Page 122 - Characterization and Properties of Petroleum Fractions - M.R. Riazi

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102 CHARACTERIZATION AND PROPERTIES OF PETROLEUM FRACTIONS
as the best method: Edmister–Pollock [14] for ASTM to TBP,
Edmister–Okamoto [15–17] for ASTM to EFV, and Maxwell TABLE 3.2—Correlation constants for Eq. (3.14).
ASTM D 86
a◦
for conversion of TBP to EFV [19]. Most of these correlations Vol% a b range, C
0
were in graphical forms and inconvenient for computer appli- 10 0.9177 1.0019 20–320
0.5564
1.0900
35–305
cations. Later, Arnold computerized these graphical methods 30 0.7617 1.0425 50–315
through a set of nth order polynomials [20]. Correlation to 50 0.9013 1.0176 55–320
convert ASTM D 2887 (SD) to ASTM D 86 were first developed 70 0.8821 1.0226 65–330
by Ford using multiplier regression analysis [21]. In the mid 90 0.9552 1.0110 75–345
0.8177
75–400
95
1.0355
1980s Riazi and Daubert [22] developed analytical methods Source: Ref. [22].
for the conversion of distillation curves based on the general- a Temperatures are approximated to nearest 5.
ized correlation for hydrocarbon properties given by Eq. (2.2).
These methods were adopted by the API in the fifth edition of lation curve is available then ASTM curve can be estimated as
API-TDB-88 [2] to replace the previous methods. Continued 1/b
1
interests from the petroleum industry for these conversion (3.15) ASTM D 86 = (TBP) 1/b
methods led to development of further methods. The latest a
methods for the conversion of distillation curves were devel- where constants a and bare given in Table 3.2 as for Eq. (3.14).
oped by Daubert in mid 1990s [23] through modifying Riazi–
Daubert correlations. In this section the API methods (Riazi– 3.2.2.1.2 ASTM D 86 and EFV Conversions—Application
Daubert and Daubert) for conversion of distillation data are of Eq. (2.13) to this type of conversion gives
presented, which are also recommended and used in other (3.16) EFV = a(ASTM D 86) (SG) c
b
references and industrial software [24, 25].
where constants a, b, and c were obtained from more than 300
3.2.2.1 Riazi–Daubert Method data points and are given in Table 3.3. Equation (3.16) was
Riazi and Daubert methods for the interconversion of vari- evaluated with more than 300 data points from 43 different
◦
ous distillation data are based on the generalized correlation samples and gave AAD of 6 C, while the method of Edmister–
◦
for property estimation of hydrocarbons in the form of Eq. Okamoto [15] gave an AAD of 10 C [22, 26].
(2.38). Available distillation temperature and specific gravity In using these equations if specific gravity of a fraction is
of the fraction are used as the input parameters to estimate not available, it may be estimated from available distillation
the desired distillation data in the following form [22]: curves at 10 and 50% points as given by the following equa-
tion:
b c
(3.13) T i (desired) = a T i (available) SG b c

(3.17) SG = aT T
10 50
where T i (available) is the available distillation temperature where constants a, b, and c for the three types of distillation
at a specific vol% distilled and T i (desired) is the desired distil- data, namely, ASTM D 86, TBP, and EFV, are given in Table
lation data for the same vol% distilled, both are in kelvin. SG 3.4. Temperatures at 10 and 50% are both in kelvin.
is the specific gravity of fraction at 15.5 C and a, b, and c are
◦
correlation parameters specific for each conversion type and 3.2.2.1.3 SD to ASTM D 86 Conversions—The equation
each vol% point on the distillation curve. For example, if this derived from Eq. (3.13) for the conversion of simulated dis-
equation is used to convert ASTM to EFV at 10%, T i (available) tillation (ASTM D 2887) to ASTM D 86 distillation curve has
is ASTM temperature at 10% and T i (desired) is the EFV tem- the following form:
perature at 10% and constants a, b, and c are specific for this
b
conversion type at 10% of volume vaporized. (3.18) ASTM D 86 = a(SD) (F) c
where constant F is a parameter specifically used for this type
3.2.2.1.1 ASTM D 86 and TBP Conversion—If distillation of conversion and is given by the following equation:
data available are in the form of ASTM D 86 and desired dis- 0.05434 0.6147
tillation is TBP, Eq. (3.13) can be used, but for this particular (3.19) F = 0.01411(SD 10%) (SD 50%)
type of conversion value of constant c for all points is zero in which SD 10% and SD 50% are the SD temperatures in
and the equation reduces to kelvin at 10 and 50 wt% distilled, respectively. Parameter F
(3.14) TBP = a(ASTM D 86) b calculated from Eq. (3.19) must be substituted in Eq. (3.18) to
estimate ASTM D 86 temperature at corresponding percent
where both TBP and ASTM temperatures are for the same point expressed in volume basis. Equation (3.18) cannot be
vol% distilled and are in kelvin. Constants a and b at various
points along the distillation curve with the range of applica- TABLE 3.3—Correlation constants for Eq. (3.16).
tion are given in Table 3.2. ASTM D 86
a◦
For a total of 559 data points for 80 different samples, Eq. Vol% a b c range, C
(3.14) gives an average absolute deviation (AAD) of about 10 0 2.9747 0.8466 0.4209 10–265
0.1287
0.9511
1.4459
60–320
5 C, while the Edmister–Pollock method [14] gives an AAD 30 0.8506 1.0315 0.0817 90–340
◦
of about 7 C. Generally predictions at 0% give higher errors 50 3.2680 0.8274 0.6214 110–355
◦
and are less reliable. Details of evaluations are given in our 70 8.2873 0.6871 0.9340 130–400
previous publications [22, 26]. Equation (3.14) can be easily 90 10.6266 0.6529 1.1025 160–520
reversed to predict ASTM from TBP data, but this is a rare 100 7.9952 0.6949 1.0737 190–430
Source: Ref. [22].
application as usually ASTM data are available. If TBP distil- a Temperatures are approximated to nearest 5.
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