different types of boiling points/ functional values api ... · pdf filefig:2.10 molal average...

2/16/2015 NPTEL :: Chemical Engineering Petroleum Refinery Engineering

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API gravity Various average boiling points and mid percent corves

Different types of boiling points/ functional values Table:2.1 For narrow boiling cuts (TBP slope less than 2) all above mentioned boiling points

tend to equal.[1,2,6,7]

Average BoilingPoint Physical property for which it is distinct.

Volume Average Used for liquid viscosity, Specific gravity.

Weight Average Critical properties

Molal Average Characterization factor, Thermal Expansion of liquid.

Mean Average Molecular weight, Sp. gravity, Heat of combustion, Sp. heat etc.

Cubic Average For additive properties, viscosities are additive when expressed oncubic average.

Average Boiling Points: To specify certain properties of the fraction 1:Vol. Avg. Based on the boiling temperature of different cuts.VABP

Used for distinguishing physical property like Liquid Viscosity, Specific Gravity. 2. Weight Average Boiling point For Critical Temperature.

% calculation based on weight. Mol. Averagebased on boiling temperature of different mole fraction.(Characterization factor, Thermal expansion of liquid, based upon boiling temperature at different molefraction.)Molal average

t1, t2, t3 are at respective mole fraction.X1, X2, X3 are mole fraction Mean Average Boiling Point



(For Estimating Mol.wt, Sp. Gravity, Sp.heat of fraction.)Mean Avg B.P=(Molal avg. B.P + Cubic avg. B.P)/2Cubic Avg. B.P:

Va= Vol. Fraction Average Boiling Point for a Fraction (summary) five types are defined in the API Technical Data Book :Volume average boling point

Mass average boling point

Molar average boling point

Cubic average boling point

Mean average boling point

Will generally use boiling point at midcumulative yield Interconversion of Boiling points

Calculate slope of Distillation curve of a fraction.ASTM/TBP/EFV SlopesTBP Slope = (t70%– t10%/60)

70% and 10% are volumetric boiling points.

Fig:2.8 Conversion of TBP slope to ASTM on EFV slope[1,2]



CRUDE OIL PROPERTIES These are required for estimating property of cut ranges in the manual method.

Mid percent API Gravity (density ) is drawn along with TBPMid percent Mol. Wt. is drawn along with TBP

Evaluation of crude properties

Calculate Mean average boiling point from TBP slope and correction factor (From graph)

MABP = VABP+ Correction factor

Calculate Characterisation factor (Kw) and API gravity for fractions.Kw is assumed constant for whole crude and its fraction.50% BOILING POINTS OF ASTM : Calculated from the slope of TBP Curve of a crude and its 50%B.P.

For Fractions: Separate IBP and volume percent for crude fractions

Calculate MABP (VABP, SLOPE and Watson Characterization factor)Calculate API of fractionsCalculate Molecular weight of the fractions using graphPlot MID Volume percent vs API gravity and M.W

Mean AVG /Molal Avg BP

Fig:2.9 Mean AVG /Molal Avg BP[1,2]



Fig:2.10 Molal Average Bolling Point [1,2]

50% Boiling Point on ASTM curve :can be calculated from the slope of TBP curve of a crudeand its 50% B.P can be estimated



Fig:2.11 50% Boiling Point on ASTM curve :can be calculated from the slope of TBP curve of a

crude and its 50% B.P can be estimated



Fig:2.12 Relationship between ASTM and TBP 50 volume points [1,2]



Fig:2.13 Characterization factor vs B.P and API gavity [1,2]

Calculation of Molecular weight



Fig:2.14 Calculation of Molecular weight

Fig:2.15 ASTM true boiling point and equillirium flash vaporisation Distillation curves for a



Naphtha kerosine Blend [1,2]

Fig:2.16 D1160 Temperature Difference[F][1,2]


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Fig:2.17 TBP Temperature oF

Crude Oil PropertiesDistillation analysis/Boiling point range

Amount collected from batch distillation at the indicated temperatureMost useful is TBP (True Boiling Point)Standardized tests —ASTM D86, D1160,

API gravity

Standard Conditions (Temperature & Pressure)“Standard conditions” may vary between countries and even states within the US Standard temperature60°F.Other typical values are 14.73 psi & 14.503 psi. Normal conditions

0°C and 100 kPa (32°F and 14.50 psi)Almost exclusively used with metric units


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different types of boiling points/ functional values api ... · pdf filefig:2.10 molal average...

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