Sieve Tray Specifications

Capacity Quite similar to sieve tray, as high or higher than bubble cap tray from 50% up to 100% design rate (varies with system and design criteria). Performance at specification quality falls off at lower rates. 

Kister et al. [213] have concluded from examining reported cases of cross-flow channeling related to poor sieve tray column performance that under specific conditions the cross-flow channeling does occur. See Figure 8-142 [213] for diagram of the postulated vapor flow across a tray. It is known to occur for valve trays and bubble cap trays. This condition has not been studied very much in the open literature however, several investigators including myself have observed in industrial practice the... 

The method of calculation introduced in this chapter not only allows an exact determination of the column diameter for nonpulsed sieve tray columns, but also allows a good estimation of the diameters of pulsed and stirred extractors. For the latter, however, more exact specific equations exist for the flooding point, see for example [1,4]. 

The correlations for sieve and bubblecap trays have no provision for multipass flow of liquid. Their basic data may have been obtained on smaller towers with liquid flow equivalent to two-pass arrangement in towers 8 ft dia. The sieve tray correlation should be adapted to multipass flow by comparison with results obtained by the valve tray correlation in specific cases. 

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. 

The specification is the same for all plates at or below the weak-acid feed point. The only operating parameter in this region to change significantly is the temperature. The bottom plate temperature is 65°C and the weak-acid feed tray is closer to 50°C. Even this temperature difference is not expected to affect the tray design such that individual sieve plates need to be sized. The operating parameters at the bottom sieve tray are therefore given as follows ... 

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. 

Part II contains the design of a major item of equipment (in this case study, it is a sieve-tray absorption column (Chapter 9) ), including the mechanical design, fabrication, materials specification, detailed engineering drawing, HAZOP study, control scheme and associated instrumentation. In summary, as complete and professional a design as... 

Data specific to tray type must be established next, but these inputs will be discussed later. The data inputted for the next six prompts are the same for all tray types and are primarily for tray efficiency calculations. If tray efficiency or tray liquid residence time values are not desired, these inputs may be skipped (i.e., remain as zero values). However, for bubble cap and sieve trays, the SURF TENS DYN/CM prompt is for active area tray flood calculation. This value should therefore be inputted. 

Valve trays. Manufacturer literature contains correlations for entrainment flooding (7-9). The three sieve tray correlations above are also applicable to valve trays. Of the three, the author recommends the Kister and Haas (15) correlation because it was specifically extended for valve trays and because it possesses the advantages listed above. When applying this correlation to valve trays, is the fractional hole... 

Specification sheet for sieve-tray distillation column. 

Because of their proprietary nature, valve trays are usually designed by their respective vendors based on process specifications supplied by the customer. However, most fabricators publish technical manuals that make it possible to estimate some of the design parameters. The procedure for calculating valve-tray pressure drop outlined here has been adapted from the Koch Design Manual. As for the other column specifications required, they can be obtained via the same calculation procedures outlined above for the sieve-tray design. 

Distillation towers feed-tray location for, 10 optimum reflux ratio for, 371-376 specifications for, 16 (See also Bubble-cap contactors, Packed towers. Sieve trays, and Valve trays) Distribution costs, 194, 196, 207, 211 Distribution in statistical analyses, 745-746 Dividends, tax exemptions for, 259 Documentation, 137-149,452-476 Double-entry bookkeeping, 143-144 Downcomers in tray columns, 684-686 Drives, cost of 532-533 Dryers, cost of 713-716... 

The electroresistivity probe, recently proposed by Burgess and Calder-bank (B32, B33) for the measurement of bubble properties in bubble dispersions, is a very promising apparatus. A three-dimensional resistivity probe with five channels was designed in order to sense the bubble approach angle, as well as to measure bubble size and velocity in sieve tray froths. This probe system accepts only bubbles whose location and direction coincide with the vertical probe axis, the discrimination function being achieved with the aid of an on-line computer which receives signals from five channels communicating with the probe array. Gas holdup, gas-flow specific interfacial area, and even gas and liquid-side mass-transfer efficiencies have been calculated directly from the local measured distributions of bubble size and velocity. The derived values of the disper-... 

The important design variables in this problem are the number of trays and the oil flow rate. Seven (or more) sieve trays were needed to reach the desired reduction in the propane content of the gas mixture. A complete set of configuration and operation specifications is given in Table 14.7. Calculated product stream flows and compositions are also given. The column and tray design is summarized in Table 14.8. 

In order to calculate the number of mass transfer units, the mass transfer coefficients must be estimated, either based on experimental data or from empirical correlations. The following correlation (Chan and Fair, 1984) was developed for binary systems, and specifically applies to sieve trays. In this correlation Nq and N are expressed in terms of residence time and interfacial area instead of the standard forms of Equations 14.26 ... 

An adaptation of the AIChE model was published by Chan and Fair, is specific to sieve trays, and is based on larger-scale sieve tray measurements. For the vapor phase. 

The deentraining device of Fig. 5.7-11 may not be needed if the "contaminated overhead vapor meets distillate specifications. Entrainment data for sieve and bubble-cap trays have been correlated by Fair and coworkers 10 as shown in Fig. 5.7-12. The sieve tray data are for trays with small (less than 7 mm) diameter. Visual dsla of FRI. released as a movie.11 show that uuder distillation conditions 3 mm holes enlmin sigaificantly less than 12.7 mm boles, with hole areas and gross vapor rales being equal,... 

---