tion problems. The EFV curve is used for determining phase behavior of liquids and, thus, is usually of interest principally to designers.
Figure 2.1 shows the TBP and atmospheric pressure EFV curves for a typical crude oil. Also illustrated is the planned yield of three distillate products for a process under study. Figure 2.2 shows the ASTM, TBP and atmospheric EFV distillation curves for a typical petroleum fraction.
The complete and definitive analysis of a crude oil, usually called a crude assay, is considerably more detailed than a TBP curve and a whole crude API gravity. A complete crude assay will contain some or all of the following:
1. Whole crude gravity, viscosity, sulfur content, pour point, etc.
2. TBP curve, mid-volume plot of gravity, viscosity, sulfur, etc.
4. Properties of fractions (naphthas, middle distillates, gas oils and residua)—yield as volume percent, gravity, sul fur, viscosity, octane number, diesel index, flash and fire point, freeze point, smoke point, pour point, vapor pressure, etc.
5. Properties of lube distillates (only if the crude is suitable for the manufacture of lube basestocks).
6. Properties of asphalts (only if the residua have suitable characteristics for preparation of asphalts).
7. Detailed studies of fractions for various properties, e.g., octane number versus yield for naphthas or viscosity versus yield for lubestocks.
8. EFV curve run at atmospheric pressure and/or phase diagram, although this is rarely done.
Much of this information is of little use in design work but is of great importance to the refiner or to a crude oil purchaser.
A typical assay of a commercial crude oil is included in the Appendix. This data was developed experimentally and correlated by Humble Oil & Refining Company and is reproduced here with their permission.
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