Properties of petroleum products

Properties of Petroleum Products

Group No 22

Zahid SirajSp12-BEC-100

Muhammad Irfan Akram Sp12-BEC-048

What is Petroleum?

Definition:“A thick, flammable, yellow-to-black mixture of gaseous, liquid,

and solid hydrocarbons that occurs naturally beneath the earth's surface, can be separated into fractions by fractional distillation.”

Different products of Petroleum:

Most famous products:

Different products of Petroleum:

Other Products: Natural gas,

Liquid petroleum gas (LPG)

Gasoline (also known as petrol)

Naphtha

Kerosene and related jet aircraft fuels

Diesel fuel

Fuel oils

Lubricating oils

Asphalt and Tar

Petroleum coke

Why we need Petroleum Properties?

To check the ignition quality of fuel oil.

To check the combustion quality of fuel oil.

To differentiate between different products of petroleum

To check the stability of oil at different temperature.

Use for selection of the lubricants for the machinery.

Importance of oil Properties:

Properties of Petroleum: Aniline point Flash point Fire Point Smoke point Cloud Point Pour Point Freezing Point Viscosity

Vapor Pressure API Acid Value/Number

Octane Number Calorific Value

Specific Gravity Emulsification

Aniline Point:Definition:

“Aniline point for a hydrocarbon or a petroleum fraction is defined as the minimum temperature at which equal volumes of liquid hydrocarbon and aniline are miscible”.

Aniline point is used to measure the aromatics contents of lubricating oil.

Aniline point and Aromatics contents have inverse relation.

Use to find out the following terms:

Aromatics contents

Diesel Index (Tells about ignition quality of oil)

Cetane Number (Tells about combustion quality of oil)

Aniline Point: Determination of Aniline point:

The temperature at which separation of two phases (Aniline + oil) take place is the Aniline Point.

Aniline + Sample oil

(Equal Volume)

Heated in Beaker on Water bath

Formation of Homogeneous

Mixture

Cooled

Cloudiness

Aniline Point:

Diesel Index Formula:

Diesel index = [ (Aniline point in ºF ) * API Gravity ] 100

Cetane Number Formula:

Cetane Number = Diesel Index 3

Flash Point & Fire Point:

Flash Point:

“It is the minimum temperature at which an oil gives out sufficient vapour to form an inflammable mixture with air and catches fire momentarily flashes when flam is applied”.

Fire Point:

“It is the minimum temp at which the lubricant’s vapours burn constantly for 5 sec when tiny flame brought near.”

Flash Point & Fire Point:

Apparatus Used:

Pensky-Marten’s Apparatus

Flash Point & Fire Point:

Flash point gives idea about: Nature of boiling point diagram of the system

Amount of low boiling fractions present in the liquid fuel

Explosion hazards

Volatility of liquid fuels

Flash point of different liquid fuels

Product Name Flash point Product Name Flash Point

Crude oil -10 to 0 ºC Gasoline -40 to -30 ºC

Kerosene oil 28 to 55 ºC Diesel Greater then 55 ºC

Lube oil 130 to 300 ºC Fuel oil Greater then 66ºC

Flash Point & Fire Point:

Important Points:Flash point = Fire point + 5 to 400 ºC

If

flash point < 140 ºF = Flammable liquids

flash point > 140 ºF = Combustible liquids

In more cases fire point is 5 to 40 ºC is higher then flash point.

The fuels with flash point higher then 66 ºC are regarded as safe for storage and transportation.

Smoke Point

Definition:“It is the maximum

height of flame in mm without smoke formation when the kerosene oil is burned in a

standard lamp under closely control conditions”

Apparatus:

Smoke Point

Why smoke produce ?Due to the following reasons smoke produce:

Smoking is due to the presence of aromatic hydrocarbons.

Paraffin's are desirable in kerosene as it has got the highest smoke point where as aromatics are undesired as it has got lowest smoke point.

Standard smoke point of kerosene is 20 to 30 mm.

Aromatics are hence removed from kerosene to improve smoke point.

Cloud Point & Pour point:

Cloud point

“The cloud point of a diesel fuel is the temperature at which the amount of precipitated wax crystals becomes large enough to make the fuel appear cloudy or hazy.”

Pour Point

“The temperature at which the oil just causes to flow is called the pour point.”

Apparatus

Cloud Point & Pour point:

Important Points: It determines the temperature below which an oil can not be used as a lubricant.

Both indicates the suitability of lubricants in cold conditions and thus must be low.

Lubricants used in a machine working at low temperature should posses a low pour point , otherwise solidification of lubricatns will cause jamming of machine.

Presence of waxes in lubricating oil raise the pour point.

Pour point of an oil can be lowered by lowering the viscosity of the oil which is achived by removing the viscous constituents of the oil.

Cloud Point & Pour point:

Lubricating oil used in the capillary feed system should have low cloud points, otherwise impurities will clog the capillary.

The cloud point has inverse relation with the density as well as the viscosity

of the fuel.

Why Wax formed?“Wax may form because normal paraffins occur naturally in diesel fuel.

As the temperature of the fuel is lowered, these paraffins become less soluble in the fuel and precipitate out as wax crystals.”

Freezing Point:

Definition:“It is the temperature at which the fuel oil freezes completely and

cannot flow at all.”

Importance: It is important in case of aviation gasoline because at high altitude where

low temperature are encountered.

If the freezing point of the fuel tank is not sufficient low then the fuel supply from fuel tank to engine may be impended due to choking of pipe line.

Aviation gasoline should have freezing point blew 60 ºC to avoid the trouble.

Octane Number:

Definition:“ This is the property of gasoline which is used in a spark ignition engine and

expresses its knocking characteristics”.

How we can find ? To determine the octane number of fuel, it is burnt in s standard engine for

the purpose and the knocking is measured by the knockmeter.

This is compared with the standard knockmeter reading of the fuel of different octane number to determine the octane number.

Octane Number:

Importance: High octane number and knocking has inverse relation.

Octane number of gasoline is improved by addition of tetra ethyl lead.

Octane number of hydrocarbon fuels increases in the order n-paraffins – aromatics.

When a gasoline engine is made to operate at high load and low speed, a short of rattling noise may develop from the combustion chamber resulting from unsteady and uncontrolled combustion, this noise is called knocking.

Higher the octane number better is a fuel as maximum permissible power increases with the octane number.

Viscosity:

Definition:

“Internal resistance between layers of oil.”

Important points: It’s a measure of fluid’s resistance to flow.

Viscosity determine the performance of lubricating oil during operation.

A low viscosity oil is thin and flows easily.

A high viscosity oil is thick and flows slowly.

Viscosity and temperature has inverse relation.

Viscosity is usually expressed in Centipoise or Centistoke.

Viscosity:

Apparatus used:

RedWood I Viscometer

RedWood II Viscometer

Engler Viscometer

(Used for Low viscous liquids)

(Used for highly viscous liquids)

(Used for moderate viscous liquid)

Diagram:

Viscosity: Formula:

A and B are constants. And ‘T’ is the time.

Apparatus Value Of ‘T’ (sec)

Value of ‘A’ Value of ‘B’

RedWood I 34 < T > 100 0.0026 1.78

RedWood II T > 100 0.00247 0.50

Engler No range 0.00147 3.74

Emulsification:

Definition:“Some oils mix intimately with water and the mixture is called emulsion which has tendency to collect dirt particles and other foreign matters.”

Importance: The emulsification tendency is undesirable in most application of the oil.

Forming of emulsion in a circulating oil system is undesirable because sticky emulsion and slug’s with oil circulation.

A good lubricating oil should not form emulsion under lubrication condition and even if it forma an emulsion , it should break off very rapidly.

Vapor Pressure:

Vapor pressure is important because:

“With decreased atmospheric pressure at high altitudes, the vapor comes out of the liquid fuel causing vapor locking and difficulty in starting the spark ignition engines. If the vapor pressure of fuel is too low starting the engine and lubricating oil dilution becomes difficult.”

If the vapor pressure is high that means flash point is low resulting in danger of fire and explosion

Lubricants having high vapor pressure will be lost quickly particularly in case of thin film boundary lubrication.

If the vapor pressure is high, vapor occurs in vapors tank and pipeline causing pumping difficulties.

Acid Value Or Number

Definition:“ The number of milligrams of the KOH required to neutralize the free

acid present in 1 gm. of an oil.”

Importance: Determine the acidity of an oil.

Acid value of petroleum products should be less then 0.1.

Increase in acid number indicates oxidation of the oil which will lead to gum and sludge formation besides corrosion.

Calorific Value

Important points: Gross calorific value of petroleum fuels are in the range of 10,000 to 11,300

kcal/kg, the higher figure being for the gasoline and lower for the heavy fuels.

Petroleum products are high in hydrogen contents 11.8 to 14.5 % and hence their net calorific value is less then the gross by 620 tp 760 kcal/kg.

Formula: