2 replies to this topic

[ktrone]

Can anyone explain ASTM distillation? I get confused when I encounter 10% ASTM distillation and 50% distillation? What is the basic difference between ASTM,TBP,EFV?

[kkala]

Explanations can be found in W. L. Nelson's "Petroleum Refinery Engineering" (McGraw-Hill, 1958), mainly in Chapter four, "Evaluation of oil stocks". Sufficient info for these lab curves can be obtained from relevant books. In bief:
1. ASTM distillation for gasoline, naphtha, kerosene (D86), or natural gasoline (D216), or gas oil (D158), concerns heating 200 cm3 (*) of the oil product & condensing the produced vapor(rate of 8-10 cm3/min). Vapor temperature is recorded for each 20 cm3 of collected distillate. Total % volume distilled is plotted against temperature, not representing actual boiling point of indicated (in the plot) fraction.
(* 100 cm3 reported elsewhere).
2. True-Boiling-Point distillation is using a fractionating lab column with reflux, distilling 250-2000 cm3 of liquid in total, mainly crude oil. Resulting plot shows total % volume distilled versus actual boiling point. Every crude of given specific (thus API) gravity has more or less same TBP distillation curve.
Specific gravity (sg) of collected distillate can be measured during experiment and plotted against % volume distilled (sg mid percent curve). Same can be done for other (additive) properties.
3. Equilibrium or Flash Vaporization heats continuously flowing oil to some temperature, then separates it from the vapor produced. A plot of percentage vaporisation is created versus changing oil temperature, not representing actual boiling point of indicated fraction.
4. TBP distillation curve looks most useful. Semi-fractionating distillations (Hempel, ASTM D-285) manage to produce curves close to TBP distillation curve.
5. Subject needs further study - any comments/ additions to the above are welcomed.

[mbeychok]

htrone:

For equations and explanation of flash vaporization of a single component liquid as well as a multicomponent liquid, see this article in the online Citizendium encyclopedia:

click here ==> Flash evaporation