INDUSTRIAL INTERNSHIP REPORT

Extraction Of Valuable Products From LNG

Presented and Submitted By:

Aman Singh
(U22CH062)
Sardar Vallabhbhai National Institute Of Technology
B.TECH. 2022-26, Semester V

Under The Supervision Of:

Shree Parth Sengupta

Department of Chemical Engineering

Sardar Vallabhbhai National Institute of Technology, Surat
Surat-395007, Gujarat, INDIA
 CERTIFICATE

Oil and Natural Gas Corporation

Makarpura Road, Vadodara – 390009
DAHEJ PLANT, BASE

This is to certify that the report entitled ”Extraction Of Valuable Products From
LNG” is presented and submitted by: Aman Singh (U22CH062), B.Tech. 2022-26,
Semester V, in partial fulfillment of the requirement for the completion certificate for
the ONGC winter internship.

In all respects, He has successfully and satisfactorily completed his winter internship
from 10-12-2024 to 9-1-2025. We certify that the work is comprehensive, complete,
and suitable for evaluation.

Shree Parth Sengupta

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Acknowledgement
I express my deepest gratitude to Oil and Natural Gas Corporation Limited (ONGC) for
providing me with the invaluable opportunity to undertake my internship at the Dahej
plant. My experience at this esteemed facility has been essential in gaining practical in-
sights into the extraction processes of C2, C3, and C4 compounds from natural gas, which
has greatly enriched our learning and professional growth. I am immensely grateful to
Mr. A. Hasan, the General Manager, for his guidance, support, and invaluable knowledge
shared during my time at the plant. His expertise and willingness to impart knowledge
have enhanced my understanding of the processes involved. I would also like to extend
our thanks to Mr. Partha Sengupta (Chief General Manager(P)), Shilpa Bhatt(Assistant
Engineer(P)), Ms. Alka Yadav & Ms. Vasundhara for their contributions, suggestions,
and support, which have greatly aided in the successful completion of my internship.
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Abstract
This writing encompasses the observations and the dynamics encountered during my win-
ter internship at the Oil and Natural Gas Corporation (ONGC), Vadodara. The practi-
cal aspect of the internship was concentrated on the organization’s objectives, which are
connected with the oil and gas company’s operation and the technical side, such as the
extraction of valuable products like ethane and propane from LNG and the production
of LPG. To gather the materials, I proactively watched and evaluated the chemical engi-
neering concepts used in essential processes such as Cryogenic operations, P&IDs, Static
LPG blending, and several others. The report also designs potential implementations
of theoretical knowledge in industrial environments, safety measures, and environmen-
tal management. This internship was a good opportunity to obtain my first experience
in the energy sector and develop such competencies as technical, problem-solving, and
professional skills.
 Table Of Contents

Contents

1 Introduction 5

2 LNG Chain 7
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 Overview of the LNG Chain . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Production and Import . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4 Liquefaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.5 Transportation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.6 Storage and Regasification . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.7 Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.8 Infrastructure in Place . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.9 Challenges in the LNG Value Chain . . . . . . . . . . . . . . . . . . . . . 11
2.10 Government Initiatives and Policy Support . . . . . . . . . . . . . . . . . 11
2.11 LNG as a Transportation Fuel . . . . . . . . . . . . . . . . . . . . . . . . 12
2.12 Strategic Reserves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.13 Future Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3 Liquification and Storage 13

3.1 Pretreatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.2 Acid Gas Removal and Dehydration . . . . . . . . . . . . . . . . . . . . . 13
3.3 Remove Heavy Hydrocarbons . . . . . . . . . . . . . . . . . . . . . . . . 13
3.4 Separation and Liquefaction . . . . . . . . . . . . . . . . . . . . . . . . . 13

4 Petronet LNG Limited Dahej 15

4.1 Overview of Dahej LNG Terminal . . . . . . . . . . . . . . . . . . . . . . 15
4.2 Infrastructure and Facilities . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.3 Environmental and Safety Measures . . . . . . . . . . . . . . . . . . . . . 16
4.4 Contribution to India’s Energy Sector . . . . . . . . . . . . . . . . . . . . 16

5 C2-C3 Plant Dahej 17

5.1 Process Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5.2 Feed Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.3 Demethanizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.4 Deethanizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.5 Depropanizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.6 Supply Back To PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.7 Product Storage And Transfer . . . . . . . . . . . . . . . . . . . . . . . . 25

3
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5.8 Hot Oil System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
5.9 Methanol System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
5.10 Other Utilities And Supporting Facilities . . . . . . . . . . . . . . . . . . 28
5.11 Built-in Safety Provisions . . . . . . . . . . . . . . . . . . . . . . . . . . 31

6 Safety Protocols at ONGC 32

7 Conclusion 36
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1 Introduction
Oil and Natural Gas Corporation Limited (ONGC) is an international oil and natural gas
company. PETROLEUM ACT relates to oil exploration, development, and production
of crude oil and natural gas. Its business include Upstream, midstream, downstream, and
marketing and specialty products. The E&P profits prove that the current upstream ex-
ploration is also a component of ONGC’s core investment. Indian-based business company
with the core function of identifying and acquiring oil and gas assets. It has three sub-
sectors of hydrocarbon exploration activities: Deep Water, Shallow Water & Ultra Deep
Water. Exploration activities onshore. Mumbai, headquartered in Maharatna ONGC,
is India’s largest crude oil and natural gas exploration and production company. It will
be reduced by around 71 percent for Indian domestic production. Crude oil is the base
commodity through which almost all finished products are derived. Downstream firms
like IOC, BPCL, HPCL, and MRPL (MRPL is the last two is a JV with BPCL) Pak-
istan International Ltd (Pakistan), Oil & Natural Gas Corporation (ONGC) oil, petrol,
diesel, kerosene, naphtha, and cooking. Gas LPG. The corporation exists under the ego
Ministry of Petroleum and Natural Gas, Government of India, and its primary focus is
on oil and gas exploration in India. India. The business domestically has been organized
into 11 assets, of which 10 are oil. and gas-producing profiles), seven basins (exploratory
profiles), and three plans set at Hazira and Dahej. and Uran) and serving (for raw mate-
rial and assistance like drilling, geophysical, logging, and well services). While at Uran,
essentially crude oil is traded, natural gas is traded at Hazira. one is handled, and the
Dahej plant is the world’s first LNG (Liquified Natural Gas) processing plant.

Figure 1: ONGC group of companies

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Figure 2: Plant location

Figure 3: Dahej Plant On Map

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2 LNG Chain
2.1 Introduction
Liquefied Natural Gas (LNG) represents an integral part of India’s energy mix; it is a
greener alternative to coal and oil to meet the country’s growing energy needs. Due to
its increasing need for energy and strategic pursuits to diversify energy supplies, India
has emerged as a major player in the global LNG market. The LNG chain provides pro-
duction, liquefaction, transportation, storage, regasification, and distribution processes.

Figure 4: LNG supply chain

2.2 Overview of the LNG Chain

2.3 Production and Import
India produces approximately 33 billion cubic meters (BCM) of natural gas annually,
which is insufficient to meet domestic demand. As a result, India heavily relies on LNG
imports, accounting for over 50% of its natural gas consumption. The primary sources of
LNG imports are Qatar (accounting for around 40%), followed by Australia, the United
States, and Russia. India’s major LNG importing companies include Petronet LNG,
Indian Oil Corporation, and GAIL.
 8

Figure 5: LNG import trend

Figure 6: LNG import trend this year

Figure 7: Pie chart for imports in 2021

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2.4 Liquefaction
Globally, liquefaction involves cooling natural gas to -162 degrees Celsius to convert it
into liquid form, reducing its volume by about 600 times. Due to limited natural gas
production, India lacks large-scale domestic liquefaction plants. LNG imported into the
country is sourced from global suppliers with significant liquefaction capabilities, such
as Ras Laffan in Qatar and Gorgon in Australia. Large-scale liquefaction plants have
capacities ranging from 5 to 10 million tonnes per annum (MTPA).

2.5 Transportation
LNG is transported to India via a fleet of specialized LNG carriers. These double-hulled
ships are designed to carry LNG at cryogenic temperatures in insulated tanks, ensuring
minimal boil-off losses during transit. India receives LNG primarily on its western coast
due to its proximity to supplier nations. Typical LNG carrier capacities range between
145,000 and 266,000 cubic meters. Key unloading ports include Hazira and Dahej.

Figure 8: LNG Imports and Exports

2.6 Storage and Regasification

Upon arrival at regasification terminals, LNG is stored in insulated cryogenic tanks. The
regasification process involves heating LNG to convert it back into its gaseous state. India
has five major regasification terminals:

• Dahej LNG Terminal (Gujarat): Capacity 17.5 MTPA

• Hazira LNG Terminal (Gujarat): Capacity 5 MTPA

• Kochi LNG Terminal (Kerala): Capacity 5 MTPA

• Dabhol LNG Terminal (Maharashtra): Capacity 5 MTPA

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• Ennore LNG Terminal (Tamil Nadu): Capacity 5 MTPA

Upcoming regasification projects aim to increase national capacity to 70 MTPA by

2030.

2.7 Distribution
After regasification, natural gas is transported via pipelines and city gas distribution
(CGD) networks. India’s pipeline infrastructure, spanning 22,000 kilometers, is primarily
managed by GAIL, Reliance, and Indian Oil. LNG-derived natural gas is distributed to
industries, power plants, fertilizer units, and households. Transportation also includes
cryogenic road tankers for regions without pipeline access.

Figure 9: Pipelines

2.8 Infrastructure in Place

India’s LNG infrastructure includes:

• Regasification Capacity: Current capacity of 42 MTPA, projected to reach 70

MTPA by 2030.
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• Pipeline Network: 22,000 kilometers, with projects underway to connect under-
served regions such as the northeast.

• CGD Networks: Over 300 districts covered, aiming to supply gas for domestic
cooking, industrial applications, and CNG vehicles.

• LNG as a Fuel: Pilot projects for LNG fueling stations are being implemented
along highways for long-haul trucks.

2.9 Challenges in the LNG Value Chain

High Import Dependency
• India’s reliance on LNG imports exposes it to price volatility in the global market.

• Spot LNG prices have ranged between USD 10 and USD 40 per MMBtu in recent
years, causing consumer affordability issues.

Infrastructure Gaps
• Regasification terminals are concentrated along the western coastline, leaving east-
ern and northeastern regions underutilized.

• Pipeline connectivity remains a bottleneck in expanding access.

Regulatory and Policy Issues

• Fragmented regulatory frameworks and delayed approvals hinder investments.

• Streamlining processes is essential for rapid infrastructure growth.

Price Sensitivity
• Imported LNG is costlier than domestic natural gas and renewable alternatives.

• Subsidies or tax incentives may be required to make LNG competitive.

Technological Barriers
• India lacks indigenous expertise in LNG liquefaction.

• Reliance on imported technology for terminals and carriers increases project costs.

2.10 Government Initiatives and Policy Support

National Gas Grid
• The government aims to develop a 34,000-kilometer national gas grid to provide
equitable access.

• Projects such as the Pradhan Mantri Urja Ganga and the Northeast Gas Grid are
integral to this effort.
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2.11 LNG as a Transportation Fuel
• Government initiatives include promoting LNG as a fuel for trucks, buses, and
ships.

• Pilot projects for LNG bunkering stations have been launched at ports like Cochin
and Mumbai.

2.12 Strategic Reserves

• India plans to develop strategic LNG reserves to mitigate supply disruptions.

• Proposed facilities are planned in Gujarat and Tamil Nadu.

2.13 Future Outlook

The LNG sector in India is poised for substantial growth. Key trends include:

• Expansion of regasification capacity to cater to rising demand.

• Increasing LNG penetration in transportation and shipping sectors.

• Collaborations for technology transfer and domestic manufacturing of LNG infras-

tructure.

• Establishment of small-scale LNG terminals and virtual pipelines for remote regions.
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3 Liquification and Storage
Natural gas is converted to a liquid in a liquefaction plant, or ’train’. An LNG train
performs four main processes:

3.1 Pretreatment
The pretreatment step removes dust and slug (water and condensate), along with hydro-
gen sulfide (H2 S) and mercury (Hg). These pollutants can cause corrosion and freezing
problems, especially in aluminum heat exchangers.

3.2 Acid Gas Removal and Dehydration

Carbon dioxide (CO2 ) is absorbed and removed from natural gas using an amine absorber
(acid gas removal or AGR). Water is removed using an adsorbent. The removal of these
impurities prevents ice formation during the subsequent liquefaction process.

3.3 Remove Heavy Hydrocarbons

Heavy hydrocarbons (C5+ ) are removed by fractionation before liquefaction. Using
propane, natural gas is pre-cooled to approximately -31°F (-35°C), .

3.4 Separation and Liquefaction

Pre-cooled mixed refrigerant (MR) moves through a high-pressure separator, separating
into vapor and liquid streams. Each stream is further cooled, fully liquefied, and sub-
cooled in separate tube circuits within the main cryogenic heat exchanger (MCHE). The
two sub-cooled MR streams are depressurized, further reducing their temperatures. As
the mixed refrigerant vaporizes and flows downward on the shell side of the MCHE,
it provides refrigeration for liquefying and sub-cooling the natural gas. The pre-cooled
natural gas flows through a separate tube circuit in the MCHE, causing it to liquefy and
sub-cool to temperatures between -238°F (-150°C) and -260°F (-162°C). The flash of the
LNG’s end at the MCHE outlet and the receiving LNG storage tank generates flash gas
and boil gas, which make up the fuel gas required primarily by the compression cycles
driven by the propane and MR gas turbines.

Figure 10: Cryogenic working

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Figure 11: LNG Treatment process

Figure 12: Flow diagram for LNG treatment

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4 Petronet LNG Limited Dahej
Petronet LNG Limited, a key player in India’s LNG infrastructure, operates the Dahej
LNG terminal, one of the country’s largest and most advanced LNG import and re-
gasification terminals. The terminal is a critical hub for ensuring energy security and
supporting the nation’s transition to cleaner energy sources.

Figure 13: PLL Dahej

4.1 Overview of Dahej LNG Terminal

• Location: Situated in Dahej, Gujarat, the terminal is strategically located along
the western coastline of India.

• Capacity: The terminal has a regasification capacity of 17.5 million metric tonnes
per annum (MMTPA), making it one of the largest LNG facilities in South Asia.

• Significance: It serves as a backbone for meeting India’s growing energy demand

in industrial, commercial, and domestic sectors.

4.2 Infrastructure and Facilities

• Storage Tanks: Equipped with state-of-the-art LNG storage tanks, each with a
capacity of 148,000 cubic meters.

• Jetty Facilities: Two dedicated jetties capable of accommodating large LNG

carriers, ensuring seamless operations.

• Regasification Units: Advanced vaporization units employing submerged com-

bustion vaporizer (SCV) technology to ensure efficient gasification.

• Pipeline Connectivity: Well-connected to the national gas grid, ensuring unin-

terrupted supply to key markets across the country.
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4.3 Environmental and Safety Measures
• Emission Control: The facility complies with strict environmental standards,
incorporating measures to minimize emissions and environmental impact.

• Safety Protocols: Comprehensive safety management systems and regular audits

ensure safe operations.

• Emergency Preparedness: Equipped with advanced fire and gas detection sys-
tems, water spray systems, and emergency response plans.

4.4 Contribution to India’s Energy Sector

• Energy Supply: Plays a vital role in ensuring a stable and reliable natural gas
supply to industries and power plants.

• LNG Distribution: Facilitates the distribution of LNG for city gas distribution
(CGD) networks and transportation fuel.

• Economic Impact: Supports industrial growth and contributes significantly to

the local and national economy.

Table 1: PLL Import Composition

Components (mol%) Rich LNG Lean LNG Commingled

Nitrogen 0.46 0.47 0.54
Methane 89.79 93.06 91.61
Ethane 6.47 6.06 6.08
Propane 2.23 0.38 1.25
i-Butane 0.42 0.01 0.20
Butane 0.63 0.02 0.31
Pentane+ 0.00 0.00 0.01
H2 S 6 ppmwt max. - -
Total Sulfur 10 ppmwt max. - -
Total 100.00 100.00 100.00

Figure 14: Block Diagram Of PLL

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5 C2-C3 Plant Dahej
ONGC DAHEJ Plant: Key Features and Technologies
• First SEZ Plant: ONGC’s inaugural plant was established in a Special Economic
Zone (SEZ), an industrial zone designed to attract investment, boost exports, and
promote economic growth through tax incentives and relaxed regulations.

• World-First Process Plant: This plant is the first in the world to extract value-
added products, such as ethane, propane, and butane, from liquefied natural gas
(LNG). These products are crucial raw materials for the petrochemical and manu-
facturing industries.

• Core-Flux Cryogenic Process:

◦ State-of-the-Art Technology: Employs advanced cryogenic technology op-

erating at extremely low temperatures to separate and recover valuable hy-
drocarbons.
◦ High C2+ Recovery Rate: Achieves an exceptional recovery rate of over
98% for ethane (C2 ) and higher hydrocarbons (C3 , C4 , etc.), minimizing waste
and maximizing resource utilization.

• Cold Energy Utilization: During the regasification of LNG, significant cold

energy is released. The plant captures and reuses this energy efficiently for cooling
and other energy-intensive processes, enhancing productivity.

• Custody Transfer of LNG: Uses an ultrasonic meter to measure and transfer

LNG custody with high precision, ensuring accountability and accuracy in transac-
tions.

Figure 15: Ultrasonic Flow Meter

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• Air-Assisted Flare System: Introduces air-assisted flare technology as a modern
alternative to conventional steam systems. This reduces steam consumption and
enhances flare efficiency for safer and more environmentally friendly operations.

Figure 16: Air Assisted Flare System

• Feed Tray Technology: Incorporates advanced SCHOEPENTOETER tech-

nology, which improves the performance of feed trays in distillation columns by
efficiently distributing liquid and vapor phases.

Figure 17: Schoepentoeter Technology

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• Green Technology:

◦ No Catalyst Usage and Zero Effluent Discharge: Operates without

catalysts, eliminating the need for hazardous waste management, and has no
liquid effluent discharge.
◦ Low Carbon Footprint: The plant features a low environmental impact,
aided by the Foundation Field Bus system, which enables advanced pro-
cess control and reduced energy consumption.

• High-Capacity Trays: Implements Shell-Sulzer technology, known for its

high-efficiency trays used in separation processes like distillation. This ensures
optimal performance and capacity.

Figure 18: Shell-Sulzer Technology

• Grass Reed Technology: Employs sustainable Grass Reed Technology for

advanced processing, aligning with global efforts toward environmentally friendly
and sustainable operations.
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Figure 19: Grass Reed Technology

Oil and Natural Gas Corporation Limited (ONGC) has undertaken the development of a
C2, C3, C4 The extraction plant is at its site in Dahej, India, adjacent to the existing LNG
terminal owned and operated by Petronet LNG Limited (PLL). The site is approximately
140 km from Vadodara and 63 km from Bharuch by road. It is also located adjacent to
the sea, creating a marine environment.

Figure 20: ONGC Plant Dahej

5.1 Process Outline

The C2/C3/C4 extraction plant consists of one train, whose design capacity is 5.0 MM
TPA (625.0 ton/h) of feed LNG, and provision has also been given for future one-train
 21
expansion of capacity, 4.0 MMTPA. Toyo Engineering Corporation (TEC) has developed
a new cryogenic process for extracting Natural-gas liquids (NGLs; Ethane (C2), Propane
(C3), Butane (C4) and other hydrocarbons) from Liquefied Natural Gas (LNG) is known
as the COREFLUX-LNG Process. Conventional extraction processes involve refluxing in
a Demethanizer column using a portion of the LNG feed. The feed’s presence of ethane
and heavier components limits the extraction efficiency. Conversely, the COREFLUX-
LNG process refluxes with a methane-rich (greater than 99%) stream obtained from
an overhead condenser cooled by the LNG feed. The remaining overhead vapors are
compressed and liquefied in a second condenser, resulting in LNG. Ethane, Propane and
Butane are recovered from the bottom of the Demethanizer column. The design allows
the column to operate at lower operating pressures, reducing reboiler duty.

Figure 21: Process Flow Sheet

5.2 Feed Inlet

Feed LNG (Rich LNG) coming from LNG storage tank in existing LNG facilities at Dahej)
Petronet LNG Limited (PLL) is analyzed for composition and metered for the required
flow rate In the metering skid. LNG feed is then received in Feed LNG Surge Drum,
the liquid of which is pumped up by the LNG Pump (P-1 to Demethanizer column).
The LNG pumping system consists of three pumps, two in operation and one on standby
The operating pressure of Feed LNG Surge Drum is the vapor pressure of Rich LNG at
the receiving temperature (-152*C). In an overpressure situation, the pressure controller
releases excess gas to flare. The level controller controls the liquid level Of D-1105,
 22
regulating the Rich LNG receiving rate.

Table 2: LNG Composition

Components Product Specification (mol%)

Nitrogen 1.4 mol% max.
Methane 85 mol% max.
Ethane 9.2 mol% max.
Propane 3.0 mol% max.
Butane and heavier 2.0 mol% max.
Pentane and heavier 0.25 mol% max.
Oxygen 0.5 mol% max.
H2 S 4 ppmv max.
Total Sulfur 10 ppmwt max.
Total non-hydrocarbons 2.0 mol% max.
Impurities Note 1
Water content Not more than 112 kg/MMSCM

5.3 Demethanizer
The Feed LNG stream first passes through the Demethanizer Overhead Condenser. The
feed LNG provides the required duty for partial condensation of Demethanæer overhead
vapor. The feed LNG is then further heated by compressed Demethanizer overhead vapor
and fed to the middle section of Demethanizer. Lean LNG Compressor, a single-stage
centrifugal compressor, compresses the Demethanizer overhead vapor from the Demeth-
anizer Reflux Drum. Top reflux contains a higher concentration of methane than Feed
LNG, and therefore, a high ethane recovery rate can be achieved Demethanizer fraction-
ates the feed LNG to Lean LNG and C2 & heavier components (C2+ NGL). The required
heat for the side reboiler is provided by circulating pure methanol. Methanol is cooled
from —10.00C to the required operating temperature of methanol (—45*C), which is
then utilized in Deethanizer and Depropanizer overhead condensers. The heat for the
main reboiler is provided by circulating hot oil through the reboiler. C2+ NGL stream
leaving from the Demethanizer bottom is fed to Deethamzer column. The flow rate of
Feed LNG is primarily controlled by the flow controller at the discharge of LNG Pump.
Secondly. Feed LNG is made up to keep the liquid level of Feed LNG Suction Drum. The
compressor performance curve controls the Demethanizer pressure With a fixed discharge
pressure by pressure controller (PIC-1109), In case of overpressure jn Demethantzer. The
pressure controller of the Demethanizer Reflux Drum Will release excess gas to the flare.
Suction throttling valves are provided to reduce the torque of the compressor during
start-up. These valves will be used only for start-up and after the compressor is started.
PIC-1119A/B should be put in MANUAL and set at 100% open position To keep the
quality of Lean LNG, a flow controller will control the reflux rate and the liquid level of
the Demethanizer Reflux Drum will be controlled by a level controller bypass of LV-1103
at the bottom of D-1101 to prevent the Lean LNG Compressor from To maintain the
 23
quality of the demthanizer bottom liquid (C2+ NGL), the temperature of the demetha-
nizer bottom section is controlled by a temperature controller that regulates the reboiler’s
duty. The Demethanizer liquid level is controlled by LIC-1101, regulating the flow rate
to Deethanizer.

Figure 22: Plant Labelled

5.4 Deethanizer
The Deethanizer Column fractionates the C2+ NGL and recovers ethane (C2) as the
overhead product and C3+ NGL as the bottom product. The required heat for the
reboiler is provided by circulating hot oil through the reboiler. Deethanizer column over-
head vapors are condensed in the Deethanizer Condenser. Circulating methanol on the
tube side provides the required condensing duty. The part of the condensed liquid that
contains higher C2 concentration is fed to the top tray of the Deethanizer column as top
reflux, and the remaining liquid is sent to the C2 Product Storage Tank. The Deetha-
nizer bottoms, which contain C3+ NGL, are fed to the Depropanizer column for further
fractionation into propane (C3) and butane (C4) products. The Deethanizer pressure is
controlled by the bypass flow of methanol to the Deethanizer Condenser with PIC-1110
cascading to FIC-1120. In case of the Deethanizer Reflux Drum overpressure, the pres-
sure controller will release vapor to the flare. To keep the quality of C2 Products, Reflux
Drum (D-1102) is controlled by a level controller (LIC-1105) regulating the flow rate of
C2 Product to the tank. To keep the quality of the Deethanizer bottom liquid (C3+
NGL), the temperature of The deethanizer bottom section is controlled by a tempera-
ture controller (TIC-1125) regulating the reboiler duty. The Deethanizer liquid level is
controlled by LIC-1104, regulating the flow rate to Deethanizer.
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5.5 Depropanizer
The configuration of the depropanizer system is identical to that of the deethanizer sys-
tem, which has an overhead. D 1103) and reboiler. The required heat for the reboiler is
given by hot oil, and for the condenser, the required heat is removed by Methanol. The
part of the condensed liquid that contains higher C3 concentration is fed to the top tray
of The depropanizer column is used as the top reflux, and the remaining liquid is sent to
the C3 Product Storage Tank. The Depropanizer column bottoms containing higher C4
concentration are sent to the C4 Product. Storage Tank after cooling down to a storage
temperature of 350C in C4 Product Cooler. The control system is also the same as that
of the Deethanizer System.

Table 3: Product Analysis

Components C2 C3 C4
Nitrogen 0.00 0.00 0.00
Methane 1.50 0.00 0.00
Ethane Min. 95.0 3.50 0.00
Propane 3.50 Min. 95.0 5.00
Butane 0.00 1.50 Min. 95.0
Pentane+ 0.00 0.00 0.00

5.6 Supply Back To PLL

Vapor from Demethanizer overhead is a lean vapor stream (with less quantities of com-
ponents) consisting predominantly of methane. The Demethanizer overhead vapor is
passed through the Demethanizer Overhead Condenser and partially condensed by heat
exchange with feed LNG. Part of the condensed liquid is fed to the top tray of Demeth-
anizer as top reflux, and the balance is sent to Lean LNG Surge Drum as Lean LNG
product. The remaining Demethanizer overhead vapors are compressed by the lean LNG
compressor and totally condensed in the LNG Preheater as a result of exchanging heat
with feed LNG coming from Demethanizer Overhead Condenser. This Lean LNG is then
sent to Lean LNG Surge Drum and is further dispatched together with the condensate
from E-1101 to B.L. using Lean LNG Booster Pumps at the required 100 kg/cm2g pres-
sure. The pressure of the Lean LNG Surge Drum is controlled by PIC-1105 regulating
hot vapor introduction from Lean LNG Compressor discharge. In case of overpressure,
the pressure controller will release excess gas to the flare. The liquid level of D-1104 is
controlled by the level controller cascading to the flow controller at the discharge of Lean
LNG Booster Pumps
 25
5.7 Product Storage And Transfer

Figure 23: Storage Spheres

C2 Product Storage And Transfer

Products from C2/C3/C4 extraction plants are ethane, propane, and butane. Ethane
(C2) is stored at -19.2 *C and 15 kg/cm2g pressure in the storage tank. There are
two spherical storage tanks for ethane. Liquid ethane is pumped by the C2 Product
Pump and sent to the battery limit. Before sending to battery limit ethane is heated
in C2 Product Heater to 5*C by hot oil. Boil-off gas from ethane storage is sent to
the Deethanizer Condenser where it is condensed and returned back to the tank along
with the product ethane. Therefore the ethane storage pressure is always maintained at
Deethanizer pressure.

Table 4: Storage Information

C2 C3 C4
Temperature -19 °C 13.0 °C 35 °C
Pressure 15 kg/cm2 g 6 kg/cm2 g 2.9 kg/cm2 g
Capacity (Metric tonne) 4189 1950 1150
Material of construction Impact tested carbon steel (Insulated) Impact tested carbon steel (Insulated) Carbon steel (Un-insulated)
No. of storage tanks 2 2 2

C3 Product And Storage Transfer

Propane (C3) is also stored in a spherical storage tank at 13*C temperature and corre-
sponding saturation pressure. The number of tanks is two. Liquid propane is pumped
by C3 Product Pump to battery limit. The boil-off gas handling system is identical to
the C2 Storage Tank, where the vapors are sent to the Depropanizer overhead condenser
& returned back to the tank along with the product. The construction material for both
C2 and C3 storage tanks is impact-tested carbon steel and insulated, but the C4 storage
tank is made of carbon steel and is uninsulated.
 26
C4 Product And Storage Transfer
Butane product (C4) is stored in the spherical storage tank at 350C temperature and
2.9 kg/cm2g pressure. The number of tanks is two. Liquid butane is pumped into the
pipeline with the help of a pump.

Figure 24: TTLF For LPG

5.8 Hot Oil System

Demethanizer, Deethanizer, and Depropanizer column reboiler heat is provided by circu-
lating hot oil through the reboiler. The hot oil system consists of a hot oil storage tank,
hot oil expansion drum, hot oil circulation pumps, and hot oil heater. Hot oil is first cir-
culated by Hot Oil Circulation Pumps through a Hot Oil Heater where the temperature
of hot oil rises to 135*C. Low-pressure (LP) fuel gas is used in burners of hot oil heaters.
The hot oil outlet temperature of H-1301 is controlled by adjusting the heater bummer
firing. From the hot oil heater, the hot oil is passed through column reboilers, providing
the required heat duty and then back to the suction of the hot oil circulation pump, thus
completing a closed loop. Part of the hot oil from the circulation pump is used for C2
Product heating in the C2 Product Heater. Any oil drain from the hot oil system is first
stored in the Hot Oil Drain Drum, which is then sent back to the Hot Oil Storage Tank
by the Hot Oil Drain Pump.
 27

Figure 25: Hot oil system

5.9 Methanol System

methanol as a cold heat carrier. This cold heat is then used for condensing vapor in
Deethanizer and Depropanizer overhead condensers also reduce the hot oil duty in the
demethanizer main reboiler, saving fuel and gas consumption in the hot oil heater. Using
methanol rather than glycol water has an advantage from a freezing point of view. The
minimum freezing temperature of 50/50 wt% ethylene glycol water is -33.8*C. which is not
recommendable for use in demethanizer, operated at about -100*C. The methanol system
consists of a Methanol Storage Tank. Methanol Pump, Methanol Circulation Pump and
Methanol Surge Drum, provided with nitrogen blanketing. Methanol is circulated at -
45*C by Methanol Circulation Pump to Deethanizer Condenser from where it passes to
the Depropanizer Condenser and partly to the C4 Product Cooler. After taking heat from
condensers and cooler, methanol flows back to the suction of the Methanol Circulation
Pump, thus completing a closed loop. heated by hot oil in a Methanol Heater. Any drain
from the methanol system is first stored in a Methanol Drain Drum, which a Methanol
Drain Pump sends back to the Methanol Storage Tank.

Figure 26: Methanol System

 28
5.10 Other Utilities And Supporting Facilities
utility and supporting facilities are integral to the C2/C3/C4 extraction unit. The fa-
cilities consist of Flare system, Fuel gas, Instrument and plant air, Nitrogen storage,
Firewater, Raw water & Potable water, Diesel oil, Oily, and Firefighting systems. The
same is described below:

• Flare System: The flare system consists of Flare KO Drum, Flare Stack Package,
and Liquid Drain vaporizer. All safety valve outlets and depressurization lines in
the process and storage area are finally connected to the main flare header, which
is subsequently connected to the flare stack via the flare KO drum. Any liquid that
may come through the flare header Is first separated in the Flare KO Drum during
emergency operations or other circumstances. Then, the separated gas leaving the
KO drum is burnt in the flare stack. To perform smokeless burning, the flare stack
is provided with air-assisting blowers. Provision is also given to measure the flaring
gas flow rate at the flare stack inlet. LP fuel gas is used as fuel for the pilot burners
of the flare stack, and the flare header is continuously purged with LP fuel gas.
All drain liquid hydrocarbon collected in hydrocarbon drain header or the liquid
accumulated in Flare KO Drum is vaporized in Liquid Drain Vaporizer by hot oil
and sent to Flare KO Drum from where it is passed to the flare stack.

Figure 27: Flare System

• Fuel Gas System: Low-pressure fuel gas is required in the C2/C3/C4 extraction
plant and is obtained by partly using gas from Lean LNG Compressor discharge.
Low-pressure fuel is required for Hot Oil Heater and for flare header purging. The
fuel gas is normally supplied from the discharge of the Lean LNG Compressor and
heated to ambient temperature by a Fuel Gas Heater. During start-up, when there
is no hydrocarbon gas in the plant, the fuel gas is taken from the interconnection
 29
line of Rich LNG from PLL. The Rich LNG is vaporized by a Start-Up Rich LNG
Vaporizer and superheated by a Start-Up Fuel Gas Heater. The start-up fuel gas is
also taken from the discharge of LNG Pump (P-1 where higher pressure is available
after the pump is started.

Figure 28: Fuel Gas System

• Instrument Air system : Two Instrument Air supplies the instrument air and plant
air requirement in this plant Compressors. The compressed air from the compressor
is fed to the Instrument Air Dryer Package. Instrument air at the outlet of the air
dryer, which is free of dust, moisture, and oil, is stored in an Instrument Air Receiver
at 8 kg/cm2g, and from there, it is distributed to the entire unit for operation. The
plant air is normally supplied from the compressor outlet when required at the hose
station. However, if compressed air pressure drops to 7.0 kg/cm2g, the pressure
control valve on the service air line will close to secure the source of the instrument
air. Provision of space is also given for future expansion capacity (air compressor,
air dryer, and IA receiver) needed for 2nd train.

Figure 29: Air System

• Nitrogen PSA System: Nitrogen is used in various seals of rotating machines in

the unit. Nitrogen is also used for Blanketing vessel tanks and inertization in the
process & utility area. The nitrogen Package consists of a liquid nitrogen storage
tank and vaporizers. Liquid nitrogen storage of 30 M3 capacity is provided. The
vaporizer at the outlet of the nitrogen storage tank vaporizes the liquid nitrogen; the
nitrogen gas is distributed to the entire plant at a header pressure of 8.0 kg/cm2g.
Nitrogen vaporizer has a capacity of 200 Nm3/hr.
 30

Figure 30: N2 PSA System

• Water System: Raw water is received from GCPTCL through a cross-country

pipeline and is stored in firewater tank and raw water tank. Firewater: A Fire-
water Storage Tank capacity of 14000 m3 is provided. A total of six fire-water
pumps with a rated capacity of 650 m3/hr each and a discharge pressure of 8.8
kg/cm2g have been provided to cater to the fire water requirement in the plant.
Two of the six fire water pumps are motor-driven, and the other four are diesel
engine-driven. Despite that, two motor-driven Fire Water Jockey Pumps with a
rated capacity of 80 m3/hr each are provided. Usually, the jockey pump will be
running continuously Service water/PotabIe Water: Raw water is stored in a Raw
Water Tank. Raw Water Pump then pumps raw water to a water treatment pack-
age where it is treated to remove suspended solid particles and then stored in an
underground Potable Water Sump, For utility purposes, service water is used from
Raw Water Pump discharge. The service water header is kept under pressure by
continuously operating the raw water pump. A Potable Water Pump pumps potable
water from the Potable Water Sump. It is sent to building overhead tanks, which
subsequently are used as drinking water & also used for safety shower/eye washers.
Before sending it to the overhead tank, chlorine is injected into potable water to
make drinking water.
 31
5.11 Built-in Safety Provisions

The C3/C4 truck loading area has advanced fire protection facilities to ensure safe
operations. The provisions include:

• Fixed Water Monitors:

• Two fixed water monitors are installed in the truck parking area outside the
plant boundary wall.
• Another ’water cum foam’ type monitor is provided for the truck loading area,
complying with OISD-144 guidelines.
• These monitors have pick-up tube connections for foam application if required.
• Foam concentrate is stored in foam cam drums that can operate for 30 min-
utes.

• Fixed Water Spray System:

• A fixed water spray system is installed for the truck loading bays, odorizing
skid, and mercaptan shed.
• The system is designed to operate automatically in case of a fire.
• Two deluge valve spray system zones are provided, covering:
• Six C3 truck loading bays
• Four C4 truck loading bays

• Fire Extinguishers:

• Fire extinguishers are installed in the truck loading area as per OISD-116 and
OISD-144 guidelines.

• Fire and Gas Detection and Alarm System:

• A fire and gas detection and alarm system is installed in the truck loading
control room and metering control room buildings.

• Clean Agent Fire Extinguishing System:

• A clean agent (Argonite) fire extinguishing system is installed in the truck

loading control room building, complying with NFPA-2001 guidelines.
 32
6 Safety Protocols at ONGC
The safety protocols at ONGC are designed to ensure the safety and well-being of em-
ployees, contractors, and visitors. Below is a comprehensive overview of these protocols:

Rule No. 1: Protect Yourself with Personal Protective Equipment (PPE)

What is PPE? Personal Protective Equipment (PPE) refers to equipment worn to
reduce exposure to risks and hazards in the workplace. It is designed to protect individuals
from physical, chemical, biological, and other hazards.
Types of PPE:

• Core PPE: Always wear the following essential items:

• Overall
• Safety Shoes
• Helmet
• Gloves
• Safety Goggles
• Ear Plug/Muff

• Specialized PPE: Use as required by tasks:

• Kits and liveries as specified in Material Safety Data Sheets (MSDS)

• Specialized kits for electrical and other jobs

Responsibilities:

• Employees: Wear PPE, follow safety rules, and report any issues.

• Employers: Provide PPE, train employees, and ensure a safe workplace.

• Visitors and Contractors: Adhere to site safety rules and wear PPE.

Rule No. 2: Work with a Valid Permit When Required

Requirements for a Valid Permit:

• Ensure a valid Permit to Work (PTW) is in place.

• Understand and follow the terms of the PTW.

• Ensure equipment is electrically isolated, tagged, and locked out when required.

Safety Checks:

• Fill out the PTW checklist carefully.

• Conduct gas tests for hydrocarbons, oxygen deficiency, and toxic gases.
 33
• Provide ventilation, lighting, and evacuation means in confined spaces.

Supervision and Safety:

• Work must be supervised by an authorized person.

• Suspend work if conditions are unsafe.

• Release interlinked lockouts after completing the job.

Rule No. 3: Ensure Safe System of Work

Requirements:

• Follow Standard Operating Procedures (SOPs) for all operations.

• Conduct Tool Box Talks before starting work.

• Carry out Job Safety Analysis (JSA) for non-routine tasks.

• Use appropriate tools for each job.

• Clearly define and communicate the job, ensuring proper authorization.

Safety Precautions:

• Inspect work areas and ensure safety barriers are in place.

• Assess the impact of tasks on surrounding activities.

• Review safety barriers in case of unplanned changes.

Rule No. 4: Obtain Authorization Before Bypassing Safety Equipment

Requirements:

• Obtain proper authorization before bypassing or overriding safety systems.

• Log all bypasses in the bypass register.

• Implement alternative safety measures for bypassed systems.

• Notify affected personnel of changes in safety systems.

Rule No. 5: No Smoking, Alcohol, or Illegal Drugs

Requirements:

• Smoking is only allowed in designated areas; deposit lighters/matchboxes before

entering operational zones.

• Alcohol and illegal drugs are strictly prohibited in the workplace.

• Report any instances of alcohol or drug abuse immediately.

 34
Rule No. 6: Safe Working at Height
ABCD of Working at Height:
• A: Anchorage – Always anchor yourself.

• B: Body Support – Wear a full-body harness.

• C: Connectors – Connect to a fixed structure.

• D: Descent/Rescue – Ensure lifeline or fall prevention devices are in place.

Additional Safety Measures:
• Secure tools and loose objects to prevent falls.

• Cordon off areas below to protect against falling objects.

• Have a rescue plan ready for emergencies.

• Use escape devices like TEED during emergencies.

Rule No. 7: Safe Handling of Loads

Pre-Lift Checks:
• Ensure lifting equipment is certified and valid.

• Only qualified operators should handle lifting equipment.

• Test safety systems, overloads, and alarms before lifting.

Safe Lifting Practices:
• Identify obstacles in the lifting path.

• Secure the load before lifting.

• Avoid working or walking under suspended loads.

Rule No. 8: No Mobile Phones in Operational Areas

Requirements:
• Deposit mobile phones before entering operational zones.

• Use approved communication devices like walkie-talkies or PA systems.

Rule No. 9: Keep Your Workplace and Environment Clean

Requirements:
• Follow approved waste management policies.

• Dispose of waste in designated bins and keep work areas clean.

• Segregate, store, and dispose of waste properly.

• Organize tools and equipment after use.

 35

Figure 31: Safety Equipments

Rule No. 10: Drive Safely

Before Driving:

• Ensure you have a valid license.

• Conduct pre-trip vehicle checks (brakes, lights, signals, etc.).

• Inspect tyre condition and pressure daily.

Safe Driving Practices:

• Do not drive under the influence of alcohol or drugs.

• Always wear a seatbelt.

• Follow all road safety rules and regulations.

• Avoid using mobile phones while driving.

• Refrain from night driving or driving when tired.

 36
7 Conclusion
The winter internship at ONGC Dahej was critical to gaining insights into the industrial
processes and operations associated with the oil and gas sector. Exposure to real-world
applications of engineering concepts and the opportunity to interact with experienced
professionals greatly enhanced my technical knowledge and practical understanding.
This has given me hands-on experience and the opportunity to observe in-depth the
intricacies of the energy industry regarding process optimization, safety measures, and
environmental issues. In my academic background, this internship enhanced my horizons;
at the same time, it sharpened my problem-solving and analytical skills to meet future
challenges.
In conclusion, interning with ONGC has been a highly enriching experience, covering
the gap between theoretical learning and industrial practice. It has motivated me to
explore further innovations in the energy domain.