1

CHAPTER 1

INTRODUCTION

When we refer to hazards in relation to occupational safety and health the

most commonly used definition is A Hazard is a potential source of harm or

adverse health effect on a person or persons. A hazard is any source of potential

damage, harm or adverse health effects on something or someone under certain

conditions at work. Due to presence of various hazards in the work place workers

are likely to be injured or any other accidents like property damage can be

occurred. These accidents and property damage can be prevented by several

techniques. One of these techniques is Hazard Analysis.

Hazard analysis is the process of determining the release probabilities and

quantities, emission or release rates, the routes/pathways by which the released

substances could reach the receptors, the fate of the substances in environmental

media through which they are transported or moved and characteristics of the

receptors at risk. Risk evaluation is the process of identifying, whether the

estimated level of risk is tolerable. Tolerable risk is not equated with

acceptability; it refers to a willingness to live with a risk so as to secure certain

risk benefits, and in the confidence that the risk is being properly controlled.

Hazard analysis involves the identification and quantification of the various

hazards (unsafe conditions) that exist in the plant. On the other hand, risk analysis

deals with the identification and quantification of risks, the plant equipment and

personnel are exposed to, due to accidents resulting from the hazards present in

the plant. Hazard and risk analysis involves very extensive studies, and requires

a very detailed design and engineering information.

Many Hazard Identification techniques are available for identifying the

hazards. There are reactive (post hazard scenario) or proactive (predictive) tool or

2

hazard identification. Some of the proven tools are mentioned below. These are

not exhaustive

Reactive approach

Accident Investigation

Plant Inspection

Critical Incidence Technique (CIT)

Incident Recall Technique

Proactive approach

Job Safety Analysis (JSA)

Failure Mode and Effect Analysis (FMEA)

Hazard and Operability Study (HAZOP)

Fault Tree and Event Tree Analysis (FTA & ETA)

Management Oversight Risk Tree (MORT) Analysis

Fire Explosion and Toxicity Index (FETI)

Material / Chemical Reactive Analysis

Consequence analysis etc.

The common terms used in Risk Assessment or Hazard Analysis are elaborated

below:

Risk is defined as a likelihood of an undesired event (accident, injury or

death) occurring within a specified period or under specified circumstances. This

may be either a probability depending on the circumstances.

Hazard is defined as a physical situation, which may cause human injury,

damage to property or the environment or some combination of these criteria.

Hazardous substance means any substance or preparation, which by

reason of its chemical or physic chemical properties or handling is liable to cause

3

harm to human beings, other living creatures, plants, microorganisms, property

or the environment.

Hazardous process is defined as any process or activity in relation to an

industry which may cause impairment to the health of the persons engaged or

connected therewith or which may result in pollution of their general

environment.

In this Project, Hazard Analysis was done in The Fertilizers and Chemicals

Travancore Limited (or FACT Ltd), a fertilizer and chemical manufacturing

company in Kochi, Kerala. It consists of several plants but hazard analysis was

carried out in Ammonia Production Plant and its Storage Area.

4

CHAPTER 2

FACT ABOUT THE COMPANY

The Fertilizers and Chemicals Travancore Limited (or FACT Ltd), a fertilizer and

chemical manufacturing company in Kochi, Kerala, India, was incorporated in

1943, by Maharajah Sree Chithira Thirunal Balarama Varma. In 1947 FACT

started production of ammonium sulphate with an installed capacity of 50,000

MT per annum at Udyogamandal near Cochin. It is the first fertilizer

manufacturing company in independent India and also the largest Central public

Sector Undertaking (CPSU) in the State of Kerala.

The company has 2 production units Udyogamandal Complex (UC) at Eloor,

Udyogamandal, and Cochin Division (CD) at Ambalamedu. The Caprolactam

plant in Udyogamandal was commissioned in 1990. Main products of the

company include Ammonium PhosphateSulphate (FACTAMFOS), Ammonium

Sulphate, Zincated Ammonium Phosphate, Caprolactum, Sulphuric Acid,

Ammonia and other complex fertilizers. Gypsum, nitric acid soda ash and

coloured Ammonium Sulphate are major by-products.

The factory commenced production of ammonium sulphate in 1947 at the dawn

of Indian independence using wood as the raw material for production of

ammonia. With the effect of time, wood gasification became uneconomic and was

replaced with naphtha reforming process. Through a series of expansion

programmes, FACT soon became the producer of the widest range of fertilizers

suited for all crops and all soil types in India. It became a Kerala State public

sector enterprise in 1960 and in 1962, it came under the Government of India.

Diversification to full-fledged engineering services (FEW) in the fertilizer field

and allied areas followed. The next major step forward was the diversification of

petrochemicals, an important milestone in the growth of the company. FACT has

formed a Joint Venture Company with Rashtriya Chemicals & Fertilizers Limited

5

for manufacturing load bearing panels and other building products using

phosphogypsum.

The factory is situated in an area of 20.2 hectares at the bank of river Periyar. The

area around the factory contains a market, a hospital and schools, two shopping

complexes and more than 1100 quarters. The neighboring factories are the

Travancore Cochin Chemicals Ltd (TCC), Hindustan Insecticides Ltd (HIL),

Indian Rare Earths Ltd(IRE). The factory is located in the Eloor Panchayat which

has a density of population more than 3000 per square kilometer. The present

operating plants in Udyogamandal division are the following.

Sulphuric Acid

Ammonium Sulphate

Phosphoric Acid

Ammonium Phosphate

Ammonia Plant

2.1 UDYOGAMANDAL DIVISION

FACT started with a low profile of nearly 4950 MT per annum of ammonium

sulphate production and 49500 MT of super phosphate. Later on, the production

capacity was raised in four stages of expansion. Some of the old process/plants

were scrapped adding new and sophisticated ones. The present production

capacity is as follows. Ammonium sulphate is a co-product of caprolactam.

FACT manufactures Caprolactam, the raw material for Nylon-6 which is

extensively used for the production of tyre cord, textile filament yarn and

engineering plastics. FACT, one of the only two manufactures of this product in

India, has the capacity to produce 50,000 tonnes of Caprolactam in a year.

Ammonium Sulphate liquor obtained as a by-product from the Caprolactam Plant

is converted as a useful fertiliser product in a New Ammonium Sulphate Plant,

2,25,000 TPA capacity put up in October 1990, at a cost of Rs.35 crore. As a

replacement to the existing high energy consuming old Ammonia plants at

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Udyogamandal, a new 900 TPD capacity Ammonia Plant at a cost of Rs.642 crore

was put up in March 1998. FACT Udyogamandal plants received ISO 14001

certification in March 2000 for conforming to the Environmental Management

System standard.

FACT's Caprolactam exported to various countries including in USA, not only

earns precious foreign exchange, but also appreciation on account of its excellent

quality. The Caprolactam Plant also produces 2,25,000 tonnes of Ammonium

Sulphate per year as coproduct and small quantities of Soda Ash and Nitric Acid

as by products. The plant has been certified ISO 9001:2002 since April 1996 by

RWTUV, Germany and ISO14001 since December 1999 by DNV, Netherlands.

Installed capacity/annum

Ammonia 330,000 MT

Sulphuric Acid 379,500 MT

Phosphoric Acid 33,000 MT

Ammonium Sulphate 225,000 MT

Ammonium Phosphate 148,000 MT

(FACTAMPHOS 20:20)

2.2 ENVIRONMENTAL POLICY

FACTUD is committed to

1. Continual improvement in its environmental performance and prevention of

pollution

2. Compliance with environmental rules, regulations and other requirements

applicable

3. Conservation of resources and waste minimization

4. Improvement of communication with interested parties

5. Training for improved environmental management

7

2.3 PRODUCTS

STRAIGHT FERTILISERS

AMMONIUM SULPHATE: Ammonium Sulphate is a nitrogenous fertiliser

containing 20.6% nitrogen, entirely in ammonical form. It has excellent physical

properties nonhygroscopic, crystalline and free flowing. It is ideal as a straight

nitrogenous fetiliser and also as an ingredient in fertiliser mixtures. It is the most

widely preferred nitrogenous fertiliser for top dressing on all crops. Another

unique advantage is that it contains 24% sulphur, an important secondary nutrient.

COMPLEX FERTILISERS

FACTAMFOS (AMMONIUM PHOSPHATE SULPHATE): FACTAMFOS

20:20:0:13 is a chemical blend of 40 parts of ammonium phosphate and 60 parts

of ammonium sulphate. It contains 20% N and 20% P2O5. The entire N is in

ammonical form and P is completely water soluble. In addition, FACTAMFOS

contains 13% sulphur, a secondary plant nutrient which is now attaining great

importance in the agricultural scene. FACTAMFOS 20:20:0:13, with the granular

form and nonhydroscopic and free flowing nature, have excellent physical

properties. It is ideal for application on all soils and all crops. FACTAMFOS

20:20:0:13 can also be used for foliar application.

FACTMIX

FACT prepares on a very large scale all the standard NPK mixtures under the

brand name 'FACTMIX' for different crops for Kerala as stipulated by the

Department of Agriculture. In addition, FACT prepares special tailor made

fertiliser mixtures of any required grade for plantation crops like coffee, tea,

rubber, etc. FACT mixtures are superior in quality with the presence of

ammoniacal nitrogen, water soluble phosphorus, and other major nutrients like

sulphur, calcium, etc.

8

GYPSUM

A by-product of phosphoric acid, is a rich and cost effective source of 16%

sulphur and 22% calcium. FACT is marketing bagged gypsum in brand name

FACT Gypsum all 4 southern states as a soil conditioner with fertilising

properties.

IMPORTED FERTILISERS

FACT markets imported Urea and Potash from Gulf Countries and Russia for

consumption in all 4 southern states as per requirement. Urea with 46% Nitrogen

in the granular/prilled form and Potash with 60% K20 serves the nutritional

requirement in the 4 southern states.

ZINCATED FACTAMFOS

This special product containing 0.3% Zinc in FACTAMFOS has been launched

to address the widespread deficiency of Zinc in most soils of South India.

ZINCATED GYPSUM

This soil amendment and ameliorant contains 2% Zinc in addition to 16% Sulphur

and 22% Calcium for rectifying alkaline soils and improving soil fertility and

physical properties.

FACT ORGANIC

FACT is also marketing organic manure produced from city compost, in brand

name FACT ORGANIC

9

CHAPTER 3

METHODOLOGY

Fig.3.1.Hazard Analysis Methodology

Report Preparation

Evaluation of hazards and recommendations

Selection of Tools for Evaluation

Identifying Harzards

Inspecting Plant

Identifying Hazardous Area

Visiting the Thermal Power Plant

10

CHAPTER 4

AMMONIA COMPLEX

Ammonia is produced from a gaseous mixture of hydrogen (H2) and nitrogen (N2)

in the stoichiometric ratio 3 to 1.The gas mixture will contain limited amounts of

inert (argon & methane) coming from the raw materials. The preparation of this

synthesis gas takes place in the various steps mentioned below

For this ammonia plant the sources of hydrogen and nitrogen are naphtha and

atmospheric air respectively.

The processes for producing ammonia from these raw materials are as follows:

a. Predesulphurisation of the raw naphtha. The bulk part of sulphur is removed in

this section.

b. Final desulphurization of the hydrocarbon feed in one step: Removal of

remaining sulphur compounds.

c. Reforming of the desulphurized hydrocarbons in two steps by steam and air.

The process gas from these steps contains hydrogen and nitrogen as well as carbon

monoxide (CO), carbon dioxide (CO2), methane and argon. The reforming takes

place at a pressure of about 35 kg/cm2g.

d. In the gas purification section, CO is first converted to CO2 and H2 yield. CO2

is then removed in the CO2-removal section, and afterwards the remaining CO

and CO2 in the converted gas are removed in the methanator.

e. The purified synthesis gas is compressed to a pressure of about 135 kg/cm2g

and converted into ammonia by a catalytic reaction.

f. The plant is designed to a nominal production of 900 MTPD ammonia and

10,800 N3/h of synthesis gas. The ammonia product produced in the plant is

sent to the atmospheric storage in Caprolactam plant. Synthesis gas is consumed

in the Caprolactam plant as well, and in combination with part of the CO2

produced.

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4.1 PREDESULPHURISATION OF THE RAW NAPHTHA

Usually raw naphtha contain 1000ppm sulphur. As the presence of sulphur is

poisonous to the reforming catalyst, desulphurization of naphtha is carried out. In

the Predesulphurisation process, the organic sulphur compounds are removed

from the naphtha by catalytic conversion to hydrogen sulphide which is separated

from the naphtha by distillation.

The raw naphtha contain a small amount of dissolved oxygen. If this oxygen is

not removed it will cause the formation of gum in the feed heating system and

hydrogenation catalyst. So the dissolved oxygen is removed by stripping with off

gas in the deaerator.

The deaerator naphtha is mixed with hydrogen rich gas and heated to about

3800C and sent to hydrogenation reactor, R 101.which is filled with cobalt

molybdenum catalyst. Sulphur in naphtha is converted to H2S. The product from

the reactor is cooled and sent to a separator where most of the H2S is separated

from the liquid naphtha. Naphtha is again stripped in the stripper at a temperature

1880C by using reboiler and at a pressure of about 10 kg/cm2 to remove H2S to a

level of less than 5 ppm sulphur.

4.2 FINAL DESULPHURIZATION

The stripped naphtha is again mixed with recycle gas and heated in a super heater

to a temperature of 380 0C and sent to hydrogenator R 201,filled with cobalt

molybdenum hydrogenator catalyst. Most of the residual sulphur is converted to

H2S. H2S is absorbed in the sulphur absorber R 202 filled with ZnO catalyst. The

ZnO reacts with H2S according to the following equation.

H2S + ZnO ZnS + H2O

The gas leaving the absorber contain less than 0.05 ppm sulphur

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4.3 REFORMING - PRIMARY REFORMER

The desulphurized naphtha is then mixed with steam and heated to 490 0C and

sent to the reformer tubes in the primary reformer furnace. There are 184 tubes,

each tube contains three types of reforming catalyst

1. RKNR 13/6x7(top)

2. RKNR 19/19x19(middle)

3. R-67-7H (bottom)

and are externally heated by 144 burners fixed on the sides of the reformer

furnace. The flue gas out let temperature is about 10100C . The gas leaving the

reformer tubes will be at a temperature of about 7900C and the hydrocarbon

content, which is methane only, will be about 10.2 mole%

The hot flue gas from the reformer is utilized for superheating steam, raising

steam in the waste heat boiler and also for heating of the combustion air to

burners.

4.4 REFORMING -SECONDARY REFORMER

The gas from the primary reformer is sent to the secondary reformer where hot

process air is injected. In the first step the heat is supplied by combustion of the

part of the gas achieved by mixing air into the gas. The burning gas provides heat

for the rest of the reforming. The reforming taking place in the primary reformer

is so adjusted that the air supplying the reaction heat in the secondary reformer

will give the required hydrogen/nitrogen ratio of 3 to 1.

In the second step, air is mixed into the partly reformed gas and reacts in the upper

empty space of the secondary reformer. The reaction here is mainly a combustion

resulting in a temperature rise. The outlet temperature will be about 9700C and the

methane concentration approximately 0.3 mole%. The reaction mixture will

contact the catalyst at about 1100 to 1200 0C.

13

4.5 CO CONVERSION

The process gas is cooled to 3600C before being introduced into the HT shift

converter. The shift reaction takes place in the converter is

CO + H2O CO2 + H2 + heat.

This will produce only in contact with a catalyst.

Thus the CO conversion is performed in two steps. A copper/chromium promoted

iron based catalyst is used in the high temperature (HT) shift converter, and a

copper based catalyst is used in the low temperature (LT) shift converter. At the

selected steam/dry gas ratio, this arrangement ensures a low CO content and a low

formation of byproducts.

4.6 CO2- REMOVAL

The gas leaving the CO conversion section has a CO2 content of 21-21.5 mole %.

The CO2 is removed from the gas by absorption in a MDEA solution. In the

absorber the CO2 is removed from the gas by countercurrent absorption in two

stages. In the lower part of the absorber, flash-regenerated solution is used for

bulk CO2 removal. In the upper part strip-regenerated solution is used for

scrubbing. At the outlet of the absorber, the CO2 content in the gas is reduced to

less than 500 ppm.

The CO2 released in the LP flash drum is saturated with water at a temperature of

750C.This mixture is cooled to 40 0C. Part of CO2 produced (2755 kg CO2/h) is

sent through the CO2 blower to Caprolactam plant and sold to the outside parties.

The balance CO2 is vented to the atmosphere.

4.7 METHANATION

In the methanator the CO and CO2 present in the synthesis gas is converted to

CH4 by Nickel based methanator catalyst .In the methanator the reverse of the

reforming reaction takes place. The chemical reactions are as follows:

CO + 3H2 CH4 + H2O + heat

CO2 + 4H2 CH4 + 2H2O + heat

14

The exit gas from the methanator contains H2 & N2 in the ratio 3:1 and inert with

less than 10 ppm CO + CO2.

4.8 AMMONIA SYNTHESIS

The gas from the methanator contains H2 & N2 in the ratio 3:1. The synthesis unit

is constructed for a maximum pressure of 158 kg/cm2, and the normal operating

pressure is in the range of 140 145 kg/cm2. The reaction temperature in the

catalyst bed is 370 490 0C which is close to optimum level. The catalyst is a

promoted iron catalyst containing small amount of non -reducible oxides.

A considerable amount of heat is liberated by the reaction (about 750 kcal/kg

produced ammonia), and the heat is utilized for production of HP steam and for

preheating of HP boiler feed water.

Only about 25 % of the hydrogen and nitrogen flow contained in the synthesis

gas at converter inlet is converted in to ammonia per pass, and it is there for

necessary to recycle the unconverted synthesis gas to the converter. In addition to

the converter .the synthesis loop includes a recirculating compressor as well as

equipment for steam production, boiler feed water preheat, for cooling of the

synthesis gas and condensation as well as separation of ammonia.

The converter is a radial type with the gas flowing through the two catalyst beds

in radial direction.

4.9 PROCESS CONDENSATE TREATMENT

During operation of the ammonia plant small amounts of ammonia are formed in

the secondary reformer, furthermore small amounts of methanol are formed in the

CO converters. Together with CO2 present in the raw synthesis gas, these are

stripped off in the process condensate stripper .The impurities, CO2, NH3 and

methanol are stripped off the condensate by means of MP steam.

The MP steam with the impurities leaving the process condensate stripper will be

used as process steam in the primary reformer.

15

4.10 PROCESS DESCRIPTION USING RLNG AS FEED

The plant was originally designed based on steam reforming of naphtha and using

naphtha as fuel. The present revamp enables the plant to operate with LNG feed,

naphtha feed and mixed feed. LNG or naphtha are used as fuel for the feed

preheaters and primary reformer. The revamp has resulted in addition of new

pieces of equipment and modification of some of the process parameters in the

desulphurization and reforming sections. The major changes are the following

- Addition of an LNG Preheater (H 206) upstream the existing H 205

- Addition of a Sulphur Absorber (R 202A) upstream the existing absorber (R

202)

- Addition of LNG fuel preheater (E 207)

4.10.1 AMMONIA PLANT

In the plant, ammonia is produced from synthesis gas containing hydrogen and

nitrogen in the ratio of approximately 3:1.

Besides these components, the synthesis gas contains inert gases such as argon

and methane to a limited extent.

The source of H2 is steam and the hydrocarbons in the natural gas. The source of

N2 is the atmospheric air. The source of CO2 is the hydrocarbons in the natural

gas feed. The main function of the plant is illustrated in the following sketch:

Fig.4.10.1.1.Plant Layout

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4.10.2 DESULPHURIZATION SECTION

Since the gas contains both H2S and organic sulphur compounds, the

desulphurization takes place in two stages. The organic sulphur compounds are

converted to H2S in the Hydrogenator (R 201), and the H2S absorption takes place

in the sulphur absorbers (R 202 and R 202 A). After desulphurization, the content

of sulphur is less than 0.1 ppm.

Fig.4.10.2.1.Desulhpurization Section

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4.10.3 FEED PREHEATING

The LNG feed is preheated to 380oC in the newly added LNG heater (H 206),

which is an LNG fired heater. The existing Process Feedstock Preheater (E 216)

and Process Feedstock Superheated (H 205) remain as originally and are only in

operation when naphtha feed is used.

4.10.4 HYDROGENATION

The preheated natural gas is fed to the Hydrogenator (R 201). The vessel contains

Topsoes hydrogenation catalyst TK-550, which is a cobalt-molybdenum based

catalyst.TK-550 catalysis the following reactions:

RSH + H2 2S

R1SSR2 + 3H2 1H + R2H + 2H2S

R1SR2 + 2H2 1H + R2H + H2S

(CH)4S + 4H2 4H10 + H2S

COS + H2 2S

Where R is hydrocarbon radical.

The hydrogenation catalyst must not get in contact with hydrocarbons without the

presence of hydrogen. The result would be poor conversion of the organic sulphur

compounds causing an increased sulphur slip to the reforming section. In case

natural gas containing CO and CO2 is fed to the Hydrogenator, the following

reactions will take place:

CO2 + H2 2O (shift reaction)

CO2 + H2 2O

Therefore, the presence of CO, CO2 and H2O influences the sulphur slippage from

the downstream sulphur absorber. The TK-250 catalyst is in oxidised state at

delivery and resumes its activity when sulphided. In the sulphide state the catalyst

is pyrophoric and it must not be exposed to air at temperatures above 70oC.When

operating with LNG feed, water needs to be added to the preheated natural gas

upstream the Hydrogenator (R 201) to avoid risk of hydrocracking in the

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hydrogenation catalyst, TK-550.The target is to achieve a water concentration of

0.1 mole% H2O in the natural gas.

4.10.5 H2S ABSORPTION

The hydrogentated natural gas is fed to the sulphur absorbers: the existing R 202,

and the newly added R 202 A. Since the LNG feed contains a greater amount of

sulphur than naphtha, it has been necessary to add R 202 A to ensure a

desulphurization lifetime of 2 years. R 202 A is placed upstream and R 202

downstream. R 202 acts as a guard in case of sulphur breakthrough from R 202 A

or in case R 202 A is taken out of service for catalyst replacement. Each vessel

has one catalyst bed, which contains HTZ-3 catalyst. This zinc oxide catalyst is

in the form of 4 mm extradites. The normal operating temperature is

approximately 380oC. The zinc oxide reacts with the hydrogen sulphide and

carbonyl sulphide in the following equilibrium reactions:

ZnO + H2 2O

2

The catalyst is not reacting with oxygen or hydrogen at any normal temperature.

Zinc sulphide is not pyrophoric and no special care during unloading is required.

Steam operations should not be carried out in R 202 and R 202 A since the zinc

oxide would hydrate and it would then be impossible to regenerate the ZnO

material in the reactor. The sulphur content in the natural gas leaving the final

desulphurisation is reduced to less than ppm by weight.

4.10.6 REFORMING SECTION

In the reforming section, the desulphurized gas is converted into synthesis gas by

catalytic reforming of the hydrocarbon mixture with steam and addition of air.

The steam reforming process can be described by the following reactions:

(1) CnH2n+2 + 2H2 n-1H2n + CO2 + 3H2 - heat

(2) CH4 + 2H2 2 + 4H2 - heat

(3) CO2 + H2 2O - heat

19

Reaction (1) describes the mechanism of reforming the higher hydrocarbons,

which are reformed in stages to lower and lower hydrocarbons, finally resulting

in methane, which is reformed as shown in reaction (2). The heat input required

for the reverse shift reaction (3) is very small compared to the heat input required

for reactions (1) and (2). The reactions take place in two steps, primary reforming

and secondary reforming as illustrated in figure 3:

Fig.4.10.6.1.Reforming Section

After reforming section, ammonia gas is synthesized as same as naphtha used as

fuel. Then after synthesis of ammonia gas it pumped to the atmospheric storage

tank where it is stored in refrigerated condition because its boiling point is very

low.

20

CHAPTER 5

HAZARDS IDENTIFIED

The manufacture of ammonia involves processing of hydrocarbons under high

temperature, high pressure conditions in the presence of various catalysts,

chemicals etc.

Hazards Identified are as follows:

Fire / Explosion Hazard

Glands/seal leaks in valves, pumps, compressors handling hydrogen,

natural gas, naphtha, synthesis gas etc.

Hose/pipe failure, leakage from flanged joints carrying combustible gases,

vapours, liquids.

Fire box explosions in furnace

Leakage of petroleum products during tanker unloading operations.

Overflow from storage tanks.

Overheating / pressurization of storage tanks.

Improper earthing / lightning protection of storage tanks and pipelines.

Improper sealing of floating roof tanks.

In adequate / improper breather valves leading to tank failures.

Fire Box Explosion in cracker Furnace

High / Low Temperature Exposure Hazards

Burns due to contact with hot surfaces of pipelines, equipments, etc. or

leaking steam lines, process fluids at high temperature.

Frost bite due to contact with anhydrous liquid ammonia at -33 deg. C

Burns due to contact with pyrophoric catalyst.

Toxic Chemical Exposure Hazards

Asphyxia due to inhalation of simple asphyxiants like CO2 , N2, H2, CH4,

naphtha etc. and chemical asphyxiants like CO, NH3, Nickel carbonyl,

V2O5, Hydrazine, NOx, SOx, H2S etc.

21

Acute toxicity due to inhalation of catalyst dusts containing heavy metals

like Ni, Cr, CO, Mo, Fe, Zn, Alumina etc. and silica gel molecular sieves,

insulation fibers/dusts

Other Hazards

Poor House Keeping

Bund wall damaged in storage areas

High Noise

High Vibrations

Steam Leakage from Condensate Pipe

Pipes are corroded may easily subjected to rupture

Fall from Height

Hydrocarbon Exhausts if burner not functioning

Spillage of Chemical during unloading of Naphtha

LNG leakage during pumping

Unsafe acts by worker during regular routine maintenance work were noted

Improper guarding of suction area of blowers

Damages in Flame Arrestors

5.1 DANGEROUS OCCURRENCE IN AMMONIA PLANT

When we are in the Plant there were two dangerous occurrences happened.

Those two dangerous Occurrences were as follows:

Occurrence 1:

Ammonia gas leakage from the Pipeline which is inlet of the compressor.

Due to leakage of gas, pressure has been reduced to the inlet of compressor results

in tripping of compressor. The main cause for the leakage was due to the flange

failure connecting the pipe bends. Flange failure happen because of improper

maintenance and also there is no arrangements for finding the smaller leak in

22

flanges. Ammonia gas released which is less than TLV hence no harm or injury

occurred to workers. Leakage stopped by shut-off valve closure.

Occurrence 2:

Gasket failure in the reactor door in the Secondary Reformer because of this

there was a huge leakage of synthesis gas into the atmosphere at ground level.

The synthesis gas which comprises of hydrogen and other gases which is highly

explosive. No ignition source available there hence no fire / explosion occurred.

The leakage had stopped by opening the reactor door and all gases escaped to

atmosphere.

5.2 MAJOR ACCIDENT HAZARDS

Storage of large amount of produced ammonia about 10,000 tons in

atmospheric storage tank in refrigerated condition. This is extremely hazardous

because if any leakage is there huge explosion / IDLH condition can be lead to a

catastrophic disaster. Also dealing with several raw materials such as naphtha,

RLNG, etc., which are highly hazardous if any leakage of them occurs may leads

to a major accident.

5.3 NAPHTHA MSDS

Naphtha is the raw material used for the production of Ammonia. It is a

liquid hydrocarbon, highly volatile, flammable, explosive and slightly toxic.

Physical properties

Specific gravity - 0.670

Carbon/hydrogen ratio - 5 : 3

Flash point - 21 -55 deg C

Auto ignition temp - 220 deg C

Health Hazard

Inhalation of concentrated vapour can cause intoxication and headache. Ingestion

may cause burning sensation and vomiting. Frequent contact of Naphtha with skin

can cause Dermatitis

TLV : 500 PPM

23

Fire & Explosion Hazard

It is highly flammable and forms explosive mixture with air.

LEL - 0.9 %

UEL -6.0 %

5.4 AMMONIA MSDS

Physical properties

Molecular weight - 17.03

Boiling point at 1 atm deg C - (-) 33.4

Vapour Density (Air= 1) - 0.60

Melting point deg C - (77.7)

Specific Gravity at 15.5 deg C - 0.62

Ignition temp deg C - 651

Health Hazard

Skin: Prolonged contact with the gas can cause skin damage. Contact

with liquid can lead to frost-bite.

Eyes: Extremely irritating can cause permanent damage.

Inhalation: Extremely irritating can cause permanent damage,

prolonged contact at high concentration can be fatal.

TLV - 25 PPM

STEL - 35 PPM

IDLH - 5000 PPM

Fire and Explosion Hazard

It forms explosive mixture with air.

LEL - 16 %

UEL - 25 %

24

CHAPTER 6

HAZARD IDENTIFICATION TOOLS AND EVALUATION

The Hazard Identification Tool used for evaluation of ammonia plant and

ammonia storage are FMEA, FTA and HAZOP.

6.1 FAULT TREE ANALYSIS

A logic tree for system behaviour may be oriented to success or failure. A

fault tree is of the latter type, being a tree in which an undesired or fault event is

considered and its causes are developed. A distinction is made between a failure

of and a fault in a component. A fault is an incorrect state that may be due to a

failure of that component or may be induced by some outside influence. Thus

fault is a wider concept than failure. All failures are faults, but not all faults are

failures.

A component of a fault tree has one of two binary states: essentially it is

either in the correct state or in a fault state. In other words, the continuous

spectrum of states from total integrity to total failure is reduced to just two states.

The component state that constitutes a fault is essentially that state which induces

the fault that is being developed.

As a logic tree, a fault tree is a representation of the sets of states of the

system that are consistent with the top event at a particular point in time. In

practice, a fault tree is generally used to represent a system state that has

developed over a finite period of time, however short. This point is relevant to the

application of Boolean algebra. Strictly, the implication of the use of Boolean

algebra is that the states of the system are contemporaneous.

Faults may be classed as primary faults, secondary faults or command

faults. A primary fault is one that occurs when the component is experiencing

conditions for which it is designed, or qualified. A secondary fault is one that

occurs when the component is experiencing conditions for which it is unqualified.

25

A command fault involves the proper operation of the component at the wrong

time or in the wrong place.

Fig.6.1.1 FTA Symbols

Fig.6.1.2. FTA Symbols

26

6.2 FAULT TREE ANALYSIS ON AMMONIA STORAGE

Fault Tree Analysis drawn using PTC windchill Quality Solution Software

Based on the top event in fault tree bottom events are brain-stormed. All possible

events that can lead to top event are included in the tree. Minimal cut sets are used

for calculation of results.

Fig.6.2.1.FTA Leakage of ammonia from storage tank

Fig.6.2.2.FTA Material Failure

27

Fig.6.2.3.FTA Overpressure in Tank

Fig.6.2.4.FTA Over filling

28

Fig.6.2.5 FTA High Temperature

Fig.6.2.6 FTA ERP Failure

29

6.3 RESULTS OF FTA

From the above drawn fault trees the minimal cut sets can be more than

400.So for cut sets that resulting in top event can be considered and a

probabilities are calculated. The result is as follows

Table.6.3.1 FTA Result

From the result we inferred that the probability values are very low for minimal

cut sets from fault tree analysis, this shows that likelihood of the leakage from

ammonia storage tank is very less. But if it occurs there will be a severe

consequences. Hence suggesting that all necessary precautions had to be taken.

Minimal Cut Set Probability

(271)(402)(253)(272)(191) 4.3E-7

(271)(802)(253)(272)(191) 2.3E-7

(271)(402)(233)(272)(191) 2.3E-7

(271)(402)(232)(272)(191) 2.3E-7

(271)(402)(231)(272)(191) 2.0E-7

(271)(402)(251)(272)(191) 2.0E-7

(271)(802)(252)(272)(191) 1.2E-7

(271)(802)(233)(272)(191) 1.2E-7

(271)(802)(232)(272)(191) 1.2E-7

(271)(802)(231)(272)(191) 1.1E-7

30

6.4 HAZOP

Hazard and Operability study - the process of assessing hazards and developing

control measures to prevent accidents involving toxic, flammable or explosive

materials to facilitate safe operation of major hazard installations. It takes a

representation of a system and analyses how its operation may lead to an unsafe

deviation from the intent of the system.

The next step of the assessment phase is to consider the deviations from normal

operations in systems, or operational malfunctions identified in the preliminary

hazard analysis (PHA) that could lead to a hazardous situation. This entails a

detailed examination of the system and mode of operation.

The hazard and operability study enables a critical in-depth evaluation of the

system and process classified as relevant in the preliminary hazard analysis. The

HAZOP technique questions systematically every part of the process in order to

establish how deviations from the intended design can occur and determines how

these deviations can give rise to hazardous situations.

The study is progressed from one part of the design to the next until the whole

plant has been examined. Possible deviations and all associated hazards identified

during the examination are then addressed if the solutions are obvious and not

likely to affect other parts of the design. However, additional information is often

required before modifications to designs can be made. The outcomes from

examinations will normally consist of a combination of decisions and additional

questions that have to be addressed by re-evaluations. This process will continue

until the desired outcome is achieved.

Guide words

Guide words are simply words used as keys to suggest the various ways in which

deviations from an intention can occur. A list and their meaning is provided.

31

GUIDE WORDS MEANING

NONE

No forward flow when there should be, i.e. no flow or

reverse flow

MORE OF

More of any relevant physical property than there should

be, e.g. higher flow (rate or total quantity), higher

temperature, higher pressure, higher viscosity, etc.

LESS OF

Less of any relevant physical property than there should

be, e.g. lower flow (rate or total quantity), lower

temperature, lower pressure, etc.

PART OF

Composition of system different from what it should be,

e.g. change in ratio of components, component missing,

etc.

AS WELL AS

MORE THAN

More components present in the system than there

should be, e.g. extra phase present (vapour, solid),

impurities (air, water, acids, corrosion products), etc.

REVERSE

A parameter occurs in the opposite direction to that for

which it was intended e.g. reverse flow.

OTHER THAN

Complete substitution e.g. sulphuric acid was added

instead of water.

EQUIPMENT

WORDS OTHER

What else can happen apart from normal operation, e.g.

start-up, shutdown, uprating, low rate running,

alternative operation mode, failure of plant services,

maintenance, catalyst change, etc.

Table.6.4.1 Guide Words

The GUIDEWORDS are applied to a range of process PARAMETERS. Usually

only a limited number of combinations of guidewords and process parameters are

used. The most common process parameters are shown in the Table and the four

in the first column are the ones most frequently used - FLOW, PRESSURE,

TEMPERATURE and LEVEL, others will be tested and used on a case by case

32

basis if required. Each guide word is combined with relevant process parameters

and applied at each point (study node, process section, or operating step) in the

process that is being examined. The following is an example of creating deviations

using guide words and process parameters:

GUIDE WORDS PARAMETER DEVIATION

NO + FLOW = NO FLOW

MORE + PRESSURE = HIGH PRESSURE

AS WELL AS + ONE PHASE = TWO PHASE

Guide words are applied to both the more general parameters (e.g. react, mix) and

the more specific parameters (e.g. pressure, temperature). With the general

parameters, it is not unusual to have more than one deviation from the application

of one guide word. For example, more reaction could mean either that a reaction

takes place at a faster rate, or that a greater quantity of product results. On the

other hand, some combinations of guide words and parameter will yield no

sensible deviation (e.g. as well as with pressure). With the specific

parameters, some modification of the guide words may be necessary. In addition,

we often find that some potential deviations are irrelevant because of a physical

limitation. For example, if temperature parameters are being considered, the guide

words more or less may be the only possibilities. The following are other

useful alternative interpretations of the original guide words:

or pressure

When dealing with a design intention involving a complex set of interrelated plant

parameters (e.g. temperature, reaction rate, composition, and pressure), it may be

better to apply the whole sequence of guide words to each parameter individually

than to apply each guide word across all of the parameters as a group.

33

6.5 HAZOP ON RLNG PIPELINE

Hazard and Operability Study was done in RLNG pumping pipeline.

RLNG is also being used as a fuel in the production of ammonia in FACT

ammonia plant. It is being pumped from Cochin Refinery Storage of LNG

through pipeline. It may involve several operability hazards to find out hazop was

used. Hazop sheet as follows:

Fig.6.5.1.Hazop sheet

34

Fig.6.5.2. Hazop Sheet

Fig.6.5.3. Hazop Sheet

35

6.6 FMEA

The purpose of an FMEA is to identify the failures which have undesired effects

on system operation. Its objectives include:

(1) identification of each failure mode, of the sequence of events associated with

it and of its causes and effects;

(2) a classification of each failure mode by relevant characteristics, including

detectability, diagnosability, testability, item replaceability, compensating and

operating provisions

The identification of the failure modes, causes and effects is assisted by the

preparation of a list of the expected failure modes in the light of (1) the use of the

system, (2) the element involved, (3) the mode of operation, (4) the operation

specification, (5) the time constraints and (6) the environment. The failure modes

may be described at two levels: generic failure modes and specific failure modes.

The example of set of generic failure modes: (1) failure during operation, (2)

failure to operate at a prescribed time, (3) failure to cease operation at a prescribed

time and (4) premature operation. As examples of specific failure modes, gives:

(1) cracked/fractured, (2) distorted, (3) Undersized, and so on.

The failure causes associated with each mode should be identified. The

failure effects involve changes in the operation, function or status of the system

and these should be identified by the analysis. Failure effects can be classified as

local or as end effects. Local effects refer to the consequences at the level of the

element under consideration and end effects to those at the highest level of the

system.

Where FMEA is to be applied within a hierarchical structure, it is

preferable to restrict it to two levels only and to perform separate analyses at the

different levels. The failure effects identified at one level may be used as the

failure modes of the next level up, and so on.

FMEA is an efficient method of analysing elements which can cause failure

of the whole, or of a large part, of a system. It works best where the failure logic

36

is essentially a series one. It is much less suitable where complex logic is required

to describe system failure. FMEA is an inductive method. A complementary

deductive method is provided by fault tree analysis, which is the more suitable

where analysis of complex failure logic is required.

To use the Risk Priority Number (RPN) method to assess risk, the

analysis team must, calculate the RPN by obtaining the product of the three

ratings:

RPN = Severity x Occurrence x Detection

The consequences of a failure as a result of a particular failure mode. Severity

considers the worst potential consequence of a failure, determined by the degree

of injury, property damage, or system damage that could ultimately occur.

The possible outcomes of FMEA hazard tools as follows:

Identification of any design weaknesses.

Identification of failure modes that are most likely to cause failure of the

product during operation.

Identification of failure modes that could lead to hazardous conditions.

Identification of the product times that are most likely to fail.

6.7 FMEA ON AMMONIA PLANT

FMEA was conducted in several items / components in ammonia plant and

their failure modes, effects, potential causes of failures, severity, occurrence,

detection and RPN (risk priority number) had been calculated for each of the

components. Based on RPN the suggestion has to be given which components

has likely to involve or withheld hazard and its risk is high. The FMEA table is

given below. In FMEA table which item having highest RPN has to be provided

first attention for hazard control.

37

Item Failure

Modes

Effects S Causes O D RPN Recommend

ed Action

Reactor

Gasket

Torn

Gasket

Leakage of H2 8 Wear,

Improper

Installation

8 1 64 Testing,

Proper

Installation

Flange Rupture,

Abraded

flange.

Leakage of NH3 5 Corrosion,

Over

pressure

4 1 20 Proper

Maintenance,

Maintain

Pressure

Pipelin

e

Cracks,

Bends,

Corrosion

Leakage of

flammable gases

leads to fire

9 High Stress,

Over

Pressure

7 3 189 Proper

Maintenance,

Pressure

gauges

Valves Breakage,

Jamming

Leakage, Build

up pressure if

jammed

7 Improper

Maintenanc

e, sudden

closure

9 1 63 Proper

Maintenance,

Interlock

system

provision

Welded

Joints

in Pipes

Weld

breaks-off

Leakage of

Chemical

8 Improper

design of

weld area

6 1 48 Design with

factor of

safety

Reactor Cracks,

Corrosion

Explosion, Fire 9 High

Pressure,

Control

failure

2 1 18 Provide

Control

Interlocks,

Pressure

gauges

Compr

essor

Tripping Leads to system

shutdown

3 Low

Pressure,

leakages etc

3 1 9 Maintain

pressure

Acousti

c Insul

ation

Loss of its

properties

High Noise

cannot be

attenuated

3 Environmen

tal

conditions

2 3 18 Replace

periodically

Table.6.7.1. FMEA Sheet

38

CHAPTER 7

CONCLUSION

Thus by visiting the plant several hazards were identified and those hazards

were evaluated by hazard assessment tools such as Fault tree analysis, Failure

Mode and Effect Analysis, and Hazard Operability study. From the evaluation,

some of the suggestions were given for ammonia plant and it includes design

changes for flange to compressor inlet, reactor gasket sealing should be replaced

and has to be checked frequently, the gas monitoring and detection system has to

be installed around the plant.

The Hazard analysis were conducted in both ammonia plant and storage

area. In which storage area is considered to be more hazardous but likelihood of

occurrence of accident in storage area is less. Even though likelihood of

occurrence is less the severity of the accident will be very disastrous in storage

area. Hence recommendations such as monitoring system has to be maintained

correctly, hydrants line and firefighting equipment has to periodically maintained.

Thus all the hazards of the plant and storage area was evaluated using

hazard assessment tools and required suggestions were given to the plant.

39

REFERENCE

Lees loss prevention in Process Industries by Sam Mannan

Hazard Evaluation Guidelines by Recht

Crowl DA, Louvar JF. (2001) Chemical Process Safety-

Fundamentals with Applications. 2nd ed., Prentice Hall PTR

Lees FP. (1996) Loss prevention in the process industries 2nd ed.,

Butterworth-Heinemann, London, A14/1-26