PETROLEUM
Petroleum is a complex mixture of organic liquids
called crude oil and natural gas, which occurs
naturally in the ground and was formed millions
of years ago.
Crude oil and natural gas are of little use in their
raw state; their value lies in what is created from
them: fuels, lubricating oils, waxes, asphalt,
petrochemicals and pipeline quality natural gas.
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INTRODUCTION
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Oil refining is a key activity.
Over 600 refineries worldwide have a
total annual capacity of more than 3500
x 106 tones.
Goal of oil refining is two fold: i. production of fuels for transportation, power
generation and heating; and
ii. production of raw materials.
Oil refineries are complex plants but are
relatively mature and highly integrated.
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OIL REFINING PRODUCTION PROCESS
Desalting and Dewatering
Distillation
Reforming
Cracking
Alkylation
Isomerisation
Polymerisation
Hydrotreating
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Physical Chemical
Thermal Catalytic
Desalting and
Dewatering
Distillation
Solvent extraction
Propane Deasphalting
Solvent dewaxing
Blending
Visbreaking
Delayed coking
Flexi coking
Hydrotreating
Catalytic reforming
Catalytic cracking
Hydrocracking
Catalytic dewaxing
Alkylation
Polymerization
Isomerization
PHYSICAL AND CHEMICAL PROCESSES
DESALTING AND DEWATERING
Crude oil is recovered from the reservoir mixed with a
variety of substances: gases water and dirt
(minerals).
Desalting is a water washing operation performed at the production field and at the refinery site for
additional crude oil cleanup. If the petroleum from
the seperators contains water and dirt, water
washing can remove much of the water soluble minerals and entrained solids. If these crude oil
contaminants are not removed, they can cause
operating problems during refinery processing, such
as equipment plugging and corrosion as well as
catalyst deactivation.
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DESALTING PROCESS
FEED
STOCK
FROM PROCESS TYPICAL
PRODUCT
TO
Crude Storage Treating Desalted
Crude
Atm. Distillation
Tower
Waste waters Treatment
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DESALTING OF CRUDE OILS
The desalting process consist of diluting this high salt content brine
with incoming fresh water to produce low salt content water. Salt
content is measured as NaCl Per Thousand Barrels of oil and its
range varies from 10 to 200 PTB. Crude oil contaminated by salt
water when shipped in tankers.
1. Primary settling.
2. Heating the oil before settling.
3. Sometimes the addition of chemicals to the mixture before settling gave
further improvements.
4. To get consistently good result practically all refiners now use
electrical desalting equipment.
CRUDE OIL DISTILLATION Crude oil consists of hydrocarbons varying in boiling range from
methane to asphalt.
The aim of crude oil distillation is to fractionate the crude oil into
light hydrocarbons (C1 through C4),
gasoline components and
middle distillates (kerosene, gas oil) which can be marketed
directly or with a minimum of further processing.
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DISTILLATION
Distillation separates chemicals by the difference
in how easily they vaporize
The two major types of classical distillation
include
continuous distillation and
batch distillation
Other ways to categorize distillation are by the
equipment type (trays, packing), process
configuration (distillation, absorption, stripping,
azeotropic, extractive, complex), or process type
(refining, petrochemical, chemical, gas treating).
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CRUDE OIL DISTILLATION PROCESSES
1.ATMOSPHERIC
2.VACCUM
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ATMOSPHERIC DISTILLATION PROCESS
FEED
STOCK
FROM PROCESS TYPICAL
PRODUCT
TO
Crude Desalting Separation Gases Atm. Distillation tower
Naphthas Reforming or treatment
Kerosene or
distillates
Treating
Gas oil Catalytic cracking
Residual Vacuum tower or
visbreaker
Carried out at pressures slightly above atmospheric pressures to
1.Raise the bpt of the light ends
2.Pressure the uncondensed gases to the meant processing step
3.Allow for column pressure drop.
Crude oil is heated to a temp range of 350-360 oC
Steam is introduced at the bottom section of the column at a rate of 12-24kg/meter 3of
column bottoms
SPECIAL FEATURES
The side stream products are steam stripped to remove the lighter components
Pump-arounds :-By providing reflux to the column below a pump-around zone gives a more Uniform liquid loading ,there by reducing the net liquid loading .
Intermediate refluxes are withdrawn to recover maximum heat and to have uniform vapour and liquid loads in the column.
About 80% of heat can be recovered by circulating reflux.
Atmospheric distillation of crude oil 1
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15 Atmospheric distillation of crude oil
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Petroleum gas - used for heating, cooking, making plastics
small alkanes (1 to 4 carbon atoms) commonly known by the names methane, ethane, propane, butane boiling range = less than 104 degrees Fahrenheit / 40 degrees Celsius often liquefied under pressure to create LPG (liquified petroleum gas)
Naphtha or Ligroin - intermediate that will be further processed to make
gasoline
mix of 5 to 9 carbon atom alkanes boiling range = 140 to 212 degrees Fahrenheit / 60 to 100 degrees Celsius
Gasoline - motor fuel
liquid mix of alkanes and cycloalkanes (5 to 12 carbon atoms) boiling range = 104 to 401 degrees Fahrenheit / 40 to 205 degrees Celsius
Kerosene - fuel for jet engines and tractors; starting material for making other
products
liquid mix of alkanes (10 to 18 carbons) and aromatics boiling range = 350 to 617 degrees Fahrenheit / 175 to 325 degrees
Celsius
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Gas oil or Diesel distillate - used for diesel fuel and heating oil; starting material
for making other products
liquid alkanes containing 12 or more carbon atoms boiling range = 482 to 662 degrees Fahrenheit / 250 to 350 degrees Celsius
Lubricating oil - used for motor oil, grease, other lubricants
liquid long chain (20 to 50 carbon atoms) alkanes, cycloalkanes, aromatics boiling range = 572 to 700 degrees Fahrenheit / 300 to 370 degrees Celsius
Heavy gas or Fuel oil - used for industrial fuel; starting material for making other
products
liquid long chain (20 to 70 carbon atoms) alkanes, cycloalkanes, aromatics boiling range = 700 to 1112 degrees Fahrenheit / 370 to 600 degrees Celsius
Residuals - coke, asphalt, tar, waxes; starting material for making other products
solid multiple-ringed compounds with 70 or more carbon atoms boiling range = greater than 1112 degrees Fahrenheit / 600 degrees Celsius
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VACUUM DISTILLATION PROCESS
Feed Stock From Process Typical Product To
Residuals Atm. Tower Separation Gas Oil Catalytic Cracker
Lubricants Hydrotreating Or
Solvent
Residual Deasphalter,
Visbreaker, Or
Coker
The atmospheric residue called reduced crude oil, contains a large volume of
distillable oils.
To remove remaining distillates ,reduced crude oil is further fractionated under
vacuum.
Vacuum column is normally operated at an absolute pressure of 80-110 mm
Hg
IMPORTANT POINTS TO BE CONSIDERED
Flash zone temp
Flash zone pressure
Pressure drops for different equipments like; pre-condenser, over head line etc
VACCUM DISTILLATION OF REDUCED CRUDE OIL
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residue from the vacuum
column may be used for
bitumen production
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1. The over flash condenses on the wash
section plates and returns to the flash
zone and bottom stripping section,
prevents coking in the wash section plates
and also carryover of coke to the bottom
side-stream product.
2. Steam (30 %of the total steam)
is introduced in the furnace coil
to decrease the residence time
and minimize coking
Requirement depends on PP of hydrocarbon to reduce the partial pressure of
hydrocarbons in the flash zone
Also help to strip off light ends in the bottom product
If vacuum residue
is left to remain at
high temperature,
coke formation
may start due to
cracking.
the maximum flash
zone temperature is
380-400oC
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Various Products From The Vacuum Distillation Of
Atmospheric Residues Along With Their Uses Are Given
Below
Product Uses
Light Vacuum Gas Oil (LVGO) (A) A Blending Component For LDO
(B) Feedstock For Catalytic Cracker /Hydrocracker
Heavy Vacuum Gas Oil (HVGO) (A) A Feed Component For Visbreaker
(B) Feedstock For Catalytic Cracker/Hydrocracker
Vacuum Residue (VR) (A) Bitumen Production
(B) A Feed Component For Visbreaker
OPERATION OF FRACTIONATING COLUMNS
1. TEMPERATURE
The top temperature of the column is usually dew-point temperature of the overhead vapors at the operating pressure
The top temperature of the column must be just high enough to allow complete vaporization of overhead product
2. COLUMN PRESSURE
not the op. variable.
High pr. Operation reduces relative volatility of components
Column dia. Low at high pr.
Lowest possible pr. is normally recommended
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3. FLOW RATES
Determined by feed composition and degree of separation
4. REFLUX : high reflux ratio is recommended
V-L contact
Maintained temp. gradient
5. REBOILER/STRIPPING STEAM
Max. amount of the steam should be used subject to the
Condenser should be able to take up load
Lowest side product does not become colored and
Column does not get flooded
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6. STABILITY OF COLUMN OPERATION
i. Pulsation:- This occurs when the amount of vapor passing through a
tray is so small that the bubble caps pass vapor intermittently
ii. Dumping:-This results at relatively high liquid loads when some of the
upstream bubble caps do not pass vapor.
iii. Coning:- This takes place when the combination of weir height and the
liquid crest over the weir does not adequately seal the cap slots.
iv. Blowing:-This results when the amount of vapor passing through the
bubble caps is so large that it literally tears holes in the liquid on the
tray.
v. Entrainment:-It is of two types:
(i) A relatively fine mist is carried to the tray above by superficial vapor
velocity
(ii) Large droplets of liquid are jetted from one tray to the next
vi. Flooding:-This occurs when the level of the liquid-foam mixture in the
downpipe builds up and overflows to the tray above
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28 Thank you