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OPERATING MANUAL FOR ISOMERISATION UNIT, VRCFP, HPCL VISAKH

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OPERATING MANUAL OF ISOMERISATION UNIT (UNIT NO.73) VISAKH REFINERY CLEAN FUELS PROJECT

HINDUSTAN PETROLEUM CORPORATION LIMITED VISAKH REFINERY

A Rev No.

Date

Issued for comments Purpose

NM Prepared by

Checked by Approved by

PREFACE

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This operating manual for Isomerization Unit of HPCL, VISAKH has been prepared by M/s Engineers India Limited for M/s Hindustan Petroleum Corporation Limited. This manual contains process description and operating guidelines for the unit and is based on documents supplied by the Process Licensor (Axens). Hence the manual must be reviewed /approved by the licensor before the start-up /operation of the unit. Operating procedures & conditions given in this manual are indicative. These should be treated as general guide only for routine start-up and operation of the unit. The actual operating parameters and procedures may require minor modifications/changes from those contained in this manual as more experience is gained in operation of the Plant. For detailed specifications and operating procedures of specific equipment, corresponding Vendor's operating manuals/instructions need to be referred to.

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Table of Contents SECTION-1...................................................................................................................................................6 INTRODUCTION........................................................................................................................................6 1.1

INTRODUCTION............................................................................................................................6

SECTION-2...................................................................................................................................................8 DESIGN BASIS............................................................................................................................................8 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8

INTRODUCTION............................................................................................................................8 UNIT CAPACITY............................................................................................................................8 ON-STREAM FACTOR..................................................................................................................8 TURNDOWN CAPABILITY..........................................................................................................8 FEED................................................................................................................................................8 PRODUCTS...................................................................................................................................11 BATTERY LIMIT CONDITIONS.................................................................................................17 UTILITY CONDITION.................................................................................................................17

SECTION-3.................................................................................................................................................21 CHEMISTRY OF THE PROCESS...........................................................................................................21 3.1 3.2 3.3 3.4

INTRODUCTION..........................................................................................................................21 ISOMER REACTIONS.................................................................................................................21 ISOMAR CATALYST....................................................................................................................25 CATALYST CONTAMINANTS....................................................................................................27

SECTION-4.................................................................................................................................................30 PROCESS DESCRIPTION.......................................................................................................................30 4.1 4.2 4.3 4.4 4.5

ISOMERIZATION UNIT PROCESS SYSTEM:..........................................................................30 PROCESS DESCRIPTION............................................................................................................34 CHLORIDE INJECTION FACILITIES........................................................................................41 UTILITY SYSTEM........................................................................................................................41 WASTE EFFLUENT FROM ISOMERIZATION SECTION........................................................45

SECTION – 5..............................................................................................................................................47 PRE-COMMISSIONING PROCEDURE................................................................................................47 5.1 5.2 5.3 5.4 5.5

GENERAL.....................................................................................................................................47 PRE-COMMISSIONING ACTIVITIES........................................................................................47 INSPECTION / CHECKING.........................................................................................................47 PREPARATION FOR PRE-COMMISSIONING..........................................................................49 PRE-COMMISSIONING OPERATION.......................................................................................50

SECTION – 6..............................................................................................................................................60 COMMISSIONING PROCEDURE.........................................................................................................60 6.1 6.2

FIRST START UP..........................................................................................................................60 STATUS OF THE UNIT................................................................................................................60

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CHRONOLOGY............................................................................................................................60 COMPLETE INERTISING............................................................................................................61 HYDROCARBON CIRCULATION AND INITIAL DRY DOWN..............................................63 HYDROGEN SWEEP...................................................................................................................64 OIL CIRCULATION, AND STABILIZER / DEISOHEXANIZER / LPG RECOVERY SECTION START-UP....................................................................................................................66 REACTION CIRCUIT OIL-IN......................................................................................................71 ACIDIZING AND FINAL DRY-DOWN.......................................................................................75 HYDROGENATION AND ISOMERISATION CATALYST LOADING UNDER N2............81 HYDROGENATION REACTION SECTION START-UP......................................................81 ISOMERIZATION REACTION SECTION START-UP..........................................................84 ISOMERIZATION UNIT LINE-OUT AT DESIGN CAPACITY............................................87 LPG RECOVERY SECTION LINE-OUT................................................................................88 UNIT RESTART.......................................................................................................................89

SECTION –7...............................................................................................................................................90 NORMAL OPERATING PROCEDURES...............................................................................................90 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9

INTRODUCTION..........................................................................................................................90 CONTROL PHILOSOPHY...........................................................................................................90 OPERATING PARAMETERS.......................................................................................................93 OPERATING PARAMETER.........................................................................................................95 SET POINTS OF ALARMS AND TRIPS...................................................................................122 EQUIPMENT LIST.....................................................................................................................127 LIST OF INSTRUMENTS..........................................................................................................136 PRESSURE SAFETY VALVES..................................................................................................143 ANALYZERS...............................................................................................................................145

SECTION - 8.............................................................................................................................................147 SHUTDOWN PROCEDURES................................................................................................................147 8.1 8.2 8.3 8.4 8.5 8.6 8.7

GENERAL...................................................................................................................................147 NORMAL SHUTDOWN PROCEDURE....................................................................................147 SHORT DURATION SHUTDOWNS..........................................................................................148 LONG DURATION SHUTDOWNS...........................................................................................149 SHUTDOWN FOR CATALYST REPLACEMENT...................................................................151 EMERGENCY SHUTDOWN PROCEDURE............................................................................152 AUTOMATIC SHUTDOWNS....................................................................................................159

SECTION-9...............................................................................................................................................163 PROCESS VARIABLE............................................................................................................................163 9.1 9.2

BENZENE SATURATION..........................................................................................................163 ISOMERIZATION.......................................................................................................................164

SECTION-10.............................................................................................................................................170 TROUBLE SHOOTING..........................................................................................................................170 10.1 10.2 10.3 10.4 10.5

WATER BREAKTHROUGH FROM THE DRYERS............................................................170 SULPHUR BREAKTHROUGH: SULPHUR STRIPPING PROCEDURE..........................172 LOSS OF C2CL4 INJECTION.................................................................................................173 CHLORIDE BREAKTHROUGH...........................................................................................174 PREVENTIVE MAINTENANCE:.........................................................................................174

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SECTION -11............................................................................................................................................175 SPECIAL PROCEDURES/INSTRUCTION/INFORMATION...........................................................175 11.1 11.2 11.3 11.4 11.5

CATALYSTS LOADING UNDER N2....................................................................................175 SPENT CATALYST UNLOADING.......................................................................................183 SPECIFICATIONS OF CATALYSTS.....................................................................................184 CHEMICALS DURING NORMAL OPERATION................................................................187 CHEMICALS DURING TRANSIENT OPEARTION...........................................................188

SECTION-12.............................................................................................................................................189 UTILITY CONSUMPTION SUMMARY..............................................................................................189 12.1

INTERMITTENT CONSUMPTIONS FOR ISOMERIZATION SECTION.........................189

SECTION-13.............................................................................................................................................191 SAMPLING PROCEDURE AND LABORATORY ANALYSIS REQUIREMENT..........................191 13.1 13.2 13.3

GENERAL..............................................................................................................................191 SAMPLING PROCEDURE....................................................................................................191 LABORATORY TEST METHOD AND SCHEDULE...........................................................194

SECTION -14............................................................................................................................................198 SAFETY PROCEDURE..........................................................................................................................198 14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8

INTRODUCTION...................................................................................................................198 SAFETY OF PERSONNEL....................................................................................................198 WORK PERMIT PROCEDURE.............................................................................................199 PREPARATION OF EQUIPMENT FOR MAINTENANCE.................................................201 PREPARATION FOR VESSEL ENTRY................................................................................203 HAZARDOUS CHEMICAL HANDLING.............................................................................209 FIRE FIGHTING SYSTEM....................................................................................................218 USE OF LIFE SAVING DEVICE...........................................................................................219

SECTION -15............................................................................................................................................221 GENERAL OPERATING INSTRUCTIONS FOR EQUIPMENT.....................................................221 15.1 15.2 15.3 15.4 15.5

GENERAL..............................................................................................................................221 CENTRIFUGAL PUMPS.......................................................................................................221 POSITIVE DISPLACEMENT PUMPS..................................................................................224 CENTRIFUGAL COMPRESSOR..........................................................................................226 HEAT EXCHANGERS...........................................................................................................229

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SECTION-1 INTRODUCTION 1.1

INTRODUCTION

Isomerization is the conversion of low octane straight chain compounds to their higher octane branched isomers. The purpose of this process is to saturate benzene and to isomerise normal paraffins to improve the research and motor octane number of the light naphtha feed (predominantly C5/C6) before blending into the gasoline pool. The light naphtha fraction is typically high in normal isomer content resulting in a low octane number (typically < 68). The isomerization process converts an equilibrium proportion of these low octane normal isomers into their higher octane branched isomers. This process developed and licensed by Axens consists of three fixed bed adiabatic reactors, with benzene saturation carried out in the first reactor, and C 5/C6 isomerization reactions completed in the following two reactors. The isomerization reactions are carried over a fixed chlorinated platinum catalyst bed in a hydrogen environment. Operating conditions are not severe as reflected by moderate operating pressure, low temperature, low hydrogen partial pressure and high catalyst space velocity. These operating conditions promote the isomerization reaction, minimize hydrocracking and minimize equipment capital costs. The feedstock of the Isomerization unit is light hydrotreated naphtha coming from Naphtha Hydrotreating Unit. Naphtha is mixed with hydrogen. A small amount of chlorinating agent is continuously injected in to the isomerization catalyst. The mixture enters in first stage reactor where isomerization reaction occurs. The effluent is cooled before entering the second stage reactor. Remaining isomerization reaction occurs in third stage reactor. The effluent is then routed to stabilizer to reduce C4 rate in the isomerization reactor effluent. The stabilizer overhead is partially cooled and vapor phase is routed to LPG recovery section while liquid is used as reflux. Stabilizer bottom

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is routed to deisohexaniser where low octane C6- n paraffin and methyl pentane is recycled to the reactor circuit in order to obtain a high octane product.

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SECTION-2 DESIGN BASIS 2.1

INTRODUCTION

The isomer unit is required to produce an Isomerate product which is suitable for gasoline pool. Important content of design basis is given below. 2.2

UNIT CAPACITY

Isomar Unit is designed for a capacity of 228641 T/yr. 2.3

ON-STREAM FACTOR

The facility is designed for 8000 operating hours per year. 2.4

TURNDOWN CAPABILITY

The facility is capable of operating at 50 percent of design feed capacity, while maintaining the designated product specification. 2.5

FEED

The feedstock of the Isomerization unit is light hydrotreated naphtha coming from Naphtha Hydrotreating Unit. Three different feeds were considered for the design of the unit NIT CASE, AM CASE (Arabian Mixed) and BH CASE (Bombay High).

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2.5.1. Light Hydrotreated Naphtha NIT case

AM case

BH case

Molecular weight

83.5

81.1

81.3

Sp Gravity @ 15°C

0.689

0.6647

0.711

Composition, wt% IBUTANE NBUTANE IPENTANE NPENTANE 22DMB 23DMB 3METHYLPENTANE NHEXANE CYCLOPENTANE METHYLCYCLOPENTANE BENZENE CYCLOHEXANE NHEPTANE METHYLCYCLOHEXAN Iso C7 TOLUENE

0.00 0.00 8.48 9.51 0.44 1.41 7.98 27.09 1.15 19.51 4.24 0.72 1.67 8.41 0.01

0.00 0.23 10.89 24.07 0.30 9.28 9.93 25.19 1.39 4.26 1.63 2.79 9.13 0.46 0.00 0.45

0.01 0.24 11.41 12.32 0.52 6.83 5.36 11.98 1.62 7.78 16.51 15.39 9.81 0.20 0.00 0.03

C8

0.14

0.00

0.00

100

100

Total

100

Impurities: The Isomerization catalyst is an activated chloride, alumina based catalyst with a platinum promoter. It is highly sensitive to impurities in the feedstock, in particular water or other oxygenated compounds. Feed to this unit is hydrotreated and both feed and make-up hydrogen are passed through dryers to remove any traces of water. Some

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impurities are considered to be irreversible poisons such as water and nitrogen compounds. Others are reversible such as sulfur. It is critically important that the operating performances of both upstream hydrotreater and dryers are such that the impurity levels in the isomerization reactor feed do not exceed the levels shown hereafter. Discussions regarding feed poisons and their effects will be presented in the Operating Instructions Section. MAXIMUM ALLOWABLE IMPURITY LEVELS IN THE FEED Total Sulphur 0.5 ppm wt max. (1) Total Nitrogen compounds 0.1 ppm wt max. (1) Water + Oxygenates 0.1 ppm wt max. (1) Metals 5 ppb wt max. Chloride 1 ppm wt max. (1) Olefins 1% wt max. Arsenic 1 ppb wt max. (1) At the outlet of the feed dryer. 2.5.2. Hydrogen Hydrogen make-up to this unit is needed for isomerization unit for benzene hydrogenation to cyclohexane and in order to satisfy the hydrogen partial pressure requirement for the naphtha hydrotreatment and for the isomerization reactions. Hydrogen is supplied from a new CCR unit. A gas compressor is required to satisfy the process requirements of the different users.

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Components

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(Mole %)

Origin

CCR Unit

H2

93.0

C1

2.3

C2

2.2

C3

1.7

iC4

0.3

nC4

0.3

C5+

0.2

Impurities: H2S HCl CO COS CO + CO2 H2O Olefins N2 compounds

Hydrogen quality

5 ppm vol max 0.5 ppm vol max 6-10 ppm vol 1 ppm vol max 25 ppm vol max 50 vol ppm 10 ppm wt max 1 wt ppm max MAXIMUM ALLOWABLE CONTAMINANT LEVELS FOR HYDROGEN TO ISOMERIZATION UNIT Total Sulphur Total Nitrogen compounds Water CO + CO2 Olefins Chloride

1.0 ppm wt max. 1.0 ppm wt max. 0.5 ppm wt max.(1) 10 ppm wt max.(1) 10 ppm wt max. 5 ppm wt max

(1) At the outlet of the hydrogen dryers.

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PRODUCTS

There are four products. The primary product is light Isomerate i.e. deisohexaniser distillate. The secondary product is heavy Isomerate, i.e. deisohexaniser bottom. The third product Fuel gas comes from LPG separator drum. The fourth product is LPG stream produced isomerization stabilizer overhead.



Light Isomerate product

The light isomerate product estimated flowrates and product characteristics are presented hereafter: SOR Isomerate Product flowrate, kg/h Sp. Gravity @15°C Estimated RON Estimated MON Estimated Yield, wt % (1) Estimated RVP, kg/cm2 abs Composition, wt % PROPANE IBUTANE NBUTANE IPENTANE NPENTANE 22DMB 23DMB 2METHYLPENTANE 3METHYLPENTANE NHEXANE CYCLOPENTANE METHYCYCLOPENTANE BENZENE CYCLOHEXANE NHEPATANE

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NIT CASE 17859 0.6456 88.9 88.2 65.7 13.56

AM CASE 21203 0.6414 89.4 88.3 78 14.9

BH CASE 11961 0.6391 88.5 86.7 44 16.7

0.01 1.4 0.53 25.56 8.28 39.02 7.25 13.73 2.51 0.11 1.55 0.05 0 0 0

0.02 1.02 0.43 35.38 10.82 41.32 3.6 5.22 0.71 0.02 1.45 0.01 0 0 0

0.01 0.71 0.39 43.53 16.47 34.01 0.75 0.71 0.07 0 3.35 0 0 0 0

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OPERATING MANUAL FOR ISOMERISATION UNIT, VRCFP, HPCL VISAKH SOR METHYLCYCLOHEXANE 11DIMET-CYCLOHEXANE Total

Yield 

LightIsomerate Freshfeed

NIT CASE 0 0 100

EOR Isomerate Product flowrate, kg/h Sp. Gravity @15°C Estimated RON Estimated MON Estimated Yield, wt% (1) Estimated RVP, kg/cm2 abs Composition, wt % PROPANE IBUTANE NBUTANE IPENTANE NPENTANE 22DMB 23DMB 2METHYLPENTANE 3METHYLPENTANE NHEXANE CYCLOPENTANE METHYCYCLOPENTANE BENZENE CYCLOHEXANE NHEPATANE METHYLCYCLOHEXANE 11DIMET-CYCLOHEXAN Total

(1)



Yield 

LightIsomerate Freshfeed

Page 13 of 221

AM CASE 0 0 100

BH CASE 0 0 100

NIT CASE

AM CASE

BH CASE

18377 0.6448 89.0 88.2 64.3

22292

12575

0.6401 89.4 88.3 78

0.6366 88.5 86.4 44

13.98

15.80

17.3

0.02 1.66 0.44 26.8 8.76 39.05 6.87 1.54 2.16 0.09 1.58 0.03 0 0 0 0 0 100

0.03 1.93 0.66 35.76 10.99 40.11 3.45 4.95 0.67 0.02 1.43 0 0 0 0 0 0 100

0.02 1.65 0.69 47.24 17 29.41 0.33 0.31 0.03 0 3.32 0 0 0 0 0 0 100

flowrate (kg / h) flowrate (kg / h)

Rev. A

* 100

flowrate ( kg / h) flowrate (kg / h)

* 100

Heavy Isomerate Product

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SOR Isomerate Product flowrate, kg/h Sp. Gravity @15°C Estimated Yield, wt % (1) Estimated RVP, kg/cm2 abs Composition, wt % IBUTANE NBUTANE IPENTANE NPENTANE 22DMB 23DMB 2METHYLPENTANE 3METHYLPENTANE NHEXANE CYCLOPENTANE METHYCYCLOPENTANE BENZENE CYCLOHEXANE NHEPATANE METHYLCYCLOHEXANE 11DIMET-CYCLOHEXAN Total Yield 

HeavyIsomerate Freshfeed

EOR Isomerate Product flowrate, kg/h Sp. Gravity @15°C Estimated Yield, wt % (1) Estimated RVP, kg/cm2 abs Composition, wt % IBUTANE NBUTANE IPENTANE NPENTANE 22DMB 23DMB 2METHYLPENTANE 3METHYLPENTANE

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NIT CASE 7148 0.7562 26.3 3.31

AM CASE 3791 0.7243 13.9 4.3

BH CASE 13788 0.7402 50.7 4.4

0.28 0.1 0.08 0.01 0 0.02 0.1 0.3 1.63 0 7.61 0 31.63 18.02 23.24 16.97 100

0.34 0.23 0.84 0.07 0.02 0.31 1.7 3.75 16.6 0 8.05 0 21.1 23.52 12.27 11.21 100

0.08 0.1 0.94 0.09 0.03 0.62 2.72 4.32 8.56 0 22.18 0 33.84 11.7 7.56 7.27 100

flowrate ( kg / h) flowrate (kg / h)

Rev. A

*100 ]

NIT CASE

AM CASE

BH CASE

7669 0.7542 26.8 3.58

3857

14239

0.7252 13.5 4.1

0.7408 49.8 4.2

0.23 0.15 1.43 0.12 0.02 0.02 0.1 0.29

0.35 0.2 0.49 0.04 0.02 0.31 1.77 3.9

0.08 0.08 0.67 0.06 0.04 0.61 2.72 4.37

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OPERATING MANUAL FOR ISOMERISATION UNIT, VRCFP, HPCL VISAKH NHEXANE CYCLOPENTANE METHYCYCLOPENTANE BENZENE CYCLOHEXANE NHEPATANE METHYLCYCLOHEXANE 11DIMET-CYCLOHEXAN Total



1.52 0 6.26 0 27.23 17.61 26.9 18.11 100

Rev. A Page 15 of 221

17.43 0 7.34 0 17.88 21.85 15.014 13.41 100

8.62 0 21.48 0 28.79 11.33 11.63 9.52 100

LPG Product

LPG is recovered at LPG stripper 73-C-04 draw-off. Estimated flowrates and compositions are presented hereafter. SOR

NIT Case

AM case

BH case

LPG normal flowrate kg/h Composition, wt% H2 C1 C2 C3 iC4 nC4 C5+ Total

2427

2320

1930

0 0.03 0.76 28.53 65.33 5.11 0.24 100.00

0.01 0.58 32.72 59.75 6.68 0.24 0 100.00

0.02 0.95 27.68 61.38 9.72 0.25 0 100.00

Specific gravity @15°C

0.5448

0.5432

0.5456

Yield estimated, wt % (1)

8.9

8.5

7.1

EOR

NIT Case

AM case

BH Case

LPG normal flowrate kg/h Composition, wt% H2 C1 C2 C3 iC4 nC4 iC5 Total Specific gravity @15°C Yield estimated, wt % (1)

2794

2566

2283

0 0.02 0.68 27.31 65.71 6.03 0.25 100 0.5459 9.8

0 0.01 0.59 33 60.38 5.77 0.25 100 0.5429 9.0

0 0.02 0.95 27.46 62.69 8.63 0.24 100 0.5455 8.0

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Yield 

(1) Note: 

LPG

flowrate ( kg / h)

NHDT  Feed

flowrate ( kg / h)

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* 100

LPG flowrates described here above take into account the LPG stream coming from reforming unit.

Fuel gas

Fuel gas is recovered at caustic scrubber 73-V-11. Estimated flowrates and compositions are presented hereafter:

SOR Off gas normal flowrate (kg/h) Composition, mol % H2 C1 C2 C3 iC4 nC4 C5+ H2O Total Molecular Weight

EOR Off gas normal flowrate (kg/h) Composition, mol % H2 C1 C2 C3 iC4 nC4 C5+ H2O Total Molecular Weight

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NIT Case

AM Case

BH Case

285

261

590

83.49 6.89 5.22 3.37 0.3 0.03 0.7 0 100 6.7

86.33 5.14 3.88 3.43 0.27 0.07 0.88 0 100 6.2

69.06 11.39 9.78 7.43 0.78 0.08 1.48 0 100 11.2

NIT Case

AM Case

BH Case

312

292

647

82.9 6.97 5.31 3.65 0.32 0.05 0.8 0 100 6.9

85.46 5.27 3.95 4.03 0.33 0.06 0.9 0 100 6.5

68.19 11.49 9.76 8.03 0.98 0.07 1.48 0 100 11.6

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BATTERY LIMIT CONDITIONS Temperature

Pressure

°C

Kg/cm2 g

 Feedstock : o

Light Naphta feed

40

7.0

o

H2 make-up

40

22.0

o

H2 for start-up

45

20.0

o

10% caustic soda

40

3.0

 Products :

2.8

o

LPG

40

16.0

o

Light Isomerate

40

7.0

o

Heavy Isomerate

40

7.0

o

Sweet Fuel gas

40

4.5

o

Spent caustic soda

45

6.0

UTILITY CONDITION UTILITY CONDITION AT UNIT BATTERY LIMIT (All battery limit pressures are measured at grade)

Sr. No.

Minimum (for

Parameter

thermal design)

1

Normal

Maximum

Mech. Design

HIGH PRESSURE STEAM 2

Pressure, Kg/cm g

33

35

38

40

Temperature, oC

340

360

380

400

2

MEDIUM PRESSURE STEAM Pressure, Kg/cm2g Temperature, oC

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9

10

11

12.5

Satd

250

280

300

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Sr. No.

Minimum (for

Parameter

thermal design)

3

Rev. A Page 18 of 221

Normal

Maximum

Mech. Design

LOW PRESSURE STEAM 2

Pressure, Kg/cm g

2.5

3.0

4.0

5.5

Temperature, oC

Satd

150

170

190

4

STEAM CONDENSATE Pressure, Kg/cm2g

--

5.5

--

10

Temperature, oC

--

100

--

185

5

COOLING WATER SUPPLY Pressure, Kg/cm2g

--

5.3

--

7.6

Temperature, oC

--

33

--

65

6

COOLING WATER RETURN Pressure, Kg/cm2g

--

3.5

--

7.6

Temperature, oC

--

44

--

65

7

BOILER FEED WATER ( VHP ) Pressure, Kg/cm2g

47

50

--

71

Temperature, oC

120

120

--

120

8

BOILER FEED WATER ( MP ) Pressure, Kg/cm2g Temperature, oC

9

17.5

20.5

--

29

120

120

--

120

DEMINERALIZED WATER Pressure, Kg/cm2g

--

3.0

--

9.0

Temperature, oC

--

Ambient

--

65

10

PLANT AIR Pressure, Kg/cm2g

3.0

4.0

5.0

9.0

Temperature, oC

--

Ambient

--

65

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Minimum (for

Parameter

thermal design)

11

Normal

Rev. A Page 19 of 221

Maximum

Mech. Design

INSTRUMENT AIR 2

Pressure, Kg/cm g

4.0

5.0

6.0

9.0

Temperature, oC

--

Ambient

--

65

12

NITROGEN 2

Pressure, Kg/cm g

5.0

6.0

7.0

10.5

Temperature, oC

--

Ambient

--

65

13

FUEL OIL SUPPLY Pressure, Kg/cm2g Temperature, oC

14

7

8

11

17

100

130

170

200

FUEL OIL RETURN Pressure, Kg/cm2g

2.5

--

--

--

Temperature, oC

--

--

--

--

15

FUEL GAS Pressure, Kg/cm2g

2.5

3.0

3.5

9.0

Temperature,

30

40-50

60

100

16

FLARE HEADER Super imposed back pressure at B/L(kg/cm2g) Built up back pr. (kg/cm2g) Total back pressure at PSV

--

0.1

--

--

--

1.5

--

--

--

1.7

--

--

outlet(kg/cm2g)

Template No. 5-0000-0001-T2 Rev A

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Doc No. Draft

OPERATING MANUAL FOR ISOMERISATION UNIT, VRCFP, HPCL VISAKH

Rev. A Page 20 of 221

SECTION-3 CHEMISTRY OF THE PROCESS 3.1

INTRODUCTION

The main purpose of this process is to saturate benzene and to isomerise normal paraffins to improve the research and motor octane number of the light naphtha feed (predominantly C5/C6) before blending into gasoline pool. The light naphtha fraction is typically high in normal isomer content resulting in a low octane number (typically