Sieve tray design diameter

For sieve trays, the number of kinetic heads equivalent to the total pressure drop through the plate itself is a function of the ratio of the sieve-hole diameter to the tray thickness and the ratio of the hole area per tray to the active area per tray as shown in Fig. 16-5. This pressure drop for a reasonable sieve-tray design is generally in the range of 1 to 3 kinetic heads, and Fig. 16-12 can be used to choose the most reasonable number to use in preliminary designs Designating the number of kinetic heads obtained from Fig. 16-12 as K.H., the pressure drop due to gas flow through the holes for a sieve tray expressed as liquid head is... 

Sieve Tray Design Perforations usually are in the range of 0.125 to 0.25 in (0.32 to 0.64 cm) in diameter, set 0.5 to 0.75 in (1.27 to 1.81 cm) apart, on square or triangular pitch. There appears to be relatively little effect of hole size on the mass-transfer rate, except that with systems of high interfacial tension, smaller holes will produce somewhat better mass transfer. The entire hole area is normally set at 15 to 25 percent of the column cross section, although adjustments may be needed. The velocity through the holes should be such that drops do not form slowly at the holes, but rather the... 

Because of their simplicity and low cost, sieve (perforated) trays are now the most important of tray devices. In the design of sieve trays, the diameter of the tower must be chosen to accommodate the flow rates, the details of the tray layout must be selected, estimates must be made of the gas-pressure drop and approach to flooding, and assurance against excessive weeping and entrainment must be established. 

Run the sieve-tray design program of Appendix E using these data. The program converges to a tower diameter D = 1.036 m and a tray spacing t = 0.6 m. When convergence is achieved, the results at the bottom of the tower are ... 

Equations (10.73) and (10.74) can be used with any consistent set of units.] The drop diameter corresponding to the above values is = 2dj. The value of a to be used is intennediate between that for the binaiy solvent pair and the equilibrium value for the extracting system if that can be estimated (data are scarce). Equations (10,73) and (10.74) are recommended for sieve-tray design, but if the resulting velocity calculates to be less than 0.1 m/s, Vq should be set at least at from 0.1 to 0.IS m/s and the drop diameter should be estimated from Fig. 10.46. 

Fair s empirical correlation for sieve and bubble-cap trays shown in Fig. 14-26 is similar. Note that Fig. 14-26 incorporates a velocity dependence (velocity) above 90 percent of flood for high-density systems. The correlation implicitly considers the tray design factors such as the open area, tray spacing, and hole diameter through the impact of these factors on percent of flood. 

A common type of distillation contacting device used in refinery applications is the sieve tray. In the early 50 s and for many years before, the bubble cap tray was the mainstay of the distillation field. A sieve tray consists of a flat plate with regularly spaced holes, normally 1/2 to 1 inch in diameter. Liquid flows horizontally across the tray and into a channel, called a downcomer, which leads to the tray below. The sieve tray exhibits good capacity, excellent efficiency, low pressure drop, and good flexibility i.e., it will operate quite efficiently at tower loadings which are 1/2 to 1/3 of design values. 

From experiments, equations have been derived that enable calculation of the minimum velocity in the nozzle, the nozzle velocity, and the Sauter diameter at the drop size minimum. They provide the basis for the correct design of a sieve tray [3,4]. Figure 9.4a shows the geometric design of sieve trays and their arrangement in an extraction column. Let us again consider toluene-phenol-water as the liquid system. The water continuous phase flows across the tray and down to the lower tray through a downcomer. The toluene must coalesce into a continuous layer below each tray and reaches... 

A sieve tray-type absorption column is proposed. The design specifies a column 1.8 m diameter, approximately 32 m high, and containing 59 sieve plates. Weak-acid condensate is added to tray 13 and make-up water is added at tray 59 (the top tray). Crossflow-type trays are employed from plates 1 to 13, however, a decreased liquid loading demands reverse flow-type trays for plates 14 to 59. The operating pressure is approximately 950 kPa and the operating temperature range is from 8°C to 65°C. 

The absorption column design represents a compromise between mass transfer factors and economic considerations. The final design specification is for a column of 1.8 m diameter, approximately 32 m high, and containing 59 sieve trays. 

Reference A3 (Figure 11.28) details the recommended plate configuration for liquid flowrate versus column internal diameter. A reverse flow-type sieve plate is suggested as shown in Figure 9.3. The pitch of the sieve-tray holes is selected so that the total hole area is reduced to 0.07 times the total column area. The other design criteria employed to provide the provisional plate specification are detailed in Table G,3. 

Total column height Internal diameter Operating pressure Operating temperatures Number of sieve trays Material of construction Design stress... 

To size the trays in UniSim Design, we must activate the tray sizing utility (from the Tools menu via Tools/Utilities/Tray Sizing). When sieve trays are selected with the default spacing of 609.6 mm (2 ft) and the other default parameters shown in Figure 4.25, then the results in Figure 4.26 are obtained. The column diameter is found to be 4.42 m. 

An altemative tray design is the sieve-plate tray (see Fig. 7). Sieve-plate trays are much cheaper to fabricate compared to bubble-cap trays since the tray consists of a circular plate with holes drilled through for the passage of vapor. These holes are generally much smaller in diameter than the bubble caps. 

Perhaps the simplest of cross-flow column tray designs is the sieve tray or perforated tray. The tray is a flat metal plate and the vapor openings are holes drilled in the plate. The holes are usually round, ranging from 1/8- to 1/2-inch diameter. Sieve trays have no liquid seals to prevent liquid from flowing down the holes. Liquid flow down the holes is prevented only by the upward flow of the vapor. 

Tray design encompasses the determination of the column diameter and the tray spacing as well as a number of mechanical considerations. The scope of the material in this chapter is limited primarily to the fundamentals involved in the design of single-pass sieve trays. The fundamentals involved in the design of valve trays are essentially the same as those involved in sieve trays. No attempt is made to treat bubble-cap trays, since valve and sieve trays have been used extensively in new installations since the early 1950s. Up until that time, bubble-cap trays were used almost exclusively. The design of bubble-cap trays has been treated by a number of authors see for example Van Winkle.17... 

---