Tray Design and Operation

Once the process design is completed, the equipment design begins. This phase of the design translates the process requirements (i.e., the vapor and liquid loads in each section of the column) into actual hardware. 

The hardware design proceeds in two phases primary (basic) and secondary (detailed layout). The primary phase sets column diameter, type of tr, and split of tray area into bubbling and downcomer areas. This phase also provides a preliminary (and usually close) estimate of tray spacing, number of passes, and other features of tray and downcomer layout such as weir height, fractional hole area, hole diameter, and clearance under the downcomer. These estimates are later firmed up in the secondary phase. 

Functionally, the primary phase sets the ms(ior equipment requirements, while the secondary phase engineers the finer details. The primary phase has a msgor impact on column costs, but a relatively small influence on achieving trouble-free operation. These roles are reversed in the secondary phase it has a relatively small impact on column costs, but a major impact on achieving trouble-free operation. 

The discussions in this chapter emphasize sieve and valve traj, as these trays are most frequently encountered in industrial practice. Several of the considerations also apply to other tray types (e.g., bubble-cap trays). Considerations unique to bubble-cap tra3rs were excluded from this chapter. The infrequent application of this type of tray in modern distillation practice argues against a detailed discus- 

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Which of these two opposing effects dominates depends on the tray design and operating level. The pressure drops through valve trays change little with vapor rates unless the valves are completely lifted. Therefore the second effect is sometimes larger than the first. If this occurs, an increase in vapor boiiup produces a transient increase in liquid rates down the column. This increase in liquid... 

Engineers will find detailed information on key fractionation concepts. .. column process design and shortcut calculations. .. tray design and operation. .. tray efficiency. .. packing design and operation. .. packing efficiency and scaleup. .. packing capacity and pressure drop. .. and much more. 

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