Safety in Chemical Industry

1. Unit 1: Introduction
Chemical Process Classification
Mrs.R.P.Nimbalkar
Assistant Professor,
Chemical Engineering,
PIET,Nagpur

2. 2
Safety In Chemical Processes
Conventional
Process
Hazards Process
Non-explosive Explosive
Non-flammable
reaction or operations
Flammable reaction or
Process Operations.

3. 3
Chemical Process Classification
The chemicals and their processes are classified
as
1)Hazardous Process : based on flash point
ignition temperature, but this is not sufficient.
It should have explosive range , concentration of
material , nature of material , sources of ignition ,
compression sensitivity , thermal stability ,
energy of activation , free energy etc:

4. 4
Types of Hazards
General process hazards:- Process
which represents conditions which
may increases the magnitude and
severity of an incidents.
Special process hazards:- which
increases the probability of fire or
explosion.

5. 5
Processes on the basis of rating
Rate Symptoms
A Highly flammable develop high pressure
instantly ,detonates or is explosive.
B Flammable or involves rapid generation of gases which
can form explosive mixture with Oxygen.
C Flammable or invovles the generation of highly
poisonous substances.
D Slightly flammable or generate mild toxic substances.
E Non-flammaatingble and non-gener

6. 6
On the basis of Degree of Hazard
Mild
Light
Moderate
Intermediate
Heavy
Severe

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Potentially Dangerous Process
 Involving explosive reaction or detonation.
 Sensitive to water or common contaminants.
 Sensitive to heating or undergoing spontaneous
polymerization.
 Processes involving highly exothermic reaction and
heat transfer rate is a limiting parameter.
 Processes involving unstable components.
 Processes operating in explosive range of materials.
 Processes involving toxic materials.
 Process having dust or mist explosion hazard.
 Processes handling flammable materials at high
temperature and high pressure.
 Processes handling huge quantity of materials at high
pressure.

8. 8
Selection of process
 Should be based on the comparison of alternative routes of
safety vs. economic advantage.
 Safety route should be economic , should be a good
investment.
 Selection of safety route should be based on correct and
sufficient data as well as experience.
 The inventory of the material should be low.
 Can introduce new techniques for hazardous process.

9. 9
Hazardous process
Ex: Manufacture of acetonitrile
•Ammoxidation of propylene.
•Cooling coils for temperature control.
•Bismuth molybdenum catalyst.
•To avoid hazard process to be carried out in
vapour phase.(So inventory of material is
low)
Properties of
Hydrocyanic acid
Properties of
Acetonitrile
 Toxic
Low boiling point
Tendency to
polymerize
Highly carcinogenic

10. 10
Precautions while Manufacture of
acetonitrile
 Ratio of ammonia-air is fixed so that the exit stream from
the reactor contains oxygen much below the explosion
limit of ammonia and oxygen.
 Propylene is introduced in the reactor, if when Oxygen
content are below 7%.
 In case of loss of ammonia or propylene feeds, tripping
of air compressor is done(this is costly)
 Flare system is provided since raw material and products
are flammable.
 HCN rich gases sent to incinerator(if fails then diverted to
flare system)
 HCN is water soluble and thus provided with water
deluge system.

11. 11
Contd….
Water deluge System
Flare Sysytem

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Some examples of hazardous , dangerous process
 Nitration reaction.(Strong oxidants and explosive
products)
 Fluorination reaction.(Highly reactive fluorine)
 Polymerization reaction.(Heat evolution and
viscosity rise with increase in degree of
polymerization.
 Pyrolysis reaction.(generation of hot spots)
 Halogenations reaction and combustion reaction
can be highly explosive.

13. 13
Process Design and Safety parameters
 To produce the desired products in safe manner.
 To design a process must operate safely at designed
condition.
 To make suitable provision to cope up with unsafe
deviation from design conditions.
 To ensure the safe start up and shut down procedure
establishment.

14. 14
Contd…..
 Safety and layout go hand in hand.
 The layout has
i)straight aisles for clear vision.
ii) Mirror should be fitted at blind corners.
iii)Moving elements should be painted in bright colors like
Overhead Cranes.
iv)Fast moving parts like V-belts and shaft coupling should
be well covered.
v) Pipes and other hot equipments should be installed 2-
2.5m above stairs and passage ways.

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