A REPORT

ON INDUSTRIAL TRAINING

AT

OIL & NATURAL GAS CORPORATION LIMITED

HAZIRA PLANT, SURAT

Submitted By:-

Shouvik Ash

B.Tech, Electrical Engineering

Institute of Technology, Nirma University

Ahmedabad

Mentor:-

Mr. K.V. Subbarao

C.E. (Electrical)

ONGC, Hazira

ACKNOWLEDGEMENT

I owe many thanks to a great many people who helped and supported me during the

training.

I would also like to thank Training Centre, ONGC, Hazira for providing an opportunity to

undergo training. It was indeed an opportunity for us to visit the different section of

COGEN Plant. During my visit to the company for preparing this Project Report, I learnt many

interesting things about the company

I express my thanks to the Mentor Mr. K.V. Subbarao for extending his support.

My sincere thanks to Mr. S Debroy and Mr. J.K. Golash who provided their valuable

suggestions for the guiding and correcting various section with attention and care. They

also took the pain to go through the visit and give necessary information as and when

needed. I also would like to thank Mr. Shantanu Kar and Mr. N.P. Ahirwar for their

valuable Knowledge.

I would also thank ONGC and their employees without whom this project would have

been a distant reality.

OVERVIEW OF ONGC HAZIRA PLANT

Oil and Natural Gas Corporation Limited (ONGC) is an Indian multinational

oil and gas company headquartered in Dehradun, India. It is a Public Sector

Undertaking (PSU) of the Government of India, under the administrative control of

the Ministry of Petroleum and Natural Gas. It is India's largest oil and gas exploration and

production company. It produces around 69% of India's crude oil (equivalent to around

30% of the country's total demand) and around 62% of its natural gas. It also produces

other value added products such as NGL, C2-C3, Aromatic Rich Naphtha (ARN) and

Kerosene. Internationally its wholly owned subsidiary ONGC Videsh Limited has number

of existing and up-coming interest in selected Oil patches including development of large

gas field in Vietnam Off-shore.

The Hazira Gas Processing Complex or HGPC, Surat is first of its kind in India and Asia’s

largest gas processing facility. It is situated near Bhatpore Village, on Surat-Dumas Road,

18 Km to the western side from Surat Railway Station. The Plant covers an area of 705

Hectares of land; it is situated at the bank of Tapti River connecting Kachchh track pipeline

originating from the south Basin in the off shore Vasai gas field of ONGC Mumbai and

Panna, Mukta & Tapti fields operating under joint venture. About 776 ONGC Employees

and Officers and 1422 contract workers are working inside the Plant. The Plant was set

up in September, 1985. The total facilities which have been installed are Gas Terminal,

Condensate, and Fractionation Units. Liquefied Petroleum Gas Plant, Gas Sweetening

Unit, Unit for Gas Dehydration, Dew Point Depression. Sulphur Recovery Unit, Kerosene

recovery unit and Co-Generation Unit. The Project is set up at a capital investment of Rs.

1337 Crores approx. including Phase-III (A). In view of ageing of Phase-I & Phase-II

facilities (commissioned in 1988 & 1990 respectively) and likely increase of gas

production from ONGC’s Western Offshore fields, as part of Phase-IV of expansion of

Hazira Complex, ONGC has installed Additional Gas Processing Facilities (AGPF

Project).

The plant processes gas coming from the Vasai, South Bassein, Heera, Panna, Mukta

and other fields of the Bombay Offshore region. Initially it was set up to receive sweet gas

from Bombay High, but with time it was seen that there were concentrations of sour gas

coming in the line. Hence the plant was converted into a sour gas plant.

Some of the gas fields in Mumbai offshore are producing sour natural gas containing

poisonous Hydrogen Sulfide Gas (also known as acid gas/sour gas) in varying amount.

Sour natural gas containing H2S require special treatment for removal of the poisonous

gas. HC condensate associated with Sour Natural Gas also becomes sour and gives rise

to production of sour LPG which requires additional treatment for making it sweet,

marketable and safe for use.

Hazira Gas processing Complex is receiving sour natural gas from South Basin Gas

Fields which is a subsea reservoir. The gas is transported from South Basin field to HGPC

through subsea pipelines. The gas is received at Gas Terminal in a slug Catcher where

gas and slug containing HC Condensate, moisture and chemicals (like corrosion

inhibitors) are separated. Gas and associated Condensates are sent further in separate

system for processing.

Places Visited During Training

1. COGEN Control Room

2. Boiler Control Room

3. Steam Generation Unit

4. Power Generation Unit

5. Demineralized Water Plant

6. Electrical Repair Workshop

7. SS-1, SS-4, SS-14

8. Gas Terminal Unit

9. LPG Plant

10. Sulphur Recovery Unit(SRU)

THE PRODUCTION PROCESS

The plant receives gas in 36” and 42” pipelines through 217 km long submarine pipes

from South Bassein to Umbrhat and then 14 km long lines from Umbrhat to the Gas

Terminal. Here gas and any condensates formed are separated. The gas goes to Gas

Sweetening Unit or GSU and the condensate is sent to Condensate Fractionation Unit

or CFU. In GSU the feed gas is freed of hydrogen sulphide and is hence “sweetened”.

The hydrogen sulphide recovered is sent to Sulphur Recovery Unit or SRU, where it is

converted into elemental sulphur and dried into bricks. Commercial production of the

same is not done. Sweet gas is sent to Gas Dehydration Unit or GDU for removal of any

moisture. Product of GDU is sent to the Dew Point Depression or DPD Unit, where the

sweet and dry fuel gas is freed from any condensates, and then is sent for packaging and

dispatch. A part of sweet gas from GSU is taken within the plant and sent to the LPG

recovery unit to obtain LPG and Propane, latter being required for refrigeration within

the plant. The condensate sent to the CFU is separated into Naphtha and Natural

Gasoline Liquid or NGL. The former is packed and dispatched. The latter is sent to

Kerosene Recovery Unit or KRU where value added products like Superior Kerosene

Oil (SKO), Aviation Turbine Fuel (ATF), and High Speed Diesel (HSD) are formed. The

LPG, SKO, and ATF from CFU and KRU are passed through a Caustic Wash Unit to

remove hydrogen sulphide. Additives are added to the same before their packaging and

dispatch. A COGEN unit is also in function to fulfil plant power requirements. Systems of

effluent disposals along with air, inert gas and water supply are also setup. The output of

the plant sustains the HBJ or Hazira-Bijaipur-Jagdispur by supplying fuel gas to GAIL.

Other consumers include IOCL, BPCL, HPCL, RIL, KRIBHCO, NTPC, ESSAR, etc.

PROCESS UNITS

Gas Terminal

It receives & separate sour gas & associated condensate from Offshore.

Gas Sweetening Unit

Removal of H2S from sour gas by selective absorption in Methyl Di- Ethanol Amine.

Gas Dehydration Unit

Removal of Moisture by Absorption in Tri-Ethylene Glycol.

Dew Point Depression

Removal of liquid hydrocarbon by chilling to make it suitable for transportation through

2300 Km long HBJ pipe line without any formation of hydrates.

Condensate Fractionation Unit

Fractional distillation of associated Sour condensate to produce LPG & NGL.

L.P.G Recover Unit

Production of LPG &ARN from sweet Gas by Cryogenic Process

Kerosene Recovery Unit

Fractionation of NGL to produce Naphtha, SKO/ATF &HSD

Cogeneration plant

It produces electric power to drive the plant via three gas turbines.

HGPC ELECTRICAL POWER SYSTEM

To feed the electricity to the entire Hazira Gas Processing Complex and the residential

townships for the employees ONGC Nagar-1, ONGC Nagar-2 and Bachelor’s Colony at

Magdalla, Surat with cumulative requirement to feed approximate 31 MW of Electrical

load, ONGC HGPC is capable of generating 19.2 MW of power at full capacity from the

Co-Generation Plant. This power is fed to the various processing units by the network

of total 17 substations consisting of more than 60 transformers throughout the plant.

The HGPC consist various electrical devices, machines and apparatuses at various

process and utility units. These includes electrical machines like HT motors, LT motors,

EOT Cranes, Illumination and Air-conditioning utilities and other minor apparatuses in

large number of amounts. The regular preventive maintenance and breakdown

maintenance is handled by Field Maintenance Group throughout the year.

Thus, Electrical Power System of HGPC is divided into these three units.

1. COGEN Unit

2. Substations

3. Field Maintenance Group

PRINCIPLE OF COGENERATION

Cogeneration or combined heat and power (CHP) is the use of a heat engine or power station to simultaneously generate electricity and useful heat. Trigeneration or combined cooling, heat and power (CCHP) refers to the simultaneous generation of electricity and useful heating and cooling from the combustion of a fuel or a solar heat collector. A plant producing electricity, heat and cold is called a trigeneration or polygeneration plant.

Cogeneration is a thermodynamically efficient use of fuel. In separate production of electricity, some energy must be discarded as waste heat, but in cogeneration this thermal energy is put to use.

In power systems, use of steam for both power generation and heating. High-temperature, high-pressure steam from a boiler and superheater first passes through a turbine to produce power. It is exhausted at a temperature and pressure suitable for heating purposes, instead of being expanded in the turbine to the lowest possible pressure and then discharged to the condenser, which would waste the remaining energy in the steam. The steam at the higher pressure can provide large amounts of lower-temperature energy for heating buildings or evaporating brine in a chemical plant. Considerable overall energy savings can be obtained by cogenerate

COGENERATION UNIT

The HGPC receives economical, quality and uninterrupted supply of electrical power and

steam from the Cogeneration plant at ONGC, Hazira which was set up in the financial

year (FY) 1987 - 1988. The Cogeneration plant consists of three nos. of Gas Turbine

Generators (GTG) to cater the power demand of Hazira Plant. GT-1 & GT 2, which are

of General Electric (GE) make were commissioned in 1988 and fitted with standard

technology components. GT-3 is of Bharat Heavy Electricals Limited (BHEL) make

was commissioned in 1997 and fitted with up-rated parts.

On the night of 7th August, 2006, unprecedented flood hit the HGPC affecting the whole

plant. Cogeneration plant was badly affected with the flood due to lower elevation and all

the three GTs, Control System and Boiler Auxiliaries were damaged. Among the three

GTs, GT-1 & GT-2 were upgraded post flood at the cost of Rs. 46.51 cr. GT-3 on the

inspection at the cost of Rs. 6.68 cr was found out to be healthy in First major inspection.

The upgraded GT-1 and GT-2 were observed to have an increase in output by 10.6%

and Heat rate reduction by 3.3%.

Why it is called Cogeneration Plant?

o At ONGC, HGPC the exhaust of Gas turbines in CPP (Captive Power

Plant) is utilised for the generation of steam in HRSG boilers.

o Thus the generation of Power and Steam is done simultaneously at the

same COGEN unit to fulfil the Steam and Electricity requirement of ONGC,

HGPC. Thus is called as Cogeneration Plant.

o In addition to Electricity and Steam, DM Water (Demineralised Water) is

also produced at COGEN to feed the boilers for generation of steam and to

the other processing units in HGPC.

Objectives of COGEN:

o To ensure uninterrupted supply of Power and HP, LP & MP Steam to the

process.

o Maximize revenue through export of surplus power in the form of wheeling

to Mehsana Asset & Sale to State Electricity Board.

The COGEN unit can generate maximum of 61.5 MW of Power from the 3 Generator

units coupled with the Gas Turbines. Out of all the Power generated, approximately 28-

31 MW Power is utilised within the HGPC itself. 11.2 MW of Power is exported to

Mehsana Asset through wheeling with State Electricity Board and the rest of the surplus

power is exported to State Electricity Board for Sale.

The COGEN Unit is further divided into 3 major units…

1. Power Generation

2. Steam Generation

3. DM Plant / Water Treatment Plant

Why CPP (Captive Power Plant) Is Required?

o To provide uninterrupted source of power.

o To provide power of required quality & tolerance.

o To provide power at a cheaper cost.

Various Types of CPP:

1. Diesel engine based.

2. Gas turbine based.

3. Steam turbine based.

4. Combine cycle based on 2. & 3.

5. Gas engine based

Advantage of Gas Turbine Based CPP:

o Most reliable & trouble free.

o Quick starting & loading time.

o More compact.

o Cheaper overhauling cost.

o Quality power within minimal tolerance limit.

o Flexibility in use of fuel.

Cogeneration Plant Efficiency:

o Waste heat of gas turbines used for steam generation in HRSGs.

o Open cycle efficiency: 30-35%.

o Combined cycle efficiency: 50-60%.

o Cogeneration cycle efficiency: 80-85%

Major Systems of COGEN Plant At ONGC, HGPC:

o Three Gas Turbines driven Generators.

o HRSGs & Gas fired boilers to meet steam demand of low, medium

& high pressure.

o Demineralisation plant to meet DM water requirement of boilers

and process.

o Two grid feeders at 66 kV level and the 66 kV/11 kV switchyard.

o 11 kV substation for power distribution from cogeneration plant.

Interconnection of Cogeneration & Distribution Network:

o Switchgears & protection system for safe power distribution from 66

kV to 415 V.

o A huge network of steam headers for steam distribution of HP, MP &

LP steam.

o Pipelines of gas, air, fire water, DM water raw water & inert gas.

Equipment Ratings:

Description Make Speed Model Capacity

Gas Turbine #1 GE 5100 RPM MS 5001 19.2 MW

Gas Turbine #2 GE 5100 RPM MS 5001 19.2 MW

Gas Turbine #3 BHEL 5100 RPM MS 5001 19.2 MW

Total Capacity 57.6 MW

Generator:

o Make: GTG-1 & GTG-2: Brush Electrical Machines Ltd.

GTG-3: BHEL

o Capacity – 31.25 MVA, Speed 3000 rpm.

HP/LP Boilers :

UNIT HP CAPACITY

(TONS/HR.)

LP CAPACITY

(TONS/HR.)

HRSG # 1 18.5 105

HRSG # 2 18.5 105

HRSG # 3 50 --

KTI 20 105

Total Capacity 107 315

MP Steam Boiler :

Unit Capacity (Tons/HR.)

IAEC # 1 32

IAEC # 2 32

IAEC # 3 32

THERMAX 37.4

Total 158.4

DM Water Plant Rating:

o Cat-ion exchanger – 03 nos. 80 m3/hr each.

o Weak base anion exchanger – 03 ns. 80 m3/hr each.

o Strong base anion exchanger – 03 ns. 80 m3/hr each.

o Degasser tower, blowers & pumps.

o Mix bed exchanger – 03 ns. 80 m3/hr each.

o DM transfer pumps – 04 nos. 135 m3/hr each.

o DM Water consumption – 1500 m3/day.

Switchyard Ratings :

o 66 kV switchyard with :

04 nos. of MOCBs

02 nos. of 25/31.5 MVA, 66/11 kV transformers with OLTC

Bus PTs

CTs

Lightening Arrestors

GEB Metering System

o Two GEB grid feeders with contract demand of 8 MVA

Two 11 KV bus at Substation-1 with :

o A Bus Coupler

o A reactor connecting both Buses

o Numerous feeders supplying the total load of HGPC through MOCBs.

Power & Steam Demand:

o Average power demand of 30 to 31 MW

o HP Steam demand of 45 - 65 Tons/Hr at 26 Kg/cm2.

o MP steam demand 60 - 85 Tons/Hr at 18 Kg/cm2.

o LP steam demand 140 - 180 Tons/Hr at 6 Kg/cm2

Gas Turbine System and Components:

o Starting system:

Diesel engine

Hydraulic clutch

Torque converter.

o Compressor - 17 stage, axial flow.

o Fuel gas system

o Air inlet system:

Self-cleaning air filters,

IGV

Blow off valves.

o Combustion chambers – 10 nos.

o Turbine - 2 stage

o Lube oil & hydraulic oil system

o Temperature & Vibration monitoring system.

o Gas / fire detection & control system.

o Accessory gear & auxiliaries

o Load gear & generator.

o Water wash & on line cleaning system.

GT Controls-MK V & VI:

o Pre start-up checks & sequencing.

o Start-up, acceleration & shutdown.

o Synchronising & loading of turbine.

o Load & speed control.

o Temperature control.

Gas Turbine Protection:

o High vibration.

o Over speed.

o Fire detection.

o High temperature.

o Loss of flame.

GT Generator System:

o The 31.25 MVA generators have Brushless excitation system.

o Winding temperature monitoring system.

o Generator protection system.

o Rotor earth fault monitoring system.

o Synchronising circuits.

o GTG 1 & 2 - Forced open air cooling system.

o GTG 3 – Closed air – water cooling system.

GTG Operation & Controls:

o In turbine the governor through Mark-V/VI takes care of the load-

frequency control by adjusting fuel flow to the turbine.

o In the generator the AVR takes care of the voltage-reactive power control

by adjusting excitation.

Load-Frequency Control:

o The Gas Turbine can be Operated in Two Modes of governor controls

Isochronous Mode

Droop Mode

o There are basic three load control modes

Pre-selected Load

Part Load.

Base Load governed by temperature Control

Voltage Control – AVR:

o AVR maintains the terminal voltage within the capacity of the generator.

o The AVR also does the protective actions of:

Excitation Monitoring.

Voltage Monitoring.

Excitation Limiting.

Diode failure detection.

Synchronising & Load Shedding:

o The synchronising of all generators and the grid feeders is done at 11 kV

level only.

o The generators synchronising can be done either in Auto or Manually.

o Load Shedding is done whenever there is load-generation mismatch.

o This scheme is operated by frequency sensing.

Generator Protection:

o Winding Temperature Protection through RTDs.

o Overcurrent Protection.

o Voltage Restrained Overcurrent Protection.

o Reverse Power Protection Stage 1 & Stage 2.

o Negative Sequence Current Protection.

o Under Voltage Protection.

o Over Voltage Protection.

o Differential Protection.

o Pole slipping Protection.

o Loss of Field.

o Under Frequency.

o Turbine under Speed trip.

Steam Generation Operation :

o Normally all the 03 HRSGs are run in such a way so as to cater to most of

the HP & LP Steam Demand.

o Minimum load is kept on KTI Boiler & it remains more or less as Hot

Standby for emergency.

BENEFITS OF COGENERATION

Provided the cogeneration is optimized in the way described above (i.e. sized according to the heat demand), the following benefits can be obtained:

Increased efficiency of energy conversion and use

Lower emissions to the environment, in particular of CO2, the main greenhouse gas

In some cases, biomass fuels and some waste materials such as refinery gases, process or agricultural waste (either anaerobically digested or gasified) are used. These substances which serve as fuels for cogeneration schemes, increases the cost- effectiveness and reduces the need for waste disposal. Large cost savings, providing additional competitiveness for industrial and commercial users while offering affordable heat for domestic users also. An opportunity to move towards more decentralized forms of electricity generation, where plants are designed to meet the needs of local consumers, providing high efficiency, avoiding transmission losses and increasing flexibility in system use. This will particularly be the case if natural gas is the energy carrier. An opportunity to increase the diversity of generation plant, and provide competition in generation. Cogeneration provides one of the most important vehicles for promoting liberalization in energy markets.

CONCLUSION

It was a four week summer industrial training program which included field visit of main

units of ONGC, Hazira Plant. I started from cogeneration unit where gas turbines and

water tube boilers were tube boilers were of main interest. Next was the utility & offset

unit where storage units of by products were observed and studied. Also compressors

of three classes; Reciprocating, centrifugal and screw type were studied and

performance of those three was compared. I learned about the various process in in the

Cogeneration plant .Further, I came across GSU, GDU, LPG, KRU, SRU units, D.M.

plant, cooling tower, reciprocating compressors (in DPD, CFU) i.e. how these worked,

what were the requirements of these in the process flow of that unit and also how these

were maintained and required after excessive usage.

I did enjoy learning new things and had an excellent exposure to the industrial world

through this summer training. I have discussed about the gas turbine and boilers in

detail including whatever possible facts and figures. With this I conclude my report.