Tray towers versus

Understand the advantages of using packed versus trayed towers for certain distillation applications. 

Trays versus packing for fractionation can be a standoff if large numbers of tray passes are allowed for large fractionation towers by the operating company. Often, company preferences will decide. The licensor may also have preferences based on field experience. 

Perforated trays are also used in fractionating towers. This tray is similar to the bubble-cap tray but has smaller holes ( lU inch, 6 mm, versus 2 inches, 50 mm). The liquid spills back to the tray below through weirs and is actually prevented from returning to the tray below through the holes by the velocity of... 

Tabulate the flows of vapor and liquid at all key trays in the tower as moles per hour. Plot these values versus tray number as vapor from tray and liquid to tray. This plot will be of great assistance in tower sizing calculations. 

The question of trays versus lean oil rate is a classical illustration of economic analysis. However, in the case of reboiled absorbers, the solution is seldom clear-cut since a savings in trays and tower height requires an increased lean oil rate. This in turn increases the refrigeration requirements and necessitates greater capital investment and operating costs. For the most part, the number of trays is preset, allowing lean oil rates to vary as a function of key component recovery. A suggested value for the number of trays is 10 theoretical trays, which will usually result in approximately 20 real trays. For low recoveries, this may result in lean oil rates which are too low for satisfactory tray operation. In this case, the number of trays should be reduced to provide an adequate oil rate. 

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