NAGARJUNA FERTILIZERS & CHEMICALS LTD.,

NAGARJUNA FERTILIZERS & CHEMICALS LTD., KAKINADA

RISK ANALYSIS REPORT OF

CUSTOMISED FERTILIZER GRANULATION PLANT

RAMS SAFETY CONSULTANTS 4/1, Parsn Reveira,

4TH Main Road Extension Kottur Gardens,

Chennai - 600 085 Phone : (044) 2447 1166

Mobile- 98400 78043 E.mail [email protected] : [email protected]

CONTENTS SL.NO. TITLE PAGE NO

Preface

i

Profile of Rams Safety Consultants

ii

Profile of the Specialists

iii

Executive Summary

Vi

1.0

NFCL Profile

1 - 1

2.0

Scope, Objective and Methodology

2-1

3.0

Data For Risk Assessment

3 - 1

4.0

Maximum Credible Accident Scenarios

4 - 1

5.0

Consequence Analysis

5 - 1

6.0

Failure Probability

6 - 1

7.0

Risk of Auto Ignition, Risk of Chemicals Under Production, Handling, Storage and Transportation, Risk due to Electrical Short Circuiting or any Other Source, Threats from the Existing Plants

7 - 1

8.0

Conclusion & Recommendations

8-1

PROCESS SAFETY

TRAINING

ii

PROFILE OF RAMS SAFETY CONSULTANTS

Started in 1985, Rams Safety Consultants (RSC) is one of the earliest safety

consultancy firms established in India to meet the specific demands of the industries in

the area of safety services. RSC consists of a group of dedicated professionals having

vast industrial experience with specialized knowledge in their respective fields.

RSC has successfully carried out more than 300 Safety Audits, 70 Risk/Consequence

Analysis Studies, 70 Hazop Studies and a number of Process Safety Training

Pogrammes all over India.

Services provided by RSC

RISK ANALYSIS/QRA

RSC HAZOP STUDY

SAFETY AUDIT

INSPECTION

ELECTRICAL SAFETY AUDIT

PREPARATION OF EMERGENCY PLANS

OHSAS 18001 &

ISO 14001 Systems

Implementation

iii PROFILE OF THE SPECIALISTS

1. SHRI.R. RAMADORAI Qualifications: B.E. (Chemical) Work Experience: Eight years of process experience followed by

18 years as Head of the Department of Safety and Fire in Fertilizer Corporation of India (FCI) Ltd.

Since 1984, working as freelance safety consultant and also heading Rams Safety Consultants. He has carried out Safety Audits, HAZOP Studies and Risk Analysis for a large number of industries all over India. He has conducted a number of safety training programmes all over India in chemical, petrochemical and fertilizer industries. He had been to Turkey as UNIDO Safety Expert. He has presented a number of papers in India and abroad.

He was a member of State Level Safety Task Force / Expert Committee of Government of Tamilnadu.

He was nominated as Member of Board of

Governors of National Safety Council to represent Public Sector Undertakings

iv

2. SHRI. P.V. RAGHAVAN Qualification: B Sc (Chem)

Work Experience: Over 30 years of experience in the commissioning and operation of the following plants in the fertilizer industry:

1. Air Separation 2. Water Treatment 3. Ammonia Was formerly a Chief Engineer in the Fertilizer Corporation of India. He is with Rams Safety Consultants for the last 18 years and during this period has carried out a number of Safety Audits, Hazop, and Risk Analysis Studies.

v

EXECUTIVE SUMMARY

Nagarjuna Fertilisers & Chemicals Limited (NFCL) is located in Kakinada, East

Godavari District of Andhra Pradesh. The NFCL complex consists of two ammonia

and two urea plants. The ammonia plants are based on Haldor Topsoe Technology

and urea plants on Snamprogetti, total recycle with ammonia stripping. The feed

stock of plant I is natural gas. and plant II, which was on mixed fuel (60 % naphtha

and 40 % natural gas), has been switched over to natural gas. The shortage of CO2,

is made up from a 450 MTPD Carbon Di Oxide Recovery Plant from the flue gases

of Ammonia Plant I Primary Reformer stack. The production capacity of each stream

of ammonia plant-I & II is 1325 MTPD & 1300 MTPD and urea-I & II is 2325 MTPD

& 2280 MTPD. Other associated offsite and utility plants are available. NFCL is setting up a 400 MTPD capacity Customized Fertilizer Granulation (CFG) Plant. This plant would be put up inside the existing complex. NFCL desired to carry

out Risk Assessment Study of the proposed customized fertilizer granulation plant to

cover risk of auto ignition, risk of chemicals under production, handling, storage and

transportation, risk due to electrical short circuiting or any other source, threats from

the existing plants, and the consequence analysis of the NG line to the plant

mentioned above, among other things.. .Rams Safety Consultants (RSC) of Chennai

was assigned the job.

Results of the analysis

Risk of Chemicals Under Production, Handling, Storage and Transportation

The materials stored, handled and mixed is thermally stable at normal working

conditions during storage and transport. The materials do not have the

tendency for auto ignition based on their chemical characteristics. They will

not get ignited due to normal ignition sources and heated metals. So there is

no possibility of fire taking place in the storage area due to auto ignition, hot

work etc., and leading to emission of toxic gases from the stored materials.

vi

The available literature does not mention about any evolution of toxic gases to

that extent that it needs dispersion/consequence modeling.

Use of recommended PPE in handling these materials would go a long way in

minimizing handling accidents.

Risk Due To Electrical Short Circuiting

Short circuits occur mainly due to overloading as it leads to heating effect and

may result in fire breakout and fatal accidents, if proper instructions are not

followed. Such incidents can be minimized to a great extent if adequate fire

precautions are observed. Electrical fires spread rapidly and cause loss of

lives and property.

Threats from the Existing Plants

The CFG Plant is to the west of existing cooling tower of ammonia plant II and

north west of urea plant II cooling towers. Any release of chlorine from the

cooling towers might affect the personnel in this plant subject to the direction

of the wind.

Similarly any major ammonia release from ammonia and / or urea plants

might have an effect on the personnel working in CFG Plant, again, subject to

wind direction.

vii

Guillotine Failure of the NG Line to HAG Burner

The Jet fire ellipse radiation levels and the furthest distance of flash fire would

be confined to the factory premises.

Sl. No

Scenario Wind Velocity / Stability

Damage Distance (m) Radiation Level Jet Fire Ellipse

Flash Fire Envelope

37.5 kW / m2

12.5 kW / m2

4 kW / m2

Furthest Extent 21716.9 ppm


1

2” NG line to HAG rupture

3 B 9.94 10.50 11.85 7.81 5.17

3 D 10.26 10.68 12.0 7.84 5.15

5D Not Reached

10.78 12.26 6.56 4.70

Specific Recommendations Special attention in terms of inspection and safety management systems for

NG line is suggested.

Hydrocarbon detectors may be suitably located in critical areas with means of

prompt isolation.

Electrical Short Circuiting

The recommendations made below, if followed might obliterate fires and

consequent damages due to electrical short circuit

The lighting fixtures in the NG routing and HAG area should conform to the

standards suitable for service in that area and once installed must be

maintained.

Use only ISI certified appliances.

viii

Use good quality fuses of correct rating, miniature circuit breakers and earth

leakage circuit breakers.

Use one socket for one appliance.

Switch off the electric supply of the fire affected areas.

Fuses and switches should be mounted on metallic cubicles for greater safety

against fire.

Replace broken plugs and switches.

Keep the electrical wires away from hot and wet surface.

Don’t use substandard fixtures, appliances.

Never have temporary or naked joints on wiring.

Don’t lay wires under carpets, mats or doorways. They get crushed, resulting

in short circuiting.

Don’t lay wires under carpets, mats or doorways. They get crushed, resulting

in short circuiting.

Don’t allow appliances cords to dangle.

Don’t place bare wire ends in a socket.

No combustible material should be permitted to be stored in the plant

ix

Threats from the Existing Plants With the current predictive and preventive maintenance practices and testing

and calibrating procedures, the possibility of major release of hazardous

chemicals from the existing unit appears to be very remote.

Mock drills should be conducted posting observers. Pamphlets may be issued

to all the employees detailing how to respond in case of an emergency.

NFCL Customised Fertilizer Granulation Plant, Kakinada

RIsk Assessment 2011

Rams Safety Consultants NFCL Profile

1-1

1.0 NAGARJUNA FERTILISERS & CHEMICALS LIMITED - PROFILE

1.1 Location

Nagarjuna Fertilizers & Chemicals Limited (NFCL) is located at Kakinada,

East Godavari District of Andhra Pradesh. The total area covered by the

NFCL plant is about 380 acres. It is situated about 500 meters from the

coast just next to Kakinada bay. The site is about 2.5 m above mean sea

level. It is surrounded on the north by Coromandel Fertilizers Limited, Bay

of Bengal on the East, Kakinada town on the west and green belt on the

south. The width of the green belt is 1 km wide and it also extends on the

west. Incidentally the green belt is between the plant and the town. The

site plan is enclosed as Figure 2.1 1.2 The Fertilizer Complex

The NFCL complex consists of two ammonia and two urea plants. The

ammonia plants are based on Haldor Topsoe Technology and urea plants

on Snamprogetti, total recycle with ammonia stripping. The feed stock I is

natural gas. To make up CO2 short fall due change over from naphtha +

NG to NG, a 450 MTPD Carbon Di Oxide Recovery Plant from the flue

gases of Ammonia Plant I Primary Reformer has been put up. The

production capacity of ammonia plant-1 is 1325 MTPD, ammonia-2 is

1300 MTPD, while Urea-1 & 2 is 2325 MTPD & 2280 MTPD respectively.

Other associated offsite and utility plants are available. NFCL is going in for a Customised Fertilizer Granulation (CFG) Plant of

400 MTPD production capacity. This plant would be put up inside the

existing complex.




1-2

1.3 Brief Process Description of CFG Plant The main sections of the plant are:

• Raw material receiving

• Raw material feeding

• Process section

• Finished product bagging & Conveying

• Pollution control

All the required Solid raw materials (DAP, Urea, MOP, Ammonium

Sulphate, Filler like dolomite or clay ) & Micro Nutrients (Zinc, Boron,

Iron, Sulphur etc ) from the storage bins are proportionately pre

weighed on weigh feeders and fed to the crushers followed by paddle

mixer. This premixed product is fed into the rotating granulator where

steam and water are added to provide sufficient liquid phase by causing

the dry raw materials to agglomerate further into product size granules.

These moist granules are fed into a rotary dryer where they are dried by

hot air generated which the air is drawn from blower in Hot Air

Generator with natural gas firing. These hot granules are cooled in a

rotary cooler and fed to the rotary screen and the oversize material is

separated, crushed & recycled back to the granulator along with

scrubber solution and undersize fraction. The desired product size

material is sent for bagging after coating and addition of Zinc using anti

caking agent. The product is bagged in 50Kg bags by automatic

Weighing and bagging machines (2Nos. 500 Bags/Hr each) and

stitching machines (2Nos) is then dispatched through road.




1-3

The plant is incorporated with stack of 40 meters in height and other

pollution control devices to take care of environmental aspects. The

exhaust air from various equipment is sent to de-dusting and the clean

air is vented to atmosphere through a stack. The de-dusting system

comprises of cyclones followed by water scrubbers and the material

laden liquid is recycled to meet the requirement in granulator.



2 - 1

Rams Safety Consultants Scope, Objective & Methodology

2.0 SCOPE, OBJECTIVE & METHODOLOGY

2.1.0 Scope

The scope of work as per NFCL Service Work Order No. 1200004449 dated 12.01.2011 is to carry out, among other things, Risk Assessment Study of the proposed customised fertilizer granulation plant to cover risk of auto ignition, risk of chemicals under production, handling, storage and transportation, risk due to electrical short circuiting or any other source, threats from the existing plants, Hazop Study of steam, utility and NG line and the consequence analysis of the NG line to the Hot Air Generator of the plant mentioned above.

2.2.0 Objective

2.2.1 The objective of this study is to carry out consequence analysis for the line rupture scenario of the NG line to the Hot Air Generator, risk of auto ignition, risk of chemicals under production, handling, storage and transportation, risk due to electrical short circuiting or any other source, threats from the existing plants, Hazop Study of steam, utility and suggest measures for risk reduction so as to bring the risk to as low as reasonably practicable.

2.1.2 Risk arises from hazards. Risk is defined as the product of severity of consequence and likelihood of occurrence. Risk may be to people, environment, assets or business reputation. This study is specifically concerned with risk of serious injury or fatality to people.

2.1.3 The following steps are involved in the analysis: • Study of the plant facilities and systems. • Identification of the hazards. • Enumeration of the failure incidents. • Estimation of the consequences for the selected failure incidents.

The process of quantitative risk assessment (QRA) is shown in the following block diagram.



2 - 2


2.3.0 Consequence Calculation Procedure

2.3.1 The first step in risk assessment is selection of failure scenarios involving release of hazardous material from process units or storage tanks. The failure scenario considered in CFG Plant is the line rupture of NG line to the Hot Air Generator.

2.3.2 The next step in Risk Assessment is to analyze the consequences of accidental releases of toxic/ flammable material from piping, plant equipment or storage tanks, such as characteristics of the cloud formed and distances to which the adverse effects may reach.

2.3.3 The steps involved in the formulation of outcome of failure scenarios and calculation of consequences are explained in the following diagram.



2 - 3


FAILURE CASE DEFINITION TREE Nature of Hazard

Phase in the Process or Storage

Release Case

Event Tree Or Model (Ρ) Boiling Liquid Expanding Vapour Explosion 2.3.4 The Event Tree diagrams for gas and liquid release incidents are

presented in separate diagrams.

The flammable effects such as jet fire, flash fire, pool fire, fireball and vapour cloud explosion, are explained in the following section 2.4.0.

DEFINE INVENTORY & STORAGE CONDITIONS OF HAZARDOUS MATERIALS

FLAMMABLE

LIQUID OR TWO-PHASE LIQUID OR

TWO-PHASE GAS

TOXIC

GAS

BLEVE(Ρ)

OTHER CASES

BLEVE Model

Flammable Gas

Event Tree

Flammable Liquid

Event Tree

Toxic Gas

Event Tree

Toxic Liquid

Event Tree



2 - 4


Is there Immediate Ignition?

FLAMMABLE LIQUID EVENT TREE

Is the Release Instantaneous?

Does a Pool Form?

Does the Pool Ignite?

Assess Fire Damage

Use Gas Event Tree to Model Gas Behaviour

Assess Pollution Use Gas Event Tree to Model Gas Behaviour

Assess Fire Damage

Assess Fire Damage

Use Gas Event Tree to Model Gas Behaviour

Assess Pollution Use Gas Event Tree to Model Gas Behaviour

Assess Fire Damage

No

Yes

Pool Fire

No

No

Yes

Yes

Estimate Duration Calculate Release Rate

Adiabatic Expansion

Yes

Release Case

Yes

No

No

Calculate Spread & Evaporation

Fire Ball

Pool Fire

No

Yes

Yes

No

Calculate Spread & Evaporation

Jet Flame



2 - 5




2 - 6


2.2.5 Consequence analysis and calculations are effectively performed by computer

software using models validated over a number of applications. This report is based on PHAST software of DNV Technica, UK. PHAST is a major component of the risk analysis software PHAST RISK (previously known as SAFETI) used for consequence modeling. The consequence calculations perform dispersion modeling and effect modeling for each weather condition specified.

The dispersion modeling calculates the distances to critical concentrations, i.e. flammability limits for flammable materials, and to minimum toxic limits for toxic materials. The effect modeling is performed for flammable materials only, and calculates the distances to critical radiation levels for jet fires, pool fires and BLEVEs, and the distances to critical over-pressures for explosions.

The PHAST software uses the Unified Dispersion Model (UDM) capable of describing a wide range of types of accidental releases. The Model uses a particularly flexible form, allowing for sharp-edged profiles, which become more diffuse downwind.

2.2.6 The calculations by PHAST software involve following steps for each modeled failure case:

- Run discharge calculations based on physical conditions and leak size.

- Model first stage of release (for each weather category).

- Determine vapour release rate and pool evaporation rate.

- Dispersion modeling.

- In case of flammable release, calculate size of effect zone for fire and explosion.

2.2.7 The PHAST programme contains data for a large number of chemicals and allows definition of mixtures of any of these chemicals in the required proportion. Appropriate inputs for material, parameters, scenario and system details (pressure, temperature, size of opening etc.) are used in calculations for each failure case.

2.2.8 The stages involved in the calculations by PHAST are as follows:

(1) Input background data.

(2) Input failure cases.

(3) Select failure cases.



2 - 7


(4) Run consequence calculations for selected cases.

(5) View results as graphs and tables.

The background data include material data, parameter data and weather data.

2.2.8 Weather data

Weather conditions are listed, each weather condition being a combination of wind speed and atmospheric stability. The weather data form important input to the dispersion calculations, and results for a single set of conditions could give a misleading picture of the hazard potential. The PHAST programme allows definition of a list of weather conditions, and it performs dispersion modeling for each condition in the list.

Stability class is a measure of the atmospheric turbulence caused by thermal gradients and it controls the vertical mass transfer mechanisms in the air, close to the ground. Six main categories (known as Pasquill stability classes) denoted by letters A - F are considered.

Stability Pasquill Stability Class

Temperature Gradient (deg. C per 100 metres)

Very unstable A

< (-)1 Unstable B

Slightly unstable C

Neutral D (-)1 to 0

Stable E 0 to 1

Very stable F > 1



2 - 8


The basis for defining the stability parameter is illustrated in the following diagram.

(a) Unstable Conditions dT/dz < (dT/dz) adiabatic

(b) Stable Conditions dT/dz > (dT/dz) adiabatic

Neutral Conditions (dashed line) dT/dz = (dT/dz) adiabatic



2 - 9


Relationship between wind speed and stability is given in the following table:

Wind Speed

Day Time:

Solar Radiation

Night Time: Cloud Cover

(m/s)

Strong

Mediu

m

Slight

Thin < 3/8

Mediu

m > 3/8

Overcas

t > 4/5

< 2 A A – B B - - D

2 - 3 A - B B C E F D

3 - 5 B B – C C D E D

5 - 6 C C – D D D D D

> 6 C D D D D D

Category D (neutral) is the most probable in moderate climates, and may occur for up to 80% of the time at relevant sites. It will almost always occur if the sky is heavily overcast.

Category F (stable) is generally associated with nighttime in cold weather and medium cloud cover. These conditions are not conducive to atmospheric dispersion. Category F is not possible over sea. This stability category is normally selected for considering worst-case scenarios.

It is necessary to consider a range of typical weather conditions in the consequence modelling calculations. PHAST software allows definition of multiple combinations of weather parameters.

The weather parameters required for PHAST are the following:

• Wind velocity

• Atmospheric weather stability class

• Atmospheric temperature



2 - 10


• Relative humidity

• Surface roughness parameters

Based on the meteorological and weather data for the plant site, the following parameters are taken for consequence calculations to cover the conditions prevailing at different periods and seasons.

Parameter Unit Weather Condition

# 1 # 2 # 3

Wind Velocity (m/s) 3 3 5

Weather Stability Class B D D

2.3.0 Flammable Effects

2.3.1 The release of flammable gas or liquid can lead to different types of fire or explosion scenarios. These depend on the material released, mechanism of release, temperature and pressure of the material and the point of ignition. Types of flammable effects are as follows.

2.3.2 Pool fire: The released flammable material which is a liquid stored below its normal boiling point, will collect in a pool. The geometry of the pool will be dictated by the surroundings. If the liquid is stored under pressure above its normal boiling point, then a fraction of the liquid will flash into vapour and the remaining portion will form a pool in the vicinity of the release point. Once sustained combustion is achieved, liquid fires quickly reach steady state burning. The heat release rate is a function of the liquid surface area exposed to air. An unconfined spill will tend to have thin fuel depth (typically less than 5 mm), which will result in slower burning rates. A confined spill is limited by the boundaries (e.g. a dyked area) and the depth of the resulting pool is greater than that for an unconfined spill.

2.3.3 Flash fire: A flash fire occurs when a vapour cloud of flammable material burns. The cloud is typically ignited on the edge and burns towards the release point. The duration of flash fire is very short (seconds), but it may continue as jet fire if the release continues. The overpressures generated by the combustion are not considered significant in terms of damage potential to persons, equipment or structures. The major hazard from flash fire is direct flame impingement. Typically, the burn zone is defined as the area the vapour cloud covers out to half of the LFL. This definition provides a conservative estimate, allowing for



2 - 11


fluctuations in modelling. Even where the concentration may be above the UFL, turbulent induced combustion mixes the material with air and results in flash fire.

2.3.4 Jet fire: Jet flames are characterized as high-pressure release of gas from limited openings (e.g. due to small leak in a vessel or broken drain valve). Jet fires can cause serious damage to equipment and people.

2.3.5 Boiling liquid expanding vapour explosion (BLEVE) or fireball: A fireball is an intense spherical fire resulting from a sudden release of pressurized liquid or gas that is immediately ignited. The best known cause of a fireball is a boiling liquid expanding vapour explosion (BLEVE). Fireball duration is typically 5 – 20 seconds.

2.3.6 Vapour cloud explosion: When a large quantity of flammable vapour or gas is released, mixes with air to produce sufficient mass in the flammable range and is ignited, the result is a vapour cloud explosion (VCE). Without sufficient air mixing, a diffusion-controlled fireball may result without significant overpressures developing. The speed of flame propagation must accelerate as the vapour cloud burns. Without this acceleration, only a flash fire will result.

2.3.7 The levels of heat radiation and explosion over-pressure considered for the analysis are based on the following reference publications:

• Loss prevention in the Process Industries by F. P. Lees

• Guidelines for Chemical Process Quantitative Risk Analysis published by AIChE / Center for Chemical Process Safety (CCPS)

• PHAST & SAFETI User Manuals of DNV Technica

• Gas Explosion Handbook published by GexCon

2.3.8 Flammable Models and End-points

Pool fire, Jet flame and BLEVE

Radiation Level (kW/m2)

Observed Effect

4 Sufficient to cause pain to personnel if unable to reach cover within 20 seconds; however blistering of the skin (second-degree burn) is likely; 0% lethality.

12.5 Minimum energy required for piloted ignition of wood, melting of plastic tubing.

37.5 Sufficient to cause damage to process equipment.



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2.3.9 The effect of thermal dose can be understood from the following correlation.

Thermal Dose (kJ/m2)

Burn Effect

65 Threshold of pain, no reddening or blistering of skin. 125 First degree burns (Persistent redness). 200 Onset of serious injury. 250 Second degree burns (Blistering). 375 Third degree burns (Charring).

Note: Thermal Dose = (Heat radiation intensity)4/3 x (Time) Units: Thermal dose – kJ/m2 Heat radiation intensity – kW/m2 Time - seconds

2.3.10 Explosion Parameters

An explosion results from a very rapid release of energy. The energy release must be sudden enough to cause local accumulation of energy at the site of explosion. The damage from an explosion is caused by the dissipating energy. The explosion energy causes the air to expand rapidly, forcing back the surrounding air and initiating a pressure wave (also called blast wave), which moves rapidly outward from the blast source. The pressure wave contains energy, which results in damage to the surroundings. For chemical plants, much of the damage from explosions is done by the pressure wave. The maximum pressure over ambient caused by the pressure wave is called the peak over-pressure.

The general correlation between explosion over-pressure level and the damage caused is given in the following table.

Over-pressure Observed Effect bar(g) psig

0.021 0.3

“Safe distance” (probability 0.95 of no serious damage below this value); projectile limit; some damage to house ceilings; 10% of window glass broken.



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0.069 1 Repairable damage; partial demolition of houses, made uninhabitable; steel frame of clad building slightly distorted.

0.138 2 Partial collapse of walls of houses.

0.207 3

Heavy machines (3000 lb) in industrial buildings suffered little damage; steel frame building distorted and pulled away from foundations.

2.3.11 Effect of explosion overpressure on humans can be seen from the following data:

Effect Explosion overpressure (psi)

Eardrum rupture - 1 % probability (threshold) 2.4 - 10 % probability 2.8 - 50 % probability 6.3

Skin laceration threshold 1 – 2

Serious wound threshold 2 – 3

Serious wound near 50 % probability 4 – 5

2.4.0 Toxic Effects

2.4.1 It is necessary to specify suitable concentration of the toxic substance under study to form the end-point for consequence calculations. The considerations for specifying the end-points for the hazardous material involved in the failure scenario are described in the following paragraphs.

2.4.2 American Industrial Hygiene Association (AIHA) has issued Emergency Response Planning Guidelines (ERPG) for many chemicals.

• ERPG-1 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing other than mild transient adverse health effects or perceiving a clearly defined, objectionable odour.



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• ERPG-2 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptoms, which could impair an individual's ability to take protective action.

• ERPG-3 is the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing life-threatening health effects.

Where available, the ERPG values are useful for consideration in the consequence calculations. Where the ERPG values are not available, temporary emergency exposure limit (TEEL) values published are used. The definitions for the TEEL values are similar to ERPG.

2.4.3 Toxic limit values as Immediately Dangerous to Life or Health (IDLH) concentrations are issued by US National Institute for Occupational Safety and Health (NIOSH). An IDLH level represents the maximum airborne concentration of a substance to which a healthy male worker can be exposed as long as 30 minutes and still be able to escape without loss of life or irreversible organ system damage. IDLH values also take into consideration acute toxic reactions such as severe eye irritation, which could prevent escape. IDLH values are used in selection of breathing apparatus.

2.4.4 Significant flammable properties of NG used in the plant and considered in this study is summarized in the table below:

Chemical

Normal Boiling Point

Flammable Properties Toxic properties

Flash Pt.

LEL UEL Auto Ign. Temp.

ERPG-1 ERPG-2 ERPG-3 IDLH

(Units) (°C) (°C) (%) (%) (°C) (ppm) (ppm) (ppm) (ppm)

Methane (-) 161.5 NA 5 15 537.7 15000 25000 50000


Quantitative Risk Assessment 2009

Rams Safety Consultants Data For Risk Assessment

3 - 1

3.0 DATA FOR RISK ASSESSMENT

3.1 Site Location

Nagarjuna Fertilizers & Chemicals Limited (NFCL) is located at Kakinada,

East Godavari District of Andhra Pradesh. The total area covered by the

NFCL plant is about 380 acres is situated about 500 meters from the coast

just next to Kakinada bay. The site is about 2.5 meters above mean sea level.

It is surrounded on the north by Godavari Fertilizers and Chemicals Limited,

Bay of Bengal on the East, Kakinada town on the west and green belt on the

south. The width of the green belt is 1 km wide and it also extends on the

west. Incidentally the green belt is between the plant and the town. The site

plan is enclosed as Figure 2.1

3.2 Fertilizer Complex

The NFCL complex consists of two ammonia and two urea plants. The

ammonia plants are based on Haldor Topsoe Technology and urea plants on

Snamprogetti, total recycle with ammonia stripping. Ammonia Plant II was

switched over to natural gas from Naptha during the min-revamp . The

shortage of CO2, would be made by a 450 MTPD Carbon Di Oxide Recovery

Plant from the flue gases of Ammonia Plant I Primary Reformer stack. The

production capacity of ammonia plant-1 is 1325 MTPD and ammonia plant -2

1300 MTPD. Similarly, Urea-1 is 2325 MTPD and Urea-2 2281 MTPD.

NFCL is going in for a 400 MTPD Customised Fertilizer Granulation (CFG) Plant. This plant would be put up inside the existing complex.

3.3 The Data Requirements:

a. Chemical inventories in various process and storage units (vessels, tanks)

b. Properties of the chemicals c. Meteorological Data




3 - 2

d. Demographic Data

NG line to HAG

Line Dia inch Line Length m

(from main header to HAG burner)

Pressure Kg/cm2

Temp °C Flow Nm3/hr

2 650 6.3 – 8.5 40 / 55 161.1 – 426.5

Materials The MSDS of the chemicals are enclosed as Annexure 1.

3.5 Site and Equipment Layout

Site Plan and Layout Plan for the plant are given in Figures 2.1 and 3.1

respectively.

3.6 Meteorological Data

The role of the atmosphere in dilution and dispersion of the accidentally

released hazardous chemicals is not very well understood in view of the

hydrodynamic complexities. The atmosphere acts like a large non-

Sl. No. Raw Material Approximate inventory Maintained

(MT)

Storage Mode

1 Di Ammonium Phosphate (DAP)

1800 Filled Bags

2 Urea 200 “ 3 Murate of Potash (MOP) 500 “ 4 Ammonium Sulphate 50 “ 5 Dolomite (Filler) 500 “ 6 Sulphur 10 Bulk / Filled

Bags 7 Zinc Sulphate 50 Filled Bags 8 Micro Nutrients 10 “




3 - 3

homogeneous reactor with several simultaneous and often complementary

phenomena occurring. The notable parameters for assessing the atmosphere

are wind speed its direction and profile, micrometeorology and atmospheric

stability and topographic parameters.

The meteorological data compiled by India Meteorological Department (IMD)

for Kakinada has been used for the risk assessment computations. The

annual mean air temperature is taken as 28 Degrees C and mean % humidity

as 72%. The average velocity is taken as 3.2 m/s.

Atmospheric stability is a very important factor for predicting the dispersion

characteristics of gases/vapours of the surrounding environment. Change in

atmospheric stability is due to the direct consequence of its vertical

temperature structure. For a given location, this tends to vary from season to

season. The stability effects are mathematically represented through Pasquill

parameters. The following stability classification is employed.

Stability Class Atmospheric Condition A Very Unstable B Unstable C Slightly Unstable D Neutral E Stable F Very Stable

Six stability classes from A to F are defined while wind speed can take any one of the innumerable values. It may thus appear that a large number of outcome cases can be formulated by considering each one of very many resulting stability class-wind speed combinations. In fact the number of outcome cases that needs to be considered for formulating outcome cases in any analysis is very limited. In nature only certain stability class and wind speed occur. For instance A-3 m/s or B-5 m/s or F-4 m/s do not occur in nature. As a result only one or two or three stability class-wind speed combinations need to be considered to ensure reasonable completeness of the Risk Assessment.

The stability class distribution over the years works out as below:




3 - 4

Month Wind Speed Cloud cover

(oktas) Stability Class

Km/hr m/s Day Night Day Night Jan 10.3 2.9 2.0 1.5 B E Feb 8.8 2.4 2.2 1.5 B E

March 8.3 2.3 2.3 1.3 B E April 9.1 2.5 3.7 2.3 B E May 11.1 3.1 4.3 3.0 B E June 12.1 3.4 5.1 5.1 D D July 12.3 3.4 6.1 6.0 D D Aug 11.0 3.1 5.6 5.7 D D Sep 8.6 2.4 5.4 5.5 D D Oct 9.5 2.6 4.5 4.8 B E Nov 12.0 3.3 3.4 3.6 B E Dec 11.3 3.1 2.2 2.2 B E

The cloud cover data: January – May 1.3 – 4.3 oktas June – October 4 – 6.1 oktas November – December 2.2 – 3.6 oktas

B 33% (day other than monsoon) D 17% (day –monsoon) & !7% (night- monsoon) E 33% (night other than monsoon)

For our study D-3m/s, D-5.0 m/s and B-3m/s stability class-wind speed combinations are considered. A most advanced method of estimating the dispersion parameters has been employed in which the input data requires the vertical temperature, wind profile and roughness factors.

3.7 Demographic Data: The following population has been considered: 0.5 km radius : 650 1.0 km radius : 6641




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2.0 km radius : 12660 3.0 km radius : 37129 5.0 km radius : 73236

The day and night population has been assumed to be the same. The consequences for various outcome cases – mainly toxic exposure – depend on whether people stay indoor or outdoor. The assumptions made Is as under: Day time 30% indoor, 70% outdoors Night time 70% indoor, 30% outdoors

3.8 Wind Direction

The annual frequency distribution of wind directions between 0830 hrs and 1730 hrs is tabulated below:

N NE E SE S SW W NW Calm 0830 hrs 4 24 1 5 1 37 7 9 12 1730 hrs 0 11 7 36 8 28 5 3 2



Rams Safety Consultants Visualisation Of Maximum Credible Accident Scenarios

4 - 1

4.0 VISUALISATION OF MAXIMUM CREDIBLE ACCIDENT

SCENARIOS

4.1 The starting point of Risk Assessment Study is the identification of hazards

and selection of scenarios that are then addressed for further analysis.

Hazard is defined as a chemical or physical condition that has the potential

for causing damage to people, property or environment. A number of

techniques are available for hazard identification depending upon the depth

and objective of the study.

Accidental release of toxic vapours or flammable vapour cloud can result in

severe consequences like toxic vapour cloud or vapour cloud explosion.

Delayed ignition of flammable vapours can result in blast over pressures.

Toxic clouds cover large distances due to lower concentration threshold

value.

In contrast, fires have localized consequences. The extent of damage to

people depends on the heat flux and duration of exposure. Fires can be put

out or contained in most cases.

Hazards, in process plant, are primarily identified on the following information:

Hazardous properties of materials handled during the process

Types of unit process / unit operation

Operating pressure / vacuum / temperature

4.2 Maximum Credible Accidents and Consequence Analysis (MCACA)

MCACA is a scientific technique to identify the vulnerable areas in a plant

where sudden heavy release of toxic vapours or flammable vapour is a




4 - 2

probability. Such releases can create unsafe situations to the personnel

inside the plant, people in the surrounding area and to the environment.

MCACA aims at identifying the most credible unwanted accidents, which can

cause maximum damage. For this purpose, a number of probable or potential

accident scenarios have been visualised, examined, screened to select only

the most probable events and their credibility established. These incidents are

called Representative incidents.

4.3 Methodology Followed for Selection of Release Scenarios

In the European countries and USA there are statutory guidelines for the

selection of release sources for performing Risk Analysis of Industrial

installations. In this study the release of natural gas from the 2” header

supplying fuel to the HAG due to line rupture has been considered since all

other materials handled are solid and non-hazardous.

This consequence analysis gives:

a. Description of the potential accident (rupture of pipeline)

b. Estimation of the quantity of material released (flammable, explosive)

c. Where appropriate, a calculation of dispersion of material released

(gas)

d. Assessment of harmful effects (heat radiation, blast wave)




4 - 3

4.4 Maximum Credible Accident Scenarios

As mentioned else where, in this study the release of natural gas from the 2”

header supplying fuel to the HAG due to line rupture has been considered

since all other materials handled are solid and non-hazardous

Sl. No

Release Source Failure Mode Outcome Modeled

1

2” Natural Gas Line

Guillotine failure Jet Fire, and Flash Fire.



Rams Safety Consultants Consequence Analysis

5 - 1

5.0 CONSEQUENCE ANALYSIS

5.1.0 Introduction

5.1.1 The major criterion for selection of scenarios is the potential for high hazard considering the amount of hazardous substance involved, operating conditions, and possibility of release and extent of consequence.

5.1.2 The details regarding the natural gas have been furnished in an earlier section of this report. The consequence calculations are based on that data.

5.1.3 The analysis of the scenario selected for study of the CFG plant is presented in the following paragraphs.

Tabular reports and graphic plots are presented wherever appropriate.

5.2.0 Failure scenario

The following scenarios have been considered for consequence calculations.

Sl. No

Release Source Failure Mode Outcome Modeled

1

2” Natural Gas Line

Guillotine failure

Jet Fire, and Flash Fire.

The main hazards are due to handling of flammable natural gas.

The levels of heat radiation for the analysis are based on the following reference

publications:

• Loss prevention in the Process Industries (2nd Edition) by F. P. Lees

• Guidelines for Chemical Process Quantitative Risk Analysis by American Institute of Chemical Engineers (AIChE) / Center for Chemical Process Safety (CCPS)

• PHAST & SAFETI User Manuals of DNV Technica




5 - 2

Flammable Models and End-points

Pool fire, Jet flame and BLEVE

Radiation Level

(kW/m2)

Observed Effect

4 Sufficient to cause pain to personnel if unable to reach cover within 20 seconds; however blistering of the skin (second-degree burn) is likely; 0% lethality.

12.5 Minimum energy required for piloted ignition of wood, melting of plastic tubing.

37.5 Sufficient to cause damage to process equipment.

The general correlation between explosion over-pressure level and the damage caused is given in the following table.

Over-pressure

Observed Effect Bar(g) Psig

0.021 0.3 “Safe distance” (probability 0.95 of no serious damage below this value); projectile limit; some damage to house ceilings; 10% of window glass broken.

0.069 1 Repairable damage; partial demolition of houses, made uninhabitable; steel frame of clad building slightly distorted.

0.138 2 Partial collapse of walls of houses.

0.207 3 Heavy machines (3000 lb) in industrial buildings suffered little damage; steel frame building distorted and pulled away from foundations.




5 - 3

Consequence modeling calculations were carried out using the software PHAST Micro 6.1 of DNV TECHNICA. Graphs obtained as output of the software are presented and summary of the results are tabulated in the following pages.

Summary of Result: For the scenario selected, the outcome cases are considered for the atmospheric conditions 3B, 3D and 5D. The first numeral represents the wind speed in meters per second and the subsequent alphabet represents the stability class. Sl. No Scenario Wind

Velocity / Stability

Damage Distance (m) Radiation Level Jet Fire Ellipse

Flash Fire Envelope

37.5 kW / m2

12.5 kW / m2

4 kW / m2



1

2” NG line to HAG rupture

3 B 9.94 10.50 11.85 7.81 5.17

3 D 10.26 10.68 12.0 7.84 5.15

5D Not Reached

10.78 12.26 6.56 4.70

The graphs for flash fire envelope, intensity radii for jet fire and Radiation vs Distance for Jet fire are shown in the following pages.




5 - 4




5 - 5




5 - 6


Risk Assessment 2011

Rams Safety Consultants Probability Of Occurrence For Selected Scenarios

6-1

6.0 PROBABILITY OF OCCURRENCE FOR SELECTED

SCENARIOS

6.1 Risk Factor Risk is defined as, “a combination of uncertainty and damage” and “a triple

combination of event, probability and consequence”. Risk estimation

combines the consequences and likelihood of all incident outcomes from

related incidents to provide a measure of risk, but these estimates based

on mathematical models have the limitation of not covering all factors

existing in the real scenario. This limitation must be appreciated by

management to set reasonable goals.

6.2 Probability estimation

The probability estimation is done by different theoretical methods such as

fault tree analysis, event tree analysis etc. The likelihood can be estimated

theoretically. But where the design involved is sufficiently similar to existing

designs represented in the historical records available in the literature, the

incident frequency can be derived from historical statistics. Only where the

design is substantially different and historical data do not exist the fault tree

method is adopted.



Rams Safety Consultants Probability Of Occurrence For Selected Scenarios

6-2

The probability or frequency of occurrence for piping related to the scenario

identified in Chapter 4 is as under:

Description Type of Failure Failure Rate

Piping - Small

(≤ 50 mm Dia.)

Rupture 8.8 x 10 -7 (m.yr)-1

(m.yr)—1 means per metre per year

Ignition Probability

Historical data on ignition of flammable releases has been used as a basis for determining Ignition probabilities.

Type of ignition Probability Immediate 0.065 Delayed 0.065

No ignition 0.87 The conditional possibility of explosion is 0.67.



Rams Safety Consultants Risk of Auto Ignition, Risk Of Chemicals Under Production, Handling, Storage etc,

7 - 1

7.0 RISK OF AUTO IGNITION, RISK OF CHEMICALS UNDER PRODUCTION, HANDLING, STORAGE AND

TRANSPORTATION, RISK DUE TO ELECTRICAL SHORT CIRCUITING OR ANY OTHER SOURCE, THREATS FROM THE EXISTING PLANTS

7.01 Materials Handled in CFG Plant

The details of raw materials and micro nutrients which are used in the

production of CFG are given in Table 7.1.

These materials are fed to the paddle mixtures from the storage bins in pre-

determined quantities. There is no chemical reaction but only physical mixing.

The premixed mixture is granulated, dried, screened and bagged after

precoat. Sl. No

Name of Chemical

Decomposition Temperature

Deg. C

Products of Decomposition

Approximate Quantity Stored

(MT)

Mode of Storage

1 DAP

155

Release of ammonia and oxides of phosphorus

1800

Filled Bags

2

MOP

Sublimes at 1500 deg C

When subjected to extremely high temperatures small quantities of chlorine is liberated.

500

Filled Bags

3

Urea

122.7

Ammonia, oxides of nitrogen, cyan uric acid, cyanic acid, biuret and CO2

200

Filled Bags

4 FeSO4 > 300 Sulphur Oxides

10 Filled Bags

5 Zn SO4

600

Fumes of SOx

50

Filled Bags

6 Ammonium

Sulphate

280

Ammonia, Sulphur trioxide and Sulphur di-oxide

50

Filled Bags

7 Dolomite 870 Ca and Mg oxides and CO2

500 Filled Bags

8 Borax

None 10 Filled Bags

9 Sulphur Boiling Point 444.6 Sulphur di-oxide and H2S under certain conditions

10 Bulk / Filled Bags

Table 7.1




7 - 2

7.02 Risk of Chemicals under Production, Handling, Storage and

Transportation

When the materials are subjected to extreme high temperatures during an

external fire, there is a possibility of the chemicals decomposing to release

limited quantity of toxic by-products of decomposition (e.g., Ammonia,

Chlorine sulphur dioxide etc.,).

The materials stored, handled and mixed is thermally stable at normal working

conditions during storage and transport. The materials do not have the

tendency for auto ignition based on their chemical characteristics. They will

not get ignited due to normal ignition sources and heated metals. So there is

no possibility of fire taking place in the storage area due to auto ignition, hot

work etc., and leading to emission of toxic gases from the stored materials.

The available literature does not mention about any evolution of toxic gases to

that extent that it needs dispersion/consequence modeling.

Precautions to be taken during Storage & Handling to minimize/mitigate the risk

The quantity of the raw materials being limited and also since they are stored

in bags (which means that they can be segregated and stacked as per good

practices to provide separation distance as well as access), the possibility of

an external fire leading to a major emergency scenario (release of toxic by

products of materials) is very remote. The following are the precautions

suggested to prevent and or mitigate the risk due to decomposition of

materials due to external fires:

1. Special care should be taken to avoid the storage of raw materials in

close proximity to combustible materials such as wooden pallets,

packaging materials etc.,




7 - 3

2. It is to be ensured that free access is made available to the storage

area for emergency and fire-fighting equipment to be used in the event

of a fire/decomposition.

3. The storage area should have provision for ventilation to dilute the

concentration of toxic by-products/fumes as a result of any external

fire.

4. Self contained breathing apparatus (SCBA) and suitable protective

clothing should be made available in the vicinity of the storage and

these should be worn while attending to any fires in the storage area.

7.03 Risk Due To Electrical Short Circuiting A short circuit in an electrical circuit is one that allows a current to travel along

a path where essentially no (or a very low) electrical impedance is

encountered. Short circuits occur mainly due to overloading as it leads to

heating effect and may result in fire breakout and fatal accidents, if proper

instructions are not followed. Electrical fires spread rapidly and cause loss of

lives and property.

Such incidents can be minimized to a great extent if the under noted

precautions are observed.

1. Always use good quality cables.

2. Make sure that electrical outlets are designed to handle

appliance loads.

3. If an electric appliance smokes or gives away an

unusual smell, unplug it immediately, then do the

proper servicing before using it again.

4. Avoid joints in wiring (taping of wires). Instead, use

extension box with fuse or else go for soldering and

proper mechanical joints.

5. Always renew the wiring after ageing. Replace




7 - 4

electrical cords that are cracked or frayed.

6. Use adequate capacity fuses for protection. Do not

increase the ratings without ascertaining reason of fuse

blowing. Do not tamper with fuse box. Install the Fuse

board away from combustible materials like paper, oil,

curtains etc.

7. Keep flammable material (oil etc.) safely in special

containers.

8. Disconnect electrical tools and appliances when not in

use.

9. Use correct rating Earth Leakage Circuit Breaker

(ELCB). A leakage current even of 1 ampere can cause

electrical fire. A correctly chosen ELCB can detect the

leakage current and can cut-off circuit thus reducing

the fire-risk.

10 The lighting fixtures should be suitable service in a

particular area.

7.04 Threats from the existing plants

The CFG Plant is to the west of existing cooling tower of Ammonia Plant-II

and north west of Urea Plant-II cooling towers. Any release of chlorine from

the cooling towers might affect the personnel in this plant subject to the

direction of the wind.

Similarly any major ammonia release from ammonia and / or urea plants

would have an effect on the personnel working in CFG Plant, again, subject to

wind direction.



Rams Safety Consultants Conclusions and Recommendations

8 - 1

8.0 CONCLUSIONS AND RECOMMENDATIONS

8.1 Conclusions

Ever since the commissioning of the NFCL plants (Ammonia & Urea) there

has been no major release of Natural Gas leading to a fire situation. The

CFG plant appears to be well designed and adequately instrumented for

its safe operation.

With the extension of current predictive and preventive maintenance

practices and testing and calibrating procedures to the NG line and CFG

plant, there appears to be no major risk of a major natural gas release and

subsequent fire hazard.

8.2 Review of Risk Analysis Study The major risk is due to accidental NG release resulting in fire and

explosion. The scenario of NG gas line rupture to HAG resulting in Jet and

Flash fires would not result in Off-Site emergency since the damage

distances would be confined to the factory premises. The quantity of gas

released, assuming effective action is taken to cut off the gas with in 5

minutes, may not result in explosion and consequent damage due to over

pressure.

General Recommendations The two steps generally considered in Risk reduction in the CFG plant are

(a) Reduction of consequences and (b) Reduction of likelihood of an

accident release of NG.




8 - 2

Some of the measures to reduce consequence are:

a) Automatic Shut Down

b) Effective maintenance System & safety devices

c) Safety Management System (SMS)

Automatic Shut Down

The quantity of material escaping from containment or from the NG line, in

case of line rupture, would get completely cut off if automatic shut down is

available and a release takes place.

Maintenance System and Safety Devices

A number of instruments are provided for the safe operation of the NG line

to HAG burner and CFG plant. Scheduled and effective maintenance of

instruments and safety devices may prevent, to a very large extent, failure

resulting in release of flammable gas

Safety Management System (SMS)

The Unit has a well documented Safety Management System (SMS)

covering a number of elements. By effective Safety Management System,

to a very large extent, failures may be prevented.

8.3 Specific Recommendations Special attention in terms of inspection and safety management systems

for NG line is suggested.

A portable explosimeter will be utilized to identify the leaks from time to

time.




8 - 3

Production, Handling, Storage and Transportation

Electrical fittings should conform to the service. All sources of heat must be kept away from fertilizers. Potential heat sources include light bulbs,

heating systems, steam pipes, electric motors, live electrical cabling and

naked flames.

Electrical Short Circuiting

The recommendations made below, if followed might obliterate fires and

consequent damages due to electrical short circuit

The lighting fixtures in the NG routing and HAG area should conform to

the standards suitable for service in that area and once installed must be

maintained.

Use only ISI certified appliances.

Use good quality fuses of correct rating, miniature circuit breakers

and earth leakage circuit breakers.

Use one socket for one appliance.

Switch off the electric supply of the fire affected areas.

Fuses and switches should be mounted on metallic cubicles for

greater safety against fire.

Replace broken plugs and switches.

Keep the electrical wires away from hot and wet surface.

Don’t use substandard fixtures, appliances.

Never have temporary or naked joints on wiring.

Don’t lay wires under carpets, mats or doorways. They get

crushed, resulting in short circuiting.

Don’t lay wires under carpets, mats or doorways. They get

crushed, resulting in short circuiting.




8 - 4

Don’t allow appliances cords to dangle.

Don’t place bare wire ends in a socket.

No combustible material should be permitted to be stored in the

plant

Threats from the Existing Plants With the current predictive and preventive maintenance practices and

testing and calibrating procedures, the probability of a major gas release

from the existing units appears to be very remote.

Mock drills should be conducted posting necessary observers.

Information pamphlets may be issued which would serve as a refresher

briefing to all the employees detailing how to respond in case of an

emergency.

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