Page 121 - Characterization and Properties of Petroleum Fractions - M.R. Riazi

QC: IML/FFX
P2: IML/FFX
T1: IML
P1: IML/FFX
14:23
June 22, 2007
AT029-Manual-v7.cls
AT029-03
AT029-Manual
3. CHARACTERIZATION OF PETROLEUM FRACTIONS 101
where ABP is the VABP, MABP, or WABP and x i is the corre-
sponding volume, mole, or weight fraction of component i. VABP and SL are defined in Eqs. (3.6) and (3.7). Once T
is calculated for each case, corresponding ABP is calculated
T bi is the normal boiling point of component i in kelvin. Two from Eq. (3.8). Equations (3.8)–(3.12) calculate values of var-
other average boiling points are CABP (cubic average boiling ious ABP very close to those obtained from empirical plot in
point) and MeABP (mean average boiling point) defined as the API-TDB [2]. The following example shows application of
these equations in calculation of various ABP.
3

1 n 1/3

(3.4) CABP = x vi (1.8T bi − 459.67) + 255.37
1.8 Example 3.1—A low boiling naphtha has the ASTM D 86 tem-
i=1
peratures of 77.8, 107.8, 126.7, 155, and 184.4 C at 10, 30, 50,
◦
MABP + CABP
(3.5) MeABP = 70, and 90 vol% distilled [11]. Calculate VABP, WABP, MABP,
2 CABP, and MeABP for this fraction.
where T bi in Eq. (3.4) is in kelvin. The conversion factors in
Eq. (3.4) come from the fact that the original definition of Solution—From Eqs. (3.6) and (3.7) VABP and SL are cal-
CABP is in degrees Fahrenheit. For petroleum fractions in culated as follows: VABP = (77.8 + 107.8 + 126.7 + 155 +
which volume, weight, or mole fractions of components are 184.4)/5 = 130.3 C = 403.5 K, and SL = (184.4 − 77.8)/
◦
not known, the average boiling points are calculated through 80 = 1.333 C (K)/%. From Eqs. (3.9)–(3.12) various correction
◦
ASTM D 86 distillation curve as temperatures are calculated: T W =−3.3 C, T M = 13.8 C,
◦
◦
T C = 3.2 C, and T Me = 8.6 C. From Eq. (3.8) various av-
◦
◦
T 10 + T 30 + T 50 + T 70 + T 90
(3.6) VABP =
5 erage boiling points are calculated: WABP = 133.7, MABP = --`,```,`,``````,`,````,```,,-`-`,,`,,`,`,,`---
116.5, CABP = 127.1, and MeABP = 121.7 C.
◦
where T 10 , T 30 , T 50 , T 70 , and T 90 are ASTM temperatures at
10, 30, 50, 70, and 90 vol% distilled. ASTM distillation curves
can be characterized by the magnitudes of temperatures and Application and estimation of various boiling points are
overall slope of the curve. A parameter that approximately discussed by Van Winkle [12]. Since the materials boil over a
characterizes slope of a distillation curve is the slope of a range of temperature, any one average boiling point fails to be
useful for correlation of all properties. The most useful type
linear line between 10 and 90% points. This slope shown by of ABP is MeABP, which is recommended for correlation of
SL is defined as
most physical properties as well as calculation of Watson K
T 90 − T 10 as will be discussed later in this chapter. However, for calcula-
(3.7) SL =
80 tion of specific heat, VABP is recommended [12]. In Example
where T 10 and T 90 are the ASTM D 86 temperatures at 10 and 3.1, MeABP is 121.7 C, which varies from 126.7 for the ASTM
◦
90% of volume vaporized. The 10–90 slope, SL, in some refer- D 86 temperature at 50 vol% distilled (T 50 ). However, based on
ences is referred to as the Engler slope and is indicative of a our experience, for narrow boiling range fractions with SL <
variety of compounds in a petroleum fraction. When the boil- 0.8 C/% the MeABP is very close to 50% ASTM temperature.
◦
ing points of compounds are near each other the value of SL As an example, for a gas oil sample [11] with ASTM tempera-
and the boiling range of the fraction are low. For petroleum tures of 261.7, 270, 279.4, 289.4, and 307.2 C at 10, 30, 50, 70,
◦
fractions, WABP, MABP, CABP, and MeABP are correlated and 90 vol%, the MeABP is calculated as 279, which is very
through an empirical plot to VAPB and SL in Chapter 2 of the close to 50% ASTM temperature of 279.4 C. For this fraction
◦
API-TDB [2]. Analytical correlations based on the API plot the value of SL is 0.57 C/%, which indicates the boiling range
◦
were developed by Zhou [10] for use in a digital computer. is quite narrow. Since none of the average boiling points de-
For heavy fractions and vacuum distillates in which distilla- fined here represent the true boiling point of a fraction, the
tion data by ASTM D 1160 are available, they should first be 50% ASTM temperature may be used as a characteristic boil-
converted to ASTM D 86 and then average boiling points are ing point instead of average boiling point. In this case it is
calculated. Analytical correlations for estimation of average assumed that the difference between these temperatures is
boiling points are given by the following equations in terms within the range of experimental uncertainty for the reported
of VABP and SL [2, 10]. distillation data as well as the correlation used to estimate a
physical property.
(3.8) ABP = VABP − T
ln(− T W ) =−3.64991 − 0.02706(VABP − 273.15) 0.6667
3.2.2 Interconversion of Various Distillation Data
(3.9) + 5.163875SL 0.25 Work to develop empirical methods for converting ASTM dis-
ln( T M ) =−1.15158 − 0.01181(VABP − 273.15) 0.6667
tillations to TBP and EFV distillations began in the late 1920s
(3.10) + 3.70612SL 0.333 and continued through the 1950s and 1960s by a large number
ln( T C ) =−0.82368 − 0.08997(VABP − 273.15) 0.45 of researchers [13–18]. All of the correlations were based on
discordant experimental data from the literature. Experimen-
(3.11) + 2.456791SL 0.45 tal ASTM, TBP, and EFV data on which the empirical correla-
ln( T Me ) =−1.53181 − 0.0128(VABP − 273.15) 0.6667 tions are based suffer a lack of reproducibility because there
(3.12) + 3.646064SL 0.333 were no standardized procedures or apparatus available. All
of these correlations were evaluated and compared to each
where ABP is an average boiling point such as WABP, MABP, other by House et al. [19] to select most appropriate methods
CABP, or MeABP and T is the corresponding correction for inclusion in the API-TDB. As a result of their evaluations,
temperature for each ABP. All temperatures are in kelvin. the following methods were adopted in the API Data Book
Copyright ASTM International
Provided by IHS Markit under license with ASTM Licensee=International Dealers Demo/2222333001, User=Anggiansah, Erick
No reproduction or networking permitted without license from IHS Not for Resale, 08/26/2021 21:56:35 MDT