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Course: Chemical Technology (Organic) Module VI

Lecture 1

Introduction: Status ofPetroleum Refinery, Crude Oil

And Natural Gas Origin,

Occurrence, Exploration,

Drilling And Processing, Fuel

Norms

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LECTURE 1 

INTRODUCTION

Petroleum and derivatives such as asphalt have been known and used for almost 6000 years and

there is evidence of use of asphalt in building more than 600 years ago. Modern petroleum

refining began in 1859 with discovery of petroleum in Pennsylvania and subsequent

commercialization. The exploration of petroleum originated in the latter part of the nineteenth

century [Speight, 1999].

CRUDE OIL AND NATURAL GAS ORIGIN, OCCURRENCE,EXPLORATION AND DRILLING

Oil and natural gas were formed hundred years ago from the prehistoric plant and animals. it is

 believed that hydrocarbon formed by the thermal maturation of organic matter buried deep in

earth. over the millions of years under extreme pressure and high temperature these organic

matter converted to hydrocarbons consisting of oil and gas. Hydrocarbons are present in the

variety of forms: koregen, asphalt, crude oil, natural gas, condensates, and coal in solid form.

Oil and gas production includes exploration, drilling, extraction, stabilization. The underground

traps of oil and gas are called reservoir. Various types of traps are structural traps, stratigraphic

traps and combination traps Most reservoir contain water also along with oil and gas. Reserves

are classified as proven, probable and possible reserves. Earlier finding of oil and gas was matter

of luck and hit and miss process. Tools used for oil and gas exploration are based and dependent

on gravity change, magnetic field change, time, change and electrical resistance. However it has

 become now more challenging and complex. With advent of three dimensional seismic

technology which is based on the sound waves, identify the subsurface formation by reflection of

sound, there has been much improvement in identification of oil and gas traps and reservoirs.

Seismic technology significantly improves the method of estimating the oil and gas deposits.

 Next step after exploration is the drilling of exploratory well. Drilling may be vertical drilling or

horizontal drilling. Drilling may be performed on-shore or off-shore. Horizontal drilling and

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hydro-fracturing has resulted in economical and more productive drilling of shale gas which was

not economical with conventional vertical drilling.

COMPOSITION OF PETROLEUM (CRUDE OIL)Petroleum (Crude oil) consists of mainly carbon (83-87%) and hydrogen (12-14%) having

complex hydrocarbon mixture like paraffins, naphthenes, aromatic hydrocarbons, gaseous

hydrocarbons (from CH4  to C4H10) [Mukhulyonov et al., 1964]. Table M-VI 1.1  gives more

details about composition of petroleum. Besides crude oil also contains small amount of non

hydrocarbons (sulphur compounds, nitrogen compounds, oxygen compounds) and minerals

heavier crudes contains higher sulphur. Depending on predominance of hydrocarbons, petroleum

is classified as paraffin base, intermediate base or naphthenic base.

Table M-VI 1.1: Composition of Petroleum

Hydrocarbons

Hydrogen

Family

Distinguishing

characteristics

Major

hydrocarbonsRemarks

Paraffins

(Alkanes)

Straight carbon

chain

Methane, ethane,

 propane, butane,

 pentane, hexane

General formula CnH2n+2 

Boiling point increases as the

number of carbon atom increases.

With number of carbon 25-40,

 paraffin becomes waxy.Isoparaffins

(Iso alkanes)

Branched

carbon chain

Isobutane,

Isopentane,

 Neopentane,

Isooctane

The number of possible isomers

increases as in geometric

 progression as the number of carbon

atoms increases.

Olefins

(Alkenes)

One pair of

carbon atoms

Ethylene,

Propylene

General formula CnH2n 

Olefins are not present in crude oil,

 but are formed during process.

Undesirable in the finished product

 because of their high reactivity. Low

molecular weight olefins have good

antiknock properties.

 Naphthenes 5 or 6 carbon

atoms in ring

Cyclopentane,

Methyl

cyclopentane,Dimethyl

cyclopentane,

General formula CnH2n+2-2R n 

R  N is number of naphthenic ring

The average crude oil contains about

50% by weight naphthenes.

 Naphthenes are modestly good

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cyclohexane,1,2 dimethyl

cyclohexane.

components of gasoline.

Aromatics 6 carbon atom

in ring with

three aroundlinkage.

Benzene,

Toluene, Xylene,

Ethyl Benzene,Cumene,

 Naphthaline

Aromatics are not desirable in

kerosene and lubricating oil.

Benzene is carcinogenic and henceundesirable part of gasoline.

Non Hydrocarbons

 Non-hydrocarbons  Compounds Remarks

Sulphur compounds Hydrogen sulphide,

Mercaptans

Undesirable due to foul odour

0.5% to 7%

 Nitrogen compounds Quinotine, Pyradine,

 pyrrole, indole, carbazole

The presence of nitrogen

compounds in gasoline and

kerosene degrades the colour of

 product on exposure to sunlight.

They may cause gum formation

normally less than 0.2.

Oxygen compounds  Naphthenic acids, phenols Content traces to 2%. These

acids cause corrosion problem at

various stages of processing and

 pollution problem.

Source: Mall,2007

PROCESSING OF PETROLEUM (CRUDE OIL)

Processing of Petroleum from drilling: when petroleum is drilled and brought to the surface, the

 pressure drops resulting in separation of gases from the crude oil. Further processing of crude

involves separation of water and oil and salt. Associated natural gas is further processed for

separation of natural gas, condensate, acid gases. Crude oil varies in appearance from brownish

green mobile liquid to black viscous and sometimes semisolid. . Figure M-VI 1.1 illustrates the

 process of oil and gas processing [Ravindranath and Habibula, 1992]

.

CRUDE OIL PROCESSED IN INDIA

Both indigenous and imported crude oil are processed in India. Various imported sources of

crude oil is given in Table M-VI 1.2.There has been continuous changes in the crude oil quality.

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Table M-VI 1.2: Imported Crude Sources

Middle East 

Kuwait, Dubai, S. Arabia( Arab Mix, Arab medium), Iraq,

Abu Dhabi, UAE(upper Zakum,Murban,UM Shaif)

Iran, Kuwait : Ratawai, Egypt( Suez Mix, Zeit mix),

Mediterranean Libya - Es Sider

West Africa Nigeria-Bonny Light, Eseravos, Forcados, Penington,Quaiboe)Angola, -Cabinda, Palanca, Girassol

Eq. Guinea -Ceiba, Zaffiro

Congo -Nikossa, Kitina

Far East Malaysia -Labuan, Miri Light

Australia -Barrow Island, Cooper Basin,Chalis

Brunei -Seria Light

Table M-VI 1.3: Worldwide Crude quality

Properties 1985 1990 1995 1999 2010

Sulphur,Wt % 1.14 1.12 1.31 1.41 1.51

API gravity 32.7 32.6 32.4 32.2 31.8

Residue in crude

,vol %

19 19.4 19.8 20.2 21.3

‘S’ in residue ,Wt%

3.07 3.26 3.61 3.91 4.0

Metals in residue,

 ppm

275 286 297 309 320

Source: Samanti,R.K . “Refining challenges and Trends” 6th summer School on “Petroleum

refining and petrochemicals” June 6, 2012, Organised by New Delhi

Table M-VI 1.4: Characteristics of Various Crude Oil

Sources of indigenouscrude

Salient features

Assam Crude Nahorkatia/

Moran 

31  o

API, Sulphur 0.3%, Pour point +30oC, High

aromatics, Total distillate yield 65%.

ONGC, Lawkwa,

Rudrasagar

27o

API, Sulphur 0.3%, High aromatics, Distillate yield

57%.

Ankleshwar Crude 48oAPI, Sulphur 0.1%, Pour point +18

oC, Distillate

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yield 80-82% (Light distillates 24%, Middle distillate

47%), Wax content 9.9%, total sulphur 0.02%.

North Gujarat Crude 28oAPI, Sulphur content 0.1%, Pour point +27

0C,

Distillate yield low 33-35%, High organic acidity.

Bombay High Crude 38oAPI, Sulphur 0.2%, Pour point +30

oC, Distillate

yield 65-70% (Light distillate 24%, Middle distillates

46%), High aromatics.

Narimanam Crude 46oAPI, Sulphur 0.1%, Pour point 3

oC, Distillate yield

80%.

KG Basin Ravva Crude 36oAPI, Sulphur 0.1%, Pour point +30

oC, Distillate

yield 61%.

Source: Mishra & Unnikrishnan, 1996, p.22

REFINERY PROCESSESRefining of crude oils or petroleum essentially consists of primary separation processes and

secondary conversion processes. The petroleum refining process is the separation of the different

hydrocarbons present in the crude oil into useful fractions and the conversion of some of the

hydrocarbons into products having higher quality performance. Atmospheric and vacuum

distillation of crude oils is the main primary separation processes producing various straight run

 products, e.g., gasoline to lube oils/vacuum gas oils (VGO). These products, particularly the light

and middle distillates, i.e., gasoline, kerosene and diesel are more in demand than their direct

availability from crude oils, all over the world. The typical refinery operation involves separation

 processes, conversion processes, finishing processes, environmental protection processes.

Typical refinery process diagram is shown in Figure M-VI 1.2. 

SEPARATION PROCESSES  Distillation

  Absorption

 

Extraction  Crystallisation

  Adsorption

PRIMARY DISTILATION (Atmospheric Distillation)  Refinery gases  Liquefied petroleum gases

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  Gasolines or naphtha (light/heavy)  Kerosene, lamp oil jet fuel  Diesel oil and domestic heating oils

  Heavy Industrial fuels

SECONDARY DISLLATION (Vacuum Distillation)  Light Distillate

  Middle distillate  Heavy distillate  Asphalt/bitumen

CONVERSION PROCESSES

Process for Improvement of Properties  Catalytic reforming  Isomerisation

 

Alkylation

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Figure M-VI 1.2: Typical Refinery Processes and Products

Thermal processes:

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  Visbreaking  Coking

Catalytic Processes  Catalytic cracking(FCC)

 

Hydrocracking  Steam reforming  Hydroconversion

FINISHING PROCESSES  Hydrotreatment/hydrogenation  Sweetening 

ENVIRONMENTAL PROTECTION PROCESSES  Acid gas processing

  Stack gas processing 

Waste water treatment process

TYPES OF PETROLEUM REFINING PROCESSESPRIMARY PROCESSES: Separating crude into its various fractions e.g. CDU/VDU 

SECONDARY PROCESSES: Processing residues from primary processes and upgrading them

to distillates e.g. FCCU, HCU 

RESIDUE UPGRADATION PROCESSES: Bottom of the barrel upgradation eg. RFCCU,

DCU, DCC

FINISHING/ PRODUCT QUALITY IMPROVEMENT PROCESSES: Processes to improve

 product quality and meet stringent product quality specifications eg. DHDS, DHDT, CRU 

REFINING CAPACITYGlobal oil consumption and refining capacity, World Refining Capacity Country wise 2009 are

given in Table M-VI 1.5 and Figure M-VI 1.3. Present refining capacity in India is million tones

 per annum. The present import of crude in India is around 180 million tones per annum. It is

expected that the import of crude oil has to exceed 240 million tones per annum in the next five

years, if GDP growth of around 6 to 7percent were to be sustained [Venkat, 2012].

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Changing Scenario in Gasoline and Diesel Specifications

Major Parameters of Gasoline Specifications [Table M-VI 1.6]

•  Lead phase out

•  Lower RVP• 

Lower benzene & aromatics

•  Lower olefin content

•  Limited Oxygen content•  Lower Sulfur content

Major Parameters of Diesel Specifications [Table M-VI 1.7]

•  Low sulfur

•  Low aromatics

•  High cetane number

•  Lower density

•  Lower distillation end point

Table M-VI 1.6: Key Specification of Gasoline

Specification BIS

2000

BS-II Euro-III Eqv. Euro-IV Eqv .

Regular Premium Regular Premium

Sulphur,ppmw(max)

1000 500 150 150 50 50

RON,Min 88 88 91 95 91 95

MON,Min No

spec.

 No

spec.

81 85 81 85

AKI,Min 84 84 81 85Benzenevol%(max)

5 3 1 1 1 1

Aromaticsvol%(max)

 Nospec.

 Nospec.

42 42 42 35

Olefinsvol%(max)

 Nospec.

 Nospec.

21 18 21 81

Source: Rajgopal, S. “Refining challenges and Trends.6th

 summer School on “Petroleum refining

and petrochemicals” June 6,2012, Organised by New Delhi

Table M-VI 1.7: Key Specification of High Speed Diesel (HSD)

Specification BIS2000 BS-II Euro-III

Equ.

Euro III

Equiv.

Density@15oC

Kg/m3 

820-860 820-860 820-845 820-845

Sulphur content ppmw(max)

2500 500 350 50

Cetane 48 48 51 51

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number(min)

Distillation

99% Vol (oC

max)

370 370 360 360

Polycyclic

aromaticshydrocarbons

(PAH),%

massmax

 No spec. No spec 11 11

Source: Rajgopal, S. “Refining challenges and Trends.6th

 summer School on “Petroleum refining

and petrochemicals” June 6,2012, Organised by New Delhi

MAXIMIZING VALUE ADDITION TO REFINERY STREAMSFor a refinery to be successful today, it has to be integrated with petrochemical to benefit from

 better realization from value added products and to mitigate the effect of volatile oil process and

highly competitive refining business [Singh and Vaidya, 2012]. Some of the streams which can

maximize value addition to the refinery is given in Table M-VI 1.8.

Table M-VI 1.8: Maximizing Value Addition to Refinery StreamsStreams Utilization

Fuel Gas H2

FCC

Ethylene Ethyl Benzene to Styrene

Propylene Cumene, Iso-Propanol

Butylene Methyl Ethyl Keton, MTBE,

Xylenes

C3  Propylene + H2

C4 Discussed Separately

LPG BTX

C5 TAME

Light naphtha LPG, BTX

Heavy Naphtha Aromatics

Kerosene n-paraffins to LABLCO (FCC unit) Mixed Naphthalenes

Coker Kerosene α-Olefins

Sources: M. O. Garg Director Indian Institute of Petroleum, Dehradun 23 rd National Convention of

Chemical Engineers IIT Roorkee, 5 – 7 October 2007

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