PETROLEUM
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Petroleum is a complex mixture of organic liquids
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called crude oil and natural gas, 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
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:
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production of fuels for transportation, power generation and heating; and ii. production of raw materials. i.
Oil refineries are complex plants but are relatively mature and highly integrated. i ntegrated. 2
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OIL REFINING PRODUCTION PROCESS 1 / 2 3 / 2 0 1 3
Desalting and Dewatering Distillation Reforming Cracking Alkylation Isomerisation Polymerisation Hydrotreating
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PHYSICAL AND CHEMICAL PROCESSES Physical
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Chemical Thermal
Catalytic
Desalting and Dewatering
Visbreaking
Hydrotreating
Delayed coking
Catalytic reforming
Distillation
Flexi coking
Catalytic cracking
Solvent extraction
Hydrocracking
Propane Deasphalting
Catalytic dewaxing
Solvent dewaxing
Alkylation
Blending
Polymerization Isomerization
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DESALTING AND DEWATERING Crude oil is recovered from the reservoir mixed with a variety of substances: gases water and dirt (minerals).
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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
Crude
Storage
PROCESS
Treating
TYPICAL PRODUCT
TO
Desalted Crude
Atm. Distillation Tower
Waste waters
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Treatment
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DESALTING OF CRUDE OILS The desalting process consist of diluting this high salt content brine
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with incoming fresh water to produce low salt content water. Salt content is measured as NaCl Per Thousand Barrels of oil and its
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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 electrical desalting equipment.
practically all refiners now use 8
CRUDE OIL DISTILLATION
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Crude oil consists of hydrocarbons varying in boiling range from methane to asphalt.
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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. 9
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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
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Atmospheric distillation of crude oil 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 •
•
•
•
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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. 14
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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 •
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• •
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
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• • •
•
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
Residuals
From
Atm. Tower
Process
Separation
Typical Product
To
Gas Oil
Catalytic Cracker
Lubricants
Hydrotreating Or Solvent
Residual
Deasphalter, Visbreaker, Or Coker
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VACCUM DISTILLATION OF REDUCED CRUDE OIL •
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 C vacuum.
•
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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
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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.
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the maximum flash zone temperature is 380-400oC
• •
•
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.
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Various
Products
From The
Vacuum
Distillation
O
Atmospheric Residues Along With Their Uses Are Given Below
Product Light Vacuum Gas Oil (LVGO)
Uses (A) A Blending Component For LDO (B) Feedstock For Catalytic Cracker /Hydrocracker
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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
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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 •
•
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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 •
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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.
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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 27
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Thank you
