Total alkylate ¼ 2,054 BPCD ¼ 506,101 lbs=CD
iC 4 Consumption ¼ 1:34 Â propylene þ 1:15 Â butylene
¼ 1:31 Â 493 þ 1:15 Â 670 ¼ 1,416:3 BPCD
¼ 278,000 lbs=CD:
iC 4 available in FCCU light ends = 48,550 lbs/CD.
Required from other sources = 229,500 lbs/CD or 1,167 BPCD.
A butane isomerizer is included in the process to provide the necessary isobutane
stream. In this process, 50 % wt of the normal butane contained in a saturated
butane stream is converted to isobutane.
Thus, from Table 33, total butanes available from saturate LE are made up as
follows:
Isobutane
670 BPCD
131,695 lbs/CD
=29.2 % wt
Normal butane
1,559 BPCD
318,223 lbs/CD
=70.8 % wt
50 % of the normal butanes are isomerized giving an isomerate 29.2 + 35.4 lbs
isobutane per 100 lbs feed and 35.4 lbs normal butane (Table 34). Feed to the
isomerizer will be 229,500 Ä (0.292 + 0.354) = 355,263 lbs/CD or 528 BPCD iC 4
and 1,232 BPCD of nC 4 .
The combined material balance for alkylation and isomerization is in Table 36.
Table 31 Alkylation unit
feed composition
Component
% vol
BPCD
lbs/Gal
lbs/CD
C 3
11.7
203
4.22
35,980
C 3 –
28.4
493
4.34
89,864
iC 4
14.2
247
4.68
48,550
nC 4
7.1
123
4.86
25,107
C 4 –
38.6
670
5.00
140,700
Total
100.0
1,736
4.67
340,201
Table 32 Alkylate product composition
From propylene
From butylene
% wt
lbs/
Gal
vol
factor
% vol
% wt
vol
factor
% vol
C 5
9.0 5.25
1.71
9.9
4.0
0.8
4.75
C 6
4.0 5.53
0.72
4.16
2.0
0.4
2.37
C 7
68.0 5.73
11.87
68.55
2.0
0.3
1.78
C 8
10.0 5.89
1.69
9.76
80.0 13.58
80.65
C 9 +
9.0 6.8
1.32
7.63
12.0
1.76
10.45
Total 100.0 5.78
17.31
100.0
100.0 16.84
100.0
lbs/Gal = 5.93
Petroleum Products and a Refinery Configuration
109