Download Fuels cont....

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• Fuel releases its energy either through
Fuel
Any material that is burned or altered
in order to obtain energy and to heat
or to move an object
Energy
• Renewable - Created about as fast as it is
consumed - months, years, decades (trees,
nuclear fusion, sunlight, wind, etc.)
• Nonrenewable – Consumed much faster than
it forms; created slowly - millions of years
(fossil fuels, nuclear fission, etc.)
– a chemical reaction means, such as combustion,
– or nuclear means, such as
• nuclear fission or
• nuclear fusion.
Energy Units
• Joule: One joule is the amount of energy required
to perform the following physical actions:
– The work done by a force of one newton travelling
through a distance of one metre;
– The work required to move an electric charge of one
coulomb through an electrical potential difference of
one volt; or one coulomb volt, with the symbol C·V;
– The work done to produce the power of one watt
continuously for one second; or one watt second.
Thus a kilowatt hour is 3,600,000 joules.
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Energy Units
• Calorie: The energy needed to increase the temperature of a gram
of water by 1 °C depends on the starting temperature and is
difficult to measure precisely.
• British Thermal Unit (BTU) - the amount of energy required to raise
the temperature of one pound of water 1 F at its maximum
density.
• Kilowatt hours is the product of power in kilowatts multiplied by
time in hours
• Kilowatt Hours and BTUs are related in the following conversion:
1 Kilowatt Hour = 3,413 BTUs
Conversion of Energy Units
– 1 calorie = 4.1868 Joules
– 1 BTU = 1055.06 Joules
– 1 BTU = 251.996 calories
World Energy Resource Consumption
• Non-renewable
–
–
–
–
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Petroleum = 36.6%
Natural Gas = 23.3%
Chemical Energy (as of 2005)
Coal = 26.5%
Nuclear fission = 6.3%
In 2009 nuclear power met 13–14% of the world's electricity demand
• Renewable
– Hydroelectric = 2.2%
– Biomass (wood) = 10.4%
– Biogas (methane), liquid biomass, geothermal, solar, wind, and wave
energy = 0.7%
– Nuclear fusion (e.g., reaction similar to that of the Sun) - technology is still
in infancy; currently not available for use as an energy resource
– As of 2010, about 16% of global final energy consumption comes from
renewables, with 10% coming from traditional biomass, which is mainly
used for heating, and 3.4% from hydroelectricity.
Chemical Energy sources
Fossil Fuels
• Much of the chemical energy produced by life
forms, such as fossil fuels, is derived from the
utilization of solar energy through
photosynthesis.
• There are two major categories:
• hydrocarbons, primarily coal and petroleum (liquid petroleum
or natural gas), formed from the fossilized remains of dead
plants and animals by exposure to heat and pressure in the
Earth's crust over a long period of time
• are non-renewable resources because reserves are being
depleted much faster than new ones are being formed.
– Fossil fuel
– Biofuel
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Origin of Fossil fuels
• Formed from the preserved remains of
organisms that have settled to the sea (or
lake) bottom in large quantities under anoxic
conditions.
– Anoxic waters are areas of sea water or fresh
water that are depleted of dissolved oxygen.
– This condition is generally found in areas that have
restricted water exchange.
Origin of Fossil fuels
• This organic matter, mixed with mud, is buried under heavy
layers of sediment.
• The resulting high levels of heat and pressure cause the
organic matter to chemically alter, first into a waxy material
(known as kerogen), and then with more heat into liquid and
gaseous hydrocarbons in a process known as catagenesis
• Terrestrial plants, on the other hand, tend to form coal.
Comparative figures
• 1 litre of regular gasoline is the time-rendered
result of about 23.5 metric tons of ancient
organic material deposited on the ocean floor.
• The total fossil fuel used in the year 1997 is
the result of 422 years of all plant matter that
grew on the entire surface and in all the
oceans of the ancient earth
Types of Fossil Fuels
•
•
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Petroleum Oil
Natural gas
Coal
Oil shales
Tar sands
Gas hydrates
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Coal
Coal
• Most of our coal was formed about 300
million years ago, when much of the earth was
covered by steamy swamps
• Through metamorphism, water and volatiles
are squeezed out, leaving essentially carbon.
• Generally Carboniferous and Permian in age.
• It differs from oil, which comes from oceans,
in that the ‘hard parts’ of plants remain. As a
result, the final product is a solid rock.
• As plants and trees died, their remains sank to
the bottom of the swampy areas,
accumulating layer upon layer and eventually
forming a soggy, dense mat of organic
material called peat
Coal
Coal and Peat
• Continued burial by overlying sediment/rock layers
changes peat into higher grades of coal:
– Lignite (avg ~30% Carbon)
– Subbituminous (avg ~40% C)
– Bituminous (avg ~66% C)
– Anthracite (avg ~92% C)
– Higher carbon content also indicates higher heat content
(burning temperature, BTU) and lower impurity content.
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Types of Coal
• Anthracite
– highest carbon content, between 86-98%
– heat value of nearly 8,000 KJ-per-kg
– most frequently used for home heating
• Bituminous
– has a carbon content ranging from 45-86%
– heat value of 5,500 to 7,500 KJ-per-kg
– used primarily to generate electricity and make coke for
the steel industry
Environmental Problems with Coal
• There are significant environmental costs
associated with the extraction, transport, and
combustion (burning) of coal
• coal is still the dirtiest energy source around
the world
Types of Coal
• Subbituminous
– has a carbon content ranging from 35-45%
– heat value between 4,300 and 6,500 KJ-per-kg
– generally has a lower sulfur content than other types
• makes it attractive for use because it is cleaner burning
– used primarily as fuel for steam-electric power generation
• Lignite
– has a carbon content ranging from 25-35%
– heat value ranging between 2,000 and 4,100 KJ-per-kg
– mainly used for electric power generation
Environmental Problems with Coal
– When it is burned, coal releases a number of
problem pollutants:
• Mercury – a known nervous system toxin
• Sulfur – which leads to the formation of acid
rain
• Nitrogen – which also contributes to acid rain
as well as smog
• Carbon dioxide – the chief global warming gas
• Acid mine drainage is also a product of coal
extraction
– Refers to the outflow of acidic water from
(usually) abandoned mines or coal mines
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Problems with Coal Mining
Problems with Coal Mining
Underground shafts and tunnels are dug to follow a
coal seam (layer)
– Problems include:
• subsidence (slow, or rapid - cave-in)
• black lung disease for miners
• exposure to high levels of radon gas
• methane gas explosions
• underground fires or floods
Sinkholes formed by collapse of abandoned mine shafts
Coal Mining
Coal Mining
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Uses of Coal
• Coal is primarily used to generate electricity.
• Manufacturing plants and industries use coal to make
chemicals, cement, paper, ceramics, and metal products
• Distillation of Coal releases methanol and ethylene
which are used to make products such as plastics,
medicines, fertilizers, and tar
• Certain industries consume large amounts of coal
– concrete and paper companies burn coal
– the steel industry uses coke and coal by-products to make steel
for bridges, buildings, and automobiles
Petroleum Oil
• The term petroleum, comes from Greek
meaning "rock oil", or crude oil
• It is a naturally occurring, flammable liquid
found in rock formations in the Earth
consisting of a complex mixture of
hydrocarbons of various molecular weights,
plus other organic compounds.
Comparison of Major Types of Fossil
Fuel
• Oil contains 17% less C/unit energy than coal
• Natural gas contains 43% less C/unit energy
than coal
• Natural gas contains 31% less C/unit energy
than oil
• Gas<Oil<Coal
Petroleum Oil
• Proportion of hydrocarbons in petroleum is
highly variable and ranges from as much as
97% by weight in the lighter oils to as little as
50% in the heavier oils.
• The hydrocarbons in crude oil are mostly
alkanes, cycloalkanes and various benzene
ring-containing hydrocarbons
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Composition of Petroleum Oil
• Petroleum is found in porous rock formations in the
upper strata of some areas of the Earth's crust.
Composition by weight
Element
Carbon
Hydrogen
Nitrogen
Oxygen
Sulfur
Mining of Petroleum Oil
Percent range
83 to 87%
10 to 14%
0.1 to 2%
0.1 to 1.5%
0.5 to 6%
BASICS OF CRUDE OIL
BASICS OF CRUDE OIL
• Crude oils are complex mixtures containing many different
hydrocarbon compounds that vary in appearance and
composition from one oil field to another.
• Crude oils range in consistency from water to tar-like solids,
and in color from clear to black. An "average" crude oil
contains about 84% carbon, 14% hydrogen, 1%-3% sulfur,
and less than 1% each of nitrogen, oxygen, metals, and
salts.
• Crude oils are generally classified as paraffinic, naphthenic,
or aromatic, based on the predominant proportion of
similar hydrocarbon molecules. Mixed-base crudes have
varying amounts of each type of hydrocarbon. Refinery
crude base stocks usually consist of mixtures of two or
more different crude oils.
• Crude oils are also defined in terms of API (American Petroleum
Institute) gravity. The higher the API gravity, the lighter the crude.
For example, light crude oils have high API gravities and low specific
gravities. Crude oils with low carbon, high hydrogen, and high API
gravity are usually rich in paraffins and tend to yield greater
proportions of gasoline and light petroleum products; those with
high carbon, low hydrogen, and low API gravities are usually rich in
aromatics.
• Crude oils that contain appreciable quantities of hydrogen sulfide or
other reactive sulfur compounds are called "sour." Those with less
sulfur are called "sweet." Some exceptions to this rule are West
Texas crudes, which are always considered "sour" regardless of their
H2S content, and Arabian high-sulfur crudes, which are not
considered "sour" because their sulfur compounds are not highly
reactive.
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Crude oil (with a high API) being
poured into a beaker.
Crude oil on fingers!
Three Principal Groups or Series of Hydrocarbon
Compounds that Occur Naturally in Crude Oil
Three Principal Groups or Series of Hydrocarbon
Compounds that Occur Naturally in Crude Oil
• a. Paraffins. The paraffinic series of hydrocarbon
compounds found in crude oil have the general formula
CnH2n+2 and can be either straight chains (normal) or
branched chains (isomers) of carbon atoms. The lighter,
straight-chain paraffin molecules are found in gases and
paraffin waxes. Examples of straight-chain molecules are
methane, ethane, propane, and butane (gases containing
from one to four carbon atoms), and pentane and hexane
(liquids with five to six carbon atoms). The branched-chain
(isomer) paraffins are usually found in heavier fractions of
crude oil and have higher octane numbers than normal
paraffins. These compounds are saturated hydrocarbons,
with all carbon bonds satisfied, that is, the hydrocarbon
chain carries the full complement of hydrogen atoms.
• b. Aromatics are unsaturated ring-type (cyclic)
compounds which react readily because they
have carbon atoms that are deficient in hydrogen.
All aromatics have at least one benzene ring (a
single-ring compound characterized by three
double bonds alternating with three single bonds
between six carbon atoms) as part of their
molecular structure. Naphthalenes are fused
double-ring aromatic compounds. The most
complex aromatics, polynuclears (three or more
fused aromatic rings), are found in heavier
fractions of crude oil.
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Three Principal Groups or Series of Hydrocarbon
Compounds that Occur Naturally in Crude Oil
• c. Naphthenes are saturated hydrocarbon
groupings with the general formula CnH2n,
arranged in the form of closed rings (cyclic)
and found in all fractions of crude oil except
the very lightest. Single-ring naphthenes
(monocycloparaffins) with five and six carbon
atoms predominate, with two-ring
naphthenes (dicycloparaffins) found in the
heavier ends of naphtha.
Other compounds found in crude oil
• d. Trace Metals. Metals, including nickel, iron, and vanadium are often
found in crude oils in small quantities and are removed during the refining
process. Burning heavy fuel oils in refinery furnaces and boilers can leave
deposits of vanadium oxide and nickel oxide in furnace boxes, ducts, and
tubes. It is also desirable to remove trace amounts of arsenic, vanadium,
and nickel prior to processing as they can poison certain catalysts.
e. Salts. Crude oils often contain inorganic salts such as sodium chloride,
magnesium chloride, and calcium chloride in suspension or dissolved in
entrained water (brine). These salts must be removed or neutralized
before processing to prevent catalyst poisoning, equipment corrosion, and
fouling. Salt corrosion is caused by the hydrolysis of some metal chlorides
to hydrogen chloride (HCl) and the subsequent formation of hydrochloric
acid when crude is heated. Hydrogen chloride may also combine with
ammonia to form ammonium chloride (NH4Cl), which causes fouling and
corrosion.
f. Carbon Dioxide. Carbon dioxide may result from the decomposition of
bicarbonates present in or added to crude, or from steam used in the
distillation process.
g. Naphthenic Acids. Some crude oils contain naphthenic (organic) acids,
which may become corrosive at temperatures above 450° F when the acid
value of the crude is above a certain level.
Other compounds found in crude oil
• a. Sulfur Compounds. Sulfur may be present in crude oil as
hydrogen sulfide (H2S), as compounds (e.g. mercaptans, sulfides,
disulfides, thiophenes, etc.) or as elemental sulfur. Hydrogen sulfide
is a primary contributor to corrosion in refinery processing units.
Other corrosive substances are elemental sulfur and mercaptans.
Moreover, the corrosive sulfur compounds have an obnoxious odor.
• b. Oxygen Compounds. Oxygen compounds such as phenols,
ketones, and carboxylic acids occur in crude oils in varying amounts.
c. Nitrogen Compounds. Nitrogen is found in lighter fractions of
crude oil as basic compounds, and more often in heavier fractions
of crude oil as nonbasic compounds that may also include trace
metals such as copper, vanadium, and/or nickel. Nitrogen oxides
can form in process furnaces. The decomposition of nitrogen
compounds in catalytic cracking and hydrocracking processes forms
ammonia and cyanides that can cause corrosion.
CRUDE OIL PRETREATMENT (DESALTING)
• Crude oil is recovered from the reservoir is mixed with
a variety of substances: gases, water and dirt
(minerals).
• Before certain varieties of crude oil can be processed at
all, they must go through a process called “desalting.”
• This process removes water, salts, and other solid
materials that otherwise could damage the equipment
at a refinery.
• If these crude oil contaminants are not removed, they
can cause operating problems during refinery
processing, such as equipment plugging and corrosion
as well as catalyst deactivation.
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CRUDE OIL PRETREATMENT (DESALTING)
• Desalting essentially means that the crude oil is
dehydrated (water is removed) so that the impurities
settle out.
• Desalting is a water – washing operation performed at
the production field and at the refinery site for
additional crude oil cleanup. If the petroleum from the
seperators contains water and dirt, water washing can
remove much of the water – soluble minerals and
entrained solids.
• Synthetic crude is crude that was processed at the
source. It does not require desalting at the refinery.
Thus, the waste water and contaminants that are a
byproduct of desalting are not an issue for refineries
that use synthetic crude oil.
•
•
PETROLEUM REFINING OPERATIONS
Fractionation (distillation) is the separation of crude oil in atmospheric and
vacuum distillation towers into groups of hydrocarbon compounds of differing
boiling-point ranges called "fractions" or "cuts.“
Conversion processes change the size and/or structure of hydrocarbon molecules.
These processes include:
– Decomposition (dividing) by thermal and catalytic cracking;
– Unification (combining) through alkylation and polymerization; and
– Alteration (rearranging) with isomerization and catalytic reforming.
•
•
•
Treatment processes are intended to prepare hydrocarbon streams for additional
processing and to prepare finished products. Treatment may include the removal
or separation of aromatics and naphthenes as well as impurities and undesirable
contaminants. Treatment may involve chemical or physical separation such as
dissolving, absorption, or precipitation using a variety and combination of
processes including desalting, drying, hydrodesulfurizing, solvent refining,
sweetening, solvent extraction, and solvent dewaxing.
Formulating and Blending is the process of mixing and combining hydrocarbon
fractions, additives, and other components to produce finished products with
specific performance properties.
Other Refining Operations include: light-ends recovery; sour-water stripping; solid
waste and wastewater treatment; process-water treatment and cooling; storage
and handling; product movement; hydrogen production; acid and tail-gas
treatment; and sulfur recovery.
CRUDE OIL PRETREATMENT (DESALTING)
• The two most typical methods of crude-oil desalting, chemical and
electrostatic separation, use hot water as the extraction agent. In
chemical desalting, water and chemical surfactant (demulsifiers) are
added to the crude, heated so that salts and other impurities
dissolve into the water or attach to the water, and then held in a
tank where they settle out. Electrical desalting is the application of
high-voltage electrostatic charges to concentrate suspended water
globules in the bottom of the settling tank. Both methods of
desalting are continuous. A third and less-common process involves
filtering heated crude using diatomaceous earth
• The desalted crude feedstock is preheated using recovered process
heat. The feedstock then flows to a direct-fired crude charge heater
where it is fed into the vertical distillation column just above the
bottom, at pressures slightly above atmospheric and at
temperatures ranging from 650° to 700° F (heating crude oil above
these temperatures may cause undesirable thermal cracking).
Fractional Distillation of crude oil
• The mixture boils, forming vapor (gases); most substances go into
the vapor phase.
• The vapor enters the bottom of a long column (fractional
distillation column) that is filled with trays or plates.
– The trays have many holes or bubble caps (like a loosened cap on a
soda bottle) in them to allow the vapor to pass through.
– The trays increase the contact time between the vapor and the liquids
in the column.
– The trays help to collect liquids that form at various heights in the
column.
– There is a temperature difference across the column (hot at the
bottom, cool at the top).
• The vapor rises in the column.
• As the vapor rises through the trays in the column, it cools.
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• When a substance in the vapor reaches a height where the
temperature of the column is equal to that substance's boiling
point, it will condense to form a liquid. (The substance with the
lowest boiling point will condense at the highest point in the
column; substances with higher boiling points will condense lower
in the column.).
• The trays collect the various liquid fractions.
• The collected liquid fractions may:
– pass to condensers, which cool them further, and then go to storage
tanks
– go to other areas for further chemical processing
• Fractional distillation is useful for separating a mixture of
substances with narrow differences in boiling points, and is the
most important step in the refining process.
Atmospheric Distillation Tower
• The fractionating tower, a steel cylinder about 40
meters high, contains horizontal steel trays for
separating and collecting the liquids. At each tray,
vapors from below enter perforations and bubble caps.
They permit the vapors to bubble through the liquid on
the tray, causing some condensation at the
temperature of that tray. An overflow pipe drains the
condensed liquids from each tray back to the tray
below, where the higher temperature causes reevaporation. The evaporation, condensing, and
scrubbing operation is repeated many times until the
desired degree of product purity is reached.
Atmospheric Distillation Tower
• Side streams from certain trays are taken off to
obtain the desired fractions. Products ranging
from uncondensed fixed gases at the top to heavy
fuel oils at the bottom can be taken continuously
from a fractionating tower. Steam is often used in
towers to lower the vapor pressure and create a
partial vacuum.
• The distillation process separates the major
constituents of crude oil into so-called straightrun products. Sometimes crude oil is "topped" by
distilling off only the lighter fractions, leaving a
heavy residue that is often distilled further under
high vacuum.
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Vacuum Distillation Tower
MAJOR REFINERY PRODUCTS
• In order to further distill the residuum or topped
crude from the atmospheric tower at higher
temperatures, reduced pressure is required to
prevent thermal cracking. The process takes place
in one or more vacuum distillation towers.
• Vacuum tower may produce gas oils (fuel oils for
agricultural, domestic and industrial engines and
boilers), lubricating-oil base stocks, and heavy
residual for propane deasphalting (using propane
to remove and precipitate asphalt (A mixture of
dark bituminous pitch with sand or gravel, used
for surfacing roads, flooring, roofing) from
petroleum stocks, such as for lubricating oils).
• Gasoline. The most important refinery product is motor gasoline, a blend
of hydrocarbons with boiling ranges from ambient temperatures to about
400 °F. The important qualities for gasoline are octane number
(antiknock), volatility (starting and vapor lock), and vapor pressure
(environmental control). Additives are often used to enhance performance
and provide protection against oxidation and rust formation.
• Kerosene. Kerosene is a refined middle-distillate petroleum product that
finds considerable use as a jet fuel and around the world in cooking and
space heating. When used as a jet fuel, some of the critical qualities are
freeze point, flash point, and smoke point. Commercial jet fuel has a
boiling range of about 190°-274° C, and military jet fuel 54°-288° C.
Kerosene, with less-critical specifications, is used for lighting, heating,
solvents, and blending into diesel fuel.
• Liquified Petroleum Gas (LPG). LPG, which consists principally of propane
and butane, is produced for use as fuel and is an intermediate material in
the manufacture of petrochemicals. The important specifications for
proper performance include vapor pressure and control of contaminants.
• Distillate Fuels. Diesel fuels and domestic heating oils have boiling ranges
of about 204°-371° C. The desirable qualities required for distillate fuels
include controlled flash and pour points, clean burning, no deposit
formation in storage tanks, and a proper diesel fuel cetane rating for good
starting and combustion.
MAJOR REFINERY PRODUCTS
How does the petroleum industry
define a "barrel"?
• Residual Fuels. Many marine vessels, power plants, commercial buildings
and industrial facilities use residual fuels or combinations of residual and
distillate fuels for heating and processing. The two most critical
specifications of residual fuels are viscosity and low sulfur content for
environmental control.
Coke and Asphalt. Coke is almost pure carbon with a variety of uses from
electrodes to charcoal briquets. Asphalt, used for roads and roofing
materials, must be inert to most chemicals and weather conditions.
Solvents. A variety of products, whose boiling points and hydrocarbon
composition are closely controlled, are produced for use as solvents.
These include benzene, toluene, and xylene.
Petrochemicals. Many products derived from crude oil refining, such as
ethylene, propylene, butylene, and isobutylene, are primarily intended for
use as petrochemical feedstock in the production of plastics, synthetic
fibers, synthetic rubbers, and other products.
Lubricants. Special refining processes produce lubricating oil base stocks.
Additives such as demulsifiers, antioxidants, and viscosity improvers are
blended into the base stocks to provide the characteristics required for
motor oils, industrial greases, lubricants, and cutting oils. The most critical
quality for lubricating-oil base stock is a high viscosity index, which
provides for greater consistency under varying temperatures.
• The "barrel" is a volumetric unit commonly
used in the petroleum industry and one barrel
is equivalent to
– 42 U.S. gallons ... or
– 34.97 Imperial gallons ... or
– 158.99 liters ... or
– 5.615 Cubic feet
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• Almost none of the products that come out of
the fractional distillation column is ready for
market. Instead, they must be processed
further, usually by:
– Solvent extraction or dewaxing
– Cracking: breaking large hydrocarbons iinto
smaller ones
– Unification: combining smaller pieces
– Alteration: rearranging the various pieces.
Cracking
• The reduction in molecular weight of various
fractions of oil through pyrolysis. Two major
forms of cracking are thermal and steam
cracking.
• Thermal cracking is mainly used to produce a
mixture rich in ethylene and propylene. It has
largely been replaced by steam cracking.
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Cracking
• The simple distillation of crude oil produces amounts
and types of products that are not consistent with
those required by the marketplace, subsequent
refinery processes change the product mix by altering
the molecular structure of the hydrocarbons.
• One of the ways of accomplishing this change is
through "cracking," a process that breaks or cracks the
heavier, higher boiling-point petroleum fractions into
more valuable products such as gasoline, fuel oil, and
gas oils. The two basic types of cracking are thermal
cracking, using heat and pressure, and catalytic
cracking.
Catalytic processes on petroleum
hydrocarbons
• Catalytic hydrocracking – produces small alkanes
from large alkanes by adding hydrogen.
• Catalytic cracking – produces small alkenes and
alkanes by cracking in the absence of hydrogen.
• Catalytic Reforming – the alkanes and
cycloalkanes are upgraded to higher octane
number by conversion into aromatic compounds.
Cracking
• It involves taking heavy oil such as kerosene or
diesel and heating it to a high temperature in
the presence of a catalyst. The large molecule
breaks down into several smaller ones, some
saturated, some unsaturated e.g.
Fluid catalytic cracking (FCC)
• Fluid catalytic cracking (FCC) is the most important
conversion process used in petroleum refineries. It is widely
used to convert the high-boiling, high-molecular weight
hydrocarbon fractions of petroleum crude oils to more
valuable gasoline, olefinic gases, and other products.
• Cracking of petroleum hydrocarbons was originally done by
thermal cracking, which has been almost completely
replaced by catalytic cracking because it produces more
gasoline with a higher octane rating. It also produces
byproduct gases that are more olefinic, and hence more
valuable, than those produced by thermal cracking.
• The feedstock to an FCC is usually that portion of the crude
oil that has an initial boiling point of 340 °C or higher at
atmospheric pressure and an average molecular weight
ranging from about 200 to 600 or higher. This portion of
crude oil is often referred to as heavy gas oil.
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Fluid catalytic cracking (FCC)
• The FCC process vaporizes and breaks the long-chain
molecules of the high-boiling hydrocarbon liquids into
much shorter molecules by contacting the feedstock, at
high temperature and moderate pressure, with a fluidized
powdered catalyst.
• The catalysts used in refinery cracking units are typically
solid materials (zeolite, aluminum hydrosilicate, treated
bentonite clay, fuller's earth, bauxite, and silica-alumina)
that come in the form of powders, beads, pellets or shaped
materials called extrudites.
• In effect, refineries use fluid catalytic cracking to correct
the imbalance between the market demand for gasoline
and the excess of heavy, high boiling range products
resulting from the distillation of crude oil.
Catalytic cracking
• There are three basic functions in the catalytic
cracking process:
– Reaction: Feedstock reacts with catalyst and
cracks into different hydrocarbons;
– Regeneration: Catalyst is reactivated by burning
off coke; and
– Fractionation: Cracked hydrocarbon stream is
separated into various products.
Fluid catalytic cracking (FCC)
• The fluid catalytic cracking process breaks large hydrocarbon
molecules into smaller molecules by contacting them with
powdered catalyst at a high temperature and moderate
pressure which first vaporizes the hydrocarbons and then
breaks them.
Catalytic Cracking
• The unsaturated products are used as
feedstock for the polymer industry.
• The saturated products are usually highoctane branched chain alkanes suitable for
making petrol.
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Catalytic Cracking using Steam
• Steam Cracking is carried out in the presence of steam.
Typically, a naphtha feedstock (with a boiling point or
bp of 70–200°C) is passed, along with steam, through a
coiled tube heated by a furnace.
• The steam acts as a diluents and, thus, favors
unimolecular reactions, which minimize radical chain
termination steps, allowing cracking to continue; and it
lowers the vapour pressure of the hydrocarbons,
thereby reducing resid concentration and maximizing
desired product formation.
Catalytic cracking in the lab
Catalytic cracking can be done in the laboratory by heating mineral wool soaked in oil with
a catalyst, producing a gas.
aluminium oxide
catalyst
gaseous product
mineral wool
soaked in oil
What might this gas be?
Reforming
CATALYTIC REFORMING.
• The process re-arranges or re-structures the
hydrocarbon molecules in the naphtha feedstocks
as well as breaking some of the molecules into
smaller molecules.
• The overall effect is that the product reformate
contains hydrocarbons with more complex
molecular shapes having higher octane values
than the hydrocarbons in the naphtha feedstock.
• Byproducts are small amounts of methane,
ethane, propane and butanes.
• Catalytic reforming is an important process used
to convert low-octane naphthas into high-octane
gasoline blending components called reformates.
• A catalytic reformer comprises a reactor section
and a product-recovery section.
• Most processes use platinum as the active
catalyst. Sometimes platinum is combined with a
second catalyst (bimetallic catalyst) such as
rhenium or another noble metal.
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CATALYTIC REFORMING
• The naphtha feedstock is mixed with hydrogen,
vaporized, and passed through a series of alternating
furnace and fixed-bed reactors containing a platinum
catalyst. The effluent from the last reactor is cooled
and sent to a separator to permit removal of the
hydrogen-rich gas stream from the top of the separator
for recycling.
• The liquid product from the bottom of the separator,
called the reformate is then sent to a fractionator
called a stabilizer (butanizer).
• The pressure at Catalytic reformers ranges from a low
of 50-200psi to a high of 1000 psi.
• There are two distinct isomerization processes,
butane (C4) and pentane/hexane (C5/C6).
– Butane isomerization produces feedstock for
alkylation.
– Pentane/hexane isomerization increases the octane
number of the light gasoline components n-pentane
and n-hexane, which are found in abundance in
straight-run gasoline (Gasoline comprised of only
natural ingredients from crude oil or natural-gas
liquids; for example, no cracked, polymerized,
alkylated, reformed products).
ISOMERIZATION
• In an isomerization reactor the paraffins are catalytically
isomerized to isoparaffins. For example, isomerization
converts n-butane, n-pentane and n-hexane into their
respective isoparaffins of substantially higher octane number.
The straight-chain paraffins are converted to their branchedchain counterparts whose component atoms are the same but
are arranged in a different geometric structure.
• Solvent Treating
• Solvent treating involves methods to remove the
impurities that remain after the initial distillation step.
These methods usually are used both at intermediate
stages in the process and just before the product is
sent to storage. Essentially, these processes remove
the impurities by adding solvents (a liquid that can
dissolve another substance). Depending on the specific
processes, the impurities either clump up and fall to
the bottom by chemical reaction (known as
precipitating), are evaporated away along with the
solvent, or the product is chilled so that the impurities
precipitate.
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Merox process
• Merox is an acronym for mercaptan oxidation. It is a
proprietary catalytic chemical process used in oil refineries
and natural gas processing plants to remove mercaptans from
LPG, propane, butanes, light naphthas, kerosene and jet fuel
by converting them to liquid hydrocarbon disulfides.
Merox process
• Processes within oil refineries or natural gas
processing plants that remove mercaptans and/or
hydrogen sulfide (H2S) are commonly referred to
as sweetening processes because they results in
products which no longer have the sour, foul
odors of mercaptans and hydrogen sulfide.
• The liquid hydrocarbon disulfides may remain in
the sweetened products, they may be used as
part of the refinery or natural gas processing
plant fuel, or they may be processed further.
Merox process
• The Merox process requires an alkaline
environment which, in some of the process
versions, is provided by an aqueous solution
of sodium hydroxide (NaOH), a strong base,
commonly referred to as caustic. In other
versions of the process, the alkalinity is
provided by ammonia, which is a weak base.
Merox process
• In all of the above Merox versions, the overall oxidation
reaction that takes place in converting mercaptans to
disulfides is:
• 4 RSH + O2 → 2RSSR + 2H2O
• The most common mercaptans removed are:
• Methanethiol - CH3SH [m-mercaptan]
• Ethanethiol - C2H5SH [e- mercaptan]
• 1-Propanethiol - C3H7SH [n-P mercaptan]
• 2-Propanethiol - CH3CH(SH)CH3 [2C3 mercaptan]
• Butanethiol - C4H9SH [n-butyl mercaptan]
• tert-Butyl mercaptan - C(CH3)3SH [t-butyl mercaptan]
• Pentanethiol - C5H11SH [pentyl mercaptan]
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Coking
Visbreaking
• A visbreaker is a processing unit in oil refinery whose
purpose is to reduce the quantity of residual oil
produced in the distillation of crude oil and to increase
the yield of more valuable middle distillates (heating
oil and diesel) by the refinery. A visbreaker thermally
cracks large hydrocarbon molecules in the oil by
heating in a furnace to reduce its viscosity and to
produce small quantities of light hydrocarbons (LPG
and gasoline). The process name of "visbreaker" refers
to the fact that the process reduces (i.e., breaks) the
viscosity of the residual oil. The process is noncatalytic.
• Hydrocracking
• In general, catalytic cracking has replaced most uses of
thermal cracking. All forms of catalytic cracking break down
complex compounds into simpler structures to increase the
quality and quantity of the desirable products and decrease
the amount of residuals. A similar process that is not as
common as “catalytic cracking,” is called “hydrocracking.” I
• t is a two-step process that uses a different catalyst — a
substance that helps cause a reaction but that does not
take part in it — than catalytic cracking, as well as lower
temperatures; it also involves high pressure and
introduction of hydrogen (“hydrogenation”). It breaks down
heavy oil into gasoline and jet fuel or kerosene.
Hydrocracking was developed in the 1960s to increase
production of gasoline and forms the basis for the modern
petrochemical industry. It is used for feedstock that is
difficult to process by either catalytic cracking or reforming
because they contain substances that are considered
“poisons” for the catalyst.
• In “coking,” the residual that is left behind in
the distillation tower is heated until is breaks
down into oil, gasoline, and naphtha (which is
further processed to make gasoline); the
process leaves behind an almost pure residue
of carbon called “coke,” which is sold.
• It is not the same as the coke produced in
steel making (or “coke” in coca cola) !
• Hydrotreating
• “Hydrotreating,” is a process that removes certain
constituents — nitrogen, sulfur, oxygen, and metals —
that are considered “contaminants” in the liquid
petroleum.
• These materials can damage the refinery equipment
and impair the quality of the finished product. It also is
used in advance of catalytic cracking to improve yields
and to upgrade the quality of the product. Essentially,
the process works by mixing the feedstock with
hydrogen, heating it, and then passing it through a
catalytic reactor.
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Hydrotreating….
• The reactor converts the contaminants to other forms that
can be separated; the result is a gas stream that, after
treatment, can be used to fire the furnaces at the refinery,
and a liquid stream that can be blended or used as
feedstock.
• Practically all the naphtha that is fed to catalytic reforming
units is hydrotreated to remove arsenic, sulfur, and
nitrogen that would damage the catalyst. The resulting
product, called reformate, is fed to the gasoline blending
pool. Byproducts of this process include hydrogen, which is
recycled within the refinery and used in hydrotreating or
hydrocracking.
Unification
• Unlike cracking, which separates the large
hydrocarbons into smaller ones, “unification”
does the reverse. The process creates
compounds that are used in making chemicals
and in blending gasoline, and generates
hydrogen, which may be used in
hydrocracking or may be sold.
• Reforming
• The major process is “catalytic reforming,” which
converts low-octane products into components that
can be blended into high-octane gasoline. It also
produces hydrogen that can be recycled and used in
other processes.
• Reforming is the result of a number of reactions that
occur simultaneously. The reformer includes a reactor
(which may consist of alternating furnaces and fixedbed reactors) and a section for product recovery.
• Most processes use platinum as the catalyst, although
it may be combined with a second substance.
• Alkylation
• Finally, the structure of the hydrocarbon may be
rearranged, rather than broken or combined, to
produce a product.
• In alkylation, certain gases (known as “low
molecular weight”) are mixed with a catalyst.
• This catalytic process was developed in the 1940s
to produce high-octane aviation gasoline, cleanburning fuels, and materials to produce
explosives and synthetic rubber.
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• Treating and Sweetening
• Some intermediate and finished products may be
treated and sweetened, in most cases to remove
unwanted sulfur. Treating is a means to remove
certain substances that are considered
“contaminants” in the finished product. These
contaminants can include sulfur, nitrogen,
oxygen, certain metals, and salts.
• Sweetening is a major refinery treatment for
gasoline and improves color, odor, and stability; it
also reduces the concentration of carbon dioxide.
These processes can be accomplished by addition
of acid or other compounds, by heating the
product, or through use of catalysts.
• Asphalt Production
• The residual materials from the refining process
can be used to produce asphalt.
• Asphalt for roads is processed in vacuum
distillation, where it is heated and sent to a
column under vacuum to prevent it from cracking
(further separating into other materials).
• When the asphalt will be used for shingles or
other roofing materials, it is produced by air
blowing.
• It is heated almost to the point where it will
evaporate and then sent to a tower, where hot air
is injected. A third process is solvent
deasphalting.
Asphalt Production…
• This process uses propane or hexane as a solvent;
it produces lubricating oil, materials that can be
recycled in other parts of the refining operation,
and asphalt. The process feeds the material and
propane into a tower at closely controlled
mixtures, temperatures, and pressures, and
separates the material on a rotating disc. The
products are evaporated and exposed to steam to
recover the propane, which is recycled in the
operation.
Blending
• Blending is the physical mixing of a number of
different hydrocarbons to produce a product.
• Products can be blended through manifolds or in
tanks and other vessels.
• The products can be blended by injecting the
correct amounts of each component; additives to
improve performance can be added both during
and after blending to provide specific
characteristics that would not otherwise be
present.
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A Small quiz
Are these statements about crude oil refining true or false?
1
Crude oil must be refined before it is used.
2
Fractional distillation works because different
molecules have different boiling points
Large molecules are broken into smaller
molecules during fractional distillation
Small molecules collect at the bottom of the
fractionating column
Each fraction of refined crude oil contains a
mix of compounds with similar boiling point
Catalytical cracking breaks down large alkanes
into smaller alkanes and alkenes
3
4
5
6
Main Uses of Asphalt
• The primary use (more than 80%) of asphalt is in road
construction and maintenance, where it is used as the
glue or binder mixed with aggregate particles to create
asphalt concrete.
• Its other main uses are for bituminous waterproofing
products, including production of roofing felt and for
sealing flat roofs. Only about 1% is used for
waterproofing, damp-proofing, insulation, and paints.
• Other uses are in hydraulics, to protect metals against
corrosion, and in electrical laminate adhesives,
synthetic turf bases and sound insulation materials.
Products from the Refinery
• Asphalt also known as bitumen, is the sticky, black and highly
viscous liquid or semi-solid present in most crude petroleums
and in some natural deposits; it is a substance classed as a
pitch.)
• Fuel Oil - The Fuel Oil is made of long hydrocarbon chains,
particularly Alkanes, Cycloalkanes and aromatics.
• The term “Fuel Oil” is also used in a strict sense to refer only
to the heaviest commercial fuel that can be obtained
from crude oil, heavier than Gasoline and Naphtha.
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• Diesel is collected in the range 250-350 degrees Celsius, and
has hydrocarbons with average of 12 carbon atoms (typically
contain between 8 and 21 carbon atoms per molecule). Diesel
is used as a fuel in motor vehicles, and as a heating oil.
• Naphtha is a product of the refining of crude oil. Naphtha is
collected in the range 60-100 degrees Celsius, and has
hydrocarbons with 5-9 carbon atoms.
• Naphtha is an intermediate product that is processed to
produce petrol for use as a fuel in motor vehicles.
• Lubricating oil contains hydrocarbon chains with 20-50 carbon
atoms, with light lubricating oil at the lower end of this range
with a low viscosity.
• Lubricating oil boils in the range 300-370 degrees Celsius, and
is used to lubricate motor vehicles and industrial machines.
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Kerosene
• Kerosene (also called jet fuel) is a product of the refining of
crude oil. Kerosene is collected in the range 175-325 degrees
Celsius, and has hydrocarbons with 10-18 carbon atoms.
Kerosene is used as a fuel in aero plane jet engines.
• Heavy fuel oil is also known as heavy gas oil or
residual fuel oil.
• Gasoline (also called petrol) is a product of the
refining of crude oil. Gasoline is collected in
the range 40-205 degrees Celsius, and has
hydrocarbons with 5-12 carbon atoms.
Gasoline is used as a fuel in motor vehicles.
Heavy fuel oil….
• Fuel oil is any liquid petroleum product that is
burned in a furnace or boiler for the
generation of heat or used in an engine for
the generation of power.
• Carbon Chain length varies from 12 – 70
carbons.
• Heavy fuel oil is a high-viscosity residual oil
requiring preheating to 104 - 127 °C.
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Gasoline
• Gasoline or petrol is a petroleum-derived
liquid mixture, primarily used as fuel in
internal combustion engines
• It consists mostly of aliphatic hydrocarbons
• The bulk of a typical gasoline consists of
hydrocarbons with between 5 and 12 carbon
atoms per molecule.
Gasoline
• A typical gasoline is predominantly a mixture of
alkanes, cycloalkanes, and alkenes. The exact
ratios can depend on:
– the oil refinery that makes the gasoline, as not all
refineries have the same set of processing units.
– the crude oil feed used by the refinery.
– the grade of gasoline, in particular the octane rating
• The specific density of gasoline is 0.71–0.77 kg/l
Gasoline
PETROL AND OCTANE NUMBERS
• An important characteristic of gasoline is its
octane rating
• Octane rating is measured relative to a mixture of
2,2,4-trimethylpentane (an isomer of octane) and
n-heptane.
• Gasoline is also one of the sources of pollutant
gases.
• It produces carbon dioxide, nitrogen oxides, and
carbon monoxide in the exhaust of the engine
which is running on it.
• A number of things happen to the petrol in the internal
combustion engine, including:
• Petrol is vaporised
• The vapour is mixed with air
• The petrol-air mixture is compressed
• The mixture is ignited by a spark from the spark plug
and burned
• The gases produced by the combustion reaction
expand
• Expansion causes the piston to move i.e. kinetic energy
is produced.
104
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PREMATURE IGNITION in Petrol
Engines
OCTANE RATING
• The more the gases in engine are compressed, the
more they heat up. Sometimes this causes ignition
before the spark is produced.
• This is intended in a diesel engine, where there is no
spark plug, but in a petrol engine the occurrence is
called auto-ignition or knocking or pinking. This is quite
a problem as it can cause loss of power, with obvious
danger, or damage to the engine. It can be prevented
in two ways during petrol manufacture:
– Use of additives
– Use of a suitable mixture of high-octane compounds.
• The octane rating is a measure of the
tendency of a fuel to auto-ignite. The lower
the octane rating the more likely it is that
auto-ignition will occur. Clearly, high-octane
fuels are more desirable. The scale is an
arbitrary one. Two compounds were chosen,
heptane (C7H16) and 2,2,4-trimethylpentane
(CH3C(CH3)2CH2CH(CH3)CH3).
105
OCTANE RATING
106
Additives in Petrol
• Heptane has a high tendency to auto-ignite, so it was
given an octane number of 0.
• On the other hand, 2,2,4-trimethylpentane has a low
tendency to auto-ignite, so it was given a rating of 100.
• A mixture of these two compounds containing 95% of
2,2,4-trimethylpentane is said to have an octane
number of 95 (2,2,4-trimethylpentane was formerly
known as iso-octane, hence the terms “octane
number” or “octane rating”).
• A mixture of compounds with an identical tendency to
auto-ignite, under the same conditions of compression,
would thus also be given an octane rating of 95.
107
Two types of additive have been in use in recent
decades, lead compounds and oxygenates.
(1) Lead compounds e.g. tetra ethyl lead.
• These work by preventing the type of reactions
that cause knocking. They have been in use
since the 1920s, but have long been criticised
for their harmful environmental effects—the
lead compounds present in exhaust fumes are
toxic. Their use has been phased out in many
countries including Kenya.
108
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Additives in Petrol
Petrodiesel
(2) Oxygenates e.g. alcohols or ethers
• These compounds work by raising the octane
number of the fuel. They cause less pollution,
because apart from not containing lead, they
produce lower levels of carbon monoxide
when they burn. The most commonly used
oxygenate is MTBE (methyl tertiary butyl
ether). The schematic name is 2-methoxy-2methylpropane. Its octane rating is 118.
• Petroleum diesel, also called petrodiesel, or
fossil diesel is produced from the fractional
distillation of crude oil between 200 °C and
350 °C at atmospheric pressure, resulting in a
mixture of carbon chains that typically contain
between 8 and 21 carbon atoms per molecule.
• The density of petroleum diesel is about 0.85
kg/l , about 18% more than petrol (gasoline)
109
Diesel Fuels
• Alkanes from nonane to, for instance, hexadecane
(an alkane with sixteen carbon atoms) are liquids
of higher viscosity, less and less suitable for use in
gasoline. They form instead the major part of
diesel and aviation fuel.
Hexadecane (cetane)
• Diesel fuels are characterised by their cetane
number, cetane being an old name for
hexadecane. Cetane number or CN is a measure
of a fuel's ignition delay; the time period between
the start of injection and the first identifiable
pressure increase during combustion of the fuel.
Definition of Cetane:
• Cetane number is actually a measure of a
fuel's ignition delay; the time period between
the start of injection and start of combustion
(ignition) of the fuel. In a particular diesel
engine, higher cetane fuels will have shorter
ignition delay periods than lower cetane fuels.
Cetane numbers are only used for the
relatively light distillate diesel oils.
111
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Chemical relevance
• Cetane (also called Hexadecane) is an alkane hydrocarbon
with the chemical formula C16H34.
• It ignites very easily under compression, so it was assigned
a cetane number of 100, while alpha-methyl napthalene
was assigned a cetane number of 15 . All other
hydrocarbons in diesel fuel are indexed to cetane as to how
well they ignite under compression. The cetane number
therefore measures how quickly the fuel starts to burn
(auto-ignites) under diesel engine conditions. Since there
are hundreds of components in diesel fuel, with each
having a different cetane quality, the overall cetane number
of the diesel is the average cetane quality of all the
components. There is very little actual cetane in diesel fuel.
How Does Cetane Number Affect
Diesel Engine Operation?
• Typical Values
• Generally, diesel engines run well with a CN from
40 to 55. Fuels with higher cetane number which
have shorter ignition delays provide more time
for the fuel combustion process to be completed.
Hence, higher speed diesels operate more
effectively with higher cetane number fuels.
There is no performance or emission advantage
when the CN is raised past approximately 55;
after this point, the fuel's performance hits a
plateau.
Cetane Rating Scale
• There is no benefit to using a higher cetane number fuel
than is specified by the engine's manufacturer.
• Diesel fuels with cetane number lower than minimum
engine requirements can cause rough engine
operation. They are more difficult to start, especially in
cold weather or at high altitudes. They accelerate lube oil
sludge formation. Many low cetane fuels increase engine
deposits resulting in more smoke, increased exhaust
emissions and greater engine wear.
• Overall fuel quality and performance depend on the ratio
of parafinic and aromatic hydrocarbons, the presence of
sulfur, water, bacteria and other contaminants, and the
fuel's resistance to oxidation.
• The reference fuel for the lower end of the
cetane number scale is 2,2,4,4,6,8,8heptamethylnonane with an assigned cetane
number of 15.
• The cetane number scale is then defined as
follows: CN = % by volume hexadecane + 0.15
* (% by volume heptamethylnonane)
2,2,4,4,6,8,8-Heptamethyl-nonane
115
116
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Petrodiesel
• Diesel-powered cars generally have a better fuel
economy than equivalent gasoline engines and
produce less greenhouse gas emission.
• Petrodiesel is composed of about 75% saturated
hydrocarbons (primarily paraffins including n, iso,
and cycloparaffins), and 25% aromatic
hydrocarbons (including naphthalenes and
alkylbenzenes).
• The average chemical formula for common diesel
fuel is C12H23, ranging from approx. C10H20 to
C15H28
Biodiesel
• Biodiesel, is a fuel comprised of mono-alkyl
esters of long chain fatty acids derived from
vegetable oils or animal fats.
• Biodiesel blend, is a blend of biodiesel fuel
with petroleum-based diesel fuel designated
BXX, where XX is the volume percent of
biodiesel.
What is the difference between low sulphur diesel fuel, offroad diesel fuel and regular sulphur diesel fuel?
• Low sulphur diesel fuel - This fuel contains less than 500
parts per million (0.05 wt per cent) sulphur, required for
on-road applications, and may be used off-road.
• Off-road diesel fuel - This refers to diesel fuel that is used
for off-road purposes (i.e., (i.e., mining, farming, marine,
etc.). This fuel is frequently dyed red or "marked" to show
that it is exempt from provincial road taxes.
• Regular sulphur diesel fuel - This fuel contains less than
5,000 parts per million (0.5 wt per cent) sulphur, may not
be used on-road, and is usually used in off-road
applications such as farming, forestry and marine.
Biodiesel Raw Materials
Oil or Fat
Soybean
Corn
Canola
Cottonseed
Sunflower
Beef tallow
Pork lard
Used cooking oils
Alcohol
Methanol (common)
Ethanol
Catalyst
Sodium hydroxide
Potassium hydroxide
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Biodiesel Attributes
•
•
•
•
•
•
•
•
•
•
High Cetane (avg. over 50)
Ultra Low Sulfur (avg. ~ 2 ppm)
High Lubricity, even in blends as low at 1-2%
High Energy Balance (3.2 to 1)
Low Agriculture Inputs: Soybeans
78% Life Cycle CO2 Reduction
Renewable, Sustainable
Domestically Produced
Reduces HC, PM, CO in existing diesel engines
Reduces NOx in boilers and home heating
Biodiesel Materials Compatibility
• Biodiesel and biodiesel blends will form high
sediment levels when in contact with the following
metals:
–
–
–
–
–
–
Brass,
Bronze,
Copper,
Lead,
Tin and
Zinc
• Biodiesel is compatible with:
– Stainless Steel,
– Aluminum
Tips for Biodiesel Handling
• Fuel tanks should be kept as full as possible to
reduce the amount of air and water entering the
tank.
• Storage in on-site tanks should be limited to less
than 6 months. The storage container should be
clean, dry, and dark.
• Copper, brass, lead, tin and zinc should not be
used to store biodiesel.
• Equipment with biodiesel blends in the fuel
system should not be stored for more than 6
months.
 When switching from diesel fuel to biodiesel
blend, it may be necessary to change the fuel
filter an extra time or two.
• One outcome of improper handling of
biodiesel may be microbial contamination.
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Natural Gas
• It is a gas consisting primarily of methane.
• It contains methane and can be classified into two
major groups:
– Fossil Natural Gas
– Biogas
• Fossil natural gas- Natural gas is commercially
produced from oil fields and natural gas fields.
• It sometimes contains significant quantities of ethane,
propane, butane, and pentane—heavier hydrocarbons
removed prior to use as a consumer fuel—as well as
carbon dioxide, nitrogen, helium and hydrogen sulfide
Biogas
• When methane-rich gases are produced by the
anaerobic decay of non-fossil organic matter
(biomass)
• Sources of biogas include swamps, marshes, and
landfills (see landfill gas), as well as sewage
sludge and manure by way of anaerobic
digesters, in addition to enteric fermentation
(fermentation that takes place in the digestive
systems of ruminant animals) particularly in cattle
Composition of Fossil Natural Gas
•
•
•
•
•
•
Mostly methane CH4
Some ethane C2H6
Propane C3H8
Butane C4H10
Hydrogen H2
Some Nitrogen, carbon dioxide, hydrogen
sulphide
Oil Shale
• Fine-grained sedimentary rocks containing
waxy insoluble hydrocarbons called kerogen
• Can be converted to oil at temperatures in
excess of 500 C
• 5 to 25% is recoverable organic material
• Rich oil shales burn like coal
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OIL SPILLS
Mild Oil Spill
• Oil is the most common pollutant in the
oceans.
• The majority of oil pollution in the oceans
comes from land.
• When oil leaks or spills into water it floats on
the surface of both freshwater and saltwater.
• Oil floats because it is less dense than water.
It’s easier to clean-up an oil spill because of
oil’s lower density.
Serious oil spill
HOW TO CLEAN UP AN OIL SPILL
• Mechanical
• Booms- It’s easier to clean-up oil if it’s all in one spot,
so equipment called containment booms act like a
fence to keep the oil from spreading or floating away.
Booms float on the surface and have three parts: a
‘freeboard’ or part that rises above the water surface
and contains the oil and prevents it from splashing over
the top, a ‘skirt’ that rides below the surface and
prevents the oil from being pushed under the booms
and escaping, and some kind of cable or chain that
connects, strengthens, and stabilizes the boom.
Connected sections of boom are placed around the oil
spill until it is totally surrounded and contained.
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Boom
An oil containment boom is laid out in the waters of Treasure Pass near La.,
on July 31, 2010 in response to the Gulf of Mexico oil spill.
Skimmers
• Skimmers- Once you’ve contained the oil, you need to
remove it from the water surface.
• Skimmers are machines that suck the oil up like a
vacuum cleaner, blot the oil from the surface with oilattracting materials, or physically separate the oil from
the water so that it spills over a dam into a tank. Much
of the spilled oil can be recovered with skimmers.
• The recovered oil has to be stored somewhere though,
so storage tanks or barges have to be brought to the
spill to hold the collected oil.
• Skimmers get clogged easily and don’t work well on
large oil spills or when the water is rough.
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Sorbent
• Sorbents- These are materials that soak up liquids by either
absorption or adsorption. Oil will coat some materials by
forming a liquid layer on their surface (adsorption). This
property makes removing the oil from the water much
easier. This is why hay is put on beaches near an oil spill or
why materials like vermiculite are spread over spilled oil.
• One problem with using this method is that once the
material is coated with oil, it may then be heavier than
water. Then you have the problem of the oil-coated
material sinking to the bottom where it could harm animals
living there.
• Absorbent materials, very much like paper towels, are used
to soak up oil from the water’s surface or even from rocks
and animal life on shore that becomes coated with oil.
•FiberDuck Socks are perfect to clean up small oil spills on land or in water.
•Quickly absorbs hydrocarbons such as crude oil, diesel oil and gasoline.
•Socks are also designed to contain spills around machine bases.
•These water-repellent socks are made from highly absorbent hydrophobic fiber
and will float indefinitely.
•Their durable polypropylene skin is UV-, chemical- and tear-resistant
A plane releases chemical dispersant over the Gulf of Mexico oil spill
.
Chemical
• Chemicals, such as detergents, break apart floating oil
into small particles or drops so that the oil is no longer
in a layer on the water’s surface.
• These chemicals break up a layer of oil into small
droplets.
• These small droplets of oil then disperse or mix with
the water. The problem with this method is that
dispersants often harm marine life and the dispersed
oil remains in the body of water where it is toxic to
marine life.
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Crude oil spill bioremediation
• Biological
• Bioremediation- There are bacteria and fungi that naturally
break down oil. This process is usually very slow- it would
take years for oil to be removed by microorganisms. Adding
either fertilizer or microorganisms to the water where the
spill is located can speed up the breakdown process. The
fertilizer gives the bacteria and fungi the nutrients they
need to grow and reproduce quicker. Adding
microorganisms increases the population that is available
to degrade the oil. A drawback to adding fertilizers is that it
also increases the growth of algae.
• When the large numbers of algae die they use up much of
the oxygen so that there isn’t enough oxygen in the water
for animals like fish.
Burning a crude oil spill
Physical
• Burning- Burning of oil can actually remove up to
98% of an oil spill. The spill must be a minimum of
three millimeters thick and it must be relatively
fresh for this method to work.
• There has been some success with this technique
in countries such as Canada.
• The burning of oil during the Gulf War was found
not as large a problem as first thought because
the amount of pollution in the atmosphere did
not reach the expected high levels.
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Burning a crude oil spill
• The decision whether or not to burn a slick at
sea is often contentious.
• Issues such as the distance of the oil from the
damaged vessel or from a populated area; the
potential toxicity of the resultant smoke; the
nature of the oil; the likelihood of the burn
being successful; and the fate of any
unburned residues all require careful
attention before attempts are made to ignite
the oil.
Environmental degradation related to
crude oil extraction by Oil Companies
Burning a crude oil spill
• Fire proof containment boom and an ignitor will most
probably be required for a burn to be undertaken.
Burning crude oil spill at Ogoniland
(Niger Delta) in Southern Nigeria
• In the recent past, a number of oil companies in
the world have been cutting corners by
disregarding set-down rules related to crude oil
extraction with serious implications on the
environment.
• In the past 2 years, the Gulf of Mexico in US
experienced the worst oil spill caused by the
company BP.
• The next 5 slides will show what havoc SHELL
company has caused on NIGERIA in the past 10
years…
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More photos of environmental effects
of crude oil spill at ogoniland
More photos of environmental effects of crude oil spill at ogoniland
Shell oil-heads leaking at K-Dere, Ogoni
A member of the Bodo community, in the
Ogoniland region of Nigeria's Rivers State, tries
to separate crude oil from water
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Is Kenya immune from environmental
disaster related to crude oil extraction?
• It is a pity that some of these companies (BP
and SHELL) may venture to Turkana area here
in Kenya (in the near future) and leave a trail
of destruction (on the lake and adjacent areas)
experienced elsewhere…
• They know that penalty for polluting the
environment is fine of a few million dollars
(which they have in plenty)!
Human toll on oil spill
• And no respirators
Human toll on oil spill
Oil Cleanup workers
are not being given
protective masks
Some glossary used in oil spills
• Pollutant: Any substance that contaminates or makes the
environment impure. Pollutants are commonly man-made wastes.
• Absorption: The process of taking in another substance, in the
same manner that a sponge would.
• Adsorption: When a liquid or solid takes up a substance and holds it
on its surface, so that the substance coats the molecules of the
solid or liquid.
• Dispersant: A chemical or material that when added to some other
substance causes it to break apart and scatter about.
• Bioremediation: Using natural biological processes to correct or
counteract an environmental hazard or ecological disaster. An
example of bioremediation is adding fertilizer or bacteria to the
water to help clean-up an oil spill.
• Ecosystem: An ecological unit of all the living organisms plus the
nonliving, physical environment and how they function together.
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CALORIMETRY
CALORIMETRY
• Calorimetry is the science of measuring
quantities of heat, as distinct from
“temperature”.
• The instruments used for such measurements
are known as calorimeters.
• We shall be concerned only with oxygen bomb
calorimeters, which are the standard
instruments for measuring calorific values of
solid and liquid combustible samples
• The calorific value (heat of combustion) of a
sample may be broadly defined as the number of
heat units liberated by a unit mass of a sample
when burned with oxygen in an enclosure of
constant volume.
• In this reaction the sample and the oxygen are
initially at the same temperature and the
products of combustion are cooled to within a
few degrees of the initial temperature
• Also the water vapor formed by the combustion
is condensed to the liquid state.
CALORIMETRY
Bomb Calorimeter
• the term calorific value (or heat of combustion)
as measured in a bomb calorimeter denotes the
heat liberated by the combustion of all carbon
and hydrogen with oxygen to form carbon dioxide
and water, including the heat liberated by the
oxidation of other elements such as sulfur which
may be present in the sample.
• The heat energy measured in a bomb calorimeter
may be expressed either as calories (cal), or
Joules (J).
• A bomb calorimeter is a type of constant-volume
calorimeter used in measuring the heat of combustion of a
particular reaction.
• Bomb calorimeters have to withstand the large pressure
within the calorimeter as the reaction is being measured.
• Electrical energy is used to ignite the fuel; as the fuel is
burning, it will heat up the surrounding air, which expands
and escapes through a tube that leads the air out of the
calorimeter.
• When the air is escaping through the copper tube it will
also heat up the water outside the tube.
• The temperature of the water allows for calculating calorie
content of the fuel.
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Bomb Calorimeter
• Four essential parts are required in any bomb
calorimeter:
1. a bomb or vessel in which the combustible charges
can be burned,
2. a bucket or container for holding the bomb in a
measured quantity of water, together with a stirring
mechanism,
3. an insulating jacket to protect the bucket from
transient thermal stresses during the combustion
process, and
4. a thermometer or other sensor for measuring
temperature changes within the bucket.
Bomb Calorimeter
Determination of heat content of fuels
• Oxygen Bomb Calorimeter
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Bomb Calorimeter: Standardization
• Before a material with an unknown heat of
combustion can be tested in a bomb
calorimeter, the energy equivalent or heat
capacity of the calorimeter must first be
determined.
• Consider a standardization test in which 1.651
grams of standard benzoic acid (heat of
combustion 6318 cal/g) produced a
temperature rise of 3.047°C.
Bomb Calorimeter: Standardization
The Fuel Test
• The energy equivalent (W) of the calorimeter
(the “calorimeter constant”) is then calculated
as follows:
• After the energy equivalent has been
determined, the calorimeter is ready for testing
fuel samples.
• Samples of known weight are burned and the
resultant temperature rise is measured and
recorded.
• The amount of heat obtained from each sample is
then determined by multiplying the observed
temperature rise by the energy equivalent of the
calorimeter.
• Note: 1 calorie = 4.18400 joules
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Note: 1 calorie = 4.18400 joules
• Assume a fuel sample weighing 0.9936 gram
produced a temperature rise of 3.234°C in a
calorimeter with an energy equivalent (the
“calorimeter constant”) of 2416 cal/°C.
• The gross heat of combustion (Hg) is then
determined by multiplying the temperature rise by
the energy equivalent, and dividing this product by
the weight of the sample, e.g:
Solution
• Since this is a combustion reaction, heat flows
from the system to the surroundings… thus, it
is exothermic. The heat released by the
reaction will be absorbed by two things:
(a) the water in the calorimeter and
(b) the calorimeter itself.
Problem
• A 1.000 g sample of octane (C8H18) is burned
in a bomb calorimeter containing 1200 grams
of water at an initial temperature of 25.00oC.
After the reaction, the final temperature of
the water is 33.20oC. The heat capacity of the
calorimeter (also known as the “calorimeter
constant”) is 837 J/oC. The specific heat of
water is 4.184 J/g oC. Calculate the heat of
combustion of octane in kJ/mol.
Solution:
a. Calculate the heat absorbed by the water
(qwater)
m = 1200 grams
cwater = 4.184 J/goC
T = 33.20 – 25.00 = 8.20oC
qwater = (m)(c)( T), so
qwater = (1200 g)(4.184 J/g.oC )(8.20 oC )
= 41170.56 J
= 41.2 kJ
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Solution:
Solution:
b. Calculate the heat absorbed by the calorimeter (qcal)
• The temperature change of the calorimeter is the
same as the temperature change for water. In this
step, however, we must use the heat capacity of
the calorimeter, which is already known. When
using heat capacity, the mass of the calorimeter is
not required for the calculation. (It’s already
incorporated into the heat capacity).
Ccal = 837 J/oC
T = 33.20 – 25.00 = 8.20oC
qcal = (Ccal)( T), so
so, qcal = (837 J/oC)(8.20 oC) = 6863.4 J = 6.86 kJ
Solution:
• Since 1.000 gram of octane was burned, the
heat of combustion for octane is equal to –
48.1 kJ/gram. In other words, when one mole
of octane is burned, 48.1 kJ of heat is released
from the reaction. What is the heat of
combustion in kJ/mol?
1 mol of octane weighs 114 grams, so
(-48.1 kJ/g)(114 g/mol) = – 5483 kJ/mol.
• The TOTAL heat absorbed by the water and
the calorimeter is the sum of (a) and (b):
• 41.2 + 6.86 = + 48.1 kJ. (Remember, q is
positive because the heat is being absorbed).
• The amount of heat released by the reaction is
equal to the amount of heat absorbed by the
water and the calorimeter. We just need to
change the sign. So, qreaction = – 48.1 kJ
Important properties related to liquid
fuels
Property
–
–
–
–
–1
Heat of combustion (kJ mol )
Boiling point (°C)
–1
Density (g mL )
–1
Average molar mass (g mol )
Important conversions
–1
• Heat of combustion per gram = Heat of combustion (kJ mol ) /
–1
Average molar mass (g mol )
–1
• Volume (litres) = 1000 × Average molar mass (g)/ Density (g mL )
–1
• Heat of combustion per liter of fuel = Heat of combustion (kJ mol )
–1
–1
×1000 × density (g mL ) /Average molar mass (g mol )
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