Vocational Training Report

Vocational Training Report | Indian Oil Corporation, Gujarat Refinery 1

VOCATIONAL TRAINING REPORT

AT

INDIAN OIL CORPORATION LTD

GUJARAT REFINERY

(JUNE-JULY 2012)

PREPARED BY:

ASHISH RAJESHBHAI KAVAIYA Roll Number :- U10CH010

(B-TECH-II IN CHEMICAL ENGINEERING)

SARDAR VALLABHBHAI NATIONAL INSTITUTE OF

TECHNOLOGY, SURAT


PREFACE

India has definitely become a strong country as far as the

petrochemical industry is concerned. India has undoubtedly strengthened

its position in the international market by roping in foreign investment

and trying to establish its strong abroad. In the present area, it has

become necessary to compete on the global stage.

It is equally important to have practical as well as theoretical

knowledge. Theoretical knowledge can be easily acquired from books

and publications, but one has to pass through an on-site training phase

for practical knowledge.

Having said this, one has to observe and study the equipments used

for the process, its construction, start up and shut down procedures,

operating problems, its solution, emergencies, etc. The theories and

usual practices cited in books and literature differ up to an appreciable

extent from the industrial practices.

Another attractive feature is to learn industrial management and

discipline, which is equally important in life.

This is only possible in an industrial training.

In short, the in-plant training makes a better engineer and a better

manager who can serve the industry with best of his ability.


ACKNOWLEDGEMENT

The summer training at Indian Oil Corporation Ltd., Gujarat Refinery was a

wonderful experience. Whatever I learnt during the training has been brought out

in the form of this training report. I, hereby take the opportunity to thank all the

people who have imparted their invaluable knowledge to me.

I bestow my gratitude to Mr. PK Sahai,Dy Manager (Trg. & Dev.),

Mr.C.P.AMBEDKAR, Sr. Officer(Trg. & Dev.) and Mr. N.H.PATEL for granting me the permission to obtain training at Indian Oil Corporation Ltd, Gujarat Refinery.

I am thankful to Mr.P.V.Solanki, Chief Production Manager

(CPNM),Gujarat Refinery, my industry mentor, for continuously guiding and

encouraging me at each step of my training. He not only solved my difficulties, but

also shared his immense experience of his service in the industry. This was the

most valuable thing I earned at Indian Oil Corporation Ltd., Gujarat Refinery. My

training would have been remained incomplete without my mentor.

I wish to warmly thank Mr.AB Damor Production Manager(GHC),Mr.K

M Taboli Production Manger(GR-1),Mr. A K Roy Production Manger(

LAB/MSQU) and Mr. S.BOSE, Production Manager (GRE) for their consistent

guidance and support in their respective units throughout my training and for

constantly ensuring that the training is opening up new aspects of chemical

industry for my learning.

I am highly indebted to Dr. Z.V.P MURTHY (Head of Department,

Chemical Engineering, SVNIT) for deputing me to Indian Oil Corporation Ltd.

for training.

I, finally, would like to thank all the staff and officials of Indian oil

Corporation Ltd., Gujarat Refinery for all the help they provided during the

training.


CONTENTS

1. Indian Oil Corporation Ltd. (IOCL) Overview ............5

Company Profile ..5

Refineries .............6

Corporate Mission ...........6

Business Activities/Objectives ............7 2. Vision .8 3. Expertise available with Indian Oil ..............10 4. Gujarat Refinery ....13

Introduction .............13

History .............14

Technology Leader ..15

Crude Processing .............15

Product and End Uses ..15 5. Important Units of Gujarat Refinery ............17 6. Gujarat Refinery Expansion Unit (GRE) ..18

Crude Distillation Unit (CDU) ..................19

Vacuum Distillation Unit (VDU) ..................26

Vis-breaker Unit (VBU) .....33

Bitumen Blowing Unit (BBU) ...................39 7. Gujarat Refinery Secomdary Processing Facilities....45

Feed preparation Unit .46

Fluidized Catalytic Cracking...47 8. Gujarat Hydro Cracker Unit ...54

Hydrogen Unit..55

Hydro Cracker Unit..60 9. Motor Spirit Quality Upgradation Unit........69 10. Catalytic Reforming Unit.82 11. General Safety Regulations .89


INDIAN OIL CORPORATION LTD

Company Profile

Indian Oil Corporation Ltd., is an Indian public-sector oil and gas company. It began its

operation in 1959 as Indian Oil Company Ltd. The Indian Oil Corporation Ltd was formed in

1964, with the merger of Indian Refineries Ltd. (established in 1958).

It is Indias largest commercial enterprise, with a sales turnover of Rs.2,85,337 crore, the highest ever for an Indian company, for the year 2008-09. Indian Oil is also the highest ranked Indian

company in the prestigious Fortune Global 500 listing, having ranked 105th in 2009. It is also the 18

th largest petroleum company in the world.

Indian Oil and its subsidiary account for approximately 48% petroleum products market share,

34% national refining capacity and 71% downstream sector pipelines capacity in India. The

Indian Oil Group of companies owns and operates 10 of Indias 20 refineries with a combined refining capacity of 60.2 million metric tones per annum. These include two refineries of

subsidiary Chennai Petroleum Corporation Ltd. (CPCL).

The Corporations cross-country network of crude oil and product pipelines, spanning more than 10,000 kms and the largest in the country, meets the vital energy needs of the consumers in an

efficient, economical and environment-friendly manner. As the flagship national oil company in

the downstream sector, Indian Oil reaches precious petroleum products to millions of people

every day through a countrywide network of about 35,000 sales points.

Indian Oil operates the largest and the widest network of petrol and diesel stations in the country,

numbering over 18,278. It reaches Indane cooking gas to the doorsteps of over 53 million

households in

nearly 2,700 markets through a network of about 5,000 Indane distributors.

Indian Oils ISO-9002 certified Aviation Service commands over 63% market share in aviation fuel business, meeting the fuel needs of domestic and international flag carriers, private airlines

and the Indian Defense Services. The Corporation also enjoys a dominant share of the bulk

consumer business, including that of railways, state transport undertakings, and industrial,

agricultural and marine sectors.


Refineries :

Digboi Refinery, in Assam is Indias oldest refinery and was commissioned in 1901. Originally a part of Assam Oil Company, it became a part of Indian Oil in 1981. Its

original refining capacity had been 0.5 MMTPA (million metric tones per annum) since

1901. Modernization project of this refinery has been completed and the refinery now has

an increased capacity of 0.65 MMTPA.

Guwahati Refinery, the first public sector refinery of the country, was built with Romanian collaboration and was inaugurated by Late Pt. Jawaharlal Nehru, the first

Prime Minister of India, on 1st January 1962.

Barauni Refinery, in Bihar, was built in collaboration with Russia and Romania. It was commissioned in 1964 with a capacity of 1.0 MMTPA. Its capacity today is 6.0 MMTPA.

Gujarat Refinery, at Koyali in Vadodara, Gujarat, is Indian Oils largest refinery. The refinery was commissioned in 1965. It also houses the first hydrocracking unit of the

country. Its present capacity is 13.70 MMTPA.

Haldia Refinery is the only coastal refinery of the Corporation, situated 136 kms downstream of Kolkata in the East Midnapore district. It was commissioned in 1975 with

a capacity of 2.5 MMTPA, which has since been increased to 5.8 MMTPA.

Mathura Refinery was commissioned in 1982 as the sixth refinery in the fold of Indian Oil and with an original capacity of 6.0 MMTPA. Located strategically between the

historic cities of Delhi and Agra, the capacity of Mathura refinery was increased to 7.5

MMTPA.

Panipat Refinery is the seventh refinery of Indian Oil. The original refinery with 6.0 MMTPA capacity was built and commissioned in 1998. Panipat Refinery has doubled its

refining capacity from 6.0 MMTPA to 12 MMTPA with the commissioning of its

Expansion Project.

Subsidiary refineries are Bongaigaon Refinery (2.95 MMTPA) and Chennai Petroleum (9.5

MMTPA).

Corporate Mission

To achieve international standards of excellence in petroleum refining, marketing and

transportation with concern for customer satisfaction.

To create a modern technology base for self-reliance, growth and development of the business.

To contribute to the national economy by providing adequate return on investment and by setting high standards of leadership in productivity and total quality.

To help to enrich the quality of life of the community and preserve ecological balance and national heritage.


Business Activities/Objectives

1) Refineries and Pipelines Division

Operate and maintain the existing refineries and pipelines

Improve operating factor

Maximize capacity utilization

Optimize energy use

Protect environment

Modernize and increase capacities of existing refineries/pipelines by low cost debottlenecking/addition of new facilities

Install new crude oil/product pipelines

Diversity into petrochemicals

Professional growth and self development of employees

2) Marketing Division

To ensure and maintain continuous and uninterrupted supply of petroleum products all over the country

To achieve excellence in consumer satisfaction

Advice Govt. on perspective plans and policies for the industry

Professional growth and self development of the employees

Market leadership in the industry

3) Research and Development

Develop formulation for lubes and greases. Nearly 600 lubricants formulation developed of international quality

Develop and improve refining processing technologies

Expertise on waxy fluids transportation by pipelines

Fuel products quality improvement

Evaluate catalyst additives

Assess remaining life of equipments

Develop synthetic lubricants and greases

Developing biodegradable as well as environment friendly lubricants

Developed kinetic model for Hydrocracker for prediction of product qualities at different levels

Developed specific railway signal lamp operable with 18 mm smoke point kerosene

Developed energy efficient household appliances like LPG burners, kerosene lamps for rural

areas


Vision Values

Indian Oil nurtures the core values of Care, Initiative, Passion and Trust

across the organization in order to deliver value to its stakeholders.

Care Stands for

Concern

Empathy

Understanding

Co-operation

Empowerment

Innovation Stands for

Creativity

Ability to learn

Flexibility

Change

Passion Stands for

Commitment

Dedication

Pride

Inspiration

Ownership

Zeal & Zest

Trust Stands for

Delivered promises

Reliability

Dependability

Integrity

Truthfulness

Transparency


EXPERTISE AVAILABLE WITH INDIAN OIL

Debottlenecking

The crude oil refining capacity has been increased from 18.75 MMTPA to 24.55 MMTPA i.e

33% increase achieved mainly through in-house expertise. As such debottlenecking included

necessary revamping of downstream Secondary Processing units as Offsite storage and dispatch

facilities.

All capacity increase projects were also associated with energy conservation and product mix

improvement. Project management including procurement, construction, supervision, start-up

and commissioning was undertaken by in-house expertise.

Technology Upgradation

Following technological developments have undergone in various refinery units:

1) FCCU

Change of catalyst from amorphous to zeolite 2) CRU

Change from monometallic to bimetallic catalyst

Adoption of continuous catalyst regeneration technology 3) VBU

Soaker Drum Technology 4) RESIDUE UPGRADE SOLVENTS

Through hydrocracker from TEG to TTEG and from Phenol to Furfural NMP* (* Normal Methyl Pyridine)

Safety Management

Our refineries have a dedicated Safety Management team and also there is a Safety Management

set-up at HO level. This team has engaged in the following activities:

Constant upgradation/improvement in fire fighting facilities

Regular HAZOP and HAZAN studies

Risk analysis

Disaster Management Plan/Mock Drill

Safety Audit


Energy Conservation

All Indian Oil Refineries have Technical Audit section equipped with experienced engineers.

Energy Conservation activities are undertaken in the following areas:

Steam/power balance

Heat Integration

Co-generation based gas turbines

Continuous Energy Audit

Retrofitting Air Preheaters in old furnaces

Replacement of inefficient equipments not amenable to modifications

Optimizes heat recovery using pinch technology

Waste heat recovery

Environment Management

Refineries of Indian Oil maintain a constant vigil and follow-up on the various aspects of

Environment Management. Elaborate treatment facilities have been provided in all refineries to

handle the following effluents:

Oil contaminated waste water

Acidic/Alkaline waste water

Fecal waste

Sulphur Dioxide emission

The refineries effluents, both liquid and gaseous, are of superior quality and meet all stipulations

laid down by the Government and the Pollution Control Boards. Environment Management

activities in all IOCL refineries include:

Modern Effluent Treatment Plants meeting stringent specification

Reuse of treated effluent

Sulphur Recovery Units

Stack/ambient air monitoring and control

Oily sludge minimization/treatment

Environment impact studies/Environment Audit

Establishing Occupational Health Centers


Maintenance and Inspection

Indian Oil has 30 years of experience in Maintenance and Inspection of its refinery process units,

offsite facilities, loading facilities and cross country pipelines. The Maintenance Departments of

all the IOCL unit are responsible for carrying out the following:

Shutdown Planning, scheduling and arranging of all resources for timely completion of the turnaround work

PM Scheduling, implementation and monitoring

Vibration monitoring, analysis and corrective action

Failure analysis of static and rotary equipments and taking corrective actions

Zero based budgeting

Long term planning

Technical Documentation

Standardization of equipments and spares

Each refinery is having a separate Inspection Department which ensures reliability and safety of

all static equipments. Primary functions of this department are:

Quality Assurance

Corrosion Monitoring

Residual Life Assessment

Non-Destructive Testing

Both Maintenance and Inspection Department are deeply involved in any process plant or offsite

revamp job and give full assistance to the Project Department in timely completion of the project

as well as their smooth commissioning.


GUJARAT REFINERY

Introduction

Gujarat Refinery is the Indian Oils largest refinery, with a crude processing capacity of 13.7 million tones per annum. Indian Oils foray into the petrochemical sector also started at Gujarat Refinery with the successful commissioning of worlds largest single train Linear Alkyl Benzene Plant in August 2004.

The refinerys success is built upon business and community partnerships with the people of Vadodara, as well as production of quality products that are compatible with the community and

the environment. At the heart of the Gujarat Refinerys success, are its employees and their commitment to Indian Oils vision and mission.

Gujarat Refinery is situated at Jawaharnagar near Bajwa Railway station on the broad gauge line

between Mumbai-Ahmedabad on Western Railway at a distance of nearly 10 kms north of

Vadodara. The refinery is spread over an area of 1424 acres out of which refinery units and

offices cover about 859 acres. About 138 acres is developed as green belt area, which is home to

all botanical species indigeneous to this region.

Its facilitates includes five Atmospheric Crude Distillation Units (ADU). The major secondary

units include Catalytic Reforming Unit (CRU), Fluidized Catalytic Cracking Unit (FCCU),

Diesel Hydro Desulphurization Unit (DHDS) and the first Hydrocracking Unit of the country.

Through a product pipeline to Ahmedabad and a recently commissioned product pipeline

connecting to BKPL product pipeline and also by rail wagons/trucks, the refinery primarily

serves the demand for petroleum products in western and northern India.


History

Following the conclusion of an Indo-Soviet agreement in 1961 February, a site for the

establishment of a 2.0 MMTPA Oil Refinery in Gujarat at Koyali near Vadodara was selected on

the 17th

April 1961. The Soviet and Indian engineers signed a contract in October 1961 for the

preparation of the project report jointly. The first Prime Minister of India, Pandit Jawaharlal

Nehru laid the foundation stone of this refinery on 10th

May 1963.

The refinery was commissioned with Soviet assistance at the cost of Rs.26.00 crores and went on

stream in October 1965. The first million tone Crude Distillation Unit was commissioned for

trial production on 11th

October 1965 and full production at the rated capacity was achieved on

6th

December 1965. The throughout was further increased by 20% beyond the designed capacity

in January 1966.

Dr. S. Radhakrishnan, the then President of India, dedicated the refinery to the nation with the

commissioning of the second Crude Distillation Unit and Catalytic Reforming Unit on 18th

October 1966.

The third 1.0 MMTPA crude distillation unit (AU-3) was commissioned in September 1967 to

process Ankleshwar and North Gujarat crudes. In December 1968, UDEX plant was

commissioned

for the production of Benzene and Toluene using feedstock available from CRU. By 1974-75

with in-house modifications, the capacity of the refinery was further increased by 40% to a level

of 4.2 MMTPA. To process Imported crude the refinery was expanded during 1978-79 by adding

another 3.0 MMTPA Crude Distillation Unit (AU-4) along with downstream processing units

like Vacuum Distillation Unit (VDU), Vis-breaker Unit (VBU) and Bitumen Blowing Unit

(BBU). By 1980-81 this unit started processing Bombay High crude in addition to the Imported

crudes.


Technology Leader

It is first amongst Indian Refineries in the following:

First Riser Cracker FCCU in the country

First Hydrocracker in the country

First Diesel Hydro Desulphurization Unit

First Spent Caustic Treatment Plant in Indian Refineries

First Automated Rail Loading Gantry

First LPG Moulded Bullets in Indian Refineries

Operates Southeast Asias biggest Centralized Effluent Treatment Plant

Crude Processing

Gujarat Refinery is designed to process indigenous as well as imported crude oil. On an average

it processes approximately 41500 metric tones of crude oil per day. Out of the crude slot it

receives, the refinery processes around 50% imported crude. Gujarat Refinery achieved highest

ever crude throughput of 13.85 MMTPA in the year 2008-09.

The break-up of the various types of crude oil processed at Gujarat Refinery is as follows:

South Gujarat Crude: 2.15 MMTPA; supply from ONGC South Gujarat crude pipeline.

North Gujarat Crude: 3.70 MMTPA; supply from ONGC North Gujarat crude pipeline.

Bombay High Crude: 1.16 MMTPA; supply from Salaya-Viramgam-Koyali pipeline. Imported Low/High Sulphur Crude: 6.84 MMTPA; supply from Salaya-Viramgam-Koyali

pipeline.

Product and End Uses Fuel Gas Fuel for Industrial Furnaces

LPG Cooking Gas

Naphtha Raw material for Petrochemicals

Motor Spirit Petrol for vehicles

Aviation Turbine Fuel(ATF) Fuel for jet aircrafts

Superior Kerosene Illuminant domestic product

High Speed Diesel(HSD) Diesel for trucks, buses ships, etc.

Light Diesel Oil(LDO) Small engines attached to irrigation pumps

Fuel Oil Industrial furnaces/boilers

Bitumen Road surfacing

Benzene Raw material for Petrochemicals

Toluene Raw material for Petrochemicals

n-Heptane Used as solvent

ARO Used in aluminium rolling industries

Linear Alkyl Benzene (LAB) Detergent manufacturers

Butene Copolymer for producing polyethylene and

polypropylene

Methyl Tertiary Butyl Ether

(MTBE)

Blending in gasoline for increasing octane number and

oxygen content


Food Grade Hexane(FGH) Solvent for oil seed extraction.

Glues/Adhesives for footwear.

Polymerization reaction in industries like

pharmaceuticals and printing ink.

Sulphur Sulphuric acid and tyre manufacture


IMPORTANT UNITS OF

GUJARAT REFINERY

1) Gujarat Refinery Unit-1 (GR-1)

Atmospheric Distillation Unit-1 (AU-1)



Catalytic Reforming Unit (CRU) 2) Gujarat Refinery Unit-2 (GR-2)


Universal Product Dow Chemical Extraction (UDEX)

Food Grade Hexane (FGH)

Methyl Tertiary Butyl Ether (MTBE) Butene-1 Pilot Distillation Fraction (PDF)

3) Gujarat Refinery Expansion Unit (GRE)


Vacuum Distillation Unit (VDU)

Vis-breaker Unit (VBU)

Bitumen Blowing Unit (BBU) 4) Gujarat Refinery Secondary Process Functioning (GRSPF)

Feed Preparation Unit-1 (FPU-1)

Fluidized Catalytic Cracker Unit (FCCU) 5) Gujarat Hydrocracker Unit (GHC)

Feed Preparation Unit-2 (FPU-2)

Hydrogen Generation Unit-1 (HGU-1)

Hydrocracking Unit (HCU)

Hydrogen Generation Unit-2 (HGU-2)

Diesel Hydro De-sulphurisation Unit (DHDS)

Sulphur Recovery Unit (SRU)

Nitrogen Unit 6) Power Generation Effluent Treatment

Cogeneration Plant (CGP)

Thermal Power Station (TPS)

Combined Effluent Treatment Plant (CETP) 7) South block

8) North block


GUJARAT

REFINERY

EXPANSION

(GRE)


CRUDE DISTILLATION UNIT (CDU)

INTRODUCTION

The atmospheric crude distillation unit under Gujarat Refinery Expansion Project is originally designed to process 3.0 MMTPA of 50-50 mixture of North Rumaila and Light

Arabian crude oils.

Subsequently in August 1986 unit was debottlenecked to process 3.3 MMTPA of crude. The unit has processed a variety of imported crude besides indigenously available

Bombay High Crude.

In December 1993, a major revamping of unit was done particularly for increasing the processing capacity of lighter crude i.e South Gujarat and Bombay High at the rate of

10,000 MT/day and also imported crude at the rate of 12,000 MT/day.

In the revamp, a Pre-fractionator column was installed and total debottlenecking of crude Preheat Exchanger train done for improving crude preheat.

In November 1999, the unit capacity was enhanced to 5.0 MMTPA by installation of additional heat exchangers and higher capacity pumps. An additional fired heater was

also installed in parallel operation with existing furnace.

FEED AND PRODUCT SPECIFICATIONS

Feed Feed is 50:50 wt% of North Rumaila and Light Arabian Crude oils. Unit can process Bombay High Crude.

Sr. No. Specification Imported Crude Bombay High

1 Density 0.8741 0.8172

2 Molecular weight 215 -

3 Avg. Boiling Point 282 -

4 Viscosity at 40 C (cst) 11.07 3.47

5 Water content vol% Nil 0.1

6 Sulphur content wt% 2.8 0.22

7 Salt content wt ppm 2.0 537

Product

Sr. No. Specification Naphtha Kerosene LGO HGO RCO

1 Density 0.6890 0.7921 0.8390 0.862 0.9580

2 Pour point - - - - 15

3 Viscosity at 37. C (cst) 0.4 1.55 3.92 8.02 150-170

4 Sulphur wt% 0.0137 0.168 1.07 1.85 3.26


PROCESS DESCRIPTION

The total process can be divided into following sections:

Crude Feed to Unit The different types of crude i.e Imported, Bombay High and South Gujarat are sorted in

different tanks. Before feeding to the unit, water in the crude is separated by settling

(minimum 24 hours) and then drained to OWS.

Booster pumps located in offsite area will take suction from the tanks and delivers into the pump suction. Normally two of the three pumps are running.

For processing slop, slop pumps are used to inject a measured quantity into the discharge of booster pumps.

In crude pump suction, demulsifiers (3 to 4 ppm), caustic solution (about 2% strength) and wash water (2 to 3% on crude flow) are injected for effective desalter operation.

Crude Preheat-1 There are total 15 nos. of heat exchangers in this section where crude is preheated to 135-

1 0 C before going to desalter. Crude, which is at ambient temperature, goes to the heat exchanger where it is treated

against LGO and heated upto 0 C. Crude is further divided into two parallel passes with the help of a differential temperature controller DTC (3 way C/V).

Both the passes travel through separate heat exchangers, exchange heat with products and are heated upto 1 0 C. Crude from the passes combine together and goes to desalter.

Desalter The function of desalter is to remove salt and water, which always remains in the crude.

The removal of salt and water is very important as acid vapour is generated from these

salts at higher temperature at fractionator top portion.

Salt also creates fouling problem in the exchanger at higher temperature. The desalting process consists of three main stages-heating, mixing and separation.

For effective separation of salt and water from crude oil, it is heated upto about 1 0 C thoroughly mixed with extra water (3-4% on crude flow) by passing through mixing

valve at the inlet of desalter (mixing valve pressure drop is generally kept at about 1.0

kg/sq.cm).

The extra water is added to collect and dissolve all the water soluble salts in the crude. The rate at which water is injected into the crude is dependant primarily upon the salt and

BS&W content of crude being treated.

In some instances, it is not possible to achieve sufficient mixing across the mixing valve alone provision is therefore given to inject water ahead of desalter heat exchangers. This water is preheated to 100 C.

The mixing valve, with isolation and bypass facility, is located at the inlet of the desalter. By varying pressure drop across the valve the desired mixing can be achieved. The

normal operating pressure is 10.5 to 11.0 kg/sq.cm(g).

Crude Preheat-2


Booster pump pumps crude from desalter outlet to one of the heat exchangers where crude is treated against Kero CR.

At outlet, the crude flow is divided into two parallel passes by DTC. Crude in both the passes exchanges heat with LGO and RCO respectively. Both the passes combine in the end where the crude temperature is around 175 C.

The two passes that combine are again divided into two passes, and is treated against HGO CR. LGO CR and HGO.

Crude after passing through a series of heat exchangers is fed to the flash zone of pre-fractionator column at a temperature of 225 C.

Pre-fractionator In this column, light naphtha is removed to reduce load on subsequent equipment i.e heat

exchangers, heaters and column etc. There are 22 valve trays in the column. Feed enters

at the 8th

tray.

The lighter vapours travels up in the column and at the top light naphtha vapours are condensed in a series if heat exchangers. Condensed liquid is collected in the reflux drum

and the uncondensed vapours are released to the flare/GR fuel gas network.

The top products i.e Light naphtha (containing LPG) goes to the stabilizer for LPG recovery. From 14

th tray, side aphtha cut is withdrawn at 155 C in case of BH and SG crude. The side cut is stripped in the stripper and its bottom is pumped to naphtha pool or

diesel pool via cooler.

Top temperature of the column is to be maintained at about 11 C for imported, BH and SG crudes (temperature should be at least 15 C above dew point). Top pressure is maintained at 3.2 kg/sq.cm(g) by split range control with flare and hot vapour bypass.

For maximizing recovery of light naphtha, stripping steam is introduced below 1st tray of column at desired rates.

Crude Preheat-3 In this section, crude from pre-fractionator bottom at about 190 C is further preheated to

255-275 C before going to the heater. The crude from pump discharge goes to a set of heat exchangers where the crude is

treated against LGO CR.

Outlet crude flow is divided into two passes by DTC. Here crude exchanges heat with hot RCO.

At outlet of both the passes crude is preheated upto about 275 C. At two outlets passes combine and go to the heater.

Heaters (Furnaces) In the heaters, crude is further heated and partially vapourised by rising temperature from

275-370 C in case of imported and upto 355 C in case of BH/SG crude. Here, furnace is a box type, horizontal tubes, balanced draft furnace. Crude feed flows to

the heater in four passes. The four passes join together and combine at the outlet to go to

the distillation column. There are total 20 nos. of dual (oil and gas) fired burners and one

gas burner in the heater.


Fuel oil pressure of 6.0 kg/sq.cm is maintained by the controller. The atomizing steam pressure to the burners is controlled by differential pressure controller.

Fuel gas is supplied to the heater at about 3.4 kg/sq.cm. If fuel gas pressure falls below 1.8 kg/sq.cm low pressure alarm will sound in the control

room and a safety shutdown valve SDV will automatically cut off fuel gas flow to the

heater, thus eliminating the possibility of back fire.

A return is provided on the fuel oil heater. A 1:1 ratio of fuel oil consumption to return is provided in the design to obtain a good control on firing and prevent congealing of the

internal fuel oil (IFO) system.

The globe valve provided on the IFO return line should be adjusted to give the desired circulation rate. For recovering heat from fuel gases, boiler feed water is circulated

through BFW coils at convection section.

Main Fractionator Partially vapourised crude from the heater outlet enters into the flash zone of the main

fractionator column. In this column, there are total 40 nos. of valve trays. Feed enters at

6th

tray from the bottom.

From the flash zone, vapour portion goes up and while going up it comes into contact with colder liquid coming from the upper trays (called internal reflux) at each tray.

In this way, heavier liquid falls below the next tray and the lighter vapours goes up in the next tray. Thus different fractions are separated in different trays depending upon the

temperature of the tray.

In the flash zone, unvapourised portion i.e RCO goes to the bottom as product. To help vaporizations and thereby more recovery of lighter products, stripping steam is given at

the bottom of the column.

If the transfer temperature is 370 C, flash zone temperature will be about 3 0 C. Reduced crude product is pumped out from the bottom of the column by RCO pumps under level

control.

The liquid from 7th tray is withdrawn entirely, measured by flow meter and put back into the column above 6

th tray.

The amount of flow is a measure of over flash, which is desirable for proper fractionation and recovery of the distillates.

To maintain the heat balance in the column, circulating refluxes are withdrawn from the column, cooled in the heat exchangers and return back to the column. There are total

three refluxes (HGO, LGO, KERO) and one top reflux is used.

HGO product and HGO reflux are withdrawn at a temperature of about 320 C. LGO product and LGO CR are withdrawn at a temperature of about 275 C and return back at a temperature of about 225 C. KERO product and KERO CR are withdrawn at a temperature of about 200 C and return back at about 155 C. Above kerosene, Heavy aphtha is withdrawn at about 150 C.

The top temperature and pressure is maintained at about 11 C and 0.9-1.0 kg/sq.cm respectively.

From the top, naphtha vapour goes overhead condenser, the condensed liquid is collected in reflux drum from where a part goes as product to naphtha pool and other is routed to

diesel pool.


The top pressure is maintained by the pressure controller with the help of flooding C/V located at the inlet of reflux drum and the reflux drum pressure is controlled by split

range controller with C/V on fuel gas make up and flare line.

Reflux drum pressure is maintained at 0.5 0. kg/s .cm(g). The column flash zone pressure and temperature are normally at about 1.1 1.3 kg/s .cm(g) and 3 0 C.

Pressure safety valve releasing to L.P flare header are provided at the top of the column to protect it from over pressure.

The column is cladded internally with 29 mm 410SS from bottom as a measure against corrosion. To control the flash point of products, Heavy Naphtha, Kero, LGO and HGO

are steam stripped in their respective strippers.

Stabilizer In the stabilizer, LPG separated from Light Naphtha is obtained as top product. The

bottom product is stabilized Naphtha and goes to Naphtha pool.

Feed to the stabilizer is pre-fractionator top product i.e Light Naphtha. It is first preheated to about 5 C. Columns bottom temperature is maintained at about 179 C by two reboilers.

The columns top temperature is maintained at about C to maintain LPG weathering. The top pressure is maintained at 9.3 kg/sq.cm(g).

At the top, LPG vapour goes to the condenser from where LPG in the form of liquid is collected in the reflux drum id pumped to the top reflux and to the run down.

From the bottom of the column, naphtha first goes to the cooler. The cooler outlet goes to the Naphtha Caustic wash section.

Naphtha Caustic Wash To remove corrosive sulphur compounds i.e Mercaptans, caustic wash is given. Main

fractionators overhead Naphtha and AU-3 Naphtha combine together and go to Drum (D-

1) for caustic wash.

For washing, caustic circulation pump is used. Caustic and Naphtha is mixed in the mixing valve before entering into D-1.

In the vessel, caustic separates out and goes to the bottom and Naphtha overflows from the top. Continuous make-up and draining of caustic is done through level control valve.

After caustic wash, Naphtha goes for water wash for removing any carryover of caustic. This is done in Drum (D-2) in the same way as in D-1. Here also fresh water is added

continuously and the same amount is drained out.

After water wash Naphtha goes to run down tanks.

LPG Caustic Wash To obtain copper strip corrosion, the dissolved H2S and Mercaptans in LPG are removed

by caustic wash.

In this system, LPG run down is received in the surge drum from where it is pumped to caustic wash system.

Drums D-2 and D-3 are used for LPG caustic and water wash respectively. About 50% caustic level is maintained in the flare knock out drum. For caustic circulation, pumps are

used.


At the inlet of the flare knock out drum LPG and caustic are thoroughly mixed in the mixing valve and orifice mixture for removing H2S and Mercaptans. In the vessel,

caustic separates out and goes to the bottom and LPG overflows from the top.

CHEMICAL INJECTION FACILITIES

De-emulsifier:- De-emulsifier is injected in the crude pump suction to break oil and water emulsion in

desalter. Normal injection rate is 4 to 5 ppm. However, if oil is observed in desalter drain

water, de-emulsifier injection rate has to be increased.

De-emulsifier chemical is brought in drums and offloaded into the vessel. The de-emulsifier injection pumps are dosing pumps provided with a safety valve. The rate of

injection can be varied by adjusting the knob on the pump.

Caustic Solution:- Caustic is injected in the crude pump suction, as water separation from oil in desalter

becomes better in alkaline medium. For this, brine water pH is maintained at about 8.0 to

9.2. 3% wt caustic solution is prepared in the tank and injected by pump.

At the desalter also, the same caustic is injected to neutralize the chloride salt. The chloride salt in the crude produces HCl (Hydrochloric Acid) at higher temperature.

This HCl is highly corrosive to column overhead, vapour line and the reflux drum. Hence, caustic is injected to neutralize HCl to NaCl (sodium chloride).

Finally NaCl goes out from bottom of the main fractionator along with RCO. Any left over HCl vapour goes to the top and finally comes along with sour water.

Hence, if sour water chloride contents are reported more than 6 ppm, caustic injection post desalter has to be increased. Also sour water pH is to be maintained at 6.5 to 7.0

with the help of ammonia injection.

Ammonia Injection:- Ammonia solution is injected in the crude fractionating column overhead and in pre-

fractionator column to neutralize highly corrosive acid HCl.

Ammonia converts HCl to ammonium chloride (NH4Cl). About 1% strength ammonia solution is injected in the top vapour line and in the top reflux line.

It is very important to know that the use of excessive ammonia will cause leak in the overhead condenser tubes. This is because ammonia reacts very fast with the brass metal

and eats away the metal.

Hence, sour water pH to be maintained strictly not more than 6.5. Ammonia is brought in the unit in cylinders. Water is received in the two solution vessels.

Ammonia solution is prepared by injection of ammonia from ammonia cylinder into the solution vessel. A pressure gauge and safety valve are provided on the ammonia

connection manifold.

To prevent cooling and icing of the cylinders when preparing ammonia solution, a connection to spray water is provided. The solution vessels are provided with seal to

minimize the loss of ammonia.


Corrosion Inhibitor Injection:- Corrosion inhibitor is an organic chemical. It acts as corrosion inhibitor by forming

continuously a monomolecular layer on the metal surfaces, by direct contact between

metal and the corrosive elements present in the system.

This is injected at the top f the vapour line of the crude fractionating column overhead and in the stabilizer column to protect vapour line and condenser.

Normal injection rate of 4 to 6 ppm is maintained by the pump.

VACUUM DISTILLATION UNIT

(VDU)

INTRODUCTION

The Vacuum Distillation Unit (VDU) of Gujarat Refinery was commissioned in 1979.

The unit was designed to process 800,000 MTPA of RCO (50:50 North Rumaila and

Arab Light).

The unit produced Light Vacuum Gas Oil (LVGO); used as LDO blending component, Heavy Vacuum Gas Oil (HVGO); used as VBU feed and Vacuum Residue (VR); used as

Bitumen Feed and VBU feed stock.

After commissioning of FCC unit, HVGO from VDU is used as one of the feed components of FCCU. The yield of desired quantity of HVGO for FCC feed was very

low.

In 1994, low cost revamp of VDU was undertaken to meet the following objectives: To increase yield of Vacuum Gas Oil (VGO) of desired quality for FCCU feed

stocks.

To improve VR quality for BBU feed. To increase unit throughput. To increase energy savings by using redundant equipments from other projects.

After revamp, VDU can process 880,000 MTPA of RCO. LVGO and HVGO are used as FCCU feed stocks. In addition, provision is made for routing LVGO to HSD as blending

stock.

In 1999, low cost revamp of VDU was undertaken to meet the following objectives. Throughput enhanced from 0.88 MMTPA to 1.2 MMTPA.

To increase VGO yield and improvement of its quality. Reduce less than 370 C cut in VGO. Better bitumen feed quality.


After revamp VDU can process 1.2 MMTPA of RCO, Heavy diesel as top product used as HSD, LVGO+HVGO used as VGO for FCCU feed stocks.

In the present column, there is a provision for withdrawal of four side cuts viz. Heavy diesel from top, LVGO, HVGO and slop distillate.

Bigger wash zone provided to maintain VGO quality as well as VR quality to suite Bitumen production.

In October 2004, VDU Air Pre heater (APH) revamp was done for increasing furnace efficiency and to recover heat from stack flue gas.

FEED AND PRODUCTS

The Vacuum Distillation Unit (VDU) is originally designed to process Reduced Crude Oil (RCO) obtained from Crude Distillation Unit (CDU) while processing imported

crude. However, RCO obtained from various imported crude and indigenous crude

(Bombay High, North Gujarat, South Gujarat mix.) has been processed successfully.

By distilling the RCO under vacuum in a single stage column, it produces Heavy diesel, Light Vacuum Gas Oil (LVGO), Heavy Vacuum Gas Oil (HVGO) and Vacuum Residue

(VR). Slop cut (distillate between HVGO and VR) production facility has been provided

since 1988.

UTILITIES AND THEIR CONSUMPTION

Sr.

No.

Utility Consumption Uses

1 LP Steam, T/hr 2.5 Stripping

2 MP Steam, T/hr 10.0 Ejector, Atomizing, Soot blowing, Velocity,

Snuffing and Emergency

3 Cooling water,

cu.m/hr

1400 Condensers, Coolers

and Pumps

4 DM water 10.0 Steam generation and Tempered water

5 Fuel Oil, T/hr 1.7

6 Fuel Gas 300-800

\

PROCESS DESCRIPTION

Brief Description Cold RCO is received in the feed surge drum under level control from storage tanks. Hot

RCO may be received from the Crude Distillation Units. RCO is pumped by charge

pumps to a series of preheat exchangers and then to furnace from where feed goes to the

main column.

In the 1st heat exchanger LVGO exchanges heat with RCO where RCO is in the shell side and LVGO+Pump Around (PA) in the tube side. In the 2

nd heat exchanger HVGO

withdrawn from column heats RCO in the shell side. Then in the next heat exchanger

slop cut exchanges heat with RCO followed by heat exchange with vacuum residue (VR).

At the end of the preheat train, feed is heated upto 305 C in case of hot feed and upto 292 C in case of the cold feed.


Preheated RCO is split into two passes and introduced to Vacuum Heater i.e furnace under pass flow control for each pass. MP steam is injected in each pass to increase

velocity and encourage vapourization of feed in the coils.

Coil outlet temperature of 395-39 C is maintained at the furnace outlet. Partially vapourized RCO is introduced in the flash zone of the vacuum Column.

LP steam is superheated upto 350 C in the convection coils of furnace and used as stripping steam in the stripping section of the vacuum column.

Vapourized RCO along with steam rises through the vacuum column and is fractionated into four nos. of withdrawals.

1st withdrawal is Heavy Diesel which after exchanging heat with feed in the heat exchangers is cooled to 55 C. One part is fed to the top of the column as cold Circulating Reflux (CR) and another part is fed as Internal Reflux (IR). Balanced Heavy Diesel is

sent to the storage under flow control.

2nd withdrawal is HVGO+PA by pumps. HVGO is bifurcated into two streams. One stream is returned as IR to column and another stream is returned to the column as cold


CR after exchanging heat with RCO. HVGO also exchanges heat with water and

generates steam in one bundle. Subsequently, it is cooled in HVGO cooler and sent to the

storage under flow control.

3rd withdrawal is LVGO by pumps. One part is returned as IR along with cold HVGO and another part as cold CR. Third part goes with HVGO rundown as VGO (Vacuum Gas

Oil). VGO may be routed to FCCU (Fluidized Catalytic Cracking Unit), VBU (Vis-

Breaker Unit), LSHS and slop.

4th withdrawal is the slop cut through chimney trays by pumps. Slop cut withdrawn is routed to LSHS/FO/LDO pool. A stream of slop cut is returned back to the column as IR

in flash zone.

Vacuum Residue (VR) is withdrawn as column bottom by pumps. After preheating the feed in a series of heat exchangers, a quench stream is routed back to the column to maintain bottom temperature of 355 C to avoid coking in the column boot.

Further VR goes to the LP steam generator an gets cooled upto 150 C. VR is routed as follows:

Before getting cooled Hot VR to BBU under flow control Hot VR to VBU under flow control Hot VR to VR burning facility Hot VR to IFO drum

After getting cooled Direct VR injection in BBU After cooling in the tempered water cooler, VR is routed to storage as 130 C

Tempered water, required for cooling is obtained from tempered water tank. Hot tempered water is cooled with cooling water in the tempered water cooler to maintain

temperature of hot circulating tempered water.

The desired vacuum is obtained by pulling vacuum by multistage ejectors, pre-condensers, intermediate condensers, after condensers and hot wells.

Detailed Description The Vacuum unit consists of the following sections, viz. Surge Drum and Preheating

Section, Vacuum Heater, Vacuum Column and Product Cooling, Vacuum Overhead

System, Steam Generation and Tempered water System.

The detailed description of the various sections and some important parameters are described below:

Surge Drum and Preheating Section The surge drum is a horizontal vessel. The feed to the unit consists of three streams of

Reduced Crude Oil (RCO) at about 120 C. Reduced Crude is also drawn from the storage tanks at about 0 C through pumps and it maintains the level in the surge drum.

A pressure of 1.0 kg/sq.cm is maintained in the surge drum. The pressure controller on the surge drum acts on the two control valves on the split control.


One of them maintains pressure in the surge drum by admitting fuel gas. If the pressure rises beyond the desired level 2

nd valve opens letting down the pressure to

the flare.

A safety valve with spare is provided to protect the vessel against over pressure. The line from feed surge drum to flare is routed through a knock out pot to avoid any

liquid from entering the flare header. An LP steam coil is also provided in the surge

drum to maintain the temperature.

The reduced crude charge pumps takes the suction from feed surge drums. A pressure indicator and a low pressure alarm are also provided on the common discharge line.

The reduced crude gets progressively heated from 120 C to 300 C by LVGO+PA in the exchanger then by HVGO and then followed by HVGO+PA in the exchanger. A

slop cut paralleled with VR is followed.

Temperature indicator is provided on the line to the Vacuum furnace which measures the outlet temperature of the reduced crude.

Each of these exchangers is provided with isolation and bypass valves both in the shell and tube side. The exchangers are also provided with temperature and pressure

gauges so that the performance of each exchanger can be evaluated.

The reduced crude side of these exchangers is provided with TSVs (Temperature Safety Valves) to provide thermal relief in case the reduced crude side of an

exchanger is double blocked with the hot stream in commission.

Vacuum Furnace Reduced crude enters two passes of the vacuum heater through control valves. Low

flow alarm is provided for the two passes.

Pressure gauges are located at the inlet of the each pass of the furnace and at the entire external crossover of the oil coils. Temperature indicators are also provided in

the external crossover.

To increase the velocity of the reduced crude in the coils and to avoid coking, MP steam is injected in both the passes.

The partially vapourized stock leaving the heater is transferred into the flash zone of the vacuum column. A pressure gauge with temperature indicator and controller is

provided in the transfer line.

Transfer line temperature is adjusted to about 395 C to maintain flash zone temperature of about 375 C.

Vacuum Furnace is provided with Air Pre Heater to improve the furnace efficiency along with FD fans and ID fan.

In addition to the oil coils, the convection section has two more coils, one for superheating steam and other for producing steam from boiler feed water.

The superheating coil is provided with safety valve and venting facility at the outlet. 16 soot blowers are provided in the convection section to remove soot and ash

deposits on the tubes.\

Vacuum Column and Product Routing Vacuum Column:


The function of the vacuum column is to permit relatively low temperature fractionation of the reduced crude into Heavy Diesel (HYD), Heavy Vacuum Gas Oil

(HVGO) and Light Vacuum Gas Oil (LVGO). This is made possible by vacuum and

partial pressure effects of the steam.

Vacuum columns have different diameters. As the column operates under vacuum, vapour velocities are high. Sections where vapour velocities are low are smaller in

diameter to affect cost savings.

The tower has 5 packed beds with chimney trays above the flash zone in the rectification section and 5 trays below in the stripping section.

Product Routing: Heavy Diesel PA are drawn off from chimney tray at a temperature of 135 C by

pump. It is routed to a heat exchanger where it is cooled to 5 C. At the outlet of the cooler it splits into PA return and Heavy diesel to storage.

On the PA return line a three way valve is provided which bypasses one heavy diesel PA from heat exchanger inlet to control the temperature of the pump around return 5 C.

The column top temperature at 0 C is achieved by temperature controller, which adjusts the flow of PA to the column. Flow of heavy diesel to storage is controlled by

the flow controller.

It can be routed to LDO/HSD/DHDS storage tanks or to FCCU or to furnace oil header. Before entering the tower the PA flows through a strainer which is provided

with block and bypass valves.

Vacuum Overhead System A two stage steam ejector maintains vacuum on the tower with surface condensers. Steam, vacuum overhead gas oil and a small amount of light hydrocarbons produced

by cracking pass out of the top of the vacuum tower into a pre-condenser where most

of the gas oil products and stripping steam is condensed.

Non-condensable gases are sucked by steam ejector and are partially condensed in the after condenser.

Non-condensable from after condenser escapes to atmosphere at higher elevation after passing through liquid seal in the hot well. This is to avoid ingress into the

column during steam failure.

A fuel gas back-in line is provided near the inlet of Vacuum overhead Pre-condenser for start-up purposes.

Aqueous ammonia is injected in the overhead vapour line at the top to control the pH of sour water between 6.5 to 7.0 in Vacuum Condensate Drum (hot well).

Preparation and dosing facility of aqueous ammonia solution is provided in VBU unit.

Cooling water circulates in series or parallel through the condensers. While in series, it enters pre-condenser and from outlet splits into two streams; one

stream flows through inter-condenser and the second through after condenser. While

in parallel, the cooling water enters independently the pre-condenser and water from

the inlet of HVGO cooler enters the inter and after condensers in parallel.


Condensate from the condenser shells drops through the sealed dip legs into the hot well where the oil and water separate. Hot well is a horizontal vessel consisting of

two sections separated by a baffle.

The pumps in the vacuum unit that take suction from the vacuum tower are served by a vacuum vent system. The vents from the various vacuum pumps are connected to a

header, which enters below the first tray of the rectification section in the vacuum

tower.

The vent system is necessary so that a vacuum can be pulled on a pump casing before the suction valve is opened.

The following pumps are served by the system: Heavy Diesel + PA pump HVGO pumps Vacuum Residue and Quench pumps HVGO PA Slop Distillate pumps LVGO + PA-2 pump

Tempered Water System In this system the boiler feed water (BFW) is used in a close circuit for cooling

purposes. This particular cooling system has been provided for vacuum residue, slop

cut and bitumen, which should not be cooled below its pour point.

The system consists of surge drum, three circulation pumps, three tempered water product coolers viz. Vacuum Residue cooler, Slop cut cooler and Bitumen cooler

latter located in Bitumen unit and one tempered water exchanger.

Boiler feed water make-up is provided to make up for evaporation losses. Due to evaporation losses, pH of tempered water comes down and becomes acidic in nature.

pH of tempered water is checked manually in intervals. If pH comes down, Morpholine chemical addition facility is also provided.

Tempered water or hot water is drawn from the surge drum at a temperature of 5 C and routed to exchangers where it cools the product.

Tempered water gets heated to 5 C in this process. It is again cooled to 5 C by cooling water before it enters the surge drum. Steam can be injected into the surge drum in case the water temperature drops below 0 C.

Waste Heat Boiler There are two waste heat boilers in VDU. The 1st waste heat boiler is provided to remove heat from LVGO and HVGO streams

and produces LP steam. It consists of a shell with two tube bundles. One bundle

caters for LVGO and the other for HVGO.

LVGO enters at a temperature of 210 C and leaves at a temperature of 175 C. HVGO enters at 210 C and leaves at 150 C. Boiler feed water at 103 C is fed onto the shell side of the boiler. Two safety valves are provided to safeguard the boiler from over

pressure.

The 2nd waste heat boiler is provided to remove heat from VR and produces LP steam. VR flows in the tube side it gets cooled to 175 C from 210 C. Boiler feed water at 103 C is fed to the boilers shell side.


Continuous and intermittent blow down from both the boilers are fed to the blow down drum

which is vented to the atmosphere. This controls the total dissolved solids in the boiler water.

The oil side of the waste heat boiler is provided with block valves and bypass to facilitate shut

down for inspection.

VIS-BREAKER UNIT

(VBU) INTRODUCTION

The Vis-breaker Unit was originally designed to process 1.0 MMTPA of atmospheric

residue, vacuum gas oil and vacuum residue from a 50:50 blend of Light Arabian and

North Rumaila crudes for the production of fuel oil.

In the year 1993, the unit was revamped with introduction of soaker technology for increasing its capacity from 1.0 MMTPA to 1.6 MMTPA using 100% North Gujarat or

Imported Crude vacuum residue as feed stock for the production of fuel oil.

As per requirement, fuel oil is also produced by using vacuum residue as feed stock and then adding cutter stock.

In conventional coil cracking, the residence time in the coil is less, hence the desired conversion is achieved by maintaining higher ( 70 C or more) cracking temperature.

However, in soaker technology, the same amount of conversion is achieved at much lower temperature ( 55 C or less) by providing adequate residence time at its cracking temperature in the Soaker Drum.

Cracking starts in the heater coils and this cracking reaction is allowed to continue in the soaker drum.

Thus both temperature and residence time are very much important for achieving desired degree of conversion.

At the outlet of soaker, a back pressure control valve maintains sufficient back pressure (about 12.0 kg/sq.cm) in the soaker drum and in the heater coils so that the reaction

mixture remains in the liquid phase and thus helps in maintaining adequate residence

time for desired conversion.

The unit is designed for normal conversion of 5.7 wt% of feed with the production of stable fuel oil.

Excess conversion results in instability in the fuel oil and viscosity starts increasing. Instability occurs due to separation of asphalteness.

In the soaker Vis-breaker, since cracking temperature is maintained lower as compared to that of coil cracking, the rate of coke deposition in the heater coils is less and fuel

consumption is also less.


The unit consists of two pass cracking heater, soaker and a fractionator. The products of the units are fuel oil, VB gas oil, VB Naphtha and fuel gas.

FEED AND ITS SPECIFICATIONS Atmospheric Residue Vacuum Gas Oil Vacuum Residue from a 50:50 blend of Light Arabian and North Rumaila

Sr.

No.

Specification North

Gujarat

VR

Imported

VR

Bombay

High VR

North

Gujarat

RCO

Imported

RCO

1 Specific Gravity 0.994 1.029 1.015 0.940 0.973

2 Pour Point ( C) +54 +54 +78 +39 +15

3 Sulphur

(wt %)

0.29 5.13 0.77 0.19 3.91

4 Kinematic Viscosity at 100 C (cst)

1540 2524 1396 63.5 74

5 Wax content 22.3 - - - -

PRODUCTS

Fuel Gas VB Naphtha VB Gas Oil VB Tar

UTILITIES AND THEIR CHARACTERISTICS

The pressure and temperature of the utilities at the battery limit of the unit are:

Sr. No. Description Pressure (kg/sq.cm) C)

1 LP Steam 4.5 165

2 MP Steam 10.0 230

3 Re-circulating water supply/return 5.5/3.5 33/45

4 Boiler feed water 22.5 190

5 Fuel Oil 10.0 80-271

6 Fuel Gas 3.1 35-50

7 Service water 3.5 Ambient

8 Service air 7.0 Ambient

9 Instrument air 7.5 Ambient

10 Flushing oil 8.0 40


PROCESS DESCRIPTION

Brief Description The various components of the feed are first preheated in the heat exchanger to about

150 C and then received in the surge drum. The combined feed stock is pumped by the Vis-breaker charge pump in to the heat

exchanger set to about 315 C and the feed suction goes to the suction of the charge booster pump.

The hot feed from the discharge of the booster pump is routed to the two passes of the Vis-breaker furnace under flow control.

The VB furnace provides the heat required for preheating and cracking reactions of the feed is heated upto 5 C.

At the furnace outlet, feed enters the soaker drum from the bottom and comes down from the top.

In the soaker drum, cracking reactions are allowed to continue at its cracking temperature by providing residence time of about 20 minutes for the desired conversion.


At soaker outlet, one back pressure controller maintains a constant back pressure of about 12.0 kg/sq.cm in the soaker and in the heating coils so that the reaction mixture remains

in the liquid phase and thereby increases its residence time for better conversion.

The hot reaction mixture at the soaker outlet is uenched by injecting cooled Vis-breaker tar to about 3 C for arresting further cracking reactions.

The quenched effluent from the soaker outlet enters the VB fractionator where it is separated into various products.

In the bottom of the VB fractionator, steam is introduced to remove lighter fractions. As and when required, slop oil from GRE tanks is also fed to VB fractionator along with gas

oil in the transfer line for stripping out the light ends.

VB tar is removed as bottom product. The bottom product goes to the fuel oil tank or LSHS (Low Sulphur Heavy Stock) tank depending upon the feed quality.

One side draw i.e VB gas oil can be routed to HSD, LDO, DHDS or LSHS. However it is normally routed to LDO/DHDS.

To maintain the thermal condition of the column and heat recovery, one gas oil circulating reflux has been provided.

The overheads from the VB fractionator are VB Naphtha and gas. Gas is sent to the fuel gas network. Naphtha is stabilized in a debutanizer and is sent to

the Naphtha Merox Unit for removal of the sulphur compounds and finally to storage.

Detailed Description

Feed Supply and Preheating The feed to the Vis-breaker unit consists of Cold VR from storage, VR from VDU

plant, RCO from storage tanks, Hot RCO from CDU, HVGO of VDU unit and RCO

from AU-3.

Among all these feed normally almost 100% VR is used as feed from different unit during LSHS/FO run.

All the feed from different sources is first preheated in the heat exchangers to about 150 C and then goes to the feed surge drum.

The drum level is maintained by varying the flow of clod feed. In case of hot feed, it is directly routed to the surge drum skipping the first set of heat exchangers.

The feed drum pressure is maintained by Split range control. Surge drum pressure is maintained at 2.5 kg/sq.cm.

VB charge pump (screw pump) routes the feed through VB feed via VB tar exchangers. The feed is heated upto about 315-320 C.

The VB charge booster pump takes suction from the exchangers outlet and routes the feed to the two passes of the VB furnace. The flow in the passes is controlled by

flow controllers.

VB Heater Originally VB heater was natural draft furnace. In the soaker revamp, the convection

section height of the furnace has been increased to accommodate more number of

hydrocarbon preheat, and the other coils and in view of this two nos. ID fans have

been provided for maintaining draft level of the heater.


The radiation section of the heater is twin cell type where each cell is further divided into two sections.

In each section burners are fired along the bridge wall. Total 64 nos. combined oil and gas burners have been provided with pilot gas burner.

The convection section is common which houses the hydrocarbon preheat coils, steam-superheating coils, BFW steam generation coils and BFW preheat coils. The

radiation section houses cracking zones of the coils.

One Temperature Safety Valve (TSV) has been provided at the outlet of the preheat coils. The coils are also provided with a safety valve with spare to protect the coils

against overpressure.

The feed is preheated in the convection section and then it passes to the radiation zone. The VB feed to the heater flows in two passes. Combination of oil and gas

burners are used.

There are soot blowers in three different levels of the convection zone of the furnace.

The soot blowers are electric motor driven and MP steam is blown from these blowers to blow out loose soot from the studded tubes.

Soaker The soaker drum is a hollow vessel, it provides adequate residence time to complete

the desired cracking reaction by the time the feed mixture comes out at the soaker

outlet from the top.

Partially cracked feed at the outlet of the heater enters the soaker drum from the bottom.

At the inlet, feed distributor is there for uniform distribution of the feed along the horizontal cross section of the vessel. This helps to eliminate channeling and the

stagnant zone in the vessel.

To measure the temperature profile in the soaker, thermocouples have been provided. 15-20 C drop in the temperature is observed from bottom to top due to endothermic nature of cracking reactions. If the temperature drop is less, it indicates

les amount of cracking.

To maintain the reaction mixture in liquid phase in the soaker drum as well as in heater coils to have better residence time for cracking one back pressure control

valve has been provided at the soaker outlet which maintains about 12.0 kg/sq.cm

back pressure in the soaker and in the heater coils.

At the soaker outlet the cracked mixture is uenched with cold VB tar at 250 C for bringing down the temperature from 20-3 C. Quenching is done to stop further reaction.

During the course of reaction, certain amount of coke also deposits along the inside surface or soaker drum.

To empty out the soaker vessel during normal or emergency shutdown, one soaker pump outline from the soaker bottom inlet line to the fractionator bottom outlet line

has been provided with control valve located near the soaker bottom.

To avoid coking up of the pump out line, provision is there for continuous injection of flushing oil.


VB Fractionator:- The quenched effluent from the soaker outlet enters the VB fractionator. It separates

into VB tar as bottom product, VB gas oil as side product, naphtha and gas as

overhead products.

The fractionator has 2 trays and the feed enters into the flash zone at about 375 C. In the bottom section, VB tar product is steam stripped.

Superheated steam at 10.0 kg/s .cm and 370 C enters the column for stripping of which the flow is controlled and measured by controllers.

The VB fractionator bottom product at 350 C is passed through coarse tar filters and then through the fine tar filters. This VB tar is cooled by passing it through the

exchangers and thereafter divided into three streams.

One portion goes to the soaker top as quench, the second portion goes to the fractionator bottom as bottom quench and the third portion under level control of the

fractionator is routed to the MP steam generator.

As side product VB gas oil is withdrawn at about 250 C. Gas oil is withdrawn to the stripper where lighter material from the gas oil is stripped off with the help of the

superheated stripping steam.

Gas oil from the bottom of the stripper goes to the heat exchangers and is further cooled and sent to either LDO or HSD or FO/LSHS or DHDS pools.

Gas oil is withdrawn into three streams. One stream is used as heating medium to debutanizer reboiler. Second stream is used to MP steam. Gas oil after getting

cooled returns as CR. Third stream directly goes as tray wash to avoid coke

depositions and chokages.

The overhead vapours from the fractionator at 1 7 C are first partially condensed in the Air-Fin cooler and then it goes to final condenser. Condenser outlet is separated

in the reflux drum.

The sour water from the reflux drum is routed to sour water stripper feed drum. A portion of the condensed hydrocarbon liquid is pumped back to the fractionator as

top reflux.

Debutanizer Naphtha from the VB fractionator reflux drum is fed into the debutanizer. The overhead product at 5 C goes to the condenser and the condensed liquid is

collected in the reflux drum. The debutanizer pressure is maintained at about 7.5

kg/sq.cm.

Debutanizer bottom goes temperature is maintained about 1 0 C by the reboiler where the gas oil CR stream is used as heating medium.

The debutanizer bottom goes by its own pressure to the exchanger and then to the cooler where it is cooled to 0 C.

From the cooler the debutanized naphtha goes through flow controller and is further routed to the Naphtha Merox Unit for treatment.


BITUMEN BLOWING UNIT

(BBU)

INTRODUCTION

The Bitumen Blowing Unit (BBU) under Gujarat Refinery Expansion was designed to

process Vacuum residue obtained from 50:50 blend of North Rumaila and Light Arabian

crudes to process 200,000 metric tones per year of 80/100 pen, 25,000 metric tones per

year of 60/70 pen and 25,000 metric tones of 30/40 pen bitumen product.

The unit was designed to operate in blocked out operation to produce the above three grades of bitumen.

The major equipments of Bitumen Unit are located in the Vacuum Unit plot area and a no. of common utility systems serve both these units.

The chief advantage of the Biturox process is the flexibility in the feed stock that can be used for the production, a wide range of other materials like Propane de-asphalted and

Vis-breaker residues blended with vacuum gas oil/extract can be used in a proper

blending rate.

The biturox unit is designed for continuous operation and the capacity range of the unit covers 60-100% of the designed capacity.

FEED AND ITS SPECIFICATIONS

Persian Gulf crude or a mixture of Persian Gulf and North Gujarat crude will be used as feed stock.

As design feed, the mixture of Persian Gulf and North Gujarat crude was selected for the design of the Biturox Reactor.

A longer retention time was required for the production of S65 using vacuum residue

from the mixture of Persian Gulf and North Gujarat crude.

Sr.

No.

Specification Unit VR Persian Gulf

crude

VR Persian Gulf/North

Gujarat crude

1 Penetration

index

mm/10 155 234

2 Softening point C 40.5 41.0

3 Specific gravity 1.0198 0.9995

4 Density at 15 C Kg/cu.dm 1.0259 1.0056

5 Flash Point C 320 316


PRODUCT AND ITS SPECIFICATIONS

The product obtained is three grades of bitumen. S90 grade bitumen------------------- 99% yield S65 grade bitumen------------------- 98.5% yield S35 grade bitumen------------------- 97.5% yield

Sr. No. Specification Unit S90 grade S65 grade S35 grade

1 Specific gravity 0.99 0.99 0.98

2 Water content wt% 0.2 0.2 0.2

3 Flash point C 175 175 175

4 Softening Point C 35-50 40-55 50-65

5 Penetration index mm/10 80-100 60-70 30-40

UTILITIES AND ITS CHARACTERISTICS

Sr. No. Utility C) Pressure (kg/sq.cm)

1 LP steam 151 4.0

2 MP steam 230 10.0

3 Boiler feed water 105 14.5

4 Fuel gas 35-50 1.7-2.1

5 Fuel oil 80-271 10.4

6 Tempered water 65-85 5.0

7 Circulating cooling water 33/45 4.5/2.5

8 Supply/Return service water Ambient 2.5

9 Instrument Air Ambient 7.0

PROCESS DESCRIPTION

Brief Description The unit shall receive hot feed (vacuum residue) from the vacuum unit directly at a

temperature of about 2 0 C and cold feed from storage. hen vacuum unit is shutdown, bitumen unit will receive the entire feed from storage at

120 C. The feed enters the converter at a temperature of 2 0 C. This is achieved by heating the

feed in the heater.

The vacuum residue is blown by air in the biturox reactor at temperature of around 2 0 C.

Since this is an exothermic reaction, the evolved heat is to be removed. This is accomplished by injecting water along with Process air and steam into the reactor at the

top.

The blown bitumen is pumped from the Biturox reactor under level control through the steam generator and the bitumen product rundown cooler.

The hydrocarbon vapours, steam and the unreacted air from the reactor overhead go to the water quench drum where hydrocarbons are condensed along with some water.

The uncondensed gas is burnt in the incinerator through the water seal drum.


The condensed hydrocarbons and the water are separated in the settling drum from where the oil is routed to slops and the water drained to oily sewer.

Detailed Description The following subsections describe the process flow of the Bitumen Unit in detail:

Feed Heating System The feed to the bitumen unit consists of the hot vacuum residue taken directly from the

vacuum unit and cold vacuum residue from the storage.

The hot VR enters the bitumen unit at a temperature of about 2 0 C. The flow of the feed is controlled by a valve.

The cold vacuum residue from the storage is pumped by feed pumps to the furnace where the vacuum residue is heated to a temperature of about 215 C.

The temperature of the feed is maintained at 232 C. The combined feed is then routed to the biturox reactor.

Steam Generator Steam generator is a horizontal kettle type exchanger having two tube bundles in a single

shell.

Heat exchange of the bitumen rundown is carried out through both the bundles with Boiler Feed ater to reduce the combined feed temperature to 200 C.

Boiler feed water flows on the shell side under the level control of which actuates the control valve on the boiler feed water line to the steam generator.

Low pressure steam is generated in the shell side. Steam generated in the shell joins the low pressure steam header running on the vacuum-bitumen unit pipe rack.

Flow indicator is provided to measure the amount of steam generated in the exchanger. Steam disengagement facilities are provided in the shell to avoid carryover of water with

steam.

Bitumen Feed Pumps The bitumen unit gets its cold feed from the vacuum residue storage tanks at a

temperature of 120 C. The bitumen feed pumps take suction from the storage tanks through suction line. One

pump is running normally and the other serves as spare.

The feed pump discharges vacuum residue at a pressure of 8.8 kg/sq.cm, which flows to the bitumen heater for heating to the reaction temperature.

A slip stream of vacuum residue from the discharge of the pump goes as a feed component to the Vis-breaker unit.

Bitumen feed pumps are screw type steam jacketed pumps. Each pump is fitted with a built in relief valve for protection against over-pressure.

Bitumen Heater The vacuum residue from the discharge of the feed pump is to be heated in the Bitumen

Heater from a temperature of 120 C to the reaction temperature of 215 C.


Bitumen heater is a vertical cylindrical type furnace having a single helical coil in the radiation zone. The heater is provided with three oil burners having self-inspiriting gas

pilots.

The temperature of the feed at the outlet of the heater is controlled by temperature controller, which is cascaded to the fuel oil pressure controller actuating the control valve

on the fuel oil line to the heater.

The bitumen heater has three main burners, which can be fired by oil only. Each main burner is provided with a gas pilot.

The burners should be operated to provide fire, which are uniform in length and size as can be obtained.

It is normally desirable to fire all three burners even when running at reduced capacity to ensure uniform heat distribution to all tubes.

Biturox Reactor The reactor unit, where biturox process occurs, consists of three main components:

Biturox reactor Agitator, with three stages of disc mixers Guiding cylinder, located concentric to the shell and containing two coalescing

plates, each one is located under the middle disc mixer and the other under the

upper disc mixer

Measured amounts of feedstock, air and water are simultaneously fed into, and processed within the reactor unit.

Compressed air is fed into the guiding cylinder through four vertical air injection pipes and flows down through the pipes to the bottom of the reactor where it is blown into the

incoming feed.

As air injection pipes are large in diameter, the air bubbles created at the bottom of the pipes are large and, as such, minimize the amount of available oxygen at the air inlet,

which prevents overheating and the coke formation at this point.

Overhead System of the Biturox Reactor Off-gases from the biturox process contains N2, residual O2, water stream, CO, CO2,

H2S, SO2 and the hydrocarbons with the average molecular weight of C17 kg/kmol.

To prevent the deposits in the off-gases line, make-up water (BFW) will be injected into the off-gases pipe. Due to vapourising of BFW the temperature of the off-gases will be reduced approximately to 170-1 0 C.

As a result of the off-gases cooling, a part of the hydrocarbons will condense from the off-gases and wash the pipe.

The amount of injected BFW is controlled with the flow control. Temperature meter measures the temperature of the off-gases after injection, which is located upstream of the

pressure control valve.

The off-gases are led by pressure control valve to the quench to the existing scrubber section for further cooling of the off-gases and the separation of the condensed

hydrocarbons.

The uenched off-gases from the uench drum passes through a water seal drum where the temperature of gases is reduced to 9 C. This drum is located on the top of the quench drum.


Water is injected into the drum and a seal is maintained by a gooseneck seal. The off-gases from the water seal drum is routed to the incinerator.

Incinerator The off-gases from the water seal drum is routed to the incinerator through flame

arrestors. Normally one pair of flame arrestors is on the line, the other pair will remain as

standby.

The off-gases then enters the incinerator through four nozzles where it is burnt. The incinerator is a vertical cylindrical type furnace provided with one fuel gas burner.

The box temperature in the incinerator is controlled by a temperature controller, which

resets the pressure indicator controller which in turn regulates the fuel gas pressure to the

burner.

If the fuel gas pressure falls a low-pressure alarm sounds in the control room and the shutdown valve will automatically cut off fuel gas to the incinerator thus eliminating the

possibility of a back fire.

In addition in case of flame failure in the incinerator an ultra violet sensing element will sense it and sound flame failure alarm in the control room and activates the shutdown

valve and shut off fuel gas flow to incinerator.

Bitumen Product Routing The produced product is discharged from the reactor by the product pumps. The

discharge of the product is controlled by the level control and a selector switch is

provided at DCS for selection.

A part of the product leaving the reactor is circulated on the pressure control from the product pumps back to the feed line of the reactor.

The product is led to the steam generator and the bitumen trim cooler will be used to cool the product to a storage temperature.

PROCESS VARIABLES

Temperature As the process is an exothermic one, it is important, that the operating temperature within

the reactor will be tightly controlled. This is accomplished by injecting of process water

into the air pipes.

o As the water vapourizes in the air pipes, it cools the content of the reactor making it possible to maintain precise temperature control.

In principle the temperature in the vapour space of the reactor is at least 50 C less than the bitumen temperature in normal operation.

In case of high temperature in the vapour space, low-pressure steam can be fed into the vapour space for quenching purposes. The quench steam valve is operated by hand and

approached from the ground surface at the steam header of the reactor.

Pressure To prevent an over pressure of the reactor, a rupture disc in combination with safety

valve at the top of the reactor is provided.


The set pressure of the safety valve is related to the design pressure of the reactor. The set pressure of the rupture disc is lower than the set pressure of the safety valve, so that it

will be possible to adjust the correct pressure after bursting of the rupture disc before the

set pressure of the safety valve will be reached.

The normal operating pressure range ends at 90% of the bursting pressure of the rupture disc.

If this percentage is exceeded, the rupture disc will be damaged and may burst under the normal operating pressure.

The burst of the rupture disc is indicated by a pressure gauge with an alarm high signal, located between rupture disc and the safety valve.

Liquid Level The level in the reactor is indicated and controlled by a liquid controller which affects the

level valve in the discharge line of the product.

A redundant level control based on a measurement of a differential pressure of the liquid column in the reactor is provided.

During operation four temperature transmitters, indicating important points of the liquid level, additionally supervise the liquid level.

The level indication is based on the temperature difference between the liquid and gaseous phase.


GUJARAT REFINERY

SECONDARY

PROCESSING

FACILITIES

(GRSPF)


FEED PREPARATION UNIT (FPU)

INTRODUCTION:

Feed P r e p a r a t i o n U n i t ( FPU), a p a r t o f G u j a r a t R e f i n e r y

Secondary Processing Facilities (GRSPF) was originally designed with a throughput of

1.66 MMTPA of RCO. The primary function of this unit was to produce 700,000 T/year of

vacuum gas oil for feed to FCCU along with vacuum diesel and vacuum residue. Later on, it

was decided to revamp the Feed Preparation Unit (FPU) to meet the increased VGO feed

requirement in Fluidized Catalytic Cracking Unit (FCCU), which was also revamped,

to 1.5 MMTPA.

FEED: mixed RCO (MAX)

PRODUCTS: 1. Heavy Diesel 2. Vacuum Gas Oil

PROCESS: The process is same as that for vacuum distillation unit of GRE. Four side draw products are obtained from the column:

1) Heavy diesel is obtained as the topside draw product.

2) Light vacuum Gas Oil (LVGO) is obtained as the second side draw product. The

LVGO pump around is used to generate LP steam after which it is returned to the column.

3) Heavy vacuum gas oil (HVGO) is obtained as the third side draw product. A pump

around reflux is also drawn off at this point. The HVGO product exchanges its heat with RCO

after which it is used to generate LP steam.

4) Slop Distillate is drawn as the fourth side draw product. The re

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