Page 275 - Applied Process Design For Chemical And Petrochemical Plants Volume II

264 Applied Process Design for Chemical and Petrochemical Plants

n = Q/[4 d2 (h - hd)0.5] (9 - I)

Q= 5.10 (n) (a) (h - h,,)O-i (9 - 2)

Q= K (11) (a) (h - (9 - 3)
This is considered the basis design for the distributor
[131]. K = 0.16 for average. The hole punch direction has
a strong influence on the value of K. = 0.6 if holes are
Figure 9-8L. Full cone spray nozzle as used punched down [ 1311.
for liquid distribution. Used by permission
of Spraying Systems, Co., Cat. 55. For distributors of any design, including the PAN, it is
important to filter the feed or reflux liquid entering the
distributor to reduce the possibilities of plugging of the
orifice holes. Otherwise, the random plugging will cause
(text continuedjirom page 257) non-uniform distribution onto the packing below. It is
important to avoid leakage around the risers because this
can destroy the liquid distribution pattern [ 1311.
the design must be carefully evaluated [ 1311. For uniform
hole performance all holes must be punched in the same Symbols are used by permission of Bonilla, [ 131 1 :
direction, i.e., top down or bottom up. A = distributor quality Factor
Equation 9-1 can be used to correlate the number of B = distributor quality factor
holes to the liquid head for a specific hole diameter, d: Cf- = vapor capacity factor

Table 9-18
Guidelines for Selection of Liquid Distributors
~~ ~~~ ~~ ~~
Type of Distributor
PAN POH POH
Factor (RTD) (Gravity) (Pressure) NTD SNH VND
__ - -
Uniformity VG VG F VG P P
Solids handling P P F G G VG
Turndown G G G G P P
Ease of installation F F G F VG G
Ease of leveling F G VG F VG F
As redistributor GI,* No2 No No2 No No*
Height requirement M L VL H M H
cost H M L H L M
Residence time H L L M L M
Suitable for large
diameters (>lo ft) P G G G VG G
Leakage potential H3 No No No NO No
At high vapor rates P G G G VG G
At high liquid rates G G G G VG G
At low liquid rates G VG G VG P P
For high-purity
fractionation VG VG P VG P P
Heat transfer G G F G VG G
Liquid feed handing Yes’ No No Yes No Yes
Yes’,* No* No No* No No2
~
Flashing feed handling ~~~~
~ -- ~~ ~-
Key VG = very good, G = good, F = fair, P = poor, H = high, M = moderate, L = low, and VL = Iery low “ho” mean\ that rhc distributor cannot Ilr (I\( d
for the particular factor
‘No significant liquid mixing prowded, however
Wery good if used in conjunction with a chimnry tray
?Leakfree if seal-welded
Reproduced by perniisw)n of The American Inmute of Lhemical Engineen, Bonilla, J A, Chrm bng Pry Vol 89, ho 3 (199s) 0 p 17 nll iiql~t\
reserved