Page 183 - Applied Process Design For Chemical And Petrochemical Plants Volume II

172 Applied Process Design for Chemical and Petrochemical Plants

Tray Operations Summary and Read Fw = 1.018 from Figure 8-105
Pressure Drop TOP Bottom how = 0.092 (1.018) (3.74/4)2/3 0.0989 0.0989
A. Tray number 20 1 Use W in.-V-notched weir, 2.5 in. from
B. Operating pressure, mm. Hg 75 100 tray floor to bottom of notch. This
C. Operating temperature, "F 60 100 is necessary because of low liquid flow.
D. Vapor flow, lbs/hr 6,565 6,565 b. Static submergence, h,, in. 0.5 0.5
E. Vapor volume, ft3/sec @ c. Caps
operating conditions, V 132.2 105 Modified Dauphine and Cicalese,
F. Vapor density, lbs/ft3 operating [ll, 131 dry cap basis.
conditions 0.0138 0.01735 1. Riser pressure drop, reversal area
G. Liquid flow, gallons/minute, L, 3.74 3.74 greater than riser area.
H. Liquid flow, Ibs/hr., L' 1,515 1,515
I. Liquid flow, ft3/sec @ operating 2.09
conditions 0.00834 0.00776
J. Liquid density, lbs/ft3 @ operating
conditions 50.5 54.2 = 0.06333 0.0633 0.0462
K Superficial vapor velocity, based 2. Reversal and annulus pressure drop
on Tower I.D., ft/sec, 132.2/28.28 4.67 3.7 Riser height > 2.5 in.
L. Vapor velocity based on cap area 1.71
between inlet and outlet weirs, h - o*68 [ 2(5'43)2 (0.0138)1/2 (s)]
ft/sec 132/[28.28 - 2(2.12)1 5.49 4.37 ra 30.5 (7.95) (11.79) 4.95
M. Volume of downcomer: Area top
segment, Perry's Hdbk. 3rd Ed. = 0.043 0.045 0.0322
pg. 32. h/D = 9% in./72 = 3. Rectangular slot dry pressure drop
0.1276, A = 0.03799(6)2 = 2.08 ft2 4.04 4.04 1.73
Lower taper, use h @ % of vert. h' =- 163 [ 13.875 (0.0138)]
taper for estimate. 8/72 = 0.111, 50.5
A = 0.04763(6)2 = 1.71 ft2 Volume
= (2.08) (0.5) + (1.71) (21/12) = 4.04 ft3 = 0.0308 0.0308 0.0231
N. Liquid residence time in downcomer, 4. Total dry cap pressure drop
seconds, (4.04)/0.00834 = 485 485 520 h', = h, + h,, + h,' = 0.0633
0. Throw over downcomer weir + 0.045 + 0.0308 = 0.139 0.1391 0.1015
(sideflow), inches 1.17 1.17 5. Wet cap pressure drop
P. Throw over downcomer weir [ ]
(center flow), min. = - - v PY (3)
li2
Q. Tray layout, actual downcomer 9% 9% As PL a,
width, in. 5% 5%
(
Taper downcomer has 6 in. vertical 132.2 0.0138 9.39
dimension at 9% in. wide. Tapers to =- [ - - )]'I2 =0.33
50.5 5.85
8.40
5% in., 24 in. below tray.
R. Slot velocity: minimum 3.4 /(pc)1/2 From Figure 8-115, C, = 0.16
ft/sec 29 25.9 h, = h,'/CI, = 0.1391/0.16 = 0.87 0.87 0.847
S. Slot velocity: maximum = 12.1/ 6. Check maximum pressure drop
(pc)'l2 = 12.1/(.0138)1/2 and 12.1/ through wet caps:
(0.01735)1/2, ft/sec 103.1 92 h, max. = 0.0633 + 0.045 +
T. Slot velocity: Superficial, u, = (1.5 + 0.25), in. 1.8 1.3
V/& = 132.2/8.40 and 105/8.4 Since h, is less than h, ma., cap is
ft/sec 15.7 12.5 0.K and not blowing under shroud
ring
Pressure Drop, Inches Liquid on Tray Top Bottom Bolles' r&ommendation
a. Height of liquid over weir (straight weir) 7. Riser, reversal, annulus pressure drop
Lg/ (lw)2.5 = 3.74/ (4~12)~.~ 0.1168 +/ar = 5.85/5.43 = 1.073
=
IW/D = 4/6 = 0.667 From Figure 8-114, K, = 0.598