Page 42 - Characterization and Properties of Petroleum Fractions - M.R. Riazi

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22 CHARACTERIZATION AND PROPERTIES OF PETROLEUM FRACTIONS
TABLE 1.5—Conversion of composition of a crude oil sample from mole to weight and volume percent.
Component QC: IML/FFX mol% T1: IML Molecular weight (M) Specific gravity (SG) wt% vol%
C 2 0.19 30.07 0.356 0.03 0.06
C 3 1.88 44.10 0.508 0.37 0.64
iC 4 0.62 58.12 0.563 0.16 0.25
nC 4 3.92 58.12 0.584 1.02 1.52
iC 5 2.11 72.15 0.625 0.68 0.95
nC 5 4.46 72.15 0.631 1.44 1.98
C 6 (fraction) 8.59 82.00 a 0.690 3.15 3.97
C 7+ (fraction) 78.23 266.00 0.895 93.15 90.63
Sum 100.00 100.00 100.00
a This is molecular weight of C 6 hydrocarbon group and should not be mistaken with M of nC 6 which is 86.2.
Example 1.1—The composition of a Middle East crude 1kW · h = 3600 kJ = 3412.2 Btu = 2.655 × 10 ft · lb f
6
oil is given in Table 1.5 in terms of mol% with known
molecular weight and specific gravity for each component/ Energy per unit mass is called specific energy that may be
pseudocomponent. Calculate the composition of the crude in used to present properties such as specific enthalpy, specific --`,```,`,``````,`,````,```,,-`-`,,`,,`,`,,`---
both wt% and vol%. internal energy, specific heats of reaction, and combustion or
the heating values of fuels. Some of the conversion factors are
Solution—In this table values of molecular weight and spe- given below.
cific gravity for pure compounds are obtained from Chapter 2
3
(Table 2.1), while for the C 6 group, values are taken from 1 J/g = 10 J/kg = 1 kJ/kg = 0.42993 Btu/lb
Chapter 4 and for the C 7+ fraction, values are given by the 1 Btu/lb = 2.326 J/g = 0.55556 cal/g
laboratory. Conversion calculations are based on Eqs. (1.15)
and (1.16) on the percentage basis and the results are also The same conversion factors apply to the units of molar en-
given in Table 1.5. In this calculation it is seen that in terms ergy such as molar enthalpy.
of wt% and vol%, heavier compounds (i.e., C 7+ ) have higher
values than in terms of mol%.
1.7.17 Units of Specific Energy per Degrees
1.7.16 Units of Energy and Specific Energy Properties such as heat capacity have the unit of specific en-
ergy per degrees. The conversion factors are as follows:
Energy in various forms (i.e., heat, work) has the unit of Joule
(1 J = 1N · m) in the SI and ft · lb f in the English system. Val- J −3 J kJ Btu
ues of heat are also presented in terms of calorie (in SI) and 1 ˙ g C = 1 × 10 k˙g C = 1 k˙g C = 0.23885 lb F
˙
◦
◦
◦
◦
BTU (British Thermal Unit) in the English system. There are
two types of joules: absolute joules and international joules, cal Btu J
where 1 Joule (int.) =1.0002 Joule (abs.). In this book only ab- 1 ˙ g C = 1 lb F = 4.1867 ˙ g C
˙
◦
◦
◦
solute joules is used and it is designated by J. There are also
two types of calories: thermochemical and Internationational As mentioned in Section 1.7.13, for the difference in tem-
◦
Steam Tables, where 1 cal (international steam tables) = perature ( T), units of C and K are the same. There-
1.0007 cal (thermochemical) as defined in the API-TDB [47]. fore, the units of heat capacity may also be represented
In this book cal refers to the international steam tables unless in terms of specific energy per Kelvin or degrees Rankine
cal
otherwise is specified. In the cgs system the unit of energy is (i.e., 1 Btu = 1 lb · ◦ R = 1 ˙ g· ◦ C = 1 g ·K ). The same conversion fac-
Btu
cal
l ˙ b· ◦ F
dyn·cm, which is also called erg. The unit of power in the SI tors apply to units of molar energy per degrees such as molar
system is J/s or watt (W). Therefore, kW·h equivalent to 3600 heat capacity.
kJ is also a unit for the energy. The product of pressure and Another parameter which has the unit of molar energy per
volume (PV) may also present the unit of energy. Some of the degrees is the universal gas constant (R) used in thermody-
conversion factors for the units of energy are given as follows: namic relations and equations of state. However, the unit of
temperature for this parameter is the absolute temperature
7
1J = 1N · m = 10 −3 kJ = 10 erg = 0.23885 cal (K or R), and Cor F may never be used in this case. Similar
◦
◦
◦
= 9.4783 × 10 −4 Btu = 2.778 × 10 −7 kW · h conversion factors as those used for the heat capacity given
1J = 3.725 × 10 −7 hp · h = 0.73756 ft·lb f = 9.869 L·atm above also apply to the units of gas constants in terms of mo-
1 cal (International Tables) = 3.9683 × 10 −3 Btu = 4.187 J lar energy per absolute degrees.
= 3.088 ft · lb f = 1.1630 × 10 −6 kW · h
1 cal (thermochemical) = 1 cal = 3.9657 × 10 −3 Btu 1 Btu ◦ = 1 cal = 1.0007 cal(thermochemical)
= 4.184 J = 3.086 ft · lb f = 1.1622 × 10 −6 kW · h lbmol · R mol·K mol·K
= 4.1867 × 10 3 J
1Btu = 1055 J = 251.99 cal = 778.16 ft · lb f kmol·K
= 2.9307 × 10 −4 kW · h
1ft · lb f = 1.3558 J = 0.32384 cal = 1.2851 × 10 −3 Btu Numerical values of the gas constant are given in Sec-
= 3.766 × 10 −7 kW · h tion 1.7.24.

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