Flash calculations are among the most common calculations required to design and
analyze petroleum processing operations.
Predicting Product Qualities
The following paragraphs describe the prediction of product properties using
pseudo components (mid-boiling point) and assay data. A diesel cut with TBP cut
points 432–595
F on Kuwait crude (Fig. 9) will be used to illustrate these
calculations. The actual TBP of this cut is predicted using the method already
described. The curve is then divided into about six pseudo mid-boiling point
components as described earlier and is shown in Fig. 10.
Predicting the Gravity of the Product
Using the mid-boiling point versus specific gravity curve from the assay given in
Appendix C of this handbook, the SG for each component is obtained. The weight
factor for each component is then obtained by multiplying the volume percent of
that component by the specific gravity. The sum of the weight factors divided by the
100 % volume total is the specific gravity of the gas oil cut. This is shown in
Table 4.
The Prediction of Product Sulfur Content
The prediction of sulfur content is similar to the method used for gravity.
First the TBP curve for the product is determined and split into pseudo boiling
Table 3 Converting TBP to EFV distillation
% Volume Δt (TBP – DRL),
F
ΔT (Flash FRL)/
ΔT (TBP–DRL)
Δt (Flash–FRL),
F
Flash,
F
0
À46
0.2
À9.2
453
10
0
0.4
0
469
20
9
0.38
3.4
482
30
14
0.37
5.2
491
40
13
0.37
4.8
498
50
7
0.37
2.6
507
60
4
0.37
1.5
511
70
0
0.37
0
514
80
À2
0.37
À0.8
523
90
0
0.37
0
531
100
22
0.37
8.1
547
The resulting TBP curves and EFV curves are shown in Fig. 8
Introduction to Crude Oil and Petroleum Processing
23