Capacity, trays comparison

FIGURE 12.70 Generalize(f comparison of capacities, structure(f packings vs. high-capacity trays. [J. L. Bravo, 1998. Chem. Eng. 105 (2) 77.]... 

If all droplets were of the same size (the maximum size that can exist), the vapor velocity at which the droplets would become suspended but would not rupture is given by Eq. (12-31). Above any actual tray, a range of droplet sizes exists, and the maximum vapor velocity which can actually be reached is well below the values predicted by Eq. (12-31). Figure 12-13, taken from Manning,13 shows a comparison of the theoretical maximum vapor velocity given by Eq. (12-31) and the actual maximum vapor velocity for several high-capacity trays. 

Kister et al. [136] prepared one of the few comprehensive distillation studies for the application selection of valve and sieve trays compared to random or structured packing. This reference is based on a more comprehensive evaluation of accumulated data by the same authors [137]. Many separate studies have been conducted for trays [138] including bubble caps as well as various packings, but few, if any attempt to establish similar conditions to make a viable comparison as is attempted in References 136, 137. There are four main differences related to capacity and separation [136] when considering ... 

Figure 9-17. Overall comparison of capacity at flood for 24-in. tray spacing with random packing. Reproduced with permission of the American Institute of Chemical Engineers, Kister, H. Z., Larson, K. F., Yanagi, T., Chemical Engineering Progress, V. 90., No. 2 (1994) p. 23 all rights reserved.

Flooding, holdup, and mass transfer rates are highly interdependent and are not simply related. Reissinger and Schroter (1978) state that tray towers in comparison with other types have good efficiencies at 60 nr /m2 hr at frequencies of 60-90/min and amplitudes of 10 mm. Packed towers have about 2/3 the capacities of tray towers. Also in comparison with unagitated towers, which are limited to interfacial tensions below lOdyn/cm, pulsed towers are not limited by interfacial tension up to 30-40 dyn/cm. Some... 

Capacity and Efficiency Comparison Kister et al. [Chem. Eng. Progr., 90(2), 23 (1994)] reported a study of the relative capacity and efficiency of conventional trays, modem random packings, and conventional structured packings. They found that, for each device optimally designed for the design requirements, a rough guide could be developed on the basis of flow parameter L/G (p( /p, )05 (abcissa in... 

Table 6.1 compares the main tray types. The comparison is general and assumes the trays are properly designed, installed, and operated. Sieve and valve trays have comparable capacity, efficiency, entrain-... 

Siemens-Martin furnace-regenerator, 590 Sieve tray extractors, 483 capacity, 484,487 diameters, 483, 487 efliciency. 483.487 pulsed, 478,483,487 sizing example, 486 Sieve trays, 428 assembly in a tower, 428 comparison with other types, example, 431... 

An important feature of the Helix dryer is its compact size. The dryer with an evaporative capacity of about 8400 kg of water/h at air temperature 315 and 82° C at the dryer inlet and outlet, respectively, is about 3.5 m in diameter and 5 m high, and contains about 75 m of tray area. A conventional vibrated fluid bed dryer for a similar application would be about 1.2 m wide and 48 m long [84]. Cost and energy efficiency comparisons, however, are not available. 

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