Trays tower dimensions

The propylene fractionator operates at a pressure of 1.8 to 2.0 MPa with more than 160 trays required for a high purity propylene product. Often a two-tower design is employed when polymer grade (99.5%+) is required. A pasteurization section may also be used when high purity is required. The bottoms product contains mainly propane that can be recycled to the cracking heaters or used as fuel. Typical tower dimensions and internals for a 450,000 t/yr ethylene plant with naphtha feed are summarized in Table 7. 

Consider the absorber of Example 3.7. Assume that the wash oil is n-tetradecane (C14H30). The absorber will be a cross-flow sieve-tray tower with dg = 4.5 mm on an equilateral-triangular pitch 12 mm between hole centers, punched in stainless steel sheet metal 2 mm thick, with a weir height of 50 mm. Estimate the number of real trays required, the dimensions of the absorber, and the power required to pump the gas and the liquid through the tower. Design for a 65% approach to the flooding velocity. 

Table 6.1 Recoimnenited general conditions and dimensions fw tray towers...

Work to dimensions only. Any warping of tray due to cutting of holes must be removed and finished plates shall be made perfectly flat for Installation In tower. Manhole plates to have suitable clamps or hook bolts and gaskets. 

To guarantee a proper downcomer seal, the bottom edge of a downcomer should be about V2 inch below the top edge of the outlet weir. This dimension should be carefully checked by process personnel when a tower is opened for inspection. It is quite easy for sloppy tray installation to distort this critical factor. 

A direct-contact gas cooler system operates as follows Approximately 35,000 lb/hr of bone-dry air is passed over hot trays. The air is heated from 150°F to 325°F as it passes over the trays. It exits from the unit with a due point of 105°F. The hot air is sent to a direct-contact cooler, where its temperature is reduced back to 150°F. During the cooling stage, the air is dehumidified with water that is heated frpm 75°F to 105°F. The unit is rated at 3.5 inches of water pressure drop (a) Determine the number of diffusion units needed for this operation and (b) Establish the required dimensions for the direct-contact cooling tower (Hint Use standard low-pressure-drop data from the literature. Some of the older literature give pressure drop data for simple fill. See Sherwood, T. K. and C. E. Reed [6]. 

Tray key data for calculations. Please notice in Fig. 3.6 that three key data inputs are required tower diameter, side downcomer dimension, and number of tray liquid passes. 

Figure 3.7 displays tray downcomer area geometry. With a given tower diameter size, only one dimension, DC, sets the downcomer area. The following equations show how the downcomer area is determined. 

The interfacial area is known accurately only in some systems used in laboratory studies falling laminar films, laminar cylindrical jets, undisturbed gas-liquid and liquid-liquid interfaces, and solid castings of known dimensions immersed in liquids. In all reactor systems used industrially such as packed towers, spray towers, and bubble trays, the interfacial area is relatively difficult to determine. Photographic, gamma-ray, light scattering and chemical methods have been used to determine a in bubble dispersions (5, 6, 7, 8, iO, 42). For an average bubble diameter dn, a superficial gas velocity Usa and a bubble rise velocity Un,... 

I find it best to make a list of all nozzle locations relative to the tray number. This helps me check my location inside the tower. Also, I make a list of dimensions from the vendor tray drawings for easy reference in the column ... 

Typical experimental values are shown in Fig. 13.1-2 for a variety of tray spacings. Note that the values of C have the dimensions of velocity note also that the curve for 0.6 m (i.e., 24 in) is the standard for North America and hence the most important line on the graph. Not surprisingly, there are many efforts to improve this figure, like corrections for surface tension, for foaming, and for tower cross-section. 

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