5 FUELS.ppt

SOURCES OF FUELS
• A material which consists of chemicals and stores energy that can
be practicably released as heat energy is termed as fuel. Chemical
fuels release energy by reacting with substances around them,
mostly by the process of oxidation.
• Chemical fuels are classified according to their physical properties
such as a solid, liquid and gas or on the basis of their availability
such as primary or natural fuels and secondary or artificial fuels.
• TYPE OF FUEL PRIMARY SECONDARY
• Solid fuels Wood, Coal, Coke, Charcoal
Peat, Dung, etc.
• Liquid fuels Petroleum Diesel, Gasoline,
Kerosene, Coal tar,
Naptha, Ethanol
• Gaseous fuels Natural gas Hydrogen, Propane,
Coalgas, CNG etc.

COAL
• Coal, a mineral of fossilized carbon, is a combustible black
or brownish-black sedimentary rock usually occurring in
rock strata in layers called coal beds. The harder forms,
such as anthracite coal ( C- 92% -98%), can be regarded as
metamorphic rock because of later exposure to elevated
temperature and pressure.
• Coal is composed primarily of carbon along with variable
quantities of other elements, chiefly Hydrogen, Sulphur,
Oxygen, and Nitrogen.
• Coal has been a useful resource and it is primarily used for
the production of electricity or heat, and is also used for
industrial purposes, such as refining metals.

TYPES OF COAL
• PEAT
• Peat has industrial importance as a fuel in some regions
like Ireland and Finland.
• In its dehydrated form, peat is a highly effective
absorbent for fuel and oil spills on land and water.
• It is also used as a conditioner for soil to make it able to
retain more water.
• Used for cooking & domestic heating.
Gardeners use peat moss mainly as a soil amendment or
ingredient in potting soil. It has an acid pH, so it's ideal for
acid loving plants, such as blueberries and camellias.

lignite
• Lignite or brown coal, is the lowest rank of
coal and used almost exclusively as fuel for
electric power generation.
• Jet, a compact form of lignite, is sometimes
polished and has been used as an ornamental
stone.
• It is a softer coal with a high moisture
content and contains carbon ,sulphur &
mercury

• The carbon content of lignite ranges from 65-
70% and represents the youngest rank of
fuel—with approximate ages of around 60
million years.
Approximately 7 percent of the coal mined in
the U.S. is lignite.
• It's found primarily in North Dakota , Texas
• Mississippi .

• Peat is the first step in coal formation. Peat is
composed of over 60% organic matter;
• Lignite is a soft brown coal that still contains a
high amount of water.
• Lignite has a higher heat content
than peat but is still not the most
desired form of coal.

TYPES OF COAL (CONTD. – 1)
• SUB-BITUMINOUS COAL
• It’s properties range from those of lignite to those of
bituminous coal and is primarily used as fuel for steam-
electric power generation and is an important source of
light aromatic hydrocarbons for the chemical synthesis
industry.
• BITUMINOUS COAL
• It is a dense sedimentary rock, usually black or dark
brown, often with well-defined bands of bright and dull
material. It is primarily used as fuel in steam-electric
power generation, with substantial quantities used for
heat and power applications in manufacturing and to
make coke.

TYPES OF COAL (CONTD. – 2)
• ANTHRACITE
• It is the best grade of coal, which is a harder, glossy black
coal used primarily for residential and commercial space
heating. It may be divided further into metamorphically
altered bituminous coal and "petrified oil“.
• GRAPHITE
• It is technically the highest grade but it is difficult to ignite
thus it is not commonly used as fuel. It is mostly used in
pencils and, when powdered, as a lubricant.

COMPARISON OF COALS
GRADE % VOLA. C% H2% O2% S% Heat kJ/kg
Lignite 45–65 60–75 6.0–5.8 34-17 0.5-3 <28,470
Flame Coal 40-45 75-82 6.0-5.8 >9.8 ~1 <32,870
Gas Flame 35-40 82-85 5.8-5.6 9.8-7.3 ~1 <33,910
Coal
Gas Coal 28-35 85-87.5 5.6-5.0 7.3-4.5 ~1 <34,960
Fat Coal 19-28 87.5-89.5 5.0-4.5 4.5-3.2 ~1 <35,380
Forge Coal 14-19 89.5-90.5 4.5-4.0 3.2-2.8 ~1 <35,380
Non-Baking 10-14 90.5-91.5 4.0-3.75 2.8-3.5 ~1 35,380
Coal
Anthracite 7-12 >91.5 <3.75 <2.5 ~1 <35,300

PETROLEUM
• Petroleum is a naturally occurring flammable liquid
consisting of a complex mixture of hydrocarbons of
various molecular weights and other liquid organic
compounds, that are found in geologic formations
beneath the Earth's surface.
• The word Petroleum is referred for both the naturally
occurring unprocessed crude oils and petroleum products
that are made up of refined crude oil.
• Petroleum is recovered mostly through oil drilling. It is
refined and separated easily by boiling into a large
number of consumer products such as petrol or gasoline,
kerosene to asphalt and chemical reagents used to make
plastics and pharmaceuticals.

The World's Largest Oil Reserves
By Country
• Venezuela - 300,878 million barrels.
• Saudi Arabia - 266,455 million barrels. ...
• Canada - 169,709 million barrels. ...
• Iran - 158,400 million barrels. ...
• Iraq - 142,503 million barrels. ...
• Kuwait - 101,500 million barrels. ...
• United Arab Emirates - 97,800 million barrels.
Russia - 80,000 million barrels. ...
•

PETROLEUM (CONTD. – 1)
• In strict sense, petroleum includes only crude oil, but
it includes all liquid, gaseous, and solid hydrocarbons.
The lighter hydrocarbons such as methane, ethane,
propane and butane occur as gases, while pentane
and heavier ones are in the form of liquids or solids.
• An oil well produces predominantly crude oil, with
some natural gas dissolved in it. Heavier hydrocarbons
such as pentane, hexane, and heptane etc. are in
gaseous form under the earth’s crust but condense at
normal pressure and temperature on extraction.
Condensate resembles petrol in appearance & similar
in composition to other volatile light crude oils.

PETROLEUM (CONTD. – 2)
• The proportion of light hydrocarbons in the
petroleum mixture varies greatly among different
oil fields, ranging from as much as 97 percent by
weight in the lighter oils to as little as 50 percent in
the heavier oils and bitumens.
• The hydrocarbons in crude oil are mostly alkanes,
cyclo-alkanes and various aromatic hydrocarbons
while the other organic compounds contain
nitrogen, oxygen and sulphur, and trace amounts
of metals such as iron, nickel, copper and
vanadium.

COMPOSITION OF PETROLEUM
ELEMENT RANGE
Carbon 83 to 87%
Hydrogen 10 to 14%
Nitrogen 0.1 to 2%
Oxygen 0.05 to 1.5%
Sulphur 0.05 to 6.0%
Metals < 0.1%
HYDROCARBON RANGE
Paraffins 15 to 60%
Naphthenes 30 to 60%
Aromatics 3 to 30%
Asphaltics 6%

USES OF PETROLEUM
• Petroleum is used mostly for producing fuel oil and petrol.
84 % of the hydrocarbons present in petroleum is converted
into energy-rich fuels including petrol, diesel, jet, heating,
and other fuel oils & liquefied petroleum gas.
• Petroleum is also the raw material for many chemical
products, including pharmaceuticals, solvents, fertilizers,
pesticides, and plastics. Remaining 16 % hydrocarbon is
converted into these materials.
• The lighter grades of crude oil provide best products, but
the world's reserves of light and medium oil have been
depleted. Oil refineries now use complex and expensive
methods to use heavier crude oils which have too much
carbon and not enough hydrogen using fluid catalytic
cracking to convert the longer, more complex molecules in
the oil to the shorter, simpler ones in the fuels.

USES OF PETROLEUM (CONTD. – 1)
• Certain types of hydrocarbons may be mixed with other
non-hydrocarbons, to create other products.
• Alkenes can be used for plastics or other compounds.
• Lubricants such as light machine oils, motor oils, and
greases by adding viscosity stabilizers.
• Wax is used in the packaging of frozen foods.
• Sulphur or Sulphuric acid are useful industrial materials
obtained as a byproduct of sulphur removal from fuels.
• Bulk tar.
• Asphalt
• Petroleum coke, used as solid fuel.
• Aromatic petrochemicals used in other chemical
production

• Alkenes are Unsaturated hydrocarbons are
hydrocarbons that have double or triple
covalent bonds between adjacent carbon
atoms.
• Those with at least one carbon-to-carbon
double bond are called alkenes and those with
at least one carbon-to-carbon triple bond are
called alkynes.

Cracking of crude oil
• In petrochemistry, petroleum geology and
organic chemistry, cracking is the process
whereby complex organic molecules such as
kerogens or long-chain hydrocarbons are
broken down into simpler molecules such as
light hydrocarbons, by the breaking of carbon-
carbon bonds in the precursors.

• Cracking allows large hydrocarbon molecules
to be broken down into smaller, more useful
hydrocarbon molecules. Fractions containing
large hydrocarbon molecules are heated to
vaporise them.

Refining process
• Cracking processes break down heavier
hydrocarbon molecules (high boiling point
oils) into lighter products such as petrol and
diesel.
• These processes include
• Catalytic cracking,
• Thermal cracking and
• Hydro-cracking.

• Catalytic cracking is used to convert heavy
hydrocarbon fractions obtained by vacuum
distillation into a mixture of more useful
products such as petrol and light fuel oil.
• In this process, the feedstock undergoes a
chemical breakdown, under controlled heat
(450 – 500oC) and pressure, in the presence of
a catalyst –

• CATALYST is a substance which promotes the
reaction without itself being chemically
changed.
• Small pellets of silica – alumina or silica –
magnesia have proved to be the most
effective catalysts.

The cracking reaction yields
• Petrol, LPG, Unsaturated olefin compounds,
Cracked gas oils, Light gases and a Solid coke
residue.
A liquid residue called cycle oil, and a solid
coke residue.
• Cycle oil is recycled to cause further
breakdown and the coke, which forms a layer
on the catalyst, is removed by burning.
• Other products passed through a fractionator
to be separated and separately proces

• Fluid catalytic cracking uses a catalyst in the
form of a very fine powder which flows like a
liquid when agitated by steam, air or vapour.
• Feedstock entering the process immediately
meets a stream of very hot catalyst and
vaporises.
• The resulting vapours keep the catalyst
fluidised as it passes into the reactor, where
the cracking takes place and where it is
fluidised by the hydrocarbon vapour.

• The catalyst next passes to a steam stripping
section where most of the volatile
hydrocarbons are removed.
• It then passes to a regenerator vessel where it
is fluidised by a mixture of air and the
products of combustion which are produced
as the coke on the catalyst is burnt off.
• The catalyst then flows back to the reactor.

• The catalyst thus undergoes a continuous
circulation between the reactor, stripper and
regenerator sections.
• The catalyst is usually a mixture of aluminium
oxide and silica.
• Most recently, the introduction of synthetic
zeolite catalysts has allowed much shorter
reaction times and improved yields and
octane numbers of the cracked gasolines.

THERMAL CRACKING
• Thermal cracking uses heat to break down the
residue from vacuum distillation.
• The lighter elements produced from this
process can be made into distillate fuels and
petrol.
• Cracked gases are converted to petrol
blending components by alkylation or
polymerisation.

• Naphtha is upgraded to high quality petrol by
reforming.
• Gas oil can be used as diesel fuel or can be
converted to petrol by hydrocracking.
• The heavy residue is converted into residual
oil or coke which is used in the manufacture of
electrodes, graphite and carbides.

• Hydrocracking can increase the yield of petrol
components, as well as being used to produce
light distillates. It produces no residues, only
light oils.
Hydrocracking is catalytic cracking in the
presence of hydrogen.
• The extra hydrogen saturates, or
hydrogenates, the chemical bonds of the
cracked hydrocarbons and creates isomers
with the desired characteristics

• . Hydrocracking is also a treating process,
because the hydrogen combines with
contaminants such as sulphur and nitrogen,
allowing them to be removed.
Gas oil feed is mixed with hydrogen, heated,
and sent to a reactor vessel with a fixed bed
catalyst, where cracking and hydrogenation
take place.
• Products sent to fractionator for separation.

• The hydrogen is recycled. Residue from this
reaction is mixed again with hydrogen,
reheated, and sent to a second reactor for
further cracking under higher temperatures
and pressures.

• In addition to cracked naphtha for making
petrol, hydrocracking yields light gases useful
for refinery fuel, or alkylation as well as
components for high quality fuel oils, lube oils
and petrochemical feedstocks.
• Following the cracking processes it is
necessary to build or rearrange some of the
lighter hydrocarbon molecules

• into high quality petrol or jet fuel blending
components or into petrochemicals.
• The former can be achieved by several
chemical process such as alkylation and
isomerisation.

CRACKING OF MINERAL CRUDE OIL
• Fluid catalytic cracking is a commonly used process in a
modern oil refinery. The process was first used around
1942 and employs a powdered catalyst mainly consisting
of aluminium oxide and silica into small, porous pieces.
• Pre-heated feed is sprayed into the base of the riser via
feed nozzles where it contacts extremely hot fluidized
catalyst at 666 to 760 °C.
• The hot catalyst vaporizes the feed & catalyzes the
cracking reactions that break down the high-molecular
weight oil into lighter components including LPG,
gasoline, and diesel.

CRACKING OF MINERAL CRUDE OIL (CONTD. – 1)
• The catalyst-hydrocarbon mixture flows upward through
the riser for a few seconds, and then the mixture is
separated via cyclones.
• The catalyst-free hydrocarbons are routed to a
main fractionator for separation into fuel gas, LPG,
gasoline, naphtha, light cycle oils used in diesel and jet
fuel, and heavy fuel oil.
• During the trip up the riser, the cracking catalyst is used
up reactions which deposit coke on the catalyst and
greatly reduce activity and selectivity.

CRACKING OF MINERAL CRUDE OIL (CONTD. – 2)
• Used up catalyst is separated from the cracked
hydrocarbon vapors and sent to a stripper where it
contacts steam to remove hydrocarbons remaining in the
catalyst pores.
• Used up catalyst then flows into a fluidized-bed
regenerator where air is used to burn off the coke to
restore catalyst activity and also provide the necessary
heat for the next reaction cycle, cracking being
an endothermic reaction.
• The regenerated catalyst then flows to the base of the
riser, repeating the cycle.

CHARACTERISTICS OF MARINE FUELS
MARINE DISTILLATE FUELS
Parameter Unit Limit DMX DMA DMB DMC
Density at 15 °C kg/m³ Max - 890.0 900.0 920.0
Viscosity at 40 ° C mm²/s Max 5.5 6.0 11.0 14.0
Viscosity at 40 °C mm²/s Min 1.4 1.5 - -
Micro Carbon Residue % m/m Max 0.30 0.30 - -
at 10% Residue
Micro Carbon Residue % m/m Max - - 0.30 2.50
Water % V/V Max - - 0.3 0.3
Sulphur c % m/m Max 1.0 1.5 2.0 2.0
Total Sediment Existent % m/m Max - - 0.10 0.10
Ash % m/m Max 0.01 0.01 0.01 0.05
Vanadium mg/kg Max - - - 100
Aluminium + Silicon mg/kg Max - - - 25
Flash point °C Min 43 60 60 60

CHARACTERISTICS OF MARINE FUELS (CONTD. - 1)
MARINE DISTILLATE FUELS (CONTD. – 1)
Parameter Unit Limit DMX DMA DMB DMC
Pour point, Summer °C Max - 0 6 6
Pour point, Winter °C Max - -6 0 0
Cloud point °C Max -16 - - -
Calculated Cetane Index Min 45 40 35 -
Appearance Clear & Bright - -
Zinc d mg/kg Max - - - 15
Phosphorus d mg/kg Max - - - 15
Calcium d mg/kg Max - - - 30
c (A sulphur limit of 1.5% m/m will apply in SOx Emission Control Areas
designated by the International Maritime Organization. There may be
local variations.)
d (The Fuel shall be free of ULO. A Fuel is considered to be free of ULO if one
or more of the elements are below the limits. All three elements shall
exceed the limits before deemed to contain ULO.)

MARINE RESIDUAL FUELS
Parameter Unit Limit RME RMF RMG RMH
180 180 380 380
Density at 15 °C kg/m³ Max 991.0 991.0 991.0 991.0
Viscosity at 50°C mm²/s Max 180.0 180.0 380.0 380.0
Water % V/V Max 0.5 0.5 0.5 0.5
Micro Carbon Residue % m/m Max 15 20 18 22
Sulphur c % m/m Max 4.50 4.50 4.50 4.50
Ash % m/m Max 0.10 0.15 0.15 0.15
Vanadium mg/kg Max 200 500 300 600
Flash point °C Min 60 60 60 60
Pour point, Summer °C Max 30 30 30 30
Pour point, Winter °C Max 30 30 30 30
Aluminium + Silicon mg/kg Max 80 80 80 80
Total Sediments % m/m Max 0.10 0.10 0.10 0.10

MARINE RESIDUAL FUELS
Parameter Unit Limit RME RMF RMG RMH
180 180 380 380
• Zinc d mg/kg Max 15 15 15 15
• Phosphorus d mg/kg Max 15 15 15 15
• Calcium d mg/kg Max 30 30 30 30
• c A sulphur limit of 1.5% m/m will apply in Sox
Emission Control Areas designated by the
International Maritime Organization. There may be
local variations.
• d The Fuel shall be free of ULO. A Fuel is considered to
be free of ULO if one or more of the elements are
below the limits. All three elements shall exceed the
limits before deemed to contain ULO.

ORIMUSLION
• Orimulsion is a registered trade name for a bitumen based
fuel developed for industrial use by Venezuela.
• Like coal & oil, bitumen occurs naturally & obtained from
the world's largest deposit in the Orinoco in Venezuela.
• Raw bitumen has an extremely high viscosity and specific
gravity and is unsuitable for direct use in conventional
power stations.
• Orimulsion is made by mixing the bitumen with about
30% fresh water and a small amount of surfactant which
behaves similarly to fuel oil.

ORIMUSLION (CONTD. -1)
• ADVANTAGES OF ORIMUSLION
• As a fuel for electricity generation, Orimulsion is very
competitive with coal.
• It is relatively easy and safe to produce, transport, handle
and store.
• It is easy to ignite & has good combustion characteristics.
• It can be used in power stations designed to run on coal or
heavy fuel oil, with suitable modification.

ORIMUSLION (CONTD. -2)
• DISADVANTAGES OF ORIMUSLION
• If there is a spill in water during it’s transportation, the
mixture de-emulsifies and the bitumen comes out of
suspension.
• It is a non-Newtonian fluid, thus if it is allowed to cool
below 30 °C, it will set and pumping becomes impossible,
there is no way of restarting flow through pipeline.
• During a strike, supplies of orimulsion were disrupted, as
a result, except China and Cuba, it’s use was discontinued.
• Due to rising crude oil prices, Orinoco bitumen (extra
heavy oil) is being diluted with a lighter crude oil which
makes this blend more profitable as a crude oil in the
world market than by selling it as Orimulsion.

NATURAL GAS
• Natural gas is a naturally occurring hydrocarbon gas
mixture consisting primarily of methane, but commonly
including varying amounts of other hydrocarbons, carbon
dioxide, nitrogen and hydrogen sulphide.
• Natural gas is an energy source often used for heating,
cooking, and electricity generation.
• Also used as fuel for vehicles and as a chemical feedstock
in the manufacture of plastics and other commercially
important organic chemicals.
• Natural gas is found in deep underground natural rock
formations or associated with other hydrocarbon
reservoirs in coal beds.

• Most natural gas is created over time by two
Mechanisms namely
• Biogenic and
• Thermogenic.
• Biogenic gas is created by methanogenic
• organisms in marshes, bogs, landfills, and
shallow sediments.

• THERMOGENIC GAS:-
Deeper in the earth, at greater temperature
and pressure, thermogenic gas is created
from buried organic material.
• Before natural gas can be used as a fuel, it
must undergo processing to remove
• impurities, including water, to meet the
specifications of marketable natural gas.

• Byproducts of processing include ethane,
propane, butanes, pentanes, and higher
molecular weight hydrocarbons, hydrogen
sulphide, carbon dioxide, water vapour, and
sometimes helium and nitrogen.
• Natural gas is often called as gas, especially
when compared to other energy sources such
as oil or coal.

NATURAL GAS (CONTD. – 2)
• In the 19th century natural gas was usually obtained as a by-
product of producing oil and was unwanted and virtually
valueless since it had to be piped to the end user thus gas was
burned off at oil fields.
• Nowadays pipelines are constructed when it is economically
feasible to transport gas from a wellsite to an end consumer in
the regions where natural gas has high demand.
• Natural gas is also exported as a liquid and transported to users
through conventional pipelines and tankers.
• Apart from oil fields, natural gas is also associated with
Coal beds or Natural gas fields.

• It sometimes contains a significant amount of
ethane, propane, butane, and pentane, after
removal of heavier hydrocarbons for
commercial use prior to the methane being
sold as a consumer fuel or chemical plant
feedstock.
• Non-hydrocarbons such as carbon dioxide,
nitrogen, and hydrogen sulfide are removed
before the natural gas is transported.

• TOWN GAS
or coal gas refers to a gaseous mixture, used as a fuel, that
is released when bituminous coal is burned.
• Town gas is a flammable gaseous fuel made by the destructive
distillation of coal and contains a variety of calorific gases.
• including hydrogen, carbon monoxide, methane and other
volatile hydrocarbons together with small quantities of non-
calorific gases such as carbon dioxide and nitrogen.
• It is used in a similar way to natural gas.
• Though not economically competitive with other sources of
fuel, but there are some specific cases where it is the best
option and it may be so into the future.

• Town gas produced in gas houses is a by-
product of coke ovens in which heated
bituminous coal in air-tight chambers.
• The coal tar or asphalt collected at the
bottom of the gashouse ovens is used for
roofing and other water-proofing purposes &
when mixed with sand and gravel was used
for paving streets.

• BIOGAS
• When methane-rich gases are produced by the anaerobic decay of
non-fossil organic matter commonly called biomass, product is
referred to as biogas. Sources of biogas include swamps, marshes,
and landfills, sewage sludge and manure by way of anaerobic
digestion.
• Methane released directly into the atmosphere acts as a pollutant
as it gets oxidized, producing carbon dioxide and water. Methane in
the atmosphere has a half life of seven years, 50% methane broken
down to carbon dioxide and water after seven years.
• It is economical to consume the gas on site or within a short
distance of the landfill using a dedicated pipeline. Water vapor is
often removed, even if the gas is combusted on site. Other non-
methane components are removed to prevent fouling of the
equipment or the environmental. Gas produced in sewage plants is
usually consumed to generate electricity.

FLOW CHART OF NATURAL GAS GENERATION

• Natural gas is a major source of electricity generation
through the use of cogeneration (Gas turbines and steam
turbines). Natural gas is also well suited for a combined
use in association with renewable energy sources such as
wind or solar and for supplementing peak-load in power
stations functioning in tandem with hydroelectric plants.
• High efficiencies can be achieved through combining gas
turbines with a steam turbine in combined cycle mode.
Natural gas burns more cleanly than other hydrocarbon
fuels and produces 30% less carbon dioxide per unit of
energy released. Natural gas powered Combined Heat and
Power plant (Cogeneration plant) is considered the
cleanest and energy efficient available source and a rapid
way to cut carbon emissions.

PROPERTIES OF MARINE FUELS
• KINEMATIC VISCOSITY
• Kinematic viscosity is a measure for the fluidity of the
product at a certain temperature.
• The viscosity of a fuel decreases with increasing
temperature.
• The viscosity at the moment the fuel leaves the injectors
has to be within the limits prescribed by the engine
manufacturers to obtain an optimal spray pattern.
• Viscosity outside manufactures specifications at the
injectors will lead to
Poor combustion
Deposit formation and
Energy loss.

• The viscosity of the fuel has to be such that
the required injection viscosity can be
reached by the ship’s preheating system.

PROPERTIES OF MARINE FUELS (CONTD. – 1)
• DENSITY
• The official unit is kg/m3 at 15°C, while kg/l at 15°C is the
most commonly used unit.
• Density is used in the calculation of the quantity of fuel
delivered.
• From a technical point of view, the density gives an
indication of the ignition quality of the fuel within a
certain product class, this is particularly the case for the
low viscosity IFOs.
• The product density is important for the onboard
purification of the fuel.
• The higher the density the more critical it becomes for
purification.

PROPERTIES OF MARINE FUELS (CONTD. - 2)
• CETANE NUMBER AND CETANE INDEX
• Only applicable for gasoil and distillate fuels.
• It is a measure of ignition quality of the fuel in a
diesel engine.
• The higher the rpm of the engine, the higher the
required Cetane number. The Cetane number is
determined on an engine.
• The Cetane index is an approximate value of the
Cetane number based on the density and the
distillation of the fuel. The Cetane index is not
applicable when Cetane improving additives are

• CARBON RESIDUE
• A carbon residue determination is a typical laboratory test
performed under specified reduced air supply and does
not represent combustion conditions in an engine.
• It gives an indication of the amount of hydrocarbons in
the fuel which have difficult combustion characteristics,
but there is no conclusive correlation between carbon
residue figures and actual field experience. The micro
carbon residue method is specified by ISO 8217.
• ASH
• The ash content is a measure of the metals present in the
fuel, either as inherent to the fuel, or as contamination.

• Conradson carbon residue, commonly known
as "Concarbon" or "CCR" is a laboratory test
used to provide an indication of the coke-
forming tendencies of an oil. Quantitatively,
the test measures the amount of
carbonaceous residue remaining after the
oil's evaporation and pyrolysis. For diesel fuel,
Concarbon correlates approximately with
combustion chamber deposits,

• FLASH POINT
• Flash point is the temperature at which the vapours of a fuel
ignite (under specified test conditions), when a test flame is
applied. The flash point for all fuels to be used in bulk
onboard vessels is set at PM, CC, 60°C minimum (SOLAS
agreement). DMX, a special low cloud point gasoil, may only
be stored onboard in drums because of its <60°C flash point.
• SULPHUR
• The sulphur content of a marine fuel depends on the crude
oil origin and the refining process. When a fuel burns,
sulphur is converted into sulphur oxides. These oxides reach
the lubricating oil via the blow-by gas . These oxides are
corrosive to engine cylinder liners and must be neutralized
by the cylinder lubricant.

• Marine engine lubricants are developed to cope with this
acidity (high BN). If the correct lubricant is used, the
sulphur content of a marine fuel is technically not
important (although it has environmental implications in
sensitive areas such as the Baltic Sea).
• WATER CONTENT
• Water in fuel is a contamination and does not yield any
energy. The percentage of water in the fuel can be
translated into a corresponding energy loss for the
customer. Water is removed onboard the vessel by
centrifugal purification. If after purification the water
content remains too high, water vapour lock can occur
and pumps can cut out.

• If water-contaminated fuel reaches the injectors,
combustion can be erratic. Water in fuel which
remains standing in lines for a longer period can cause
corrosion.
• POUR POINT
• Pour point is the lowest temperature at which a fuel
will continue to flow when it is cooled under specified
standard conditions. Contrary to straight run type
heavy fuels (pour point typically in the +20°C range),
bunker fuels from a complex refinery generally have
pour points below 0°C (range –10 to –20°C).

• This is reflected in the fact that bunker fuel tanks are
generally not completely heated any more, but only
before the fuel transfer pump. This can then lead to
problems, if a vessel receives high pour straight run
bunker fuel.
• For distillate marine diesel, cold temperature
behaviour is controlled in ISO 8217 by maximum pour
point. With marine diesels, a high content of heavier
n-paraffins vigilance is required if strong temperature
changes are expected resulting in settling of wax even
when pour point specs have been met.

Most of the paraffin compounds in naturally
occurring crude oils are normal paraffins,
while isoparaffins are frequently produced in
refinery processes.
The normal paraffins are uniquely poor as
motor fuels, while isoparaffins have good
engine-combustion characteristics.

• ELEMENTS
• Vanadium and nickel are elements found in certain heavy
fuel oil molecules (asphaltenes). Upon combustion
Vanadium oxides are formed and some of them have
critical melting temperatures. The most critical are the
double oxides / sulphates with sodium. Some countries
have implemented maximum Ni concentrations for inland
use of heavy fuel due to emission regulations.
• TOTAL SEDIMENT POTENTIAL
• Inorganic material naturally occurring in crude oil is
removed in the refineries prior to the atmospheric
distillation. Some minor contamination (e.g. Iron oxides)
of a finished heavy fuel can not be excluded.

• Asphaltenes consist primarily
of carbon, hydrogen, nitrogen, oxygen,
and sulfur, as well as trace amounts
of vanadium and nickel. The C:H ratio is
approximately 1:1.2, depending on the
asphaltene source.

• The biggest risk for sediment formation in heavy fuel is
due to potential coagulation of organic material inherent
to the fuel itself (viz.broken asphaltenes), if insufficiently
stable, can form sediment (coagulation is influenced by
time and temperature). A decrease in aromaticity of the
fuel matrix by blending with paraffinic cutterstocks can
also deteriorate the stability of the asphaltenes.
• In cases of heavy fuel instability, it is only a relative small
fraction of the asphaltenes which forms sediment, but
this organic sediment includes in its mass some of the fuel
itself and water. The amount of generated sludge can
become quite high. The total potential sediment gives the
total amount of sediment that can be formed under
normal storage conditions, excluding external influences.

ASPHALTENE CONTAMINATION
Some of the symptoms are as followed:
• Filter Plugging
• Reduced fuel economy
• Loss of power
• More frequent injector replacements
• More frequent filter changes
• More money out of pocket!

• Cutter stocks are generally lighter petroleum
liquids than the heavy fuel oil produced by
Russian refineries, which can be used to
reduce viscosity to produce on-
specEuropean fuel oil. The bulk of Europe's
cutter stock supply comes from US refineries.
• Kerosine is cutterstock oil

• Straight run fuel oil is the residue that comes
out from the distillation column, without
further processing in vaccum distillation unit
or residue catalytic cracker.
•

• If the total potential sediment of the heavy fuel oil
markedly exceeds the specification value (0.10 % (m/m)
max for all grades of IFOs and HFOs, problems with the
fuel cleaning system can occur, fuel filters can get plugged
and combustion become erratic.
• CATALYTIC FINES
• As described previously, HCO is used worldwide in
complex refining as a blending component for heavy fuel.
Mechanically damaged catalyst particles (aluminum
silicate) cannot be removed completely in a cost-effective
way, and are found in blended heavy fuel.

• Fuel precleaning onboard ships has a removal efficiency of
approximately 80% for catalyst fines. In order to avoid
abrasive wear of fuel pumps and injectors, a maximum
limit of 80 mg/kg for Al+Si has been defined in ISO 8217.
• CALCULATED CARBON AROMATICITY INDEX (CCAI)
• CCAI is an indicator of the ignition delay of an IFO.CCAI is
calculated from the density and the viscosity of the fuel
oil. Although it is not an official specification, it has found
its way in many users’ bunker fuel specification
requirements. Some manufacturers specify CCAI limits for
their engines, depending on engine type and application.

UNDESIRED ELEMENTS IN MARINE FUELS
• One of the greatest sources of trouble of fuel oils is
the water and sediments often present in the oil.
Following sediments are commonly seen in fuel oils.
• Vanadium and Nickel are present in crude oils which
are carried into marine fuels.
• Aluminium and Silicon are used as catalysts in
Refineries and available in fuels as catalytic fines and
are highly abrasive.
• Sodium is freely available in marine fuels and is highly
corrosive in combination.
• Shipboard fuel oil purification is aimed to remove
most of these unwanted substances from marine
fuels.

• 6. Abrasion: The heavy fuel oil contains
deposits such as vanadium, sulphur, nickel,
sodium, silicon etc. which are difficult to
remove and have an abrasive effect on the
liner and piston surfaces.
• 7. Corrosion: Elements such as vanadium and
sulphur, which are present in the heavy fuel
oil, leads to high temperature and low-
temperature corrosion respectively.
•

• Sulphur is also present in the heavy grade fuel.
When sulphur combines with oxygen to form
sulphur dioxide or sulphur trioxide, it further
reacts with moisture (which can be due to low
load operation) to form vapours of sulphuric
acid. When the metal temperature is below
the dew point of acid, the vapours condense
on the surface and cause low-temperature
corrosion.

• Vanadium when comes in contact with sodium
and sulphur during the combustion, forms a
eutectic compound with a low melting point
of 530°C.
• This molten compound is highly corrosive and
attacks the oxide layers on the steel liner and
piston (which is used to protect the steel
surface), leading to corrosion.

TREATMENT OF MARINE FUELS ON BOARD
• In the late 70’s, the increasing market demand for distillate
type fuels (gasoline, diesel) and the resulting changes in
refinery processes to cope with this demand have resulted
in a deterioration of the heavy fuel quality.
• Efficient cleaning of heavy fuel oil is mandatory to achieve
reliable and economical operation of diesel engines burning
heavy fuel.
• Water is a common contaminant in fuel oil. Apart from
water content in the fuel oil, during transportation there can
be a further contamination in the storage tank due to water
condensation as a result of temperature changes.
• Catalyst fines from aluminium silicate used in the catalytic
cracking process may end up in the heavy fuel and have to
be removed to avoid abrasive wear of various engine parts.

TREATMENT OF MARINE FUELS ON BOARD (CONTD. – 1)
• Treatment on board ship involves removal of Impurities
from the fuel oil by Separation and Filtration.
• Separation is carried out both by gravitation in settling
tank and centrifugal in purifier/clarifier.
• Filtration is done in two or three stages and fineness of
filter depends on the size of nozzle through which the oil
has to pass which in turn depends on degree of
atomization and penetration required.
• In diesel engines, the combustion chamber is at high
pressure and time available for ignition is very short’

• Thus fuel should reach the combustion
chamber in a finely atomized form, achieved
by pumping fuel at high pressure and passing
it through very fine holes.
• This will require a notch wire filter separating
impurities to very small size.

• On the other hand, pressure in the boiler furnace is near
atmospheric and time available for combustion is
sufficient thus oil under moderate pressure can penetrate
through the furnace and very fine atomization is not
required.
• As the burner tip for the boiler has large holes, course
filtration is sufficient to prevent it’s blockage. Contrary to
diesel engine where impurities leave deposits on piston
crown and increase the abrasive wear on running surface,
boiler combustion is not affected by the presence of
impurities thus centrifuging is considered unnecessary.
• Boiler fuel just needs to be settled for removal of water &
large impurities whereas treatment of diesel engine
requires, sedimentation, separation & filtration.

• Fuel from the storage tank is pumped to the settling tank and
contaminants (WATER & SOILDS) sink to the bottom
of the tank under influence of the gravity force (g).
• The rate of separation by gravity, Vg is defined by Stoke’s law:
Vg = [d2 (ρ2 - ρ1) / 18 η] g, where
d = particle diameter
ρ2 = particle density
ρ1 = density of the fuel oil
η = viscosity of the fuel oil
g = gravitational acceleration.
• Complete separation in a reasonable period of time can only
be achieved by mechanically generated centrifugal force.

• Fuel from the settling tank is fed to a centrifugal system or
purifier and water and solids are separated out of the
fuel. The rate of separation in a centrifugal field (V) is
defined as:
• V= Vg x Z where
Z = rω2/g
r = distance of the particle from the axis of rotation
ω = angular velocity
• The factor Z specifies how much greater the
sedimentation rate is in the centrifugal field compared to
the gravitational field.

CHANGE IN DENSITY WITH INCREASE IN TEMPERATURE

USE OF CENTRIFUGES
• In a purifier type separator, cleaned oil and separated water
are continuously discharged during operation. An interface is
formed in the bowl between the water and the oil. This
interface position is affected by several factors, such as density
and viscosity of the fuel oil, temperature and flow rate.
• Position of the interface becomes progressively more sensitive
with increasing fuel density. The generally accepted maximum
density limit for the conventional purifier is 991 kg/m3 (at
15°C).
• In order to achieve optimum separation results with purifiers,
the interface between oil and water in the bowl must be
outside the disc stack but at the inside of the outer edge of the
top disc.

USE OF CENTRIFUGES (CONTD. – 1)
PURIFIER BOWL ARRANGEMENT

• The position of the interface is affected mainly by the DENSITY
and the VISOSITY of the fuel oil and is adjusted by means of
gravity discs.
• The correct gravity disc is defined as the largest disc that does
not cause a broken water seal. With the correct interface
position, the oil feed can enter the narrow channels.
• For fuel oils with a viscosity above 180 mm2/s at 50°C, it is
recommended that the highest possible temperature (98°C) be
maintained. The fuel oil has to remain in the centrifuge bowl for
as long as possible by adjusting the flow rates through the
centrifuge so that it corresponds to the amount of fuel required
by the engine.
• If the interface is in an incorrect position the oil to be cleaned
will pass only through the lower part of the disc stack, since the
upper part is blocked with water. Thus separation will be
inefficient as only the part of the disc stack will be utilized.

• In order to achieve optimum separation results with purifiers,
the interface between oil and water in the bowl must be
outside the disc stack but at the inside of the outer edge of the
top disc.
• To ensure optimal cleaning of a fuel oil, a second separator can
be used in series operation, e.g. a purifier followed by a
clarifier. The density limit of 991 kg/m3 is not applicable to
clarifier operation, but the combined system of purifier and
clarifier in series remains restricted to a maximum density of
991kg/m3 at 15°C.
• Heavy movements of the vessel can stir up dirt, water and
sludge that have accumulated over time on the bottom of the
bunker and settling tanks. It is therefore potentially possible
that efficient purification is not always obtained when
separators have been put in a parallel purifying function.

CONVENTIONAL CLARIFIER
• In a conventional clarifier the water outlet is
closed off and the separated water can only be
discharged with the sludge through the sludge
ports at the bowl periphery.
• A sludge discharge causes turbulence in the bowl
and leads to less efficient separation.
Consequently, the water handling capability of a
conventional clarifier is insufficient for the
cleaning of fuel oil if the fuel oil has a significant
amount of water (the prior use of a purifier with
its continuous water removal is mandatory).

CONVENTIONAL CLARIFIER (CONTD. – 1)

ADVANCED COMPUTER DRIVEN
FUEL CLEANING SYSTEMS
• Fuel oils with densities above 991 kg/m3 at 15°C are
available in the market and can be purified, with the ALCAP
system, which allows fuel oil densities up to 1010 kg/m3 at
15°C.
• Fuel oil is continuously fed to the separator. The oil flow is
not interrupted when sludge is discharged. The ALCAP
basically operates as a clarifier. Clean oil is continuously
discharged from the clean oil outlet. Separated sludge and
water accumulate at the periphery of the bowl.
• Sludge and water is discharged after a pre-set time. If
separated water approaches the disc stack (before the pre-
set time interval between two sludge discharges is reached)
some droplets of water start to escape with the cleaned oil.

ALCAP SYSTEM (CONTD. - 1)
• A water transducer, installed in the clean oil outlet
immediately senses the small increase of the water content
in the clean oil. The signal from the water transducer is
transmitted to a control unit and changes in water content
are measured.
• Increased water content in the cleaned oil is considered as
the sign of reduced separation efficiency for not only water
but for the removal of solid particles as well. When the
water content in the cleaned oil reaches the pre-set trigger
point, the control unit will initiate an automatic discharge of
the water that has accumulated in the bowl through the
water drain valve. That means water is discharged either
with the sludge at the periphery of the bowl or through the
water drain valve when separated water reaches the disc
stack before the pre-set time between sludge discharges.

RESIDUAL FUELS
• This oil is called residual fuel oil (RFO) or heavy fuel
oil (HFO).
• It is the remainder of the crude oil after gasoline and
distillate fuel oils have been extracted through distillation.
It fuels thermal power stations or robust engines( marine
engines.)
• Residual means the material remaining after the removal
of more valuable products.
• The residue may contain various undesirable impurities
including 2 percent water.
• Residual fuels are dense, viscous require heating, contain
impurities which require treatment before use & have
combustion related problems.

• Residual fuels require preheating from 105 –
145°C for proper atomization at the burners
depending on required viscosity.
• Fuels used on ship are typically called Bunker
Oil which in the present day may be obtained
from the heavy gas oil .
• or it may be a blend of residual oil with
distillate oil to adjust the viscosity.
• Residual fuel oil is cheaper

RESIDUAL FUELS (CONTD. -1)
• The most common residual marine fuels are RMG and
RMK. The differences between the two are mainly the
density and viscosity, with RMG generally being delivered
at 380 centistokes or less, and RMK at 700 centistokes or
less. Ships with more advanced engines can process
heavier, more viscous, and thus cheaper, fuel.
• Governing bodies like California, European Union etc.
have started to put the limit on the maximum sulphur of
fuels burned in their ports to limit pollution. In such
places, residual fuels can not be used as they have sulphur
contents more than the specified limits, thus Marine
Distillate Fuels of grades DMA and DMB are generally in
use.

RESIDUAL FUELS (CONTD. -2)
• Main drawback of residual fuel oil is its high initial viscosity
which requires a system for storage, heating, pumping, and
burning.
• Though it is usually lighter than water,
it is much heavier and more viscous than distillate fuels.
• RMG oil must, in fact, be stored at around 38 °C and heated
to 66°C before it can be easily pump.
• At cold temperatures it can become a tarry semisolid. The
flash point of RMG oil is about 66 °C.
• Attempting to pump high-viscosity oil at low temperature can
cause the damage to fuel lines, furnaces, and related
equipment which are often designed with lighter fuels in
mind.

• The high sulphur content of RMG oil up to
4.5% by weight cause environmental
pollution.
• When spilled into the sea, this oil does not
degrade rapidly.
• It’s high viscosity and stickiness is
responsible for forming a layer on sea bed.

EMULSIFIED OILS
• Emulsified Fuels are emulsions composed of water and
fuel. Emulsion fuels can be either a micro-emulsion or as
macro-emulsion.
• The essential differences between the two are their
stability. Microemulsions are thermodynamically stable
whereas macroemulsions are kinetically stabilized.
• Microemulsions are formed spontaneously whereas
macroemulsions are formed by a shearing process.
• Particle size distribution in micro-emuslion have
dimensions of 10 to 200 nm and in macroemulsion have
100 nm to over 1 micrometer.
• Micro-emulsions are isotropic whereas macro-emulsions
are prone to settling and changes in particle size over
time.

EMULSIFIED OILS (CONTD. – 1)
• Water-in-oil emulsified fuels contain between 5 and
30% water (by mass) in the overall fuel emulsion.
• The main advantages of using emulsified fuels instead
of plain fuel are environmental protection and
economic benefits. Addition of water to the diesel
decreases combustion temperatures and lowers NOx
emissions.
• Usual method is to inject water along with fuel although
some engine builders prefer emulsified fuels as it
further helps in atomization of fuel. Fuel is first
atomized in the fuel valve by passing it at high pressure
through fine orifices and secondly when water droplet
explodes in combustion chamber on receiving the heat
gives secondary atomization.

ADDITIONAL QUESTION AND ANSWER
• ABSOLUTE VISCOSITY
• The resistance to flow encountered when one layer or
plane of fluid attempts to move over another identical
layer or plane of fluid at a given speed. Absolute viscosity
is also called dynamic viscosity.

• Pour point:
• The pour point is the temperature below
which the fuel ceases to flow. Once the fuel oil
temperature goes below the pour point, it
forms wax which can lead to blockage of the
filter. The wax formation will also build upon
tank bottoms and heating coils, leading to a
reduction in heat exchanging capabilities.

• Sulphur:
• Sulphur in the fuel is one of the main factors
for sulphur oxide pollution from ships – a
pollutant which is currently under major
scrutiny. As per MARPOL, the current sulphur
value for HFO are:
• 3.50% m/m on and after 1 January 2012
• 0.50% m/m on and after 1 January 2020

ASH
• The amount of inorganic materials present in
the fuel which remain as residue once the
combustion process is over is called ash
deposits.
These deposits mainly consist of elements
such as vanadium, sulphur, nickel, sodium,
silicon, aluminium etc., which are already
present in the fuel.
• The max. limit of ash content in the fuel is
0.2% m/m.

LNG
• Liquefied natural gas (LNG) is natural gas that
has been cooled to a liquid state, at about -
260°Fahrenheit, for shipping and storage. The
volume of natural gas in its liquid state is
about 600 times smaller than its volume in its
gaseous state.

LNG
• Is natural gas (predominantly methane, CH4,
with some mixture of ethane C2H6) that has
been cooled down to liquid form for ease and
safety of non-pressurized storage or transport.
• It takes up about 1/600th the volume of
natural gas in the gaseous state (at standard
conditions for temperature and pressure).
• It is odorless, colorless, non-toxic and non-
corrosive.

• Hazards include flammability after
vaporization into a gaseous state, freezing
and asphyxia.
• The liquefaction process involves removal of
certain components, such as dust, acid
gases, helium, water, and heavy hydrocarbons,
which could cause difficulty downstream.

ADVANTAGES
• ECONOMY CHEAPER THAN ANY OTHER
FOSSIL FUEL.
• ENVIORNMENT Environment: Another
important fact is that natural gas burns
without releasing any soot or sulfur dioxide. It
also emits 45% less carbon dioxide than coal
and 30% less than oil.

• Transportation: Transportation is made via
sea (tankers) and land (pipelines and small
tanks). This fact allows natural gas to be easily
transferred from power plants to residential
areas.
Multi-uses: Natural gas is a multi-use fuel. It
can be used for generating electric power,
powering Ships (by substituting for diesel and
gasoline),
•

• Availability: It is abundant and almost
worldwide available.
• Conversion to Hydrogen Fuel: It is currently
the cheapest fossil fuel source for producing
hydrogen.

DISADVANTAGES
• Flammable and Toxic: Natural gas leaks can be
proven to be extremely dangerous. Such leaks
may be the cause of fire or explosions. The gas
itself is extremely toxic when inhaled.
• Non-Renewable: It is a finite source of energy
and cannot be considered a long-term
solution to our energy supply problem.

• Processing: In order to use it as a fuel, all
constituents other than methane have to be
extracted. The processing results in several
byproducts: hydrocarbons (ethane, propane,
etc.), sulfur, water vapor, carbon dioxide, and
even helium and nitrogen.
• Installation: The whole pipe installation may
be very expensive to construct since long
pipes, specialized tanks.

• Environmental Impact: When natural gas
burns, carbon dioxide, monoxide, and other
carbon compounds are emitted in the
atmosphere contributing to the greenhouse
effect. Although it is cleaner than other fossil
fuels (oil, coal, etc.) as far as byproducts are
concerned, natural gas leaks can become
more hazardous since methane is 21 times
more dangerous than carbon dioxide.
•

• The natural gas is then condensed into a liquid
at close to atmospheric pressure by cooling it
to approximately −162 °C (−260 °F); maximum
transport pressure is set at around 25 kPa
(4 psi).

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