Download - Distillation of Crude
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DISTILLATION OF
CRUDE
PRESENTED BY:
NITISH SALVI
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ContentsABOUT CRUDE.
DISTILLATION BASICS.
VARIOUS FRACTIONS OF DISTILLATION
COLOUMN.
DETAIL ABOUT FRACTIONS.
SEPERATION.
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Crudeoil
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In crude distillation process, crude oil is first heated
in order to vaporize it and then passed into a
fractionating column in which unvapourised liquid
flows down and out of the bottom as residue while
vapour rise up the column.
In doing so they are contacted with a down flowing
stream of reflux 'on a number of trays filled with
special contacting devices. the tower gets
progressively cooler towards the top & so from the
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various fractions obtained by crude distillation canbe explained as follows:
1.GAS FRACTIONS: NATURAL
GAS,LPG,REFINERY GAS.
2.LIGHT ENDS:
GASOLINE,NAPTHA,KEROSENE.
3.INTERMEDIATE ENDS: FUEL OIL,DIESEL
OIL,GAS OIL,WHITE OIL.
4.HEAVY ENDS:LUBRICATING
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Liquid petroleum gas :
This gas contains
propane & butane & is widely used in
cylinders as domestics fuel or laboratory gas
burners the gas can be easily liquefied &
stored in liquid form. It is very popular as a
cooking gas.
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REFINERY GAS:
This is the off-gas from
refinery operation. it contains a part from
methane & ethane,H2S,H2,SO2 etc.The H2S
content in Indian crude is not much as Indian
crude contains very little sulphur (
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Light fractionsGASOLINE: Commonly known as petrol. it isproduced to a maximum quantity. it is used as a fuelfor automobiles & other light vehicles.
NAPTHA: the term naphtha is refered to thefractions having properties between gasoline &kerosene. It consists of a complex mixture ofhydrocarbon molecules generally having between 5
and 12 carbon atoms. It typically constitutes 1530%of crude oil, by weight. Light naphtha is the fractionboiling between 30 C and 90 C and consists ofmolecules with 56 carbon atoms. Heavy naphtha
boils between 90 C and 200 C and consists ofmolecules with 612 carbons.
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kerosene:
it is the most important constituent of
India. It is used as a household fuel for cooking as well
as for illumination. It is also used as a fuel for jet(its
freezing point must be very low than-25 c) Kerosene
is a thin, clear liquid formed from hydrocarbons, with
a density of 0.780.81 g/cm3, is obtained from the
fractional distillation of petroleum between 150 C
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Intermediate fractionsDiesel oil: these oil which are used in heavy
vehicles such as trucks,buses,locomotives,tractors
etc. have become extremely important. they must be
clean must have good ignition quality for easy
starting of low engine,pressure,good fluidity so that it
does not give much resistance ,to flow but at the
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Fuel oil or furnace oil:
As the name suggest theseare primarily used as fuel in furnace and also inpower station boilers. Nowadays due to shortage ofnaphtha and natural gas they are also used as raw
material for making ammonia and fertilizers.Gas oil:These are used as absorbents for
hydrocarbon gases. This is also used for makingwith tar and asphalt for reducing their viscosity.
Another use is for increasing the calorific value oflow calorific value gases such as producer gasand water gas . Most of it is nowadays used tocrack light fractions.
White oil:
This is primarily used for making hair oil orcosmetics.
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Heavy fractionsLubricating oil:
These include various oils used forlubrication of machinery such as motor,engine,machine,gear
oil etc. the important properties of the lubricating oil areviscosity, flash point.Paraffin wax:
Paraffin wax is used formaking wax paper candles, insulatingmaterials, sealing compounds and ointment.
Mineral jelly:
This is used for making ofcosmetics, sealing compound for preventing leakespecially in acid lines. another use is to apply it
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ResidueAsphalt:
the main use of asphalt is for water proofing ofroofs. it is used in road making and protective coating andinsulating material.
Petroleum coke: coke is used for making carbon electrodesother use of petroleum coke is in manufacture of calcium carbideand black paints.
Grease: these are semisolid mixture of solids they are used forlubrication as well as sealing of moving parts. grease are usedwhere lubrication cannot be done.
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Distillation is a mass transfer separation wherein a mixture containing two or morecomponents can be separated into individualcomponents or group of components using
counter-current multistage liquid-gascontacting equipment.
Ease of separation depends on- feed concentration
- relative volatility of components
SEPERATION:
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Each stage in a distillation column providescontact for gas and liquid.
Section of column above feed point is called
enriching section or rectifying section.
Section below the feed point is called stripping
or exhaustive section.
Liquid to column is provided by reflux while
vapor to the column is provided by reboiler.
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Feed stream provides both liquid and vapor.
Vapours going up and liquid flowing down are
in equilibrium.
Vapours leaving to the column top are rich in
the more volatile components (lighter
components).
The vapours are condensed and part of it is
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In this way, at each stage, vapor leaving the
stage becomes enriched in more volatile
component and liquid leaving the stage
becomes concentrated in less volatilecomponent.
Relative volatility depends on vapor pressure.
For an ideal binar s stem, relative volatilit is
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The relative volatility can be altered by
changing the operating pressure.
Separation becomes easier and easier as
system pressure is lowered.
Lower operating pressure requires big diametercolumn.
Vacuum distillation is preferred when
se aration is difficult or tem eratures are to be
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Factors Affecting
DistillationNumber of trays in a column
Column capacity
Reflux rates to column
Feed Composition
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ABNORMAL OPERATION
FLOODING
ENTRAINMENT
PULSATION
DUMPING
COONING
TRAPPED WATER
HIGH LIQUID LEVELS
DRY TRAYS
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Flooding can berecognized by:
Poor quality products
Small temperature gradient
Pressure drop larger than normal
Pressure fluctuations
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Intermittent flow of vapor through slots of
bubble caps.
Causes low tray efficiency.
Depends on physical properties of the two
phases, cap construction and tray layout.
Pulsation
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Dumping
High liquid loads causes liquid to enter the gapand fall through risers.
Reduces efficiency of column.Can be avoided by preventing the liquid from
entering the slots at high velocity.
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High Liquid Levels
Trays behave as if they are flooded.
Efficiency of fractionation reduces.
Height of liquid level is controlled byadjusting flow rate of bottom product.
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Distillation Column
ControlTwo main variables to be controlled are
:-
Reflux ratio
Heat supplied to the column
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