nC 4 ¼ 1:48
iC 5 ¼ 0:94
Then the relative volatility ϕ = 1.48/0.94 = 1.57.
Using the Fenske equation:
N mþ1 ¼
Log LT key=HY key
ð
Þ D Â HY Key= LT key
ð
Þ W
À
Á Á
Logϕ
15 ¼
Log x=3:8 Â 112:1=108 À x
ð
Þ
ð
Þ
Log 1:57
15 Â 0:196 ¼ Log 112:1x
ð
Þ= 410:4 À 3:8x
ð
Þ
ð
Þ
871 ¼ 112:1x= 410:4 À 3:8x
ð
Þ
x ¼ 104:48 moles=h:
Associated with nC 4 in the bottom product will be an equilibrium amount of iC 4 .
Although small, this will have an effect on the bottom product bubble point and
therefore the tower bottom temperature. The amount of this iC 4 in the bottom
product can be calculated using a similar method as that for the split between nC 4
and iC 5 ; thus the keys for this calculation will be iC 4 and nC 4 . Let x be the moles/h
of iC 4 in the bottom product. Then:
Feed
Dist
Bottoms
iC4
39
x
39 – x
nC4
108
104.48
3.52
Table 2 Full range naphtha composition
Comp
BPSD
lb/gal
Gals/h
lb/h
MW
Moles/h
C2
20
3.42
35
120
30
4
C3
240
4.23
420
1,777
44
40.38
iC4
275
4.70
481
2,262
58
39.0
NC4
735
4.87
1,286
6,264
58
108.0
iC5
915
5.21
1,601
8,343
72
115.87
nC5
1,216
5.26
2,126
11,184
72
155.33
C6
2,170
5.56
3,798
21,114
84
251.36
C7
2,930
5.71
5,128
29,278
100
292.78
Mbpt 224
1,075
6.12
1,881
11,513
106
108.62
239
1,525
6.15
2,669
16,413
109
150.58
260
1,345
6.22
2,354
14,640
115
127.31
276
895
6.26
1,566
9,805
120
81.71
304
895
6.35
1,566
9,946
130
76.51
Total
14,235
5.73
24,911
142,659
1,551.45
Distillation of the ‘‘Light Ends´´ from Crude Oil in Petroleum Processing
205