Solving for x : 26, 754 x ¼ 8, 997, 000
x ¼ 336 Btu=lb
From enthalpy tables => 615
F.
Temperature of LGO leaving its stripper = 488
F.
Temperature of Kero leaving its stripper = 359
F.
Overall Tower Heat Balance
Tower Overhead Heat Balances
Balance included by envelope 1 determines the overhead condenser duty. See
Tables 9 and 10.
The overhead condenser duty is 71.360 MMBtu/h; therefore, the heat removed
by intermediate refluxes (pumparound) is 115.717À71.360 = 44.357 MMBtu/h.
The heat balance included in envelope 2 determines the internal reflux from the
top tray.
This is as follows:
Let x be the lb/h of overflow from the top tray. Then the heat balance is as
follows (see also Table 11):
Solving for x ¼
12, 879, 000
121
¼ 106, 438 lb=h
¼ 821 mol=h or 16, 736 GPH:
Check for fractionation (using this chapter’s Appendix 2):
Overflow at 60
F = 16,736 GPH.
Overflow at 255
= 19,029 GPH.
Prod vapor to top tray = 13,125 GPH.
Reflux ratio =1.45.
Table 8 HGO stripper balance
Stream
V/L
API
Wat. K
F
lb/h
Btu/lb
MMBtu/h
In
Feed ex HGO
L
30
11.5
627
26,754
347
9.284
Steam
V
–
–
450
1,838
1,290
2.371
Stripout
L
32
11.5
627
1,390
349
0.485
Total in
29,982
12.14
Out
HGO
L
30
11.5
t
F
26,754
x
26,754x
Steam
V
622
1,838
1,376
a
2.529
Stripout
V
32
11.5
622
1,390
442
0.614
Total out
29,982
3.143 + 26,754x
a
At partial pressure of 36.3 psia
Atmospheric and Vacuum Crude Distillation Units in Petroleum Refineries
171