G f = Mass velocity of vapor at flood in lb/hÁsqft of bubble area.
K r = 1,100 for a 24
00 tray spacing.
The largest diameter will always be below the bottom pumparound in terms of
the vapor load. For a quick estimate let the bubble area be 80 % of the total tower
diameter.
Below Bottom Pumparound Loading
Assume bottom pumparound returns to tower at 300
F.
Total PA duty = 17,740,000 Btu/h.
Enthalpy at 627
F = 347 Btu/lb.
Enthalpy at 300
F = 140 Btu/lb.
The lb=h of the PA stream is
17, 740, 000
207
¼ 85, 715 lb=h or 11, 774 GPH
GPH of unstripped HGO product = 3,668.
GPH of overflow = 23,990.
Table 12 Heat balance over envelope 3
Stream
V/L
API Wat. K
F
lb/h
Btu/lb
MMBtu/h
ENV 3
IN
Heat in crude
V+L
–
379,575
175.939
Steam
V
450 33,968
1,290 43.819
Tray34 o/flow
L
46.3
12
367 x3
191 191x3
Total in
413,543 + x 3
219,758 +
x 3
Out
O/flow to tray 34 V
46.3
12
370 x 3
302 302x 3
Vapor to tray 34
V
62.5
12
370 111,510
320 35.683
Steam to tray 34
V
370 33,968
1,253
a
42.562
LGO prod
L
36.3
11.5
488 44,226
255 11.278
HGO prod
L
30
11.5
615 26,754
336 8.989
Residue
L
13
11.5
704 197,085
378 74.498
Top PA
26.614
Bot PA
17.743
Total out
413,543 + x 3
217.367 +
302x 3
a
Steam at the partial pressure of 18.3 psia
Atmospheric and Vacuum Crude Distillation Units in Petroleum Refineries
177