Nht Isom Draft

NHT-ISOM

OPERATING MANUAL FOR

ISOMERISATION UNIT,

VRCFP, HPCL VISAKHDoc No. Draft

Rev. A

Page 1 of 231

OPERATING MANUALOFISOMERISATION UNIT

(UNIT NO.73)

VISAKH REFINERY CLEAN FUELS PROJECT

HINDUSTAN PETROLEUM CORPORATION LIMITED

VISAKH REFINERY

AIssued for commentsNM

Rev No.DatePurposePrepared byChecked byApproved by

PREFACEThis 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.

Table of Contents

6SECTION-1

6INTRODUCTION

61.1INTRODUCTION

8SECTION-2

8DESIGN BASIS

82.1INTRODUCTION

82.2UNIT CAPACITY

82.3ON-STREAM FACTOR

82.4TURNDOWN CAPABILITY

82.5FEED

112.6PRODUCTS

172.7BATTERY LIMIT CONDITIONS

172.8UTILITY CONDITION

21SECTION-3

21CHEMISTRY OF THE PROCESS

213.1INTRODUCTION

213.2ISOMER REACTIONS

253.3ISOMAR CATALYST

273.4Catalyst Contaminants

30SECTION-4

30PROCESS DESCRIPTION

304.1ISOMERIZATION UNIT PROCESS SYSTEM:

344.2Process description

414.3Chloride Injection Facilities

414.4UTILITY SYSTEM

454.5Waste effluent from Isomerization section

47SECTION 5

47PRE-COMMISSIONING PROCEDURE

475.1GENERAL

475.2PRE-COMMISSIONING ACTIVITIES

475.3INSPECTION / CHECKING

495.4PREPARATION FOR PRE-COMMISSIONING

505.5PRE-COMMISSIONING OPERATION

60SECTION 6

60COMMISSIONING PROCEDURE

606.1FIRST START UP

606.2Status of the Unit

606.3Chronology

616.4Complete Inertising

636.5Hydrocarbon Circulation and Initial Dry Down

646.6Hydrogen Sweep

666.7Oil Circulation, and Stabilizer / Deisohexanizer / LPG RECOVERY SECTION Start-up

716.8Reaction Circuit Oil-in

756.9Acidizing and Final Dry-down

816.10Hydrogenation and isomerisation catalyst loading under N2

816.11Hydrogenation reaction section start-UP

846.12Isomerization reaction section start-up

876.13Isomerization Unit Line-Out at Design Capacity

886.14LPG Recovery Section Line-Out

896.15Unit restart

90SECTION 7

90NORMAL OPERATING PROCEDURES

907.1INTRODUCTION

907.2Control philosophy

937.3Operating parameters

957.4OPERATING PARAMETER

1227.5SET POINTS OF ALARMS AND TRIPS

1277.6EQUIPMENT LIST

1367.7LIST OF INSTRUMENTS

1437.8Pressure Safety Valves

1457.9Analyzers

147SECTION - 8

147SHUTDOWN PROCEDURES

1478.1General

1478.2Normal Shutdown Procedure

1488.3Short Duration Shutdowns

1498.4Long Duration Shutdowns

1518.5Shutdown for Catalyst Replacement

1528.6EMERGENCY SHUTDOWN PROCEDURE

1598.7Automatic Shutdowns

163SECTION-9

163PROCESS VARIABLE

1639.1Benzene Saturation

1649.2Isomerization

170SECTION-10

170TROUBLE SHOOTING

17010.1Water BREAKTHROUGH FROM THE DRYERS

17210.2Sulphur Breakthrough: Sulphur Stripping Procedure

17310.3Loss of C2Cl4 Injection

17410.4Chloride Breakthrough

17410.5Preventive Maintenance:

175SECTION 11

175SPECIAL PROCEDURES/INSTRUCTION/INFORMATION

17511.1Catalysts Loading Under N2

18311.2SPENT CATALYST UNLOADING

18411.3Specifications of catalysts

18711.4Chemicals during normal operation

18811.5chemicals during transient opeartion

189SECTION-12

189UTILITY CONSUMPTION SUMMARY

18912.1Intermittent consumptions for Isomerization Section

191SECTION-13

191SAMPLING PROCEDURE AND LABORATORY ANALYSIS REQUIREMENT

19113.1GENERAL

19113.2SAMPLING PROCEDURE

19413.3LABORATORY TEST METHOD AND SCHEDULE

198SECTION -14

198SAFETY PROCEDURE

19814.1INTRODUCTION

19814.2SAFETY OF PERSONNEL

19914.3WORK PERMIT PROCEDURE

20114.4PREPARATION OF EQUIPMENT FOR MAINTENANCE

20314.5PREPARATION FOR VESSEL ENTRY

20914.6HAZARDOUS CHEMICAL HANDLING

21814.7Fire Fighting System

21914.8USE OF LIFE SAVING DEVICE

221SECTION -15

221GENERAL OPERATING INSTRUCTIONS FOR EQUIPMENT

22115.1GENERAL

22115.2CENTRIFUGAL PUMPS

22415.3POSITIVE DISPLACEMENT PUMPS

22615.4CENTRIFUGAL COMPRESSOR

22915.5HEAT EXCHANGERS

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 C5/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 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.

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 FACTORThe 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).

2.5.1. Light Hydrotreated Naphtha

NIT caseAM caseBH case

Molecular weight 83.581.181.3

Sp Gravity @ 15C0.6890.66470.711

Composition, wt%

IBUTANE0.000.000.01

NBUTANE0.000.230.24

IPENTANE8.4810.8911.41

NPENTANE9.5124.0712.32

22DMB0.440.300.52

23DMB1.419.286.83

3METHYLPENTANE7.989.935.36

NHEXANE27.0925.1911.98

CYCLOPENTANE1.151.391.62

METHYLCYCLOPENTANE19.514.267.78

BENZENE4.241.6316.51

CYCLOHEXANE-2.7915.39

NHEPTANE0.729.139.81

METHYLCYCLOHEXAN1.670.460.20

Iso C78.410.000.00

TOLUENE0.010.450.03

C80.140.000.00

Total

100100100

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 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 Sulphur0.5 ppm wt max. (1)

Total Nitrogen compounds0.1 ppm wt max. (1)

Water + Oxygenates0.1 ppm wt max. (1)

Metals5 ppb wt max.

Chloride1 ppm wt max. (1)

Olefins1% wt max.

Arsenic1 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.

Components(Mole %)

OriginCCR Unit

H293.0

C12.3

C22.2

C31.7

iC40.3

nC40.3

C5+0.2

Impurities:

H2S

HCl

CO

COS

CO + CO2H2O

Olefins

N2 compoundsHydrogen 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 Sulphur1.0 ppm wt max.

Total Nitrogen compounds1.0 ppm wt max.

Water0.5 ppm wt max.(1)

CO + CO210 ppm wt max.(1)

Olefins10 ppm wt max.

Chloride5 ppm wt max

(1) At the outlet of the hydrogen dryers.

2.6 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:

SORNIT CASEAM CASEBH CASE

Isomerate Product flowrate, kg/h178592120311961

Sp. Gravity @15C0.64560.64140.6391

Estimated RON88.989.488.5

Estimated MON88.288.386.7

Estimated Yield, wt % (1)65.77844

Estimated RVP, kg/cm2 abs13.5614.916.7

Composition, wt %

PROPANE0.010.020.01

IBUTANE1.41.020.71

NBUTANE0.530.430.39

IPENTANE25.5635.3843.53

NPENTANE8.2810.8216.47

22DMB39.0241.3234.01

23DMB7.253.60.75



NHEXANE0.110.020


METHYCYCLOPENTANE0.050.010

BENZENE000

CYCLOHEXANE000

NHEPATANE000

METHYLCYCLOHEXANE000

11DIMET-CYCLOHEXANE000

Total100100100

EORNIT CASEAM CASEBH CASE


Sp. Gravity @15C0.64480.64010.6366

Estimated RON89.089.488.5

Estimated MON88.288.386.4

Estimated Yield, wt% (1)64.37844


Composition, wt %

PROPANE0.020.030.02

IBUTANE1.661.931.65

NBUTANE0.440.660.69

IPENTANE26.835.7647.24

NPENTANE8.7610.9917

22DMB39.0540.1129.41

23DMB6.873.450.33



NHEXANE0.090.020


METHYCYCLOPENTANE0.0300

BENZENE000

CYCLOHEXANE000

NHEPATANE000

METHYLCYCLOHEXANE000

11DIMET-CYCLOHEXAN000

Total100100100

(1)

Heavy Isomerate Product

SORNIT CASEAM CASEBH CASE


Sp. Gravity @15C0.75620.72430.7402

Estimated Yield, wt % (1)26.313.950.7


Composition, wt %

IBUTANE0.280.340.08

NBUTANE0.10.230.1

IPENTANE0.080.840.94

NPENTANE0.010.070.09

22DMB00.020.03

23DMB0.020.310.62



NHEXANE1.6316.68.56

CYCLOPENTANE000

METHYCYCLOPENTANE7.618.0522.18

BENZENE000

CYCLOHEXANE31.6321.133.84

NHEPATANE18.0223.5211.7

METHYLCYCLOHEXANE23.2412.277.56

11DIMET-CYCLOHEXAN16.9711.217.27

Total100100100

]

EORNIT CASEAM CASEBH CASE


Sp. Gravity @15C0.75420.72520.7408

Estimated Yield, wt % (1)26.813.549.8


Composition, wt %

IBUTANE0.230.350.08

NBUTANE0.150.20.08

IPENTANE1.430.490.67

NPENTANE0.120.040.06

22DMB0.020.020.04

23DMB0.020.310.61



NHEXANE1.5217.438.62

CYCLOPENTANE000

METHYCYCLOPENTANE6.267.3421.48

BENZENE000

CYCLOHEXANE27.2317.8828.79

NHEPATANE17.6121.8511.33

METHYLCYCLOHEXANE26.915.01411.63

11DIMET-CYCLOHEXAN18.1113.419.52

Total100100100

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

SORNIT CaseAM caseBH case

LPG normal flowrate kg/h242723201930

Composition, wt%

H200.010.02

C10.030.580.95

C20.7632.7227.68

C328.5359.7561.38

iC465.336.689.72

nC45.110.240.25

C5+0.2400

Total100.00100.00100.00

Specific gravity @15C0.54480.54320.5456

Yield estimated, wt % (1)8.98.57.1

EORNIT CaseAM caseBH Case

LPG normal flowrate kg/h279425662283

Composition, wt%

H2000

C10.020.010.02

C20.680.590.95

C327.313327.46

iC465.7160.3862.69

nC46.035.778.63

iC50.250.250.24

Total100100100

Specific gravity @15C0.54590.54290.5455

Yield estimated, wt % (1)9.89.08.0

(1)

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

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

SORNIT CaseAM CaseBH Case

Off gas normal flowrate

(kg/h)285261590

Composition, mol %

H283.4986.3369.06

C16.895.1411.39

C25.223.889.78

C33.373.437.43

iC40.30.270.78

nC40.030.070.08

C5+0.70.881.48

H2O000

Total100100100

Molecular Weight6.76.211.2

EORNIT CaseAM CaseBH Case

Off gas normal flowrate

(kg/h)312292647

Composition, mol %

H282.985.4668.19

C16.975.2711.49

C25.313.959.76

C33.654.038.03

iC40.320.330.98

nC40.050.060.07

C5+0.80.91.48

H2O000

Total100100100

Molecular Weight6.96.511.6

2.7 BATTERY LIMIT CONDITIONS

TemperaturePressure

CKg/cm2 g

Feedstock :

Light Naphta feed407.0

H2 make-up4022.0

H2 for start-up 4520.0

10% caustic soda403.0

Products :

LPG4016.0

Light Isomerate407.0

Heavy Isomerate407.0

Sweet Fuel gas 404.5

Spent caustic soda456.0

2.8 UTILITY CONDITION

UTILITY CONDITION AT UNIT BATTERY LIMIT

(All battery limit pressures are measured at grade)

Sr. No.ParameterMinimum (for thermal design)NormalMaximumMech. Design

1HIGH PRESSURE STEAM

Pressure, Kg/cm2g33353840

Temperature, oC340360380400

2MEDIUM PRESSURE STEAM

Pressure, Kg/cm2g9101112.5

Temperature, oCSatd250280300

3LOW PRESSURE STEAM

Pressure, Kg/cm2g2.53.0 4.05.5

Temperature, oCSatd150170190

4STEAM CONDENSATE

Pressure, Kg/cm2g--5.5--10

Temperature, oC--100--185

5COOLING WATER SUPPLY

Pressure, Kg/cm2g--5.3--7.6


6COOLING WATER RETURN



7BOILER FEED WATER ( VHP )

Pressure, Kg/cm2g4750--71

Temperature, oC120120--120

8BOILER FEED WATER ( MP )

Pressure, Kg/cm2g17.520.5--29

Temperature, oC120120--120

9DEMINERALIZED WATER


Temperature, oC--Ambient--65

10PLANT AIR

Pressure, Kg/cm2g3.04.05.09.0


11INSTRUMENT AIR



12NITROGEN



13FUEL OIL SUPPLY

Pressure, Kg/cm2g781117

Temperature, oC100130170200

14FUEL OIL RETURN

Pressure, Kg/cm2g2.5------

Temperature, oC--------

15FUEL GAS


Temperature, 3040-5060100

16FLARE HEADER

Super imposed back pressure at B/L(kg/cm2g)--0.1----

Built up

back pr.

(kg/cm2g)--1.5----

Total back pressure at PSV outlet(kg/cm2g)--1.7----

SECTION-3

CHEMISTRY OF THE PROCESS

2.1 INTRODUCTIONThe 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

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