Introduction oil production and cannot be recovered.

During the flaring of gasses, these are mixed

Anthropogenic activities like burning and
with air and are burnt in the flare system to
production of fossil fuels has made the world
produce water vapours and carbon dioxide.
to face the climate change and this change has
This burning of fumes and can be equalized of
completely disturbed the weather patterns and
burning of liquefied of petroleum gas (LPG).
has affected the nature badly. In an oil
production industry, flaring is the one of the Types of Flares by Operation
most visible forms of the waste Capturing the
Process Flaring
flared gasses is not only beneficial for the
environment, but it has economic incentives as Process flaring is the controlled combustion of
well. The World Bank Introduced the ‘Zero gas produced during industrial processes. It is
Routine Flaring by 2030’ goal which is the frequently practiced across industries
baseline for our objective to reduce gas flaring including oil and gas and chemical production.
and recover these gasses. This project It is put into place for safety and legal
discusses the impact of flared gasses on compliance, and it stops dangerous gasses
environment, technologies to recover the from direct escaping to the environment.
flared gasses and its environmental, economic,
and social issues related to the flare system Emergency Flaring
and benefits of its recovery. The controlled combustion of gases in
Background Knowledge industrial facilities, especially those in the oil
and gas industry during unanticipated or
Overview of Refinery emergency conditions is known as emergency
flaring. In order to avoid potential risks, this
An oil refinery is an industrial process plant
safety precaution is used to quickly and
where crude oil which is extracted from
properly dispose of surplus or undesired gases.
ground is refined to into useful petroleum
By preventing unintentional discharges of
products such as gasoline, distillates like diesel
potentially hazardous gases, emergency flaring
fuel, heating oil and jet fuel petrochemical
reduces the possibility of explosions or other
stock, waxes, lubricating oils and asphalt.
unfavourable events.
Most of refineries ten to produce oil used in
transportation industry. In 2016, approximately Production Flaring
50% of the refineries produced the gasoline
and distillate fuels which are consumed in The intentional burning of associated gases
transportation. An oil refinery operates in produced during the extraction and processing
simple three steps: separation conversion and of oil and gas is known as production flaring.
treatment. In the separation process, the Production flaring is generally related to the
vapours and liquids get separated into extraction of oil, is practiced when there is an
petroleum products based on their boiling excessive number of associated gasses that
points. The heavy fraction such as asphalt and cannot be utilized effectively. When
fuel oil get separated from the bottom of infrastructure is insufficient to handle the gas
column. In the final step products are blended or in case of maintenance handling of
and treated to meet the market standard equipment, needs a call for pressure release
requirements. temporarily and under controlled situations it
addressed by production flaring.
Importance of Flare System
Problem Statement
Flare is an important safety device utilized in
refineries and oil production facilities. This is A critical and prolonged issue facing the oil
also used in emergency and startup or shut industry that dates back 160 years is the
down situations. Flares are used to burn ongoing systematic flaring of associated gases
associated hydrocarbons produced during the during oil production. A significant amount of
associated gas is still flared despite of the as those for stabilization, distillation, sulphur
commendable efforts from governments and recovery, dehydration, treating sour gas, and
oil corporations to invest in the capture and auxiliary services. Northwest to southeast
conservation of these gases. Technological, winds dominate the local climate in this area
legal, and financial limitations possess hurdle for around 90% of the year, especially at the
to this process. The alarming annually burning gas processing complex. Throughout the next
of 140 billion cubic feet of natural gas around months, the wind pattern changes, blowing
the globe can be exemplified by the release of from the southeast to the northwest [10]. This
300 million tons of CO2 which is contributing seasonal pattern suggests that for around 10%
to climate change, and this flared gas by itself of the year, workers are at an increased risk of
is 28 times stronger greenhouse gas with being exposed to hazardous gasses. Wind rise
devastating effects on environment and this diagrams were used to determine the direction
gas can serve as the breeding ground for of the predominant wind and to shed light on
climate change. Moreover, associated gas the usual distribution of wind speed and
release causes carbon emission, impacting the direction. Specifically, wind blowing from 160
environment with the release of black carbon degrees transports harmful gasses during the
and many other pollutants. In addition to 10% of the year that has been classified as
making the world’s environment problems potentially dangerous for workers. Under these
more and more complex this ecological circumstances, the dormitory—which is 200
damaging process wastes a significant amount meters long and 1050 meters away from the
of energy source. There is possibility of flare stack—becomes very vulnerable.
generation of 750 billion kWh (UN Employees exposed to unacceptable
Environment Program, 2105) of electricity concentrations of these chemicals may be at
which is more than the electricity consumption risk for health problems because of the choice
in whole Africa. The flaring not only affects to release dangerous gasses for an hour.
the climate but also the gas’s economic
A comprehensive strategy, including improved
promise as a catalyst for the sustainable
safety precautions, ongoing air quality
development has not been fully realized,
monitoring, and the creation of strong
representing a missed opportunity for
emergency response plans, is needed to
developing countries to advance both socially
address this problem. To reduce the impact on
and economically.
workers' health and safety, the facility must put
The Zero flaring goal to be achieved by 2030, employee welfare first, put effective mitigation
led by the World Bank, seeks to address these techniques into place, and follow all applicable
problems by making oil companies and environmental and safety laws.
governments to sit on one table and make
1-Hazard Identification
collaborative efforts to bring an end to this
wasteful and environmentally harmful The study and calculation of the harmful gases
practice. The problem seeks urgent attention considered during the one-hour release period
and action to mitigate the environmental was done for two different flaring conditions:
impacts caused by the gas flaring and harness
this valuable energy source for the well-being Flare flame out: where the gas of concern is
of environment and humanity. H2S.
Normal flaring: where the gas of concern is
SO2.
Environmental Risk Assessment of
Hydrogen sulphide, or H2S, is a very
Site Specification poisonous and dangerous substance.
Colourless and combustible, H2S is
The plant is a gas processing facility that uses
distinguished by its distinct smell like rotting
local sources of gas and is in a semi-arid area.
eggs. Slightly greater quantities of H2S may
The plant is divided into many sections, such
irritate the upper respiratory tract, low doses of concentration of pollutants absorbed over a
20–150 ppm H2S induce eye irritation, and certain period by human or ecological
continuous exposure may cause Pulmonary receptors. The process of assessing exposure
Edema. The irritating activity has been involves many stages, such as defining the
explained by the formation of sodium exposure environment, determining the
sulphide, a caustic, when H2S reacts with the exposure pathways, and calculating the
alkali found in wet surface tissues. Olfactory exposure level.
fatigue causes odour to become impressible
when the concentration gets closer to 100 ppm. Compositions flow Molar
(kmol/h) percent
At these concentrations, the gas interferes with
(%)
the process of cellular respiration and may
Methane 1059.40 87.42
result in severe respiratory depression and Ethane 5.66 0.46
arrhythmias in the heart 200 ppm is a very Propane 1.28 0.10
dangerous number that can instantly pose a I-Butane 0.37 0.03
threat to life. After 30 minutes at 500 ppm, N-Butane 0.61 0.05
symptoms include headache, vertigo, N-Pentane 0.34 0.02
excitation, stumbling, and gastrointestinal N-Hexane 0.27 0.02
issues. In rare instances, bronchitis or Carbon dioxide 2.68 0.22
bronchial pneumonia ensue. By respiratory Hydrogen 100.63 8.34
paralysis, concentrations over 600 ppm can be Sulphide
lethal in 30 minutes. Nitrogen 40.50 3.34
Moreover, SO2 is a colourless gas with a
burned match scent. It may be reduced to The inhalation rates are taken from the USEPA
sulphur trioxide, which easily changes into that were used, considering both slow and
sulphuric acid mist when water vapor is quick activity levels. In ideal circumstances,
present. Acute exposure to 5 ppm of SO2 may employees are on the job site for 12 hours, but
result in a severe increase in resistance to in the worst situation, they can be there all day.
bronchial air passage as well as dryness of the There are some employees that miss work on
nose and throat. Tidal respiration capacity weekends, for a total of 96 days annually. To
decreases when SO2 levels rise to 6 to 8 ppm evaluate possible lifelong carcinogenic
and at 10 ppm, coughing, sneezing, and eye consequences, an average exposure length of
discomfort happen. After less than 30 minutes 70 years was anticipated.
of exposure, a SO2 concentration of 20 ppm
may produce bronchospasm, while 50 ppm
causes severe pain but no harm. Lastly, Factors Values Worst Case
breathing in 1000 parts per million for longer Scenario
than ten minutes results in death [15]. Table 1 Inhalation rate 0.72 3.06
shows the concentrations of H2S and SO2 (m3/h)
under the two distinct scenarios taken into Exposure time 12 24
consideration in this modelling scenario. It is (h/event)
believed that during typical flare, H2S is Exposure 269 365
totally oxidized. frequently
(events/yr.)
2-Exposure Assessment. Exposure 70 70
duration (yr)
Public knowledge of environmental concerns carcinogenic
has significantly increased recently, and Exposure 70 70
concern about how environmental variables duration (yr)
affect human health has grown. In this context, carcinogenic
exposure assessment is important since it
involves estimating the amount or
The following formula was used to determine Cair × IR × ET × EF × ED
CDI of Inhalation=
the dosage resulting from the breathing of each BW × AT
metal, which represents the intake of
carcinogens: 5 mg 24 365 day
× × ×35 year
L day year
=
365 day
70 kg × × 70 year
C × CR× ET × EF × ED year
Exposure by Inhalation= =0.8571mg/kg-day
BW × AT
I is the chemical intake (mg/kg d) Step-2(Calculated HI)

C is the chemical concentration (mg/m3) mg

0.08571(−day)
CDI kg
CR is the contact rate (m3/h) HI = = = 10.91
RFD mg
0.078( −day )
ET is the exposure time (h/day) kg
EF is the exposure frequency (day/year) For Carcinogenic

ED is the exposure duration (years) Step 1 (calculated CDI)

BW is the body weight (kg) Cair × IR × ET × EF × ED

DI of Inhalation=
BW × AT
AT is the averaging time (days)
=
Dose Response Assessment.
0.5 mg 2 l 350 day
× × ×35 year
A critical element in the risk assessment L day year
process is dose-response assessment, which 365 day
establishes the relationship between the 70 kg × ×70 year
year
likelihood and seriousness of negative health
consequences on humans from exposure to =0.006849 mg/kg-day
different concentrations of risk agents. The
Step2(Calculated Cancer Risk)
reference concentration (RFC) is used to
assess the dangers of inhalation, where Cancer Risk = CDI × Slope Factor
"concentration" refers to the amounts of
pollutants in the air. When it comes to = 0.006849 (mg/kg-day) × 0.85 (mg/kg-day)-1
carcinogens, the risk at various exposure levels = 0.005822
is estimated using the Slope Factor (SF),
which is the slope of the straight line that Step 3 (calculated No. of extra cancer per
connects dosage and response. The RFCs and millions of people)
SFs used in this modelling scenario are
described in the following . No. of extra cancer per millions of people =
Cancer Risk x 106
Compound Reference Slope Factor =0.005822 x 10 6

Dose (mg/kg/day)-
(mg/m3) 1 =5821.918 per million at risk of cancer
H2S 0.002 0.021
Step 4 (No. of extra men at cancer risk per
SO2 0.078 -
year per million)
No. of extra men at cancer risk per year per
Risk Characterization
million=
Calculation. No . of men at cancer risk per miliion
70 years
Step-1(Calculate CDI)
 5821.918 Total BTUs
=
70 flare per 697834.5 MMBTU/Year
year
=83.17025 people at cancer risk per year per
million CAD/
Fuel Gas MMBTU
Economics Impact: 2.7
Price (Albera.Ca,
The economic implications are linked to the n.d.)
need to import an extra quantity of energy Total losses
equivalent to the energy of flaring gases. By in flaring 1,884,153 CAD/Year
harnessing the energy inherent in the flare the gas
gases, substantial cost savings can be
achieved, particularly in terms of fuel gas
expenditures.
To offset this energy loss, the plant is
compelled to procure additional energy at a
rate of 2.7 CAD/MMBTU, representing the
heating Value average cost of fuel gas. This translates to an
contribution annual expense of 1.9 million CAD. This
Compositions (BTU/SCF) constitutes a noteworthy cost that could have
(EnggCyclopedia, been preserved annually through effective
n.d.) energy utilization.

Methane 884.69 Carbon Dioxide Emissions:

Ethane 8.2018 CH4 + 2O2  CO2 + 2H2O

Propane 2.557 C2H6 + 7/2 O2  2CO2 + 3H2O

I-Butane 1.0062 C3H8 + 5 O2  3CO2 + 4H2O

N-Butane 1.6845 C4H10 + 13/2 O2  4CO2 + 5H2O

C5H10 + 15/2 O2  5CO2 + 5H2O
N-Pentane 0.8018
C6H12 + 9 O2  6CO2 + 6H2O
N-Hexane 0.95118
The aforementioned combustion reactions
Hydrogen
56.0448 have been provided, and the resultant
Sulphide
production of carbon dioxide is calculated and
Total 955.93768 detailed below.

Based on the above data, annual losses are

calculated in terms of energy loss by flaring
gases. Moles of
Componen Flowrate
CO2
Parameter Value Units t (Kgmoles/hr)
(Kgmoles)
Flow Rate Methane 1059.4 1059.4
of the Flare 56.02 m3/hr
Ethane 5.66 11.32
Gas
Propane 1.28 3.84
Total BTUs I-Butane 0.37 1.48
flare per 1911.9 MMBTU/Day N-Butane 0.61 2.44
Day N-Pentane 0.34 1.7
 The flare gas recovery system holds significant
N-Hexane 0.27 1.62 importance due to its role in mitigating
Carbon environmental impact and maximizing
2.68 2.68 resource utilization. This system captures and
dioxide
Total 1070.61 1084.48 processes gases that would otherwise be flared
Total CO2 Emission per during industrial operations. Its process
418002 involves collecting, compressing, and treating
year (Tons per year)
these gases to convert them into usable energy
or products, reducing emissions and
Upon assessing the potential issues arising environmental harm while harnessing valuable
from gas flaring, it becomes evident that resources that would otherwise go to waste.
addressing this problem necessitates an
alternative and sustainable approach for The flare gas recovery system involves several
resolution. key steps:
Gas Collection: Flare gas, which typically
consists of hydrocarbons and other gases, is
collected from various industrial processes
Significance Assessment Matrix instead of being released into the atmosphere.

Industries globally utilize a significance Compression: The collected gas is

assessment matrix to identify process steps compressed to increase pressure, facilitating its
that bear a significant impact on quality, movement through the recovery system.
environmental, occupational health, economic, Treatment: The gas undergoes treatment
or societal risks. While sustainability considers processes to remove impurities, contaminants,
triple bottom lines, our focus is specifically on and unwanted components. This treatment
assessing the notable environmental risk posed often involves separation techniques to isolate
by the flaring process. There are diverse valuable gases from waste or harmful
qualitative and quantitative methods to substances.
determine this significance, following outlined
guidelines presented in Table 4. The outcome Conversion or Utilization: The recovered
confirms that flaring significantly impacts the gas can be converted into usable energy, such
environment, indicating a substantial burden as electricity or heat, through combustion or
on environmental well-being. other energy generation processes.
Alternatively, it may be utilized as feedstock
Environmental factors categorized as minor, for other industrial processes, reducing the
low, medium, and high receive scores ranging need for new raw materials.
from 1 to 4, respectively.
Distribution or Storage: Once treated and
Environmental effects that surpass a specified processed, the recovered gas is either
threshold, beyond legislative requirements, distributed for immediate use or stored for
and possess a significance value of 54 or future consumption or sale.
higher are deemed significant, as determined
by the subsequent formula. Emission Reduction: The primary aim of the
flare gas recovery system is to significantly
Frequency × Severity × Duration × Area/Scale reduce or eliminate the flaring of gases,
thereby minimizing harmful emissions and
environmental impact.
A Sustainable Solution:
Compressor Design:
Flare Gas Recovery System:
Compressor design for power requirements is
a meticulous process focused on achieving
high efficiency by balancing pressure ratios,
airflow rates, and mechanical design. This
optimization aims to minimize energy
consumption while ensuring the compressor
delivers the necessary output, incorporating
principles of thermodynamics and
aerodynamics for efficient power utilization.
Knock-Out Drum Design:
In a flare gas recovery system, the knock-out
drum holds paramount importance as it serves
as a crucial component for separating liquid
hydrocarbons or contaminants from the gas
stream before further processing. This
separation is vital to prevent downstream
equipment from being damaged by liquid
carryover, ensuring the efficient operation of
subsequent processes. By effectively removing
liquids, the knock-out drum safeguards
downstream compressors, pumps, and other
equipment, reducing maintenance
requirements and enhancing the overall
reliability of the flare gas recovery system.
 Fluid characteristics
Gas name - Flare Gas
Gas molar mass g/mol 18.61
Gas isentropic coefficient - 1.31
Compressor mass flow capacity
Gas Flow rate m3/h 56.1
Reference temperature c 0
Reference pressure Pa 101325
Gas Density Kg/m3 1.02
Air mass flowrate kg/s 5.1
Compression required
Target discharge pressure bar g 7
Suction pressure bar g 0.43
Suction temperature c 20
Efficiency of compressor - 0.72
Isentropic coefficient or polytropic coefficient - 1.31

Power requirement calculation

Discharge temperature K 439.8
c 166.7
Isentropic power W 412000
kW 412
Actual power required kW 572

Knock out Drum Design:

Equipment Knock out Knock Out Units

drum Drum
demister Mesh type Mesh Type -
Maximum velocity 1.3 m/s
Area 2.4 m2
length 3 m
diameter 0.3 m

Performance Indicators:

Ssustainable Flare Gas Recovery System Conventional Flare System

Indicators
Emissions Effectively captures and repurposes Releases flared gases directly into
Reduction flared gases, reducing emissions of the atmosphere, contributing to
methane, CO2, and other pollutants greenhouse gas emissions and
into the atmosphere. environmental pollution.
Resource Recovers valuable hydrocarbons for Wastes valuable gases, resulting in
Utilization reuse, reducing waste and maximizing economic losses and inefficient
resource efficiency. utilization of resources.
Environmental Minimizes environmental impact by Contributes to environmental
Impact reducing air pollution and mitigating pollution, impacting air quality and
the greenhouse effect through gas potentially exacerbating climate
capture and utilization. change.
Energy Enhances energy efficiency by Wastes energy resources by flaring
Efficiency harnessing captured gases for energy gases without utilizing their energy
 production or industrial use. potential.
Regulatory Complies with environmental
May face challenges in meeting
Compliance regulations and supports sustainable environmental regulations and
practices by reducing flaring activities.
sustainability goals due to
uncontrolled gas flaring.
Economic Provides economic benefits by Incurs economic losses by wasting
Viability recovering and repurposing gases, valuable gases and missing
leading to potential cost savings and opportunities for revenue generation.
revenue generation.