Page 214 - Characterization and Properties of Petroleum Fractions - M.R. Riazi

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194 CHARACTERIZATION AND PROPERTIES OF PETROLEUM FRACTIONS
4.6. Repeat Problem 4.5 for the gamma and exponential dis-
tribution models to QC: —/— T1: IML 21:30 (crude number 6). In constructing this figure the mid-
volume points may be used for the specific gravity. De-
a. find the coefficients of Eq. (4.31): η, α, and β in termine the distribution coefficients in Eq. (4.56) for T b
Eq. (4.31) for M and T b . and SG in terms of x cv and compare with the experimen-
b. estimate SG distribution based on exponential model tal values. Also estimate crude sulfur content.
and constant K W approach. 4.15. Show how Eqs. (4.104), (4.105), and (4.106) have been
c. calculate mixture M, T b , and SG and compare with derived.
experimental data. 4.16. As it will be shown in Chapter 7, Lee and Kesler have
d. make a graphical comparison between predicted dis- proposed the following relation for estimation of vapor
tributions for M, T b , and SG from Eq. (4.56) as ob- pressure (P vap ) of pure compounds, which may be ap-
tained in Problem 4.5, gamma and exponential mod- plied to narrow boiling range fractions (Eq. 7.18).
els with each other and experimental data.
4.7. For the C 7+ of Problem 4.5 find distributions of M, T b , lnP r vap = 5.92714 − 6.09648/T br − 1.28862 ln T br
and SG assuming: 6
+ 0.169347T + ω 15.2518 − 15.6875/T br
br
a. Only information available are M 7+ = 142.79 and 6
SG 7+ = 0.7717. − 13.4721 ln T br + 0.43577T br
b. Only information available is M 7+ = 142.79. vap vap
c. Only information available is SG 7+ = 0.7717. where P r = P /P c and T br = T b /T c in which both T b
d. Graphically compare predicted distributions from and T c must be in K. Use the continuous mixture ap-
parts a, b and c with data given in Table 4.28. proach (Section 4.7) to predict distribution of vapor
e. Estimate M 7+ and SG 7+ form distribution parameters pressure at 311 and 600 K for the waxy crude oil in
obtained in parts a, b and c and compare with the Table 4.2 and graphically show the vapor pressure dis-
experimental data. tribution versus cumulative mol% and carbon number.
4.17. Minimum information that can be available for a crude
4.8. Using the Guassian Quadrature approach, split the C 7+ oil is its API or specific gravity. A Saudi light crude has
fraction of Problem 4.7 into three pseudocomponents.
Determine, x m , M, T b , and SG for each component. Cal- API gravity of 33.4 (SG = 0.8581), and experimental data
culate the mixture M and SG from the three pseudocom- on boiling point and specific gravity of its various cuts
ponents. Repeat using carbon number range approach are given in the following table as given in the Oil and
with 15 pseudocomponents and appropriate boundary Gas Journal Data Book (2000) (p. 318 in Ref. [8]).
values of M i .
4.9. For the C 7+ fraction of Problem 4.5 estimate total sulfur Vol% SG T b , K SG (calc) T b , K (calc)
content in wt%. 23.1 . . . 370.8 ? ?
4.10. For the waxy oil in Table 4.2 present the oil in six 23.1 0.8131 508.3 ? ?
groups as C 2 –C 3 ,C 4 –C 6 ,C 7 –C 10 ,C 11 –C 20 ,C 21 –C 30 , and 8.5 0.8599 592.5 ? ?
C 31+ . Determine M and SG for each group and calculate 30.2 0.9231 727.5 ? ? ? ?
1.0217
15.1
. . .
M and the API gravity of the oil. Compare estimated
M from the six groups with M calculated for the crude
based on the detailed data given in Table 4.2. a. Using the minimum available data (API gravity), es-
4.11. Use the crude assay data for crude number 7 in Table 4.3 timate values of T b and SG in the above table and
to compare with given experimental data graphically.
a. determine T b and SG distributions. b. Similar data exist for a Saharan crude oil from Algeria
b. estimate T b for the residue based on the distribution (page 320 in Ref. [8]) with API gravity of 43.7. Con-
found in Part a. struct T b and SG distribution diagram in terms of cu-
c. estimate M for the residue from T b in Part b and mulative volume fraction.
SG. 4.18. Similar to the continuous mixture approach introduced
d. estimate M for the residue from viscosity and SG and in Section 4.7, calculate vapor and liquid product distri-
compare with value from c. butions for flash distillation of the same crude at 1 atm
◦
e. Determine distribution of sulfur for the crude and and 400 C. Present the results in a fashion similar to
graphically evaluate variation of S% versus cumula- Fig. 4.26 and calculate the vapor to feed ratio (φ).
tive wt%. 4.19. Repeat Problem 4.18 but instead of Eq. (4.120) for the
f. Estimate sulfur content of the crude based on the pre- vapor pressure, use the Lee–Kesler correlation given in
dicted S% distribution. Problem 4.16. Compare the results with those obtained
4.12. For the crude sample in Problem 4.8 find distribution of in Problem 4.18 and discuss the results.
melting point and estimate average melting point of the --`,```,`,``````,`,````,```,,-`-`,,`,,`,`,,`---
whole crude.
4.13. Estimate molecular weights of SCN groups from 7 to REFERENCES
20 using Eqs. (4.91) and (4.92) and compare your re-
sults with those calculated in Example 4.6 as given in [1] Pedersen, K. S., Thomassen, P., and Fredenslund, Aa.,
Table 4.10. “Characterization of Gas Condensate Mixtures,” C 7+ Fraction
4.14. Construct the boiling point and specific gravity curves Characterization, L. G. Chorn and G. A. Mansoori, Eds., Taylor
for the California crude based on data given in Table 4.3 & Francis, New York, 1989, pp. 137–152.

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