or be enlarged by corrosion. They can handle dirty solutions containing suspended solids one modification of the disk-and-doughnut towers even contains scrapers to remove deposited solids from the baffles. Because the flow of liquid is smooth and even, with no sharp... 

If either the batch or the tubular type of reactor is chosen, the reactor size and product distribution can be calculated by using the batch or longitudinal-flow equations. For a stirred-tank continuous reactor, the backmixing equations can be used. If a packed or baffled tower is used, then the calculations must be made for both the longitudinal and back-mixing cases. Proper extrapolation must then be made from empirical data or previous experience. 

For spray tower and baffle tower, see Section 5.2. For tray and packing see Section 4.2. 

See Section 4.2 for cost guidelines for packed and tray columns or as pressure vessel Section 10.1. See Section 5.2 for gravity spray, baffled tower, atmospheric scrubber, venturi and wet cyclone. Demister, see Section 9.1. 

Blenke-cascade reactor Baffled tower separating the reactor into different sections being mixed by upward flowing gas. Similar to plate columns. Liquid or liquid-solid mixture can be operated co- or countercurrently... 

Baffle Towers. These extractors consist of vertical towers containing horizontal baffles to direct the flow of the liquids. There are three principal types disk-and-doughnut, side-to-side, and center-to-side. 

Baffle Towers. Although no systematic study has been made for these extractors, it can be surmised that the important variables would be densities, viscosities, and interfacial tension of the liquids, and baffle shape, relative size, and spacing. A few data for capacities of towers of the type of Fig. 10.5 are indicated in Table 10.1 (33). 

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