Plate towers valve trays

Example 5 Determination of holdup time in downcomer. A valve-tray tower with 24-in. plate spacing and liquid crossflow contains straight segmental downcomers. The overflow weir at the downcomer entrance is formed by an extension of the downcomer plate. The height of this weir is 3 in. The inside diameter D of the tower is 5 ft, and the weir length is 0. 60. If liquid with a density of 55 lb/ft3 flows across die plate at a rate of 30,000 lb/h, estimate the residence or holdup time in the downcomer from this plate. 

This chapter considers the vapor-liquid equilibrium of mixtures, conditions for bubble and dew points of gaseous mixtures, isothermal equilibrium flash calculations, the design of distillation towers with valve trays, packed tower design. Smoker s equation for estimating the number of plates in a binary mixture, and finally, the computation of multi-component recovery and minimum trays in distillation columns. 

Adsorbers, distillation colunuis, and packed lowers are more complicated vessels and as a result, the potential exists for more serious hazards. These vessels are subject to tlie same potential haz. uds discussed previously in relation to leaks, corrosion, and stress. However, llicse separation columns contain a wide variety of internals or separation devices. Adsorbers or strippers usually contain packing, packing supports, liquid distributors, hold-down plates, and weirs. Depending on tlie physical and chemical properties of the fluids being passed tlirough tlie tower, potential liazards may result if incompatible materials are used for llie internals. Reactivity with llie metals used may cause undesirable reactions, which may lead to elevated temperatures and pressures and, ullinialely, to vessel rupture. Distillation columns may contain internals such as sieve trays, bubble caps, and valve plates, wliicli are also in conlacl with tlie... 

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. 

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