Sieve plate design diameter

Solvent recovery column plate column, diameter 0.6 m, height 6 m, 10 stainless steel sieve plates, design pressure 2 bar, column material carbon steel. 

Valve plates are proprietary designs. They are essentially sieve plates with large-diameter holes covered by movable flaps, which lift as the vapour flow increases. 

A sieve tray-type absorption column is proposed. The design specifies a column 1.8 m diameter, approximately 32 m high, and containing 59 sieve plates. Weak-acid condensate is added to tray 13 and make-up water is added at tray 59 (the top tray). Crossflow-type trays are employed from plates 1 to 13, however, a decreased liquid loading demands reverse flow-type trays for plates 14 to 59. The operating pressure is approximately 950 kPa and the operating temperature range is from 8°C to 65°C. 

After selection of the column internal diameter (the fundamental column specification), the sieve plates must then be designed. This involves a trial and error approach. A preliminary plate design is proposed based upon typical tray configurations, then the hydraulic... 

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. 

For sieve trays, the number of kinetic heads equivalent to the total pressure drop through the plate itself is a function of the ratio of the sieve-hole diameter to the tray thickness and the ratio of the hole area per tray to the active area per tray as shown in Fig. 16-5. This pressure drop for a reasonable sieve-tray design is generally in the range of 1 to 3 kinetic heads, and Fig. 16-12 can be used to choose the most reasonable number to use in preliminary designs Designating the number of kinetic heads obtained from Fig. 16-12 as K.H., the pressure drop due to gas flow through the holes for a sieve tray expressed as liquid head is... 

Plate columns are used for operations requiring a large number of transfer units, high pressure, high gas flow rates and low liquid flow rates, when it is necessary to supply or to remove heat, when solids are present in the liquid (or gas), and when the diameter is greater than 70 cm. They have the ability to handle large variations in gas and liquid flow rates. Mass-transfer data will be presented here for the most common designs— bubble-cap plates and sieve plates. 

An altemative tray design is the sieve-plate tray (see Fig. 7). Sieve-plate trays are much cheaper to fabricate compared to bubble-cap trays since the tray consists of a circular plate with holes drilled through for the passage of vapor. These holes are generally much smaller in diameter than the bubble caps. 

Recall that when we designed distillation columns with the graphical McCabe-Thiele method, we specified the relative flow rates of liquid and vapor to obtain the operating lines. What diameter of column is needed to accommodate the absolute flow rates If the column is too narrow le., the sieve plate area is too small), the liquid will pass over the sieve plate too quickly and not equilibrate with the vapor. If the colunm is too wide, the liquid will not cover the tray completely and the vapor will blow through without equilibrating. 

A common type of distillation contacting device used in refinery applications is the sieve tray. In the early 50 s and for many years before, the bubble cap tray was the mainstay of the distillation field. A sieve tray consists of a flat plate with regularly spaced holes, normally 1/2 to 1 inch in diameter. Liquid flows horizontally across the tray and into a channel, called a downcomer, which leads to the tray below. The sieve tray exhibits good capacity, excellent efficiency, low pressure drop, and good flexibility i.e., it will operate quite efficiently at tower loadings which are 1/2 to 1/3 of design values. 

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