Petroleum Refining & Petrochemicals
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Transcript of Petroleum Refining & Petrochemicals
LISTEN...LEARN...THINK...GROW 1
Welcome to
Petroleum Refining &
PetrochemicalsECHM 404
Zin-Eddine Dadach
2013-2014
LISTEN...LEARN...THINK...GROW 2
L.O’s of the course Describe refinery products and feed stock qualities
Differentiate between atmospheric and vacuum crude oil distillation units
Explain the process and principles used for hydrotreating, catalytic reforming, and isomerization.
Explain the process and principles for coking, catalytic cracking, and hydrocracking units
Describe the petrochemical industry and discuss the properties and manufacture of some typical end products
Highlight the common chemical reactions involved in the production of petrochemicals.
Perform tasks using the internet to retrieve information about the markets for crude oil, petroleum products, and petrochemical end products.
L.O #1:
Describe Refinery
products and feed stock
qualities
Crude oil is one of the most valuable commodities in the
world, but only after it has been refined into petroleum
products.
LISTEN...LEARN...THINK...GROW 3
LISTEN...LEARN...THINK...GROW 4
WHAT IS PETROLEUM OR
CRUDE OIL?
Petroleum (Latin Petroleum derived from Greek πέτρα
(Latin petra) - rock + έλαιον (Latin oleum) - oil)
Crude oil is a naturally occurring liquid found in
formations in the Earth consisting of a complex
mixture of hydrocarbons (mostly alkanes) of various
lengths.
Crude oil may also be found in semi-solid form mixed
with sand, as in the Athabasca oil sands in Canada,
where it may be referred to as crude bitumen.
LISTEN...LEARN...THINK...GROW 5
WHAT IS CRUDE OIL?
Crude oils are in liquid form containing complex mixtures of many different hydrocarbon compounds. Crude oils 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.
Crude oils are generally classified as paraffinic, naphthenic, or aromatic, based on the predominant proportion of similar hydrocarbon molecules.
LISTEN...LEARN...THINK...GROW 6
MAIN COMPONENTS OF CRUDE OILS
Carbon - 84%
Hydrogen - 14%
Sulfur - 1 to 3% (hydrogen sulfide, sulfides, disulfides, elemental sulfur)
Nitrogen - less than 1% (basic compounds with amine groups)
Oxygen - less than 1% (found in organic compounds such as carbon dioxide, phenols, ketones, carboxylic acids)
Metals - less than 1% (nickel, iron, vanadium, copper, arsenic)
Salts - less than 1% (sodium chloride, magnesium chloride, calcium chloride)
LISTEN...LEARN...THINK...GROW 7
MAJOR HYDROCARBONS IN
CRUDE OIL
The approximate length range is C5H12 to C18H38.
Any shorter hydrocarbons are considered natural gas or natural gas liquids,
while long-chain hydrocarbons are more viscous, and the longest chains are part of bitumen or asphalt.
Crude oil refining is a key transformation step in the
Midstream Sector of the oil and gas value chain
because it adds commercial value to the oil by
transforming it into many different marketable
products.
LISTEN...LEARN...THINK...GROW 8
LISTEN...LEARN...THINK...GROW 9
GLOBAL ECONOMY
DEPENDS ON ENERGY The global economy receives almost 80% of its
energy subsidies from nonrenewable fossil sources:
crude oil, gas, and coal.
They are called "nonrenewable" because, for all
practical purposes, they're not being made any more.
Nonrenewable fossil sources are the major
contributors to global warming
LISTEN...LEARN...THINK...GROW 10
DIFFERENT ENERGY
SOURCES
LISTEN...LEARN...THINK...GROW 11
WORLD OIL RESERVES
LISTEN...LEARN...THINK...GROW 12
ECONOMY AND CRUDE OIL IN
UAE?
Crude Oil production has been the mainstay of the
economy in the UAE and will remain a major
revenue earner long into the future, due to the vast
hydrocarbon reserves at the country’s disposal.
Proven recoverable oil reserves are currently put at
98.2 billion barrels or 9.5 percent of the global
crude oil proven reserves.
LISTEN...LEARN...THINK...GROW 13
CRUDE OIL
REFINERIES
Refinery: From Crude to Useful
Products
LISTEN...LEARN...THINK...GROW 14
LISTEN...LEARN...THINK...GROW 15
WORLD’S REFINERIES
Petroleum refineries are marvels of modern engineering.
Within them a maze of pipes, distillation columns, and
chemical reactors turn crude oil into valuable products.
Large refineries cost billions of dollars, employ several
thousand workers, operate around the clock, and occupy the
same area as several hundred football stadiums.
Useful Products from crude oil
LISTEN...LEARN...THINK...GROW 16
Petroleum Refining Processes
Petroleum refining processes are the chemical engineering
processes and other facilities used in petroleum refineries
(also referred to as oil refineries) to transform crude oil into
useful products such as liquefied petroleum gas (LPG),
gasoline or petrol, jet fuel, diesel oil and fuel oils.
We will study the following processes:
Hydrodesulfuration as pretreatment
Isomerization
Reforming Catalytic
Thermal cracking
Cooking
LISTEN...LEARN...THINK...GROW 17
LISTEN...LEARN...THINK...GROW 18
ABU DHABI REFINERY
Following the discovery of oil in Abu Dhabi in 1958, and the first export shipments of Crude in 1962, plans were drawn up for a grass root Refinery with a capacity of 15,000 barrels per stream day (BPSD) to meet a growing local need for petroleum products
LISTEN...LEARN...THINK...GROW 19
CRUDE OIL FOR ABU DHABI
REFINERY
The Refinery is a Hydro Skimming
Complex designed to process Bab
Crude as well as a mixture of Asab-
Sahil, Shah and Thammama
Condensate.
LISTEN...LEARN...THINK...GROW 20
REFINERY MAIN UNITS IN
ABU DHABI REFINERY Crude Distillation Unit
Naphtha Hydrodesulphuriser Unit
Kerosene Merox Unit
Catalytic Reformer Unit
Gas Oil Hydrodesulphuriser Unit
LPG Treating and Recovery Unit
Naphtha Stabilizer Unit
Gas Sweetening Unit
Sulphur Recovery Unit
REFINERY FINAL PRODUCTS
LISTEN...LEARN...THINK...GROW 21
LISTEN...LEARN...THINK...GROW 22
STUDY THE MARKET
BEFORE YOU DECIDE We need to study the market in order to adjust the production of each
refinery product to maximize profits
Various fractions are more important at different times of year. During the summer driving months, the public consumes vast amounts of gasoline, whereas during the winter more fuel oil is consumed.
These demands also vary depending upon whether you live in the frigid north, or the humid south.
Modern refineries are able to alter the ratios of the different fractions to meet demand, and maximize profit.
LISTEN...LEARN...THINK...GROW 23
WORLD MARKETS
LISTEN...LEARN...THINK...GROW 24
FROM THE WORLD MARKET DISTILLATE AND GASOLINE ARE THE TWO MOST
IMPORTANT PRODUCTS
LIGHT CRUDE OILS CAN SATISFY THE MARKET BETTER
THAN HEAVY CRUDE OILS
FROM HEAVY CRUDE OILS , CRACKING PROCESSES ARE
NEEDED TO OBTAIN SMALLER CHAINS HYDROCARBONS
AS DISTILATE AND GASOLINE
Classification of Crude
Oils
WTI or Brent
Light or Heavy
Sweet or Sour
LISTEN...LEARN...THINK...GROW 25
LISTEN...LEARN...THINK...GROW 26
CLASSIFICATION OF CRUDE
OILS
The oil industry classifies "crude" by the location of its origin (e.g., "West Texas Intermediate, WTI" or "Brent")
Often by its relative weight or viscosity ("light", "intermediate" or "heavy");
Refiners may also refer to it as "sweet," which means it contains relatively little sulfur, or as "sour," which means it contains substantial amounts of sulfur and requires more refining in order to meet current product specifications.
Each crude oil has unique molecular characteristics which are understood by the use of crude oil assay analysis in petroleum laboratories.
Brent Blend
Brent blend is a light crude oil (LCO), though not as
light as West Texas Intermediate (WTI). It contains
approximately 0.37% of sulphur, classifying it as
sweet crude, yet not as sweet as WTI.
Brent is suitable for production of petrol and middle
distillates. It is typically refined in Northwest Europe.
Brent Crude has an API gravity of around 38.06 and
a specific gravity of around 0.835.
LISTEN...LEARN...THINK...GROW 27
WTI Crude Oil
WTI is a light crude oil, with an API gravity of around
39.6 and specific gravity of about 0.827, which is
lighter than Brent crude.
It contains about 0.24% sulfur thus is rated as a sweet
crude oil (having less than 0.5% sulfur), sweeter than
Brent which has 0.37% sulfur.
WTI is refined mostly in the Midwest and Gulf Coast
regions in the U.S.
LISTEN...LEARN...THINK...GROW 28
LISTEN...LEARN...THINK...GROW 29
HYDROCARBONS IN
CRUDE OILS
COMPOSITION OF PETROLEUM
(PAGES 62-64)
LISTEN...LEARN...THINK...GROW 30
BASICS OF HYDROCARBON
CHEMISTRY
Crude oil is a mixture of hydrocarbon molecules, which are organic compounds of carbon and hydrogen atoms that may include from one to 60 carbon atoms.
The properties of hydrocarbons depend on the number and arrangement of the carbon and hydrogen atoms in the molecules.
Hydrocarbons containing up to four carbon atoms are usually gases, those with 5 to 19 carbon atoms are usually liquids, and those with 20 or more are solids.
LISTEN...LEARN...THINK...GROW 31
THE MAIN HYDROCARBONS
OF CRUDE OILS Paraffins
Aromatics
Naphtenes
Other hydrocarbons:
Alkenes
Dienes and Alkynes
LISTEN...LEARN...THINK...GROW 32
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.
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).
LISTEN...LEARN...THINK...GROW 33
THE SIMPLEST PARAFFIN
METHANE
LISTEN...LEARN...THINK...GROW 34
C4H10
BUTANE AND ISOBUTANE
LISTEN...LEARN...THINK...GROW 35
AROMATICS
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.
LISTEN...LEARN...THINK...GROW 36
AROMATIC COMPOUND
BENZENE (C6H6 )
LISTEN...LEARN...THINK...GROW 37
DOUBLE-RING AROMATIC
COMPOUND
NAPTHALENE (C10 H8)
LISTEN...LEARN...THINK...GROW 38
NAPHTHENES
(monocycloparaffins)
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.
CLASSIFICATION OF
CRUDE OILS
LISTEN...LEARN...THINK...GROW 39
LISTEN...LEARN...THINK...GROW 40
CHARACTERIZATION OF
CRUDE OILS ?
Attempts have been made to use
Distillation ranges in order to classify
crude oils as :
Paraffinic
Naphtenic
Aromatic
LISTEN...LEARN...THINK...GROW 41
CRUDE OILS ARE DEFINED AS :
Paraffin base
Naphtene base
Asphalt base
Mixed based
Aromatic base ( up to 80% aromatics)
LISTEN...LEARN...THINK...GROW 42
CRUDE OIL CLASSIFICATION
in order of decreasing value
1) PARAFFINIC CRUDE OILS
paraffins + naphthenes > 50%
paraffins > naphthenes
paraffins > 40%
2) NAPHTHENIC CRUDE OILS
2) paraffins + naphthenes > 50%
naphthenes > paraffins
naphthenes > 40%
LISTEN...LEARN...THINK...GROW 43
CRUDE OIL CLASSIFICATION
in order of decreasing value
3) PARAFFINIC- NAPHTENIC CRUDE OILS
Aromatics < 50%
paraffins < 40%
naphthenes < 40%
4) AROMATIC- NAPHTENIC CRUDE OILS:
Aromatics > 50%
naphthenes > 25%
paraffins < 10%
LISTEN...LEARN...THINK...GROW 44
CRUDE OIL CLASSIFICATION
in order of decreasing value
5)AROMATIC- INTERMEDIATE CRUDE OILS
Aromatics > 50%
paraffins > 10%
6)AROMATIC- ASPHALTIC CRUDE OILS
naphthenes > 25%
paraffins < 10%
LISTEN...LEARN...THINK...GROW 45
PROBLEMS WITH HEAVY CRUDE
OILS
The heavier a crude oil is, the more difficult a challenge it presents in extracting it from the ground and purifying it into end products.
Crude oil's physical properties, such as viscosity, and its chemical impurities affect the cost of recovery and refining, and the amount of waste produced in processing.
New air-pollution regulations have tightened the restrictions on the amount of impurities, such as sulfur, that can remain in petroleum products used as fuel.
LISTEN...LEARN...THINK...GROW 46
HEAVY CRUDE OILS
SITUATION IN THE MARKET
So, oil companies have focused on bringing up the
lighter oil and leaving denser oil under ground.
Moreover, due to increased refining costs and high
sulfur content, heavy crude oils are often priced at a
discount to lighter ones.
LISTEN...LEARN...THINK...GROW 47
LIGHT CRUDE OILS AND
GLOBAL MARKET
But industry predictions show that the supply of
light crude oils is dwindling, leaving an increasing
proportion of heavy grades for future use.
In fact, most of the Western Hemisphere's
remaining oil is heavy crude, creating a strong
strategic incentive to find new ways to extract and
use it.
LISTEN...LEARN...THINK...GROW 48
COST INVOLVED FOR
HEAVY CRUDE OILS
The increased viscosity and density also makes
production more difficult.
Large quantities of heavy crude oils have been
discovered in the Americas including Canada,
Venezuela and Northern California.
The relatively shallow depth of heavy oil fields
(often less than 3000 feet) contributes to low
drilling costs.
LISTEN...LEARN...THINK...GROW 49
PROPERTIES OF HEAVY
CRUDE OILS
Heavy crude oil is asphaltic. It is "heavy" (dense and
viscous).
heavy crude oils with a high content of naphthenic
compounds, such as asphaltenes.
Asphaltic crude oils are also known as naphthene-
based crude oil when the paraffin wax content is low (
< 10%)
Heavy oil has over 60 carbon atoms and hence a high
boiling point and molecular weight.
LISTEN...LEARN...THINK...GROW 50
ENVIRONMENTAL ISSUE OF
HEAVY CRUDE OILS
As a rule, heavy crude oils have a more severe
environmental impact than light ones.
Heavy crude oils also carry contaminants. For example,
Orinoco extra heavy oil contains 3.5% sulfur as well as
vanadium and nickel
Heavy crude oils contain more carbon in relation to
hydrogen, thus releasing more CO2 (believed to be
responsible for climate change) per amount of usable
energy when burned.
LISTEN...LEARN...THINK...GROW 51
CHARACTERIZATION OF
CRUDE OIL
PROPERTIES/ASSAY
Pages 57-70
LISTEN...LEARN...THINK...GROW 52
WHY CHARACTERIZE
CRUDE OILS ?
Crude grades vary considerably from each other - in yield
and properties.
Crude characterization is essential to estimate:
Feedstock properties for refinery units,
Produce an optimal amount of final products
Meet product quality specifications
Provide an economic assessment for crude oils.
LISTEN...LEARN...THINK...GROW 53
CRUDE CHARACTERIZATION
IS UTILIZED BY: UPSTREAM PLANNING
To determine the economic viability of new fields / discoveries
SUPPLY ORGANIZATIONS
To assign crude value for individual grades
REFINERY OPERATIONS
To schedule crude receipts and determine product yields
MODEL ENGINEERS
To optimize refinery crude slates
RESEARCH & DEVELOPMENT
To design equipment and process planning
LISTEN...LEARN...THINK...GROW 54
HOW TO CHARACTERIZE
CRUDE OILS
Because crude oils contain hundreds of
hydrocarbons and therefore exact composition of
crude oils is unknown
We need other methods to characterize crude oils
Properties of crude oils are then defined by
different assay.
LISTEN...LEARN...THINK...GROW 55
WHAT IS A CRUDE OIL ASSAY?
An efficient assay is derived from a series of test data is then used to give an accurate description of crude oil quality.
These properties allow an indication of crude oil behavior during the refining processes
LISTEN...LEARN...THINK...GROW 56
THE IMPORTANCE OF CRUDE
OIL ASSAYS
Knowing what your crude is worth begins by
having good crude assay data.
The identification of chemical and physical
properties of crude oil provides the basis for
economic valuation, engineering design and
refinery processing.
LISTEN...LEARN...THINK...GROW 57
THE MOST IMPORTANT ASSAY
Density or API Gravity
Distillation range
Characterization Factor
Pour point
Carbon residue
IMPURITIES :
Sulfur Content
Salt content
Nitrogen Content
LISTEN...LEARN...THINK...GROW 58
SPECIFIC GRAVITY OF
CRUDE OIL
LISTEN...LEARN...THINK...GROW 59
DEFINITION OF DENSITY
Density ( ASTM D-1298, IP 160) is an important property used to determine the quality of crude oils
Petroleum and petroleum products are usually bought or sold on the density basis
Definition: Density of a crude oil is the mass of oil by unit volume at 150C
In laboratories, hydrometers, pycnometers or modern digital density meter are used to measure specific gravity
LISTEN...LEARN...THINK...GROW 60
CRUDE OIL’S API GRAVITY
Crude oils are defined in terms of API (American
Petroleum Institute) gravity.
The higher the API gravity, the lighter the crude.
Crude oils API gravity may range from less than
100API to over 500 API but most crude oils fall in
the 20 to 450 API
LISTEN...LEARN...THINK...GROW 61
WHAT IS 0API?
°API of different crude oils Light crude oil is defined as having an API gravity higher than
31.1 °API (less than 870 kg/m3)
Medium crude oil is defined as having an API gravity between
22.3 °API and 31.1 °API (870 to 920 kg/m3)
Heavy crude oil is defined as having an API gravity below 22.3
°API (920 to 1000 kg/m3)
Extra heavy crude oil is defined with API gravity below 10.0
°API (greater than 1000 kg/m3)
LISTEN...LEARN...THINK...GROW 62
LISTEN...LEARN...THINK...GROW 63
API DENSITY AND TYPE OF
HYDROCARBONS
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 VALUABLE CRUDE OIL
Those with high carbon, low hydrogen, and low API gravities are usually rich in aromatics and more impurities LESS VALUABLE CRUDE OIL
LISTEN...LEARN...THINK...GROW 64
True Boiling Point or TBP
Curve
DISTILLATION TEST
LISTEN...LEARN...THINK...GROW 65
TRUE BOILING POINT ( TBP)
A Distillation Curve
A plot of the boiling points ( temperatures) of crude oil versus % volume of distilled fractions
TBP crude oil distillations by ASTM D 5236
LISTEN...LEARN...THINK...GROW 66
TBP OF CRUDE OIL IS A KEY
ASSAY FOR REFINERIES
A full and comprehensive evaluation of the crude
starts with a True Boiling Point Distillation
The distillation test is a method used to give an
indication of the types of the products that can be
obtained by the crude oils
A boiling range of the crude oil gives an indication of
the quantities of the various products present
LISTEN...LEARN...THINK...GROW67
CRUDE OIL TBP ASSAY IN
OUR LAB
LISTEN...LEARN...THINK...GROW 68
RESULT OF THE EXPERIMENT:
TRUE BOILING CURVE OF CRUDE OIL
LISTEN...LEARN...THINK...GROW 69
ATMOSPHERIS AND VACUUM
DISTILLATION
ASTM D-86 ( Atmospheric distillation):
This test is carried out at atmospheric pressure and is
stopped at 3000C ( 5720F) to avoid thermal cracking
ASTM D-1160 (Vacuum distillation):
This test method covers the determination, at reduced
pressure, of the boiling temperature ranges of
petroleum products from the residue of the atmospheric
distillation.
LISTEN...LEARN...THINK...GROW 70
DISTILLATION LABS
ATMOSPHERIC AND VACCUM
DISTILLATIONS
LISTEN...LEARN...THINK...GROW 71
LAB for atmospheric distillation
ASTM D-86 ( Atmospheric Distillation):
LISTEN...LEARN...THINK...GROW 72
LAB for Vacuum distillation
ASTM D-1160 (Vacuum distillation):
LISTEN...LEARN...THINK...GROW 73
DISTILLATION RANGES FOR
REFINERY PRODUCTSATMOSPHERIC DISTILLATION PRODUCTS
Butanes and lighter 55-175 0F-
Light Gasoline 175-300 0F
Light naphtha 300-400 0F
Heavy naphtha 400-500 0F
Kerosene 500-650 0F
Atmosphere Gas Oil 650-800 0F
VACUUM DISTILLATION PRODUCTS
Light Vacuum Gas Oil (LVGO) 800-1000 0F
Heavy. Vacuum Gas Oil (HVGO) 1000 0F
Vacuum Residue > 1000 0F
Measuring the Density of
different fractions
LISTEN...LEARN...THINK...GROW 74
LISTEN...LEARN...THINK...GROW 75
0API VERSUS % VOLUME
DISTILLED FRACTION
LISTEN...LEARN...THINK...GROW 76
ASSAY TO DETERMINE
GASES IN CRUDE OILS
BY GAS CHROMATOGRAPHY
LISTEN...LEARN...THINK...GROW 77
LIGHT HYDROCARBONS OR
GASES IN CRUDE OILS
The amount of the individual light
hydrocarbons in crude oils ( methane to butane)
is often included as part of a preliminary assay
The identification and quantification of each
light component is carried out by GC or gas
chromatography ( ASTM D-2427)
LISTEN...LEARN...THINK...GROW 78
CLASS WORK #1
Study appendix C ( page 415)
about the specifications of
different crude oils
Group discussion
LISTEN...LEARN...THINK...GROW 79
CLASS WORK #2
Study the data of the crude oil given in figure 3.5 page 66:
1) Define its type knowing its density
Draw the TBP curve ( Temperature versus the percentage distilled using figure 3.6 page 67 for the products of vacuum distillation)
Draw the API curve ( 0 API versus the percentage distilled)
Perform an approximate material balances of the refinery using this crude oil using the typical ranges of refinery products (given above).
LISTEN...LEARN...THINK...GROW 80
CHARACTERIZATION
OF CRUDE OILS
LISTEN...LEARN...THINK...GROW 81
THE NEED FOR
CHARACTERIZATION FACTORS
Problems arise at ranges above 2000C, since molecules can not be placed in one group ( naphthenic/ aromatic or cyclic/ paraffinic)
To overcome this situation, characterization factors based on specific gravity and TBP distillation were introduced to characterize the different crude oils
LISTEN...LEARN...THINK...GROW 82
CHARACTERIZATION OF
CRUDE OILS
The two mostly used correlations between yield
and aromaticity and paraffinicity of crude oils are:
UOP or Watson Characterization factor
( KW)
US bureau of Mines Correlation index
(CI)
LISTEN...LEARN...THINK...GROW 83
WATSON CHARACTERIZATION
TB is the average boiling point in 0R
S.G is the specific gravity at 600F
KW ranges from less than 10 for highly aromatic crude oils to almost 15 for highly paraffinic crude oils
KW ranges 10.5-12.5 for highly naphtenic (Cyclic) crude oils and 12.5 -13 for highly paraffinic crude oils
GS
TK B
W.
3/1
84
CORRELATION INDEX (CI) THE CORRELATION INDEX ( CI) IS BASED ON THE PLOT OF SPECIFIC
GRAVITY VS THE RECIPROCAL OF THE BOILING POINT IN
S.G is the specific gravity at 600F
the CI is useful for individual fractions ( PRODUCTS)
CI is based on straight paraffins having CI = 0 and benzene having CI =100
Low CI ( 0-15) indicates great concentration of paraffins in the fraction
Average CI ( 15-50) indicate a predominance of naphthenes or a mixture of paraffins, naphthenes and aromatics
High CI ( above 50) indicates great concentration of aromatics
8.456.7.47387552
GxST
CIB
CLASS WORK
Solve problems 1, 2 and 3 page 68
LISTEN...LEARN...THINK...GROW 85
LISTEN...LEARN...THINK...GROW 86
KINEMATIC
VISCOSITY
LISTEN...LEARN...THINK...GROW 87
DEFINITION
Viscosity is a measure of the resistance of a
fluid to deform under shear stress.
It is commonly perceived as "thickness", or
resistance to flow.
Viscosity describes a fluid's internal resistance to
flow and may be thought of as a measure of fluid
friction.
LISTEN...LEARN...THINK...GROW 88
KINEMATIC VISCOSITY
In many situations, we are concerned with the ratio of the viscous force to the inertial force, the latter characterized by the fluid densityρ.
This ratio is characterized by the kinematic viscosity (ν), defined as follows:
ν =μ/ρ
.
where η is the dynamic viscosity, and ρ is the density.
Kinematic viscosity (Greek symbol: ν) has SI units (m²·s-1).
It is sometimes expressed in terms of centistokes (cS or cSt). In U.S. usage, stoke is sometimes used as the singular form.
1 stokes = 100 centistokes = 1 cm2·s−1 = 0.0001 m2·s−1.
1 centistokes = 1 mm²/s
LISTEN...LEARN...THINK...GROW 89
KINEMATIC VISCOSITY OF
CRUDE OILS
Kinematic viscosity is usually
determined at 250C ( 770F) and 1000C
(2120F) by measuring the time for a
volume of liquid to flow under gravity
through a calibrated glass capillary
viscometer ( ASTM D-445)
LISTEN...LEARN...THINK...GROW 90
WHY KINEMATIC VISCOSITY OF
CRUDE OILS IS IMPORTANT
Cost of exploitation and transportation of
crude oils depends on its kinematic
viscosity
Light crude oils have small kinematic
viscosity and then transportation cost are
low
LISTEN...LEARN...THINK...GROW 91
HIGH VISCOSITY OF VENEZUELA
AND CANADIAN CRUDE OILS
For example, the viscosity of Venezuela's
Orinoco extra-heavy crude oil lies in the range
1000-5000 cP.
Canadian extra-heavy crude has a viscosity in
the range 5000-10,000 cP.
LISTEN...LEARN...THINK...GROW 92
LAB #4 ( KINEMATIC
VISCOSITY)
LISTEN...LEARN...THINK...GROW 93
POUR POINT
LISTEN...LEARN...THINK...GROW 94
DEFINITION OF POUR
POINT
The pour point of a liquid is the lowest temperature at which it will pour or flow under prescribed conditions. It is a rough indication of the lowest temperature at which oil is readily pumpable.
Also, the pour point can be defined as the minimum temperature of a liquid, particularly a lubricant, after which, on decreasing the temperature, the liquid ceases to flow.
LISTEN...LEARN...THINK...GROW 95
CRUDE OILS BEHAVIOR AT
LOW TEMPERATURES
Viscosity and Pour point determinations are
performed to give us information about flow
characteristics of crude oils at low
temperatures
Some general information about the type of
crude oil can be derived from its pour point
data
LISTEN...LEARN...THINK...GROW 96
POUR POINT OF CRUDE
OILS
The Pour point of crude oil is indicate the lowest temperature at which the crude oil will flow under specific conditions
The maximum and the minimum Pour points temperatures provide the range of temperatures in which the crude oil might appear in liquid form as well as in solid form
LISTEN...LEARN...THINK...GROW 97
POUR POINT OF CRUDE
OILS
Pour Point of crude oil is the temperature at which
the oil no longer flows when tilted in a test jar; the
liquid phase is trapped within the PARAFFIN
CRYSTAL STRUCTURE
The paraffins are the first components to crystallize
under low temperatures
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PROBLEMS RELATED TO
POUR POINTS
The production and transportation of
crude oil and its fractions can be
significantly affected by deposition of
paraffin and asphaltenes in the reservoir
rock tubulars, pumps, vessels, and
pipelines.
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ADDITIVES FOR
CRYSTALLIZATION PROBLEMS The Pour point is also used to screen the effects of wax
interactions modifiers on the flow behavior of the crude oil
In a gas-oil NON-FLOW CONDITIONS happen at about
1% crystallization
whereas in a crude oil this happens at 2% crystallization.
The additives used to achieve this are usually referred to
as Pour Point Depressants or PPD’s.
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LAB # 6 ( POUR POINT)
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CARBON RESIDUE
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CARBON RESIDUE
The Carbon residue is roughly related to the
asphalt of the crude oil and to the quantity of the
lubricating oil fraction that can be converted
Determined by distillation to a coke residue in the
absence of air
The lower the Carbon Residue, the more
valuable is the crude
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CARBON=POISON TO
CATALYSTS
Carbon residue cause rapid deactivation of
catalysts and high catalysts cost
For ARC feeds, we use catalytic processes
For VRC, we use non-catalytic processes
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CRUDE OIL
IMPURITIES
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INTRODUCTION
Crude oil is a dense, dark fluid
containing many varieties of complex
hydrocarbon molecules, along with
organic impurities containing sulfur,
nitrogen, and heavy metals.
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SULFUR COMPOUNDS IN
HEAVY CRUDE OILS
Hydrogen sulfide (H2S),
Compounds (e.g. mercaptans, sulfides, disulfides,
thiophenes, aphthenes, etc.
Elemental sulfur
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SULFUR REFINERY
PROBLEMS
Sulfur presence in crude oil is detrimental to the processing because sulfur can act as catalyst poisons during processing
Compounds containing sulfur cause also equipment corrosion and atmospheric pollution when products are burned
The sulfur content in crude oil varies from 0.1% to 3% weight and a sulfur content up to 8% was found in tar sand bitumen
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SULFUR IN CRUDE OILS
Crude oils with less than 0.5% of sulfur are called sweetcrude oil and the crude oils with more than 0.5% are called sour crude oils
Sour crude oils require special processing and are then less expensive than the sweet crude oils
One of the most used technique to evaluate the percentage of sulfur is the combustion of a sample in oxygen to convert sulfur to sulfur dioxide which is titrated iodometrically or detected by nondipersive infrared ( astm D-1552)
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OXYGEN COMPOUNDS
Oxygen compounds such as phenols,
ketones, and carboxylic acids occur in crude
oils in varying amounts
Nitrogen is found in lighter fractions of crude
oil and more often in heavier fractions of crude
oil as non- basic compounds
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NITROGEN CONTENT
A high nitrogen content is undesirable in crude
oils before organic nitrogen compounds cause
severe poisoning of catalysts and corrosion of
equipments
Crude oils containing nitrogen above 0.25% by
weight require special processing to remove
the nitrogen
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METAL CONTENT ( PPM)
Metals found in crude oils come from the reservoir itself but also during recovery, transportation and storage.
Even traces of metals can be deleterious to processes using catalysts but can also cause corrosion and affect the quality of products
Trace Metals. Metals, including nickel, iron, and vanadium are often found in crude oils in small quantities
Test methods such as Atomic Absorption Spectrometry, X-ray fluorescence spectroscopy are used to determine the amounts of metals
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SALTS IN CRUDE OILS
Salts. Crude oils often contain inorganic salts such as sodium
chloride, magnesium chloride, and calcium chloride in
suspension or dissolved in entrained water (brine).
Salts in crude oils come mostly from production practices used
in the field but at some extent from handling to tankers bringing
it to terminals
Most of the salts are dissolved with coexisting water and
removed in desalters but some can be dissolved in the crude oil
itself
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SALTS CONTENT
Salts can accumulate in stills, heaters and
exchangers leading to fouling that requires expensive
clean up.
Salts content can be determined by potentiometric
titration
The amount of salts in crude oils is important to
decide whether and to what extent the crude oil needs
desalting
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OTHER IMPURITIES WITH
SMALLER AMOUNTS
Carbon Dioxide
Naphthenic Acids: Some crude oils
contain naphthenic (organic) acids
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CONCLUSION ON CRUDE
OILS PROPERTIES
API Gravity: oAPI defined asoAPI= (141.5/ sp.gr.) -131.5
Most crude oils fall in the 20-45 0API range ( the reference temperature is 600F ( 15.60C)
TBP Curve
Sulfur Content ( wt%)
Sulfur content can be from 0.1% to 5%
More than 0.5%, crude are sour and need special processing
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INTERPRETATION OF
PROPERTIES
Pour point: Low pour point means lower paraffin and the greater the content of aromatics
Carbon Residue ( wt%): Related to asphalt content and to the quantity of the lubricating oil that could be recovered
Salt Content ( lb/ 1000bbl): If the salt content , when expressed as NaCl, is greater than 10 lb/ 1000bbl ( 30 ppm), it is necessary to desalt the crude in order to avoid corrosion
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MAJOR REFINERY PRODUCTS
DUE TO THE ACTUAL MARKET
LPG
Gasoline
Jet fuels
Diesel fuels
Home heating oils
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SPECIFICATIONS OF
REFINERY FINAL
PRODUCTS
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WHAT IS LPG?
Varieties of LPG bought and sold include mixes that are primarily propane, mixes that are primarily butane, and the more common, mixes including both propane (60%) and butane(40%).
Depending on the season—in winter more propane, in summer more butane.
Propylene and butylenes are usually also present in small concentration.
A powerful odorant, ethanethiol, is added so that leaks can be detected easily
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SECURITY FOR LPG
STORAGE IN REFINERIES Large, spherical LPG containers may have up to a
15 cm steel wall thickness.
Ordinarily, they are equipped with an approved pressure relief valve on the top, in the centre.
One of the main dangers is that accidental spills of hydrocarbons may ignite and heat an LPG container, which increases its temperature and pressure, following the basic gas laws.
The relief valve on the top is designed to vent off excess pressure in order to prevent the rupture of the tank itself
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STORAGE OF COMMERCIAL
PROPANE AND BUTANE FOR
HOMES
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SECURITY FOR BOTTLES In order to allow for thermal expansion of the contained
liquid, these bottles are not filled completely; typically, they are filled to between 80% and 85% of their capacity.
Vapor pressure of LPG is approximately 220 kilopascals(2.2 bar) for pure butane at 20 °C (68 °F), and approximately 2.2 megapascals (22 bar) for pure propane at 55 °C (131 °F).
LPG is heavier than air, and thus will flow along floors and tend to settle in low spots, such as basements. This can cause ignition or suffocation hazards if not dealt with.
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MAIN USE OF LPG:
HEATING AND ENGINES
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PROPERTIES OF
COMMERCIAL PROPANE Vapor pressure ( PSIG)
700F = 124
1300F = 286
S.G liquid (60/600F) = 0.509
Limits of flammability (vol% gas in air)
Lower limit = 2.4
Upper limit = 9.6
Gross heating values:
Btu/ft3 gas = 2,560
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PROPERTIES OF
COMMERCIAL BUTANE
Vapor pressure ( PSIG)
700F = 31
1300F = 97
S.G liquid (60/600F) = 0.582
Limits of flammability (vol% gas in air)
Lower limit = 1.9
Upper limit = 8.6
Gross heating values:
Btu/ft3 gas = 3,350
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Motor gasoline characteristics: The critical properties are:
* Ried vapor pressure ( RVP): Vapor pressure is a measure of the surface pressure it takes to keep the liquid from vaporizing. RVP is measured at 100oF
* RVP of gasoline must meet two conditions:
- On cold start , enough gasoline must vaporize to provide ignitable mixture
- On hot restart, the gasoline should not expand in the injection apparatus and must let air to come in
* Boiling range ( 100 -4000F)
* Antiknock characteristics: PON
* Desirable sulfur content is < 300 PPM
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Octane number?
Definition: A value used to indicate the resistance of a motor fuel to knock. Octane numbers are based on a scale on which isooctane is 100 (minimal knock) and heptane is 0 (bad knock).
Example: A gasoline with an octane number of 92 has the same knock as a mixture of 92% isooctane and 8% heptane.
We can measure antiknock by using the octane number :
PON: posted octane number
MON: motor octane number
RON : research octane number
Antiknock performance is the main difference between the grades of gasoline
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Posted Method Octane
number
Gasoline pumps typically post octane numbers as an average of two different values. Often you may see the octane rating quoted as PON=(RON+MON)/2.
One value is the research octane number (RON), which is determined with a test engine running at a low speed of 600 rpm ( performance inside cities).
The other value is the motor octane number (MON), which is determined with a test engine running at a higher speed of 900 rpm ( performance in high ways).
If, for example, a gasoline has an RON of 98 and a MON of 90, then the posted octane number would be the average of the two values or PON= 94.
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CLASS WORK
WORK EXAMPLE 10.3.1 PAGE 216
DISTILLATE FUELS
Jet fuel
Diesel fuel
Heating fuels
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WHAT IS JET FUEL? The most expensive distillate fuel
Used for commercial aviation and military aircraft
Known also as turbine fuels
Primary fraction of jet fuel blending is the kerosene fraction from Atmospheric distillation
Characteristics:
The most important characteristic: No freezing in the cold temperatures of the skies ( -500C)
LAB ABOUT FREEZING POINT OF FUELS
Smoke point expressed in mm of flame height at which smoke is detected ( environment)
Volume percent of total aromatics less than 20% and naphthalene less than 3%
CLASS WORK
Study the different specifications of the jet fuels in
table 2-8 page 52
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WHAT IS AUTOMOTIVE
DIESEL FUEL?
Used for high speed engines such as trucks and buses
Boiling range : 360-6000F (182-3160C)
Critical properties are : volatility, viscosity, ignition quality, sulfur content, percent of aromatics and cloud point.
The cloud point of a fuel is the temperature at which the fuel becomes hazy or cloudy because of the appearance of wax crystals
Ignition properties are expressed as CETANE NUMBER
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CETANE NUMBER?
Comparable to the octane number for gasoline.
A rating on a scale used to indicate the tendency of a fuel for diesel engines to cause knock.
The rating is comparing the fuel’s performance in a standard engine with that of a mixture of cetane ( HIGH IGNITION QUALITYCN=100) and alpha-methyl-naphthalene ( LOW IGNITION QUALITYCN=0).
The cetane number is the percentage by volume of cetane in the mixture that has the same performance as the fuel being tested.
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WHAT IS A HEATING OIL?
Fuel oils No1 and No2:
Fuel oil No1 is similar to kerosene (Jet Fuel) but generally has a:
* higher pour point ( Defined as 50F higher than the temperature at which a liquid stops flowing)
*higher end point ( Defined as the lowest temperature at which virtually 100% of a product will boil off to vapor form)
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WHAT IS FUEL OIL N02
Similar to diesel fuel
Blended from naphtha, kerosene, diesel, and
cracked gas oil
Critical properties are sulfur content, pour point,
distillation and flash point
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WHAT IS RESIDUAL FUEL OIL ?
Composed of the heaviest part of crude oil and is
generally from bottoms of vacuum distillation
The critical properties are viscosity and sulfur content
Used in furnaces
CLASS WORK
tudy the different characteristics of the fuel oils in
table 2-9 page 54
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REFINERY PROCESSES
Step I : Pretreatment
Step II Separations
Step III : Chemical transformation
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CLASS WORK :
STUDY FIGURE 1.1 PAGE 3
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CRUDE OIL
PRETREATMENT
DESALTING
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INTRODUCTION Historically, the main problems associated with salt in crude oil
were corrosion and fouling in the crude unit overheads.
As downstream treatment and conversion processes assume
an ever greater importance in refinery economics and
operations, sodium poisoning of catalysts and fouling in
downstream units become increasing concerns.
Many refiners are turning to desalter upgrades and expansions
to solve the problem at source
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PROBLEMS CAUSED BY THE
PRESENCE OF SALTS The salts that are most frequently present in crude oil
are calcium, sodium and magnesium chlorides.
Technical problems:
Sand, silts and salt cause deposits and foul heat exchangers.
The high temperatures that occur downstream in the process could cause water hydrolysis, which in turn allows the formation of corrosive hydrochloric acid
Sodium, arsenic and other metals can poison catalysts
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CRUDE OIL DESALTING
A desalter is a process unit in an oil refinery that removes salt from the crude oil. The salt is dissolved in the water in the crude oil, not in the crude oil itself.
The desalting is usually the first process in crude oil refining. The salt content after the desalter is usually measured in PTB - pounds of salt per thousand barrels of crude oil.
Usually desalting is necessary only when the salt content of a crude oil is greater than 10 lb/ 1000bbl (expressed as NaCl)
But now almost all crude oils are desalted to increase the efficiency of the refineries
Objectives of desalting
The basic principle is to wash the salt from crude oil
using water
Secondary but important function of desalting is to
remove solid particles from crude oil
These are usually fine sands, clays and soil particles
, iron oxides and iron sulfide particles from pipelines,
tanks and tankers
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Electrostatic De-salter
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Description of the process The dehydration process of a desalter will reduce a
portion of the free brine as it exits the vessel. A certain
quantity of brine will continue to exit as an emulsion.
Depending on the product specifications, one, two, or
three stages of desalting may be required to satisfy
the process design requirements.
Recycling reduces dilution/wash water consumption
and disposal costs of the effluents.
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THE DESALTING PROCESS
Washing the crude with 3 to 10% vol. of water
at 200-3000F then separating the water
AC or DC potentials from 12,000 to 35,000 V
are used
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TECHNICAL PROBLEMS OF
THE PROCESS
The salt in crude oil is dissolved or in suspended salt crystals
in water emulsified with the crude oil.
Technical problems occur in
obtaining efficient water/ oil mixing
water-wetting of suspended particles
separation of the wash water from oil
the process is affected by :
pH, gravity and viscosity of crude oil
vol. of wash water by vol. of crude oil
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TYPICAL DESALTING
CONDITIONS
0API Water ( %Vol.) Temp (0F)
> 40 3-4 240-260
30 -40 4-7 260-280
< 30 7-10 280-330
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CLASS WORK
Study in group the desalting process
(Figure 4.6 PAGE 80)
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PREHEATING AFTER
DESALTING Following the desalter, the crude oil is further heated by exchanging heat
with some of the hot, distilled fractions and other streams. It is then heated in
a fuel-fired furnace (fired heater) to a temperature of about 398 °C and
routed into the bottom of the first distillation unit.
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STEP II: DISTILLATION AS
SEPARATION PROCESS
For any refinery, the first step is to separate the crude oil
into different fractions using distillation techniques.
two distillation columns are used ( atmospheric and
vacuum)
The amount of each fraction depends on the TBP curve of
the crude oil.
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STEP III: CHEMICAL AND THERMAL
PROCESSES TO PRODUCE MORE
GASOLINE
STEP II : SEPARATION
OF CRUDE OIL INTO
FRACTIONS
DISTILLATIONS
(ATM AND VACCUM)
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Step II: Crude distillation
The crude atmospheric and vacuum distillations are the first majorprocessing units in any refinery.
They are used to separate the crude oils into fractions according toboiling point so that each of the processing units following will havefeedstock that meet their particular specifications.
Higher efficiencies and lower costs are achieved if the crude oilseparation is accomplished in two steps:
First by fractionating the total crude oil at essentiallyatmospheric pressure;
Then by feeding the high-boiling bottoms fraction (topped oratmospheric reduced crude) from the atmospheric still to asecond fractionator operated at a high vacuum
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OVERVIEW OF THE TWO
DISTILLATION UNITS
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ATMOSPHERIC AND VACUUM
DISTILLATIONS
Atmospheric distillation operates under atmospheric
pressure and a gradient of temperatures from high
temperature in the bottom to low temperature at the
top
Vacuum distillation operates at very low pressure to
avoid thermal cracking of the heavy fractions
The fractions are separated according to their boiling
point
Vacuum Distillation
The vacuum still is employed to separate the
heavier portion of the crude oil into fractions
because the high temperatures necessary to
vaporize the topped crude at atmospheric
pressure cause thermal cracking to occur, with
the resulting loss to dry gas, discoloration of
the product, and equipment fouling due to coke
formation.
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CRUDE DISTILLATION UNIT
PRODUCTS
Fuel gas: The fuel gas consists mainly of methane and ethane. In some
refineries, propane in excess of LPG requirements is also included in the
fuel gas stream. This stream is also referred to as ‘‘Dry gas.’’
Wet gas: The wet gas stream contains propane and butanes as well as
methane and ethane. The propane and butanes are separated to be used
for LPG and, in the case of butanes, for gasoline blending and alkylation unit
feed.
LSR or Light Straight-Run Naphtha: The stabilized LSR naphtha (or LSR
gasoline) stream is desulfurized and used in gasoline blending or processed
in an isomerization unit to improve octane before blending into gasoline.
CRUDE DISTILLATION UNIT
PRODUCTS
HSR naphtha or HSR gasoline: The naphtha cuts are generally used ascatalytic reformer feed to produce high-octane reformate for gasolineblending and aromatics.
Gas oils: The light, atmospheric, and vacuum gas oils arm processed in ahydrocracker or catalytic cracker to produce gasoline, jet, and diesel fuels.The heavier vacuum gas oils can also be used as feedstocks for lubricatingoil processing units.
Residuum: The vacuum still bottoms can be processed in a visbreaker,coker, or deasphalting unit to produce heavy fuel oil or cracking and/or lubebase stocks. For asphalt crudes, the residuum can be processed further toproduce road and/or roofing asphalts.
Typical Boiling Ranges of typical
products of the distillation
process
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PROCESS DESCRIPTION OF
ADU (Atmospheric Distillation Unit)
ADU contains around 20 fractionation trays and is equipped with one top pump around, an overhead reflux system, and three side strippers (for naphtha, kerosene, and gas oil products).
The ADU (Atmospheric Distillation Unit) separates most of the lighter end products such as gas, gasoline, naphtha, kerosene, and gas oil from the crude oil.
The bottoms of the ADU is then sent to the VDU (Vacuum Distillation Unit).
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OVERVIEW OF ADU
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TOP OF ADU: LPG AND
GASOLINE PRODUCTS
The condensed gasoline and water are separated
by gravity in the reflux drum. Part of the gasoline is
pumped back to the tower as reflux, with the rest
going to storage.
The water is drained to disposal and the vapor
from the ADU overhead is passed to an untreated
fuel gas system.
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OVERVIEW OF THE TOP OF
ADU
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NAPHTHA PRODUCT
Naphtha draw is located at tray 5.
The naphtha product flows by gravity to the top of
the naphtha stripper.
Stripping steam is used to remove the light ends,
improving the flash point.
The stripped naphtha product is pumped to storage.
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KEROSENE PRODUCT
Kerosene draw is located at tray 12.
The kerosene product flows by gravity to the top of
the kerosene stripper.
Stripping steam is used to remove the light ends,
improving the flash point.
The stripped kerosene product is pumped to storage.
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GAS OIL PRODUCT
At tray 19, a draw pan is located from which gas oil
product is drawn.
The gas oil product flows by gravity to the top of the
gas oil stripper.
Stripping steam is used to remove the light ends,
improving the flash point.
The stripped gas oil product is pumped to storage.
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NAPHTHA + KEROSENE +
GAS OIL PRODUCTS
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ARC :BOTTOM PRODUCT
OF ADU
The liquid part of crude oil ARC is sent for further
processing to the VDU ( Vacuum Distillation Unit).
Steam is injected into the base of the tower to reduce
the hydrocarbon partial pressure by stripping some
light boiling components from the bottoms liquid.
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BOTTOM OF ADU
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ATMOSPHERIC
DISTILLATION PRODUCTS
FUEL GAS C1 AND C2)
LPG (C3 and C4),
Unstabilized light naphtha,
Heavy naphtha,
Kerosene,
Gas oil
TOP (reduced) crude (ARC)
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WHAT DEFINES A GOOD
SEPARATION ?
The relationship between the ASTM distillation temperatures at 95%vol and 5%vol of two adjacent fractions, light and heavy, respectively.
ASTM 5%vol T (heavy) – 95%vol T (light) = DT
(e.g., LGO) (e.g., kerosene)
IF DT > 0, called ASTM gap (good separation)
IF DT < 0, called ASTM overlap (bad separation)
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FACTORS FOR A GOOD
SEPARATION
1) Number of plates
2) Reflux ratio
3) Steam injection - particularly for better separation
of heavy fractions
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CLASS WORK: ADU DISTILLATION
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.
STUDY FIGURE 4.8 PAGE 83
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SECOND DISTILLATION : VDU
OR VACUUM DISTILLATION
The VDU (Vacuum Distillation Unit)
takes the ARC from the Atmospheric
Distillation Unit bottom and separates it
into products such as vacuum gas oil,
vacuum distillate, slop wax, and residue.
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OVERVIEW OF VDU
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PREHEATING OF ARC
ARC is preheated by the bottoms feed
exchanger, further preheated and partially
vaporized in the feed furnace, and passed before
passing to the vacuum tower
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VDU COMPONENTS
This tower contains a combination of 14 fractionation
trays.
It is equipped with three side draws and pump around
sections for
1) Vacuum Gas Oil,
2) Vacuum Distillate
3) Slop Wax products.
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VDU OVERHEAD
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PROCESS OF VDU
OVERHEAD
The overhead from the VDU is condensed and
combined with the vacuum steam.
The slop oil and water are separated by gravity in
the vacuum drum.
The water is drained to disposal, while the slop oil
is accumulated and occasionally drained to slop
collection.
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VDU GAS OIL& DISTILLATE
&SLOP WAX PRODUCTS
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VACUUM GAS OIL
PRODUCT
VGO draw is located at tray 4.
The vacuum gas oil draw tray is also a total draw
tray, where the reflux from the tray is pumped
under flow control to the tray below.
The product and pump around are cooled with the
vacuum gas oil product going to storage, while the
pump around is returned to the tower at tray 1.
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VACUUM DISTILLATE
PRODUCT
The next product draw is located at tray 8, where the draw for
vacuum distillate product is located.
The vacuum distillate draw tray is a total draw tray, where the
reflux from the tray is pumped under flow control to the tray
below.
The product and pump around are cooled, with the vacuum
distillate product going to storage, while the pump around is
returned to the tower at tray 7.
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VACUUM SLOP WAX
PRODUCT
At tray 14, a draw pan is located from which slop
wax product is drawn.
The slop wax product and pump around are
cooled, with the slop wax product going to
storage, while the pump around is returned to the
tower at tray 11.
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VDU BOTTOM PRODUCT
The liquid from the feed furnace enters the tower
bottoms, where it is collected and sent for further
processing.
Steam is injected into the base of the tower to reduce
the hydrocarbon partial pressure by stripping some
light boiling components from the bottoms liquid.
The vapors from the feed heater enter the tower
below tray 14.
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DISTILLATION
SPECIFICATIONS
AND CONTROL
CASE STUDY
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EXAMPLE OF ADU
OPERATING CONDITIONS
The ADU feed is heated to 690 0F before entering
the tower which is maintained at 2.70 PSIG.
The top temperature is controlled at 280 0F which
maintains the Gasoline quality,
Draw temperatures of 355 0 F for the Naphtha, 529 0F for the Kerosene and 583 0F for the Gas Oil.
PROCESS CONTROL
SYSTEM OF ADU
DISTILLATION
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CONTROL OF THE FEED
The ADU feed is pumped by P-100 (HS-100) and
controlled by FIC-100. \
It is preheated in the bottoms feed exchanger (E-
100) before entering the Feed Furnace (F-100).
TIC-100 controls the crude oil temperature
entering the ADU (T-100) by adjusting fuel gas
flow to the furnace.
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CONTROL OF THE BOTTOM
OF ADU
Bottoms liquid is collected and sent to the VDU by
LIC-114 through the Bottoms Pump P-114 (HS-114).
This flow is indicated by FI-124.
Stripping steam is injected into the ADU bottoms by
FIC-134.
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CONTROL OF GAS OIL
QUALITY Hot gas oil flows by gravity to the Gas Oil Stripper (T-113)
through FIC-113.
The gas oil enters the stripper at the top and flows downward over six trays.
Stripping steam is introduced into the bottom of the stripper through FIC-133.
The gas oil product is pumped from the base of the stripper by the Gas Oil Product Pump P-113 (HS-113) to storage.
The gas oil product flow is controlled by LIC-113 and the flow rate is indicated by FI-123.
The gas oil product's 95% point is monitored by AI-123.
LISTEN...LEARN...THINK...GROW 194
CONTROL OF KEROSENE
QUALITY Hot kerosene flows by gravity to the Gas Oil Stripper (T-112)
through FIC-112.
The kerosene enters the stripper at the top and flows downward over six trays.
Stripping steam is introduced into the bottom of the stripper through FIC-132.
The kerosene product is pumped from the base of the stripper by the Gas Oil Product Pump P-112 (HS-112) to storage.
The gas oil product flow is controlled by LIC-112 and the flow rate is indicated by FI-122.
The kerosene product's 95% point is monitored by AI-122.
LISTEN...LEARN...THINK...GROW 195
CONTROL OF NAPHTHA
QUALITY Hot naphtha flows by gravity to the Naphtha Stripper (T-111)
through FIC-111.
The naphtha enters the stripper at the top and flows downward over six trays.
Stripping steam is introduced into the bottom of the stripper through FIC-131.
The naphtha product is pumped from the base of the stripper by the Naphtha Product Pump P-111 (HS-111) to storage.
The naphtha product flow is controlled by LIC-111 and the flow rate is indicated by FI-121.
The naphtha product's 95% point is monitored by AI-121
LISTEN...LEARN...THINK...GROW 196
NAPHTHA PUMP AROUND
A naphtha pump around is drawn from tray 6,
pumped through P-115 (HS-115) and controlled
by FIC-115.
The pump around return temperature is controlled
by TIC-115 which modulates cooling water flow to
E-115.
LISTEN...LEARN...THINK...GROW 197
CONTROL OF GASOLINE
QUALITY The ADU overhead vapor flows through the overhead
condenser E-110 (HV-110), whose outlet temperature is indicated by TI-120, into the Overhead Reflux Drum D-111.
The hydrocarbons are partially condensed and the two phases (vapor and liquid) enter the overhead reflux drum where the condensed water separates from the hydrocarbon liquid by gravity.
The uncondensed gas (FI-130) is sent to fuel gas through PIC-120, which maintains the ADU back pressure.
Analyzers are present to monitor the C3 composition of the off gas (AI-130) and vapor pressure (AI-120) of the gasoline.
PROCESS
CONTROL OF A VDU
DISTILLATION
LISTEN...LEARN...THINK...GROW 198
LISTEN...LEARN...THINK...GROW 199
EXAMPLE OF VDU
OPERATING CONDITIONS
The VDU feed is heated to 750 0F before entering the
tower which is maintained at 2.00 in Hg.
The top draw temperature is controlled at 310 0F
which maintains the Vacuum Gas Oil quality
Draw temperatures of 607 0F for the Vacuum
Distillate, and 668 0F for the Slop Wax.
LISTEN...LEARN...THINK...GROW 200
CONTROL OF THE VDU
FEED
The VDU feed is pumped by P-114 (HS-114)
controlled by LIC-114 and indicated by FI-124.
It is preheated by the bottoms feed exchanger E-200
before entering the Feed Furnace (F-200).
TIC-200 controls the temperature of the feed entering
the VDU (T-200) by adjusting fuel gas flow to the
furnace.
LISTEN...LEARN...THINK...GROW 201
CONTROL OF VDU BOTTOM
PRODUCT QUALITY
Bottoms liquid is collected and sent to storage
through pump P-214 (HS-214), controlled by LIC-
214, and indicated by FI-224.
This residue's 95% point is monitored by AI-224.
Stripping steam is injected into the VDU bottoms by
FIC-234.
LISTEN...LEARN...THINK...GROW 202
CONTROL OF SLOP WAX
QUALITY
Hot slop wax is pumped from the tower by pump P-
213 (HS-213).
The slop wax product flow to storage (FI-223) is
controlled by LIC-213, and it's 95% point is
monitored by AI-123.
Cooled pump around is controlled by FIC-213 and
returned to the tower above the slop wax draw tray.
LISTEN...LEARN...THINK...GROW 203
CONTROL OF DISTILLATE
QUALITY Hot vacuum distillate is pumped from the tower by pump P-
212 (HS-212).
The vacuum distillate product flow to storage (FI-222) is controlled by LIC-212, and it's 95% point is monitored by AI-122.
Cooled pump around is controlled by FIC-212 and returned to the tower above the vacuum distillate draw tray.
Vacuum distillate reflux is controlled by FIC-232 and returned to the tower below the vacuum distillate draw tray.
LISTEN...LEARN...THINK...GROW 204
CONTROL OF VGO QUALITY Hot vacuum gas oil is pumped from the tower by pump P-
211 (HS-211).
The vacuum gas oil product flow to storage (FI-221) is controlled by LIC-211, and it's 95% point is monitored by AI-121.
Cooled pump around is controlled by FIC-211 and returned to the tower above the vacuum gas oil draw tray.
Vacuum gas oil reflux is controlled by FIC-231 and returned to the tower below the vacuum gas oil draw tray.
LISTEN...LEARN...THINK...GROW 205
CONTROL OF VDU
OVERHEAD
The VDU overhead vapor flows through the
overhead condenser E-210 (HV-212) into the
Overhead Vacuum Drum D-211.
The hydrocarbons are fully condensed and mixed
with the vacuum condensate flow from E-211.
LISTEN...LEARN...THINK...GROW 206
CONTROL OF VACUUM IN
VDU TOP
The VDU vacuum pressure is maintained by the
steam to the vacuum ejector (HV-211), the cooling
water (HV-212) to the steam condenser E-211, and
the hydrocarbon condenser E-210.
The pressure is regulated by PIC-210, which
reduces the vacuum by circulating water to the
vacuum ejector.
CHEMICAL
TRANSFORMATION OF
HYDROCARBONS
LISTEN...LEARN...THINK...GROW 207
LISTEN...LEARN...THINK...GROW 208
L.O #3 :Explain the process and
principles used for hydrotreating,
catalytic reforming, and
isomerization.
LISTEN...LEARN...THINK...GROW 209
OBJECTIVE OF THIS
SECTION
THE MAIN PURPOSE OF THIS
SECTION IS TO STUDY HOW A
REFINERY USE CHEMICAL
PROCESSES TO PRODUCE
GASOLINE FROM THE OTHER
FRACTIONS
LISTEN...LEARN...THINK...GROW 210
CHEMICAL TRANSFORMATION
FOR ADU PRODUCTS
LISTEN...LEARN...THINK...GROW 211
CHEMICAL TRANSFORMATION
FOR VDU PRODUCTS
LISTEN...LEARN...THINK...GROW 212
THREE WAYS OF CHEMICAL
TRANSFORMATION
You can change one fraction into
another by one of three methods:
breaking large hydrocarbons into
smaller pieces (cracking)
combining smaller pieces to make
larger ones (unification)
rearranging various pieces to make
desired hydrocarbons (alteration)
LISTEN...LEARN...THINK...GROW 213
THE NECESSITY OF THE
BREAKING PROCESSES
Very few of the components come out of
the fractional distillation columns ready
for market.
Many of them must be chemically
processed to make other fractions.
For example, only 40% of distilled crude
oil is gasoline; however, gasoline is one
of the major products made by oil
companies.
LISTEN...LEARN...THINK...GROW 214
BREAKING PROCESSES
TRANSFORM HEAVIER
FRACTIONS GASOLINE
Rather than continually distilling large
quantities of crude oil, oil companies
chemically process some other
HEAVIER fractions from the distillation
column to make gasoline
This processing increases the yield of
gasoline from each barrel of crude oil.
LISTEN...LEARN...THINK...GROW 215
CATALYTIC REFORMING
LISTEN...LEARN...THINK...GROW 216
WHAT IS CATALYTIC REFORMING
THE MAIN PROPERTY OF GASOLINE IS HIGH OCTANE NUMBER
LOW OCTANE NUMBER GASOLINE DESTROY THE CAR ENGINE
Catalytic reforming is an important process used to convert low-octane naphtha into high-octane gasoline blending components called reformates.
LISTEN...LEARN...THINK...GROW 217
FEED TREATMENT SECTION
BEFORE REFORMING
Naphtha from heavy and sour crude oils will contain some components like hydrogen sulfide, ammonia, organic nitrogen and sulfur compounds which will deactivate the Reforming catalyst
More or less standard is a feed preparation section in which, by combination of hydrotreatment and distillation, the feedstock is prepared to specification.
LISTEN...LEARN...THINK...GROW 218
HYDROTREATING OF SOUR
NAPHTHA
The hydrotreater uses Co/Mn Catalyst to convert organic sulfur and nitrogen compounds into H2S and NH3
These gases are removed with the unreacted Hydrogen
The metals in the feed are retained by the hydrotreater
The hydrogen needed come from the catalytic reformer
LEAN NAPHTHA ENTERS THE CATALYTIC REFORMING SECTION
LISTEN...LEARN...THINK...GROW 219
HYDROTREATING CHAPTER 9 FROM
BOOK
LISTEN...LEARN...THINK...GROW 220
THE OBJECTIVE OF
CATALYTIC REFORMING
Lean naphtha is used for the production of very high concentrations of toluene, benzene, xylene, and other aromatics needed in the final product : GASOLINE
The properties of the naphtha feedstock (as measured by the paraffin, olefin, naphthene, and aromatic content) will be changed using catalysts and appropriate operating conditions.
A significant by-product, is separated from the reformate ( gasoline) for recycling and use in other processes.
LISTEN...LEARN...THINK...GROW 221
PONA ANALYSIS BEFORE
AND AFTER REFORMING
Component NAPHTHA GASOLINE
* Paraffins 30-70 30-50
* Olefins 0-2 0
* Naphtenes 20-60 0-3
* Aromatics 7-20 45-60
LISTEN...LEARN...THINK...GROW 222
THE CATALYTIC
REFORMING PROCESS
LISTEN...LEARN...THINK...GROW 223
CATALYTIC REFORMING
PROCESS
catalytic reformer comprises a reactor section and a product-recovery section.
Naphtha feed and recycle hydrogen are mixed, heated and sent though successive reactor beds.
Each reactor needs heat input to drive the reactions
Final effluent is separated with the hydrogen being recycled or purged for hydrotreating
The reformate can be used as for gasoline blends or treated to separate aromatics components for petrochemical industries.
LISTEN...LEARN...THINK...GROW 224
CATALYST AND CONDITIONS
The catalyst
A typical catalyst is a mixture of
platinum and aluminum oxide.
With a platinum catalyst, the process is
sometimes described as "platforming".
Temperature and pressure
The temperature is about 500°C, and the
pressure varies either side of 20 atm.
LISTEN...LEARN...THINK...GROW 225
THE FOUR MAJOR REACTIONS
OF REFORMING
Dehydrogenation of naphtenes to
aromatics
Dehydrocyclization of paraffins to
aromatics
Isomerization
Hydrocraking
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Dehydrogenation of naphtenes to
aromatics
Methylcyclohexane Toluene + 3H2
Methylcyclopentane Cyclohexane
Benzene +3H2
N-heptane Toluene + 4H2
LISTEN...LEARN...THINK...GROW 227
Dehydrocyclization of paraffins
to aromatics
For example, cyclohexane, C6H14, loses
hydrogen and turns into benzene..
Heptane turns to methylbenzene or
toluene
LISTEN...LEARN...THINK...GROW 228
ISOMERIZATION OF
OLEFINS AND PARAFFINS
Paraffins are isomerized and to some
extent converted to naphtenes and
naphtenes are converted to aromatics
Olefins are saturated to form Paraffins
which then react as the first step
Naphtenes are converted to aromatics
Aromatics are essentially unchanged
LISTEN...LEARN...THINK...GROW 229
HYDROCRACKING
REACTIONS
Major hydrocracking reactions involve
the cracking and saturation of paraffins.
EXAMPLE: DECANE N-BUTANE
LISTEN...LEARN...THINK...GROW 230
MAIN REACTIONS IN THE
FIRST REACTOR BED :
Dehydrogenation &
Dehydrocyclization Reactions:
* highly endothermic
* The temperature decreases in the
reactor
* Highest reaction rates
LISTEN...LEARN...THINK...GROW 231
MAIN PROPERTY OF REACTOR
IS ITS SPACE VELOCITY (SV)
Space velocity represents the relation between volumetric flow and reactor volume.
It is often denoted by SV and it is related to the residence time in a chemical reactor, τ.
In the relationship, SV = 1/τ = volumetric flow/volume ( ex: m3/hr/m3)
The space velocity, in chemical reactor design, indicates how many reactor volumes of feed can be treated in a unit time.
For example, a reactor with a space velocity of 7 hr-1 is able to process feed equivalent to seven times the reactor volume each hour
LISTEN...LEARN...THINK...GROW 232
AROMATICS YIELDS IN FIRST
REACTOR INCREASED BY:
High temperature ( Increases rate of
reactions)
Low pressure ( Shift chemical reaction
to the production of aromatics)
Low space velocity ( promotes approach
at equilibrium)
Low hydrogen to Hydrocarbon ratio
LISTEN...LEARN...THINK...GROW 233
MAIN REACTIONS IN THE
SECOND REACTOR BED
Isomerization Reactions
Isomerization yield is increased by:
High temperature
Low space velocity
Low Pressure
Fairly rapid reactions
LISTEN...LEARN...THINK...GROW 234
MAIN REACTIONS IN THE
THIRD REACTOR BED
Hydrocracking Reactions
Exothermic reactions and produce lighter liquid and gas products
Relatively slow reactions
Major reactions are cracking and saturation of paraffins
Hydrocracking yields are increased by:
* High Temperature
* High Pressure
* Low space velocity
LISTEN...LEARN...THINK...GROW 235
Undesirable reactions In
reforming
Dealkylation of side chains on naphtenes
and aromatics to produce butane and
lighter paraffins
Cracking of paraffins and naphtenes to
form butane and lighter paraffins
LISTEN...LEARN...THINK...GROW 236
Catalytic Reforming Processes
Depending upon the frequency of catalyst
regeneration, Reforming Processes are
classified as:
continuous,
cyclic
semigenerative
LISTEN...LEARN...THINK...GROW 237
Continuous catalytic reforming
( figure 10.2 page 218)
Recently built reformers are continuous catalyst regeneration licensed by IFP and UOP
In this process, the catalyst flows by gravity from one reactor to another
the catalyst is then sent pneumatically to a regenerator and then sent to the first reactor
removal and replacement of catalyst during normal operation.
expensive process
the catalyst is always maintained at his highest activity.
LISTEN...LEARN...THINK...GROW 238
Semiregenerative catalytic
reforming
Regeneration of catalyst occurs when:
the octane number of the gasoline becomes low
when the temperature in the reactor is close to the maximum allowable
The unit should be shut down
high hydrogen recycle rates and high pressure are used to minimize coke deposit on the catalyst
Depending on the severity of the process , the regeneration takes place every 3 to 24 months
Low capital cost
LISTEN...LEARN...THINK...GROW 239
Cyclic catalytic reforming
It’s intermediate between the two
extremes
Only one reactor is shut and
regenerated when it is replaced by a
new reactor called a swing reactor
PRODUCT OF CATALYTIC
REFORMING: GASOLINE
THE MAIN PRODUCT OF ANY
REFINERY
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LISTEN...LEARN...THINK...GROW 241
Motor gasoline is a blend of
* Light straight line
* Catalytic Reformate
* Catalytically cracked gasoline
* Hydrocracked gasoline
* Polymer gasoline
* Additives
LISTEN...LEARN...THINK...GROW 242
WHAT IS GASOLINE?
Source of energy for motors
Complex mixture of hydrocarbons with a boiling point range:100-400oF (38-205oC) by ASTM method
Grades of Gasoline: Unleaded, Regular, Premium and superpremium
CHEMICAL TANSFORMATION OF
DIFFERENT HYDROCARBONS
MAKE MORE GASOLINE FROM THE
SAME CRUDE OIL FEED RATE
LISTEN...LEARN...THINK...GROW 244
THREE WAYS OF CHEMICAL
TRANSFORMATION
You can change one fraction into another
by one of three methods:
Rearranging various pieces to make
desired hydrocarbons (alteration)
Combining smaller pieces to make
larger ones (unification)
Breaking large hydrocarbons into
smaller pieces (cracking)
REARANGING THE
MOLECULAR STRUCTURE
We have studied this transformation in
the Catalytic Reforming Process where
paraffins, olefins and naphtenes were
transformed into is-paraffins or aromatics
which have highest octane number
Combining smaller pieces to make
larger ones
This transformation will be studied in this
chapter where small molecules
Alkylation Process
Isomerization process
ALKYLATION PROCESS
DEFINITION
In petroleum terminology, the term
Alkylation is used for the reaction of low
molecular weight olefins with an iso-
paraffin to form higher molecular weigh
iso -paraffin
STUDY THE ALKYLATION REACTIONS
PAGE 232 AND 233
THE ALKYLATION PROCESS
FEED:
Alkylation combines low-molecular-weight olefins (primarily a mixture of propylene and butylenes) with isobutene.
CATALYST:
Either sulfuric acid or hydrofluoric acid.
PRODUCT:
The product is called alkylate and is composed of a mixture of high-octane, branched-chain paraffinic hydrocarbons.
PRODUCT SPECIFICATIONS:
Alkylate is a premium blending stock because it has exceptional antiknock properties and is clean burning. The octane number of the alkylate depends mainly upon the kind of olefins used and upon operating conditions.
TYPICAL FEEDSTOCKS FOR
ALKYLATION PROCESS
Petroleum gas from Distillation or
cracking units
Olefins from Catalytic cracking or
hydrocracking units
Sulfuric Acid Alkylation
Process
FEED:
In cascade type sulfuric acid (H2SO4) alkylation units, the feedstock (propylene, butylene, amylene, and fresh isobutane) enters the reactor
CATALYST
the concentrated sulfuric acid catalyst (in concentrations of 85% to 95% for good operation and to minimize corrosion).
THE REACTOR
The reactor is divided into zones, with olefins fed through distributors to each zone, and the sulfuric acid and isobutanes flowing over baffles from zone to zone.
The reactor effluent is separated into hydrocarbon and acid phases in a settler, and the acid is returned to the reactor. The hydrocarbon phase is hot-water washed with caustic for pH control before being successively depropanized, deisobutanized, and debutanized.
THE PRODUCT
The alkylate obtained from the deisobutanizer can then go directly to motor-fuel blending or be rerun to produce aviation-grade blending stock. The isobutane is recycled to the feed.
SCHEMA OF THE PROCESS
PROCESS VARIABLES
REACTION TEMPERATURE
ACIDITY
ISOBUTANE CONCENTRATION
OLEFIN SPACE VELOCITY
REACTON TEMPERATURE
Normal temperatures are from 5 to 100C
Lower temperatures will increase
significantly the acid solution viscosity
Bad mixing and separation of products
Higher temperatures ( >200C)
Polymerization of olefins
ACIDITY OF SOLUTION
Highest Octane number and highest
yields are obtained at:
93-95% weight acid
1-2% water
Hydrocarbons diluents
Higher concentration of water will lower
the activity of the catalytic solution
ISOBUTANE
CONCENTRATION
Higher isobutane/olefin ratio will increase
the octane number and the yield of the
alkylate
In industrial practice the ration from 5:1
to 15:1 is used
Reactors using internal circulation use
up to 100:a to 1000:1 ratio
OLEFIN SPACE VELOCITY
Lowering the olefin space velocity or
increasing the contact time, it will:
Reduce the production of high boiling
points hydrocarbons
Increase the alkylate octane number
Contact time varies from 5 to 25 min
CORRELATON FACTOR Mrstik et al. developp a correlation factor
IE= % OF ISOBUTANE VOLUME IN REACTOR
(I/O)F= VOLUMETRIC ISOBUTANE/OLEFIN RATIO IN FEED
(SV)0= OLEFIN SPACE VELOCITY (hr-1)
NORMAL VALUES OF F : 10 TO 40
HIGHER VALUES GIVE HIGHER ALKYLATE OCTANE NUMBER
0).(100
)/.(
SV
OIIF FE
SAFETY PRECAUTIONS:
HAZARDOUS SULFURIC ACID
Loss of coolant water, which is needed to maintain process temperatures, could result in an upset.
Precautions are necessary to ensure that equipment and materials that have been in contact with acid are handled carefully and are thoroughly cleaned before they leave the process area or refinery.
..
Immersion wash vats are often provided
for neutralization of equipment that has
come into contact with hydrofluoric acid.
Hydrofluoric acid units should be
thoroughly drained and chemically
cleaned prior to turnarounds and entry to
remove all traces of iron fluoride and
hydro-fluoric acid
SAFETY PRECAUTIONS:
HAZARDUS SULFURIC ACID
Following shutdown, where water has been used the unit should be thoroughly dried before hydrofluoric acid is introduced
Leaks, spills, or releases involving hydrofluoric acid or hydrocarbons containing hydrofluoric acid can be extremely hazardous.
Care during delivery and unloading of acid is essential.
Process unit containment by curbs, drainage, and isolation so that effluent can be neutralized before release to the sewer system is considered.
Vents can be routed to soda-ash scrubbers to neutralize hydrogen fluoride gas or hydrofluoric acid vapors before release.
Pressure on the cooling water and steam side of exchangers should be kept below the minimum pressure on the acid service side to prevent water contamination.
CORROSION PROBLEMS
Some corrosion and fouling in sulfuric acid units may occur from the breakdown of sulfuric acid esters or where caustic is added for neutralization.
These esters can be removed by fresh acid treating and hot-water washing.
To prevent corrosion from hydrofluoric acid, the acid concentration inside the process unit should be maintained above 65% and moisture below 4%.
NEW UOP ALKYLATION
PROCESS
UOP has developed a new approach to produce a gasoline blending component similar in quality to traditional motor alkylate.
The InAlk process uses commercial, solid catalysts for reacting light olefins to produce a high octane, paraffinic gasoline component similar to traditional alkylate.
The InAlk process is based on proven technology and light hydrocarbon chemistry.
The Alkylene process is a novel solid-catalyst alkylation process with a product equal to that produced by liquid HF alkylation.
LISTEN...LEARN...THINK...GROW 265
ISOMERIZATION PROCESS
PROCESS OBJECTIVE
ABU DHABI REFINERY : LIGHT NAPHTA AND
HEAVY NAPHTA ARE SEPARATED AND :
LIGHT NAPHTA TO ISOMERIZATION
HEAVY NAPHTA TO CATALYTIC
REFORMING
CONVERT LOW OCTANE N-PARAFFINS OF
LIGHT NAPHTA ( C4–1800F and RON ~70) TO
HIGH OCTANE ISO PARAFFINS ( RON~92) IF
RECYCLING IS USED
PROCESS TECHNIQUE
Isomerization occurs in a chloride
promoted fixed bed reactor where n-
paraffins are converted into iso-paraffins
Catalyst very sensitive to incoming
contaminants ( water and sulfur)
PROCESS STEPS
Desulfurized feed and hydrogen are dried in fixed beds of solid desiccants prior to mixing together
The mixed feed is heated and passes through a hydrogenation reactor to saturate olefins to paraffins and saturate benzene
The hydrogenation effluent is cooled and passes through a isomerization reactor
The final effluent is cooled and separated as hydrogen and LPG which go as fuel gases and isomerate product to gasoline blend.
FIGURE 10.9 PAGE 225
PROCESS VARIABLES
The yield of the process is increased by:
High temperature ( reaction rate ↑)
Low space velocity ( reaction time ↑)
Low pressure
High H2/HC Phc ↓ isomers yield ↑
GASOLINE BY CRACKING
LONG CHAIN HYDROCARBONS
CRACKING CATALYTIC
HYDROCRACKING
THERMAL CRACKING
LISTEN...LEARN...THINK...GROW 272
CRACKING UNIT
LISTEN...LEARN...THINK...GROW 273
Catalytic cracking?
The most important and widely used refinery
process
Convert heavy oils into valuable gasoline and
lighter products
Originally cracking was accomplished thermally
Catalytic cracking produces more gasoline with
higher octane number
Comparison between thermal and catalytic
cracking is shown in Table 6.1 page 122
LISTEN...LEARN...THINK...GROW 274
PRIMARY CRACKING
REACTIONS
The primary reactions can be
represented as follow:
PARAFFIN paraffin + olefin
ALKYL NAPHTENE naphtene + olefin
ALKYL AROMATIC aromatic + olefin
LISTEN...LEARN...THINK...GROW 275
HEAT OF CRACKING
REACTIONS (REACTOR)
The cracking reaction is endothermic or
exothermic?
ENDOTHERMIC
WHY?
Because we need energy to get
small molecules from big molecules
LISTEN...LEARN...THINK...GROW 276
HEAT OF REGENERATION
(REGENERATOR)
The regeneration reaction is
endothermic or exothermic?
Exothermic
Why ?
Because burning coke is an
oxidation and oxidation release heat
LISTEN...LEARN...THINK...GROW 277
Temperatures of reactor and
regenerator
Reactor temperature are around 900 to
10000F ( 480-5400C)
The feed temperature is around 500 to
9000F ( 260-4250C)
regeneration exit temperature is around
1200 to 15000F ( 650-8150C)
LISTEN...LEARN...THINK...GROW 278
Different types of processes
Two Classes:
Moving bed
Fluidized bed
These days, there are very few
Moving bed reactors
FLUIDIZED BED?
In a Fluidized Bed Reactor, the catalyst
is distributed in the fluid phase and
behaves as a fluid.
CATALYST STAYS INSIDE THE
REACTOR
LISTEN...LEARN...THINK...GROW 280
Fluid catalytic cracker
The fluid catalytic cracker (FCC) is
representative of the fluidized bed units
The FCC can be classified as :
Bed FCC
Riser FCC
Depending where the major fraction of the
cracking reactions occur
LISTEN...LEARN...THINK...GROW 281
THE REACTOR AND
REGENERATOR
REACTOR
REGENERATOR
LISTEN...LEARN...THINK...GROW 282
PROCESS DESCRIPTION FOR
RISER FCC:
A) FEED AND RISER:
Pre-heated feed is sprayed into the base of the riser via feed nozzles where it contacts extremely hot fluidized catalyst at 1230 to 1400 degrees F
The hot catalyst vaporizes the feed and catalyzes the cracking reactions that break down the high molecular weight oil into lighter components including LPG, gasoline, and diesel
LISTEN...LEARN...THINK...GROW 283
PROCESS DESCRIPTION:
B) REACTOR AND CYCLONES:
The catalyst-hydrocarbon mixture flows upward
through the riser for just 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, light cycle oils used in diesel
and jet fuel, and heavy fuel oil.
LISTEN...LEARN...THINK...GROW 284
PROCESS DESCRIPTION:
C) STRIPPER: During the trip up the riser, the cracking catalyst is "spent" by reactions which deposit coke on the catalyst and greatly reduce activity and selectivity.
The "spent" catalyst is disengaged from the cracked hydrocarbon vapors and sent to a stripper where it is contacted with steam to remove hydrocarbons remaining in the catalyst pores
LISTEN...LEARN...THINK...GROW 285
PROCESS DESCRIPTION:
D) REGENERATOR:
The "spent" catalyst then flows into a fluidized-
bed regenerator where air (or in some cases air
plus oxygen) 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
Figures 6.1 a and 6.1 b
LISTEN...LEARN...THINK...GROW 286
CATALYST IN FCC
The FCC uses very fine particles catalyst
( 70μm) which behave as a fluid when
aerated with vapor
The fluidized catalyst is circulated
continuously between the reactor and
the regenerator
LISTEN...LEARN...THINK...GROW 287
TYPES O CATALYST
Commercial cracking catalyst can be
divide into 3 classes:
1) acid treated natural aluminosilicates
2) amorphous synthetic silica-alumina
mixtures
3) crystalline synthetic silica-alumina
catalysts called zeolites
LISTEN...LEARN...THINK...GROW 288
INDUSTRIALY USED
CATALYSTS
The most commonly used are classes 2
and 3 Tables 6.2 and 6.3 PAGE 137
LISTEN...LEARN...THINK...GROW 289
Advantages of zeolites catalyst
Higher activity
Higher gasoline yield
Lower coke yield
LISTEN...LEARN...THINK...GROW 290
CRACKING MAIN PROBLEM:
COKING
The cracking process produces carbon which
remains on the catalyst and lowers its activity
What should we do to maintain the activity of
catalyst high?
Regenerate the catalyst by burning off the
coke with air
As a result, the catalyst is continuously
moved from reactor to regenerator
( Figure 6.1a page 95)
LISTEN...LEARN...THINK...GROW 291
Catalytic hydrocracking?
A process similar to catalytic cracking in
its industrial purpose but effected under
hydrogen pressure.
The catalyst of hydrocracking containing
two functions:
A cracking function
A hydrogenating function ( Figure 7.2
page 144 shows a two-stages system).
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Hydrocracking Catalyst
Most of the hydrocracking catalyst
consist of a crystalline mixture of silica
alumina with a small uniformly
distributed amount of rare earths
containing within the crystal line lattice.
The silica-alumina provides cracking
Rare earth component provides
hydrogenation
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Hydrocracking and catalytic
cracking
They work as a team:
The catalytic cracker takes the more easily
cracked paraffinic atmospheric and vacuum
gas oils as charge stocks
The hydrocraking uses more aromatic
cycle oils and cooker distillates as feed.
These streams resist to catalytic cracking but
high pressure and hydrogen atmosphere make
them easy to crack
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Why catalytic hydrocracking?
NEW DEMAND: The demand for petroleum products has shifted to high ratio of gasoline and jet fuel compared with the usage of diesel fuel and home heating fuels.
DISPONIBILTY OF HYDROGEN: by product hydrogen at low cost and in large amounts has become available from catalytic reforming operations
ENVIRONMENTAL CONCERNS: limiting sulfur and aromatic compounds concentrations in motor fuels have increased
PRETREATMENT OF HEAVY
DISTILLATE FRACTIONS
REMOVING IMPURITIES TO AVOID
CATALYST POISENING AND
ENVIRONMENTAL PROBLEMS
CATALYTIC PROCESS MAIN
PROBLEMS
Catalysts of Reforming catalytic &
Cracking catalytic & Hydrocracking
can be poisoned by sulfur , nitrogen
and oxygen compounds and
metallic salts present in the their
respective feedstocks
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FEEDSTOCKS PREPARATION
Feed impurities are removed by a hydrotreatment process to:
Saturate the olefins
Remove sulfur, nitrogen and oxygen compounds.
Molecules containing metals are cracked and the metals are retained by the catalyst
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HYDROTREATING
OBJECTIVE:
Hydrotreating is used for removing the
undesired compounds and stabilizing
the heavy distillate fractions.
Hydrotreating uses:
A catalyst
A substantial quantities of hydrogen.
ENVIRONMENTAL ISSUES
The main impurities that could also harm the environment are nitrogen and sulfur compounds.
They are removed by conversion of sulfur and nitrogen elements into ammonia and hydrogen sulfide.
Because of the new environmental regulations due to global warming, the amount of sulfur and nitrogen in the refinery products are around 50 ppm and less
MAIN HYDROTREATING
PROCESSES
The most used Hydrotreating
processes are:
Desulphurization (remove sulphur
compounds)
Denitrification (remove nitrogen
compounds)
Conversion of olefins to paraffins
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HDS MAIN REACTIONS
Mercaptans: RSH + H2 RH + H2S
Sulfides : R2S + 2H2 2RH + H2S
Disulfides : (RS)2 + 3H2 2RH + 2H2S
Thiophenes :
+4H2 C4H10 + H2S
S
The reactions: EXOTHERMIC
HDS CATALYST
The most economical catalyst for HDS
is: Cobalt- Molybdene oxides on alumina
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THE OTHER REACTIONS OF
THE HDS PROCESS
In the HDS reactor, other reactions take place like:
Denitrogenation
Deoxidation
Dehalogenation
Hydrogenation
Hydrocracking.
DENITROGENATION
Nitrogen is more difficult to remove than sulfur
Reactions :
Pyrrole: C4H4NH + 4H2 C4H10 + NH3
Pyridine: C5H5N + 5H2 C5H10 + NH3
For middle distillate fractions having high concentration of nitrogen, the catalyst used is : 90% Ni- Mo oxides and 10% nickel-tungsten
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Operating Conditions
Temperature 270- 3400C
Pressure 690- 20,700 kPag
Hydrogen/ unit feed:
Recycling 360m3/m3
Consumption 36-142m3/m3
Space velocity 1.5 -8.0
Space velocity is defined as the rate of feed
per unit mass of catalyst ( mass of catalyst
because catalyst is very expensive)
CLASS WORK #1
Study the process of HDS figure 9-1
page 196
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CLASS WORK #2:
study figure 9-2 page 199
Discuss the effects of process variables on its
efficiency:
T ↑ Removal ↑ , H2 Consumption
↑and coke ↑
PH2 ↑ Removal ↑ and H2 Consumption
↑
P ↑ H2 Consumption ↑ and Coke ↓
Space velocity ↑ Removal ↓ and H2
Consumption ↓ and Coke ↓
ACID GAS REMOVAL
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ACID GAS REMOVAL
Gases from various operations of sour
crude oil contain hydrogen sulfide
The hydrogen sulfide is produced in
units such as hydrotreating, cracking and
coking
Recent air pollution regulations require
that most of the sulfur to be removed
from gases and converted to element
sulfur
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THREE DIFFERENT KINDS OF
PROCESSES TO REMOVE H2S
Chemical solvent processes
Physical solvent processes
Dry adsorbents processes
Chemical solvent processes
: FIGURE 13.5
* Monoethanolamine (MEA)
* Diethanolamine (DEA)
* Methyl- Diethanolamine (MDEA)
* Diglycolamine (DGA)
* Hot Potassium Carbonate
Physical solvent processes
Physical solvent processes:
* Selexol
* Propylene Carbonate
* Sulfinol
* Rectisol
Dry adsorbents processes:
* Molecular sieve
* Activated charcoal
* Iron sponge
* Zinc oxide
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Class work #3
Discuss the figure 13.5
page 284 and explain all
the steps of the process
SULFUR RECOVERY PROCESS
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THE MODIFIED CLAUSS PROCESS:
The most practical method for converting
hydrogen sulfide to elementary sulfur
Best suited for gases containing more
than 50% hydrogen sulfide is the
PARTIAL COMBUSTION PROCESS.
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PARTIAL COMBUSTION
PROCESS (FIGURE 13.7 PAGE
287)
Hydrogen sulfide is burned with 1/3 the
stoichiometric quantity of air
2H2S + 3O2 2H2O + 2SO2
The hot gases are sent to a reactor with
alumina as catalyst to react sulfur
dioxide with unburned hydrogen sulfide
to produce free sulfur
2H2S + SO2 2H2O + 3S
TAIL GASES OF CLAUS
PLANT
Carbon sulfide (COS) and carbon disulfide CS2
have presented problems in many Claus plant
operations.
These compounds are formed in the
combustion step ( see reactions page 289)
Unconverted, these compounds represent a
loss of sulfur recovery.
They are in the tail gas of the Claus process
and sent to the Scot process
CLASS WORK #4
USING THE BOOK, DESCRIBE ALL
THE STEPS OF THE CLAUSS
PROCESS IN FIGURE 13.7 PAGE 287
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PROCESS FLOW DIAGRAM
THE SCOT PROCESS
THE TAIL GAS OF THE CLAUS
PROCESS ARE SENT TO THE SCOT
PROCESS
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DESCRIPTION OF THE SCOT
PROCESS ( fig 13.9 page 291)
The tail gas of the Claus unit contains small amounts of CARBONYL SULFIDE and CARBON DISULFIDE as well as SO2 and H2S
The gas is combined with hydrogen or a mixture of ( CO + H2)
The mixture is heated at 480 to 5700F,
Pass through a catalytic reactor where sulfur compounds are converted to Hydrogen sulfide
The reactor effluent is cooled and H2S is absorbed with amine solution
The H2S from the amine generation unit is sent back to the Claus process
The H2S exiting the amine unit ( 50 to 400 ppm) is burned to produce SO2
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Class work: study the process
in figure 13.9 page 291
LUBRICATING OILS
INTRODUCTION
The lube oil sold in the market are a
mixture of:
Lubricating oil base stocks
Additives
Lubricating oils
The feeds for the production of
lubricating oils come from the vacuum
distillation
The feeds are treated to improve the
quality of the lubricating oils
Chemicals are added to improve the
properties
USES OF LUBRICATING
OILS
Motor oil is a lubricant in internal combustion engines, typically found in automobiles and other vehicles, boats, lawn mowers, trains, airplanes.
In engines there are parts which move very closely against each other at high speeds, often for prolonged periods of time.
Such motion causes friction, absorbing otherwise useful power produced by the motor and converting the energy to useless heat.
Friction also wears away the contacting surfaces of those parts, which could lead to lower efficiency and degradation of the motor.
This increases fuel consumption.
USES OF LUBRICATING
OILS
Lubricating oil makes a film between surfaces
of parts moving next to each other so as to
minimize direct contact between them
decreasing friction, wear, and production of
excessive heat, thus protecting the engine.
Motor oil also carries away heat from moving
parts, which is important because materials
tend to become softer and less abrasion-
resistant at high temperatures.
Some engines have an additional oil cooler.
MOST IMPORTANT
PROPERTY OF MOTOR OILS
One of the most important properties of motor oil in maintaining a lubricating film between moving parts is its viscosity
The viscosity must be high enough to maintain a satisfactory lubricating film, but low enough that the oil can flow around the engine parts satisfactorily to keep them well coated under all conditions.
VISCOSITY INDEX
The viscosity index is a measure of how
much the oil's viscosity changes as
temperature changes.
A higher viscosity index indicates the
viscosity changes less with temperature
than a lower viscosity index
POUR POINT OF MOTOR
OILS
Motor oil must be able to flow at cold winter
temperatures to lubricate internal moving parts
upon starting up the engine.
Another important property of motor oil is its
pour point, which is indicative of the lowest
temperature at which the oil could still be
poured satisfactorily.
The lower the pour point temperature of the
oil, the more desirable the oil is when starting
up at cold temperature.
FLASH POINT OF MOTOR
OILS
Oil is largely composed of hydrocarbons which can burn if ignited.
Still another important property of motor oil is its flash point, the lowest temperature at which the oil gives off vapors which can ignite.
It is dangerous for the oil in a motor to ignite and burn, so a high flash point is desirable.
At a petroleum refinery, fractional distillationseparates a motor oil fraction from other crude oil fractions, removing the volatile components which ignite more easily, and therefore increasing the oil's flash point.
TOTAL BASE/ACID NUMBER
Another test done on oil is to determine the
Total Base Number (TBN), which is a
measurement of the reserve alkalinity of an oil
to neutralize acids.
The resulting quantity is determined as mg
KOH/(gram of lubricant).
Analogously, Total Acid Number (TAN) is the
measure of a lubricant's acidity.
Other tests include zinc, phosphorus, or sulfur
content, and testing for excessive foaming.
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LUBRICATING OIL
BLENDING STOCKS
The main properties of lubricating oils are:
* Viscosity
* Viscosity Index
* Pour Point
* Oxidation Resistance
* Flash Point
* Boiling Temperature
* Acidity
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VISCOSITY
From a given crude oil; the higher the boiling point; the greater is the viscosity
The viscosity of a lubricating oil can be selected by the distillation boiling point of the cut
Measure of internal resistance to flow
The higher is the viscosity the ticker the film of oil that clings to a surface
Depending upon the service:
* The oil should be thin and free flowing
* Or should be tick and resistant to flow
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VISCOSITY INDEX (VI)
The rate of change of viscosity with temperature
The higher is the VI, the smaller is the change of viscosity with temperature
The VI of lubricating oils vary from negative values for oils from naphtenic crude oils to about 100 for oil from parrafinic crude oils.
Some specially processed oils with chemical additives can have VI higher than 130
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ADDITIVES TO IMPROVE VI
Polyisobutylenes or polymethacrylic acid esters
are used to improve the VI of lubricating oils
Motor oils must be thin enough at low
temperatures to permit easy starting
Viscous enough at engine operating
temperatures ( 80-1200C) to reduce friction by
providing enough oil thickness between metal
surfaces
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POUR POINT
The lowest temperature at which oil will
flow under standards conditions
A Low pour point is important in cold
days to obtain easy starting of the
engine
They are two types of pour point:
* Viscosity pour point
* Wax pour point
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Viscosity pour point
The Viscosity pour point is approached
gradually as the temperature is lowered
and the viscosity of the fluid increase
until it will not flow under the standards
conditions
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Wax pour point
The wax pour point occurs abruptly as
the paraffin wax crystals precipitate from
oil and the solution solidifies
Additives can be used to lower the wax
pour point
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Cloud point
The cloud point is also used to report
the temperature at which wax or other
solid material begins to separate from
solution
For parrafinic oils, this is the starting
point of crystallization of parrafinic waxes
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Oxidation resistance
The high temperature of engines causes the rapid oxidation of motor oils
Especially in piston heads where temperature can attain 4000C.
Oxidation causes the formation of coke
Anti oxidation additives, such as phenolic compounds , can be added to suppress oxidation
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Flash point
It is only an indication of the
hydrocarbons emissions
Low flash point indicate greater
hydrocarbon emissions during use
It also indicate if a mixture of high
viscosity and low viscosity cuts or is a
central cut with average viscosity
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Boiling temperature
The higher is the boiling temperature means
the higher is the molecular weights of the
components and the greater is the viscosity
The boiling ranges and the viscosities of the
fractions are the major factors in selecting the
cut points for the lube oil blending stocks on the
vacuum distillation unit.
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Acidity
The organic acids formed during the oxidation of lubricating oil causes corrosion because of their acidity
The alkaline materials are added to lubricating to neutralize the acid contaminants.
Lube oils blending from parrafinic crude oils have higher oxidation stability and exhibit lower acidity than the naphtenic crude oils
LUBE OIL PROCESSINGS
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LUBE OIL PROCESSING
The objective of lube oil processing is to improve the properties of raw lube oil fractions from most crude oils which contain components which have undesirable characteristics for finished lubricating oils
The heavier lube oil raw stocks are included in the vacuum fractionating tower bottoms with asphaltenes, resins, and other undesirables materials
The choice of the cut for lube
oils
The first step is the separation on the
crude oil distillation units of the individual
fractions according to viscosity and
therefore by boiling range
specifications
Heavy lube oils are produced by heavy
hydrocarbons who have high boiling
points
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PROPERTIES TO BE
IMPROVED
The undesirable characteristics of these impurities include:
High Pour Point
High Cloud Point
Low VI ( large change of viscosity with Temperature)
Poor oxygen stability
Poor Color
High Organic acidity
High carbon and sludge-forming tendencies
CLASS WORK #1
STUDY AND DISCUSS WITH YOUR
FRIENDS THE MAIN PROPERTIES OF
LUBE OILS IN PAGE 309.
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The processes used to change
these characteristics are:
Solvent deasphalting to reduce carbon and
sludge- forming tendencies
Solvent extraction and hydrocracking to
improve VI
Solvent dewaxing and selective hydrocracking
to lower cloud and pour point
Hydrotreating and clay treating to improve
color and oxygen stability and lower organic
acidity
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PROPANE DEASPHALTING
The lighter distillate feedstocks for
producing lubricating oil base stocks can
be sent directly to the solvent extraction
unit, however the atmospheric and
vacuum still bottoms require de-
asphalting to remove the asphaltenes
and the resins before solvent extraction
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QUALITIES OF PROPANE
Propane is usually used but can sometimes be mixed with ethane or butane in order to obtain desired solvent properties
Propane has unusual solvent properties:
From 40 to 600C, the paraffins are very soluble in propane but this solubility when the temperature increases until the critical temperature of propane ( 96.80C)
The asphaltens and resins are largely insoluble in propane
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The Process
The feed is mixed with 4 to 8 volumes of liquid
propane at the desired temperature
The extract phase contains from 15 to 20% by
weight of oil with the remaining solvent
The heavier is the feed , the higher propane to
feed ratio
The raffinate phase contains 30 to 50%
propane by volume and is an emulsion of
precipitated asphaltic materials with propane
CLASS WORK :
STUDY AND DISCUSS WITH YOUR
FRIENDS FIGURE 15.1 PAGE 313
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Viscosity Index improvement
and solvent extraction
Three solvent used for the extraction of aromatics from lube oil feeds:
Furfural
Phenol
N-methyl-2-pyrrolidone ( NMP)
The purpose of solvent extraction is to improve VI, oxidation resistance and color of the lube oil and to reduce the carbon and sledges- forming tendencies of the lubrificants by separating the aromatic portion from the naphtenic and parrafinic portions of the feed
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Furfural Extraction
Similar to the propane deasphalting unit
Except: The solvent recovery which is more complicated
The extraction column is a rasching –ring packed column or sometimes a rotating disc column RDC
The temperature gradient in the column is 300C to 500C between the top and the bottom
The temperature of the top depends on the miscibility temperature of furfural and oil Usually from 1050C to 1500C
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VI OF LUBE OILS IMPROVED BY
HYDROCRACKING OF GAS
OILS Table 15.1 ( page 317) shows that the VI of
mononaphtene and paraffins are high
Hydrocracking of vacuum gas oils increase the concentration of parrafins and the VI of the lube oil
When the severity of the process increases mononaphtalenes and isoparaffins increases
The good conditions of the process are :
* High conversion
* Low space velocity
* Low reaction temperature
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DEWAXING
All lube oils , except those from very few naphtenic crude oils, must be dewaxed
Dewaxing is the most important process otherwise the lube oils will not flow at ambient temperatures
Two types of processes: Refrigeration to crystallize the wax and
solvent to dilute the oil fraction sufficiently to permit rapid filtration
Selective hydrocracking to crack wax molecules into light hydrocarbons
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SOLVENT DEWAXING
Two principal solvents: Propane and
ketones
The ketone process uses :
* Methyl Ethyl Ketone (MEK) with
Methyl isobutyl ketone ( MIBK)
* MEK with Toluene
CLASS WORK #3
STUDY THE DEWAXING BY PROPANE
PAGE 319-320
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DILCHILL DEWAXING
( Figure 15.3 PAGE 320)
Developed by EXXON
Describe Process in Figure
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GRADES OF MOTOR OILS
SINGLE GRADE
MULTI GRADE
SINGLE GRADE
The Society of Automotive Engineers, usually abbreviated as SAE, has established a numerical code system for grading motor oils according to their kinematic viscosity.
For single-grade oils, the kinematic viscosity is measured at a reference temperature of 100 °C (212 °F) in units of mm²/s or the equivalent older non-SI units, centistokes (abbreviated cSt).
SINGLE SAE GRADE
The higher the viscosity, the higher the
SAE grade number is.
These numbers are often referred to as
the weight of a motor oil.
Based on the range of viscosity the oil
falls in at that temperature, the oil is
graded as an SAE number 0, 5, 10, 20,
30, 40, 50, 60 or 70.
SINGLE GRADES IN WINTER
(W)
On single-grade oils, viscosity testing can be
done at cold, winter (W) temperature (as well
as checking minimum viscosity at 100 °C or 212
°F) to grade an oil as SAE number 0W, 5W,
10W, 15W, 20W, or 25W
A single-grade oil graded at the hot temperature
is expected to test into the corresponding grade
at the winter temperature; i.e. a 10 grade oil
should correspond to a 10W oil.
MOTOR OILS WITH
ADDITIVES
A specific oil will have high viscosity when cold and a low viscosity at the engine's operating temperature.
The difference in viscosities for any single-grade oil is too large between the extremes of temperature.
To bring the difference in viscosities closer together, special polymer additives called viscosity index improvers are added to the oil.
These additives make the oil a multi-grade motor oil.
WHY MULTIGRADE LUBE
OILS
The idea is to cause the multi-grade oil to have
the viscosity of the base number when cold and
the viscosity of second number when hot.
The viscosity of a multi-grade oil still varies
logarithmically with temperature, but the slope
representing the change is lessened.
This slope representing the change with
temperature depends on the nature and amount
of the additives to the base oil.
API/SAE SCALE FOR
MLTIGRADE LUBE OILS
The API/SAE designation for multi-grade oils includes two grade numbers.
For example, 20W-50 designates a common multi-grade oil in UAE.
Historically, the first number associated with the W (again 'W' is for Winter, not Weight) is not rated at any single temperature.
The “20W" means that this oil can be pumped by your engine as well as a single-grade SAE 20 oil can be pumped.
The second number, 50, means that the viscosity of this multi-grade oil at 100 °C (212 °F) operating temperature corresponds to the viscosity of a single-grade 50 oil at same temperature
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Hydrogen production &
purification
Many refineries produce enough hydrogen for hydrotreating from the catalytic reforming unit.
Some modern plants with extensive hydrotreating and hydrocracking operations require more hydrogen than they produce
This hydrogen can be produced:
-- By partial oxidation of heavy hydrocarbons such as fuels
-- By steam reforming of methane( natural gas) , ethane or propane ( FIGURE 13.1)
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Steam Reforming of natural gas in
four stepsSTEP ONE: REFORMER :
CH4 + H2O CO + 3H2
Catalytic reaction
temperature range : 1400-15000F
Endothermic reaction
gas pass through a filled catalyst furnace
Catalyst: hallow cylindrical rings of ¾ in in diameter . 25 to 40% nickel oxide deposited on silica refractory base.
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STEP 2 :SHIFT CONVERTER
In the shift converter, more steam is added to convert the CO produced by the REFORMER to an equivalent amount of hydrogen.
SHIFT CONVERTER: CO + H2O CO2 + H2
The shift reaction is:
* Exothermic reaction
* In fixed bed catalytic reactor
* Temperature: 6500F
* Catalyst : Mixture of chromium and iron
oxide
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STEP 3 : GAS PURIFICATION
The third step is the removal of CO2 in
circulating amine or hot potassium
carbonate solution. CO2 being acid is
absorbed by a basic solution like amine
Absorption column with 24 trays
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STEP 4 : METHANATION
in this last step of steam reforming, the
remaining quantities of CO and CO2 are
converted to methane :
* Exothermic Reactions:
CO + 3H2 CH4 + H2O
CO2 + 4H2 CH4 + 2H2O
* Fixed bed catalytic reactor
* Temperature range : 700-8000F
* Catalyst : 10 to 20% Ni on a refractory base
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Future Trends in Petroleum
Refining There are four major forces which affect the development of petroleum refining processes:
Demand for products (i.e. gasoline or diesel, fuel oil or jet fuel ) to be cleaner and higher-performance
Feedstock supply increasing heavier and more sour crude supply — alternative feed supplies include oil sand, and coal.
Environmental regulations
Technology development (i.e. new catalysts and processes) — the development of fuel cells would drive refineries to become H2 producers
Current Government Regulations on sulfur content in diesel fuel US EPA has reduced from 5000 ppm to 500 ppm in 1993
EEC has limited to 500 ppm since 1996,
Japan has limited to 500 ppm since 1997,
Canada has limited to 500 ppm since 1998.
New US EPA Tier 2 Regualtions on sulfur content in diesel and gasoline
Most refiners must meet a 30 ppm sulfur average with a 80 ppm cap for both conventional and reformulated gasoline by January 1, 2006
New on-road diesel regulations = 15 ppm sulfur cap by January 1, 2006
New Processes for Low-Sulfur Fuels
More active and selective catalysts for existing HDS processes
Novel processing schemes that don’t depend on HDS technology
· Reactive adsorption of sulfur without high-pressure H2 (Phillips Petroleum)
Selective adsorption of sulfur compounds without H2 (PSU)
Liquid-phase oxidation followed by extraction
Bio-desulfurization that is not limited by steric restriction of 4,6-DMBT (Energy Biosystems)
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GAS PROCESSING UNIT
Main objectives:
Recovery of valuable C3,C4,C5 and C6
compounds from various gas streams
generated by crude distillation, cokers, cat
crackers, reformers and hydrocrackers
Production of desulfurized dry gas
consisting mostly of methane and ethane for
use as fuel gas or feedstock for hydrogen
production
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THE PROCESS (FIGURE
13.3) Compressing the gas
Feed an absorber- deethanizer unit where naphta is used to absorb 90% of the C3 and all the C4
+
The vaporized heavy hydrocarbons leave the top of the absorber with the light gases and are recovered in a sponge absorber
The non volatile kerosene can be used as sponge oil
The deethaniser rich oil will feed the debutanizer where all the propane and butane are recovered and then desulfurized and separated in a depropanizer
Natural gasoline from the bottom of the debutanizer is the feed of the naphta splitter where Light Straight Run ( C5 and C6) is produced at the top sweetened and used as gasoline blend. The lean absorbing oil is obtained at the bottom
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TWO STAGES PROCESS
( Page 144)
The fresh feed is mixed with Make up and recycled Hydrogen
then pass through a heater and the first reactor ( If the feed is not treated, It should pass through a guard reactor before hydro cracking to eliminate the impurities such as organic sulfur and nitrogen compounds)
The hydrocracking reactor is operated as high temperature to convert 40 to 50% vol of the reactor effluent to material boiling below 4000F.
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The reactor effluent goes through heat
exchangers and a high pressure
separator where the gas rich in hydrogen
is recycled . The liquid go to the
distillation column where light gases,
naphta and diesel are produced
The fractionator bottom is used as a
feed to the second hydrocracker
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Typical hydrocracker
feedstocks
Feed Products
Kerosine Naphta
SR- Diesel Naphta , jet fuel
Atmospheric G.oil Naphta, jet fuel, diesel
Vacc. G.oil Naph, J,Fuel, Diesel, Lube oil
Light FCC cycle gas oil Naphta
Heavy FCC cycle gas oil Naphta / distillates
Light Cooker Gas oil Naphta / distillates
Heavy Cooker Gas oil Naphta / distillates
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Hydrocracking Reactions
Cracking is the scission of carbon-carbon single bond
hydrogenation is the addition of hydrogen to a carbon-carbon double bond
Cracking provide double bonds for hydrogenation (page 139 and 140)
Isomerization is another reaction in hydrocracking
The olefinic products formed are rapidly hydrogenated maintaining a high concentration of high octane isoparaffins and preventing the back reactions to straight chain molecules
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Hydrotreater
Number of reactions take place:
Olefin saturation
aromatic ring saturation
cracking is almost insignificant
The exothermic heats of
desulphurization and denitrogenation are
high ( 2800 kJ/std m3)
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The saturation of olefins contribute also
in the exothermicity of the reaction,
However for virgin stocks, this is
negligible reaction
Reduce the water content to 25 ppm
In average, this process consume 27 to
54 m3 of hydrogen by m3 of feed)
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Hydrocracking Process
Figure 7.2
Freed is mixed with recycled hydrogen
Pass trough a heater and a first reactor
If the feed was not treated , the first reactor is a guard reactor with catalyst Co-Mo on silica alumina to convert organic sulfur and nitrogen compounds to protect the hydrocracking catalyst
The hydrocracking reactor is at 660-7850F and 1000-2000 psig
The reactor effluent goes trough heat exchanger and a high pressure separator
The hydrogen is recycled and the liquid sent to distillation
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Process variables
Reactor temperature is the primary means of conversion
control..200C increase in temperature almost double the
conversion rate
Reaction Pressure: The primary effects of pressure on
conversion is in its effects on the partial pressure of
hydrogen which increases conversion…the effects of
partial pressure of ammonia is to decrease conversion but
this effect is smaller than the increase of partial pressure of
hydrogen
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Space velocity: The volumetric space velocity is the ratio of liquid flowrate in barrels per hour on the catalyst volume in barrels.
The catalyst volume is constant, therefore , space velocity varies directly with feed rate. As feed rate increases, the contact time with catalyst decreases and therefore the conversion decreases
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Nitrogen Content: The increase of nitrogen content will
deactivate more the catalyst and therefore conversion
decreases
Hydrogen sulfide: A small concentration of H2S acts as
catalyst to inhibit the saturation of aromatic rings which
have higher octane number than the naphtenic. However,
small amount of H2S produces very low smoke point jet fuel
( Bad burning quality jet fuel)
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Hydrogen sulfide: A large amount of H2S increases
corrosion and inhibit the cracking activity of the catalyst
Heavy Polynuclear Aromatics: HPNA
HPNA are formed in small amounts from hydrocracking
reactions….these amounts can build up when the
fractionator's bottoms is recycled and causes fouling of
heat exchangers
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ETHYLENE
Lightest olefinic hydrocarbon
Does not occur freely in nature
Largest building block for a variety of petrochemicals such as plastics, resins, fibers, solvents,…
Produced primarily from the thermal cracking of hydrocarbons feedstocks derived from natural gas and crude oil
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PRODUCTION OF
ETHYLENE
Thermal Pyrolysis of hydrocarbons
Conventional feedstocks include ethane, propane, butane and naphta
Reaction of cracking occurs in tubular coils located in the radiant zone of furnaces
Steam is added to reduce the partial pressure of hydrocarbons in the coils
Transformation of saturated hydrocarbons to olefins is endothermic reaction and require temperature around 750 to 9000C
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Reactions of thermal cracking
Rice and Herzfeld proposed the concept of free radical mechanism
Chain Initiation: Initiation of Radicals
CnH2n+2 CmH2m+1. + C(n-m)H2(n-m)+1.
Chain propagation: Reaction of Radicals with molecules
CnH2n+2 + CmH2m+1. CnH2n+1. + CmH2m+2
CnH2n+1. CmH2m + C(n-m)H2(n-m)+1.
Chain Termination: Disappearance of radicals
CnH2n+1. + CmH2m+1. CnH2n + CmH2m+2
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PROCESS
First Stage: Pyrolysis or cracking of feed
Second Stage: Gasoline fractionator to remove heavier fuel components if the feed is naphta. Bottom temperature 190 to 2300C and Top temperature 95 to 1200C
Third Stage : Fuel Oil Stripper where fuel oil are stripped and sent to fuel handling facilities
Fourth Stage: Water Quench tower where the cracked gas is cooled to 400C with circulating water
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PROCESS
Fifth Stage: Compression: The cracked gas leaving the quench tower is compressed to 32 to 37 bars in four or five centrifugal compressor
Sixth Stage: Acid gas removal and drying:
between the third and fourth stage of compression, CO2
and H2S are removed with dilute caustic soda
Seventh Stage: Chilling train and Demethanizer
to separate H2, ethane from C2+
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PROCESS
Eighth stage: Deethanizer and Ethylene
production
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High Density Polyethylene
HDPE
The Hastalen process is designed to
produce HDPE from ethylene monomer
The Process consists on 2
polymerization reactors that can be
operated in parallel ( unimodal product)
or in series ( bimodal product)
Catalyst is injected in the stirred slurry
reactor where the liquid phase is hexane
as suspending agent
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HDPE
After the reaction, the polymer is
separated from the slurry mixture and
dried
The polymer is send to the extrusion
unit
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PROCESS
Catalyst preparation and feeding
Polymerization
Powder drying
Extrusion and pellets handling
Hexane recycling
Butene recycling
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Catalyst preparation
Production of Catalyst THT/THE/ THB is
performed batchwise from four
commercially available components in
one catalyst preparation vessel under
precisely defined conditions
Finished catalyst batches are
transferred into catalyst dilution vessels
and further diluted to the correct
concentration
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POLYMERIZATION
The reactors are CSTRs. They are operated at different conditions and residence times
The reactor is fed continuously with monomers, catalyst and co catalyst, hydrogen and hexane recycled from the process
The reaction is extremely exothermic; the pressure is around 5 to 10 bars and the temperature around 75 to 850C.
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The heat of reaction is removed by
cooling water
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HDPE Powder Drying /
Diluent's separation
Suspensions leaving the receiver ( Figure) are
separated in a decanter centrifuge into a liquid
and a solid fraction
The solid part will feed a fluidized bed dryer
operated with nitrogen and the liquid part (
hexane) goes back to reactors
Dried HDPE powder passes through a sieve
and is pneumatically conveyed by nitrogen to
the extrusion unit
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Reaction Mechanisms
The Hostalen process is based on a
Ziegler reaction mechanism with the so
called ziegler catalyst.
These catalyst are produced with TiCl4and Al(C2H5)3 according the the formula
given in Figure
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POLYPROPYLENE
The polymerization of propylene to polypropylene was performed in 1954 by Giulio Natta ( 1963 Nobel prize in Chemistry)
Propylene can polymerize into three distinct structural chains ( Figure 16.1.1)
* Isotactic
* syndiotactic
* atactic
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Isotactic PP occurs when all the methyl
groups are located on the same side
Syndiotactic PP occurs when the methyl
groups are located on alternating sides
of the chain
Atactic PP occurs when the methyl
groups are randomly dispersed around
the chain
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The catalyst System
The catalyst system is composed of:
* Solid catalyst, generally TiCl4supported by MgCl2
* an internal or external Lewis Base
* an Aluminium Alkyl
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Catalyst Function
The catalyst is composed of two main
elements: a transitional salt and an inert
support structure
The MgCl2 support has the following function:
* It creates a highly disorganized crystalline
structure the reaction sites are greater in
number and therefore higher activity
The active part of the catalyst ( TiCl4) should
be activated by an Aluminum Alkyl and Lewis
base
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Catalyst Evolution ( Table 16.1.1)
The rapid & successful
commercialization of PP is due to the
continuous development of new
improved catalysts
the yield of catalyst has increased from
1 to 120 kg/ g catalyst
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Polymer Chain Control
The length of the polymer chain has a significant impact on its performances and mechanical properties.
Direct measurement of the chain length is difficult For many years the intrinsic Viscosity IV was used
IV results were directly related to the polymer chain
The higher the IV the longer is the chain
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Recently, The melt-flow rate (MFR) technique is used
MFR is the weight of melted polymer that can flow through a specific orifice under standard conditions
Standard Load = 2.16 kg
Standard temperature = 230 0C
Standard Time = 10 min
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Molecular Weight Distribution
(MWD)
In the polymer, the chains have different length
and one way to know the length distribution is
the MWD
A fundamental measurement of MWD is gel
permeation also known as size-exclusion
chromatography
In this technique, the polymer is dissolved in a
solution and the chains elute at different times
through a porous media
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MWD
We can distinct Mn and Mw
Mn is the number average molecular weight
Mw is the weight average molecular weight
i
ii
nn
MnM
iiiiw MnMnM /2
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Polydispersity
Polydispersity is the ration of Mw/Mn
Polydispersity is used to describe the
MWD
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PP Polymerization Processes
In the 1960’s, PP process used first
generation low-yields catalyst ( <
1000kgPP/ kg of catalyst) in mechanically
stirred reactors filled with an inert hydrocarbon
diluent
PP produced had unacceptable high residual
metals and contained 10% atactic PP which
needed separation
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Second Generation catalyst
An intermediate step was reached with
a second generation catalyst increasing
yield to 6000/15000Kg PP by kg of
catalyst
But isotacticity not yet at level that allow
simplification of the process
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Third Generation Catalysts
In the 1970’s, the discovery of the third
generation catalyst ( 15000 to 30000kg
PP by kg catalyst) eliminated the need
for catalyst residue removal but atacticity
was still high and the atactic recovery
step was not eliminated
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The Fourth Generation
Catalyst
In the 1980’s, the fourth-generation high yield , high selectivity ( HY/HS) catalyst was discovered ( 30000kg of PP by kg of catalyst)
this eliminated the need of catalyst and atactic removal
In 1982, the Spheripol process was developped
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Spheripol Process
It has the unique ability to produce
polymer spheres directly in the reactor
Spherical PP differs considerably from
the small, irregularly shaped, granular
particles produced by other technologies
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Process Description
The Polymerization Unit involves the following
sections:
* Catalyst Feeding
* Polymerization:
- Prepolymerization
- Bulk Polymerization
- Gas phase Polymerization
- Finishing
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The catalyst
The catalytic system has three
components:
- Solid catalyst
- Aluminium Alkyl used to activate the
catalyst
- Lewis Base used to control the
cristallinity and the homopolymer grade
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Bulk polymerization
Bulk Polymerization employs jacketed tubular reactor completely filled with liquid propylene to produce homopolymer, random copolymer and terpolymer
The catalyst, liquid propylene and the hydrogen are fed continuously into the loop reactor
The Polymerization reaction is exothermic
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Commercial uses of PP
Table 16.3.1
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Synthetic Polymers
The synthetic polymer industry is the major
use of many petrochemical monomers such as
ethylene, propylene, styrene and vinyl chloride
Many articles previously produced from natural
material such as wood, cotton, wool, iron ,
aluminum and glass are now replaced or
partially substituted by synthetic polymers
Polymerization can now be tailored to produce
polymers stronger than steel
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Thermoplastics
Polyethylene ( LDPE and HDPE)
Polypropylene
Polyvinyl Chloride (PVC)
Polystyrene
Nylon resins
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POLYETHYLENE
The most extensively used thermoplastic
Because of the abundance of the monomer from the abundant raw materials ( FG, LPG, naphta)
Other factors include
* Low cost, ease processing the polymer, resistance to chemicals,
World production of PE was 100 billions pounds in 1997 and predicted 300 billions pounds in 2015
The two grades of PE include LDPE and HDPE
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LDPE
Produced under High pressure in the presence of free radical initiator
Temperature of reaction: 100-2000C
Pressure of reaction: 100-135 atm
Polymer highly branched (?)
Low crystallinity (?)
By adding copolymers , we obtain copolymers with lower crystallinity, higher impact stenght
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HDPE
Low pressure process
High cristallinity
high melting point ( compared to LDPE)
due to absence of branching
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Properties and uses of PE
Inexpensive thermoplastic
can be modeled to almost any shape, extruded into fibers or filaments and blown or precipitated into films or foils
LDPE is flexible and transparent can be used for the production of films and sheets and for film production
HDPE can be used to produce bottles and hollow objects by blow molding ( about 64% of bottles are made by HDPE)
Injection molding is used to produce solid objects
Pipes produced from HDPE are flexible, tough and corrosion resistant
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POLYPROPYLENE (PP)
Major thermoplastic polymer
The delay in PP production is attributed to its polymerization
PP produced by free radical is mainly atactic form having low cristallinity which is not suitable for thermoplastic or fiber use
The turning point in PP production is the development of a Ziegler-type catalyst developed by Natta to produce isotactic PP
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Properties and Uses of PP
Good chemical and electrical resistance
Low water absorption
Light weight ( lowest thermoplastic
polymer density)
High abrasion resistance
high impact strength
no toxicity
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PP can be extruded into sheets
Due to its light weight and toughness,
PP is widely used in automobile parts
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PVC
widely used thermoplastic
blow modeled into bottles, used in common
items such as garden hoses, shower curtains,
irrigation pipes, paint formulation
Excellent chemical and abrasion resistance
self extinguishing due to the presence of
chlorine atom
Can be used as tablecloth, cable insulation
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POLYSTYRENE (PS)
Polymerized by free radical or using coordination catalysts
Copolymers Styrene- acrylonoitrile (SAN)
have higher tensile strength than PS
A copolymer of acrylonitrile, butadiene and styrene (ABS) is an engineering plastic due to its better mechanical properties
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Properties and Uses of PS
Highly amorphous if produced by free radical
polymerization
SBR ( a block copolymer with 75% Butadiene
) is produced by anionic polymerization
PS is used mostly in packaging
Molded PS is also used in automobile interior
parts, furniture and home appliances
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Project by Internet
Uses of PE
Uses of PP
What is PVC ( polyvinyl Chloride)
What is PS ( Polystyrene)