DEPARTMENT OF CHEMICAL ENGINEERING

SAFETY IN CHEMICAL INDUSTRIES

Course Code: CLPE15
Number of Credits: 3

Lecture- 16
Dr. Kartikeya Shukla
Assistant Professor
Department of Chemical Engineering
NIT Trichy 1
 • TWA (time-weighted average) concentration
• TLV
– TLV-TWA
– TLV-STEL
– TLV-C

Department of Chemical Engineering Safety In Chemical Industries 2

 Industrial Hygiene: Evaluation
TLVs,

Department of Chemical Engineering Safety In Chemical Industries 3

 Threshold Limit Values

Department of Chemical Engineering Safety In Chemical Industries 4

 • If more than one chemical is present in the
workplace, one procedure is to assume that the
effects of the toxicants are additive.

• The mixture TLV-TWA can be computed from

Department of Chemical Engineering Safety In Chemical Industries 5

 Industrial Hygiene: Control

Department of Chemical Engineering Safety In Chemical Industries 6

 Ventilation
• Local Ventilation
• Dilution Ventilation

Department of Chemical Engineering Safety In Chemical Industries 7

• Introduction: Role of chemical engineer in process industries; Industrial
Hazards , Fire hazards and it’s prevention, Radiation hazards and control of
exposure to radiation, Mechanical hazards, Electrical hazards.
• Psychology, hygiene & other industrial hazards: Industrial psychology,
Industrial hygiene, Housekeeping, Industrial lighting and ventilation,
Industrial noise, Occupational diseases and prevention methods, Personal
protective equipments; Site selection and plant layout.
• Instrumentation and control for safe operation: Pressure, Temperature
and Level controllers; Risk Management and Hazard Analysis – Steps
in risk management, Risk analysis using HAZOP, FTA etc.
• Case studies pertaining to chemical industries: Bhopal gas tragedy, causes,
affects & lessons learnt, other cases; Economics of safety – Financial costs
to individual, family, organization and society.
• Process safety and process safety management, Legal framework for
industrial safety and environment in India- The Factories Act, The
Environmental (Protection) Act, The Workmen’s compensation Act, The
Employee State Insurance Act.
Department of Chemical Engineering Safety In Chemical Industries 8
 Assignment
(13 marks)
• Write a report (Handwritten) of 15 pages on the following accidents (the links are given below)
by correlating all the concepts learnt in this course.

• Hazard Identification, Technical aspects, Initiation, propagation, and termination, methods that
could have prevented, TLV values, ignition temp, etc.

• https://www.youtube.com/watch?v=VXZRx7sE1qc
• https://www.youtube.com/watch?v=Tflm9mttAAI&ab_channel=USCSB
• https://www.youtube.com/watch?v=UM0jtD_OWLU&ab_channel=VideoSpikes
• https://www.youtube.com/watch?v=BeaX0IRjyd8&t=1s&ab_channel=USCSB
• https://www.youtube.com/watch?v=C561PCq5E1g&t=195s&ab_channel=USCSB
• https://www.youtube.com/watch?v=goSEyGNfiPM&t=1s&ab_channel=USCSB
• https://www.youtube.com/watch?v=j4iv4HvrfSU&ab_channel=USCSB
• https://www.youtube.com/watch?v=J4wKjGHvs_4&ab_channel=USCSB
• https://www.youtube.com/watch?v=BfUrC2u_Nsc&ab_channel=USCSB
• https://www.youtube.com/watch?v=pbFzuS8Bdhw&ab_channel=USCSB
• https://www.youtube.com/watch?v=2Bn4Krb-HoI&ab_channel=USCSB
• https://www.youtube.com/watch?v=HZirRB32qzU&ab_channel=USCSB
• https://www.youtube.com/watch?v=ADK5doMk3-k&ab_channel=USCSB
• https://www.youtube.com/watch?v=h4ZgvD4FjJ8&ab_channel=USCSB
• https://www.youtube.com/watch?v=PqskpvPejeU&ab_channel=USCSB
• https://www.youtube.com/watch?v=d5N8hxhJD7E&ab_channel=USCSB

The last date of submission is 14-10-2024

9
• Compute the
concentration (in ppm) of
the saturated vapor with
air above a solution of
pure toluene. Compute
the concentration (in
ppm) of the equilibrium
vapor with air above a
solution of 50 mol %
toluene and benzene. The
temperature is 80°F and
the total pressure is 1 atm

Department of Chemical Engineering Safety In Chemical Industries 10

 • Benzene and toluene
form an ideal liquid
mixture. A mixture
composed of 50 mol %
benzene is used in a
chemical plant. The
temperature is 80°F, and
the pressure is 1 atm. a.
Determine the mixture
TLV.

• TLV Benz=0.5 ppm

• TLV Tol=20 ppm

Department of Chemical Engineering Safety In Chemical Industries 11

DEPARTMENT OF CHEMICAL ENGINEERING

SAFETY IN CHEMICAL INDUSTRIES

Course Code: CLPE15
Number of Credits: 3

Lecture- 21
Dr. Kartikeya Shukla
Assistant Professor
Department of Chemical Engineering
NIT Trichy 12
Department of Chemical Engineering Safety In Chemical Industries 13
 Initiating factors
• Incorrect charging and inadequate cooling are the most
important initiating factors for the runaway reactions followed
by unknown exotherm/decomposition, impurities and incorrect
agitation/mixing resulting in hotspots.
• Incorrect charging
• Inadequate cooling

Department of Chemical Engineering Safety In Chemical Industries 14

 • Unknown exotherm/decompostion: In the manufacture of
tetrachloro-ethane excess chlorine was reacted with acetylene
at 100°C in the presence of ferric chloride catalyst. On one
occasion, the temperature of the mix dropped to 60 °C and an
explosion ruptured the bursting disc and also cracked the
reactor. It was suggested that monochloroacetylene had
decomposed, initiating the explosion.

Department of Chemical Engineering Safety In Chemical Industries 15

 • Impurity exotherm: An initiating mix of ether, butyl chloride,
cyclohexane and butyl bromide for the preparation of a
Grignard reagent was added to a reactor containing
magnesium. Cyclohexane was added and immediately vapours
emerged from the condenser vent and the bursting disc
ruptured. The investigation revealed that the cyclohexane
transfer line was wet and the Grignard reagent had reacted
with the water to produce hydrogen and ethane.

Department of Chemical Engineering Safety In Chemical Industries 16

 • Incorrect agitation: Monoethanolamine was added slowly with
stirring to 98% H2SO4 which was maintained at 110°C in a
glass-lined reactor. The monoethanolamine and H2SO4 were
immiscible. When the reaction was complete the mix was
cooled and isopropyl alcohol was added to precipitate the
product. On the day of the incident, the reactor was charged
with H2SO4 and then there was a shift change. The oncoming
shift did not realize that the stirrer had not been switched on
and proceeded to add the monoethanolamine. When they
realised the temperature was not rising and switched on the
stirrer. The two liquids were mixed causing an instantaneous
chemical reaction and explosion.

Department of Chemical Engineering Safety In Chemical Industries 17

 Case studies
• T2 Laboratories, Florida

Department of Chemical Engineering Safety In Chemical Industries 18

 Phenol-formaldehyde reactions
• Phenol-formaldehyde reactions are common industrial processes.
• The reaction of phenol or substituted phenol with an aldehyde, such
as formaldehyde, in the presence of an acidic or basic catalyst is
used to prepare phenolic resins.
• Phenolic resins are used in adhesives, coatings, and molding
compounds.
• Typically, phenol-formaldehyde reactions are highly exothermic.
Once a reaction is initiated, heat generated by the reaction increases
the reaction rate generating more heat. Because the reaction rate is
typically an exponential function of temperature, the rate of heat
generation will accelerate. Without intervention, a thermal runaway
will occur, producing a large amount of heat in a very short time.

Department of Chemical Engineering Safety In Chemical Industries 19

 • Once the reaction begins to accelerate, the pressure of the
system will typically increase suddenly due to gas
production and/or the vigorous evaporation of liquid.
• If the reaction continues to accelerate, the pressure buildup
may reach and exceed the ultimate strength of the reactor
and cause it to explode.
• The heat of reaction is removed by the evaporation of water
or other liquid from the process, condensation of the liquid
in the overhead condensation system, and return of the
liquid to the reactor vessel.
• Emergency relief on the reactor is usually provided by
rupture disks.
• For safety reasons, slow continuous or stepwise addition of
formaldehyde is preferred.
Department of Chemical Engineering Safety In Chemical Industries 20
 Components of intrinsic safety
• The basic parameters that have to be considered for assessing the chemical reaction systems
are
• Thermodynamics
• Reaction energy
• Adiabatic temperature and pressure rise
• Kinetics
• Activation energy
• Reaction rate
• Rate of heat generation
• Rate of pressure rise
• Time to maximum rate
• Physical
• Heat capacity
• Thermal conductivity
• In addition to the above parameters the safe limits of temperature, feed rate and concentration
have to be defined as a function of operating conditions.

Department of Chemical Engineering Safety In Chemical Industries 21

 Reaction Hazard
• Analysis indicates that incidents occur due to:
• Lack of proper understanding of the thermo-
chemistry and chemistry
• Inadequate engineering design for heat transfer
– Inadequate control systems and safety back-up
systems Including venting arrangements
• Inadequate operational procedures, including
training

Department of Chemical Engineering Safety In Chemical Industries 22

 Assessing Reaction Hazard
• Controlling an exothermic reaction depends on the interaction
among: the kinetics and reaction chemistry
– the plant equipment design
– the operating environment.

• Chemical process industry must consider the following factors

to better understand and address the potential hazards and
consequences of reactive systems:

Department of Chemical Engineering Safety In Chemical Industries 23

 Characterization using
Calorimeters
• Important questions that must be asked for the characterization of
reactive chemicals:
• At what temperature does the reaction rate become large enough
• What is the maximum temperature increase
• What is the maximum pressure during the reaction.
• At what time and temperature does the maximum self-heat rate or
pressure rate occurs
• Are there any side reactions
• Can the heat generated by chemical reactions (desired or
undesired) exceed the capability of the vessel/process to remove
heat

Department of Chemical Engineering Safety In Chemical Industries 24

 Tools for evaluating thermal
explosion

– Thermal analysis Differential Scanning

Calorimeter (DSC),
– Thermo Gravimetric Analyzer (TGA),
– Differential Thermal Analyzer (DTA).

Department of Chemical Engineering Safety In Chemical Industries 25

Department of Chemical
Safety In Chemical Industries 26
Engineering
DEPARTMENT OF CHEMICAL ENGINEERING

SAFETY IN CHEMICAL INDUSTRIES

Course Code: CLPE15
Number of Credits: 3

Lecture- 16
Dr. Kartikeya Shukla
Assistant Professor
Department of Chemical Engineering
NIT Trichy 27
 Dose versus Response

Department of Chemical Engineering Safety In Chemical Industries 28

Department of Chemical
Safety In Chemical Industries 29
Engineering
Department of Chemical
Safety In Chemical Industries 30
Engineering
Department of Chemical
Safety In Chemical Industries 31
Engineering
Department of Chemical
Safety In Chemical Industries 32
Engineering
 Dose-response curve

Lethal dose curve

Department of Chemical
Safety In Chemical Industries 33
Engineering
• If the response of interest is death
or lethality, the response versus
log dose curve of Figure is called
a lethal dose curve

• Effective dose

Department of Chemical Engineering Safety In Chemical Industries 34

 Threshold Limit Values

Department of Chemical Engineering Safety In Chemical Industries 35

 Industrial Hygiene
Identification: determination of the presence
or possibility of workplace exposures.
Evaluation: determination of the magnitude of
the exposure.
Control: application of appropriate technology
to reduce workplace exposures to acceptable
levels.

Department of Chemical Engineering Safety In Chemical Industries 36

Department of Chemical
Safety In Chemical Industries 37
Engineering
 OSHA: Process Safety
Management
• The PSM standard has 14 major sections:
– employee participation,
– process safety information
– process hazard analysis
• a team of expert, HAZOP, what-if scenarios, checklist
– operating procedures
• initial startup, normal operations, temporary operations, emergency shutdown, emergency operations,
normal shutdown
– training
– contractors
– pre-startup safety review
– mechanical integrity
– hot work permits
– management of change
– incident investigations
– emergency planning and response
– audits
– trade secrets.

Department of Chemical Engineering Safety In Chemical Industries 38

 Industrial Hygiene: Identification
Industrial hygiene (particularly identification)
must be a part of the education process of
chemists, engineers, and managers.

Material Safety Data Sheets

Department of Chemical Engineering Safety In Chemical Industries 39

Department of Chemical Engineering Safety In Chemical Industries 40
Department of Chemical
Safety In Chemical Industries 41
Engineering
 Industrial Hygiene: Evaluation
TLVs,

Department of Chemical Engineering Safety In Chemical Industries 42

 • If more than one chemical is present in the
workplace, one procedure is to assume that the
effects of the toxicants are additive.

• The mixture TLV-TWA can be computed from

Department of Chemical Engineering Safety In Chemical Industries 43

 • Determine the 8-hr TWA worker exposure if
the worker is exposed to toluene vapors as
follows. TLV for toluene is 100 ppm, the
worker is?

Department of Chemical Engineering Safety In Chemical Industries 44

 Determine the mixture TLV at 25 ℃ and 1 atm
pressure of a mixture derived from the following
liquid:

Department of Chemical Engineering Safety In Chemical Industries 45

• A substance has a TLV-TWA of 200 ppm,
a TLV-STEL of 250 ppm, and a TLV-C of
300 ppm. The data in the following table
were taken in a work area

Department of Chemical Engineering Safety In Chemical Industries 46

 Industrial Hygiene: Control

Department of Chemical Engineering Safety In Chemical Industries 47

 Ventilation
• Local Ventilation
• Dilution Ventilation

Department of Chemical Engineering Safety In Chemical Industries 48

 Industrial Hygiene: Control

Department of Chemical Engineering Safety In Chemical Industries 49

• Introduction: Role of chemical engineer in process industries; Industrial Hazards ,
Fire hazards and it’s prevention, Radiation hazards and control of exposure to
radiation, Mechanical hazards, Electrical hazards, Construction hazards.
• Psychology, hygiene & other industrial hazards: Industrial psychology, Industrial
hygiene, Housekeeping, Industrial lighting and ventilation, Industrial noise,
Occupational diseases and prevention methods, Personal protective equipments;
Site selection and plant layout.
• Instrumentation and control for safe operation: Pressure, Temperature and
Level controllers; Risk Management and Hazard Analysis – Steps in risk
management, Risk analysis using HAZOP, FTA etc.
• Case studies pertaining to chemical industries: Bhopal gas tragedy, causes, affects
& lessons learnt, other cases; Economics of safety – Financial costs to individual,
family, organization and society.
• Process safety and process safety management, Legal framework for industrial
safety and environment in India- The Factories Act, The Environmental (Protection)
Act, The Workmen’s compensation Act, The Employee State Insurance Act.

Department of Chemical Engineering Safety In Chemical Industries 50

 Assignment
(13 marks)
• Write a report (Handwritten) of 15 pages on the following accidents (the links are given below)
by correlating all the concepts learnt in this course.

• Hazard Identification, Technical aspects, Initiation, propagation, and control, methods that could
have prevented, TLV values, ignition temp, etc.

• https://www.youtube.com/watch?v=VXZRx7sE1qc
• https://www.youtube.com/watch?v=Tflm9mttAAI&ab_channel=USCSB
• https://www.youtube.com/watch?v=UM0jtD_OWLU&ab_channel=VideoSpikes
• https://www.youtube.com/watch?v=BeaX0IRjyd8&t=1s&ab_channel=USCSB
• https://www.youtube.com/watch?v=C561PCq5E1g&t=195s&ab_channel=USCSB
• https://www.youtube.com/watch?v=goSEyGNfiPM&t=1s&ab_channel=USCSB
• https://www.youtube.com/watch?v=j4iv4HvrfSU&ab_channel=USCSB
• https://www.youtube.com/watch?v=J4wKjGHvs_4&ab_channel=USCSB
• https://www.youtube.com/watch?v=BfUrC2u_Nsc&ab_channel=USCSB
• https://www.youtube.com/watch?v=pbFzuS8Bdhw&ab_channel=USCSB
• https://www.youtube.com/watch?v=2Bn4Krb-HoI&ab_channel=USCSB
• https://www.youtube.com/watch?v=HZirRB32qzU&ab_channel=USCSB
• https://www.youtube.com/watch?v=ADK5doMk3-k&ab_channel=USCSB
• https://www.youtube.com/watch?v=h4ZgvD4FjJ8&ab_channel=USCSB
• https://www.youtube.com/watch?v=PqskpvPejeU&ab_channel=USCSB
• https://www.youtube.com/watch?v=d5N8hxhJD7E&ab_channel=USCSB

The last date of submission is 14-10-2024

51
DEPARTMENT OF CHEMICAL ENGINEERING

SAFETY IN CHEMICAL INDUSTRIES

Course Code: CLPE15
Number of Credits: 3

Lecture- 19
Dr. Kartikeya Shukla
Assistant Professor
Department of Chemical Engineering
NIT Trichy 52
 • Location

• Site selection

• Plant layout

• Unit plot planning

Department of Chemical Engineering Safety In Chemical Industries 53

 • Processing units
• Maintenance shop
• Ware house
• Safety house
• SRP
• R&D
• Pilot plants
• Admin block
• Waste water treatment
• Boiler
• Elevated flare
• R&D section
• Safety office
• Warehouse

Department of Chemical Engineering Safety In Chemical Industries 54

 • First degree Line of defense to prevent second
degree hazard. Engineering
– Direction of wind
– Providing adequate access ways
• Second line of defense
– Separating hazardous areas from areas occupied by
people
– Strategically locating fire fighting equipment.
• Third line of defense
– Hospital facilities

Department of Chemical Engineering Safety In Chemical Industries 55

 Tools and techniques of defense
• Natural tones
– Topography
– Direction of wind, adequate water
• Intelligence of man
– Separation
– Concentration of hazards and identification of
hazards
• Design and build physical facilities to combat
hazards.

Department of Chemical Engineering Safety In Chemical Industries 56

 Safety problems of site selection
• Toxic gases to residential area
• Flammable gases to ignition source
• Fog from cooling towers
• Two ways to combat these types
• Plant downwind from the community
• Waste stream
• High speed highways
• Community
• Adequate source of water
• Topography low land area for plant

Department of Chemical Engineering Safety In Chemical Industries 57

Department of Chemical Engineering Safety In Chemical Industries 58
 Safety problems of plant layout
• Processing units most hazardous areas.
• Processing units should be removed from boundaries.
• Should be consolidated rather than scattered.
• Processing units and ignition sources.
• Processing units should be downwind from ignition sources
• Processing units and tanks area.
• Not too consolidated. Mutually hazardous. One unit operation and one shut
down
• Spacing of process units, remains a matter of good judgment
– Operating temperature
– Operating pressure
– Types of materials
– Quantities of materials
– Space required for fire fighting
Department of Chemical Engineering Safety In Chemical Industries 59
 • Administrative facilities at the periphery and isolated
from hazardous components.
– Sales
– Largest concentration of people
• One adverse factor
• Laboratories adjacent to administrative facilities (no direct
contact)
• Safety office should be located on the periphery on the plant
• Boiler, maintenance shop ignition source, upwind location.
• Warehouse nearby maintenance shop
• Tank truck traffic, downwind area is preferred (peripheral
locations).

Department of Chemical Engineering Safety In Chemical Industries 60

 • Waste water facilities downwind.
• Cooling towers (toxics) downwind
location from roadways.
• Elevated flare or burning pot
upwind or downwind?
• Sidewind?
• Storage vessels downwind in tank
area consolidated.
– Separation of tanks from each
other
– Separation of tanks from other
facilities
– Area required to provide dikes
• Try out for a layout Road
connectivity
• Arrange heavily travelled roads
• Ground level pipe alleys.
• Overhead pipe alleys.
• Expansion loop
Department of Chemical Engineering Safety In Chemical Industries 61
Department of Chemical Engineering Safety In Chemical Industries 62
 • Pipe allies and road crossing overhead clearance
• Pipe allies and diked areas
• Power in wires
• Power lines below ground
• Safety locations remote from hazardous locations
but not enough
• General pattern for location of safety showers
• We may not get always the way we want.
• Flammable mixtures may not be uphill from point
of ignition
Department of Chemical Engineering Safety In Chemical Industries 63
 Safety considerations in unit plot
planning
• Construction and operation cost alongwith the
safety.
• Compact unit, cost and safety

Department of Chemical Engineering Safety In Chemical Industries 64

 • Accessways to both sides of considerable
portion of processing equipment, firefighting,
fire breaks
• Gantry crane
• Cooling tower header
• Depressed area firewalls

Department of Chemical Engineering Safety In Chemical Industries 65

Department of Chemical
Safety In Chemical Industries 66
Engineering
Department of Chemical
Safety In Chemical Industries 67
Engineering
 • A roadway
• A gantry way
• Cooling water header beneath the gantry way
• A line of fractionating towers, heat exchangers,
accumulators, reflux drums. Depressed about eight
inches.
• The main pipe alley of the unit. If the unit includes fan
type air coolers, they can also be mounted.
• A rows of pumps
• A roadway

Department of Chemical Engineering Safety In Chemical Industries 68

 • Roadways flanking fire fighting
• Gantry crane
• Area required for gantry way provides space
• Cooling water header water facility
• Depressed area will retain spills
• Removal of pump while unit is operating

Department of Chemical Engineering Safety In Chemical Industries 69

 • Control house
• Periphery best view of the unit
• Upwind location
• Furnace sideways
• Compressors reasonable separation
• Compressor leaks downwind.
• Reactors hot ignition source
• Electrical unit below ground
• Fire hydrants close to hazardous spots
• Indoors units
• No prevailing winds
• Distance would have solved the purpose of low cost containment
• Physical barrier
• Separate compartment ignition and flammables
• Two doors
• High temperature, high pressure isolated
• Fire resistant walls
Department of Chemical Engineering Safety In Chemical Industries 70
 • Building of multiple floors
• Flammable liquids should not be uphill of ignition sources
• Flammable vapors heavy or light
• Concentration of hazards:
– Ventilating systems
– High capacity drainage
– Remotely operated handling devices
• After that also limit size of hazards

Department of Chemical Engineering Safety In Chemical Industries 71

 Chemical Process safety
• There are many reasons for explosions during
chemical processing
– Decomposition and runaway chemical reactions
are the most common
– Often these are either exothermic and/or gas
producing reactions that go out of control
– Can be avoided if reactions are understood and
reactive chemicals are identified.

Department of Chemical Engineering Safety In Chemical Industries 72

DEPARTMENT OF CHEMICAL ENGINEERING

SAFETY IN CHEMICAL INDUSTRIES

Course Code: CLPE15
Number of Credits: 3

Lecture- 20
Dr. Kartikeya Shukla
Assistant Professor
Department of Chemical Engineering
NIT Trichy 73
 Safety problems of plant layout
• Processing units most hazardous areas.
• Processing units should be removed from boundaries.
• Should be consolidated rather than scattered.
• Processing units and ignition sources.
• Processing units should be downwind from ignition sources
• Processing units and tanks area.
• Not too consolidated. Mutually hazardous. One unit operation and one shut
down
• Spacing of process units, remains a matter of good judgment
– Operating temperature
– Operating pressure
– Types of materials
– Quantities of materials
– Space required for fire fighting
Department of Chemical Engineering Safety In Chemical Industries 74
 • Administrative facilities at the periphery and isolated
from hazardous components.
– Sales
– Largest concentration of people
• One adverse factor
• Laboratories adjacent to administrative facilities (no direct
contact)
• Safety office should be located on the periphery on the plant
• Boiler, maintenance shop ignition source, upwind location.
• Warehouse nearby maintenance shop
• Tank truck traffic, downwind area is preferred (peripheral
locations).

Department of Chemical Engineering Safety In Chemical Industries 75

 • Waste water facilities downwind.
• Cooling towers (toxics) downwind
location from roadways.
• Elevated flare or burning pot
upwind or downwind?
• Sidewind?
• Storage vessels downwind in tank
area consolidated.
– Separation of tanks from each
other
– Separation of tanks from other
facilities
– Area required to provide dikes
• Try out for a layout Road
connectivity
• Arrange heavily travelled roads
• Ground level pipe alleys.
• Overhead pipe alleys.
• Expansion loop
Department of Chemical Engineering Safety In Chemical Industries 76
Department of Chemical Engineering Safety In Chemical Industries 77
 • Pipe allies and road crossing overhead
clearance
• Pipe allies and diked areas
• Power in wires
• Power lines below ground
• Safety locations remote from hazardous
locations but not enough
• General pattern for location of safety showers
Department of Chemical Engineering Safety In Chemical Industries 78
 Safety considerations in unit plot
planning
• Construction and operation cost alongwith the
safety.
• Compact unit, cost and safety

Department of Chemical Engineering Safety In Chemical Industries 79

 • Accessways to both sides of considerable
portion of processing equipment, firefighting,
fire breaks
• Gantry crane
• Cooling tower header
• Depressed area firewalls

Department of Chemical Engineering Safety In Chemical Industries 80

 • Control house
• Periphery best view of the unit
• Upwind location
• Furnace sideways
• Compressors reasonable separation
• Compressor leaks downwind.
• Reactors hot ignition source
• Electrical unit below ground
• Fire hydrants close to hazardous spots
• Indoors units
• No prevailing winds
• Distance would have solved the purpose of low cost containment
• Physical barrier
• Separate compartment ignition and flammables
• Two doors
• High temperature, high pressure isolated
• Fire resistant walls
Department of Chemical Engineering Safety In Chemical Industries 81
 • Building of multiple floors
• Flammable liquids should not be uphill of ignition sources
• Flammable vapors heavy or light
• Concentration of hazards:
– Ventilating systems
– High capacity drainage
– Remotely operated handling devices
• After that also limit size of hazards

Department of Chemical Engineering Safety In Chemical Industries 82

 Chemical Process safety
• There are many reasons for explosions during
chemical processing
– Decomposition and runaway chemical reactions
are the most common
– Often these are either exothermic and/or gas
producing reactions that go out of control
– Can be avoided if reactions are understood and
reactive chemicals are identified.

Department of Chemical Engineering Safety In Chemical Industries 83

 Runaway Reaction
• In chemical engineering, runaway is a process by which an
exothermic reaction goes out of control, often resulting in an
explosion.
• Exothermic chemical reactions can lead to a thermal runaway if the
heat generation rate exceeds the heat removal rate.

• When the reaction rate increases due to an increase in temperature,

causing a further increase in temperature and hence a further
increase in the reaction rate.
• Thermal runaway may result from exothermic side reaction(s), and
is characterized by an exponential increase in the rate of heat
generation, temperature and pressure.

Department of Chemical Engineering Safety In Chemical Industries 84

 Thermal profile of exothermic
reaction

Department of Chemical Engineering Safety In Chemical Industries 85

Department of Chemical Engineering Safety In Chemical Industries 86
 Initiating factors
• Incorrect charging and inadequate cooling are the most
important initiating factors for the runaway reactions followed
by unknown exotherm/ decomposition, impurities and
incorrect agitation/mixing resulting in hotspots.
• Incorrect charging
• Inadequate cooling

Department of Chemical Engineering Safety In Chemical Industries 87

 • Unknown exotherm/decompostion: In the manufacture of
tetrachloro-ethane excess chlorine was reacted with acetylene
at 100°C in the presence of ferric chloride catalyst. On one
occasion, the temperature of the mix dropped to 60 °C and an
explosion ruptured the bursting disc and also cracked the
reactor. It was suggested that monochloroacetylene had
decomposed, initiating the explosion.

Department of Chemical Engineering Safety In Chemical Industries 88

 • Impurity exotherm: An initiating mix of ether, butyl chloride,
cyclohexane and butyl bromide for the preparation of a
Grignard reagent was added to a reactor containing
magnesium. Cyclohexane was added and immediately vapours
emerged from the condenser vent and the bursting disc
ruptured. The investigation revealed that the cyclohexane
transfer line was wet and the Grignard reagent had reacted
with the water to produce hydrogen and ethane.

Department of Chemical Engineering Safety In Chemical Industries 89

 • Incorrect agitation: Monoethanolamine was added slowly with
stirring to 98% H2SO4 which was maintained at 110°C in a
glass-lined reactor. The monoethanolamine and H2SO4 were
immiscible. When the reaction was complete the mix was
cooled and isopropyl alcohol was added to precipitate the
product. On the day of the incident, the reactor was charged
with H2SO4 and then there was a shift change. The oncoming
shift did not realize that the stirrer had not been switched on
and proceeded to add the monoethanolamine. When they
realised the temperature was not rising and switched on the
stirrer. The two liquids were mixed causing an instantaneous
chemical reaction and explosion.

Department of Chemical Engineering Safety In Chemical Industries 90

 Fault tree

Department of Chemical Engineering Safety In Chemical Industries 91

 Case studies
• T2 Laboratories, Florida

Department of Chemical Engineering Safety In Chemical Industries 92

 Phenol-formaldehyde reactions
• Phenol-formaldehyde reactions are common industrial processes.
• The reaction of phenol or substituted phenol with an aldehyde, such
as formaldehyde, in the presence of an acidic or basic catalyst is
used to prepare phenolic resins.
• Phenolic resins are used in adhesives, coatings, and molding
compounds.
• Typically, phenol-formaldehyde reactions are highly exothermic.
Once a reaction is initiated, heat generated by the reaction increases
the reaction rate generating more heat. Because the reaction rate is
typically an exponential function of temperature, the rate of heat
generation will accelerate. Without intervention, a thermal runaway
will occur, producing a large amount of heat in a very short time.

Department of Chemical Engineering Safety In Chemical Industries 93

 • Once the reaction begins to accelerate, the pressure of the
system will typically increase suddenly due to gas
production and/or the vigorous evaporation of liquid.
• If the reaction continues to accelerate, the pressure buildup
may reach and exceed the ultimate strength of the reactor
and cause it to explode.
• The heat of reaction is removed by the evaporation of water
or other liquid from the process, condensation of the liquid
in the overhead condensation system, and return of the
liquid to the reactor vessel.
• Emergency relief on the reactor is usually provided by
rupture disks.
• For safety reasons, slow continuous or stepwise addition of
formaldehyde is preferred.
Department of Chemical Engineering Safety In Chemical Industries 94
 Chemical Reactivity Hazard
• A chemical reactivity hazard is a situation with the potential
for an uncontrolled chemical reaction that can result directly
or indirectly in serious harm to people, property, or the
environment.
• The resulting reaction may be violent, releasing heat, large
quantities of toxic, or flammable gases or solids.
• If the reaction is confined in a container, the pressure within
the container may increase resulting in an explosion.
• Common materials that we use routinely by themselves with
negligible hazard may react violently when mixed with other
common materials, or react violently when the temperature or
pressure is changed.

Department of Chemical Engineering Safety In Chemical Industries 95

 Components of intrinsic safety
• The basic parameters that have to be considered for assessing the chemical reaction systems
are
• Thermodynamics
• Reaction energy
• Adiabatic temperature and pressure rise
• Kinetics
• Activation energy
• Reaction rate
• Rate of heat generation
• Rate of pressure rise
• Time to maximum rate
• Physical
• Heat capacity
• Thermal conductivity
• In addition to the above parameters the safe limits of temperature, feed rate and concentration
have to be defined as a function of operating conditions.

Department of Chemical Engineering Safety In Chemical Industries 96

 Reaction Hazard
• Analysis indicates that incidents occur due to:
• Lack of proper understanding of the thermo-
chemistry and chemistry
• Inadequate engineering design for heat transfer
– Inadequate control systems and safety back-up
systems Including venting arrangements
• Inadequate operational procedures, including
training

Department of Chemical Engineering Safety In Chemical Industries 97

 Assessing Reaction Hazard
• Controlling an exothermic reaction depends on the interaction
among: the kinetics and reaction chemistry
– the plant equipment design
– the operating environment.

• Chemical process industry must consider the following factors

to better understand and address the potential hazards and
consequences of reactive systems:

Department of Chemical Engineering Safety In Chemical Industries 98

 • Thorough hazard assessment: The chemical &
process hazards and the consequences of
deviations must be thoroughly understood,
evaluated, and appropriately addressed through
preventive measures. Several layers of safety
systems, whether complementary or redundant
should be considered to enhance reliability.

Department of Chemical Engineering Safety In Chemical Industries 99

 • Complete identification of reaction chemistry and thermochemistry:
• For some exothermic reactions, the time to runaway is very short.
• Over-pressurization can occur when gas or vapor is produced as a
byproduct of the reaction or any decomposition reactions.
• The kinetics of the runaway reaction will be reaction specific and
may differ in various runaway situations.
• The characteristics of the particular reactions must be determined
experimentally.
• Experimental data should be used to define process boundaries in
terms of the pressure, temperature, concentration, and other
parameters as well as the consequences of operating outside of these
boundaries.

Department of Chemical Engineering Safety In Chemical Industries 100

 • Addition of raw materials: Frequently, the
reaction rate is controlled by the addition rate
of one reactant or the catalyst and should be
determined based on chemistry studies.
Process industries must pay attention to the
order of ingredients, the addition rates, under-
or over-charging, and loss of agitation.

Department of Chemical Engineering Safety In Chemical Industries 101

 • Emergency relief: Runaway reactions may
lead to the rapid generation of gas or vapor.
Under certain conditions, the vapor generation
rate may be large enough to cause the vapor-
liquid mixture to swell to the top of the vessel,
resulting in two-phase flow in the relief
venting system. Relief system capacity should
be evaluated in conjunction with the hazard
analysis to ensure that sizing is based on an
appropriate worst case scenario.
Department of Chemical Engineering Safety In Chemical Industries 102
 • Administrative controls: If administrative
controls, such as training and standard
operating procedures (SOP), are used as a
safeguard against process deviation and
accidental release, consideration must be given
to human factors to ensure reliability

Department of Chemical Engineering Safety In Chemical Industries 103

 • Chemical plants produce products using a
variety of complex reactive chemistries.
• It is essential that the behavior of these
reactions be well characterized prior to using
these chemicals in large commercial reactors.
• Calorimeter analysis is important to
understand both the desired reactions and also
undesired reactions.

Department of Chemical Engineering Safety In Chemical Industries 104

 Characterization using
Calorimeters
• Important questions that must be asked for the characterization of
reactive chemicals:
• At what temperature does the reaction rate become large enough
• What is the maximum temperature increase
• What is the maximum pressure during the reaction.
• At what time and temperature does the maximum self-heat rate or
pressure rate occurs
• Are there any side reactions
• Can the heat generated by chemical reactions (desired or
undesired) exceed the capability of the vessel/process to remove
heat

Department of Chemical Engineering Safety In Chemical Industries 105

 Tools for evaluating thermal
explosion

– Thermal analysis Differential Scanning

Calorimeter (DSC),
– Thermo Gravimetric Analyzer (TGA),
– Differential Thermal Analyzer (DTA).

Department of Chemical Engineering Safety In Chemical Industries 106

 Steps to Reduce Reactive
Hazards
• Facilities should take the following steps to prevent
runaway reactions: Modify processes to improve inherent
safety.
• Minimize the potential for human error.
• Understand events that may lead to an overpressure and
eventually to vessel rupture.
• Use lessons learned.
• Evaluate Safe Operating Procedures.
• Evaluate the effectiveness of the emergency relief system.
• Evaluate employee training and oversight

Department of Chemical Engineering Safety In Chemical Industries 107

 • Through Inherent Safety
• Use a reaction pathway that uses less hazardous chemicals
• Use reaction pathway that is less energetic, slower or easier to control
• Use smaller inventories of reactive chemicals both in process and in
storage

• Reduce shipping of reactive chemicals – produce on site on demand.

• Design equipments or procedures to prevent an incident in the event of a
human error.
• Control reactor stoichiometry and charge mass so that in the event of a
runaway reaction the pressure rating of the vessel will not be exceeded.

Department of Chemical Engineering Safety In Chemical Industries 108

DEPARTMENT OF CHEMICAL ENGINEERING

SAFETY IN CHEMICAL INDUSTRIES

Course Code: CLPE15
Number of Credits: 3

Lecture- 13
Dr. Kartikeya Shukla
Assistant Professor
Department of Chemical Engineering
NIT Trichy 109
 Toxicology, and industrial
hygiene
Chemical engineers must be knowledgeable
about
the way toxicants enter biological organisms,
the way toxicants are eliminated from biological
organisms,
the effects of toxicants on biological organisms,
and
methods to prevent or reduce the entry of toxicants
into biological organisms.

Department of Chemical Engineering Safety In Chemical Industries 110

 “All substances are poisons; there is none
which is not a poison. The right dose
differentiates a poison and a remedy”.
Toxicology is more adequately defined as the
qualitative and quantitative study of the
adverse effects of toxicants on biological
organisms.
A toxicant can be a chemical or physical agent,
including dusts, fibers, noise, and radiation.

Department of Chemical Engineering Safety In Chemical Industries 111

 How Toxicants Enter Biological
Organisms
 Ingestion: through the mouth into the stomach,
 Inhalation: through the mouth or nose into the lungs,
 Injection: through cuts into the skin, dermal
 Absorption: through skin membrane.
 Injection, inhalation, and dermal absorption generally result
in the toxicant entering the bloodstream unaltered.
 Toxicants entering through ingestion are frequently
modified or excreted in bile.
 Toxicants that enter by injection and dermal absorption are
difficult to measure and quantify.
 Some toxicants are absorbed rapidly through the skin.
 Of the four routes of entry, the inhalation and dermal routes
are the most significant to industrial facilities
Department of Chemical Engineering Safety In Chemical Industries 112
Department of Chemical
Safety In Chemical Industries 113
Engineering
Department of Chemical
Safety In Chemical Industries 114
Engineering
Skin
 The skin plays important roles in both the dermal absorption and
injection routes of entry.
 Injection includes both entry by absorption through cuts and
mechanical injection with hypodermic needles.
 The skin is composed of an outer layer called the stratum corneum.
This layer consists of dead, dried cells that are resistant to
permeation by toxicants.
 The absorption properties of the skin vary as a function of location
and the degree of hydration. The presence of water increases the
skin hydration and results in increased permeability.
 Most chemicals are not absorbed readily by the skin. A few
chemicals, however, do show remarkable skin permeability. Phenol,
for example, requires only a small area of skin for the body to
absorb an adequate amount to result in death.

Department of Chemical Engineering Safety In Chemical Industries 115

 Respiratory System
 Respiratory system is to exchange oxygen and
carbon dioxide between the blood and the inhaled
air.
 1 minute a normal person at rest uses an estimated
250 ml of oxygen and expels approximately 200
ml of carbon dioxide
 Only a fraction of the total air within the lung is
exchanged with each breath.
 These demands increase significantly with
physical exertion.
Department of Chemical Engineering Safety In Chemical Industries 116
  Upper and the lower respiratory system
 The upper respiratory system is composed of the nose, sinuses, mouth, pharynx (section
between the mouth and esophagus), larynx .
 The lower respiratory system is composed of the lungs and its smaller structures, including
the bronchi and the alveoli.
 The alveoli are small blind air sacs where the gas exchange with the blood occurs.
 These alveoli contribute a total surface area of approximately 70 m 2
 Small capillaries found in the walls of the alveoli transport the blood; an estimated 100 ml of
blood is in the capillaries at any moment.
 The upper respiratory tract is responsible for filtering, heating, and humidifying the air.
 The upper and lower respiratory tracts respond differently to the presence of toxicants. The
upper respiratory tract is affected mostly by toxicants that are water soluble.
 These materials either react or dissolve in the mucus to form acids and bases.
 Toxicants in the lower respiratory tract affect the alveoli by physically blocking the transfer of
gases (as with insoluble dusts) or reacting with the wall of the alveoli to produce corrosive or
toxic substances.
 Phosgene gas, for example, reacts with the water on the alveoli wall to produce HCl and
carbon monoxide.

Department of Chemical Engineering Safety In Chemical Industries 117

 Upper respiratory toxicants include hydrogen
halides (hydrogen chloride, hydrogen
bromide), oxides (nitrogen oxides, sulfur
oxides, sodium oxide), and hydroxides
(ammonium hydroxide, sodium dusts, and
potassium hydroxides).

Department of Chemical Engineering Safety In Chemical Industries 118

 How Toxicants Are Eliminated from
Biological Organisms
 Excretion: through the kidneys, liver, lungs, or
other organs;
 detoxification: by changing the chemical into
something less harmful by biotransformation;
 storage: in the fatty tissue.
 In general, chemical compounds with molecular
weights greater than about 300 are excreted by the
liver into bile.
 Compounds with lower molecular weights enter
the bloodstream and are excreted by the kidneys.
Department of Chemical Engineering Safety In Chemical Industries 119
 The lungs are also a means for elimination of substances,
particularly those that are volatile.
 Other routes of excretion are the skin (by means of
sweat).
 The liver is the dominant organ in the detoxification
process.
 The final mechanism for elimination is storage.
 Storage can create a future problem if the organism's
food supply is reduced and the fatty deposits are
metabolized; the stored chemical agents will be released
into the bloodstream, resulting in possible damage.
 For massive exposures to chemical agents, damage can
occur to the kidneys, liver, or lungs, significantly
reducing the organism's ability to excrete the substance.
Department of Chemical Engineering Safety In Chemical Industries 120
 Toxicological Studies
• A major objective of a toxicological study is to quantify the effects
of the suspect toxicant on a target organism.
• Before undertaking a toxicological study, the following items must
be identified:
• the toxicant
• the target or test organism
• the effect or response to be monitored
• the dose range
• the period of the test.
• The toxicant must be identified with respect to its chemical
composition and its physical state. For example, benzene can exist
in either liquid or vapor form.
• The dose units depend on the method of delivery.

Department of Chemical Engineering Safety In Chemical Industries 121

• The dose is measured in milligrams of agent per
kilogram of body weight.
• For gaseous airborne substances the dose is
measured in either parts per million (ppm) or
milligrams of agent per cubic meter of air
(mg/m3).
• Acute toxicity is the effect of a single exposure or
a series of exposures close together in a short
period of time.
• Chronic toxicity is the effect of multiple
exposures occurring over a long period of time.
Department of Chemical Engineering Safety In Chemical Industries 122
• A liquid mixture containing 0.50
mole fraction benzene-toluene is
contained in a storage vessel at
25°C and 1 atm. The vessel is
vented to the atmosphere.
• a. Is the vapor in the vessel
flammable?
• b. What are your resulting
concerns about fire and explosion
hazards with this storage vessel?
• Benzene-toluene can be assumed
to be an ideal liquid-vapor system.

Department of Chemical Engineering Safety In Chemical Industries 123

 Dose versus Response

Department of Chemical Engineering Safety In Chemical Industries 124

Department of Chemical
Safety In Chemical Industries 125
Engineering
Department of Chemical
Safety In Chemical Industries 126
Engineering
Department of Chemical
Safety In Chemical Industries 127
Engineering
Department of Chemical
Safety In Chemical Industries 128
Engineering
 Dose-response curve

Department of Chemical
Safety In Chemical Industries 129
Engineering
• If the response of interest is death
or lethality, the response versus
log dose curve of Figure is called
a lethal dose curve

• Effective dose

Department of Chemical Engineering Safety In Chemical Industries 130

 Threshold Limit Values

Department of Chemical Engineering Safety In Chemical Industries 131

 Industrial Hygiene
Identification: determination of the presence
or possibility of workplace exposures.
Evaluation: determination of the magnitude of
the exposure.
Control: application of appropriate technology
to reduce workplace exposures to acceptable
levels.

Department of Chemical Engineering Safety In Chemical Industries 132

 OSHA: Process Safety
Management
• The PSM standard has 14 major sections: employee participation,
– process safety information
– process hazard analysis
– operating procedures
– training, contractors
– pre-startup safety review
– mechanical integrit
– hot work permits
– management of change
– incident investigations
– emergency planning and response
– audits
– trade secrets.

Department of Chemical Engineering Safety In Chemical Industries 133

 Industrial Hygiene: Identification
Industrial hygiene (particularly identification)
must be a part of the education process of
chemists, engineers, and managers.

Material Safety Data Sheets

Department of Chemical Engineering Safety In Chemical Industries 134

Department of Chemical Engineering Safety In Chemical Industries 135
Department of Chemical
Safety In Chemical Industries 136
Engineering
 Industrial Hygiene: Evaluation
TLVs, PELs,

Department of Chemical Engineering Safety In Chemical Industries 137

 Industrial Hygiene: Control

Department of Chemical Engineering Safety In Chemical Industries 138

DEPARTMENT OF CHEMICAL ENGINEERING

SAFETY IN CHEMICAL INDUSTRIES

Course Code: CLPE15
Number of Credits: 3

Lecture- 12
Dr. Kartikeya Shukla
Assistant Professor
Department of Chemical Engineering
NIT Trichy 139
 Radiation measurements
• Curie (Ci), Becquerel (Bq)
• 1 Curie=3.7×1010 nuclear disintegrations per second.
• Many laboratories perform less than 1mCi.
• Radiation depends on type, quantity, type and amount of
interaction with matter.
• The roentgen is a unit of measurement for the exposure of X-
rays and gamma rays, and is defined as the electric charge
freed by such radiation in a specified volume of air divided by
the mass of that air (coulomb per kilogram).
• 1 Roentgen=0.000258 coulomb/kg

Department of Chemical Engineering Safety In Chemical Industries 140

 • The radiation dose absorbed by a person (that is, the amount of
energy deposited in human tissue by radiation) is measured using
the conventional unit rad or the SI unit gray (Gy).

• The biological risk of exposure to radiation is measured using the

conventional unit rem or the SI unit sievert (Sv).

• When a person is exposed to radiation, energy is deposited in the

tissues of the body.

• The amount of energy deposited per unit of weight of human tissue

is called the absorbed dose.

• The rad, which stands for radiation absorbed dose

Department of Chemical Engineering Safety In Chemical Industries 141

 • To determine a person’s biological risk, scientists have
assigned a number to each type of ionizing radiation (alpha
and beta particles, gamma rays, and x-rays) depending on that
type’s ability to transfer energy to the cells of the body.
• This number is known as the Quality Factor (Q).
• When a person is exposed to radiation, scientists can multiply
the dose in rad by the quality factor for the type of radiation
present and estimate a person’s biological risk in rems. Thus,
risk in rem = rad × Q.
• The rem has been replaced by the Sv.
• One Sv is equal to 100 rem.

Department of Chemical Engineering Safety In Chemical Industries 142

 Grieger Mueller Counter
• Countmeter
• Count rate meter

• Thin walled tube reacts with radiation to produce electronic

pulses that are amplified so that they can be heard through
speakers or earphones.

• Can pinpoint the radiation .

• Cannot determine their energies.

Department of Chemical Engineering Safety In Chemical Industries 143

Department of Chemical Engineering Safety In Chemical Industries 144
 Scintillation counters
• Atom excited to higher electronic state.
• Loses energy and return to its lowest state by emitting photons.
• For some substance the energy is lost by collisions.
• For some substances, energy is not degraded and light is
emitted under irradiation.
• Inorganic media such as ZnS, organic substances serve as
scintillating media and burst of light is detected, and amplified.
• ZnS

Department of Chemical Engineering Safety In Chemical Industries 145

 Alpha detectors
• Except scintillating counters, others will not work for alpha.

• Very Thin plastic covered window permits alpha particle to

enter electric field.

• Electronic pulse amplified and indicated by meter.

Department of Chemical Engineering Safety In Chemical Industries 146

 Control of exposure to radiation
• No unnecessary exposure should be permitted.
• Risk of the exposure should be balanced against
importance of results to be obtained.
• Strong source require meticulous care
• Preplanning of a facility, careful selection and use of
equipment, SOP, adequate education and training of
personnel.
• Every operation involving ionizing radiation should be
preplanned, if possible, rehearsed
– Time
– Distance
– Shielding

Department of Chemical Engineering Safety In Chemical Industries 147

 Time
• Exposure dose=rate×time
• Preplanned

• Distance:
• Radiation follows inverse square law (light
intensity)
• If radiation flux is 1 at a given distance, it will be
¼ at twice distance
– Mirrors, telescope.

Department of Chemical Engineering Safety In Chemical Industries 148

 Shielding or filters
• Any matter or mass placed between a radiation source
or beam and point of exposure will screen or decrease
the exposure
• Even air has some shielding effect.
• Lead or other heavy metals excellent shields for
radiation, but cost is high
• Concrete mixed with iron ore, heavy mineral is
effective
• Frequently used approach is locate the machine, source
in a pit or depression underground
• Deep pools of water.

Department of Chemical Engineering Safety In Chemical Industries 149

 Toxicology, and industrial
hygiene
Chemical engineers must be knowledgeable
about
the way toxicants enter biological organisms,
the way toxicants are eliminated from biological
organisms,
the effects of toxicants on biological organisms,
and
methods to prevent or reduce the entry of toxicants
into biological organisms.

Department of Chemical Engineering Safety In Chemical Industries 150

 Paracelsus: “All substances are poisons; there
is none which is not a poison. The right dose
differentiates a poison and a remedy”.
Toxicology is more adequately defined as the
qualitative and quantitative study of the
adverse effects of toxicants on biological
organisms.
A toxicant can be a chemical or physical agent,
including dusts, fibers, noise, and radiation.

Department of Chemical Engineering Safety In Chemical Industries 151

 How Toxicants Enter Biological
Organisms
 Ingestion: through the mouth into the stomach,
 Inhalation: through the mouth or nose into the lungs,
 Injection: through cuts into the skin, dermal
 Absorption: through skin membrane.
 Injection, inhalation, and dermal absorption generally result
in the toxicant entering the bloodstream unaltered.
 Toxicants entering through ingestion are frequently
modified or excreted in bile.
 Toxicants that enter by injection and dermal absorption are
difficult to measure and quantify.
 Some toxicants are absorbed rapidly through the skin.
 Of the four routes of entry, the inhalation and dermal routes
are the most significant to industrial facilities
Department of Chemical Engineering Safety In Chemical Industries 152
Department of Chemical
Safety In Chemical Industries 153
Engineering
Department of Chemical
Safety In Chemical Industries 154
Engineering
 Gastrointestinal Tract
Skin
 The skin plays important roles in both the dermal absorption and
injection routes of entry. Injection includes both entry by absorption
through cuts and mechanical injection with hypodermic needles.
 The skin is composed of an outer layer called the stratum corneum.
This layer consists of dead, dried cells that are resistant to
permeation by toxicants.
 The absorption properties of the skin vary as a function of location
and the degree of hydration. The presence of water increases the
skin hydration and results in increased permeability.
 Most chemicals are not absorbed readily by the skin. A few
chemicals, however, do show remarkable skin permeability. Phenol,
for example, requires only a small area of skin for the body to
absorb an adequate amount to result in death.

Department of Chemical Engineering Safety In Chemical Industries 155

 Respiratory System
 Respiratory system is to exchange oxygen and
carbon dioxide between the blood and the inhaled
air.
 1 minute a normal person at rest uses an estimated
250 ml of oxygen and expels approximately 200
ml of carbon dioxide
 Only a fraction of the total air within the lung is
exchanged with each breath.
 These demands increase significantly with
physical exertion.
Department of Chemical Engineering Safety In Chemical Industries 156
  Upper and the lower respiratory system
 The upper respiratory system is composed of the nose, sinuses, mouth, pharynx (section
between the mouth and esophagus), larynx .
 The lower respiratory system is composed of the lungs and its smaller structures, including
the bronchi and the alveoli.
 The alveoli are small blind air sacs where the gas exchange with the blood occurs.
 These alveoli contribute a total surface area of approximately 70 m 2
 Small capillaries found in the walls of the alveoli transport the blood; an estimated 100 ml of
blood is in the capillaries at any moment.
 The upper respiratory tract is responsible for filtering, heating, and humidifying the air.
 The upper and lower respiratory tracts respond differently to the presence of toxicants. The
upper respiratory tract is affected mostly by toxicants that are water soluble.
 These materials either react or dissolve in the mucus to form acids and bases.
 Toxicants in the lower respiratory tract affect the alveoli by physically blocking the transfer of
gases (as with insoluble dusts) or reacting with the wall of the alveoli to produce corrosive or
toxic substances.
 Phosgene gas, for example, reacts with the water on the alveoli wall to produce HCl and
carbon monoxide.

Department of Chemical Engineering Safety In Chemical Industries 157

 Upper respiratory toxicants include hydrogen
halides (hydrogen chloride, hydrogen
bromide), oxides (nitrogen oxides, sulfur
oxides, sodium oxide), and hydroxides
(ammonium hydroxide, sodium dusts, and
potassium hydroxides).

Department of Chemical Engineering Safety In Chemical Industries 158

 How Toxicants Are Eliminated from
Biological Organisms
 Excretion: through the kidneys, liver, lungs, or
other organs;
 detoxification: by changing the chemical into
something less harmful by biotransformation;
 storage: in the fatty tissue.
 In general, chemical compounds with molecular
weights greater than about 300 are excreted by the
liver into bile.
 Compounds with lower molecular weights enter
the bloodstream and are excreted by the kidneys.
Department of Chemical Engineering Safety In Chemical Industries 159
 The lungs are also a means for elimination of substances,
particularly those that are volatile.
 Other routes of excretion are the skin (by means of
sweat).
 The liver is the dominant organ in the detoxification
process.
 The final mechanism for elimination is storage.
 Storage can create a future problem if the organism's
food supply is reduced and the fatty deposits are
metabolized; the stored chemical agents will be released
into the bloodstream, resulting in possible damage.
 For massive exposures to chemical agents, damage can
occur to the kidneys, liver, or lungs, significantly
reducing the organism's ability to excrete the substance.
Department of Chemical Engineering Safety In Chemical Industries 160
 Toxicological Studies
• A major objective of a toxicological study is to quantify the effects
of the suspect toxicant on a target organism.
• Before undertaking a toxicological study, the following items must
be identified:
• the toxicant
• the target or test organism
• the effect or response to be monitored
• the dose range
• the period of the test.
• The toxicant must be identified with respect to its chemical
composition and its physical state. For example, benzene can exist
in either liquid or vapor form.
• The dose units depend on the method of delivery.

Department of Chemical Engineering Safety In Chemical Industries 161

• The dose is measured in milligrams of agent per
kilogram of body weight.
• For gaseous airborne substances the dose is
measured in either parts per million (ppm) or
milligrams of agent per cubic meter of air
(mg/m3).
• Acute toxicity is the effect of a single exposure or
a series of exposures close together in a short
period of time.
• Chronic toxicity is the effect of multiple
exposures occurring over a long period of time.
Department of Chemical Engineering Safety In Chemical Industries 162
 • Estimate the flash point of a solution of 50
mol % water and 50 mol % ethanol. Flash
point of pure ethanol 13 ℃.

Department of Chemical Engineering Safety In Chemical Industries 163

 • Why do staged hydrogen compressors need
interstage coolers?

Department of Chemical Engineering Safety In Chemical Industries 164

• A liquid mixture containing 0.50
mole fraction benzene-toluene is
contained in a storage vessel at
25°C and 1 atm. The vessel is
vented to the atmosphere.
• a. Is the vapor in the vessel
flammable?
• b. What are your resulting
concerns about fire and explosion
hazards with this storage vessel?
• Benzene-toluene can be assumed
to be an ideal liquid-vapor system.

Department of Chemical Engineering Safety In Chemical Industries 165

 Dose versus Response

Department of Chemical Engineering Safety In Chemical Industries 166

Department of Chemical
Safety In Chemical Industries 167
Engineering
Department of Chemical
Safety In Chemical Industries 168
Engineering
 • If the response of interest is death or lethality,
the response versus log dose curve of Figure 2-
7 is called a lethal dose curve

Department of Chemical Engineering Safety In Chemical Industries 169

DEPARTMENT OF CHEMICAL ENGINEERING

SAFETY IN CHEMICAL INDUSTRIES

Course Code: CLPE15
Number of Credits: 3

Lecture- 11
Dr. Kartikeya Shukla
Assistant Professor
Department of Chemical Engineering
NIT Trichy 170
 • Determine the LOC of a mixture of 2%
hexane, 3% propane, and 2% methane by
volume. LFLmethane 5%, LFLpropane 2.1%, LFLhexane
1.2%.

Department of Chemical Engineering Safety In Chemical Industries 171

 Radiations hazards and its
control
• Radiation refers to the process of emission, transmission,
reflection or absorption of energy.
• Electromagnetic.
• Electromagnetic radiation is special type doesn’t requires
medium.
– Ionizing : X-rays, γ rays, β particle, α particle
• Very high dose can cause death
• Moderate dose can cause tumor
– Non ionizing: UV rays, visible light, Radiowaves,
Television waves
• High exposure can heat up body tissues

Department of Chemical Engineering Safety In Chemical Industries 172

 • Ionizing radiation:
– Nuclear
– Electronic: Cathode ray tube, electron guns

• Radioactive isotopes and stable isotopes.

• Radioactive isotopes tend to stabilize after giving off radiations.
• Half life
• 2He
4

• Alpha particle:
– Little penetration due to large size
– Not potential hazard if not ingested
– Helps in cancer treatment
– smoke detectors

Department of Chemical Engineering Safety In Chemical Industries 173

 • β particle
– (-)vely charged particle, or positron
– can penetrate deeper than alpha
– Cathode rays
– Electron accelerators
– Glass, plastic, aluminium, used for shielding purpose
– For low energy, iron, copper, are used

Department of Chemical Engineering Safety In Chemical Industries 174

 X-rays, γ rays
• Electromagnetic radiations analogous to light but short
wavelength
– Shortwave radiation contains higher amounts of energy
and longwave radiation contains a smaller amount of
energy.
– Therefore, the sun gives off shortwave radiation, as it is
extremely hot and has a lot of energy to give.

• Emitted from nuclei, electron transfer

• X-rays are called Roentgen rays
• X-rays are used in clinical purpose.
• γ rays can be followed by alpha or beta decay.
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Department of Chemical Engineering Safety In Chemical Industries 176
 • Neutrons
• Not emitted spontaneously from radioactive nuclei
• Release depends on the interaction of α particle, γ particles
with nuclei of target materials
• Neutrons are neutral hence very high penetrating power.
• Too many protons in nucleus leads to emit positron.
• Too much energy in nucleus leads to emit γ rays.
• Too much mass in nucleus leads to emit alpha particle.

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 Radiation measurements
• Curie (Ci), Becquerel (Bq)
• 1 Curie=3.7×1010 nuclear disintegrations per second.
• Many laboratories perform less than 1mCi.
• Radiation depends on type, quantity, type and amount of
interaction with matter.
• The roentgen is a unit of measurement for the exposure of X-
rays and gamma rays, and is defined as the electric charge
freed by such radiation in a specified volume of air divided by
the mass of that air (coulomb per kilogram).
• 1 Roentgen=0.000258 coulomb/kg

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 • The radiation dose absorbed by a person (that is, the amount of
energy deposited in human tissue by radiation) is measured using
the conventional unit rad or the SI unit gray (Gy).

• The biological risk of exposure to radiation is measured using the

conventional unit rem or the SI unit sievert (Sv).

• When a person is exposed to radiation, energy is deposited in the

tissues of the body.

• The amount of energy deposited per unit of weight of human tissue

is called the absorbed dose.

• The rad, which stands for radiation absorbed dose

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 • To determine a person’s biological risk, scientists have
assigned a number to each type of ionizing radiation (alpha
and beta particles, gamma rays, and x-rays) depending on that
type’s ability to transfer energy to the cells of the body.
• This number is known as the Quality Factor (Q).
• When a person is exposed to radiation, scientists can multiply
the dose in rad by the quality factor for the type of radiation
present and estimate a person’s biological risk in rems. Thus,
risk in rem = rad × Q.
• The rem has been replaced by the Sv.
• One Sv is equal to 100 rem.

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 Measuring radiation
• To maintain a cumulative record.

• To measure over short period the exposure of individual

carrying out a specific operations.

• To survey flux or radiation level in all parts of the facility.

• To monitor contamination of hands, feets, hair, skin.

• To establish legal protection for employers and employees.

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 Radiation instrumentation
• Film badges
• Photographic film
• Low cost, convenient size, capability of integrating dose for a
long time
• X-rays, β rays, γrays, neutron radiations.
• Don’t respond to α rays.
• Holder with small disks of different metal pieces.
• If neutrons are involved, additional film of Cd should be taken.
• 7-10 days and returned to the service supplier.
• Emergency processing should also be done.
• Filters, absorption leads to determine level of exposure.
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Department of Chemical Engineering Safety In Chemical Industries 183
 Ionization chamber
• Provides a method of measurement based on the movement of
ions from one part of chamber to electric plate.
• Ions in a gas are reactive and may be chemically changed
while moving towards electrode.
• Total charge is not altered.
• Personal monitoring pocket ionization chamber like fountain
pen.
– Initially pen is charged to a known voltage.
– Change in the capacitance can be noted down.

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Department of Chemical Engineering Safety In Chemical Industries 185
 Grieger Mueller Counter
• Countmeter
• Count rate meter

• Thin walled tube reacts with radiation to produce electronic

pulses that are amplified so that they can be heard through
speakers or earphones.

• Can pinpoint the radiation .

• Cannot determine their energies.

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Department of Chemical Engineering Safety In Chemical Industries 187
 Scintillation counters
• Atom excited to higher electronic state.
• Loses energy and return to its lowest state by emitting photons.
• For some substance the energy is lost by collisions.
• For some substances, energy is not degraded and light is
emitted under irradiation.
• Inorganic media such as ZnS, organic substances serve as
scintillating media and burst of light is detected, and amplified.
• ZnS

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 Alpha detectors
• Except scintillating counters, others will not work for alpha.

• Very Thin plastic covered window permits alpha particle to

enter electric field.

• Electronic pulse amplified and indicated by meter.

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 Exposure to radiations
• Biological effects of radiation
– Genetic and cellular damage
• Terrestrial sources include uranium, actium,
thorium.
• Radon contribute largest to radioactivity to
natural background

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 • Body can repair damage from radiation upto a
level.
• At what point?
– Depends upon the ionization
– Direct
– Indirect
• Effects may be reversible or irreversible.

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 Decreasing order of sensitivity to
radiation
• Lymphocytes
• Granulocytes
• Basal cells
• Alveolar cells
• Bile ducts cells
• Cells or tubules of the kidneys
• Endothelial cells
• Connective tissue cells
• Muscle cells
• Bone cell
• Nerve cell

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 • Internal radiation exposure
• Certain isotopes tend to concentrate in most
vital organs.

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 Control of exposure to radiation
• No unnecessary exposure should be permitted.
• Risk of the exposure should be balanced against
importance of results to be obtained.
• Strong source require meticulous care
• Preplanning of a facility, careful selection and use of
equipment, SOP, adequate education and training of
personnel.
• Every operation involving ionizing radiation should be
preplanned, if possible, rehearsed
– Time
– Distance
– Shielding

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 Time
• Exposure dose=rate×time
• Preplanned

• Distance:
• Radiation follows inverse square law (light
intensity)
• If radiation flux is 1 at a given distance, it will be
¼ at twice distance
– Mirrors, telescope.

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 Shielding or filters
• Any matter or mass placed between a radiation source
or beam and point of exposure will screen or decrease
the exposure
• Even air has some shielding effect.
• Lead or other heavy metals excellent shields for
radiation, but cost is high
• Concrete mixed with iron ore, heavy mineral is
effective
• Frequently used approach is locate the machine, source
in a pit or depression underground
• Deep pools of water, if water doesn’t adversely affected
by water.
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