Page 164 - Characterization and Properties of Petroleum Fractions - M.R. Riazi

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144 CHARACTERIZATION AND PROPERTIES OF PETROLEUM FRACTIONS
there are a number of basic parameters that must be known
for a fraction to determine various properties from the boiling point is available, nearly all other parameters can be
determined through mid boiling point and PNA composition
methods presented in this chapter. As more experimental with better accuracy than using only T b and SG. For heavy
data are available for fraction a better characterization of fractions in which T b may not be available, the pseudocom-
the fraction is possible. For example, to estimate sulfur ponent technique can be applied through use of M and PNA
content of a fraction from Eqs. (3.97) and (3.98), the input composition where M may be estimated from viscosity data
parameters of specific gravity, molecular weight, density and if it is not available. As there are many scenarios to estimate
refractive index at 20 C are needed. If experimental values of basic properties of petroleum fractions, use of available data
◦
all these parameters are available a good estimate of sulfur to predict the most accurate characterization parameters is
content can be obtained. However, since normally all these an engineering art which has a direct impact on subsequent
data are not available, M, n, and d 20 should be estimated from prediction of physical properties and eventually on design cal-
--`,```,`,``````,`,````,```,,-`-`,,`,,`,`,,`---
SG and T b . Therefore, a minimum of two parameters that culations. The basic laboratory data that are useful in charac-
are boiling point and specific gravity are needed to estimate terization methods based on their significance and simplicity
the sulfur content. However, for heavy fractions in which are given below:
distillation data are not reported, M should be estimated
from kinematic viscosity at 38 and 99 C(ν 38 and ν 99 ) and 1. distillation data, boiling point
◦
specific gravity through Eq. (2.52). Once M is estimated, 2. specific gravity
n can be estimated from M and SG through Eq. (2.127) and 3. composition (i.e, PNA content)
d is calculated from SG through Eq. (2.123). With the knowl- 4. molecular weight
edge of M and SG all other parameters can be estimated from 5. refractive index
methods presented in Chapter 2. Therefore, at least three 6. elemental analysis (i.e., CHS composition) ◦
◦
parameters of ν 38 , ν 99 , and SG must be known to determine 7. kinematic viscosity at 37.8 and 98.9 C (100 and 210 F)
sulfur content or other characteristics. In a case that only one One can best characterize a petroleum fraction if all the
viscosity data is known, i.e., ν 38 , kinematic viscosity at 99 C, above parameters are known from laboratory measurements.
◦
ν 99 , can be estimated from Eq. (2.61). In this way estimated However, among these seven items at least two items must be
value of M is less accurate than the case that three values of known for characterization purposes. In any case when exper-
ν 38 , ν 99 and SG are known from experimental measurements. imental value for a characterization parameter is available it
We see that again for heavy fractions with knowledge of only should be used instead of predicted value. Among these seven
two parameters (i.e., ν 38 and SG or ν 99 and SG) all basic items that can be measured in laboratory, refractive index and
properties of the fraction can be estimated. Therefore, to specific gravity are the most convenient properties to mea-
obtain the basic characterization parameters of a petroleum sure. Molecular weight especially for heavy fractions is also
fraction a minimum of two parameters are needed. very useful to predict other properties. As discussed in Chap-
If the only information is the distillation curve, then spe- ter 2, for light fractions (M < 300; N C < 22, T b < 350 C) the
◦
cific gravity can be estimated from T 10 and T 50 through Eq. best two pairs of parameters in the order of their character-
(3.17) and Table 3.4. Having T 50 and SG, all other parameters izing power are (T b , SG), (T b , n), (M, SG), (M, n), (ν, SG), (T b ,
can be estimated as discussed above. When only a portion of CH), (M, CH), (ν, CH). The most suitable pair is (T b , SG) and
distillation curve (i.e., T 20 , T 40 , and T 60 ) is available, through the least one is (ν, CH). As it is explained in the next section,
Eq. (3.35) the complete curve can be predicted and from this for heavy fractions three parameter correlations are more ac-
equation T 10 and T 50 can be determined. Therefore, a portion curate. Therefore, for heavy fractions in which boiling point
of distillation curve can also be used to generate all parame- cannot be measured a minimum of three parameters such
ters related to properties and quality of petroleum fractions. as viscosity at two different temperatures and specific gravity
We showed that with the knowledge of PNA composition a (i.e., ν 38 , ν 99 , SG) are needed. For heavy fractions the pseudo-
better characterization of a fraction is possible through pseu- component method is much more accurate than use of bulk
docomponent technique. Therefore, if the composition along properties for the estimation of various properties. Therefore,
TABLE 3.31—Standard test methods for measurement of some properties of liquid petroleum products.
Property ASTM D IP ISO Property ASTM D IP ISO
Aniline Point 611 2/98 2977 Flash Point 93 34/97 2719
Carbon Residue (Ramsbottom) 524 14/94 4262 Freezing Point 2386 16/98 3013
Carbon Residue (Conradson) 189 13/94 6615 Hydrocarbon Types 1319 156/95 3837
Centane Number 4737 380/98 4264 Heating Value 240 12
Cloud Point 2500 219/94 3016 Kinematic Viscosity 445 71/97 3104
Color 1500 196/97 2049 Octane Number (Motor) 2700 236 5163
Density/Sp. Gr. 4052 365/97 2185 Refractive Index 1218
Distillation at Atm. Pressure 86 123/99* 3405 Pour Point 97 15/95 3015
Distillation at Reduced Pressures 1160 6616* Sulfur Content 1266 107/86 2192
Distillation by Gas Chromatography 2887 406/99* Thermal Conductivity 2717–95
Distillation of Crude Oils 2892 8708* Vapor Pressure (Reid) 323 69/94 3007
Viscosity (Viscous Oils) 2983 370/85*
ASTM has test methods for certain properties for which other test methods do not suggest equivalent procedures. Some of these methods
include heat of combustion: D 4809; smoke point: D 1322; surface tension: D 3825; vapor–liquid ratio: D 2533; viscosity temperature chart: D
341; autoignition: D 2155 (ISO 3988). Further test methods for some specific properties are given in the text where the property is discussed.
ASTM methods are taken from Ref. [4]. IP methods are taken from Ref. [85]. Methods specified by * are similar but not identical to other
standard methods. Most IP methods are also used as British Standard under BS2000 methods [85]. The number after IP indicates the year of
last approval. ISO methods are taken from Refs. [24] and [85].

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