Download Chapter Three Physical Properties 1

Chapter Three
Physical Properties
1- Thermal Expansion
One of the marketing properties that oil products are sold by size not by weight,
that’s why temperature affect the size when the a thing is sold in someplace.
Actually there is no selling at standard temperatures (60o F), but they are sold in
the temperature of the air at the time of selling and that’s why there is a table to
correct the density at the temperature of selling. See figure (2-3) p.47
Thermal Expansion
Is the proportion of increase and decrease in size as a result of increasing or
decreasing temperature? Thermal expansion depends on density as well as
middle boiling degree for oil distilled
From figure (2-3) P.47/ calculate thermal expansion index for each area?
A/ 1- light distilled have higher thermal expansion index than heavy distilled.
2- Throughout the first stage of increasing temperature, Thermal expansion is
low. Then, it increases during the highest heating stages.
3- When two boiling degrees of two distilled, the distilled of more paraffin (API),
has the thermal expansion index higher than oil distilled in Aromatics (API less)
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Freezing or Melting Point
The most important property of airplanes fuel is freezing point that is flying in
higher layers (where pressure is low and temperature is much below zero)
Q/ what is the relation between pressure and temperature for liquid and gas
matter?
A/ Freezing point: - is temperature at which the matter is converted from liquid
to solid at particular pressure.
Melting point: - is the opposite of freezing point definition
Factors that affect the freezing point of Hydrocarbon
a- Increase of carbon atoms in homogeneous group
see table (3-2) P.48
b- Difference in forming Hydrocarbons that have the same normal carbon
atoms. Of these are paraffin that has higher freezing point than branched.
Whenever branching increased, freezing point decreases. See (3-3) P.5
c- Symmetry:Whenever the molecule is more symmetrical, freezing point of the molecule
increases. Most of the times, the effect of the symmetry prevails on Branching
effect.
Q/ what is symmetry, what is its effect?
See.49
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Boiling point and boiling range
Boiling point of a matter is a temperature at which the matter boils. (Converts from liquid
to vapour at air pressure).
For pure matters, boiling degree is a fixed property, and used to detect its quality and
purity. But for mixtures, which are made of one matter, has no boiling degree, but has
boiling range which depends on:a- Number of materials forming it
b- boiling point of each material.
c- vapour pressure at separation or testing
d- The device used to separate the materials
There are known ways to make a survey at boiling range:1- ASTM Standard
2- IP method
These ways give a brief idea about boiling range of the distilled components. But it doesn’t
clarify the amount of true heavy or light components in the distilled.
Q/ What do we mean by IP, ASTM
There is another way which is more efficient to determine boiling range of the distilled, and
this way is known as True Boiling Point.
In this way (Frictional Column is used)
Boiling range has a big importance with many uses of different oil distilled especially for
what relates to valuality , as well as used in designing and controlling distilling devices After
knowing the boiling point how is this range used in calculation. There are many
comparisons :-
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* Average Boiling Point
Such as Volume Average B.P.
Such as weight Average B.P
From this aspect it has the industrial uses which are called Lumping Method and
the aim is to find more real properties for the mixture representing materials
forming it.
1- Boiling point of hydrocarbon homogeneous group increases by the increase
of hydrocarbon atoms.
2- Aromatics have a higher boiling point than naphthenic which has boiling
points higher than straight paraffin
Aromatics > Naphthenic > Paraffin.
Q/ What is the difference between Dew point and Bubble point?
[Which has boiling point higher than branched chains and decreases by the
increase of branching] ?
Q/ what is the difference between Dew point and Bubble point?
A/ P.54
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Melting (dissolving) property
The basic principle to dissolve a matter into the other is whenever ….. of the
dissolver and dissolved , the melting will be more efficient, and efficiency isn’t
quality only but also the molecular weigh. A matter of aromatic composition
dissolves aromatics as well as the small molecules dissolve a little in a dissolver
with higher molecular weight, as it is with gases forming natural gas that
dissolving property decreases by the decrease of carbon.
(C1 less , C2 high)
Importance of Dissolving Property in Oil Industries
For instance, solvent extraction that is used in kerosene refinement and distilled
of lubrication oils to get rid of what they contain of aromatics to improve their
properties. Aromatic compounds has high polarity for there are double
connections, subsequently, solvents with high polarity are used to dissolve
aromatics by high proportion.
Viscosity
Basic property of oil , fuel and lubricating oils and it is the result of inner friction
among the fluid molecules that’s why it depends on size and composition of
these molecules. This friction is a result of attraction power among fluid
molecules which resist fluid molecules and determine its liquidity.
Viscosity is the resistance of the fluid against the flow as a result of the inner
friction, and mathematically as follows
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F/A
T
M=
(
du/dx
)
du/dx
Viscosity is of two kinds:a- Absolute Viscosity
b- Relative Dynamic Viscosity
Absolute Viscosity: is of two kinds
Dynamic and Kinematic viscosity
1- Dynamic viscosity its unit is poise which is the dynamic viscosity that results
by shifting surface of 1 cm by speed of 1cm/sec on a distance of 1 cm from other
surface in parallelism with it under the effect of a force (1 dyne).
Dyne . Sec
Poise =
Cm2
2- Kinematic Viscosity
Its units (stokes, centi stokes): and it represents kinematic viscosity for a liquid
of Dynamic viscosity (1 poise). Kinematics viscosity is the proportion of dynamic
viscosity to the liquid density at the same temperature.
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M
Ɣ=
cm
=
P
sec
cm
represent flow of liquid speed in viscosity devices
sec
b- Relative viscosity:1- Viscosity by grades of [Engler visc] which is measured by Engler device.
2- By using the device [ Sybolt – second Sn] of wide hole or [fural ]device.
3- By using device of [Redwood, second Rn] of big hole.
Relative Dynamic Viscosity
Is the proportion between the dynamic viscosity of the fluid and the dynamic
viscosity of water at (20o) when the standard conditions (1.002 c.p) , the
proportional viscosity and fluid viscosity are equal in number.
Dynamic Viscosity of fluid
Dynamic Viscosity of water
At 20 oC
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The relation Between Viscosity and Temperature
It is of the most important relation for the lubricating oils because of the high temperature
ascending and descending , and the viscosity of oil decreases whenever temperature
increases, and of the most used relations (equations) :Log (Vk + 0.6) = A=B log T
P.60
Viscosity Index
Good oils are that their viscosity doesn’t decreases by the increase of temperature. For
instance:Fluid (L) has low viscosity proportionally.
Fluid (H) has high viscosity index proportionally
See page 62, 63, 64
Oils are divided, according to viscosity index, into three parts :1- HVI Oils of high viscosity index
2- MVI Oils of medium viscosity index
3- LVI Oils of low viscosity index
Q/ what is the classification that is used by cars engineers association.
A/ P.65, P.66 Saybolt classification without mentioning viscosity index and oils have been
divided to heavy oils that their viscosity is measured by 54,4 Co and light oils that their
viscosity is measured by 99 Co .
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Viscosity – Gravity Constant: one of the first indexes that is used to distinguish the quality
of oils:LoG – 1.0752 * log(V-38)
VGC =
10 – Log (V-38)
Density
Is the mass of volumes unit in certain conditions of temperature and pressure. Its unit
(kg/m3) or Ib/ft3
Specific Gravity
Is called proportional density. Proportion between liquid matter density and the density of
the distilled water in the same conditions of pressure and temperature
Sp.Gr =
(at the same condition)
H2O
* One of the benefits of knowing specific gravity and density is to calculate weights by
volume and vice versa.
* Density is considered measurement of quality control
Density or density measurement by the American petroleum institute API-Gr
141.5
API =
- 131.5
Sp - G
Whenever oil is light (less specific weight), API degrees increase and it helps to give a clue
about the price of crude oil.
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Molecular weight
Molecular weight of a compound is group of the sum of atomic weight of atoms
that are in a molecule of a matter.
Note/ revise figure (3-2) P.68
Q/ discuss figure P.69
Refraction Index
Refraction index is the proportion between light speed in a space and its speed
in a matter when the light has the same wave length in space and the matter at
certain temperature.
Refraction index helps to give a clue about hydro carbonic composition for oil
distilled that it increases by the increase of aromatics and decrease by the
decrease of paraffin. Refraction index is used to determine hydrocarbonic
composition of oil distilled by several ways depend on comparison of these oil
properties with heavy hydrocarbons by graphic curves according to relations
used in comparisons. These relations are called
Refractivity Index (specific Refraction)
Refractivity Index =
Specific Refraction =
n- d
2
dd
(n2-1) 1 1 yt
(n2-1) d2
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(Surface Tension and in-between Surface Tension)
Surface tension is a standard for attraction force in the separation surface
between two states of matters, if the surface is between solid and liquid or
liquid and gas, the attraction is called surface tension.
If the surface separates two non- homogeneous liquids, then it is called tensile
interface or in-between surface tension and is measured by:Newton/m and Joule/m
Surface tension for most oil products is in proportionally narrow limits (25-35)
Dyne/cm, thus this property isn’t considered as an essential property to
compare oil products, but an important factor in calculating multiphase flow
and designing flow systems consisting of these phases.
Some non-hydro carbonic materials in oil decreases surface tension especially
soup materials and organic acids, and the surface tension for these materials is
of particular concentration that after this concentration it cannot be influenced
(critical concentration.
((Conductivity of Electricity))
Electricity conductivity of oils is too low and it is affected by impurities even if
they are little. Generally conductivity in oil distilled increases by the increase of
temperature. Temperature effect may be reversed by candles.
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Thermal properties
1- Specific Heat
Is the required heat to raise temperature of mass unit of a matter one degree.
Specific heat is donated with several units but the most common one is British
units (BTu ) (Btu/Ib.oF). The relation between specific heat and temperature for
hydrocarbons is a linear relation. (Specific heat increases by the increase of
temperature). Study figure P. 74 (3-11)
In case of liquid hydrocarbon, specific heat and temperature are not affected
greatly by heat. But concerning gases, specific heat of fixed pressure differs from
specific heat of fixed volume that specific heat of fixed volume is less than it by
the amount of specific gas index.
2- Latent heat of evaporation
There is no change in the tangible heat during the conversion in the matter from
shape to another (like melting
evaporation or vice versa). There is only
absorption or emission of heat called latent heat and is measured at the fixed
pressure which is called enthalpy change.
Q/ What are the latent heat units?
Btu/Ib or KJ/kg
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Latent heat of evaporation is considered the most important type of latent
heats for oil engineering that it decreases whenever temperature increases till it
reaches zero at critical degree.
Latent heat of evaporation: number of English thermal units that are necessary
to evaporate one pound of liquid at its normal boiling degree
3- Heat of Combustion
4- Total Heat Content
Is the quantity of material heat at particular temperature.
∆H = ƩnHip
-
ƩnHiR
And if measured at fixed pressure, it is called enthalpy and has the same units as
latent heat.
Total Heat Content is the sum of tangible, specific heat and non-tangible or
latent heat.
Heat Content is important to calculate thermal balance.
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Vapour pressure
Because of roalt law, vapour pressure is a hydro carbonic mixture of molecular
pressures of all mixture contents. (Rozalt law is applicable at low pressures). But
at high and medium pressures a deviation happened from Rozalt law.
There are common ways to measure absolute (infinite) vapour pressure of the
mixture, and the most common one is (Reed way)
Q/ what is Reed way?
The importance of measuring vapour pressure for mixtures is in measuring the
composition of the liquid and its balanced vapour that they have importance in
designing distillation and evaporation, and condensation devices as well as in
designing safety and storage warehoused and devices that are exposed to high
pressures.
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Smoke Point
Longest flame that result from combustion of chosen distilled measured by mm
without smoke.
Smoke point is used in comparing the hydro carbonic composition for oil
distilled. The distilled which gives water smoke point (little smoke) must contain
paraffin with high proportion and low proportion of aromatics and vice versa.
Smoke point is considered an essential property to compare Kerosene distilled,
which is used in lights, heating, and combustion, as well as kerosene of jet
planes and diesel fuel.
Aniline Point
Lowest temperature at which two equal volumes are mixed from Aniline and the
chosen distilled.
Aniline point decreases whenever the proportion of Aromatics in the distilled
increases.
Q/ Explain the reason for that
A/ p.86
aniline pt * gravity (API)
Diesel Index = D.I =
100
Quality of combustion increases by the increase of paraffin nature for distilled of
gas oil and diesel fuel because paraffin has low thermal resistance. Combustion
quality is measured by choosing octane number of gasoline.
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Flash Point
Lowest temperature at which fuel vapour, in balance with fuel liquid, ignites. .
Flash point is considered of the security tests to prevent exposing fuel to
temperature equal or more than flash point to prevent heat or explosions.
Gasoline has a flash point equal to normal temperature for it contains more
evaporated hydrocarbons at high temperatures.
Cloud, pour and settling points
Cloud Point is temperature at which oil candles are crystalized.
Pour Point is lowest temperature at which oil can be poured (pours in test tube)
Settling Point is temperature at which oil has horizontal shape in test tube.
Pour point has marketing importance. Moving Heavy (dense) oils and crude oil
from the maker (factory) to the consumer is a big problem especially in winter.
Solving this problem depends on how much is the pour point for these products
at air temperature. If the difference is much, used as heating tool, and if the
difference is little, it is used as cheap solvent, like gas oil.
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Crude oil Quality
Density degree of crude oil is denoted by API which is a standard for each determiner
developed by American Petroleum Institution to measure proportional density of several oil
liquids. This standard has degrees and most of its values between 10 – 70 degrees of
heaviness. Heaviness degree of oil equals its proportional heaviness to water in 60
Fahrenheit. Fahrenheit is converted according to the following equation:C = (oF – 32) ÷ 1.8
True oil: - Known as traditional oil and its heaviness degree is 22 API or more, like Saudi
mixture of the most lightness (super light crude oil) has heaviness degree of 44.
Heavy Oil:- dense and viscous oil which has low heaviness degree. The highest approved
degree is 22. Heavy oil cannot be extracted by normal production ways most of it needs
heating or dilution in order to flow in pipes.
More heavy crude oil:- Its heaviness degree is 10 API
Bitumen: - which is known as (oil sands) has several common properties with heavy oil, but
it is more dense and viscous.
Sulfur Content:- Crude oil can be measured by its sulfuric content which is about 1 kilo
and bitter.
Sweet Crude:- has sulfur proportion less than 0,5% , but the bitter crude is the oil that has
proportion of sulfur more than 0,5%
The meaning of API: American Petroleum Institution. Crude oil is classified according to the
origin like west of Texas or Brent, mostly by specific weight or density. Those who make
refinement classify it as sweet or intoxicant.
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Octane Number
Means the resistance of benzene to explosion (auto ignition without a spark,
and the required is to ignite Benzene with (plug) not by the motor.
Auto ignition causes problems in motor like:- 1- Detonation 2- ignition 3Dieseling
The first is the explosion of Benzene after the spark, the second is the explosion
of Benzene before the spark and the third one is as with diesel motor
Ignition: Is the combustion of Benzene before the heat comes out
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Sulfur Content Test
Removing sulfur from crude oil by using oxidation with adsorption.
The existence of sulfur in crude oil makes great challenges concerning negative
environmental, economic effects as well as the equipment may be damaged
while dealing with crude oil (9,3% sulfur) because of the acidic nature,
subsequently this research aims to lessen the level of sulfur in crude oil by five
different ways: extraction by solvents, oxidation, adsorption, , merging oxidation
with extraction by solvents and adsorption by using relatively normal conditions.
Firstly, the efficiency of removing sulfur, by extraction with solvents, from oil
crude process has been studied. Different solvents have been used which are
Acetonitrile. After 30 minutes the efficiency of removal was higher than Acetone
and methanol by 28,5% and proportion of mixing by 3:1 and solvent/oil.
Second way that has been studied is oxidation by Hydrogen Peroxide as a
catalyst. Results have shown that removal efficiency increases by the increase of
temperature (35-60 oC), time of mixing (15 – 60) minute and speed of mixing
(100 – 500) r/sec. Also using Hydrogen peroxide/ formic acid has shown a higher
efficiency than using Hydrogen peroxide/ hydrochloric acid, and the efficiency of
removing sulfur 7,2% and 14,4% and the best condition were 60 oC and speed of
500 r/min and mixing time 60 min
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Electrometric Salt Determination
In order to refine petrol, the proportion of salts must not be more than 50
milligram/liter, but less than this. Some of the salts that exist in petrol are
sodium, calcium and magnesium chlorides and others. Mainly, in refineries, salts
are separated from petrol by pure water, then separation of water from petrol.
Separation of salts from petrol which has much salt by 10-15% of water two or
three times.
Salts are separated from crude oil by electricity or combined units of thermal
chemical units and electrical unit.
And separation process of dissolved salts from oil. Oil refineries use salt
removers to complete crude oil refinement process. Salts are disposed of by
increasing temperature of crude oil to 140 oC after that the injection in salt
removal unit begins. Removal process is done by injecting water and
emulsification breaker to crude oil and then, the mixture is entered to a tank has
poles
Water Content Test
To get rid of emulsions with crude oil, in Iraq, Thermal ways are used to
separate water from crude oil, but these ways are expensive while the
developed world is using new methods like microwave rays instead of heating in
traditional ways. This new technology has been applied on Missan oil because it
is a strong and stable emulsion and difficult to be separated, but this new
technology has succeeded (this new method to break emulsification of water
emulsions in oil).
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9-Sulfur content test
To measure sulfur content in the produced oil and gas
10- Contact angle interfacial tension
This system is used to measure surface tension and interfacial among different t
fluids
11- Mercury injection capillary pressure
This system is used to measure the capillary pressure by the mercury injection
technique at different reservoir conditions
12- Densitometer
Used to measure the density of the gases and fluids at different temperatures
and pressures
13- Liquid chromatography
Necessary to chemical composition of petroleum fluids
14- Gas Chromatography
Necessary for the chemical composition of the hydrocarbon gases
15- PH
16- Viscosity
17- Pour point
18- Flexibility point
19- Freezing point
20- Melting point (by the analyzer)
21- Cloud point
22- Wax Content
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