Petroleum distillation pseudocomponent mixtures

Feed analyses in terms of component compositions are usually not available for complex hydrocarbon mixtures with a final normal boiling point above about 38°C (100°F) (n-pentane). One method of handling such a feed is to break it down into pseudocomponents (narrow-boiling fractions) and then estimate the mole fraction and K value for each such component. Edmister [Ind. Eng. Chem., 47,1685 (1955)] and Maxwell (Data Book on Hydrocarbons, Van Nostrand, Princeton, N.J., 1958) give charts that are useful for this estimation. Once K values are available, the calculation proceeds as described above for multicomponent mixtures. Another approach to complex mixtures is to obtain an American Society for Testing and Materials (ASTM) or true-boiling point (TBP) curve for the mixture and then use empirical correlations to construct the atmospheric-pressure equihbrium flash vaporization (EFV) curve, which can then be corrected to the desired operating pressure. A discussion of this method and the necessaiy charts is presented in a later subsection Petroleum and Complex-Mixture Distillation. 

Before proceeding, we mention sources for a few areas not covered in this chapter. Basic chemical thermodynamics is the subject of Chapter 4. For polymers and their solutions, the Polymer Handbook [1] is an indispensable source, and more on polymer thermophysical properties may be found in two books from AIChE s DIPPR project [2, 3]. The estimation of properties of mixtures described by distillation curves (typically petroleum fractions), or of the pseudocomponents derived from such curves, is covered in the AP7 Technical Data Book [4]. Many molecular data, such as dipole moments and spectroscopic constants, are tabulated in the NIST Chemistry Webbook [5]. 

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