Page 194 - Applied Process Design For Chemical And Petrochemical Plants Volume II

Distillation 183

Figure 8-131. Weeping correlation for sieve trays
with downcorners. Used by permission, Hugh-
mark, G. A. and O’Connell, H. E., The American
institute of Chemical Engineers, Chevn. Eng.
Prog. V. 53. (1953, p. 127M, all rights resewed.

0 Hutchinson 11

Figure 8-132. Weeping sieve trays. Used by permission,
Smith, B. D., Design of Equilibrium Stage Processes,
0 1 .o 2.0 3.0 4.0 Chapter 15 by J. R. Fair, McGraw-Hill Book Co. (1963), all
hlo-hw+how, in. of liquid rights resewed.

Determine C, from Figure 8-129 [ 1931. Note that deter- Note that if an inlet tray weir is used, the (h, + how)
mining froth density is by experiment and/or best judg- group is replaced by the corresponding (hw’ + how‘) cal-
ment based on similar or related systems. Usually 4 I 1.0 culated for the inlet weir using the same algebraic rela-
to 0.50. The method checks literature and industrial tests tions.
about 215%.
Free Height in Downcomer
Pressure Drop through Downcomer, &
-
F = sf + h, - Hd (8 270)
Calculate as for bubble cap tray.
Minimum Vapor Velocity: Weep Point
Liquid Backup or Height in Downcomer
The “weep point” is considered to be the minimum
Hd= ht + hw + how + A + & (8-269) vapor velocity that will provide a stable tray operation, pre-