aTrue boiling point. initial boiling point. cFinal boiling point.

aTrue boiling point. initial boiling point. cFinal boiling point.

Figure 11.2 Boiling curves for crude oil.

The TBP plot of the crude gives an estimate of the amount of each petroleum cut in the crude. As shown in Figure 11.4, the boiling point range of each product from the pipestill is shown on the horizontal lines. For example, the boiling point range of the jet fuel in the crude is 280-460oF. By reading off the volume percentages at these temperatures (17 and 40 vol%, respectively), the yield of jet fuel can be estimated to be about 22% of the crude fed to the pipestill. So a 100,000-b/d (b/d = barrels per day) crude unit should produce about 22,000 b/d of jet fuel when fed this type of crude. Of course, the yields will be different for other crudes with different TBP curves.

The properties of a petroleum stream are not specified in terms of compositions. Instead, properties are used such as 5% point, final boiling point, Reid vapor pressure (RVP), flashpoint, and octane number.

The method for performing quantitative calculations with petroleum fractions is to break them into "pseudocomponents" with each having an average boiling point, specific gravity, and molecular weight. Aspen Plus generates these pseudocomponents given "assay" information about the crude oil.

TABLE 11.2 Comparison of Boiling Point Methods for Crude Oil

Vol% Distilled

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