International Journal of Scientific Research and Engineering Studies (IJSRES)
Volume 2 Issue 5, May 2015
ISSN: 2349-8862
Characterization Of Nigerian Crude Oil Using ASTM86 Test
Method For Design Of Mini Refinery
Victor Adekunle Adetoro
Sunday Christopher Aduloju
Eton Udeme
Priscilla N. Duru
Adeyemi Adeniji
National Engineering Design Development Institute, Nnewi, Nigeria
Abstract: Some physical and chemical properties of
samples of light Nigerian crude have been measured and
reported in this paper. The crude oil have also been
characterized by fractional distillation; D86 method. The
importance of the physicochemical properties and the
significance of fractional distillation method to industrial
process operations have been discussed.
I.
INTRODUCTION
Crude oil is a naturally occurring mixture, consisting
predominantly of hydrocarbons with other elements such as
sulphur, nitrogen, oxygen, etc. appearing in the form of
organic compounds which in some cases form complexes with
metals [1]. Elemental analysis of crude oil shows that it
contains mainly carbon and hydrogen in the approximate ratio
of six to one by weight [2]. The mixture of hydrocarbons is
highly complex and the complexity increases with boiling
range. The instrumental techniques of chromatography,
ultraviolent and infrared spectroscopy together with mass
spectrometry facilitate knowledge of the detailed hydrocarbon
type composition of crude oil [3].
Over the years the chemical utilization of crude oil and its
refined products has been on the increase globally. As a result
concerted efforts are being made to understand its
composition, structure and properties. This understanding will
result in improved process conditions for improved yield and
quality of products. The net effect is further enhancement of
the utilization of crude oil and its products. Thus studies on
crude oil and its products have utilized several analytical
techniques after fractionation to aromatics and nonaromatics
[4]. Mair and Rossini [5] carried out the isolation of
hydrocarbons in crude oil by fractionation, crystallization, and
solvent extraction as well as the analysis of the fractions. Karr
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and co-workers [6] used the technique of elution
chromatography for the fractionation of virgin crude oils while
Crowley et al. [7] reported hydrocarbon class separation
scheme for crude oil using liquid chromatography glass
capillary chromatography.
Some literature reports [8-13] have utilized different
chromatographic techniques for separation of crude oil, crude
oil fractions, or petroleum products into acid, base, neutral,
saturates and aromatic fractions. In other reports, further
fractionation of the aromatics into monoaromatics, diaromatics
and polyaromatics were carried out [9].
The fractions were characterized using ultraviolent and
infrared spectrophotometry [4], X-ray fluorescence
spectrometry [3] as well as proton and carbon-13 nuclear
magnetic resonance spectrometry [14-15]. The metal contents
of crude oils and its products have also been determined using
methods such as UV-visible spectrophotometry [16] and
atomic absorption spectroscopy (ASS) method [17]. The nonmetal constituents of crude oil and crude oil products, and
especially sulphur, nitrogen and their derivatives have also
been studied [18-21]. These non-metals as well as the metals
constitute the impurities crude oil.
In this paper, the result of physical and chemical
characterization of Nigerian light crude oil is presented. The
crude oil sample analyzed is the Bonny light obtained from
Warri Refinery and Petrochemical Company.
II. METHODOLOGY
A. TEST METHODS
a.
ASTM D86: This is the Standard Test Method for
Distillation of Petroleum Products atAtmospheric
Pressure. This test method covers the atmospheric
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International Journal of Scientific Research and Engineering Studies (IJSRES)
Volume 2 Issue 5, May 2015
ISSN: 2349-8862
b.
c.
d.
distillation of petroleum products using a laboratory
batch distillation unit to determine quantitatively the
boiling range characteristics of such products as
natural gasolines, light and middle distillates,
automotive spark-ignition engine fuels, aviation
gasolines, aviation turbine fuels, I-D and 2-D regular
and low sulfur diesel fuels, special petroleum spirits,
naphthas, white spirits, kerosines, and Grades 1 and 2
burner fuels. The test method is designed for the
analysis of distillate fuels; it is not applicable to
products containing appreciable quantities of residual
material. This test method covers both manual and
automated instruments.
ASTM D 445: This is the Standard Test Method for
Kinematic Viscosity of Transparent and Opaque
Liquids. It covers the determination of the kinematic
viscosity of liquid petroleum productsboth
transparent and opaque, with the exception of
Bitumens by measuring the time of flow of afixed
volume of liquid at a given temperature through
calibrated glass capillary instruments, using "gravityflow."
ASTM D 1298: This is the Standard Practice for
Density, Relative Density (Specific Gravity) or API
Gravity of Crude Petroleum and Liquid
Petroleum.This test method covers the laboratory
determination using a glass hydrometer, of the
density, relative density (specific gravity), or API
gravity of crude petroleum, petroleum products, or
mixtures of petroleum and nonpetroleum products
normally handled as liquids, and having a Reid vapor
pressure of 101.325 kPa (14.696 psi) or less. Values
are measured on a hydrometer at either the reference
temperature or at another convenient temperature,
and readings corrected to the reference temperature
by means of the Petroleum Measurement Tables;
values obtained at other than the reference
temperature being hydrometer readings and not
density measurements. Values determined as density,
relative density, or API gravity can be converted to
equivalent values in the other units at alternate
reference temperatures by means of the Petroleum
Measurement Tables.
ASTM D 2892: This is the Standard Test Method for
Distillation of Crude. This test method covers the
procedure for the distillation of stabilized crude
petroleum to a final cut temperature of
400oCAtmospheric Equivalent Temperature (AET). It
employs a fractionating column having an efficiency
of 14 to 18 theoretical plates operated at a reflux ratio
of 5:1. Performance criteria for the necessary
equipment are specified. This Test Method offers a
comprise between efficiency and time in order to
facilitate the comparison of distillation data between
laboratories. It can also be applied to any petroleum
mixture except liquefied petroleum gases, very light
naphthas, and fractions above 400oC.
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B. TEST PROCEDURE
Sample collection and analysis of oil sample was carried
out in line with recommended procedures of the American
Society of Testing and Materials-ASTM. During sampling all
glassware were rinsed properly with water and properly airdried. The wares were later rinsed with the crude oil to be
sampled before the sample for analysis was collected. Samples
were obtained in triplicates. Also, all the chemical reagents
used in this study were of analytical reagent grade.
The following physical and chemical properties of
samples of crude oils were determined following well
established procedures: API gravity, density, viscosity,
temperature, molecular weight and Watson factor.
The fractionation distillation of each sample was carried
out in a distillation apparatus which consists of the distillation
flask, graduated cylinder, cooling bath and heat source. After
carefully introducing the crude oil into the distillation flask
and making all necessary connections, heat was supplied to
distill the oil. The volume of distillate fraction collected at
each 25oCincrease in temperature was recorded until 370oC
was reached. Then the heating of the flask was stopped to
allow the condenser to drain into the receiver and the volume
of distillate collected was recorded.
III. RESULTS AND DISCUSSION
A. PHYSICOCHEMICAL PROPERTIES
The physicochemical properties of the crude oil and its
fractions are summarized in Tables1-3 and the data in Table1
show that the API gravity of the light crude is above 30owhich
agreed with published data [13].
Parameter
Test
Method
ASTM
D1298
Result
API
Density Molecular
(g/cm3) Weight (g)
Crude oil
32
0.8364
190
Gasoline
88
0.6210
90
Naphtha
81
0.6425
106
Kerosene
48
0.7604
130
Gasoil
35
0.8186
172
Fuel oil
20
0.9016
218
Table 1: Physicochemical properties of crude oil and
fractions
Parameter
Test Method
Result
ASTM D1298
Watson Factor (Crude Oil)
11.6078
Sulphur Content (WT %)
0.37
Water (Vol %)
Nitrogen (ppm)
1000
Pour Point (oC)
43.0
Salt Content (PTB)
4.0
Table 2: Physicochemical properties of crude oil
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International Journal of Scientific Research and Engineering Studies (IJSRES)
Volume 2 Issue 5, May 2015
ISSN: 2349-8862
Cumulative
fraction
Test
Method
ASTM
D445
Viscosity
@40oC,
cSt
Viscosity
@100oC,
cSt
Gasoline
0.9604
0.8047
Gasoline+Naphtha
0.9787
0.8974
Gasoline+Naphtha
1.1018
0.9521
+Kerosene
Gasoline+Naphtha
1.3109
1.3033
+Kerosene+Gasoil
Gasoline+Naphtha
1.7246
1.7040
+Kerosene+Gasoil
+ Fuel oil
Table 3: Viscosity of fractions
API gravity determines the grade or quality of crude oils.
Generally, crude oil samples with API gravity greater than 31
are classified as light crude oils, those with API gravity of
between 22 and 31 are classified as medium crude while those
with API gravity of 20 and less are referred to as heavy crude
oil. A comparison of the value of API gravity obtained for the
crude oil in this study with that of API Standard [22] shows
that, the crude oil obtained from Warri Refinery and
Petrochemical Company is light crude oil. % sulphur content
determines whether a particular crude is sweet or sour. Crude
oil samples are classified as sweet if it sulphur content is less
than 0.5%. Anything greater than 0.5% is termed sour. With
respect to its sulphur content, the crude oil used in this study
was found to be of low sulphur. This crude oil sample can thus
be classified as sweet crude. Sweet crude samples are
generally preferred to sour because it has less
corrosion/pollution potential which leads to increase cost of
production and is therefore more suited for the production of
the most valuable refined products.
Viscosity is a measure of internal friction of a liquid
which is the reluctance of a liquid to flow. It therefore
indicates the flowing ability of Crude oil from one point to
another. The result of this study shows that the crude oil
sample is relatively of low viscosity. Viscosity of petroleum is
of importance in studying the energy loses during production.
Any engineering activities including piping and pipeline
construction require the knowledge of the viscosity of the
crude oil to enhance transportation. Viscosity also plays an
important role in reservoir simulations as well as in
determining the structure of liquids. Therefore, the low
viscosityobtained for the crude oil blends indicates that the
sample can easily flow when transported trough pipes thus
making for easy transportation.
The values for water and % nitrogen contents were also
appreciably low in the sample. A knowledge of water and %
nitrogen contents content of any crude oil is important in the
refining, purchase and sales of crude oil because corrosion
problems associated with these parameters. The low water and
% nitrogen contents of the crude oil sample also show that it is
of high value. Pour point of a petroleum specimen is an index
of the lowest temperature of its utility for certain applications.
The pour point value of the sample is low and indicates that
the oils can easily be utilized under low temperature
conditions.
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Salt content and acid number are important index for
refining operations. High values of any of these parameters
indicate high corrosion tendency of crude oil. The values of
these parameters obtained for the crude oil sample show that it
possesses very low corrosion potentials.
Heavy metals are often found to be part of crude oil
samples. Possible sources of trace metals in crude oil are:
through incorporation and diagenesis of metal complexes of
the original biological materials; through incorporation into
the organic matrix during diagenesis of the biological
materials in the source rocks either from clay minerals or
interstitial aqueous solution; through an aqueous phase during
primary and secondary migration and from formation waters
or reservoirs’ rock minerals. The levels of most of the trace
elements obtained in this study were generally low. This
agrees with reports that light crude oil samples usually contain
relatively low trace metal contents compared to the heavy
crudes.
The final properties of the finished products depend on
the properties of the source crude as well as the process
conditions and final treatments.
B. FRACTIONAL DISTILLATION
The experimental data from fractional distillation of the
crude oil sample are also presented in Tables 4-10. The data
clearly shows that the crude oil sample yielded a greater
proportion of light fractions (naphtha).
In a petroleum refinery the physical and chemical
operations are integrated, and both atmospheric and vacuum
distillation processes are involved. Thus the products are
expected to be more in number and to show a wider range than
obtained in this study. However, the present result show that
the product distribution of atmospheric fractional distillation
of crude oil is a function of the nature of the crude oil. The
boiling point of the distillate fractions increases as the volume
percent of the fraction increases. Moreover, as expected,
Gasoil has a higher boiling point than kerosene which in turn
has a higher boiling point than gasoline for all the fractions
collected.
Parameter
Test Method Result
Crude Assay ASTM
D2892
Fractions
Temp. Range Yield
(oC)
(%)
Gases
<35
16.9
Gasoline
35-130
12.0
Naphtha
130-150
5.8
Kerosene
150-250
20.4
Gasoil
250-300
14.0
Fuel oil
300-370
17.1
Bottoms
>370
13.0
Losses
0.8
Table 4: Fractional Distillation of crude oil
Crude
Test Method Result
Recovery ASTM D86
Crude oil
Temperature Yield
(oC)
(%)
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International Journal of Scientific Research and Engineering Studies (IJSRES)
Volume 2 Issue 5, May 2015
ISSN: 2349-8862
Fractions
Recovery
Gasoline
Fractions
Recovery
Naphtha
Fractions
Recovery
Kerosene
Fractions
Recovery
Gasoil
144
10
170
20
216
30
258
40
290
50
340
60
385
65
Table 5: Crude oil recovery
Test Method Result
ASTM D86
Temperature Yield
(oC)
(%)
88
20
100
40
108
50
118
60
132
70
162
80
262
90
Table 6: Gasoline recovery
Test
Result
Method
ASTM
D86
Temperature Yield (%)
(oC)
158
20
180
40
192
50
208
60
224
70
244
80
280
90
300
94
Table 7: Naphtha recovery
Test
Result
Method
ASTM D86
Temperature Yield
(oC)
(%)
158
20
180
40
192
50
208
60
224
70
244
80
280
90
300
94
Table 8: Kerosene recovery
Test Method Result
ASTM D86
Temperature Yield
(oC)
(%)
242
20
258
40
264
50
272
60
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Fractions
Recovery
Fuel oil
284
300
336
340
Table 9: Gasoil recovery
Test Method Result
ASTM D86
Temperature
(oC)
302
322
338
352
372
Table 10: Fuel oil recovery
70
80
90
92
Yield
(%)
20
40
50
60
64
Figure 1: Variation of yield of fractions against temperature
IV. CONCLUSION
The result of this study has shown that the crude oil
sample obtained from Warri Refinery and Petrochemical
Company contains low level of sulphur. The sample is also of
light crude oil category grade. Therefore, it can be classified
as light-sweet crude oil. The low values of viscosity obtained
for the sample indicate that, this oil sample can flow easily.
This makes it easy for transportation through pipelines without
the necessary addition of diluents at regular intervals often
associated with heavy crude oil samples. On the whole, the
low levels % of water, salt contents and pour point observed
for the oil sample coupled with other physiochemical
parameters show that, the crude oil has characteristics which
enhance its preferences inthe oil market and refinery
operations.
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International Journal of Scientific Research and Engineering Studies (IJSRES)
Volume 2 Issue 5, May 2015
ISSN: 2349-8862
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