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