Pharos University
Faculty of Engineering
Petrochemical Department
‫جامعه فاروس‬
‫كلية اهلندسة‬
‫قسم البرتوكيماوايت‬
PE 330 ENERGY CONSERVATION
LECTURE (3)
I)-LIQUID FUELS AND THEIR
CHARACTERISTICS
The liquid fuels can be classified as follows :
(a) Natural , and Artificial or manufactured fuels .
(b) Petroleum and non petroleum fuels.
Advantages of liquid fuels:
(a) They posses higher calorific value per unit mass than solid
fuels.
(b) They burn without dust, ash, clinkers, etc.
(c) Their firing is easier and also fire can be extinguished easily
by stopping liquid fuel supply.
(d) They are easy to transport through pipes.
(e) They can be stored indefinitely without any loss.
(f) They are clean in use and economic to handle.
(g) Loss of heat in chimney is very low due to greater cleanliness.
(h) They require less excess air for complete combustion.
(i) They require less furnace space for combustion.
Disdvantages of liquid fuels:
a)
The cost of liquid fuel is relatively much higher as
compared to solid fuel.
(b) Costly special storage tanks are required for storing
liquid fuels.
(c) There is a greater risk of fire hazards, particularly, in case
of highly flammable and volatile liquid fuels.
(d) They give bad odour.
(e) For efficient burning of liquid fuels, specially
constructed burners and spraying apparatus are required.
1-Petroleum and its Characteristics
Petroleum is a basic naturally occurring brown to black
flammable liquid. Crude oils are principally found in oil
reservoirs associated with sedimentary rocks beneath the
earth’s surface. Although exactly how crude oils originated is
not established, it is generally agreed that crude oils derived
from marine animal and plant debris subjected to high
temperatures and pressures. It is also suspected that the
transformation may have been catalyzed by rock constituents.
Regardless of their origins all crude oils are mainly constituted
of hydrocarbons mixed with variable amounts of sulfur,
nitrogen, and oxygen compounds. Metals in the forms of
inorganic salts or organo-metallic compounds are present in the
crude mixture in trace amounts.
The ratio of the different constituents in crude oils, however,
vary appreciably from one reservoir to another.
Normally, crude oils are not used directly as fuels or as
feedstocks for the production of chemicals. This is due to the
complex nature of the crude oil mixture and the presence of
some impurities that are corrosive or poisonous to processing
catalysts.
Crude oils are refined to separate the mixture into simpler
fractions that can be used as fuels, lubricants, or as
intermediate feedstock to the petrochemical industries
Petroleums are graded according to the following
phsio-chemical properties :
(a) Density, Specific Gravity and API Gravity.
(b) Salt Content (expressed in milligrams of sodium chloride
per liter oil)
(c) Flash point
(d) Ignition point
(d) Viscosity
(e) Sulphur contents,
(f) Moisture content
(g) Pour Point
h) Calorific value
i) Ash Content (indicates the amount of metallic constituents
in a crude oil).
Classification of Crude Petroleum
Crude oils can be arbitrarily classified into three or four
groups depending on the relative ratio of the hydrocarbon
classes that predominates in the mixture. The following
describes three types of crudes:
A-Paraffinic Base Type Crude Petroleum:
This type of petroleum is mainly composed of the
saturated hydrocarbons from CH4 to C35H72 and a little
of the napthenes and aromatics. the hydrocarbons from
C18 H38 to C35 H72 are sometimes called waxes.
Properties: waxy, less asphaltic, low sulphur, high pour
B-Asphalitc Base Type Crude Petroleum:
contain relatively a large amount of polynuclear aromatics,
a high asphaltene content, and relatively less paraffins than
paraffinic crudes.
Properties: high sulphur, nitrogen, suitable for base oils
C-Naphthenic Crude Petroleum:
The ratios of naphthenic and aromatic hydrocarbons are
relatively higher than in paraffinic crudes.
Properties:less wax, less asphaltic, low pour
Oil products and cuts
II) Manufactured Liquid Fuels and their
Characteristics
Manufactured liquid fuels include Gasoline, Diesel oil, Kerosene,
Heavy oil, Naptha, Lubricating oils, etc. These are obtained mostly
by fractional distillation of crude petroleum or liquefaction of coal.
1-Gasoline and its Characteristics:
 It contains some undesirable unsaturated straight chain hydrocarbons
and sulphur compounds.
 It has boiling range of 40-120ºC.
 The, unsaturated hydrocarbons get oxidized and polymerized,
thereby causing gum and sludge formation on storing. On the other
hand, sulphur compounds lead to corrosion of internal combustion
engine and at the same time they adversely affect tetraethyl lead,
which is generally added to gasoline for better ignition properties.
 The sulphur compounds from gasoline are generally
removed by treating it with an alkaline solution sodium
plumbite. Olefins and colouring matter of gasoline are
usually removed by percolating through ‘Fuller’s earth’
which absorbs preferentially only the colours and olefine.
 It is used in air-crafts. It is also used as motor fuel, in drycleaning and as a solvent.
2-Diesel Fuel and its Characteristics
 The diesel fuel or gas oil is obtained between 250-320 ºC
during the fractional distillation of crude petroleum. This oil
generally contains 85% C. 12% H. Its calorific value is about
11,000 kcal/kg.
 Diesel fuels consist of longer hydrocarbons and have low
values of ash, sediment, water and sulphur contents.
 The suitability of a diesel fuel is determined by its cetane
value, and It is used in diesel engines as heating oil and for
cracking to get gasoline.
• The hydrocarbon molecules in a diesel fuel should be, as far as
possible, the straight-chain ones, with a minimum mixture of
aromatic and side-chain hydrocarbon molecules.
3-Kerosene Oil and its Characteristics
 Kerosene oil is obtained between 180-250 ºC during
fractional distillation of crude petroleum.
 It is used as an illuminant, jet engine fuel, tractor fuel, and
for preparing laboratory gas.
• With the development of jet engine, kerosene has
become a material of far greater importance than it is
used to be.
• When kerosene is used in domestic appliances, it is
always vaporized before combustion. By using a fair
excess of air it burns with a smokeless blue flame.
4-Heavy Oil and its Characteristics
 It is a fraction obtained between 320-400ºC during
fractional distillation of crude petroleum. This oil on
refractionation gives :
(a) Lubricating oils which are used as lubricants.
(b) Petroleum-jelly (Vaseline) which is used as lubricants in
medicines and in cosmetics.
(c) Greases which are used as lubricants.
(d) Paraffin wax which is used in candles, boot polishes,
wax paper, tarpolin cloth and for electrical insulation
purposes.
III)-Manufactured Liquid Fuels
(Non Petroluem)and their Characteristics
A- OIL SHALE:
 Oil shale is a low-permeable rock made of inorganic
material interspersed with a high-molecular weight
organic substance called “Kerogen.” Heating the shale
rock produces an oily substance with a complex structure.
 The composition of oil shales differs greatly from one
shale to another. For example, the amount of oil obtained
from one ton of eastern U.S. shale deposit is only 10
gallons, compared to 30 gallons from western U.S. shale
deposits.
 Retorting is a process used to convert the shale to a high
molecular weight oily material. In this process, crushed shale is
heated to high temperatures to pyrolyze Kerogen. The product
oil is a viscous, high molecular weight material (high in
nitrogen, oxygen, and sulphur). Further processing is required
to change the oil into a liquid fuel.
B- Tar Sands:
 Tar sands (oil sands) are large deposits of sand saturated with
bitumen and water. Tar sand deposits are commonly found at or
near the earth’s surface entrapped in large sedimentary basins.
Large accumulations of tar sand deposits are few. About 98%
of all world tar sand is found in Canada.
 Tar sand is difficult to handle. During summer, it is soft and
sticky, and during the winter it changes to a hard, solid
material.
 Recovering the bitumen is not easy, and the deposits are either
stripmined if they are near the surface, or recovered in situ if
they are in deeper beds.
 The bitumen could be extracted by using hot water and steam
and adding some alkali to disperse it. The produced bitumen is
a very thick material having a density of approximately 1.05
g/cm3.
 It is then subjected to a cracking process to produce distillate
fuels (naptha, kerosine, and gasoline), and coke. The distillates
are hydrotreated to saturate olefinic components.
3-Coal Derived Fuels:
 Liquid fuels derived from coal range from highly
aromatic coal tars to liquids resembling petroleum.
 Coal tar fuels are high boiling fractions of crude tar
from pyrolysis in coke ovens and coal retorts.
 They are low in sulphur and ash, they contain
hydrocarbons, phenols, and heterocyclic nitrogen and
oxygen compounds.
 They are more aromatic than petroleum fuels they
burn with a more luminous flame.
IV) Gaseous Fuels
A) Natural Gas:
1. Raw natural gas is a combustible gas extracted
primarily from any one of
conventional
underground sources, namely petroleum crude oil
wells, gas wells, and condensate wells.
2. natural gas consists of hydrocarbons with very low
boiling point.
3. Methane is the main one with boiling point 119K,
ethane with 184 K, propane with 231 K.
 Some wells, deliver gas containing levels of hydrogen
sulfide, and other sulfur compounds (thiophenes,
mercaptants, and organic sulfides) that must be removed
before transfer to pipelines.
 Pipeline-company contracts typically maximum allowable
limits of impurities: H2S and total sulfur compounds
seldom exceed 0.023 g/m3.
 The majority of pipe line companies limited H2S to less
than 0.007 g/m3.
 Hydrogen:
 Hydrogen is used for production of ammonia and
chemicals, in the refining of petroleum, hydrogenation of
fats and oils. It is also used as a fuel in industrial cutting
and welding operations .
 It is produced by steam reforming of natural gas, a by
product in thermal cracking of hydrocarbons, and to a
small extent by electrolysis of water.
 Hydrogen is non polluting form of energy, when
electrochemically combined with oxygen in fuel cells, only
water, heat and electricity are produced.
 Hydrogen can be stored in gaseous, liquid, or solid form.
 Acetylene:
 Acetylene is used in operations requiring high flame
temperature, such as welding and metal cutting.
 To transport acetylene, it is dissolved in acetone under pressure
and drawn into small containers filled with porous materials.
 Miscellaneous Fuels:
 A variety of gases have minor market shares , theses are
reformed gas , oil gases, producer gas, blue water gas,
carbureted water gas, coal gas, and blast furnace gas. They are
produced by pyrolysis, water gas reaction, or as a by product
in iron production .