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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 cm Ɣ = = 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.

At 20 oC

Dynamic Viscosity of fluid Dynamic Viscosity of water

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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 dd 2

(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.

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.

∆H = ƩnHip - ƩnHiR

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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 3-

Dieseling

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