B.tech Project.cpd2014

8/13/2019 B.tech Project.cpd2014

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CHEMICAL PROCESS QUANTITATIVE RISK ANALYSIS

AND

MANUFACTURE OF PARA NITRO CHLOROBENZENE

A PROJECT REPORT

Submitted by

MOHD. IBRAZ HUSSSAIN (41502203009)RATNA RAMANI (41502203013)S.SRILAKSHMI (41502203016)

In partial fulfillment for the award of the degree

of

BACHELOR OF TECHNOLOGY

In

CHEMICAL ENGINEERING

S.R.M. ENGINEERING COLLEGE,KATTANKULATHUR-603 203, KANCHEEPURAM DISTRICT

ANNA UNIVERSITY: CHENNAI-600 025

MAY 2006


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ANNA UNIVERSITY: CHENNAI 600 025

BONAFIDE CERTIFICATE

Certified that this project report Part A "CHEMICAL PROCESS

QUANTITATIVE RISK ANALYSIS" and report

Part B- "MANUFACTURE OF PARA NITRO CHLOROBENZENE is the

bonafide work of MOHD. IBRAZ HUSSAIN (41502203009), RATNA RAMANI

(41502203013) and

S. SRILAKSHMI (41502203016) who carried out the project work under our

supervision.

Dr.R.KARTHIKEYAN Dr.R.KARTHIKEYAN

PROFESSOR SUPERVISOR

HEAD OF THE DEPARTMENT HEAD OF THE DEPARTMENT

CHEMICAL ENGINEERING CHEMICAL ENGINEERING

S.R.M.Engineering college S.R.M.Engineering college

Kattankulathur-603 203 Kattankulathur-603 203Kancheepuram District. Kancheepuram District.

ACKNOWLEDGEMENT

We take pleasure in expressing our heartfelt thanks to our Principal Prof. R.

Venkataramani, B.E., M.Tech. F.I.E., and Director Dr. T.P.Ganesan,

B.E.,(Lhons).,M.Sc.,(Engg.), for constantly looking into our needs and upgrading the

support system provided to students.


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We also take this opportunity to thank our HOD

Prof. Dr. R Karthikeyan, B.E., Ph.D., who through his busy schedule always provided

time to guide us and motivate us.

Also, we would like to thank our faculty members who gave us valuable and

timely inputs which helped us to bring this project to a successful completion.

ABSTRACT

Para nitro chlorobenzene is an important compound in chemical industry with

respect to dyeing and production industry especially.

A conservative approach has been employed in the manufacture of Para nitro

chlorobenzene, as the other methods of production available are employed only for

laboratory purposes.

This project deals with design aspects of equipments used, cost estimation and

project feasibility.


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TABLE OF CONTENTS

CHAPTER TITLE PAGE NO

ABSTRACT

1 INTRODUCTION 11.1 UNDERSTANDING RISK 11.2 SELECTED DEFINITIONS FOR

CPQRA 3

2 RELEVANCE OF THE TECHNIQUE 10CASE STUDIES2.1 CASE STUDY OF A DISTILLATION

COLUMN 102.1.1 Identification, Enumeration and 13

Selection of incidents2.2 INCIDENT CONSEQUENCE 18

ESTIMATION2.2.1 Flash, Discharge and Dispersions 18

Calculations2.2.2 Event Tress 232.2.3 Consequences of Incident 25

Outcomes2.3 INCIDENT FREQUENCY 30

ESTIMATION2.3.1 Frequencies of the Representative 30

set of Incidents2.3.2 Probabilities of Incident outcomes 332.3.3 Preparation of incident outcome 34

case frequencies2.4 RISK ESTIMATION 352.5 CONCLUSION 40

3 REVIEW OF RELATED LITERATURE 413.1 TORAP 41

3.1.1 The Accident Scenario general 41step

3.1.2 Consequence Analysis 423.1.3 Checking for higher degree of 42

accidents3.1.4 Characteristics of worst-accident 42

ScenarioCONCLUSION 44

APPENDIX 1 45APPENDIX 2 46


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ABSTRACT

Chemical Process Quantitative Risk Analysis is a relatively new methodology

that is a valuable management tool in the overall safety performance of chemical

process industry.

CPQRA techniques provide advanced quantitative means to supplement hazard

identification, risk assessment, control and management methods to identify potential

for incidents and evaluate control strategies.

TABLE OF CONTENTS

CHAPTER TITLE PAGE NO

ABSTRACT

LIST OF SYMBOLS

1 INTRODUCTION

1.1 BRIEF INTRODUCTION 53

2 PROCESS

2.1 PROCESS DESCRIPTION 552.1.1 Equipment Description 57

2.2 MATERIAL BALANCE 59

2.3 ENERGY BALANCE 64

2.4 DESIGN 67

2.5 PROCESS CONTROL AND 71

INSTRUMENTATION


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2.6 PLANT LAYOUT 74

2.7 COST ESTIMATION 79

2.8 PROCESS SAFETY 87

LIMITATIONS 96

CONCLUSION 96

LIST OF SYMBOLS

Hreaction - Heat of reaction (kJ)

Cp - Specific heat kJ

kgoC

T - Temperature difference

- Latent heat of varporisation

V - volume of the reactor (m3

)

VO - Volumetric flow rate of the reactor (m3/hr)

- Vapor flow rate (kmol/hr)

CHAPTER 1

INTRODUCTION

BRIEF INTRODUCTION

Understanding Risk


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Risk is a measure of potential for loss in terms of both likelihood(events/year) of the incident and the consequences (effects/year) of the

incident. Risk in an industry may be due to natural hazards and

infrastructure.

Flixborough, Bhopal, Piper Alpha and other accidentsemphasized the need for risk analysis.

The development of a quantitative estimate of risk based onengineering evaluation and mathematical techniques for

combining estimates of incident likelihood and consequences.

Chemical process quantitative risk analysis is a relatively newmethodology that is valuable as a management tool in the overall safety

performance of the Chemical Process Industry (CPI).

Chemical Process Quantitative Risk Analysis (CPQRA)techniques provide advanced quantitative means to supplement

hazard identification, analysis, assessment, and control and management

methods to identify the potential for accidents to occur and to evaluate

control strategies.


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A flow sheet is illustrated below to indicate the step-by- stepprocedure involved in CPQRA.

Selected Definitions for CPQRA

HazardA chemical or physical condition that has the potential for causing damage to

people, property or the environment (e.g. a pressurized tank containing 500 tonsof ammonia)

IncidentIncident can be defined as loss of containment of material orenergy(e.g. a

leak of 10 lb/sec of ammonia from a connecting pipeline to the ammonia tank,producing a toxic vapor cloud).This is pertaining to Risk Studies.

Event SequenceA specific unplanned sequence of events composed of initiating events

and intermediate events that may lead to an incident.

Initiating event

The first event in an event sequence (e.g. stress corrosion resulting inleak/rupture of the connecting pipeline to the ammonia tank)

Intermediate eventAn event that propagates or mitigates the initiating event during an event

sequence (e.g.: improper operator action fails to stop the initial ammonia leak and

causes propagation of the intermediate event to an incident, in this case theintermediate event could be a continuous release of Ammonia)

Incident outcomeThe physical manifestation of the incident; for toxic materials, the incident

outcome is a toxic release, while for flammable materials, the incident outcomecould be a BLEVE, flash fire, unconfined vapor cloud explosion, etc.


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Incident outcome caseThe quantitative definition of a single result of an incident outcome through

specification of sufficient parameters to allow distinction of this case from all othersfor the same incident outcomes (e.g. a concentration of 3333 ppm (v) of ammonia2000 ft downwind from a 10lb/sec ammonia leak is estimated assuming a 1.4 mph

wind and stability Class D)

ConsequenceA measure of the expected effects of an incident outcome case (e.g., an

ammonia cloud from a 10lb/sec leak under stability Class D weather conditions,and a 1.4 mph wind traveling in a northerly direction will injure 50 people)

Effect zoneFor an incident that produces an incident outcome of toxic release, the areaover which the airborne concentration equals or exceeds some level of concern.

The area of the effect zone will be different for each incident outcome case[e.g.,given an IDLH for ammonia of 500 ppm (v) , an effect zone of 4.6 square milesis estimated for a 10 lb/sec ammonia leak].For a flammable vapor release, thearea over which a particular incident outcome case produces an effect based ona specified overpressure criterion (e.g., an effect zone from an unconfined

vapor cloud explosion of 28,000 Kg of hexane assuming 1 % yield is 0.18 km2if an overpressure criterion of 3 psig is established).For a loss of containmentincident producing thermal radiation effects, the area over which a particularincident outcome case produces an effect based on a specified thermal damagecriterion[e.g., a circular effect zone surrounding a pool fire resulting from aflammable liquid spill, whose boundary is defined by the radial distance at

which the radiative heat flux from the pool fire has decreased to 5 kW/m2(approximately 1600 Btu/hr-ft2]

Likelihood

Likelihood can be defined as a measure of the expected probability or

frequency of occurrence of an event. This may be expressed as a frequency (e.g.,events/year), a probability of occurrence during some time interval, or a conditionalprobability (i.e., probability of occurrence given that a precursor event has

occurred, e.g., the frequency of a stress corrosion hole in a pipeline of sizesufficient to cause a 10 lb/sec ammonia leak might be 1 x 10 -3 per year; theprobability that ammonia will be flowing in the pipeline over a period of 1 yearmight be estimated to be 0.1;and the conditional probability that the wind blows

toward a populated area following the ammonia release might be 0.1)


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It is necessary to pay attention to the scope of a CPQRA, in order to satisfypractical budgets and schedules. If the scope is not clearly defined in advance, there is apossibility for the workload to explode. The concept of a STUDY CUBE has beenintroduced as shown above to relate scope, workload and goals. The three axes of thecube represent risk estimation technique, complexity of analysis and number ofincidents selected for study. Each axis of the cube has been arbitrarily divided into threelevels of complexity. These results in a total of 27 different categories of CPQRA,depending on what combinations of complexity of treatment are selected for threefactors. Each cell in the cube represents a potential CPQRA characterization. Howeversome cells represent a combination of characteristics that are more likely to be useful inthe course of a project or in the analysis of an existing facility

Risk estimation techniqueEach of the components of this axis corresponds to a study exit point .The

complexity and level of effort necessary increase along the axis-from consequence

through frequency to risk estimation.

Complexity of StudyThis axis presents a complexity scale for CPQRAs .Position along the axis is

derived from two factors

The complexity of the models to be used in a studyThe number of incident outcome cases to be studied

Number of incidentsThere are three groups of incidents used

Bonding Group-this group contains a small number of incidents that arecatastrophic by nature

Representative Set-it includes incidents from the either group of incidents.

Expansive List- it contains incidents in all three classes selected throughthe incident enumeration technique

The STUDY CUBE provides a conceptual framework for discussing factorsthat influence the depth of a CPQRA.


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CHAPTER 2

RELEVANCE OF THE TECHNIQUE

CASE STUDIES

2.1 CASE STUDY OF A DISTILLATION COLUMN

Consider a C6 distillation column, which is used to separate hexane and heptanefrom a feed stream consisting of 58 %( by weight and 42% heptane. The overhead

condenser, thermosyphon reboiler and accumulator are all included in this study. Thecolumn operating pressure is 4barg the temperature range is 130-160C from the top tothe bottom of the column respectively. The column bottoms and reboiler inventory is6000kg and there are about 10000kg of liquids on the trays. The condenser is assumedto have no liquid holdup and the accumulator drum inventory is 12000kg. The materialin the bottom of the column is approximately 90% heptane and 10% hexane and that atthe top is approximately 90% hexane and 10% heptane.


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Table

Physical properties Hexane Heptane

Boiling point (oC) 69 99

Molecular weight 86 100

Upper flammable limit (vol%) 7.5 7.0

Lower flammable limit (vol%) 1.2 1.0

Heat of combustion (J/kg) 4.5x107 4.5x107

Ratio of specific heats, 1.063 1.054

Liquid density at boiling point (kg/m3) 615 614

Heat of vaporization at boiling point (J/kg) 3.4x105 3.2x105

Liquid heat capacity (J/kg/ok) 2.4x103 2.8x103


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The plant layout and surroundings The wind rose

The study objective is to estimate the risk to the residential community fromthe fractionation system from both individual and societal risk perspectives.

In order to limit the number of calculations, only one average weathercondition is considered a wind speed of 1.5 m/s and F stability- representing a worstcase weather condition with a reasonable probability of occurrence. The wind roseused in this example, gives the probability of wind from each of eight directions.


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2.1.1 Identification, Enumeration and Selection of incidents

An initial list of incidents is listed to consider all possible breaks orruptures of items of equipment which would lead to a loss of

containment

The initial list is modified to produce a revised list which excludesproblems such as polymerization, corrosion, over pressurization pertaining

to this distillation column.

Each vessel may break or rupture in a number of ways. A pipebreak may be of any size from a pin hole to a full bore rupture and may

be in any position between the pipe ends.

The spectrum of incidents is reduced to a Representative Set ofIncidents. Possible pipe failures are represented by either full bore ruptures

or holes of 20% of the pipe diameter.

Flange leaks, pump seal leaks do not cause any long distance effectsbut may result in a pool fire. Diking around the column limits the pool size to

10m2.

Incident outcomes such as fire and explosions should beconsidered since the material is flammable.

The final choice of incidents is modeled based on the following factors:

the size of the release whether the release is instantaneous or continuous whether the release is liquid or vapor The revised list of incidents include: Complete Rupture Column Accumulator Reboiler Condenser


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Liquid leaks(full bore rupture and hole equivalent to 20% ofdiameter)

Column feed line Reboiler feed line Heptane pump(pump 2) suction line(including flanges and pump) Heptane pump(pump 2)discharge line(including flanges) Condenser discharge line Reflux pump (pump1)suction line (including flanges and pump) Reflux pump(pump1) discharge line (including flanges) Shell leak(of column, accumulator, reboiler or condenser) of holesize equivalent to 20% of pipe diameter only.

Vapor leaks(full bore rupture and hole equivalent to 20% of diameter) Column overhead line Reboiler discharge line Shell leakage (of the column, accumulator, reboiler orcondenser) of hole size equivalent to 20% of pipe diameter only.

Assumptions pertaining to Representative List of Incidents

a. It is assumed that automatic isolation exists at the system boundaries suchthat no additional fuel other than that present in the system at the time of incident

contributes to the release. Hence an instantaneous failure of one vessel will lead to

the rapid release of the entire contents of all other connected vessels. It may be

noted that there are no automatic isolation valves with in the system.

b. It is assumed that all liquid lines have a diameter of 0.15m.Discharge ratefrom these lines is used to determine whether full bore rupture of these lines can be

treated as an instantaneous or continuous release. Here releases close to the

vessel are better approximated by the liquid discharge model as compared

to two-phase discharge model. Discharge equation for continuous releases from

the 0.15m diameter line is :


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GL= Cd A !(2(p-pa) / ! + 2 g h )1/2

GL= Liquid discharge rate (kg/s)

Cd=discharge coefficient (0.61 for liquids)

A = hole cross-sectional area ( for 0.15m diameter pipe)=0.0176m2

!=liquid density (615 kg/m3)

p=upstream pressure (5 bar=5*105N/m2)

pa=down stream pressure(1 bar = 1*105N/m2)

h=liquid head (assumed to be negligible)

g= acceleration due to gravity (9.8 m/s)

It has been calculated that discharge rate is 240 kg/s bysubstituting all the above values in equation.

Flow rate can double if pipe breaks in such a way that flow isunimpeded from both ends.

It is estimated that at the initial rate the entire contents of column,reboiler and accumulator would be emptied in 2 minutes. But due to

pressure decrease in the system, it takes a larger time to empty the

contents.

It is considered reasonable to treat full bore ruptures of liquidlines in the same manner as a catastrophic failure of any vessel in the

fractionating system.

c. Vapor lines are 0.5m in diameter.A quick estimate of the discharge rate canbe used to establish whether the full bore rupture of these lines can be treated as

an instantaneous or continuous release. It is determined whether flow is sonic in

order to estimate the actual discharge rate from a catastrophic break in the gas

piping.

rcrit=(("+1)/2)("/("-1))

Where


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"= gas specific heat ratio(1.063 for hexane, 1,054 for heptane)

rcrit=1.687 for hexane

rcrit=1.682 for heptane

Sincep=5*105N /m2 (absolute)

pa=1*105N/m2(absolute)

p/pa=5.0 > rcrit= 1.687

Therefore, vapor discharge will be sonic. For sonic flow the discharge rate is

given by

Gv=CdA p #/ $o

Where

Gv= gas discharge rate for choked vapor flow (kg/s)

Cd= discharge coefficient (assumed to be 1 for gases)

A =hole cross-sectional area ( for 10% of 0.5m pipe,m2)

p=absolute upstream pressure (N/m2)

$o =sonic velocity of gas at T =(RT"/M)1/2

#=flow factor = "(1/rcrit)("+1)/2")

M= molecular weight (86 for hexane, 100 for heptane)R=gas constant (8310 joules/kg-mole/K)

T=upstream temperature (403K for hexane, 433K for heptane)

"=gas specific heat ratio (1.063 for hexane, 1.054 for heptane)

rcrit=1.687 for hexane, 1.682 for heptane

The vapor discharge rate is 303 kg/s for pure hexane and 320 kg/sfor pure heptane. Therefore, full bore ruptures of vapor lines are also

treated the same as a catastrophic failure of any vessel in the fractionatingsystem.

Representative List of Incidents:


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a. a catastrophic failure of the column, reboiler, condenser, accumulator, orany full bore liquid or vapor line rupture

b. a liquid release through a hole of diameter equal to 20%of a 0.15m diameterline

c. a vapor release through a hole of diameter equal to 20% of a0.5m diameterline

2.2 INCIDENT CONSEQUENCE ESTIMATION

2.2.1 Flash,Discharge and Dispersions Calculations (Incidents A,B & C)

Flash discharge and dispersion calculations are carried out for the Incidents A,B and C that are defined above.

Incident A : A Catastrophic failure

In the event of catastrophic failure of one of the vessels or full bore line

rupture; it is assumed that the entire contents of the column, reboiler, condenser, and

accumulator, are lost instantaneously. In the following calculation, the flash fraction is

determined assuming the column reboiler and accumulator contains pure heptane and

pure hexane, respectively, rather than mixtures.

Fv=Cp((T-Tb)/Hfg)

Where

Fv= fraction of fluid flashed to vapor

Cp= average liquid heat capacity (range T to Tb)(2400J/kg/K for hexane, 2800

J/kg/K for heptane)

T= operating temperature (130C for hexane, 99C for heptane)

Tb=atmospheric boiling point (69C for hexane, 99C for heptane)


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Hfg= latent heat of vaporization at Tb (3.4x105 J/kg for hexane, 3.2x105

J/kg for Heptane)

The calculated flash fractions are 0.43 for hexane and 0.51 for heptane.Therefore, both of these materials exhibit a flash fraction of roughly 0.5. It is

reasonable to assume that all of the hexane and heptane released will release as gas and

aerosol .It is further assumed that the aerosol droplets are small enough to remain

suspended and evaporate instead of raining out onto the ground. DENSE CLOUD

MODEL is used to calculate the dispersion of the instantaneous release of the

mentioned gases. Since thermo physical properties of hexane and heptane are similar,

the dispersion calculations are based on hexane that comprises approximately 2/3 of

the inventory of the system. The release is supposed to consist only of gas and aerosoldroplets that eventually evaporate into cloud and hence an all gaseous release is chosen

for dispersion analysis. The temperature used is 69C , which is the temperature to

which hexane liquid will flash when released to the atmosphere. It is also necessary to

estimate the initial dilution, which is the number of volumes of air containing one

volume of gas in the cloud after expansion to atmospheric pressure and before heat

transfer and dispersion processes begin. A dilution factor of ten is chosen. The initial

cloud radius is set equal to height, which is the most common default for top-hat

models.

Incident B & C: Liquid and Vapour Release from Hole in Piping

For liquid release, the flash fraction is same as that considered for incident A

i.e. 0.43 for hexane and 0.51 for heptane. It is assumed that entire release is a gas and

aerosol cloud, with no liquid rainout.

The discharge rate for the liquid release (incident B) can be estimated usingequation and assuming a hole diameter of 0.03m.The resulting rate discharge rate is 9.6

kg/s.


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The discharge rate for gaseous release i.e. incident C can be estimated using

equation assuming a hole diameter of 0.12m. The discharge rate is calculated as 12.6

kg/s.

Since both releases are gaseous and discharge is similar incidents B and C are

combined and on average release rate of 11 kg/s is obtained. Top hat dense cloud

model of WHAZAN is used to calculate dispersion. The flammability zone from

continuous release will extend in residential area.


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This is the output obtained in case of instantaneous heavy gas dispersion

W H A Z A N***********

HEAVY CLOUD DISPERSION MODEL****************************

Copyright (C)DNV Technica Ltd.

Date 28 Sep 1996 Time 02:53

Instantaneous release of n-Hexane (Gaseous)

Mass released : 28000. kgInitial flash : .000

Temp. after release : 342.0 KMolecular weight : 86.17Boiling point : 344.6 KSpecified lower conc.: 10000.000 ppmInitial dilution : 10.0 TimesFraction liquid : .000Initial cloud temp. : 308.0 KInitial cloud conc. : 78912.050 ppmInitial density : 1.317 kg/cu mInitial radius : 32.1 mInitial volume : 104011. cu mInitial height : 32.1 mSurface roughness : .100

Ambient temperature : 293.0 KRoughness length : .18 m

Air density : 1.196 kg/cu mRelative humidity : 80. %

Wind speed : 1.5 m/sMixing ratio : .012Pasquill category : F

TIME DISTANCE CLOUD CLOUD C/L CLOUDDOWNWIND RADIUS HEIGHT CONC. TEMP.

(s) (m) (m) (m) (ppm vol) (K)

.0 .0 32.1 32.1 78912.050 308.03Forced convection from .0 m

6.7 10.0 58.6 19.9 37354.630 300.7413.3 20.0 76.6 16.0 26933.910 298.1920.0 30.0 91.3 13.9 21768.740 297.0426.7 40.0 104.0 12.5 18586.480 296.3633.3 50.0 115.4 11.5 16387.550 295.91


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40.0 60.0 125.8 10.7 14759.090 295.5846.7 70.0 135.4 10.1 13497.570 295.3353.3 80.0 144.4 9.6 12483.410 295.1360.0 90.0 152.9 9.2 11644.780 294.9766.7 100.0 161.0 8.8 10935.520 294.8373.3 110.0 168.7 8.5 10325.010 294.71

10000.000 ppm vol concentration reached 289.4 m at time 77. s


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This is the output obtained in case of continuous heavy gas dispersion

W H A Z A N***********

HEAVY CLOUD DISPERSION MODEL****************************

Copyright (C)DNV Technica Ltd.

Date 4 Oct 1996 Time 00:40

Continuous release of n-Hexane (Gaseous)

Rate of release : 11.00 kg/sInitial flash : .000Duration : 100.0 s

Temp. after release : 342.0 KMolecular weight : 86.17Boiling point : 344.6 KSpecified lower conc.: 12000.000 ppmInitial dilution : 10.0 TimesFraction liquid : .000Initial cloud temp. : 308.0 KInitial cloud conc. : 78912.050 ppmInitial density : 1.317 kg/cu mInitial semi-width : 3.7 mCross sectional area : 27. sq mInitial height : 3.7 mSurface roughness : .100

Ambient temperature : 293.0 KRoughness length : .18 m

Air density : 1.196 kg/cu mRelative humidity : 80. %

Wind speed : 1.5 m/sMixing ratio : .012Pasquill category : F

TIME DISTANCE CLOUD CLOUD C/L CLOUDDOWNWIND RADIUS HEIGHT CONC. TEMP.

(s) (m) (m) (m) (ppm vol) (K)

.0 .0 3.7 3.7 78912.050 308.03Forced convection from .0 m

6.7 10.0 12.4 2.3 36603.000 300.2313.3 20.0 18.8 2.0 28127.050 298.0220.0 30.0 24.3 1.8 23755.340 296.9326.7 40.0 29.3 1.7 20884.200 296.24


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33.3 50.0 34.0 1.6 18778.020 295.7440.0 60.0 38.4 1.6 17110.050 295.3646.7 70.0 42.6 1.5 15732.440 295.0653.3 80.0 46.6 1.5 14556.420 294.8160.0 90.0 50.5 1.5 13527.630 294.6066.7 100.0 54.2 1.5 12611.990 294.42

12000.000 ppm vol concentration reached 107.4 m at time 72. s


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2.2.2 Event Trees

A number of different outcomes are possible for incidents A, B, C depending

on

If and when ignition occurs Consequences of ignition Two events have been drawn below to illustrate the incidentoutcomes of these releases.

Though ignition may occur at a number of positions depending onignition sources it.

It is assumed that the immediate ignition will cause a BLEVE from an

instantaneous release and a jet fire from a continuous release. If ignition is delayed until

the cloud has developed, the consequences will be either a UVCE or a flash fire. From

the event trees, the following incident outcomes are identified for the risk analysis:

BLEVE due to immediate ignition of an instantaneous release UVCE due to delayed ignition of an instantaneous release Flash fire due to delayed ignition of an instantaneous release Jet fire from immediate ignition of a continuous release Flash fire due to delayed ignition of a continuous release


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Event tree for incident A

C o n t in u o u s

R e l e a s e

I m m e d i a t e I g n i t io n

N o I m m e d ia t e I g n it io n

D e la y e d I g n i t io n

N o I g n it io n

F l a s h F i r e

J e t F i re

T o x ic E f f e c t s

N o C o n s e q u e n c e s

Event tree for incident B and C


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2.2.3 Consequences Of Incident Outcomes

The consequences of incident outcomes are calculated in the following sections.

The discrete zone approach is used to define flammable effects. It is assumed in thisapproach that within a zone people are assumed to be fatalities and outside the zonepeople are assumed to be non-fatalities. This method overestimates the proportion offatalities within the zone and underestimates them beyond it. The zones of fatal effectsfor various incident outcomes are calculated as follows:

Incident Outcome No.1: BLEVE due to immediate ignition of anInstantaneous Release.

Consider a BLEVE involving 28,000 kg of hexane (M), the followingparameters that is peak BLEVE diameter, BLEVE duration and center

height of BLEVE are calculated from following equations as shown below

Peak BLEVE diameter (Dmax) =6.48 x M 0.325= 181m BLEVE duration (tBLEVE) = 0.825 x M 0.26 = 12s Center height of BLEVE (HBLEVE) = 0.75 x Dmax= 136m

For duration of 12s, the incident radiation required for fatality ofan average individual of an average individual is approximately 75kW/m2

.This is derived from the figure that is for the 50% fatality line at 12s.

The incident radiation from a BLEVE is given by equation

QR = %E F21

Where%= transmissivity

F21= view factorE = surface emitted flux (kW/m2)

The transmissivity is given by equation given below!= 2.02 (P wx)

-0.09

Where


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Pw= water partial pressure at ambient conditions (N/m2)

x = path length between flame surface and receiver (m)

The path length x is calculated asx = ( H2BLEVE+ r

2)1/2- 0.5 * Dmax= (1362+ r2)1/2 90.5

Where r is the horizontal distance from the column to the receiver

Assuming Pw = 2820 N/m2 , substituting in equation no.then the equation reduces to

%= 0.99 ((1362+ r2)0.5 90.5) -0.09

Consider the equation

F21= D2/ 4r2

Now, substitute D = Dmaxin the above equation and we getF21= 8190 r

-2

From an energy balance on the emitted energy we haveE = (Eradx M x He) / &x D

2maxxt BLEVE

Erad= 0.25 and heat of combustion for hexane is 4.5x 10+7J/kg. Therefore, E = 255 kW/ m2.This value may be

entered into the expanded equation.

QR= 0.99 ((1362+ r2)0.5- 90.5) -0.09x 8190 x r-2x 255

For a radiation level QRof 75 kW/m2, this equation may be solved byiteration to give r = 135m.Therefore,the area of fatal effect is a circle of

radius 135m, centered on column which would extend into the residential

area.

Incident Outcome No.2: UVCE due to delayed ignition of an Instantaneous

Release.


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This incident outcome involves 28,000 kg of hexane. The equivalentmass of TNT is given by the equation given below.

Hence, the equivalent mass of TNT is 27,400 kg. The use of an empirical explosion yield of 0.1 should represent areasonable worst case result for an explosion incident outcome.

An overpressure of 3 psi is used to calculate the extent of fataleffects.

Hence the area of fatal effect for a UVCE of 28,000 kg of hexane isa circle of radius 239m, centered 85m downwind of the column, which

would extend well into the residential area.

Incident Outcome No.3: Flash fire due Delayed Ignition of an Instantaneous

Release.

For flash fires, an approximate estimate for the extent of fataleffect zone is the area over which the cloud is above the LFL.

It is assumed that this area is not increased by cloud expansion duringburning.

This is a circular zone of 148m radius centered 85m downwind.

Incident Outcome No.4: Jet fire from immediate ignition of a Continuous

Release.

Rough calculations based on the method of Considine and Grint thatis very strictly applicable to LPG, yield an end hazard range of 50% lethality at

31m for a 100-s exposure.

This result suggests that there is no direct threat to the residentialarea and this incident outcome shall not be considered further.

Incident Outcome No.5: Flash fire due to delayed ignition of a Continuous

Release.

This gives a pie shaped hazard zone 127m long downwind (71mdistance + 56m radius) with 48 of arc.


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This incident can impact the residential area and has to beconsidered for further study.

The net result of these consequence effect calculations is that fourof the five Incident Outcomes could impact the Residential Area.

The next step in the calculation procedure is to determine Incidentand Incident Outcome Frequencies.

2.3 INCIDENT FREQUENCY ESTIMATION2.3.1 Frequencies Of The Representative Set Of Incidents

Data from the historical record have been used in order to estimatethe frequencies of the Representative Set of incidents.

In this case the column, vessels, pipes and pumps are standard processequipment and historical failure rate data are available for such items.

The basic failure rate data are listed in Table below. For each itemof equipment, the frequencies of a number of different sizes of failure are

given. These are quoted per item year except for piping for which

frequencies are given per meter year.

Item Size of failure Failure Rate

Piping

Small '50mm diameter

Full bore rupture 20% of pipe

diameter rupture

8.8 x 10-7(m yr-1)

8.8 x 10-6(m yr-1)

Medium > 50mm

diameter

'150mm diameter


diameter rupture

2.6 x 10-7(myr-1)

5.3 x 10-6(myr-1)

Large > 150mm

diameter


diameter rupture

8.8 x 10-8(myr-1)

2.6 x 10-6(myr-1)

Fractionating system

(excluding piping)

Serious leakage Catastrophic

failure

1.0 x 10-5(yr-1)

6.5 x 10-6(yr-1)

Using Table, the numbers of vessels, pumps, and pipe lengthsincluded in the Representative Set of incidents, the frequencies are calculated

as follows :-


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Incident A: Instantaneous Release. This incident includes the following failures:

Catastrophic rupture of any component in the fractionating system Catastrophic (full bore) rupture of any pipework There is approximately 25 m of 0.5-m-diameter piping and 55 m of0.15-m equivalent diameter piping included in this incident. Hence, the

frequency is calculated as follows :

Catastrophic rupture of 6.5 x 10-6 = 6.5 x 10-6yr-1fractionating system

Full bore of55m of medium pipe 55 x 2.6 x 10

-7

= 1.4 x 10-5

yr-1

25m of large pipe 25 x 8.8 x 10-8= 2.2 x 10-6yr-1Total 2.3 x 10-5yr-1

Incidents B and C : Continuous Release.

This incident includes holes of 20% of the diameter for all pipingand serious leakage from vessels. There are approximately 25 m of large 0.5

m diameter piping and 55 m of medium 0.15-m-diameter piping included

in this incident. Hence, the frequency is calculated as follows:

Leaks from55 m of medium pipe 55 x 5.3 x 10-6= 2.9 x 10-4

25 m of large pipe 25 x 2.6 x 10-6= 6.5 x 10-5

Serious leakage fromfractionating system 1.0 x 10-5 = 1.0 x 10-5yr-1

Total 3.7 x 10-4yr-1

2.3.2 PROBABILITIES OF INCIDENT OUTCOMES

The Probabilities of each incident outcome is determined byassigning probabilities to all the branches of the event trees of figures.

Some of the probabilities are direction dependent. (ie., the proportion of

the residential area involved affects the probability of ignition).


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For this case, two event trees have been developed for eachindent one that considers wind directions toward the residential area

and one that considers all other directions. The results of this exercise are

shown in figure 8.15 through 8.18. For this case study, the branch

probabilities for these event trees have been derived using engineering

judgement.

In a real risk assessment better validated sources would be preferred.It is important that such assumptions are documented for later review and

sensitivity analyst if warranted. A summary of the values selected and their

justification is listed in tables given below Preparation of incident

outcome case frequencies.

2.3.3 Preparation of incident outcome case frequencies

The prior analysis of a revised list of potential incidents (under thecategories of complete rupture, liquid leaks and vapor leaks) gives

Representative Set of three potential incidents (Incidents A, B and C).

It is assumed that with minimal loss in accuracy, those incidentscan be characterized as a single catastrophic incident (Incident A) and a single

continuous release (Incidents B and C).

The event tree analysis developed the instantaneous andcontinuous release incidents to four specific incident outcomes that

can impact the residential area. These can be listed as:

Incident Outcomenumber

Incident outcome

1 BLEVE due to immediate ignition of an instantaneousrelease

2 UVCE due to delayed ignition of an instantaneous release

3 Flash fire due to delayed ignition of an instantaneous release4 Flash fire due to delayed ignition of a continuous release

The frequencies of incident outcome cases, which are dependent on winddirection, are calculated in table given below. In that table the headings are defined are

Incident - The incident from the Representative Set chosen for theAnalysis.


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Incident outcome - The incident outcomes related to a particularincident which were shown to have potential for public impact.

Incident frequency The frequency of each incident in theRepresentative Set

Incident outcome probability - The probability of an incident outcomebased on event tree analysis given that the probability of the incident is

1.0

2.4 RISK ESTIMATIONIndividual Risk

The individual risk in the area around the column is estimated from the above

incident outcome case frequencies and consequences effect zones (Chapter 4). The

discrete consequence effect zones were estimated previously.

Incident Outcome

1. BLEVE a circle of radius 135 m centered on the column2. UVCE a circle of radius 239 m centered 85m from the column3. Flash fire (instantaneous) a circle of radius 148 m centered 85 m from the

column4. Flash fire (continuous) a pie shaped section (48oangle) that extends a total of

127 m from the column. The radius is 56m centered on a point 71 m from thecolumn.

These four consequence effect zones have been superimposed over the plantlayout to scale in the east direction in Figure 8.19. From consequence considerationonly. The consequence effects, ranked in descending order, are UVCE, Flash fire(instantaneous). BLEVE, and Flash Fire (continuous).

The four consequence effects described above can be divided into 3 commontypes :

Circular shaped, centered on column (Incident Outcomes 1)Circular shaped centered 85 m from column (incident outcomes 2 and 3)Pie shaped, originating at column (incident outcome 5)

Each of these must be treated slightly differently in calculating individual risk,but it is straightforward to extend this procedure to any effect zone shape and position.


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Figures illustrate the general shape of the individual risk profile as a function of

distance, for each of the four incident outcomes, along any wind direction (including

the east direction that contains the residential area). The zero point in each of the

figures is the location of the fractionating system.

It is very important in the estimation of individual risk (and as will be shown

later, in the estimation of societal risk) that overlapping incidents be properly

considered. Thus, with the large UVCE consequence effect zone, consideration of only

the W to E wind case would greatly underestimate the risk for those living to the east as

UVCE incidentxs from all 8 directions contribute to the risk.

The calculation of the individual risk at any point assumes that the

contributions of all incident outcomes cases are additive. Therefore, the total individual

risk at each point is equal to the sum of the individual risxks from all possible incident

outcome cases.

The individual risk in this study is not symmetrical around the column because

of the directional probabilities of the wind and ignition. Ideally, an individual risk

contour could be developed that includes points in each of the eight wind directions.

However, in this study, the population is only situated east of the plant and an

individual risk curve will be developed only for that easterly direction.

Each of figures contains a set of distances for that incident outcome. Each

distance listed on a particular figure represents a subset of incident outcome cases that

reach that distance. However, other incident outcomes can also provide cases that


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apply at the same distance. Therefore, for every distance listed in figure a calculation

should be made that sums all of the total incident outcome cases that contribute at that

distance.

Table presents a summation of the individual risk for a distance of 0-63m in an

easterly direction from the column. All incident outcome cases contribute in this

calculation with the expection of Flash fire (continuous) wind directions N to S, NE to

SW, E to W, SE to NW and S to N.

Table has been developed to show the changes to total individual risk the result

at each discrete distance. The permits development of the Total (ndividual Risk Curve

in the East Direction.

Some observations on the results are :

1. The risk near the column has property been underestimated, sincesmall incidents that may contribute to the risk in this area have been excluded

from the analysis (e.g jet fire hazards).

2. The choice of only two places for ignition (immediate and delayeduntil the LFL concentration is reached) simplifies the real situation of

ignition points at intermediate locations due to residential areas, fired

process equipment, roads, etc. A different ignition distribution could be

considered, but with increased calculational burden.

3. The use of only one weather condition (F stability, 1.5 m/s windspeed) generally tends to overestimate risk at a given distance, because the

longest dispersion distances are usually associated with F stability, low

wind speed conditions.

4. The risk from UVCE is probably overestimated because of the highexplosive yield chosen.


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These assumptions have been chosen to provide a reasonable, but conservative,

risk estimate using a minimum number of manual calculations. Where the resulting

risk estimates indicate a potential problem, the analyst can decide whether some

simplifying assumptions should be made more realistic, and the calculations repeated.

However, each change in an assumption probably represents a significant increase in

the number of incident outcome cases. An alternative approach is to use a computer

tool that automates the calculation procedures, allowing analysis of a greater number of

incident outcome cases.

SOCIETAL RISK

The first step in the estimation of societal risk is to calculate the number of

fatalities for each incident outcome case. For this case study, consequence effect zones

are discrete (within the zone there will be 100% fatalities) and an assumption is made

that the residential area has a uniform population distribution. Therefore, the fraction

of residential area covered by each incident outcome case will represent the fraction of

200 fatalities which would result table summarizes these results.

The data in Table represent the raw information from which the societal risk

estimate may be developed. The data must be put into a cumulative frequency form in

order to plot the F-N curve. This is accomplished by rearranging the incident outcome

cases by descending number of fatalities and then calculating the frequency of having N

or more fatalities. This procedure is presented in table.


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The data in the first and last columns are plotted on logarithmic scales to

produce the F-N curve shown in Figure. Adding more incident outcomes cases will

produce a smoother curve because of the additional data points, but will not necessarily

produce significant upward or downward bias.

2.5 CONCLUSION

The largest contribution to individual risk near to the column is from flash fires

from pipe rupture equivalent to 20% of the pipe diameter. Remedial measures might

include more frequent inspection or monitoring of wall thickness, if significant

corrosion and/or erosion effects are anticipated.

The largest contributor to the societal risk, not unexpectedly, is from

instantaneous release of the contents and delayed ignition resulting in an unconfined

vapor cloud explosion.

The radius of the consequence zone is proportional to the 1/3 power of the

quantity released. Therefore, only a very major reduction in quantity has a significant

effect in reducing that radius. Nonetheless, additional remote isolation for the system

could be considered. Vessel and piping integrity is the major concern. Additional

ispection, perhaps utilizing different methods, could be considered.


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Finally, because of the magnitude of the societal risk, additional study could

consider other causes of vessel failure, such as overpressurization, that could lead to

identical consequences. These studies, probably utilizing FTA, could indicate whether a

threat of overpressurization is significantly higher than basic vessel failure and

engineering or procedural controls could be implemented to reduce that risk.

CHAPTER 3

REVIEW OF RELATED LITERATURE

3.1 TORAP

TORAP(Tool for Rapid riskAssessment in Petroleum refinery) A new toolfor conducting assessments in petroleum refineries and petrochemical industries. Thispackage is used to identify steps to prevent / manage accidents

TORAP involves the following main steps: The accident scenario general step Consequence Analysis Checking for higher degree of accidents Characterization of worst-accident scenario

3.1.1 The accident scenario general step

An accident scenario is basically a combination of different likely accidental

events that may occur in an industry. Such scenarios are generated based on the

properties of chemicals handled by the industry, physical conditions under which

reactions occur or reactants / products stored, geometries and material strength of

vessels and safety arrangement etc. External factors such as site characteristics &

metrological conditions are also considered.This step would help in the development of

more appropriate & effective strategies for crisis prevention & management.


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3.1.2 Consequence Analysis

This involves the assessment of likely consequences if an accident occurs. Theconsequences are quantified in terms of :Damage radii the radius of the area in which damage would readily occur.

Damage to propertyToxic effects

3.1.3 Checking for higher degree of accidents

Higher degrees of accident like secondary and tertiary accidents are moreprobable in petroleum refineries and petrochemical industries.The TORAP packageestimates the damage potential of secondary accident (provided it is higher than theminimum value) and its likelihood of causing third degree accidents.

3.1.4 Characteristics of worst-accident scenario

This is the final step in TORAP algorithm. This step determines the worst-accident scenario based on the results of a consequences analysis. This step helps todevise strategies to avert a crisis or to minimize its adverse impact if the crisis does takeplace.

AdvantagesCharacterization of accidents as primary, secondary, tertiary is possible

FLOW CHART indicating the procedure of TORAP


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CONCLUSION

Chemical process quantitative risk analysis is an effective management tool forcarrying out safety analysis in process industries.

In this study project a distillation column has been taken as the focus of interest

and detailed report, concerning the RISK posed by it, the incident outcomes possible

has been discussed.

Also TORAP, i.e method for risk assessment in refineries had been disused.

CHAPTER 1

INTRODUCTION

BRIEF INTRODUCTION

1-Chloro -4- nitrobenzene is produced and used in chemical industryand is not known to occur naturally.

It is used in the synthesis of industrial chemicals (e.g. para nitrophenol, para-nitro aniline, para-aminophenol, 4-nitroanisole, and

para-anisidine), pesticides (e.g.parathion methyl parathion, ethyl

parathion and nitrophen), the analgesic drugs phenacitin and

acetaminophen, and the antimicrobial drug dapsone which is

used to treat leprosy among other conditions.

1 Chloro 4 nitrobenzene is also used in the synthesis of 4-nitrodiphenylamine-based antioxidants for rubber.


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p-Nitrochlorobenzene is used as an intermediate for organic synthesis;p-nitrophenol, azo dyes and sulfate dyes, pharmaceuticals(such as

phenacetin and acetaminophen) and pesticides (such as nitrofen,

parathion) and rubber chemicals.


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Physical and Chemical Properties

1-Chloro-4-nitrobenzene is a crystalline yellow solid at room temperature with a

sweet odor and is slightly soluble in water (243 mg/L at 20oC).

Molecular Formula : C6H4ClNO2

Molecular Weight : 157.56

Chemical Class : nitroaromatic

Melting point : 82.6oC

Boiling point : 242oC

Vapor Pressure : 0.15mm Hg (at 30oC)

Synonyms

Para-chloronitrobenzene, 4-chloro-1-nitrobenzene, 4-nitrochlorobenzene, para-

nitrochlorobenzene, 1-nitro-4-chlorobenzene, 4-nitro-1-chlorobenzene.

REVIEW OF LITERATURE

Methods of preparing chlorontrobenzene include.

1. diazotisation of nitroanilines of replacement by chlorine

2. Reaction of phosphorous pentachloride with nitrophenols

But all these methods are applicable to laboratories and not of commercial

interest. Hence, manufacture of paranitrochlorobenzene from chlorination of

nitrobenzene is used for commercial purpose.

CHAPTER 2

PROCESS

2.1 PROCESS DESCRIPTION

Chlorobenzene is the main raw material used in the manufacture ofpara nitro chlorobenzene.

Cl

No2


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It is fed into a nitrator where chlorobenzene is nitrated usingnitrating acid. This acid is composed of 52.5 weight percent of H2SO4, 35.5

weight percent of HNO3 and 12 weight percent of H2O.

A slight excess of chlorobenzene usually is fed into the nitrator toensure that the nitric acid present is consumed to the maximum possible

extent. The reaction mixture flows from the nitrator into a separator or a

centrifuge where the organic phase is separated from the aqueous phase.

This aqueous phase or spent acid is drawn from the bottom andconcentrated and recycled to the nitrator, where it is mixed with nitric acid

and sulphuric acid immediately prior to being fed into the nitrator.

Crude nitro chlorobenzene is obtained at this stage which is mainly amixture of isomers. Further, purification is needed to obtain para nitro

chlorobenzene from the mixture of isomers which also contains small

quantities of chlorobenzene and sulphuric acid.

The crude nitro chlorobenzene flows through a couple of washer-separators where residual acid is removed by washing with dilute base

followed by final washing with water.

The product then is distilled to remove chlorobenzene from themixture of isomers. The bottom product which is a mixture of isomers

contains about 34 weight percent ortho nitro chlorobenzene, 65 weight

percent para nitro chlorobenzene and 1weight percent meta nitro

chlorobenzene.

The mixture is cooled to a temperature slightly above its freezingpoint and a large portion of para isomer slowly crystallizes and is

separated from the mother liquor. Thus para nitro chlorobenzene is

obtained in the form of crystals with very less impurities.


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The reaction time takes about 10-30 minutes and theoretical yield isabout 96-99 %.

2.1.1 Equipment Description

NITRATOR

The reaction vessels are acid resistant, glass-lined steel vesselsequipped with efficient agitators.

Optimum mass transfer of reactants is maintained by vigorousagitation. The reactors contain internal cooling coil which control the

temperature of the highly exothermic reaction.

CRYSTALLISER

The crystallizer used in this process is SWENSON- WALKERcrystallizer.

It consists of a open trough with a semi- cylindrical bottom, a waterjacket welded to the outside of the trough and a slow speed long pitch,

spiral agitator running at about 7 rpm and set as close to the bottom of the

trough as possible.


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Nitrator Acid

separator

Spent acid

reconcentration

Washtower(1)

Washtower(2)

Di

c

W aste water

treatment

Nitro c

(I

Salt + water

Cr

paranitro

Fresh

Sulphuric acid

Nitrating

Ac id

Chlorobenzene

Reaction mixture

Crude

Nitrochlorobenzene

Dilute baseNaOH Water

Spent

Ac id

FreshNitric acid


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2.2 MATERIAL BALANCE

NITRATOR

BASIS: 1000 kg/hr of nitrating acid.

The reaction given below takes place in the reactor.

C6H5Cl + HNO3 )C6H4ClNO2+ H2O

Composition of Nitrating Acid

Components Weight(kg) Molecular

weight(kg/kmole)

No. of moles

(in kmole)

HNO3 355 63 5.635

H2SO4 525 98 5.357

H20 120 18 6.667

Amount of chlorobenzene to be taken ( 20% excess) = 1.2 x 5.635

=6.762 kmoles

Products from Nitrator

H2SO4 = 5.357 kmoles

H2O = 6.667+(0.98 x 5.635) =12.98 kmoles

C6H4ClNO2= 0.98 x 5.635 = 5.522 kmoles

HNO3= 0.02 x 5.635 = 0.113 kmolesC6H5Cl = (0.02 x 5.635) + (0.2 x 5.635) =1.24 kmoles


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ii

WASHING

Input to wash tower 1

Crude Nitrochlorobenzene

C6H4ClNO2 = 869.7 kg

H2SO4= 26.25 kgH20 = 10.27 kg

C6H5Cl = 139.5 kg

Dilute base required to neutralize H2SO4completely

2NaOH + H2SO4 " Na2SO4+ 2H20

NaOH required = 2 x 0.2679 = 0.536 kmoles = 21.44 kg

Total input = 1760.72kgTotal output = 1760.72kg


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iii

Input to wash tower 2

C6H4ClNO2: 869.7 kg

Na2SO4:38.042 kg

H2O: 20.62 kg

C6H5Cl: 139.5 kg

Amount of water required to dissolve Na2SO4completely =96.48 kg


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iv

D = F ( x F x B ) / ( x D x B)

Input to Distillation Column

Feed contains: C6H5Cl = 139.5 kg

C6H4ClNO2= 869.7 kg

Total = 1009.2 kg

In mass fraction:

x F = 0.14 ; x D= 0.98 ; x B= 0.03

D= 116.85kg B= 892.35kg


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v

Crystallizer

Solubility of para C6H4ClNO2at 80oC is

kg para C6H4ClNO20.085

kg ortho C6H4ClNO2

Feed Mother liquor =328.25kgorthoC6H4ClNO2 orthoC6H4ClNO2=302.65kg=302.95kg para C6H4ClNO2=25.6kgpara C6H4ClNO2=562.93kg para C6H4ClNO2

crystals = 537.33kgTotal = 865.58kg Total = 865.58kg

ENERGY BALANCE

Crystallizer

Total =1009.2kgTotal =1009.2kg


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vi

*Hreaction = +(mcp*T)products+*Ho

reaction +(mcp*T)reactants

+(mcp*T)products = (mcp*T) C6H4ClNO2 - +(mcp*T)H2SO4+

(mcp*T)HNO3+(mcp*T)H2O+(mcp*T)C6H5Cl

= [(869.7 x 1.589) + (52.5 x 2.425) +

(7.12 x 2.941) + (219.4 x 4.186) +

(139.5 x 1.2104)] x (70.25)

= 1,69,347.5 KJ

*Horeaction = *Hf-products- *Hf reactant

*Hf product = [(-309.46 x 869.7) + (454.13 x 139.5)

+ (-8273.3 x 525) + (2747.47 x 7.12) +

(-68.3174 x 219.4)]

= 45,44,695.6 kJ

*Hf reactants = (454.13 x 760.72) + (-8273.3 x 525)

+ (2747.47 x 355) + (-68.3174 x 120)

= 30,30,862.9 kJ

*Horeaction = -45,44,695.6 (-30,30,862.9)

= -15,13,832.7 kJ

+(mcp*T)reactants = (mcp*T)C6H5Cl+ (mcp*T)H2SO4 + (mcp*T)HNO3

+ (mcp*T)H2O

= [(760.07 x 1.2104) + (525 x 2.425)

+ (355 x 2.941) + (120 x 4.186)] x (40-25)= 56104.13 kJ

*Hreaction = 169347.5 -1513832.7-56104.13

= - 1400589.3 kJ


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vii

Mass of cooling water required.

Heat to be removed = 1400589.3 kJ

(mcp*T)water = 1400589.3*T = 40

m (4.186)(40) = 1400589.3

m = 8364.7 kg.

Distillation column

Condenser Hot fluid: distillate

Cold fluid: water

Distillate = 116.85 kg. = 1.03 kmoles

Latent heat of distillate = 36564.65 kJ/kmol = 322.44 kJ/kmol

(m,)hot fluid = (mcp*T)cold fluid

116.85 x 322.44 = m x 4.186 x 20

mass of water required = 450 kg.

Reboiler

-,= ms,s

- = V- F(1-q))

q = 1

-= v = D(R+1) = 1.03(5.75+1) = 6.953 kmoles

-=6.953 kmoles = 788.5 Kg.

,avg.= 36885.88 kJ/kmol = 236.2 kJ/kg.

-,= ms,

788.5 x 236.2 = ms x2259.83

mass of steam required = 82.42 kg.

Crystallizer


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viii

Design summary:

Diameter of reactor = 0.56m

Length of reactor = 2.8 m

Heat from the crystallizer:

Q = Fcp*T + C,

= (865.58 x 1.589 * (245-80)) + (537.33*234.3)= 352838.5 kJ

cooling water requirement

Q = (mcp*T)cooling water

m = 352838.5/ 4.186 X (353-288)

= 1296.7 kg.

DESIGN

REACTOR DESIGN

Space time = %= 20 minutes

%= V / VO

VO = mo/!

= (760.72/1128) + (1000/1447.33)= 1.365m3/hr

V = 0.683 m3

Assumption: L/D = 5

(.D2 / 4)x L = O.683m3

D = 0.56 m

L = 2 .8 m

DISTILLATION COLUMN


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ix

Design Summary:

No of theoretical stages = 6

Column diameter = 0.72m

Column height = 5.85m

x 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

y 0 0.28 0.46 0.6 0.7 0.77 0.84 0.89 0.93 0.97 1

Where y = $x /1+($-1 )xLet $= 3.5

/= D(R+1)

D = 1.03 kmoles/hr

R = 5.75

/= 6.953 kmoles/hr

At the top

No. of moles of vapour = 6.953 kmoles/hr

Assuming ideal gas behaviour, VO= nRT / P = (6.953 x 0.082 x 405) /1

= 230.91m3/hr

Assumption: vapour velocity = 0.2 m/s

Cross sectional area = 230.91/ (3600 x 0.2) = 0.321m2

Column diameter = 0.64 m

At the bottom

No.of moles of vapour = 6.953 kmoles/hr

Vapour flow rate = (6.953 x 0.082 x 518 )/1 = 295.33 kmoles/hr

Cross sectional area = 0.41 m2

Column diameter = 0.72m

COLUMN HEIGHT

Assumption: plate efficiency = 50%

Plate spacing = 0.45m

No.of actual plates = (7-1)/ 0.45 = 12

Column height= ((12-1)+ 2) x 0.45 = 5.85 m


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x

Design Summary:

Area of the crystallizer =13.15m2

No of the sections = 6

CRYSTALLIZER DESIGN

Surface area required

Q =U A *Tlm

Where U = 250 kJ/hr m2K

*Tlm= (*T2 -*T1)/ln (*T2/*T1)= (165-65)/ln (165/65)

= 107.34

Area = 352838.35/(250 x 107.34)

= 13.15m2

Number of sections = total area / area of one section

Maximum length of 1 section is 5ft = 1.524m.

Assumption 1.5m2

of cooling surface per m length of crystallizer is available.Area of one section =1.5 x 1.524 =2.286m2

No of sections =13.15/2.286

=5.8


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xi

PROCESS CONTROL AND INSTRUMENTATION

The primary objectives of the designer when specifying instrumentation and

control schemes are:

1. Safe Plant Operation

a.To keep the process variables within known safe operating limitsb.To detect dangerous situations as they develop and to

provide alarms and automatic shut-down systems.

c.To provide interlocks and alarms to prevent dangerousoperation procedures.

2. Production rate

To achieve the designed output.

3. Product quality

To maintain the product composition within specified quality standards.

4. Cost

To operate at the lowest production cost, commensurate with the other

objectives.

REACTOR CONTROL

The schemes used for reactor control depend on the process and the type of

reactor. If a reliable on-line analyzer is available, and the reactor dynamics are suitable,

the product composition can be monitored continuously and the rector conditions and

feed flows controlled automatically to maintain the desired product composition and

yield. More often, the operator is the final link in the control loop, adjusting the


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xii

controller set points to maintain the product within specification, based on periodic

laboratory analysis.

Reactor temperature will normally be controlled by regulating the flow ofcooling medium. Pressure is usually held constant. Material balance control will be

necessary to maintain the correct flow of reactants to the reactor and flow of products

and unreacted, materials from the reactor.

INSTRUMENTATION

TEMPERATURE MEASUREMENT

The temperature measuring element in a control system for jacketed tank is

generally a thermocouple. The five most commonly used thermocouples are copper

constantan, iron constantan, chromel alumel, platinum platinum 13% rhodium,

platinum platinum 10% rhodium.

LEVEL MESUREMENT

The float- shaft type is employed either in open vessels. This method is suitable

for a wide range of liquids and semi-liquids. Difficulties are sometimes encountered

when the liquid deposits on the float and when the liquid level is foaming or turbulent.

FLOW RATE MEASURING

The industrial devices for flow rate estimation are common orifice meter,

venturimeter, pilot tube and the Rota meter. The piping system must be made ofspecial corrosion resistant material when corrosive fluids are used.

pH MEASUREMENT


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In this process we use the digital pH meters, these pH meters can measure the

pH of the solution accurately for two decimal places. These pH meters can be used

over wide range temperatures. These pH meters dont require additional current for the

working once they are dipped in the solution they measure the pH of the solution onthe display.

PLANT LAYOUT

Administrative

Block

Hospital

Canteen

P

A

RK

I

N

G

S

E

C

UR

I

T

Y

check

post

Transformer

Fire

Station

Training Academy

Health Club

Work shop

Water

Treatment

Area

Store

House

Quality Prod and control limit

Lab and testing area

Processing

Area


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PLANT LOCATION AND SITE LAYOUT

The location of the plant can have a crucial effect on the profitability of a

project, and the scope for the future expansion. There are many factors must beconsidered while selecting a suitable site. Some of the principal factors while selecting a

suitable site. Some of the principal factors which must be considered for the selection

of chemical process site are:

1. Area of development favored by the government and the incentives, whichare available.

2. The likelihood of finding suitable employees in the area and of wagesubsides.

3. The peculiarities of climate.4. Sources of electricity gas and water.5. Area of atleast 100 acres of level ground on good boulder clay free from

any danger of flooding.

6. Not sensitive environmental area.7. Besides fresh water, adequate water must be available for cooling purposes.8. Readily linked railway system.9. Besides readily linked road system.10.Near a responsible population centre.11.Local community considerations.12.Environmental impact and effluent disposal.13.Political and strategic considerations.14.Climate.15.Expansion possibilities.

SITE LAYOUT

The process units and ancillary building should be laid out to give the most

economical flow of materials and personal around site. Hazardous process must be

located at a safe distance from other buildings.


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Considerations must also be given to future expansion of the site. The ancillary

buildings and services required on site, in addition to the main processing

units(buildings),will include :

1. Storages for raw material and products : Tank farms andWare house

2. Maintenance workshops.3. Store for maintenance and operating supplies.4. Laboratories for process control.5. Fire stations and other emergency services.6. Utilities : steam boilers , compressed air , power generation ,

Transformer station.7. Effluent disposal plant.8. Offices for general administration.9. Canteens and other amenity buildings, such as medical centers.10. Regulatory laws.11. Taxes.12. Car parks.

RAW MATERIALS SOURCES

Careful considerations should be given to the sources of raw materials to be

used, method of delivery and storage facilities of raw materials.

WASTE PRODUCT DISPOSAL

Another aspect, which is gaining importance these days, is the environmental

considerations. Careful attention should be given to the nature of products to be

wasted, their quantity, available methods of disposal and the legislations governing the

disposal.


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Location can be an important factor for cost. If the bearing quality of the land

is low, considerable amount may be spent in piling support for heavy equipments or

multi-storied buildings. If the land is uneven and the site needs even level, the cost of

leveling may be considerable. Sometimes advantage can be taken of uneven levels so asto use gravity as a means of transportation of materials.

When planning the preliminary site layout, the process units will normally be

sited first and arranged to give a smooth flow of materials through various processing

steps, from raw material to final product storage. Process units are normally spaced at

least 30 meters apart. Administration offices and laboratories, in which a relatively large

number people will be working, should be located well away from potentially hazardous

process control rooms. The siting of the main process units will determine the layout ofthe plant roads, pipes, alleys and drains. Access roads will also be constructed for

operation and maintenance purpose. Utility building should be sited to give the most

economical run of the processing units. The main storage areas should be placed

between the loading and unloading facilities and the process units they serve. Storage

tanks containing hazardous materials should be sited at least 70 meter from site

boundary.

PLANT LAYOUT

The economic construction and efficient operation of a process unit will

depend on how well the plant and equipment specified on the process flow sheet is laid

out. The major principal factor that has to be considered while designing a plant layout

is as follows:

1. Economic considerations : Constructions and operating cost2. Damage to person and property an case of fire , explosion and3. toxic release4. The process requirements5. Convenience of maintenance.6. Safety7. Future expansion.


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8. Modular constructions.

It is also advisable to check up the insurance regulations from the view of

getting the best coverage at minimum cost for plant building and inventory. Adjacent tofermentors a separate house can be provided for pumps, compressors, molasses

weighing system etc.

STORE AND WAREHOUSES

The engineer must decide whether the warehouses must be at ground level or

dock level.

The latter facilitates loading trains and trucks, but costs 15-20% more than one

placed on the ground. It is usually difficult to justify the added expenses of a dock-high

warehouse.

To size the amount of space needed, it must be determined how much is to be

stored in what size containers. The container sizes that will be used are obtained from

the scope. Liquids are generally stored in bulk containers. No more than a weeks

supply of liquid stored in drums should be planned. Solids, on the other hand, arefrequently stored in smaller containers or in a pile on the ground.

COST ESTIMATION

ESTIMATION OF THE TOTAL CAPITAL INVESTMENT

The total capital investment I involves the following:

A. The fixed capital investment in the process area, IF.

B. The capital investment in the auxiliary services, IA.C. The capital investment as working capital, IW.

i.e., I = IF + IA + IW


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A. FIXED CAPITAL INVESTMENT IN THE PROCESS AREA, IF.

This is the investment in all processing equipment within the processing area.

Fixed capital investment in the process area, IF = Direct plant cost + Indirect

plant cost

The approximate delivered cost of major equipments used in the proposed P-

nitrochlorobenzene manufacturing plant are furnished below:

S.No. Equipment Units Cost in

lakhs/unit

Cost in lakhs

1 Crystallizer 1 350 350

2 Reactor 1 250 250

3 Condenser 1 308 308

5 Distillation column 1 420 420

6 Pump 4 0.5 2

7 Storage tank sealed 2 100 200

8 Miscellaneous 2600

TOTAL 4130 lakhs

Direct Cost Factor

S.No Items Direct cost factor

1 Delivered cost of major equipments 100

2 Equipment installation 15

3 Insulation 15

4 Instrumentation 15

5 Piping 75


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6 Land & building 30

7 Foundation 10

8 Electrical 15

9 Clean up 5

Total direct cost factor 280

Direct plant cost = (Delivered cost of major equipments)

(Total direct factor) / 100

Direct plant cost = (4130 x 280) / 100

= 11564 lakhs

Indirect Cost Factor

S.No. Item Indirect cost factor

1 Overhead contractor etc. 30

2 Engineering fee 13

3 Contingency 13

Total indirect cost factor 56

Indirect plant cost = (Direct plant cost)

(Total indirect cost factor)/ 100

= (115664 x 56) / 100

= 6475.84 lakhs

Fixed capital investment in the process area, IF = Direct plant cost + Indirect

plant cost

= 1156 + 6475.84

= 18039.84 lakh

B. THE CAPITAL INVESTMENT IN THE AUXILLARY SERVICES, IA.

Such items as steam generators, fuel stations and fire protection facilities are

commonly stationed outside the process area and serve the system under consideration.


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S.No. Items Auxiliary services cost factor

1 Auxiliary buildings 5

2 Water supply 23 Electric Main Sub station 1.5

4 Process waste system 1

5 Raw material storage 1

6 Fire protection system 0.7

7 Roads 0.5

8 Sanitary and waste disposal 0.2

9 Communication 0.2

10 Yard and fence lighting 0.2

Total 12.3Capital investment in the auxillary services = (Fixed capital investment in the

process area) (Auxiliary services cost factor) / 100

= (18039.84 x 12.3) / 100

= 2218.9 lakhs

Installed cost = Fixed capital investment in the process area + Capital

investment in the auxiliary services

= 18039.84 + 2218.9

= 20258.74 lakhs

C. THE CAPITAL INVESTMENT AS WORKING CAPITAL, IW.

This is the capital invested in the form of cash to meet day-to-day operational

expenses, inventories of raw materials and products. The working capital may be

assumed as 15% of the total capital investment made in the plant (I).

Capital investment as working capital, IW

= ((18039.84 + 2218.9) x 15) / 85

= (20258.74 x 15) / 85

= 3575.071 lakhs


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Total capital investment, I = IF+ IA+ IW

= 18039.84 + 2218.9+ 3575.07

= 23833.81 lakhs

ESTIMATION OF MANUFACTURING COST

The manufacturing cost may be divided into three items, as follows:

A. Cost Proportional to total investment

B. Cost proportional to production rate

C. Cost proportional to labour requirement

A. COST PROPORTIONAL TO TOTAL INVESTMENT

This includes the factors, which are independent of production rate and

proportional to the fixed investment such as

- Maintenance-labour and material- Property taxes- Insurance- Safety expenses- Protection, security and first aid- General services, laboratory, roads, etc.- Administrative services

For this purpose we shall charge 15% of the installed cost of the plant

= (Installed cost x 15) / 100

= (20258.74 x 15) / 100

= 3038.811 lakhs

B. COST PROPORTIONAL TO PRODUCTION RATE


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The factors proportional to production rate are

- Raw material costs- Utilities cost power, fuel, water. Steam, etc.- Maintenance cost- Chemical, warehouse, shipping expenses

Assuming that the cost proportional to production rate is nearly 60% of total

capital investment.

Cost proportional to production rate

= (Total capital investment x 60) / 100

= (23833.81 x 0.6)

= 14300.286 lakhs

C. COST PROPORTIONAL TO LABOUR REQUIREMENT

The cost proportional to labour requirement might amount to 10% of total

manufacturing cost.

Cost proportional to labour requirement

= (3038.811 + 14300.286)(0.1) / (0.9)

= 1926.566 lakhs

Therefore, manufacturing cost

= (3038.811 + 14300.286 + 1926.566)

= 19265.657 lakhs

SALES PRICE OF PRODUCT

Market price of Paranitrochlorobenzene = Rs.18/kg

Production rate =1.5x105TPA

Total sales income = 18x1.5x105 x1000

= 27000 lakhs


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PROFITABILITY ANALYSIS

A. DEPRECIATION

According to sinking fund method:

R = (V-VS) I / (1+ I)n

R = Uniform annual payments made at the end of each year

V = Installed cost of the plant

VS = Salvage value of the plant after n years

N = life period (assumed to be 15 years)I = Annual interest rate (taken as 15%)

R = (20258.74 x 0.15) / (1+0.15)15-1

= 425.779 lakhs

B. GROSS PROFIT

Gross profit = Total sales income - manufacturing cost

= 27000 19265.657= 7734.343 lakhs

C. NET PROFIT

It is defined as the annual return on the investment made after deducting

depreciation and taxes. Tax rate is assumed to be 40%.

Net profit = Gross profit-Depreciation-(Gross profit*Tax rate)= 7734.434-425.779-7734.434*0.4)

= 4214.8268 lakhs

D. ANNUAL RATE OF RETURN


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Rate of return = (100*Net profit/Installed cost)

= (100*4214.8268) / 20258.74 = 20.8%

E. PAYOUT PERIOD

Payout period = Depreciable fixed investment / ((profit)+(depreciation))

= 20258.74 / (4214.826 + 425.779)

= 4.365 years

PROCESS SAFETY

In recent years there has been an increased emphasis on process safety as aresult of number of serious accidents. This is due in part to the worldwide attention to

issues in the chemical industry brought on by several dramatic accidents involving gas

releases, major explosions and several environmental

Accidents: Public awareness of these and other accidents has provided a driving

force for industry to improve its safety record. Local and national governments are

taking a hard look at safety in the industry as a whole and the chemical industry in

particular. There has been an increasing amount of government regulations.

For many reasons, the public often associates chemical industry with

environmental and safety problems. It is vital for the future of the chemical industry

that process safety has a higher priority in the design and operation of chemical process

facilities.

Industrial accidents

An accident has been defined as an unplanned or unexpected event, whichcauses or is likely to cause an injury.

An accident occurs as a result of unsafe action or exposure to an unsafe

environment.


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Unsafe actions or unsafe mechanical or physical conditions exist only because

of faults of a particular person.

Faults of persons are inherited from the environment and reasons for the faultsare:

Improper attitude Lack of knowledge or skill Physical unsuitability Improper mechanical or physical environment

Accident prevention

From the foregoing, it will be seen that the occurrence of an injury is the

culmination of a series of events circumstances that invariably occur in a fused and

logical order.

Knowledge of the factors in the accident sequence guides and assists in

selecting the point of attack in prevention work. It permits simplification without

sacrifice of effectiveness. The most important point is that unsafe condition or actions

are the immediate cause of accidents. The supervisions and management can control

the action of employed persons and so prevent unsafe acts and also guard or remove

unsafe conditions, even though previous events or circumstances in the sequence are

unfavorable.

The four factors that converge to cause accidents are:

Personal factor Hazard factor Unsafe factor Proximate casual factor

The solution under the four factors would also lead to the steps. These are

planning and organizing to


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1. Prevent unsafe mechanical or physical conditions.2. Prevent unsafe action being committed.

Unsafe condition examples:

Operating without securing, warning etc. Operating or working at unsafe speed. Making safety devices inoperative. Using unsafe equipment. Unsafe loading, placing, mixing etc. Taking unsafe position or posture. Working on moving or dangerous equipment. Unsafe mechanical and physical conditions. Inadequately guarded. Unguarded. Defective condition ( rough, delayed etc ). Unsafe design or construction. Hazardous arrangement or process. Inadequate or improperly distributed ventilation. Unsafe dress or apparel. Unsafe method, process, planning etc.

The most important means of accident prevention are:

Engineering revision. Instruction. Persuasion. Personal adjustment. Discipline.


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Industrial ventilation and lighting

The main functions of ventilation in an industry are:

To prevent harmful concentration of aerosols. To maintain reasonable condition of comfort for operators at

workplace.

It maintains the body heat balance and to provide reasonableconditions of comfort.

Ventilation should aim at

Keeping the air temperature of the workroom low enough to enablebody heat to be dissipated by convection

Preventing excessive humidity so as to assist body heat loss byevaporation.

regulating the rate of air movement so that loss of body heat byconvection is facilitated.

The amount of ventilation generally depends on the following factors:

Size and type of room or building and its usage. Duration and type of occupants and their activities. heat gains from sun , hot manufacturing. Temperature conditions. The operators of the ventilating system.

Types of ventilation

1. Natural ventilation2. Mechanical ventilation


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Natural ventilation

Forces, which operate to induce natural ventilation in building, arc due to :

Pressure exerted by outside wind. The temperature differences of the air within and withoutthe building.

Mechanical ventilation

It is brought out by their one or both of the following two methods:

Ventilation through windows or other openings owing to thesuction created by the exhaust of air.

Positive ventilation by means of a fan or blower.

Personal protective devices

Protective devices are required by regulation; the employers are required to

provide it free of cost and also should be responsible to ensure its usage maintenance

and renewal. Once it is decided to use personal protective devices, we must select the

proper type of devices. Make sure that the employees use and maintain these correctly.

For selection of device, two criteria should be used:

1. The degree of protection.

2. The ease with which it may be used.

Protective devices are divided into two groups:

1. Respiratory devices

2. Non-respiratory devices


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Safety appliances

Helmets

Every employee inside the factory should always wear the safety helmet to

avoid head injuries. No worker will be allowed to enter any plant without a helmet.

Safety goggles

The goggles must be worn while entering the process areas. Special geoggles

must be worn for gas and grinding operations.


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Safety shoes

All the employees working inside a factory should wear safety shoes and

gumboots should be used while handling acids and alkalis.

Hand gloves

While operating any valve or equipment and also while executing any

maintenance work including electrical maintenance work, the employees should wear

appropriate type of safety gloves.

Dust mask

While working in a dusty atmosphere, the employees must wear dust masks to

prevent dust and fumes entering the sensitive respiratory organs, which can cause a lot

of irritation and in the long run painful and incurable diseases.

Plastic aprons

This along with the hood gives protection to the operation and maintenance

staff while handling dangerous acids and other hazardous chemicals particularly whenthere is possible leakage.

In spite of safety appliances, the companys medical center is equipped to meet

any emergency and any employee coming in contact with acids or any hazardous

chemicals must be treated at the medical center immediately.

Health and Safety Factors

The mononitrochlorobenzenes are toxic substances which may be absorbed

through the skin and lungs giving rise to methemoglobin. their toxicity is about the

same as or greater than that of nitrobenzene. The para isomer is less toxic than the

ortho isomer, and the maximum allowable concentration that has been adopted for p-

nitrochlorobenzene is 1mg/m3(0.1ppm). The mononitrochlorobenzenes are moderate

fire hazards when exposed to heat or flame.


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LIMITATIONS

This compound is a derivative of nitrobenzene and information regarding the

various processes available for the manufacture of p-nitrochlorobenzene was not

available.

Thus, the short comings and advantages of this process of manufacture of p-

nitrochlorobenzene has not been discussed.

CONCLUSION

Para nitro chlorobenzene is an important compound used in theprocess of manufacture of intermediate for azo and sulphur dyes and also

industrial chemicals.

This project has dealt with material balance and energy balancerequired for production of para nitro chlorobenzene.

Also, the design aspects, process instrumentation, project feasibilityand health and safety factors have been discussed.

APPENDIX -1

AICHE-

DIPPR

American Instiute of Chemical Engineers-Design Institute for Physical

Property Data

ASME Americal Society of Mechanical Engineers

BLEVE Boiling Liquid Expanding Vapor Explosion

CCPS Center for Chemical Process Safety

CONSEQ Consequence Analysis Computer Software (Technica, Inc.)

CPI Chemical Process Industry

FMEA Failure Modes and Effects Analysis

FN Frequency Number

FTA Fault Tree Analysis

HAZOP Hazard and operability

OSHA Organization Safety and Heath administration

PERD Process Equiment Reliability Data


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PHA Preliminary Hazard Analysis

P&ID Piping and Instrumention Diagram

ROD Average Rate of Death

ROF Average Rate of FailureSYREL Systems Relibility Service Data Base

TCPA Toxic Catastrophe prevention Act

THERP Technique of Human Error Rate prediction

TNT Trinitrotoluene

TLV Threshold Limit Values

TNO Netherlands Organization for Applied Scientific Reserarch

TXDS Toxicity Dispersion

UCL Upper confidece LimitUFL Upper FlammableLimt

UVCE Union Nations Industrial Development Organization

VSP Vent Sizing Package

appendix 2Glossary

Aerosol fraction : The fraction of liquid phase which, when flashed to the

atmosphere, remains suspended asan aerosol.

Atmospheric dispersion : the low momentum mixing of a gas or vapor with air

the mixing is the result of turbulent energy exchange, which is a function of wind

(mechanical eddy formation ) and atmospherc

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