Course: Chemical Technology (Organic) Module VI

Lecture 1

Introduction: Status of Petroleum 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 hydrocarbons

Remarks

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+2-2Rn RN 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 around linkage.

Benzene, Toluene, Xylene, Ethyl Benzene, Cumene, Naphthaline

Aromatics are not desirable in kerosene and lubricating oil. Benzene is carcinogenic and hence undesirable 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 indigenous crude

Salient features

Assam Crude Nahorkatia/ Moran

31 oAPI, Sulphur 0.3%, Pour point +30 oC, High aromatics, Total distillate yield 65%.

ONGC, Lawkwa, Rudrasagar

27 o API, Sulphur 0.3%, High aromatics, Distillate yield 57%.

Ankleshwar Crude 48 oAPI, 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 28 oAPI, Sulphur content 0.1%, Pour point +27 0C, Distillate yield low 33-35%, High organic acidity.

Bombay High Crude 38 oAPI, Sulphur 0.2%, Pour point +30 oC, Distillate yield 65-70% (Light distillate 24%, Middle distillates 46%), High aromatics.

Narimanam Crude 46 oAPI, Sulphur 0.1%, Pour point 3 oC, Distillate yield 80%.

KG Basin Ravva Crude 36 oAPI, Sulphur 0.1%, Pour point +30 oC, Distillate yield 61%.

Source: Mishra & Unnikrishnan, 1996, p.22

REFINERY PROCESSES Refining 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 PROCESSES PRIMARY 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 CAPACITY Global 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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Table M-VI 1.5: Global Oil Consumption and Refining Capacity 2009 million barrel/d Region Oil consumption Refining

capacity Remarks

Asia Pacific 25.99 26.81 Just matching North america 22.83 21.13 Deficit Europe and Eurasia

19.37 24.92 Surplus

S & cent .America

5.65 6.69 Surplus

Middle east 7.15 7.86 Surplus Africa 3.08 3.26 Surplus Total 84.04 90.66 Surplus Source: Samanti,R.K. “Refining challenges and Trends.6th Summer School on “ Petroleum refining and petrochemicals” June 6,2011, Organised by New Delhi

 Figure M-VI 1.3: World Refining Capacity Country wise 2009

Total: 90.7 mbpd (4533 MMTPA) Sources: Mr. R.K. Samtani, DGM (Exploration & Production) IOC ltd. 6th June 2011  

USA, 19%

CHINA, 10%

RUSSIAN FED., 6% JAPAN, 5%

S. KOREA, 3%

INDIA, 4%

ITALY, 3%

S. ARABIA, 2%

GERMANY, 3%

OTHERS , 45%

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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 85 Benzene vol%(max)

5 3 1 1 1 1

Aromatics vol%(max)

No spec.

No spec.

42 42 42 35

Olefins vol%(max)

No spec.

No spec.

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 aromatics hydrocarbons (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 STREAMS For 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 Streams Streams 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 LAB LCO (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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REFERENCE

1. Garg, M. O., Invited talk 23 rd National Convention of Chemical Engineers IIT Roorkee, 5 –

7 October 2007

2. Mishra, A.K, Unnikrishnan, A., “Overview of the quality of crude oils processed in India”

1996, p.22 Challenges in crude oil evaluation: edt. Nagpal, J.M., New Delhi, Tata McGraw-

Hill Publishing Company Ltd, 1996, p. 1.

3. Mukhulyonov, I.U., Kuznetsov, D., Averbukh, A., Tumarkina, E., Furmer “Chemical

Technology” Mir Publishers Moscow,1974

4. Rajgopal, S., “Petroleum refining and petrochemicals” Refining challenges and Trends 6th

summer School on June 6,2012, Organised by New Delhi

5. Ravindranath,K., Habubula,M. “Hydro carbon condensate Fractionation in oil and gas

processing complex”, Chemical Engineering world, Vol 27, No.10, 1992, p.43

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

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

7. Samtani R.K., DGM (Exploration & Production) IOC ltd. 6th June 2011

8. Singh, S., Vaidya,S.M., “The benefits from refinery and petrochemical Integration”

Chemical Industry digest August 2012,p67

9. Speight J.G. “The chemistry and technology of Petroleum”, Marccel Decker, Inc, New York,

1999.

10. Venkatraman, N.S., “Algae biofuel could be India’s savior” chemical News July, 2012, p.40