Trays types

Distillation towers are the heart of a process plant, and the working component of a distillation column is the tray. A tray consists of the following components, as shown in Fig. 3.2  

There are two types of tray decks perforated trays and bubble-cap trays. In this chapter, we describe only perforated trays, examples of which are 

Possibly 90 percent of the trays seen in the plant are of these types. Perforated tray decks all have one feature in common they depend on the flow of vapor through the tray deck perforations, to prevent liquid from leaking through the tray deck. As we will see later, if liquid bypasses the outlet weir and leaks through the tray deck onto the tray below, tray separation efficiency will suffer. 

---

Direct-Heat Tray Dryers Satisfactory operation of tray-type dryers depends on maintaining a constant temperature and a uniform air velocify over all the materi being dried. 

Tray dryers may be of the tray-truck or the stationary-tray type. In the former, the trays are loaded on trucks which are pushed into the dryer in the latter, the trays are loaded directly into stationary racks within the dryer. Trucks may be fitted with flanged wheels to run on tracks or with flat swivel wheels. They may also be suspended from and moved on monorails. Trucks usually contain two tiers of trays, with IS to 48 trays per tier, depending upon the tray dimensions. 

FIG. 12-85 Perforated-tray type of reactor-discharge control. 

The separation operation called distillation utihzes vapor and hquid phases at essentially the same temperature and pressure for the coexisting zones. Various lands of devices such as r andom or sti uctui ed packings and plates or tr ays are used to bring the two phases into intimate contact. Trays are stacked one above the other and enclosed in a cyhndrical shell to form a column. Pacldngs are also generally contained in a cyhndrical shell between hold-down and support plates. A typical tray-type distillation column plus major external accessories is shown schematically in Fig. 13-1. 

Refitting of a tray-type column is desired to increase loading, increase efficiency, and/or decrease pressure drop. Structured packing is pariicularly applicable in this case. 

Design data for separation of the particular or similar mixture in a packea column are not available. Design procedures are better estabhshed for tray-type columns than for packed columns. This is particularly so with respect to separation efficiency since tray efficiency can be estimated more accurately than packed height equivalent to a theoretical stage (HETP). 

Figure 8.2.2 Conceptual scheme for a tray-type adiabatic reactor.

Figure 2. Estimation of downcomer area for a tray-type distillation column.

Smith uses settling height as a correlating factor which is intended for use with various tray types. The correlation is shown in Figure... 

Compared more with tray type performance than other packing materials. Usually used in large diameter towers, above about 24-inch dia., but smaller to 10-inch dia. available. Metal only. 

Knox has provided the following graphs for estimating the required vent steam from boiler feedwater deaerators. Vent steam rate depends upon the type of deaerator (spray or tray type) and the percentage of makeup water (in contrast to returning condensate). Low makeup water rates require relatively lower steam vent rates, but there is a minimum rate required to remove CO2 from the returning condensate. 

Figure 2. Steam vent rate vs. deaerator rating for a tray-type deaerator.

Smith" uses settling height as a correlating factor, which is intended for use with various tray types. The conrelation is shown in Figure 1. Curves are drawn for a range of settling heights from 2 to 30 inches. Here, U is the vapor velocity above the tray not occupied by downcomers. 

Figure 4-63. Tray-type scrubber with continuous sludge removal. Courtesy of National Dust Collector Corp.

Tray types Sieve or valve trays only... 

TOWER INTERNALS SPECIFICATIONS TRAY TYPE COLUMNS... 

No> of Tray Type Fixe[Pg.217]

Figure 8-156B. Tower internals specifications form, tray type columns.

Tray types are selected for performance. However, when a particular type is not specifically required, it is well to consider that, in carbon steel, the trays installed (not including tower shell) cost approximately ... 

Figure 3.4 (a) Tray type deaerator (b) exchange packing type deaerator (c) spray type deaerator and (d) atomizing type deaerator. 

It should be emphasized that the overall stage efficiency from Equation 9.61 should only be used to derive a first estimate of the actual number of distillation trays. More elaborate methods are available but are outside the scope of this text. In practice, the stage efficiency varies from component to component, and more accurate calculations require much more information on tray type and geometry and physical properties of the fluids. 

Tray stack heigrt, ft. Tray diameter, ft. Tray spacing, in. Tray type Material... 

In a contact sulphuric acid plant the secondary converter is a tray type converter, 2.3 m in diameter with the catalyst arranged in three layers, each 0.45 m thick. The catalyst is in the form of cylindrical pellets 9.5 mm in diameter and 9.5 mm long. The void fraction is 0.35. The gas enters the converter at 675 K and leaves at 720 K. Its inlet composition is ... 

---