Three pass trays

When feed to multipass trays is to be split unevenly, such as in a three-pass tray. In such cases, a feed trough (Fig. 2.4) is often preferred to a distributor (179, 307). 

To avoid excessively short liquid paths, several designers recommend that two-pass trays should only be installed when column diameter exceeds 4 to 6 ft (38, 48, 73, 138, 172, 211, 257, 319, 371, 409) three-pass trays should only be installed when column diameter exceeds 7 to 9 feet (38, 138, 211) and four-pass trays should only be installed when column diameter exceeds 10 to 12 ft (38, 138, 211). 

The author and others (238, 371) prefer avoiding an odd number of passes (e.g., three-pass trays) altogether. Their panels are far less... 

For this large a tower diameter, the need for a multipass tray needs to be considered, using Figure 14.5. The volumetric liquid flow rate = (215,000/60)/4.33 = 828 gpm. For this diameter and liquid flow rate, a three-pass tray is indicated. For a one-pass tray, a simulator gives a tower diameter of 9.5 ft, when the diameter is restricted to increments of 0.5 ft. For a three-pass tray, the tower diameter remains at 9.5 ft. 

Other calculations from a simulator for both single-pass and three-pass trays are as follows ... 

Convert from single- to dual-pass (or even four-pass) trays. Never use the three-pass trays, as poor vapor-liquid distribution will surely result. Keep to a minimum flow-path length of 1. 

If the weir loading is excessive, increase the number of tray deck passes from one to two, or from two to four. I don t use three-pass trays, because they lack symmetry. 

The purification unit consists of three valve-tray columns. The production medium for AA in the purification stage at 130-200 °C contains up to 16% water, 26% methyl iodide, and other components, such as methyl acetate (MA), methanol (MeOH), hydrogen iodide (HI), formic acid (FA), and propionic acid (PA) (PEP Report, 1994). The fractionation column removes the light components and portions of water in the mixture, and the dehydration column treats both water and FA. The last column, which is an SSC, produces the final AA product from the side draw by cutting off the remaining light and heavy components from... 

Figure 1. Schematic representation of in situ incubation for phytoplankton and benthic algae. (A) General disposition of trays with tubes and filters for cutting off different portions of the solar spectrum in the bottom a set up for benthic algae incubation is presented. (B) Close up of one tray containing duplicate quartz tubes for three different radiation treatments PAB, unfiltered solar radiation PA, PAR + UV-A and P, only PAR. (C) Transmission characteristics of various materials and filters used in photobiological...

Ruminococcus albus strain 7, (1), was grown on cellulose roll tubes according to the Hungate technique (2). Either Avicel (FMC Corporation, Marcus Hook, Pa.) or balled filter paper was used as the cellulose source. Three milliliters of melted cellulose-medium at 45 °C. in 16 X 150 mm. tubes were inoculated with the bacteria under a gas phase of 95% C02 and 5% H2. The tubes were subsequently stoppered and rolled in a tray of ice in order to form a film of agar medium around the... 

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