Trays, fractionating types

Process pressure vessel cost. Process pressure vessels are always designed in accordance with the current ASME code. These major equipment items are always cylindrical metal shells capped with two elliptical heads, one on each end. Installation can be either vertical or horizontal. Vertical is generally a fractionation-type column with internal trays or packing, although the smaller-height vertical vessels (less than 15 ft) are mostly two-phase scrubber separators. The horizontal vessel is generally a two- or three-phase separation vessel. 

Trays, fractionating assembly of sieve trays, 428 bubblecap, 428,430-433 capacity, F-factor, 429 capacity, Jersey Critical, 432 capacity, Souders-Brown, 432 cartridge, 428 design data sheet, 429 dualflow, 426 efficiency, 439-456 Linde, 430 ripple, 426 sieve, 428,429 turbogrid, 426 types, 426 valve. 429.430.432 Trickle reactors, 576, 607 Tridiagonal matrix, 407 Trommels, 335... 

The number of trays between draw trays is set rather arbitrarily. Nelson (4) recommends using 3 to 5 trays between the draws. If one employs fractionating type draw trays, this would indicate four trays between draws at the maximum since the draw counts as a tray. If chimney type draw trays are used, one more tray in the section would be required to provide the equal degree of fractionation. 

If a waste contains a mixture of volatile components that have similar vapor pressures, it is more difficult to separate these components and continuous fractional distillation is required. In this type of distillation unit (Fig. 4), a packed tower or tray column is used. Steam is introduced at the bottom of the column while the waste stream is introduced above and flows downward, countercurrent to the steam. As the steam vaporizes the volatile components and rises, it passes through a rectification section above the waste feed. In this section, vapors that have been condensed from the process are refluxed to the column, contacting the rising vapors and enriching them with the more volatile components. The vapors are then collected and condensed. Organics in the condensate may be separated from the aqueous stream after which the aqueous stream can be recycled to the stripper. 

Fractionation Research, Inc. Report of Tests of Nutter Type B Float Valve Tray, July 2, 1964 from Nutter Engineering Co. 

Available in metal only, compared more with tray type performance than other packing materials. About same HETP as Spraypak for available data. Used In towers 24 inches and larger. Shows some performance advantage over bubble cap trays up to 75 psia in fractionation service, but reduced advantages above this pressure or in vacuum service. 

In a contact sulphuric acid plant the secondary converter is a tray type converter, 2.3 m in diameter with the catalyst arranged in three layers, each 0.45 m thick. The catalyst is in the form of cylindrical pellets 9.5 mm in diameter and 9.5 mm long. The void fraction is 0.35. The gas enters the converter at 675 K and leaves at 720 K. Its inlet composition is ... 

Figure 13.41. Efficiencies of some fractionations with several types of trays as a function of vapor factor F = u fp or linear velocity, (a) Data of methanol/water in a column 3.2 ft dia [data of Kastanek, Huml, and Braun, Inst. Chem. Eng. Symp. Ser. 32(5), 100 (1969)]. (b) System cyclohexane/w-heptane in a 4 ft dia sieve column [Sakata and Yanagi, Inst. Chem. Eng. Symp. Ser. 56, 3.2/21 (1979)] valve tray data (Bulletin 160, Glitsch Inc., 1967). (c) Methanol/water [Standart et al., Br. Chem. Eng. 11, 1370 (1966) Sep. Sci. 2, 439 (1967). (d) Styrene/ethylbenzene at lOOTorr [Billet and Raichle, Chem. Ing. Tech. 38, 825 (1966) 40, 377 (1968)]. (e) Ethanol/water (Kirschbaum, Destillier und Rektifiziertechnik, Springer, Berlin, 1969). (f) Methanol/water [Kastanek, Huml, and Braun, Inst. Chem. Eng. Symp. Ser. 32, 5.100, (1969)].

Many books and technical articles deal with our subject. Many of these thoroughly explain beyond any confusion just how any tray-type plate in almost any fractionation column works. Presented here is a slightly different approach that is believed to be a more simple way to understand and apply good practice. 

Campbell s series [5] states that many authors recommend, as do I, the O Connell method for hydrocarbons. You may select the two-film method by entering T. The Fractionation Research Institute (FRI) has for more than 30 years used and proven a much more thorough method called the two-film method, which is equally applicable to both fractionators and absorbers [6], The FRI method accounts for the actual tray internal configuration and fluid dynamics, making it far superior to the O Connell method. I have therefore produced a type of two-film method for determining tray efficiency that has been checked to be within 3% accuracy of hundreds of answers calculated with the FRI method. Called the Erwin two-film method, it is recommended for all types of trays and will also calculate the liquid tray residence time in seconds. This method is included in the three tray computer program executable files in the CD accompanying this book. 

For fractionation column tray efficiency determination, use the alpha ratio (the light key K value divided by the heavy key component K value). Please note that the fractionation column involves both the enriching section and the stripping section, as compared to absorber- or stripping-type columns. 

A demethanizer fractionation tower is frequently positioned first. This tower is often operated at 34 x 105 Pa, with temperatures low enough to obtain liquid methane. This tower is usually a tray-type column, although more recently packed towers have been introduced. The noncondensible gases (hydrogen, nitrogen, and carbon monoxide) and relatively pure methane can thus be separated from the C2 and higher hydrocarbons. 

The hardware design proceeds In two phases primary (basic) and secondary (detailed layout). The primary phase sets column diameter, type of tray, and split of tray area Into bubbling and downcomer areas. This phase also provides a preliminary (and usually close) estimate of tray spacing, number of passes, and other features of tray and downcomer layout such as weir height, fractional hole area, hole diameter, and clearance under the downcomer. These estimates are later firmed up in the secondary phase. 

Figure 6.1 Continued) Common tray types, (c) Sieve tray id) dual flow tray. [Pari e courtesy ofGlitsch, Inc,] [Peal d courtesy of Fractionation Research Inc. (FRI)-l...

Reactive distillation is a technology that simultaneously performs fractional distillation and chemical reaction. Fig. 1 is a schematic representation of a reactive distillation tray column for a reaction of the type... 

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