Vertically tray towers

To allow for the vertical height required for packed tower distributors and redistributors—and in tray towers the vertical height used by additional trays—typically using 10%-20% of the vertical packed height (10% for 2-in. random packing and 20% for structured packing) [136] the analysis indicated ... 

An extractor column is generally a tall, vertical packed tower that has two or more bed sections. Each packed bed section is typically limited to no more than 8 ft tall, making the overall tower height about 40 to 80 ft. Tower diameter depends fully upon liquid rates, but is usually in the range of 2 to 6 ft. Liquid-liquid extractors may also have tray-type column internals, usually composed of sieve-type trays without downcomers. These tray-type columns are similar to duoflow-type vapor-liquid separation, but here serve as contact surface area for two separate liquid phases. The packed-type internals are more common by far and are the type of extractor medium considered the standard. Any deviation from packed-type columns is compared to packing. 

Distillation tray towers Vertical axial flow... 

In our schematic of a countercurrent cascade, we had the streams moving horizontally. Generally, a pump would then be required between each stage to overcome friction. With vapor and liquid, the density difference is sufficiently large, that we can use gravity to move the fluids if we stack the stages vertically rather than horizontally. A vertical stack of stages is called a tray tower. 

A5. As shown by the Leaning Tower of Pisa, towers that do not have a proper footing can develop a significant lean. Even if a distillation tower is structurally sound, leaning away from being vertical affects the operation. What is likely to go wrong for a tray tower if it leans ... 

The gas and liquid are often placed in contact in a large vertical cylindrical tower. Several tower designs are shown in Fig. 28.3. Packed towers, spray towers, tray towers, and reverse jet-type scrubbers have aU been used to treat acid plant tail gas. They are usually constructed of fiber reinforced plastic with a suitable corrosion-resistant liner. Unlined stainless steel and rubber-lined carbon steel are also used. 

Horizontal natl. circ. Ease of maintenance Lower skirt height than vertical Less pressure drop than vertical Longer tubes possible Less cost than kettle No theoretical tray Extra space and piping as compared to vertical Fouls easier as compared to vertical Accumulation of higher boiling point components in feed line, i.e., temperature may be slightly higher than tower bottom... 

In a trayed absorber the amine falls from one tray to the one below in the same manner as the liquid in a condensate stabilizer (Chapter 6, Figure 6-4). It flows across the tray and over a weir before flowing into the next downcomer. The gas bubbles up through the liquid and creates a froth that must be separated from the gas before it reaches the underside of the next tray. For preliminary design, a tray spacing of 24 in. and a minimum diameter capable of separating 150 to 200 micron droplets (using the equations developed in Volume 1 for gas capacity of a vertical separator) can be assumed. The size of packed towers must be obtained from manufacturer s published literature. 

L = liquid flow rate, lb/hr-fl of cros,s-sectional area m = constant, allowing for vertical tower height consumed by distribution/redistribution equipment S = tray spacing, in. 

The common reason for out-of-levelness of trays is sagging of the tray decks. Sags are caused by pressure surges and sloppy installation. Sometimes, the tray support rings might not be installed level or the tower itself might be out-of-plumb (meaning the tower itself may not be truly vertical). 

A typical arrangement (Fig. 17) consists of a vertical tower fitted with horizontal plates or trays, on which liquid and gas are contacted. Each tray is equipped with gas passages, which may be perforations in the tray floor or other devices such as valves or bubble caps that disperse the rising gas into the liquid layer. The liquid layer on the tray is maintained by the outlet weir. Liquid descends from each tray to the tray below via a downcomer. 

Vertical-plate extractor. Exemplified by the Bonotto extractor (Fig. 18-79), this consists of a column divided into cylindrical compartments by equispaced horizontal plates. Each plate has a radial opening staggered 180° from the openings of the plates immediately above and below it, and each is wiped by a rotating radial blade. Alternatively, the plates may be mounted on a coaxial shaft and rotated past stationary blades. The solids, fed to the top plate, thus are caused to fall to each lower plate in succession. The solids fall as a curtain into solvent which flows upward through the tower. They are discharged by a screw conveyor and compactor. Like the Bollman extractor, the Bonotto has been virtually displaced by horizontal belt or tray percolators for the extraction of oil seeds. 

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