Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Trays, sieve operational limits

Trays operate within a hydraulic envelope. At excessively high vapor rates, liquid is carried upward from one tray to the next (essentially back mixing the liquid phase in the tower). For valve trays and sieve trays,. i capacity limit can be reached at low vapor rates when liquid falls through the rray floor rather than being forced across the active area into tlic downcomers. Because the liquid does not flow across the trays, it rass.scs contact with the vapor, and the separation efficiency drops dramatically. ... [Pg.142]

Weeping capacity is more related to turndown operation. Typically, 80% weep defined by equation (12.52) is used as the weep limit. Valve trays provide better turndown capacity in 3 1 versus sieve trays in 2 1. In other words, valve trays could operate in 30% of normal load with weep rate less than 10%. [Pg.277]

There are diree factors that limit the accuracy of the preceding analysis. The first of these relates to the phenomenon of inverse response discussed in Chapter 13. It is characteristic of valve tray columns and some sieve tray columns operating at low boilup rates. It exercises its most serious effect in those columns where base level is controlled via steam flow. If the level becomes too high, the level controller increases the steam flow. But this causes a momentary increase in base level due to the extra liquid coming down the column (also due to thermosyphon reboiler swell ). Without proper design the level controller can become very confused. This is discussed in detail in Chapter 16. [Pg.333]

Air stripping is used to remove 90% of the toluene (molecular weight = 92) dissolved in a 10 kg/s (159 gpm) wastewater stream. The inlet composition of toluene in the wastewater is 500 ppm. Air (essentially free of toluene) is compressed to 202.6 kPa (2 atm) and bubbled through a stripper which contains sieve trays. In order to avoid fire hazards, the concentration of toluene in the air leaving the stripper is taken as 50% of the lower flammability limit (LFL) of toluene in air. The toluene-laden air exiting the stripper is fed to a condenser which recovers almost all the toluene. A schematic representation of the process is shown in Fig. 2.11. Calculate the annual operating cost and the fixed capital investment for the system. The following physical and economic data are available ... [Pg.28]

To determine a tray operation with respect to pressure drop, the ralue of hd must be assumed at a reasonable value,—the larger the better the contact, and higher the pressure drop. Values of hd should be limited to about 4 in., following sieve tray practice. [Pg.203]

A sieve-tray column with 15 plates is used to prepare 99 percent methanol from a feed containing 40 percent methanol and 60 percent water (mole percent). The plates have 8 percent open area, in. holes, and 2-in. weirs with segmental downcomers, (a) If the column is operated at atmospheric pressure, estimate the flooding limit based on conditions at the top of the column. What is the F factor and the pressure drop per plate at this limit (Z>) For the flow rate calculated in part (a) determine the F factor and the pressure drop per plate near the bottom of the column. Which section of the column will flood first as the vapor rate is increased ... [Pg.587]

The suitable control range of differential pressure controllers may be narrow, especially with valve trays (Fig. 19.126). In the valvethrottling range of a valve tray, and below the weep point of a sieve tray, pressure drop may be insensitive to vapor loads. Differential pressure control may therefore be difficult to apply imder turned-down conditions. Packed towers are not prone to this limitation (44), because pressure drop tends to be sensitive to vapor load over the entire operating range (Fig. 14.3). [Pg.601]

Fig. 6-35. Volumetric flow of disperse and continuous phase at the loading limit and operating range of a sieve tray. Representation according to Reissinger et al. [6.23] and PanoFER et al. [6.42]. Fig. 6-35. Volumetric flow of disperse and continuous phase at the loading limit and operating range of a sieve tray. Representation according to Reissinger et al. [6.23] and PanoFER et al. [6.42].
The two critical areas for deposit formation in a column are at the trays, where vapor passes through a valve, sieve, flapper, or riser, and in the flash zone, where vapor condenses. Operating history sometimes indicates which areas require cleaning for example, the vapor line is suspect if the column vapor rate becomes limiting. Inspection is necessary to determine the extent and location of fouling. [Pg.239]


See other pages where Trays, sieve operational limits is mentioned: [Pg.565]    [Pg.168]    [Pg.170]    [Pg.203]    [Pg.158]    [Pg.187]    [Pg.75]    [Pg.376]    [Pg.512]    [Pg.170]    [Pg.203]    [Pg.99]    [Pg.170]    [Pg.376]    [Pg.321]    [Pg.451]    [Pg.802]   
See also in sourсe #XX -- [ Pg.383 ]




SEARCH



Operating limits

Operational Limits

Sieve operation

Sieve trays

© 2024 chempedia.info