are used for this purpose. A graph of these indices is given in Fig. 12. It is selfexplanatory and its application is explained in Table 7.
Flash Points
The flash point of a product is related to its ASTM distillation by the expression:
Flash point ¼ 0:77 ASTM 5 % in
F À 150
F
ð
Þ
(4)
Thus, for the gas oil product in the above example, the flash point will be as follows:
Flash point ¼ 0:77 420 À 150
ð
Þ ¼ 208
F:
Blending Products of Different Flash Points
As with pour points and viscosity, the flash point of a blend of two or more
components is determined by using a flash blending index. Figure 13 gives these
indices. Again the indices are blended linearly as in the case of viscosity. Consider
the following example:
2,000 BPSD of kerosene with a flash point of 120
F is to be blended with 8,000
BPSD of fuel oil with a flash point of 250
F. Calculate the flash point of the
blend (Table 8).
Table 5 Calculating the sulfur content of a cut
Component
Weight factor
Mid-BPt,
F
Sulfur, % wt
Sulfur factor
1
10.3
410
0.2
2.06
2
13.2
460
0.41
5.41
3
17.6
489
0.84
14.78
4
15.2
520
1.16
17.63
5
15.7
550
1.35
21.2
6
11.1
592
1.5
16.65
Total
83.1
77.73
Sulfur % weight ¼
77:7
83:1 Â 100 ¼ 0:935 %wt: actual plant data gave 0:931 %wt:
ð
Þ
Table 4 Calculating the SG of a cut
Component
Volume %
Mid-BPt,
F
S Ga t6 0
F
Weight factor
1
13.0
410
0.793
10.3
2
16.5
460
0.801
13.2
3
21.0
489
0.836
17.6
4
18.0
520
0.844
15.2
5
18.5
550
0.846
15.7
6
13.0
592
0.850
11.1
Total
100.0
83.1
SG of cut ¼
83:1
100 ¼ 0:831
Introduction to Crude Oil and Petroleum Processing
27