Page 220 - Applied Process Design For Chemical And Petrochemical Plants Volume II

Distillation 209

Table 8-23 Turndown: It is proposed by Klein [201] that the oscilla-
Closed and Open Loss Coefficients for Dry Tray tory motion of the valve accounts for the greater turn-
Pressure Drop Equations 8-314 and 8-315 down of a valve compared to other tray-valve designs. The
... . turndown can be controlled by the number of “working”
.... Tray deck thicknesses of: ~ or oscillating valves on the tray, or by changing the uni-
._.
.
0.134 in. 0.104 in. 0.074 in. formity of weight of the valves per tray or the valve design
Orifice type (10 gage) (12 gage) (14 ?REF) to obtain daerent velocities through different valves on
........ ... __ . . ___ ... .. .. -
- the same tray.
K,
Flat 6.154 6.154 6.154 Beyond point B on the diagram, the pressure drop for
Venturi 3.07’1 3.077 3.077 the tray increases as the vapor rate increases. Use Equation
Kl
- 8-314 or 8-313 to determine the dry tray pressure drop, AP,
Flat 0.821 0.931 1.104 in. liquid, Bolles [203] per Klein [201]:
Venturi 0.448 0.448 0.448
............ . ... .....
Used by permission, Chm. Eng., Klein, G., May 3, (1982), p. 81; all rights For closed valves: hh = K, (&/PI) b2, in. liquid (8 - 314)
reserved.
For open dves: hh = K,, (p&) vh2, h. liquid (8 - 315)
Table 8-24 where y., = vapor velocity through holes, ftlsec
Common Materials Used for Distillation Valves hh = dry tray pressure drop, in. tray liquid
........ .~ . . pi - liquid density, Ib/fv3
Metals Weight, lb/ft3 pv = vapor density, lb/ft3
. .......... . .....
Carbon steel 490
Type 304 Stainless Steel 50 1 Aerate&Trql Liquid Presswe Drsfj
Type 316 Stainless Steel 501
Type 310 Stainless Steel 501 Klein [201] has developed the correlation based on
Chrome Stainless Steel, 400 series 484 published data of others (his citations) as shown in Figure
Monel, 400 551 8-149. Because the method of aeration between sieve trays
Nickel 555 [2053 and valve trays is different [201], the same aeration
Aluminum 170
........ . . . - _. ._ .. - -. . . correlation cannot be used, because valve trays have lower

Figure 8-149. Correlation for aerated-tray-liquid pressure drop developed from published data for various valves. Note: $ = relative froth den-
sity. Reference numbers are from original article 12011. Used by permission, Klein, G. F., Chem. Eng. V. 89, No. 9 (1982), p. 81; all rights resewed.